Industrial Waste
Management
-------
This Guide provides state-of-the-art tools and
practices to enable you to tailor hands-on
solutions to the industrial waste management
challenges you face.
WHAT'S AVAILABLE
• Quick reference to multimedia methods for handling and disposing of wastes
from all types of industries
• Answers to your technical questions about siting, design, monitoring, operation.
and closure of waste facilities
• Interactive, educational tools, including air and ground water risk assessment
models, fact sheets, and a facility siting tool.
• Best management practices, from risk assessment and public participation to
waste reduction, pollution prevention, and recycling
-------
;NOWLEDGEMENTS
The rdowing members of the Industrial Waste Focus Group and the Industrial Waste Steering Commiw are grateUy
acknowledged far al of their time and assistance in the development of this guidance document
Current Industrial Waste Focus
Group Members
Paul Bar*, The Dow Chemical
Company
Walter Carey. Nestle USA Inc and
New Miltord Farms
Rama Chaturvedi Bethlehem Steel
Corporation
H.C. Clark. Rice University
Barbara Dodds, League of Women
voters
Chuck Feerick. Exxon Mobil
Corporation
Stacey Ford. Exxon Mobil
Corporation
Robert Giraud OuPont Company
John Harney Citizens Round
Tabte/PURE
Kyle Isakower. American Petroleum
Institute
Richard Jarman, National Food
Processors Association
James Meiers, Cinergy Power
Generation Services
Scott Murto. General Motors and
American Foundry Society
James Roewer, Edison Electric
Institute
Edward Repa. Environmental
Industry Association
Tim Savior, International Paper
Amy Schaffer. Weyerhaeuser
Ed Skemofc, WMX Technologies. Inc
Michael Wach Western
Environmental Law Center
David Wens, University of South
Wabnms Medical Center
Pat Gwn Cherokee Nation of
Oklahoma
Past industrial Waste Focus
Group Members
Dora Cetofius. Sierra Club
Brian Forrestal. Laidlaw Waste
Systems
Jonathan Greenberg. Browning-
Ferris Industries
Michael Gregory, Arizona Toxics
Information and Sierra Club
Andrew Mites The Dexter
Corporation
Gary Robbins, Exxon Company
Kevin Sail. National Paint & Coatings
Association
Bruce SteJne. American Iron & Steel
Lisa Williams, Aluminum Association
Cuircnt Industrial Waste Steering
Committee Members
Keiiy Catalan Aaaocauon oi Slate
and Territorial Solid Waste
Management Officials
Marc Crooks, Washington State
Department ot Ecology
Cyndi Darling. Maine Department of
Environmental Protection
Jon DilDard Montana Department of
Environmental Qualty
Anne Dobbs. Texas Natural
Resources Conservation
Commission
Richard Hammond New York State
Department of Environmental
Conservation
Elizabeth Haven California State
Waste Resources Control Board
Jim Hul Missouri Department of
Natural Resources
Jim Knudson, Washington State
Department of Ecology
Chris McGuire, Florida Department
of Environmental Protection
Gene Mitchell Wisconsin
Department of Natural Resources
William Pounds, Pennsylvania
Department of Environmental
Protection
Bijan Sharafkhani Louisiana
Department of Environmental
Qualty
James Warner, Minnesota Pollution
Control Agency
ittustrial Waste Steering
Pamela um*. nianie
Environmental Protection
NormGumenik Arizona Department
of Environmental Qualty
Steve Jenkins, Alabama Department
of Environmental Management
Jim North Arizona Department of
Environmental Quality
-------
Industrial waste is generated by the production
of commercial goods, products, or services.
Examples include wastes from the production
of chemicals, iron and steel, and food goods.
-------
United States
Environmental Protection
Agency
Industrial Waste Air Model
Technical Background
Document
-------
Solid Waste and EPA 530-R-02-010
Emergency Response August 2002
(5306W) www.epa.gov/industrialwaste
-------
February 2002
Industrial Waste Air Model
Technical Background Document
Office of Solid Waste
U.S. Environmental Protection Agency
Washington, DC 20460
Printed on Recycled Paper
-------
-------
IWAIR Technical Background Document Table of Contents
Contents
Section Number
List of Figures v
List of Tables vi
List of Acronyms and Abbreviations vii
1.0 Introduction 1-1
1.1 Guide for Industrial Waste Management and IWAIR 1-1
1.2 Model Design 1-2
1.2.1 Emission Model 1-2
1.2.2 Dispersion Model 1-4
1.2.3 Risk Model 1-4
1.3 About This Document 1-5
2.0 Source Emission Estimates Using CHEMDAT8 2-1
2.1 Model Selection and Overview of CHEMDAT8 2-1
2.2 Scientific Background 2-3
2.3 Emission Model Input Parameters 2-5
2.3.1 Chemical-Specific Input Parameters 2-6
2.3.2 Input Parameters for Land Application Units, Landfills, and
Waste Piles 2-13
2.3.3 Input Parameters for Surface Impoundments 2-18
2.4 Mathematical Development of Emissions 2-24
2.4.1 Landfills 2-24
2.4.2 Land Application Units 2-29
2.4.3 Waste Piles 2-34
2.4.4 Surface Impoundments 2-36
3.0 Development of Dispersion Factors Using ISCST3 3-1
3.1 Development of Dispersion Factor Database 3-2
3.1.1 Identify WMU Areas and Heights for Dispersion Modeling (Step 1) .. 3-2
3.1.2 Select Receptor Locations for Dispersion Modeling (Step 2) 3-4
3.1.3 Identify Meteorological Stations for Dispersion Modeling (Step 3) ... 3-6
3.1.4 Conduct Dispersion Modeling Using Industrial Source Complex
Short-Term Model, Version 3 (Step 4) 3-10
3.1.5 Select Dispersion Factors to Populate IWAIR Database (Step 5) .... 3-13
3.2 Interpolation of Dispersion Factor 3-13
in
-------
IWAIR Technical Background Document Table of Contents
Contents (continued)
Section Number
4.0 Exposure Factors 4-1
4.1 Inhalation Rate 4-2
4.2 Body Weight 4-4
4.3 Exposure Duration 4-5
4.4 Exposure Frequency 4-6
5.0 Inhalation Health Benchmarks 5-1
5.1 Background 5-1
5.2 Data Sources 5-2
5.2.1 IRIS 5-3
5.2.2 Superfund Technical Support Center 5-3
5.2.3 HEAST 5-3
5.2.4 Other EPA Documents 5-4
5.2.5 ATSDR 5-4
5.2.6 CalEPA 5-4
5.3 Hierarchy Used 5-4
5.4 Chronic Inhalation Health Benchmarks Included in IWAIR 5-5
6.0 Calculation of Risk or Allowable Waste Concentration 6-1
6.1 Calculation of Risk or Hazard Quotient 6-1
6.1.1 Calculation of Risk for Carcinogens 6-2
6.1.2 Calculation of HQ for Noncarcinogens 6-3
6.2 Calculation of Allowable Waste Concentration 6-3
6.2.1 Calculating Allowable Waste Concentrations for Land Application
Units, Landfills, and Waste Piles 6-4
6.2.2 Calculating Allowable Waste Concentrations for Surface
Impoundments 6-5
6.2.3 Setting an Allowable Waste Concentration 6-7
7.0 References 7-1
Appendix A Considering Risks from Indirect Pathways A-l
Appendix B Physical-Chemical Properties for Chemicals Included in IWAIR B-l
Appendix C Sensitivity Analysis of ISCST3 Air Dispersion Model C-l
Appendix D Selection of Meteorological Stations D-l
IV
-------
IWAIR Technical Background Document Table of Contents
Figures
Number Page
3-1 Development of dispersion factor database 3-3
3-2 Meteorological stations and region boundaries for the contiguous 48 states 3-9
6-1 Graphical interpretation of the Newton-Raphson method 6-6
-------
IWAIR Technical Background Document Table of Contents
Tables
Number Page
1-1 Constituents Included in IWAIR 1-3
2-1 Chemical-Specific Inputs 2-7
2-2 Input Parameters for Landfills 2-14
2-3 Input Parameters for Land Application Units 2-15
2-4 Input Parameters for Waste Piles 2-16
2-5 Input Parameters for Surface Impoundments 2-19
3-1 Final Surface Areas and Heights Used for ISCST3 Model Runs 3-5
3-2 Surface-Level Meteorological Stations in IWAIR, by State 3-7
4-1 Summary of Exposure Factors Used in IWAIR 4-2
4-2 Recommended Inhalation Rates for Residents 4-3
4-3 Recommended Inhalation Rates for Workers 4-3
4-4 Body Weights for Adults, Males and Females Combined, by Age 4-4
4-5 Body Weights for Male and Female Children Combined, Aged 6 Months to 18 Years 4-5
5-1 Chronic Inhalation Health Benchmarks Used in IWAIR 5-6
5-2 Provisional Inhalation Benchmarks Developed in the Air Characteristic Study 5-11
VI
-------
IWAIR Technical Background Document
Table of Contents
Acronyms and Abbreviations
ADI Acceptable daily intake
ATSDR Agency for Toxic Substances and Disease Registry
CAA Clean Air Act
CAG Carcinogen Assessment Group
CalEPA California Environmental Protection Agency
CAS Chemical Abstract Service
CSF Cancer slope factor
CSTR Continuously stirred tank reactor
EFH Exposure Factors Handbook
EPA (U.S.) Environmental Protection Agency
FR Federal Register
HAD Health Assessment Documents
HEA Health Effects Assessment
HEAST Health Effects Assessment Summary Tables
HEED Health and Environmental Effects Document
KEEP Health Environmental Effects Profile
HQ Hazard quotient
HSDB Hazardous Substance Databank
IRIS Integrated Risk Information System
ISCST3 Industrial Source Complex, Short-Term Model, Version 3
ISMCS International Station Meteorological Climate Summary
IWAIR Industrial Waste Air Model
LOAEL Lowest-observed-adverse-effect level
MLVSS Mixed-liquor volatile suspended solids
MRL Minimum risk level
NCEA National Center for Environmental Assessment
NESHAP National Emission Standards for Hazardous Air Pollutants
NOAEL No-observed-adverse-effects level
OAQPS Office of Air Quality Planning and Standards
ORD Office of Research and Development
OSW Office of Solid Waste
OW Office of Water
RCRA Resource Conservation and Recovery Act
REL Reference exposure level
RfC Reference concentration
RfD Reference dose
SCDM Superfund Chemical Data Matrix
SAB Science Advisory Board
SIS Surface Impoundment Study
SSL Soil Screening Levels
TRI Toxics Release Inventory
TSDF Treatment Storage and Disposal Facility
TSS Total suspended solids
vn
-------
IWAIR Technical Background Document Table of Contents
Acronyms and Abbreviations (continued)
URF Unit risk factor
WHO World Health Organization
WMU Waste management unit
Vlll
-------
IWAIR Technical Background Document Section 1.0
1.0 Introduction
This document provides technical background information on the Industrial Waste Air
(IWAIR) model. This document is a companion document to the IWAIR User's Guide, which
provides detailed information on how to install and use the model.
1.1 Guide for Industrial Waste Management and IWAIR
The U.S. Environmental Protection Agency (EPA) and representatives from 12 state
environmental agencies developed a voluntary Guide for Industrial Waste Management
(hereafter, the Guide) to recommend a baseline of protective design and operating practices to
manage nonhazardous industrial waste throughout the country. The guidance is designed for
facility managers, regulatory agency staff, and the public, and it reflects four underlying
objectives:
• Adopt a multimedia approach to protect human health and the environment.
• Tailor management practices to risk in the enormously diverse universe of waste,
using the innovative, user-friendly modeling tools provided in the Guide.
• Reaffirm state and tribal leadership in ensuring protective industrial waste
management, and use the Guide to complement state and tribal programs.
• Foster partnerships among facility managers, the public, and regulatory agencies.
The Guide recommends best management practices and key factors to consider to protect
groundwater, surface water, and ambient air quality in siting, operating, and designing waste
management units (WMUs); monitoring WMUs' impact on the environment; determining
necessary corrective action; closing WMUs; and providing postclosure care. In particular, the
guidance recommends risk-based approaches to choosing liner systems and waste application
rates for groundwater protection and to evaluating the need for air controls. The CD-ROM
version of the Guide includes user-friendly air and groundwater models to conduct these risk
evaluations.
Chapter 5 of the Guide, entitled "Protecting Air Quality," highlights several key
recommendations:
• Adopt controls to minimize particulate emissions.
1-1
-------
IWAIR Technical Background Document Section 1.0
• Determine whether WMUs at a facility are addressed by Clean Air Act (CAA)
requirements and comply with those requirements.
• If WMUs are not specifically addressed by CAA requirements, use IWAIR to
assess risks associated with volatile air emissions from units.
• Implement pollution prevention programs, treatment measures, or emissions
controls to reduce volatile air emission risks.
EPA developed IWAIR and this technical background document to accompany the Guide
to assist facility managers and regulatory agency staff in evaluating inhalation risks. Workers
and residents in the vicinity of a unit may be exposed to volatile chemicals from the unit in the
air they breathe. Exposure to some of these chemicals at sufficient concentrations may cause a
variety of cancer and noncancer health effects (such as developmental effects in a fetus or
neurological effects in an adult). With a limited amount of site-specific information, IWAIR can
estimate whether specific wastes or waste management practices may pose an unacceptable risk
to human health.
1.2 Model Design
IWAIR is an interactive computer program with three main components: (1) an emission
model to estimate release of constituents from WMUs; (2) a dispersion model to estimate fate
and transport of constituents through the atmosphere and determine ambient air concentrations at
specified receptor locations; and (3) a risk model to calculate either the risk to exposed
individuals or waste constituent concentrations that can be protectively managed in the unit. The
program requires only a limited amount of site-specific information, including facility location,
WMU characteristics, waste characteristics, and receptor information. A brief description of
each component follows.
1.2.1 Emission Model
The emission model uses waste characterization, WMU, and facility information to
estimate emissions for 95 constituents (identified in Table 1-1) for four types of units: land
application units, landfills, waste piles, and surface impoundments. Users can add chemical
properties to model additional chemicals. The emission model selected for incorporation into
IWAIR is EPA's CHEMDAT8 model. This model has undergone extensive review by both EPA
and industry representatives and is publicly available from EPA's Web page
(http://www.epa.gov/ttn/chief/software.html).
To facilitate emission modeling with CHEMDAT8, IWAIR prompts the user to provide
the required waste- and unit-specific data. Once these data are entered, the model calculates and
displays chemical-specific emission rates. If users decide not to develop or use the CHEMDAT8
rates, they can enter their own site-specific emission rates.
1-2
-------
IWAIR Technical Background Document
Section 1.0
Table 1-1. Constituents Included in IWAIR
CAS
Number
Compound Name
CAS
Number
Compound Name
75070 Acetaldehyde
67641 Acetone
75058 Acetonitrile
107028 Acrolein
79061 Acrylamide
79107 Acrylic acid
107131 Acrylonitrile
107051 Allyl chloride
62533 Aniline
71432 Benzene
92875 Benzidine
50328 Benzo(a)pyrene
75274 Bromodichloromethane
106990 Butadiene, 1,3-
75150 Carbon disulfide
56235 Carbon tetrachloride
108907 Chlorobenzene
124481 Chlorodibromomethane
67663 Chloroform
95578 Chlorophenol, 2-
126998 Chloroprene
1319773 Cresols (total)
98828 Cumene
108930 Cyclohexanol
96128 Dibromo-3-chloropropane, 1,2-
75718 Dichlorodifluoromethane
107062 Dichloroethane, 1,2-
75354 Dichloroethylene, 1,1-
78875 Dichloropropane, 1,2 -
10061015 Dichloropropylene, cis-1,3-
10061026 Dichloropropylene, trans-1,3-
57976 Dimethylbenz[a]anthracene, 7,12-
95658 Dimethylphenol, 3,4-
121142 Dinitrotoluene, 2,4-
123911 Dioxane, 1,4-
122667 Diphenylhydrazine, 1,2-
106898 Epichlorohydrin
106887 Epoxybutane, 1,2-
111159 Ethoxyethanol acetate, 2-
110805 Ethoxyethanol, 2-
100414 Ethylbenzene
106934 Ethylene dibromide
107211 Ethylene glycol
75218 Ethylene oxide
50000 Formaldehyde
98011 Furfural
87683 Hexachloro-l,3-butadiene
118741 Hexachlorobenzene
77474 Hexachlorocyclopentadiene
67721 Hexachloroethane
78591 Isophorone
7439976 Mercury*
67561 Methanol
110496 Methoxyethanol acetate, 2-
109864 Methoxyethanol, 2-
74839 Methyl bromide
74873 Methyl chloride
78933 Methyl ethyl ketone
108101 Methyl isobutyl ketone
80626 Methyl methacrylate
1634044 Methyl tert-butyl ether
56495 Methylcholanthrene, 3-
75092 Methylene chloride
68122 N,N-Dimethyl formamide
91203 Naphthalene
110543 n-Hexane
98953 Nitrobenzene
79469 Nitropropane, 2-
55185 N-Nitrosodiethylamine
924163 N-Nitrosodi-n-butylamine
930552 N-Nitrosopyrrolidine
95501 o-Dichlorobenzene
95534 o-Toluidine
106467 p-Dichlorobenzene
108952 Phenol
85449 Phthalic anhydride
75569 Propylene oxide
110861 Pyridine
100425 Styrene
1746016 TCDD, 2,3,7,8 -
630206 Tetrachloroethane, 1,1,1,2-
79345 Tetrachloroethane, 1,1,2,2-
127184 Tetrachloroethylene
108883 Toluene
75252 Tribromomethane
76131 Trichloro-l,2,2-trifluoroethane, 1,1,2-
120821 Trichlorobenzene, 1,2,4-
71556 Trichloroethane, 1,1,1-
79005 Trichloroethane, 1,1,2-
79016 Trichloroethylene
75694 Trichlorofluoromethane
121448 Triethylamine
108054 Vinyl acetate
75014 Vinyl chloride
1330207 Xylenes
*Chemical properties for both elemental and divalent forms of mercury are included.
1-3
-------
IWAIR Technical Background Document Section 1.0
1.2.2 Dispersion Model
IWAIR's second modeling component estimates dispersion of volatilized constituents
and determines air concentrations at specified receptor locations using default dispersion factors
developed with EPA's Industrial Source Complex, Short-Term Model, version 3 (ISCST3).
ISCST3 was run to calculate dispersion for a standardized unit emission rate (1 |j,g/m2-s) to
obtain a dispersion factor, which is measured in |J,g/m3 per |j,g/m2-s. The total air concentration
estimates are then developed by IWAIR by multiplying the constituent-specific emission rates
derived from CHEMDAT8 (or the rates the user specified) with a site-specific dispersion factor.
Running ISCST3 to develop a new dispersion factor for each location/WMU is time consuming
and requires extensive meteorological data and technical expertise. Therefore, IWAIR
incorporates default dispersion factors developed using ISCST3 for many separate scenarios
designed to cover a broad range of unit characteristics, including
• 60 meteorological stations, chosen to represent the different climatic and
geographical regions of the contiguous 48 states, Hawaii, Puerto Rico, and parts
of Alaska;
• 4 unit types;
• 17 surface areas for landfills, land application units, and surface impoundments,
and 11 surface areas and 7 heights for waste piles;
• 6 receptor distances from the unit (25, 50, 75, 150, 500, 1,000 meters);
• 16 directions in relation to the edge of the unit (only the one resulting in the
maximum air concentration is used).
The default dispersion factors were derived by modeling each of these scenarios, then
choosing as the default the maximum dispersion factor of the 16 directions for each
WMU/surface area/height/meteorological station/receptor distance combination.
Based on the size and location of a unit specified by the user, IWAIR selects an
appropriate dispersion factor from the default dispersion factors in the model. If the user
specifies a unit surface area or height that falls between two of the sizes already modeled, IWAIR
uses an interpolation method to estimate a dispersion factor based on the two closest modeled
unit sizes.
Alternatively, a user may enter a site-specific dispersion factor developed by conducting
independent modeling with ISCST3 or with a different model and proceed to the next step, the
risk calculation.
1.2.3 Risk Model
The third component combines the constituent's air concentration with receptor exposure
factors and toxicity benchmarks to calculate either the risk from concentrations managed in the
1-4
-------
IWAIR Technical Background Document Section 1.0
unit or the waste concentration (Cwaste) in the unit that must not be exceeded to protect human
health. In calculating either estimate, the model applies default values for exposure factors,
including inhalation rate, body weight, exposure duration, and exposure frequency. These
default values are based on data presented in EPA's Exposure Factors Handbook (U.S. EPA,
1997a) and represent average exposure conditions. IWAIR contains standard health benchmarks
(cancer slope factors [CSFs] for carcinogens and reference concentrations [RfCs] for
noncarcinogens) for 94 of the 95 constituents included in IWAIR.1 These health benchmarks are
obtained primarily from the Integrated Risk Information System (IRIS) and the Health Effects
Assessment Summary Tables (HEAST) (U.S. EPA, 1997b, 2001a). IWAIR uses these data
either to estimate risk or hazard quotients (HQs) or to estimate allowable waste concentrations.
Users may override the IWAIR health benchmarks with their own values.
IWAIR only addresses risk from direct inhalation of vapor-phase emissions. Appendix A
discusses the potential for risks attributable to indirect exposures.
1.3 About This Document
The remainder of this background document is organized as follows:
• Section 2, Source Emission Estimates Using CHEMDAT8, describes the
CHEMDAT8 model used to calculate emissions.
• Section 3, Development of Dispersion Factors Using ISCST3, describes how
dispersion factors were developed using ISCST3 and how these are used in the
model.
• Section 4, Exposure Factors, describes the exposure factors used in the model.
• Section 5, Inhalation Health Benchmarks, describes the health benchmarks used
in the model.
• Section 6, Calculation of Risk or Allowable Waste Concentration, describes the
risk calculation and the allowable waste calculation.
• Section 7, References, lists all references cited in this document.
• Appendix A, Considering Risks from Indirect Pathways, describes the types of
pathways by which an individual may be exposed to a constituent, explains which
pathways are accounted for in IWAIR, and discusses exposures unaccounted for
in IWAIR.
1 At the time IWAIR was released, no accepted health benchmark was available for 3,4-dimethylphenol
from the hierarchy of sources used to populate the IWAIR health benchmark database, nor were data available from
these sources to allow the development of a health benchmark with any confidence. In addition, IWAIR contains
chemical properties for both elemental and divalent forms of mercury, but contains a health benchmark only for
elemental mercury; no accepted benchmark was available for divalent mercury.
-------
IWAIR Technical Background Document Section 1.0
• Appendix B, Physical-Chemical Properties for Chemicals Included in IWAIR,
presents the physical-chemical property values included in IWAIR and the sources
of those values.
• Appendix C, Sensitivity Analysis of the ISCST3 Air Dispersion Model, describes
the sensitivity analysis performed on depletion options, source shape and
orientation, and receptor location and spacing.
• Appendix D, Selection of Meteorological Stations, discusses the approach used
for selecting meteorological stations used in IWAIR and describes the region
represented by each station.
1-6
-------
IWAIR Technical Background Document Section 2.0
2.0 Source Emission Estimates Using
CHEMDAT8
This section describes the CHEMDAT8 emission model used to develop emission
estimates for each WMU. Section 2.1 describes why CHEMDAT8 was chosen and provides an
overview of CHEMDAT8; Section 2.2 provides scientific background on emissions modeling for
aqueous- versus organic-phase wastes; Section 2.3 describes the input parameters; and
Section 2.4 describes the important modeling assumptions and equations used to calculate mass
emission rates.
2.1 Model Selection and Overview of CHEMDAT8
EPA's CHEMDAT8 model was selected as the model to estimate volatile emission rates
from the WMUs in IWAIR. CHEMDAT8 meets the goals that were established during the
model selection process. EPA sought to select a model that
• Provides emission estimates that are as accurate as possible without
underestimating the constituent emissions
• Provides a relatively consistent modeling approach (in terms of model complexity
and conservatism) for each of the different emission sources under consideration
• Has undergone extensive peer review and is widely accepted by both EPA and
industry
• Is publicly available for use in more site-specific evaluations.
The CHEMDAT8 model was originally developed in projects funded by EPA's Office of
Research and Development (ORD) and Office of Air Quality Planning and Standards (OAQPS)
to support National Emission Standards for Hazardous Air Pollutants (NESHAPs) from sources
such as tanks, surface impoundments, landfills, waste piles, and land application units for a
variety of industry categories, including chemical manufacturers, pulp and paper manufacturing,
and petroleum refining. CHEMDAT8 includes analytical models for estimating volatile
compound emissions from treatment, storage, and disposal facility processes under user-specified
input parameters and has been used to support the emissions standards for hazardous waste
treatment, storage, and disposal facilities (U.S. EPA, 1991) regulated under Subpart CC rules of
the Resource Conservation and Recovery Act (RCRA), as amended in 1984. The CHEMDAT8
model is publicly available and has undergone extensive review by both EPA and industry
representatives.
-------
IWAIR Technical Background Document
Section 2.0
Competing Removal Pathways
Adsorption is the tendency of a chemical or liquid
medium to attach or bind to the surface of particles in
the waste.
Biodegradation is the tendency of a chemical to be
broken down or decomposed into less-complex
chemicals by organisms in the waste or soil.
Hydrolysis is the tendency of a chemical to be
broken down or decomposed into less-complex
chemicals by reaction with water in the waste or soil.
Leaching is the tendency of a chemical to dissolve in
water in the waste or soil and follow the flow of
water (e.g., due to rainfall) down through the soil to
groundwater.
Runoff is the tendency of a chemical to dissolve in
water in the waste or soil and follow the flow of
water (e.g., due to rainfall) downhill to surface water.
CHEMDAT8 models volatile air
emissions and considers most of the
significant competing removal pathways that
might limit those emissions (see text box).
These competing removal pathways lower the
potential for emission to the air as gases in
various ways: adsorption limits the mass of
chemical free to volatilize by binding
chemical on the waste particles;
biodegradation and hydrolysis reduce the
mass of the chemical in the unit (although
these mechanisms do generate new chemicals
in the form of breakdown products); and
leaching and runoff remove chemical mass
from the unit by non-air pathways (i.e., to
groundwater or surface water).
For surface impoundments,
CHEMDAT8 considers adsorption,
biodegradation, and hydrolysis. For land
application units, landfills, and waste piles,
CHEMDAT8 considers biodegradation; CHEMDAT8 does not explicitly consider adsorption for
these unit types, but volatilization from these unit types is limited by the relative air porosity of
the soil or waste matrix. CHEMDAT8 does not consider hydrolysis in the land application unit,
landfill, and waste pile, even for soil moisture or percolating rainwater. CHEMDAT8 does not
consider leaching or runoff for any of the unit types, nor does it model chemical breakdown
products from biodegradation or hydrolysis. As such, CHEMDAT8 is considered to provide
reasonable to slightly high (environmentally conservative) estimates of air emissions from the
various emission sources modeled in IWAIR.
EPA's CHEMDAT8 model is a modular component of IWAIR. The original
CHEMDAT8 Lotus 1-2-3 spreadsheet was converted to Visual Basic code for use in IWAIR. In
addition, the chemical-specific data in the original code were evaluated for accuracy. Some of
these values have been changed to reflect newer or better information. A list of the physical-
chemical property values included in IWAIR is provided in Appendix B of this document.
Extensive testing was performed to ensure that the coded version produces results identical to the
spreadsheet version.
This document provides information about CHEMDAT8 that is pertinent to the IWAIR
program, including the CHEMDAT8 equations used in IWAIR. However, it does not attempt to
reproduce the CHEMDAT8 documentation, so the equations are presented, but their derivation is
not covered in any detail. For complete documentation on the CHEMDAT8 model, refer to
documents available on EPA's Web page. The CHEMDAT8 spreadsheet model and model
documentation may be downloaded at no charge from EPA's Web page
(http://www.epa.gov/ttn/chief/software.html).
2-2
-------
IWAIR Technical Background Document Section 2.0
2.2 Scientific Background
A WMU contains solids, liquids (such as water), and air. Individual chemical molecules
are constantly moving from one of these media to another: they may be adsorbed to solids,
dissolved in liquids, or assume vapor form in air. At equilibrium, the movement into and out of
each medium is equal, so that the concentration of the chemical in each medium is constant. The
emissions model used in IWAIR, CHEMDAT8, assumes that equilibrium has been reached.
Partitioning refers to how a chemical tends to distribute itself among these different
media. Different chemicals have differing affinities for particular phases—some chemicals tend
to partition preferentially to air, while others tend to partition preferentially to water. The
different tendencies of different chemicals are described by partition coefficients or equilibrium
constants.
Of particular interest in modeling volatile emissions of a chemical from a liquid waste
matrix is the chemical's tendency to change from a liquid form to a vapor form. As a general
rule, a chemical's vapor pressure describes this tendency. The pure-component vapor pressure is
a measure of this tendency for the pure chemical. A chemical in solution in another liquid (such
as a waste containing multiple chemicals) will exhibit a partial vapor pressure, which is the
chemical's share of the overall vapor pressure of the mixture; this partial vapor pressure is lower
than the pure-component vapor pressure and is generally equal to the pure-component vapor
pressure times the constituent's mole fraction (a measure of concentration reflecting the number
of molecules of the chemical per unit of volume) in the solution. This general rule is known as
Raoult's law.
Most chemicals do not obey Raoult's law in dilute (i.e., low concentration) aqueous
solutions, but exhibit a greater tendency to partition to the vapor phase from dilute solutions than
would be predicted by Raoult's law. These chemicals exhibit a higher partial vapor pressure than
the direct mole fraction described above would predict.1 This altered tendency to partition to the
vapor phase in dilute solutions is referred to as Henry's law. To calculate the emissions of a
constituent from a dilute solution, a partition coefficient called Henry's law constant is used.
Henry's law constant relates the partial vapor pressure to the concentration in the solution.
To account for these differences in the tendency of chemicals to partition to vapor phase
from different types of liquid waste matrices, CHEMDAT8 models emissions in two regimes: a
dilute aqueous phase, modeled using Henry's law constant as the partition coefficient, and an
organic phase, modeled using the partial vapor pressure predicted by Raoult's law as the partition
coefficient. In fact, there is not a clear point at which wastes shift from dilute aqueous phase to
organic phase; this is a model simplification. However, several rules of thumb are used to
determine when the Raoult's law model would be more appropriate. The clearest rule is that any
chemical present in excess of its solubility limit in a wastewater or its saturation concentration in
soil has exceeded the bounds of "dilute aqueous" and is more appropriately modeled using
1 There are some exceptions to this behavior in dilute solutions. A notable exception is formaldehyde,
which has lower activity in dilute aqueous solution, which means that formaldehyde will have greater emissions in a
high-concentration organic-phase waste.
-------
IWAIR Technical Background Document
Section 2.0
Aqueous-phase waste: a waste that is predominantly
water, with low concentrations of organics. All
chemicals remain in solution in the waste and are
usually present at concentrations below typical
solubility or saturation limits. However, it is possible
for the specific components of the waste to raise the
effective solubility or saturation level for a chemical,
allowing it to remain in solution at concentrations
above the typical solubility or saturation limit.
Organic-phase waste: a waste that is predominantly
organic chemicals, with a high concentration of
organics. Concentrations of some chemicals may
exceed solubility or saturation limits, causing those
chemicals to come out of solution and form areas of
free product in the WMU. In surface impoundments,
this can result in a thin organic film over the entire
surface.
Raoult's law. Chemicals exceeding solubility
or saturation limits will typically come out of
solution and behave more like pure, organic-
phase component. However, solubility and
saturation limits can vary depending on site-
specific parameters, such as temperature and
pH of the waste. In addition, waste matrix
effects2 can cause chemicals to remain in
solution at concentrations above their typical
solubility or saturation limit. This scenario
(an aqueous-phase waste with concentrations
above typical solubility or saturation limits) is
also best modeled using Raoult's law.
Another rule of thumb is that a waste with a
total organics concentration in excess of
about 10 percent (or 100,000 ppm) is likely to
behave more like an organic-phase waste than
a dilute aqueous-phase waste and be more
appropriately modeled using Raoult's law.
For land application units, landfills, and waste piles, where the waste is either a solid or
mixed with a solid (such as soil), the CHEMDAT8 emissions model considers two-phase
partitioning of the waste into the liquid (either aqueous or organic) phase and the air phase, using
the partition coefficients described above, to estimate the equilibrium vapor composition in the
pore (or air) space within the WMU. Emissions are subsequently estimated from the WMU by
calculating the rate of diffusion of the vapor-phase constituent through the porous waste/soil
medium.
For surface impoundments, where the waste is a liquid, the model uses a different
approach that considers the resistance to mass transfer (i.e., movement of chemical mass from
one phase to the other) in the liquid and gas phases at the surface of the impoundment.
Emissions are calculated using an overall mass transfer coefficient, which is based on the
partition coefficient (as described above), the liquid-phase mass transfer factor (which accounts
for resistence to transfer in the liquid phase), and the gas-phase mass transfer factor (which
accounts for resistence to transfer in the gas phase). This is referred to as the two-film model.
For organic-phase wastes, the mass transfer is dominated by the gas-phase resistance and the
partition coefficient; the liquid-phase mass transfer resistance is negligible and is, therefore,
omitted from the calculation. This is referred to as the one-film model, or the oily film model.
"Waste matrix effects" refers to the effect that the composition of the waste has on a constituent's
solubility in the waste or the tendency for the chemical to evaporate from the waste. For example, hexane has a
solubility in distilled water of approximately 12 mg/L; however, its solubility in methanol is much higher (more than
100,000 mg/L) (Perry and Green, 1984). Therefore, it is likely that hexane will remain dissolved in a solution of 10
percent methanol in water at higher concentrations than the aqueous solubility limit of 12 mg/L suggests.
2-4
-------
IWAIR Technical Background Document Section 2.0
In the two-film model for surface impoundments, the gas-phase and liquid mass transfer
coefficients are strongly affected by the turbulence of the surface impoundment's surface.
Turbulence may be caused by mechanical aeration or, to a lesser extent, diffused air aeration.
Therefore, whether the impoundment is aerated or not and how it is aerated are important inputs.
2.3 Emission Model Input Parameters
To model emissions using CHEMDAT8, users enter unit-specific data. Most of the
inputs are used by CHEMDAT8 directly, but some are used to calculate other inputs for
CHEMDAT8. The IWAIR program provides default input data for some parameters. For
example, the annual average temperature and wind speed for a WMU site are automatically used
as a default for a site once the site is assigned to one of the 60 meteorological stations in the
IWAIR program. Users may choose to override the default data and enter their own estimates for
these parameters. Thus, emissions can be modeled using CHEMDAT8 with a very limited
amount of site-specific information by using the default data provided.
This section discusses the various parameters that have a significant impact on the
estimated emission rates. Inputs that influence these rates include
• Input parameters specific to the physical and chemical properties of the
constituent being modeled
• The characteristics of the waste material being managed
• Input parameters specific to the process and operating conditions of the WMU
being modeled
• Meteorological parameters.
IWAIR checks inputs only against the limits of the model or absolute physical limits (e.g., area
must be greater than zero). It does not verify that user-provided inputs are within some "typical"
or "acceptable" range. However, Appendix B of the IWAIR User's Guide provides guidance for
developing values for all input parameters.
A general discussion of the physical and chemical properties of the constituents is
provided in the Section 2.3.1. Critical input parameters for the remaining sets of inputs are
discussed for land application units, landfills, and waste piles in Section 2.3.2 and for surface
impoundments in Section 2.3.3. The input parameters used in IWAIR differ in some respects
from those needed by CHEMDAT8. When the CHEMDAT8 inputs are not readily available but
can be calculated from more readily available data, IWAIR uses the more readily available input
parameters. The equations used to convert these to the CHEMDAT8 inputs are documented in
Section 2.4. For detailed guidance on developing input values for all parameters needed to run
IWAIR, see Appendix B, "Parameter Guidance," of the IWAIR User's Guide.
2-5
-------
IWAIR Technical Background Document
Section 2.0
Organic Chemicals
The IWAIR model covers only organic chemicals,
with the exception of mercury. Organic chemicals
are those pertaining to or derived from living
organisms. All organic chemicals contain carbon and
most also contain hydrogen, although there are some
substituted carbon compounds that do not contain
hydrogen but are generally considered to be organics
(e.g., carbon tetrachloride). However, elemental
carbon and certain other carbon-containing
compounds (e.g., carbon dioxide) are considered
inorganic compounds.
2.3.1 Chemical-Specific Input Parameters
Chemical-specific input parameters
are those parameters that relate to the physical
or chemical properties of each individual
chemical. The values of these parameters are
different for each of the 95 chemicals
included in IWAIR. Table 2-1 lists the
chemical-specific input parameters needed to
run IWAIR, along with minimum and
maximum values, if any (a blank in the
maximum column indicates that no maximum
value is enforced). IWAIR comes with
chemical data for 95 chemicals in its chemical
properties database. Using the ADD/MODIFY
CHEMICALS feature, the user can create additional
entries in the chemical properties database to reflect different property values for organic
chemicals included in IWAIR or to add new organic chemicals not included in IWAIR. To
maintain the integrity of the original chemical data included with IWAIR, those entries cannot be
edited directly; however, they may be used as the basis for new entries. Mercury is included in
the IWAIR database in both divalent and elemental forms, but because of code modifications
needed for mercury (to reflect differences in its behavior, since it is not an organic chemical), the
user may not create additional or modified entries for mercury.
Key chemical-specific input parameters that have a significant impact on modeled
emissions include air-liquid equilibrium partition coefficients (vapor pressure or Henry's law
constant), liquid-solid equilibrium partition coefficients (log octanol-water partition coefficient
for organics), biodegradation rate constants, and liquid and air diffusivities.
The primary data sources for the physical and chemical properties for the constituents
included in IWAIR include
• EPA's Superfund Chemical Data Matrix (SCDM) (U. S. EPA, 1997d),
• The Merck Index (Budavari, 1996),
• The National Library of Medicine's Hazardous Substances Databank (HSDB),
available on TOXNET (U.S. NLM, 2001),
• Syracuse Research Corporation's CHEMFATE database (SRC, 1999)
• CambridgeSoft.com's ChemFinder database (CambridgeSoft, 2001),
• EPA's Mercury Report to Congress (U.S. EPA, 1997c), and
• EPA's Diaxin Reassessment (U.S. EPA, 2000).
2-6
-------
IWAIR Technical Background Document
Section 2.0
Table 2-1. Chemical-Specific Inputs
Parameter
Chemical name
CAS number
Molecular weight (g/mol)
Density (g/cm3)
Vapor pressure (mm Hg)
Henry's law constant
(atm - mVmol)
Solubility (mg/L)
Diffusivity in water (cm2/s)
Diffusivity in air (cm2/s)
Log Kow
K! (L/g-h)
Kmax(mgVO/g-h)
Soil biodegradation rate (s"1)
Hydrolysis constant (s"1)
Antoine's constant A
Antoine's constant B
Antoine's constant C
Soil saturation concentration (mg/kg)
Minimum
Value
1
>0
>0
>0
>0
>0
0
-10
0
0
0
0
0
0
None
>0
Maximum
Value3
1,000,000
10
Comments
Cannot be left blank; maximum
length is 60 characters
Cannot be left blank; must be
numeric; maximum length is 9
numbers
User-entered values of zero are
changed to IE- 6 to prevent
division by zero in IWAIR.
User-entered values of zero are
changed to 1E-4 to prevent
division by zero in IWAIR.
User-entered values of zero are
changed to 1E-20 to prevent
division by zero in IWAIR.
Calculated by IWAIR
' A blank cell indicates there is no maximum value.
2-7
-------
IWAIR Technical Background Document Section 2.0
These sources were used for molecular weight, density, vapor pressure, Henry's law constant,
solubility, and log octanol-water partition coefficient. Liquid and air diffusivities were calculated
from other properties. Antoine's coefficients (for adjusting vapor pressure to temperature) were
taken from Reid et al. (1977). Soil biodegradation rate constants were taken from Howard et al.
(1991). Hydrolysis rate constants were taken from Kollig (1993). Biodegradation rates for
surface impoundments (K, andKmax) were taken from CHEMDATS's chemical properties
database (U.S. EPA, 1994a). The surface impoundment biodegradation rate constants in the
downloaded CHEMDAT8 database file were compared with the values reported in the summary
report that provided the basis for the CHEMDAT8 surface impoundment biodegradation rate
values (Coburn et al., 1988). Surface impoundment biodegradation rate constants for compounds
with no data were assigned biodegradation rates equal to the most similar compound in the
biodegradation rate database. The specific chemical property inputs used for the emission
modeling are provided in Appendix B with their chemical- and property-specific references. The
following subsections briefly describe each chemical property.
Molecular Weight (g/mol). Molecular weight is used to estimate emissions. This value
must be greater than or equal to 1 g/mol (the molecular weight of a single hydrogen ion).
Density (g/m3). IWAIR uses density to determine if chemicals present in organic phase in
surface impoundments are likely to float (if they are less dense than water) or sink (if they are
more dense than water). Unless the value is very near 1 g/m3 (the density of water), the model is
not sensitive to variations in the value.
Vapor Pressure (mmHg). Vapor pressure and the mole fraction concentration in the
liquid phase are used to calculate the constituent's partial vapor pressure. The partial vapor
pressure is subsequently used as the partition coefficient for organic-phase wastes and aqueous-
phase wastes with chemicals present above solubility or saturation limits. Different vapor
pressures may be reported for the same chemical at different temperatures. The vapor pressures
in RVAIR were chosen for temperatures as close to 25°C as possible. IWAIR corrects these to
the ambient temperature (see Sections 2.4.1 and 2.4.4.1 for specific equations, and Sections 2.3.2
and 2.3.3 for a more general discussion of temperature corrections).
Henry's Law Constant (atm-n^/mol). Henry's law constant reflects the tendency of
chemicals to volatilize from dilute aqueous solutions; it is used as the partition coefficient for
aqueous-phase wastes with chemicals present below solubility or saturation limits. Values can be
obtained from the literature, or they can be calculated from the chemical's vapor pressure,
molecular weight, and solubility using the following equation (Lyman et al., 1990):
f VP
760 (2-1)
2-8
-------
IWAIR Technical Background Document Section 2. 0
where
H = Henry 'slaw constant (atm-m3/mol)
VP = vapor pressure (mmHg)
S = solubility (mg/L)
MW = molecular weight (g/mol)
760 = unit conversion (mmHg/atm)
1000 = unit conversion (L/m3)
1000 = unit conversion (mg/g).
IWAIR corrects Henry's law constant to the ambient temperature (see Sections 2.4. 1 and 2.4.4. 1
for specific equations, and Sections 2.3.2 and 2.3.3 for a more general discussion of temperature
corrections).
Solubility (mg/L). This is the solubility of the individual chemical in water. Solubility is
used for surface impoundments to identify wastes that may be supersaturated so that emissions
equations may be based on the most appropriate partition coefficient (Henry's law for aqueous-
phase wastes below saturation or solubility limits, and partial vapor pressure for wastes above
saturation or solubility limits and organic-phase wastes).
Soil Biodegradation Rate (s'1). The soil biodegradation rate is a first-order rate constant
used to estimate soil biodegradation losses in land application units, landfills, and waste piles.
The tendency to biodegrade in soil is often reported as half-life. Half-life is not comparable to
biodegradation rate; however, the soil biodegradation rate can be calculated from the half-life as
follows:
ks = -p (2-2)
Ll/2
where
ks = soil biodegradation rate (s"1)
ln(2) = natural log of 2
t1/2 = half-life (s).
For IWAIR, the longest half-life (i.e., slowest degradation) was chosen when a range of
values was reported. Observed biodegradation rates are dependent on the population of specific
degrading species, microorganism acclimation, and primary versus secondary substrate
utilization. In addition, there is the potential for co-metabolism and inhibition. Consequently,
observed biodegradation rates for similar treatment units within the same (or similar) industry are
highly variable. Order-of-magnitude variations in observed degradation rates are not unusual.
This makes the development of generally applicable biodegradation rate constants a difficult task
and ensures a significant level of uncertainty. As a result, users are encouraged to create new
chemical entries in the IWAIR database and enter site-specific biodegradation rates if these are
available.
2-9
-------
IWAIR Technical Background Document Section 2.0
Antoine's Constants: A, B, or C. Antoine's constants are used to adjust vapor pressure
and Henry's law constant to ambient temperature.
Diffusivity in Water (cnf/s). Diffusivity in water is used to estimate emissions.
Diffusivity in water can be calculated from the chemical's molecular weight and density, using
the following correlation equation based on Water9 (U.S. EPA, 2001b):
D-=00001518xh^rH^ (M)
where
Dw = diffusivity in water (cm2/s)
T = temperature (°C)
273.16 = unit conversion (°C to °K)
MW = molecular weight (g/mol)
p = density of chemical (g/cm3).
If density is not available, diffusivity in water can be calculated using the following correlation
equation based on U.S. EPA (1987b):
2
Dw = 0.00022 x (MW) 3 (2-4)
Diffusivity in Air (cnf/s). Diffusivity in air is used to estimate emissions. Diffusivity in
air can be calculated from the chemical's molecular weight and density, using the following
correlation equation based on Water9 (U.S. EPA, 2001b):
0.00229 X (T + 273.16) L5 X 10.034 + X MWcor
V V MW/
MW
V0.33
+ 1.8
(2-5)
where
Da = diffusivity in air (cm2/s)
T = temperature (°C)
273.16 = unit conversion (°C to °K)
MW = molecular weight (g/mol)
p = density (g/cm3)
MWcor = molecular weight correlation:
2-10
-------
IWAIR Technical Background Document Section 2.0
MWcor = (l - 0.000015 x MW2 ) (2-6)
If MWcor is less than 0.4, then MWcor is set to 0.4.
If density is not available, diffusivity is air can be calculated using the following correlation
equation based on U.S. EPA (1987b):
--
D = 1.9 X MW 3 (2-7)
d I I \ /
For dioxins, diffusivity in air is calculated from the molecular weight using the following
equation based on EPA's Dioxin Reassessment (U.S. EPA, 2000):
154
Octanol-Water Partition Coefficient (log Kon). Km is used to estimate emissions and to
calculate the soil saturation concentration limit for land application units, landfills, and waste
piles. Because K^ can cover an extremely wide range of values, it is typically reported as the log
of Km. Mercury does not have a Km because it is not an organic chemical. The soil-water
partition coefficent (Kd) for mercury is used instead.
Hydrolysis Constant (s'1). This value, which is used to estimate losses by hydrolysis, is
the hydrolysis rate constant at neutral pH. Very few data were available on hydrolysis rates for
IWAIR chemicals; therefore, only a few chemicals have them in the IWAIR database.
Kj (L/g-h) andKmax (mg volatile organics/g-h). K, and Kmax are used to estimate
biodegradation losses in surface impoundments. IWAIR uses the CHEMDAT8 model equations
for biodegradation in wastewater treatment units. These biodegradation rate equations are based
on the Monod model for biodegradation (analogous to Michaelis-Menten enzyme kinetics). This
biodegradation rate model is linear (first order) with constituent concentrations at low
concentrations and becomes independent (zero order) at higher concentrations. Unfortunately,
because of the difficulty in determining the two biodegradation rate constants (K, and Kmax)
needed for the Monod model, many detailed wastewater treatment source models resort to simple
first-order biodegradation rate kinetics. Although inhibitory kinetics are not included in the
model, by using the Monod biodegradation rate model, IWAIR provides a much better
simulation of the reduced relative importance of biodegradation at high constituent
concentrations than it would if it employed strictly first-order biodegradation kinetics. To
include inhibitory kinetics requires a third rate constant, which is available for far fewer
compounds than those used as the basis for the Monod constants.
2-11
-------
IWAIR Technical Background Document Section 2. 0
The data sources for the biodegradation rate constants developed for the CHEMDAT8
model and used in IWAIR are fully documented in Coburn et al. (1988); a representative
(although incomplete) list of the data sources includes EPA sampling at 10 different activated
sludge systems and three surface impoundment units at varied industries; other full-scale
sampling studies of activated sludge systems (Berglund and Whipple, 1987; Hannah et al., 1986)
and surface impoundments (Demirjian et al., 1983); pilot-scale treatment studies (Petrasek, 1981;
Petrasek et al., 1983; and Lesiecki et al., 1987); biodegradability flask studies (Fitter, 1976); and
laboratory studies (Kincannon et al., 1982; Beltrame et al., 1980, 1982; and Beltrame, Beltrame,
and Carniti, 1982). Although the biodegradation rate constants for the CHEMDAT8 model were
developed in 1988, few additional data have been presented since to significantly alter these rate
constants.
Biodegradation rate constants were not available for all of the IWAIR compounds.
Biodegradation rate constants for compounds that did not have sufficient data were assigned the
biodegradation rate constant of the most similar compound (in terms of chemical structure and
biologically important functional groups) for which biodegradation rate constants could be
estimated. There is some additional uncertainty for these biodegradation rate constants, but
similarly structured chemicals typically have similar biodegradation rates, and the added
uncertainty in the biodegradation rate constant assignments is likely not much greater than the
uncertainty in the biodegradation rate constants themselves.
Soil Saturation Concentration (mg/kg). The soil saturation limit (Csal) reflects the
maximum concentration of a chemical that can be present in a soil matrix. Csat is dependent on
site-specific factors, as well as chemical properties; therefore, IWAIR calculates it from user
inputs as follows:
sat= dxPb+ ew+ xea (2.9)
•"D
where
Csat = soil saturation limit (mg/kg)
S = solubility (mg/L)
pb = bulk density of soil/waste matrix (kg/L)
Kd = soil-water partition coefficient (L/kg), calculated as shown below for organic
chemicals; this is an input for mercury
ew = water-filled porosity (unitless)
H' = dimensionless Henry's law constant (unitless = H/RT)
ea = air-filled porosity (unitless)
and
Kd = Koc X foc (2-10)
2-12
-------
IWAIR Technical Background Document Section 2.0
where
Koc = organic carbon partition coefficient (L/kg), calculated as shown below
foc = fraction organic carbon in waste (unitless).
Fraction organic carbon is set to a fixed value of 0.014. This value was derived from the median
of a set of values for many (but not all) of the locations included in the IWAIR dispersion factor
database. Koc is calculated as follows (Hasset et al., 1980):
Koc = 10--- (2-11)
where
Kow = octanol-water partition coefficent (L/kg).
2.3.2 Input Parameters for Land Application Units, Landfills, and Waste Piles
The input parameters for land-based units are presented in Tables 2-2 through 2-4.
Unit Design and Operating Parameters. The annual waste quantity, the frequency of
constituent addition, and the dimensions of the unit influence a number of model input
parameters. Because these are so critical and because the values of these parameters for a
specific unit to be modeled should be readily available to the user, no default values are provided
for these parameters. Operating life is also included here, although it does not affect emissions
for waste piles. This value is used to cap the default exposure durations used by IWAIR for
landfills and waste piles (30 years for residents and 7.2 years for workers) if the unit is not going
to be operating that much longer, as closure of these unit types is assumed to end exposure.
Postclosure exposure is assumed to occur for land application units; therefore, exposure duration
is not capped at operating life.
Also in this category is the biodegradation toggle. This option lets the user choose
whether to model biodegradation losses in the unit. This is set on by default for land application
units, which are designed to biodegrade wastes, and off for landfills and waste piles, which often
are not.
Waste Characterization. In order to generate an accurate estimate of a constituent's
volatile emissions, a user of IWAIR must define the physical and chemical characteristics of the
waste that will be managed in the WMU. In particular, the user must identify whether or not the
waste is best described as a dilute mixture of chemical compounds (aqueous) or if the waste
should be considered organic, containing high levels of organic compounds or a separate
nonaqueous organic phase. These two different types of waste matrices influence the degree of
partitioning that will occur from the waste to the air. Partitioning describes the affinity that a
constituent has for one phase (for example, air) relative to another phase (for example, water)
that drives the volatilization of organic chemicals. The choice of waste matrix will significantly
affect the rate of emissions from the waste. See Section 2.2 for a more detailed discussion of
2-13
-------
IWAIR Technical Background Document
Section 2.0
Table 2-2. Input Parameters for Landfills
Input Parameter
Units
Default
Value
Range3
Basis
Unit Design and Operating Parameters
Biodegradation toggle
Operating life of landfill
Total area of landfill - all cells
Average depth of landfill cell
Total number of cells in landfill
Average annual quantity of waste
disposed
none
yr
m2
m
unitless
Mg/yr
off
none
none
none
none
none
>0
81-
8.09E+6
>0
>1
>0
Required input
Required input
Required input
Required input
Required input
Waste Characterization Information
Dry bulk density of waste in landfill
Average molecular weight of organic-
phase waste
Total porosity of waste
Air-filled porosity of waste
g/cm3
g/mol
volume
fraction
volume
fraction
1.2
none
0.50
0.25
>0
>1
>0-<1
XMotal
porosity
ERG and Abt (1992)— uses a default
of 1.4 g/cm3 for waste sludge
U.S. EPA (1989)— uses sludge density
of 1.01 g/cm3
Required input for organic phase
wastes
U.S. EPA (1991)— input used for all
active landfills
Coburn et al. (1988)— default input for
CHEMDAT8 landfill
ERG and Abt (1992)— uses default of
0.40
Schroeder et al. (1994) — halogenated
aliphatics used 0.46
U.S. EPA (1991)— input used for all
active landfills
Coburn et al. ( 1 988)— default input
for CHEMDAT8 landfill
Schroeder et al. (1994) — halogenated
aliphatics used range = 0.16 to 0.31
' Ranges are inclusive, except for parameters with ranges shown as ">0-x", which must be greater than zero.
2-14
-------
IWAIR Technical Background Document
Section 2.0
Table 2-3. Input Parameters for Land Application Units
Input Parameter
Units
Default
Value
Range3
Basis
Unit Design and Operating Parameters
Biodegradation toggle
Operating life of land application
unit
Tilling depth of land application unit
Surface area of land application unit
Average annual quantity of waste
applied
Number of applications per year
none
yr
m
m2
Mg/yr
yr1
on
none
none
none
none
none
>0
>0
81-
8.09E+6
>0
>1
Required input
Required input
Required input
Required input
Required input
Waste Characterization Information
Dry bulk density of waste/soil
mixture
Average molecular weight of
organic -phase waste
Total porosity of waste/soil mixture
Air-filled porosity of waste/soil
g/cm3
g/mol
volume
fraction
volume
fraction
1.3
none
0.61
0.5
>0
>1
>0-<1
>0-total
porosity
Loehr et al. (1993) — reports density
= 1.39 g/cm3 for surface soil
U.S. EPA (1992)— uses a default
value of 1.4 g/cm3 for sewage
sludge/soil in land application unit
Li and Voudrias (1994) — wet soil
column density = 1.03 g/cm3
Required input for organic-phase
wastes
U.S. EPA (1991)— default input used
for all model land application
units
Coburn et al. ( 1 988)— default input
for CHEMDAT8 land application
units
U.S. EPA (1992)— uses default of
0.4
Loehr et al. (1993) — reports porosity
= 0.49 for surface soil
Li and Voudrias (1994) — wet soil
column porosity = 0.558
U.S. EPA (1991)— default input used
for all model land application
units
Coburn et al. (1988)— default input
for CHEMDAT8 land application
units
' Ranges are inclusive, except for parameters with ranges shown as ">0-x", which must be greater than zero.
2-15
-------
IWAIR Technical Background Document
Section 2.0
Table 2-4. Input Parameters for Waste Piles
Input Parameter
Units
Default
Value
Range3
Basis
Unit Design and Operating Parameters
Biodegradation toggle
Operating life of waste pile
Height of waste pile
Surface area of waste pile
Average annual quantity of waste
added to waste pile
Dry bulk density of waste
none
yr
m
m2
Mg/yr
g/cm3
off
none
none
none
none
1.4
>0
1-10
20-
1.3E+6
>0
>0
Required input
Required input
Required input
ERG and Abt (1992)— uses default
of 1.4 g/cm3 for waste sludge
U.S. EPA (1991)— uses default of
1.8 g/cm3 for waste pile
Coburn et al. (1988) — uses "liquid in
fixed waste" density of 1.16 g/cm3
U.S. EPA (1989)— uses sludge
density of 1.01 g/cm3
Waste Characterization Information
Average molecular weight of waste
Total porosity of waste
Air-filled porosity of waste
g/mol
volume
fraction
volume
fraction
none
0.5
0.25
>1
>0-<1
>0-total
porosity
Required input for organic phase
wastes
U.S. EPA (1991)— input used for all
model waste piles
Coburn et al. (1988)— default input
for CHEMDAT8 waste piles
U.S. EPA (1991)— input used for all
model waste piles
Coburn et al. (1988)— default input
for CHEMDAT8 waste piles
"Ranges are inclusive, except for parameters with ranges shown as ">0-x", which must be greater than zero.
2-16
-------
IWAIR Technical Background Document Section 2.0
waste matrices and partitioning. A general rule of thumb is that wastes that consist of 10 percent
or more organics are best modeled as organic phase.
The molecular weight of the organic phase of the waste is a key input for modeling
emissions from organic-phase wastes (this is the molecular weight of the bulk liquid, not the
individual chemical). Higher waste molecular weights will result in higher emissions estimates.
The range of molecular weights for common organic chemicals that might be found in Industrial
D wastes spans an order of magnitude, from about 30 g/mol to about 300 g/mol. Therefore,
setting this value as accurately as possible will produce the most accurate emissions estimates. In
risk mode, no default value is provided; however, Appendix B of the IWAIR User's Guide
provides an equation for estimating an appropriate molecular weight from the concentrations and
molecular weights of the components of the waste. Because these components may include
chemicals not being modeled in a particular IWAIR run, IWAIR cannot calculate this directly
from user inputs and chemical properties. In allowable concentration mode, the molecular
weight of the organic phase is set to the molecular weight of the individual chemical modeled,
simulating emissions from pure component.
CHEMDAT8 is fairly sensitive to the total porosity and air porosity values that are used.
Total porosity includes air porosity and the space occupied by oil and water within waste or soil.
Total porosity is related to bulk density of the waste (which is also an input) as follows:
, BD
et = 1 - — (2-12)
where
et = total porosity (unitless)
BD = bulk density (g/cm3)
ps = particle density (g/cm3).
A typical value for ps is 2.65 g/cm3 (Mason and Berry, 1968). Default values are
provided for waste bulk density, total porosity, and air-filled porosity, but the user is strongly
encouraged to enter site-specific data, if available.
Meteorological Conditions. Two meteorological parameters are used as inputs to
CHEMDAT8: annual average wind speed and annual average temperature. By default, IWAIR
uses the annual average temperature and wind speed for the meteorological station identified as
most representative for the site location. However, the user may override these with site-specific
data.
The temperature is used for several calculations to adjust chemical properties that are
dependent on temperature. These include the vapor-liquid equilibrium partition coefficient and
the gas-phase diffusivity. The temperature correction adjustment for vapor-liquid equilibrium
partition coefficient uses the Antoine's coefficients to calculate a ratio of the constituent's vapor
pressure at the system temperature to the constituent's vapor pressure at 25°C. This ratio is used
2-17
-------
IWAIR Technical Background Document Section 2.0
to adjust the vapor-liquid partition coefficient when either Raoult's law or Henry's law is used.
The Henry's law coefficient is sometimes estimated by the constituent vapor pressure divided by
solubility. Although it is more correct to consider the liquid-phase activity coefficient, it is more
difficult to assess a temperature adjustment factor for the liquid-phase activity coefficient (or
solubility) than for vapor pressure. In addition, solubility is generally less temperature-dependent
than vapor pressure. There has been some progress in developing temperature-dependent
correlations for Henry's law coefficients in recent years,3 but these correlations were not readily
available at the time of the development of CHEMDAT8, and they are still not currently
available for the range of chemicals modeled by IWAIR. Therefore, the best approach for
adjusting the Henry's law constants from input values determined at 25°C to the prevailing
temperature of the WMU is to use the temperature correction factors developed for vapor
pressure, which are based on Antoine's coefficients.
Wind speed is used to select the most appropriate empirical emission correlation equation
in CHEMDAT8; there are several of these correlations, and each one applies to a specific range
of wind speeds and unit sizes. The CHEMDAT8 model is insensitive to wind speeds for long-
term emission estimates from land-based units.
2.3.3 Input Parameters for Surface Impoundments
The input parameters for surface impoundments are presented in Table 2-5.
Unit Design Data. The annual waste quantity (flow rate), the dimensions of the surface
impoundment, and whether or not the impoundment is aerated are critical input parameters for
impoundments. Because these are so critical and because the values of these parameters for a
specific unit to be modeled should be readily available to the user, no default values are provided
for these parameters. Operating life is also included here. This value is used to cap the default
exposure durations used by IWAIR (30 years for residents and 7.2 years for workers) if the
operating life is shorter than the relevant default exposure duration.
Also in this category is the biodegradation toggle. This option, in conjunction with the
active biomass input, allows the user to determine what type of biodegradation is modeled. In
biologically active surface impoundments, two processes occur: growth of biomass, which
provides a growing matrix for chemical adsorption and loss through settling, and direct
biodegradation of chemical constituents as the bacteria that form the biomass consume
constituent mass. Direct biodegradation cannot occur if there is no active biomass. If an
impoundment is biologically active, it may go through a transitional period during which there is
active biomass (so adsorption and settling losses occur), but the biomass is not yet adapted to
consume the specific chemicals present (so direct biodegradation is not occurring). This
transitional period will usually end as the biomass acclimates and adapts to the chemicals
present.
By default, biodegradation is set to ION I for surface impoundments. This toggle controls
direct biodegradation. Setting biodegradation to I OFF | turns off direct biodegradation, but does
3 e.g., the compilations of Sanders; see http://www.mpch-mainz.mpg.de/~sander/res/henry.html
2-18
-------
IWAIR Technical Background Document
Section 2.0
Table 2-5. Input Parameters for Surface Impoundments
Input Parameter
Units
Default
Value
Range3
Basis
Unit Design Data
Biodegradation toggle
Operating life
Depth of liquid in surface
impoundment
Surface area of surface
impoundment
Average annual flow rate
none
yr
m
m2
mVyr
on
none
none
none
none
>0
>0
81-8.09E+6
>0
Required input
Required input
Required input
Required input
Aeration Data
Fraction of surface area agitated
Submerged air flow rate
unitless
mVs
none
none
>0-1
>0
Required input for aerated units
Required input for diffused air
aeration
Mechanical Aeration Information
Oxygen transfer rate
Number of aerators
Total power input to all aerators
Power efficiency of aeratorsb
Aerator impeller diameter
Aerator impeller rotational speed
Ib
O2/h-hp
unitless
hp
fraction
cm
rad/s
3
none
none
0.83
61
130
>0
>1
>0.25
>0-1
>0-
100*/WMU
area
>0
U.S. EPA (1991)— range = 2.9 to
3.01bO2/h-hp
Required input for mechanically
aerated impoundments
U.S. EPA (1991)— input for
medium-sized, aerated surface
impoundments - model units
T02I and T02J
U.S. EPA (1991)— range = 0.80 to
0.85
U.S. EPA (1991)— input used for
all model surface
impoundments
U.S. EPA (1991)— input used for
all model surface
impoundments
Waste Characteristic Data
Average molecular weight of waste
Density of waste
g/mol
g/cm3
none
none
>1
>0
Required input for organic-phase
wastes
Required input for organic-phase
wastes
(continued)
2-19
-------
IWAIR Technical Background Document
Section 2.0
Table 2-5. (continued)
Input Parameter
Active biomass concentration (as
mixed-liquor volatile suspended
solids (MLVSS)) in the surface
impoundment
Total suspended solids (TSS) in
surface impoundment influent
Total organics (total organic carbon
or chemical oxygen demand) in
surface impoundment influent
Total biorate
Units
g/L
g/L
mg/L
mg/g
biomass-h
Default
Value
0.05
0.2
200
19
Range3
0-1,000
0-1,000
0-1,000,000°
>0
Basis
Coburnetal. (1988)— default
value used for surface
impoundments in developing
biodegradation rate constants
U.S. EPA (1994a)— recommended
default for quiescent surface
impoundments; suggests a
default for aerated surface
impoundments = 0.25 g/L
U.S. EPA (1994a)— range = 0.11-
0.40 for surface
impoundments designed for
biodegradation
U.S. EPA (1994a)— default value
recommended in
CHEMDAT8
a Ranges are inclusive, except for parameters with ranges shown as ">0-x", which must be greater than zero.
b Power efficiency is a misnomer that is carried over from CHEMDAT8. This input is really the oxygen
correction factor for the liquid-phase turbulent mass transfer coefficient (see Equation 2-63). The actual
power efficiency, used in the equation for gas-phase turbulent mass transfer coefficient (see the equation for
power number in the list of parameters for Equation 2-64), is hardwired to a value of 0.85 in CHEMDAT8.
In order to maintain consistency with CHEMDAT8, IWAIR also terms this input "power efficiency" but uses
it as the oxygen correction factor and hardwires the real power efficiency with a value of 0.85. The default
value provided in the IWAIR model and the parameter guidance provided in Appendix B of the IWAIR
User's Guide for this input are consistent with its use as the oxygen correction factor.
b Must be greater than or equal to the sum of the concentrations of all organic chemicals specified as being in
the waste by the user in risk calculation mode.
2-20
-------
IWAIR Technical Background Document Section 2.0
not affect adsorption loss. Setting active biomass to zero turns off biomass growth, so that
adsorption losses are limited to adsorption to inlet solids. Setting active biomass to zero also
turns off direct biodegradation, as biodegradation cannot occur without active biomass. IWAIR
enforces this if the user sets biodegradation to ION I and then sets active biomass to zero by
automatically resetting the biodegradation option to I OFF |.
Aeration. Factors that have an impact on the relative surface area of turbulence and the
intensity of that turbulence are important in determining the rate of volatilization of the
chemicals in aerated surface impoundments. IWAIR can model two types of aeration, either
separately or in combination: mechanical aeration and diffused air aeration.
Mechanical aeration is achieved using impellers rotating in the impoundment and
agitating the liquid. Diffused air aeration is achieved through the use of diffusers that force air
through the liquid, thus agitating the liquid. The extent and intensity of the turbulence are
important factors in estimating emissions from aerated impoundments. For both types of
aeration, the fraction of the surface area that is turbulent is an important input and no default is
provided.
For mechanical aeration, the model has several input parameters that have an impact on
the degree and intensity of the turbulence created by the aeration (or mixing). Total power,
power per aerator (number of aerators), and impeller diameter have some impact on the emission
results. A default value is provided for impeller diameter; but the user is encouraged to enter a
site-specific value, if available. No default is provided for number of aerators or total power.
The other parameters, such as impeller speed, power efficiency, and oxygen transfer rate have
only a slight impact on the estimated emissions; default values are provided for these inputs, but
the user is encouraged to enter site-specific values, if available.
For diffused air aeration, the key input is the submerged air flow. No default is provided
for this parameter. The diffused air portion of CHEMDAT8 does not include correlations for
calculating a turbulent mass transfer coefficient to account for increased emissions as a result of
surface turbulence caused by the air flow through the liquid. However, the equations for
turbulent mass transfer coefficient for mechanically aerated systems can be (and are) used to
estimate this by entering inputs for a "virtual" aerator. IWAIR uses the default values for
impeller diameter, impeller speed, power efficiency, and oxygen transfer rate to create a virtual
aerator for diffused air systems. The total power and number of aerators are set based on the size
of the unit. This is discussed in more detail in Section 2.4.4.4.
Waste Characterization Inputs. In order to generate an accurate estimate of a
constituent's volatile emissions, a user of IWAIR must define the physical and chemical
characteristics of the waste that will be managed in the WMU. In particular, the user must
determine if the waste is best described as a dilute mixture of chemical compounds (aqueous) or
if it should be considered organic, containing high levels of organic compounds or a separate
nonaqueous organic phase. These two different types of waste matrices influence the degree of
partitioning that will occur from the waste to the air. Partitioning describes the affinity that a
constituent has for one phase (for example, air) relative to another phase (for example, water)
that drives the volatilization of organic chemicals. The choice of waste matrix will significantly
2-21
-------
IWAIR Technical Background Document Section 2.0
affect the rate of emissions from the waste. See Section 2.2 for a more detailed discussion of
waste matrices and partitioning. A general rule of thumb is that wastes that consist of 10 percent
or more organics are best modeled as organic phase. CHEMDAT8 (and IWAIR) can model both
aqueous- and organic-phase wastes for nonaerated (quiescent) surface impoundments, but can
model only aqueous-phase wastes for aerated surface impoundments.
CHEMDAT8 includes an input for the fraction of waste that is "oily" (i.e., organic). In
IWAIR, if the user models an organic waste, IWAIR assumes that this fraction is 1.
The molecular weight of the organic phase of the waste is a key input for modeling
emissions from organic-phase wastes (this is the molecular weight of the bulk liquid, not the
individual chemical). Higher waste molecular weights will result in higher emissions estimates.
The range of molecular weights for common organic chemicals that might be found in Industrial
D wastes spans an order of magnitude, from about 30 g/mol to about 300 g/mol. Therefore,
setting this value as accurately as possible will produce the most accurate emissions estimates. In
risk mode, no default value is provided; however, Appendix B of the IWAIR User's Guide
provides an equation for estimating an appropriate molecular weight from the concentrations and
molecular weights of the components of the waste. Because these components may include
chemicals not being modeled in a particular IWAIR run, IWAIR cannot calculate this directly
from user inputs and chemical properties. In allowable concentration mode, the molecular
weight of the organic phase is set to the molecular weight of the individual chemical modeled,
simulating emissions from pure component.
The density of the waste is also needed for modeling emissions from organic-phase
wastes. In risk mode, no default value is provided; however, Appendix B of the IWAIR User's
Guide provides an equation for estimating an appropriate density from the concentrations and
densities of the components of the waste. Because these components may include chemicals not
being modeled in a particular IWAIR run, IWAIR cannot calculate this directly from user inputs
and chemical properties. In allowable concentration mode, the density of the organic phase is set
to 1 g/cm3, consistent with the assumption that 1,000,000 mg/L is pure component.
Factors that influence the rate of biodegradation are important in determining emissions
from surface impoundments. Unlike the biodegradation rate model that is used for land
application units, landfills, and waste piles, the biodegradation rate model used in CHEMDAT8
for surface impoundments is dependent on the amount of active biomass in the WMU.
Therefore, the active biomass concentration is a critical parameter for impoundments (see the
discussion above on biodegradation toggle and how it interacts with active biomass). A default
value is provided for active biomass if the user chooses to model biodegradation, but the user is
encouraged to enter a site-specific value, if available. No default value is provided if the user
chooses not to model biodegradation; unless users explicitly want to model the transitional
period before the biomass has adapted to the chemicals present, they should set active biomass to
zero when the biodegradation toggle is set to I OFF |.
The TSS and total organics in the influent and the total biorate have an impact on the rate
of biomass production and subsequently the amount of constituent that is adsorbed onto the
solids. These inputs, however, have little or no impact on the estimated emission rates for most
2-22
-------
IWAIR Technical Background Document Section 2.0
of the constituents included in IWAIR. Default values are provided, but the user is strongly
encouraged to enter site-specific values, if available.
Typically, active biomass in the impoundment will be less than TSS in the influent.
However, this might not be the case in all situations. The most frequent exception would be in
activated sludge units where a portion of the effluent biomass is recovered and recirculated back
into the unit. There may also be occasions where the biomass growth rate exceeds the solids
settling rate within the unit so that the in-basin active biomass concentration is greater than the
influent TSS concentration without a return activated sludge. These conditions are less frequent
for surface impoundments than for tanks, which cannot be modeled using IWAIR.
Meteorological Conditions. Two meteorological parameters are used as inputs to
CHEMDAT8: annual average wind speed and annual average temperature. By default, IWAIR
uses the annual average temperature and wind speed for the meteorological station identified as
most representative for the site location. However, the user may override these with site-specific
data.
Emissions estimates for nonaerated impoundments are influenced by both temperature
and wind speed. Emissions for aerated impoundments are predominantly driven by the turbulent
area and associated mass transfer coefficients; therefore, the emissions from aerated
impoundments are not strongly affected by the wind speed; they are affected by temperature.
Wind speed is used to select the most appropriate correlation equation for calculating the liquid-
phase quiescent mass transfer coefficient.
The temperature is used for several calculations to adjust chemical properties that are
dependent on temperature. These include the vapor-liquid equilibrium partition coefficient and
the gas-phase diffusivity; however, temperature also affects the liquid-phase diffusivity and the
liquid-phase turbulent mass transfer coefficient. The temperature correction adjustment for
vapor-liquid equilibrium partition coefficient uses the Antoine's coefficients to calculate a ratio
of the constituent's vapor pressure at the system temperature to the constituent's vapor pressure
at 25°C. This ratio is used to adjust the vapor-liquid partition coefficient when either Raoult's
law or Henry's law is used. The Henry's law coefficient is sometimes estimated by the
constituent vapor pressure divided by solubility. Although it is more correct to consider the
liquid-phase activity coefficient, it is more difficult to assess a temperature adjustment factor for
the liquid-phase activity coefficient (or solubility) than for vapor pressure. In addition, solubility
is generally less temperature-dependent than vapor pressure. There has been some progress with
temperature-dependent correlations for Henry's law coefficients in recent years,4 but these were
not readily available at the time of the development of CHEMDAT8, and they are still not
currently available for the range of chemicals modeled by IWAIR. Therefore, the current
temperature correction factor applied to the Henry's law constants based on the temperature
dependence of constituent's vapor pressure as estimated using Antoine's equation remains the
best approach for adjusting the Henry's law constants (input values determined at 25°C) to the
prevailing temperature of the WMU. Depending on the residence time of the waste in the
impoundment, the temperature of the waste is not expected to vary significantly with changing
4 e.g., the compilations of Sanders; see http://www.mpch-mainz.mpg.de/~sander/res/henry.html
2^23
-------
IWAIR Technical Background Document Section 2.0
atmospheric temperatures. Therefore, annual average temperatures are used to estimate the
average waste temperature in the impoundment.
2.4 Mathematical Development of Emissions
This section describes how the inputs described in Section 2.3 are used to calculate the
mass emission rate for use in subsequent risk estimates. Most of the mathematical equations
used to calculate emissions were taken from the CHEMDAT8 emission model developed by
EPA. The documentation of the CHEMDAT8 model can be accessed from EPA's Web site
(http://www.epa.gov/ttn/chief/software.html, then select "WaterS and ChemdatS"). For
convenience, the necessary equations are provided here. For a more detailed discussion or
derivation of these equations, the reader is referred to the CHEMDATS model documentation
(U.S. EPA, 1994a). Some additional equations were needed to convert the CHEMDATS fraction
emitted to mass emission rates. Through the remainder of this section, the subsection heads
indicate whether the equations in that subsection came from CHEMDATS or were added by
IWAIR.
2.4.1 Landfills
Inputs and assumptions The basic assumptions used for modeling landfills are as
follows:
• The landfill operates for tlife years filling N cells of equal size sequentially.
• The active cell is modeled as being instantaneously filled at time t = 0, and
remains open for tlife/Nyears; this is the time it takes to fill one landfill cell.
• Emissions are only calculated for one cell for tlif(/Nyears (it is assumed that the
cell is capped after tlife/Nyears and that the emissions from the capped landfill
cells are negligible); the time of calculation is calculated as follows:
365.25 x 24 x 3,600
- (2-13)
cells
where
tcalc = time of calculation (s)
tlife = lifetime of unit (yr)
Ncens = total number of cells (unitless)
365.25 = unit conversion (d/yr)
24 = unit conversion (h/d)
3,600 = unit conversion (s/h).
2-24
-------
IWAIR Technical Background Document Section 2. 0
• The waste is homogeneous, with an initial concentration of 1 mg/kg for the
allowable concentration mode or a user-specified concentration for the risk mode;
the landfill may also contain other wastes with different properties.
• Loading is calculated from the annual waste quantity and the size of the landfill,
as follows:
L = (2-14)
Atotal X dtotal
where
L = waste loading rate (Mg/m3 = g/cm3)
Qamuai = annual waste quantity (Mg/yr)
A totai = total area of unit (m2)
dtotai = total depth of unit (m).
Note that if the unit is a monofill receiving only the waste modeled, the loading
should equal the bulk density entered by the user. If the unit receives other wastes
in addition to the waste modeled, the loading should be less than the bulk density
of the waste. The loading cannot exceed the bulk density of the waste; if this
condition occurs, the user will get an error message and will be required to change
the inputs to eliminate this condition.
• Landfill cell areas and depth are used for the model run: Acell = Atotal /Ncells;
dceu = dtotal.
• By default, biodegradation is not modeled for landfills, but the user may choose to
turn biodegradation on. If the user chooses to model it, biodegradation is modeled
as a first-order process based on soil half-life data.
Calculation of the equilibrium partition coefficient (CHEMDAT8V The emissions
from the landfill are based primarily on the vapor-phase concentration of the pore-space gas
within the landfill (in equilibrium with the disposed waste) and the diffusion rate of the
constituents in this pore-space gas to the soil surface. The vapor-phase concentration is
determined by the vapor-liquid equilibrium coefficient (Keq). The calculation of this coefficient
is dependent on the type of waste managed.
For organic-waste matrices, the vapor-liquid equilibrium coefficient is based on the
constituent's partial vapor pressure (often referred to as Raoult's law), as follows:
T P MW e
l^ _ corr vap waste a ,~ -> r\
eq RTL l " ^
2-25
-------
IWAIR Technical Background Document Section 2.0
where
Keq = vapor-liquid equilibrium coefficient for constituent (g/cm3 per g/cm3)
Tcorr = temperature correction factor for vapor pressure for constituent (unitless)
Pvap = pure component vapor pressure of constituent at 25°C (atm)
MWwaste = average molecular weight of the waste (g/mol)
ea = air-filled porosity (cm3/cm3)
R = universal gas constant = 82.1 cm3-atm/mol-°K
T = temperature of the system (°K).
The temperature correction factor is based on the ratio of the constituent's vapor pressure,
as calculated using Antoine's equation at the system's temperature, and the constituent's vapor
pressure at the reference temperature for which the vapor pressure is provided, which is assumed
to be 25°C in IWAIR (that is, all chemical properties in the IWAIR database correspond to the
property value at 25°C). The temperature correction factor is calculated as follows:
(2-16)
where
VPb = Antoine's vapor pressure constants for constituent
VPC = Antoine's vapor pressure constant C for constituent.
The Antoine's constants used in IWAIR assume the Antoine's equation (which is logPvap = A
B/(C + T)) and are developed for calculating the vapor pressure, Pvap, in mmHg given the
temperature, T, in °C.
For aqueous matrices, the vapor-liquid equilibrium coefficient is based on the
constituent's Henry's law constant, as follows:
T
v _ con
N is;
where
H = Henry's law constant at 25°C (atm-m3/mol)
MWwaste = average molecular weight of the waste =18 g/mol = molecular weight of
water
18 = unit conversion factor for aqueous waste (cm3/mol =18 g/mol x 1 cm3/g)
106 = unit conversion factor (cm3/m3).
Calculation of the effective diffusivitv (CHEMDAT8V The effective diffusivity of
constituent in a porous medium is calculated as follows:
2-26
-------
IWAIR Technical Background Document
Section 2.0
3.33
(2-18)
where
Deff
Da
T
1 C,gai
effective diffusivity of constituent in the system (cm2/s)
diffusivity of constituent in air at 25°C (cm2/s)
temperature correction factor for gas diffusivity (unitless)
(T/298.15)1'75
total porosity (cm3/cm3).
Calculation of the fraction emitted (CHEMDAT8). The equation used to calculate the
fraction emitted is dependent on the volatilization rate constant, the biodegradation rate constant,
and the time period for the calculation. The volatilization rate constant is calculated as follows:
K =
D
eff
i 2
(2-19)
where
Kv = volatilization rate constant for constituent (1/s)
dwmu = characteristic depth of the WMU (cm) = dtotal /100 for a landfill.
The fraction emitted is calculated using one of the following three solution algorithms,
depending on the biodegradation (bsoil) and volatilization rate (Kv) constants.
If Kv/bsoll< 0.1089,
emitted
K
1-e
IfKv/bsoll > 0.1089 andKv tcalc < 0.22 (short-term solution),
(2-20)
f =9
1 emitted **\
K t
v L calc
1-
u calc u soil
(2-21)
2-27
-------
IWAIR Technical Background Document
Section 2.0
IfKv/bsoil > 0.1089 andKv tcalc > 0.22 (first term of the Taylor series expansion solution),
f = —
emitted _2
\-e
ale I ^j-Kv+bsoii
1 +
4
+ 0.1878
(2-22)
where
Emitted
fraction of constituent emitted to the atmosphere (unitless)
soil biodegradation rate constant for constituent (1/s).
Calculation of the fraction biodegraded (CHEMDAT8) The fraction biodegraded and
the fraction emitted are both dependent on the volatilization and biodegradation rate constants,
and their values are not independent of each other. The fraction biodegraded is calculated using
one of the following two equations depending on the biodegradation and volatilization rate
constants, as follows:
IfKv tcalc < 0.22 (short-term solution),
= 1-1-2
X,t
v calc
g tcalcbsoil
-f
emitted
(2-23)
IfKv tcalc > 0.22 (first term of the Taylor series expansion solution),
1-
1-e
+ 0.1878
p-'calc^oil I _ f
c I i emitted
(2-24)
where
fbio = fraction of constituent biodegraded in the WMU (unitless).
Calculation of the emission flux rate (IWAIRV The average emission flux rate for the
landfill can be calculated as follows:
E =
^annual waste emitted
Acell X Pb X 365'25 X 24 X 3'600
(2-25)
2-28
-------
IWAIR Technical Background Document Section 2.0
where
E = emission flux rate of constituent (g/m2-s)
CWaste = concentration of constituent in waste (mg/kg = g/Mg)
Acell = area of cell (m2)
pb = bulk density of waste in landfill (g/cm3)
365.25 = unit conversion (d/yr)
24 = unit conversion (h/d)
3,600 = unit conversion (s/h).
2.4.2 Land Application Units
Inputs and assumptions The assumptions used for modeling land application units are
as follows:
• Waste application occurs Nappl times per year. The land application unit is
modeled using time steps equal to the time between applications, as follows:
365.25 x 24 x 3,600
W N (2-26)
^appl
where
Nappi = number of applications per year (yr"1)
365.25 = unit conversion (d/yr)
24 = unit conversion (h/d)
3,600 = unit conversion (s/h).
The land application unit operates for tltfe years and is modeled for tltfe plus 30
years, in order to account for up to 30 years of postclosure exposure. The total
number of time steps modeled is thus
Nsteps = (tiife+30)x Nappl (2-27)
where
Nsteps = total number of time steps modeled (unitless)
tiife = operating life of unit (yr).
This total number of time steps, Nsteps, cannot exceed 32,766 because of code
limitations for integer variables. This is unlikely to result in practical limitations,
unless the operating life is very long and the number of applications per year very
2^29
-------
IWAIR Technical Background Document Section 2.0
high. For example, daily applications (365 applications/year) for 59 years would
still be within this limitation.
• The waste is homogeneous, with an initial concentration of 1 mg/kg for the
allowable concentration mode or a user-specified concentration for the risk mode.
• Loading is calculated from the annual waste quantity and the size of the land
application unit as follows:
L = N (2.28)
N.PPI x A x d«
where
L = loading rate (Mg/m3 = g/cm3)
Qamuai = annual quantity of waste (Mg/yr)
A = area of unit (m2)
dtill = tilling depth (cm)
100 = unit conversion (cm/m).
By default, biodegradation is modeled as a first-order process based on soil half-
life data. The user may choose to turn biodegradation off.
The characteristic depth of a land application unit used in Equation 2-19
(calculation of Kv) is the tilling depth (dwmu = dall).
The volume of the land application unit remains constant. To maintain this
assumption, it is assumed that as more waste is applied, an equal volume of
waste/soil mixture is buried or otherwise removed from the active tilling depth.
The equipment used to incorporate and mix the waste with the soil in a land
application unit typically does so at a fixed depth; therefore, the depth of waste
incorporation is fixed. If the depth of waste added to the unit over the active life
of the land application unit is significant relative to the tilling depth, subsequent
applications of waste will leave the bottom-most layer of contaminated soil
untilled (i.e., buried). If subsequent waste applications were added to the same
fixed mass of soil, the model as constructed would perceive this as adding a fixed
quantity of pure constituent to the fixed soil mass during each waste application.
As such, the land application unit could eventually have higher constituent
concentrations than the applied waste (for compounds that persist in the
environment). Therefore, the burial loss term is needed for an accurate estimate
of the maximum steady-state soil concentration (and emissions rate) according to
mass balance principles.
2-30
-------
IWAIR Technical Background Document Section 2.0
IWAIR further assumes that this buried waste layer does not have any significant
impact on the emission estimates. There are several reasons why the buried waste
is not expected to contribute significantly to the emissions. At the time of burial,
the buried waste constituent concentration is less than (or at most equal to) the
constituent concentration in the tilled layer of the land application unit. Secondly,
experience with emission estimates of buried waste using model equations
developed by Jury et al. (1990) shows that the buried waste layer contributions to
emissions are typically 1 to 2 orders of magnitude less than the emissions from the
surface layer (depending on the relative depths of each layer) when the initial
concentrations are homogeneous (a requirement for the Jury model solution).
Constituent burial tends to be a significant constituent removal mechanism only
when other constituent removal mechanisms are essentially zero (i.e., chemicals
that do not degrade or volatilize). Constituent loss in buried waste is a
simplifying assumption with respect to volatilization, but this assumption
provides a much better simulation of the land application unit constituent
exposure scenarios than when waste burial is not included. Without "burial"
losses, land application unit soil concentrations can exceed those in the original
waste material. These "unlikely" high soil concentrations provide greater errors in
the estimated long-term volatilization rates than are projected by the land
application unit model with constituent burial losses.
Calculation of fraction emitted and fraction biodegraded (CHEMDAT8) The
IWAIR model calculates the fraction emitted and the fraction biodegraded for each chemical in
the land application unit using the CHEMDAT8 equations shown in Equations 2-15 through
2-24, as applicable, for the time interval between applications (i.e., the time of the calculation,
tcalc, from Equation 2-26). The calculation is made for the first application given the inputs and
assumptions outlined above. As the model is linear (first-order) with respect to constituent
concentration, the fraction emitted and the fraction biodegraded are independent of the starting
concentration. Consequently, these calculated fractions can be applied to successive waste
applications assuming that the volume of the land treatment unit remains constant; this
assumption is also documented above. The IWAIR model takes the fraction emitted and fraction
biodegraded and calculates the long-term emissions that occur from successive use. This is an
enhancement made in IWAIR and is documented in the following subsections.
Calculation of the emission rate (IWAIRV The emission rate for a land application
unit is dependent on the starting concentration or mass of constituent within the land application
unit for a given application. For the first application, the mass of constituent in the land
application unit just after the first application is
M = M ^annual X waste
1Vistart,l 1V1appl M (2-29)
^appl
where
Ms,arU = mass of chemical in unit at start of time step 1 (g)
2-31
-------
IWAIR Technical Background Document
Section 2.0
Mappl = mass of chemical added during one application (g)
CWaste = concentration of chemical in waste (mg/kg = g/Mg).
The mass of constituent in the land application unit at the end of the first time of
calculation (just prior to more waste being added) is
M
end,l
= Mappl x (1 -
emitted
(2-30)
where
Mendjl
f
Emitted
*bio
= mass of chemical in unit at end of time step 1 (g)
= fraction emitted (unitless).
= fraction biodegraded (unitless).
Note that fraction emitted and fraction biodegraded, which are calculated according to
Equations 2-20 through 2-24, are not independent of each other despite their appearance as
separate terms in the above equation. Fraction emitted depends on biodegradation rate and other
variables, and fraction biodegraded depends on biodegradation rate and fraction emitted, among
other variables.
The generalized equation for the starting mass of constituent (just after any waste
application number, «, and taking into account the "burial" loss needed to maintain a constant
land application unit volume) is
Mstart,n = Mappl
M
end,n-
_ appl
(2-31)
where
M,
M,
start,n
end,n-l
= mass of chemical in unit at start of time step n (g)
= mass of chemical in unit at end of time step n-1 (g)
= depth of waste applied (cm), see Equation 2-32.
Depth of waste applied is calculated as
appl
^annual
x 100
Nappl X Pb
(2-32)
where
pb = bulk density of waste (g/cm = Mg/m)
2-32
-------
IWAIR Technical Background Document Section 2. 0
Note that dtill must exceed dappl and should probably be at least three to four times dappl. The user
will be warned if dm does not exceed dappl.
The generalized equation for the ending mass of constituent in the land application unit
for any waste application number, «, (just prior to the n+1 waste application) is
Mend,n = MStart,n X C1 ~ femrtted ~ fbio) (2-33)
where
Mendjn = mass of chemical in unit at end of time step n (g).
The generalized equation for the mass of constituent emitted during any application
period (time of calculation) is
Memitted,n = Mstart,n X femitted (2-34)
where
Memittedn = mass of chemical emitted in time step n (g).
For each time period, the emission flux rate is calculated as follows:
where
En = emission flux rate in time step n (g/m2-s).
The starting mass, ending mass, and emitted mass of constituent are calculated for each
time step for a period equal to the life of the unit plus 30 years. This time series of emission rates
for each time step must then be converted to a time-averaged emission rate for a time period
corresponding to exposure assumptions. Three exposure scenarios are possible: for carcinogenic
risk, IWAIR uses an average for a time period that corresponds to the exposure duration: 30 years
for a resident or 7 years for a worker. For noncarcinogens, IWAIR uses a 1-year average as an
indicator of the highest exposure experienced over a chronic duration.
The additional 30 years postclosure are modeled to ensure that the period of maximum
emissions is captured. For chemicals that tend to volatilize quickly, this is likely to occur during
operation of the unit, as new waste additions continue to be made. For chemicals that do not tend
to volatilize quickly, but build up in the unit, this is likely to occur postclosure (when waste
2-33
-------
IWAIR Technical Background Document Section 2.0
additions stop and the maximum concentration is achieved in the unit). To capture the maximum
period, IWAIR calculates all possible 30-year and 7-year averages over the life of the unit plus 30
years and chooses the maximum of these. For example, for a unit with an operating life of 10
years, eleven 30-year averages are possible, the first starting in year 1 of operation and running
through 10 years of operation and 20 years postclosure, and the last starting in the first year
postclosure (i.e., year 11) and running for 30 years.
The emission rate displayed on the emission screen in IWAIR and in the printed reports
for all chemicals modeled is the maximum 1-year average used for noncarcinogens. However,
the air concentration displayed on the RESULTS screen and in the printed reports is based on the
appropriate average emission rate for the chemical and receptor. If a chemical has both a
carcinogenic and a noncarcinogenic health benchmark (so that both risk and HQ are calculated),
the air concentration displayed on the RESULTS screen corresponds to the carcinogenic risk
calculation, not the noncarcinogenic HQ calculation. The interested user can use Equation 6-1 to
convert displayed 1-year emission rates to the corresponding 1-year air concentration for such
chemicals. Similarly, Equation 6-1 can be used to convert the 30- or 7-year air concentration to
the corresponding emission rate (which is not displayed).
2.4.3 Waste Piles
Inputs and assumptions. The modeling assumptions used for modeling waste piles are
as follows:
• The waste pile is modeled as a batch process with the waste remaining in the
waste pile for one average residence time (see time of calculation equation
provided in Equation 2-36). The model solution is appropriate for either of the
following two scenarios:
1. The waste pile is instantaneously filled at time t = 0 and remains dormant
(no other waste added) for one average residence time, at which time the
entire waste pile is emptied and completely filled with fresh waste.
2. An annual quantity of waste is added to the waste pile consistently (in
small quantities) throughout the year, and a corresponding quantity of the
oldest waste within the waste pile is removed from the waste pile (so that
the waste pile is essentially a plug-flow system).
• The waste is homogeneous, with an initial concentration of 1 mg/kg for the
allowable concentration mode or a user-specified concentration for the risk mode.
• By default, biodegradation is not modeled for waste piles. Waste piles are not
generally designed for biodegradation; however, if residence times of waste in the
waste pile are on the order of months or years, naturally occurring microorganisms
could potentially acclimate and degrade constituents within the waste pile. The
wastes for which IWAIR was designed are industrial wastes, not hazardous wastes
(and so presumably are not toxic enough to fail the Toxicity Characteristics
2-34
-------
IWAIR Technical Background Document Section 2.0
Leaching Procedure, because that would make them hazardous). Therefore, while
a specific waste might not be very conducive to biomass growth, it cannot be
widely assumed that the wastes for which this model was designed would be toxic
to any potential biomass. Therefore, the user has the option of turning
biodegradation on if site-specific conditions suggest that biodegradation is
occuring. If the user chooses to model it, biodegradation is modeled as a first-
order process based on soil half-life data.
• Loading is the bulk density of the waste material (L = pb).
• The time of calculation is equal to one average residence time of waste in the
waste pile. The time of calculation (or residence time) is calculated as follows:
A x h x p x 365.25 x 24 x 3,600
'oak = (2-36)
where
tcalc = time of calculation (s)
A = area of unit (m2)
h = height of waste pile (m)
pb = bulk density of waste (g/cm3 = Mg/m3)
Qannuai = annual waste quantity (Mg/yr)
365.25 = units conversion (d/yr)
24 = units conversion (h/d)
3,600 = units conversion (s/h).
• The waste pile geometry is modeled as a square box. The sides are assumed to be
essentially vertical and are assumed to be negligible in the overall surface area of
the waste. The shape of the upper surface is assumed to be square. The area and
height of this box are both user inputs and are used by the emissions component.
Calculation of fraction emitted and fraction biodegraded (CHEMDAT8). The
IWAIR model calculates the fraction emitted and the fraction biodegraded for each chemical in
the waste pile using Equations 2-15 through 2-24, as applicable, for one residence time (i.e., the
time of the calculation, tcalc, from Equation 2-36).
Calculation of the emission flux rate (IWAIRV The average emission flux rate for the
waste pile can be calculated as follows:
Biannual waste emitted ,~ ^r7\
- (z-j/l
A x 365.25 x 24 x 3,600 v '
2-35
-------
IWAIR Technical Background Document Section 2.0
where
E = emission flux rate of constituent (g/m2 - s)
CWaste = concentration of constituent /' in waste (mg/kg = g/Mg)
femitted = fraction of constituent /' emitted to the atmosphere (unitless)
365.25 = units conversion (d/yr)
24 = units conversion (h/d)
3,600 = units conversion (s/h).
2.4.4 Surface Impoundments
Inputs and Assumptions. The basic modeling assumptions used for modeling surface
impoundments are somewhat different for aqueous- and organic-phase wastes. For aqueous-
phase wastes, assumptions include
• The impoundment operates under steady-state, well-mixed conditions
(continuously stirred tank reactor (CSTR)). In a CSTR, the unit is assumed to be
perfectly (or completely) mixed so that the concentration within the unit is at all
times homogeneous and equal to the effluent concentration. Constituent in the
influent waste stream is assumed to be instantaneously and evenly distributed
within the unit. This modeling assumption is generally appropriate when aeration
or mechanical mixing is present. It may also be generally applicable for certain
nonaerated units whose general dimensions and orientation to prevailing winds
afford significant mixing from eddy currents. An alternate model construct is the
plug-flow model, which is roughly equivalent to a batch reactor. In a plug-flow
system, essentially no mixing is assumed. This scenario is most appropriate for
units that are quiescent and whose dimensions and orientation to prevailing winds
limit wind-caused mixing (e.g., a very narrow, long, slow-moving stream). In
reality, both model constructs are imperfect. Complete mixing or absolutely no
mixing is never achieved. For IWAIR, it was determined that the complete
mixing model construct was generally the most applicable; it was therefore used
for IWAIR. Consequently, the predicted emissions for aqueous-phase wastes are
most accurate for well-mixed units and are less accurate when little or no mixing
(i.e., plug-flow) is present.
• Hydrolysis rate is first order with respect to constituent concentrations.
• By default, aqueous waste constituent biodegradation is modeled as first order
with respect to biomass concentrations and follows Monod kinetics with respect
to constituent concentrations (see discussion of the biodegradation rate constants
K, and Kmax in Section 2.3.1). Because the Monod kinetic model is nonlinear with
respect to the constituent concentration, waste influent concentration is calculated
using an iterative approach (using a Newton-Raphson routine) for the
concentration calculation mode or is user-specified for the risk calculation mode.
The surface area, depth, flow rate, and aeration parameters (if applicable) are all
2-36
-------
IWAIR Technical Background Document Section 2.0
directly specified for the model unit. See Section 6.2.2 for further discussion of
the Newton-Raphson method.
In addition to constituent biodegradation, growth of biomass occurs in
biologically active surface impoundments, which provides a growing matrix for
chemical adsorption and loss through settling. Adsorption and settling losses also
occur in the absence of active biomass and biodegradation, but are limited to
occurring on inlet solids. Biodegradation cannot occur if there is no active
biomass. If an impoundment is biologically active, it may go through a
transitional period during which there is active biomass (so biomass growth
occurs, facilitating adsorption and settling losses) but the biomass is not yet
adapted to consume the specific chemicals present (so biodegradation does not
occur). This transitional period will usually end as the biomass acclimates and
adapts to the chemicals present.
The user can control these two processes (biodegradation and adsorption losses)
separately. Setting biodegradation to |OFF| turns off biodegradation, but does not
affect adsorption loss. Setting active biomass to zero turns off biomass growth, so
that adsorption losses are limited to adsorption to inlet solids. Because
biodegradation cannot occur in the absence of active biomass, setting active
biomass to zero also effectively turns off biodegradation.
For organic-phase wastes (which can be modeled only for nonaerated impoundments),
assumptions include
• The impoundment is assumed to operate under steady-state, plug-flow (no
mixing) conditions.
• There is no biodegradation or hydrolysis for organic-phase wastes.
• There is no adsorption modeled for organic-phase wastes.
The equations for surface impoundments are presented in the following five sections:
Section 2.4.4.1, Quiescent Surface Impoundments for Aqueous-Phase Wastes; Section 2.4.4.2,
Quiescent Surface Impoundments for Organic-Phase Wastes; Section 2.4.4.3, Mechanically
Aerated Surface Impoundments (Aqueous-Phase Wastes Only); Section 2.4.4.4, Diffused Air
Aerated Surface Impoundments (Aqueous-Phase Wastes Only); and Section 2.4.4.5, Both
Mechanically and Diffused Air Aerated Surface Impoundments (Aqueous-Phase Wastes Only).
2.4.4.1 Quiescent Surface Impoundments for Aqueous-Phase Wastes
Calculation of the liquid-phase mass transfer coefficient for quiescent surface
impoundments (CHEMDAT8V The appropriate correlation to use to estimate the liquid-phase
mass transfer coefficient for quiescent surface impoundments is dependent on the wind speed and
the fetch-to-depth ratio of the impoundment. The fetch is the linear distance across the WMU,
and it is calculated from the WMU's surface area assuming a circular shape for the WMU. That
is,
2^37
-------
IWAIR Technical Background Document
Section 2.0
F =
4 A
,0.5
(2-38)
where
F = fetch of the unit (m)
A = surface area of the unit (m2).
For wind speeds less than 3.25 m/s, the following correlation is used to calculate the
liquid-phase mass transfer coefficient for quiescent surface impoundments regardless of the
fetch-to-depth ratio:
k1>q = 2.78 x 10-6 Tc>liq
"^^
D
ether
(2-39)
where
T
c,liq
T
D
D
ether
liquid-phase mass transfer coefficient for quiescent surface impoundments
(m/s)
temperature correction factor for liquid-phase mass transfer coefficients
(unitless) = (T/298.15)
temperature of system (°K)
diffusivity of constituent in water (cm2/s)
diffusivity of ether in water (8.5E-6 cm2/s).
For wind speeds greater than or equal to 3.25 m/s, the appropriate correlation for the
liquid-phase mass transfer coefficient for quiescent surface impoundments is dependent on the
fetch-to-depth ratio (F/dliq) as follows:
For — < 14,
<**
ku =
SCjjq '
(2-40)
For 14
51.2,
= T
cjiq
2.605 x 1Q-9 — + 1.277 x 10'7
^^
ether
(2-41)
2-38
-------
IWAIR Technical Background Document Section 2.0
For — > 51.2,
k1>q = 2.611 x 10- ' °-
Aether
(2-42)
where
dliq = depth of liquid in the surface impoundments (m)
a = equation constant, a = 34.1 for U* > 0.3 m/s; a = 144 for U* < 0.3 m/s
U* = friction velocity (m/s) = 0.01U (6.1 + 0.63U)0'5
U10 = wind speed 10m above surface (m/s)
b = equation constant, b = 1 for U* > 0.3 m/s; b = 2.2 for U* < 0.3 m/s
Scliq = liquid-phase Schmidt number = |J.w/(pw Dw)
|j,w = viscosity of water (g/cm-s) = 9.37E-3 g/cm-s
pw = density of water (g/cm3) = 1 g/cm3.
Calculation of gas-phase mass transfer coefficient for quiescent surface
impoundments (CHEMDAT8V The gas-phase mass transfer coefficient for quiescent surface
impoundments is estimated as follows:
kg>q = (4.82 x 10-3) Tceas uo.78 Sc;o.67 F_o.ii (2.43)
where
kgq = gas-phase mass transfer coefficient for quiescent surface impoundments (m/s)
Tc,gas = temperature correction factor for gas diffusivity or gas mass transfer
coefficient (unitless) = (T / 298.15)1'75
T = temperature of system (°K)
Scg = gas-phase Schmidt number = |J.a/(pa Da)
pa = density of air (g/cm3) = 1.2E-3 g/cm3
|j,a = viscosity of gas (air) (g/cm-s) = 1.81E-4 g/cm-s
Da = diffusivity of constituent in air (cm2/s).
Calculation of overall mass transfer coefficient for quiescent surface impoundments
for (CHEMDAT8V For aqueous wastes, the overall mass transfer coefficient that determines
the rate of volatilization is determined based on a two-resistance model: a liquid-phase mass
transfer resistance and a gas-phase mass transfer resistance. The overall volatilization mass
transfer coefficient for quiescent surface impoundments is calculated as follows:
I i i V1
KOL = KOL,, = IT" + TT^— (2-44)
2-39
-------
IWAIR Technical Background Document Section 2. 0
where
KOL = overall volatilization mass transfer coefficient (m/s)
KOLq = overall mass transfer coefficient for quiescent surface impoundments (m/s)
Keq = vapor-liquid equilibrium coefficient for constituent (g/cm3 per g/cm3).
Generally, Henry's law is used to estimate the vapor-liquid equilibrium coefficient for
aqueous systems. The only exception to this is when the constituent is present within the surface
impoundments at concentrations above the aqueous solubility. As the aqueous solubility is
determined for binary systems (i.e., the constituent in pure water), a chemical's solubility in the
waste matrix within the surface impoundments may be quite different than its solubility in pure
water. However, Henry's law applies to dilute solutions. The aqueous solubility is used as an
indication of whether or not the solution is "dilute" for a given chemical. As the steady-state
concentration within the impoundment has not been calculated and cannot be calculated without
first estimating the overall mass transfer coefficient, the vapor-liquid equilibrium coefficient is
calculated based on Henry's law as follows:
(2-45)
where
Tcorr = temperature correction factor for vapor pressure for constituent (unitless) (see
Equation 2-16)
H = Henry's law constant at 25°C (atm-m3/mol)
R = universal gas constant = 8.21E-5 m3-atm/mol-°K
T = temperature of the system (°K).
If the concentration within the impoundment exceeds the aqueous solubility for a given
constituent based on the initial Henry's law assumption, then the vapor-liquid equilibrium
partition coefficient for that chemical is recalculated using Raoult's law as follows:
T p / i o
= corr vap _LS
eq RT (\06
where
Pvap = vapor pressure of constituent at 25°C (atm)
T = temperature of the system (°K)
18 = unit conversion factor for aqueous waste (cm3/mol = 18 g/mol x 1 cm3/g)
106 = unit conversion factor (cm3/m3).
Calculation of adsorption rate constant (CHEMDAT8) Sorption onto solids within
the surface impoundment is a competing removal mechanism to the volatilization loss. The
sorption removal rate depends on the rate at which solids enter and/or are produced within the
surface impoundment and the solids-liquid partition coefficient. Solids production within the
2^40
-------
IWAIR Technical Background Document Section 2.0
surface impoundment is dependent on either the available degradable organic matter entering the
surface impoundments or the maximum overall biodegradation rate of this organic matter. The
solids "wasting" rate (rTSS) is the total rate at which solids enter the surface impoundment plus the
rate of solids production within the surface impoundment, and it is calculated as follows:
rTSS = 1000TSSmQ+0.5xmmf ^1.0462x(T-298)dliqAX;CTOCQj (2-47)
where
rTSS = total solids wasting rate (g solids/s)
1000 = unit conversion factor (L/m3)
TSSin = total suspended solids in influent (g/L)
Q = influent flow rate (m3/s)
0.5 = assumed biomass yield coefficient (g solids/g organic consumed)
min() = function that returns the minimum value of a series of numbers separated by
semicolons
rb,tot = biodegradation rate for total organics (mg/g-hr)
3600 = unit conversion (s/hr)
0.001 = unit conversion (g/mg)
T = temperature (°K)
X = active biomass concentration in the surface impoundment (g/L)
CTOC = concentration of total organics in the surface impoundment influent (mg/L) =
g/m3.
It is assumed that the sludge is 99 percent water by weight and 1 percent solids by weight
and that the sludge has a density essentially that of water (i.e., 1 g/cm3). The sludge-liquid
partition coefficient, therefore, adjusts the solid-liquid partition coefficient as follows:
Ks = 0.99 + 0.0 lKd (2-48)
where
Ks = sludge-liquid partition coefficient (g/cm3 sludge per g/cm3 waste)
Kd = solid-liquid partition coefficient (cm3/g solids).
For organic compounds, the following correlation is used to estimate the solid-liquid
partition coefficient using the constituent's octanol -water partition coefficient as follows:
where
Kow = octanol-water partition coefficient (unitless).
-------
IWAIR Technical Background Document Section 2. 0
For mercury, the solid-liquid partition coefficient (Kd) is directly input in place of the octanol-
water partition coefficient, and Equation 2-48 is used directly using this input value for Kd.
The adsorption rate constant is then calculated as
100K rTSS
where
Kads = adsorption rate constant (1/s)
100 = sludge solids correction factor, (100 g sludge/g solids) * (1 cm3/g sludge)
106 = units correction factor (cm3/m3).
Calculation of effluent concentration (CHEMDAT8) All aqueous surface
impoundments are modeled as well-mixed systems so that the concentration within the surface
impoundment is assumed to be the same as the effluent concentration. Because of the nonlinear
biodegradation rate model used for aqueous surface impoundments, the steady-state solution for
the effluent concentration (and concentration within the surface impoundment) requires the
solution of a quadratic equation, as follows:
2a
where
Chq = constituent concentration in the surface impoundment and in the effluent
(mg/L = g/m3)
a,b,c = quadratic equation terms, which are defined in the following equations:
Quadratic term a:
I K
a = -
1
where
a = — + 72k + Khyd+Kads (2-52)
res liq
tres = hydraulic residence time (s) = dUq x A/Q
Khyd = hydrolysis rate constant (1/s).
Quadratic term b:
<2-53)
2-42
-------
IWAIR Technical Background Document Section 2.0
where
Kmax = maximum biodegradation rate constant (mg/g-hr)
Kj = first-order biodegradation rate constant (g/L-hr)
T = temperature (°K)
3600 = units conversion factor (s/hr)
Cin = constituent concentration in surface impoundment influent (mg/L = g/m3)
Quadratic term c:
(K Yc "\
c = - —S£L — (2-54)
UJUJ
Calculation of fraction emitted (CHEMDAT8). The fraction emitted is the mass of
constituent volatilized per mass of constituent influent to the surface impoundment:
AKOLCliq
PL liq C7-55)
1 emitted /-«-*! ^ '
where
= fraction of constituent emitted to the atmosphere (unitless).
Calculation of fraction adsorbed (CHEMDAT8). The fraction adsorbed is the mass of
constituent adsorbed per mass of constituent influent to the surface impoundment:
_ A dliq Kads Qiq (
-"-adsorbed > \
where
= fraction of constituent adsorbed (unitless).
Calculation of emission flux rate (IWAIR). The emission flux rate is calculated as
follows:
f
E emitted
= '
A
where
E = emission flux rate of constituent (g/m2-s).
2-43
-------
IWAIR Technical Background Document Section 2.0
2.4.4.2 Quiescent Surface Impoundments for Organic-Phase Wastes.
Biodegradation, hydrolysis, and adsorption are not modeled for organic-phase wastes.
Calculation of gas-phase mass transfer coefficient for quiescent surface
impoundments (CHEMDAT8V The gas-phase mass transfer coefficient for quiescent surface
impoundments is estimated as follows:
kgq = (4.82 x 1(T3) TCjgas°'67 U°-78 Scg °'67 F-°-u (2-58)
where
T = temperature of system (°K).
Calculation of overall mass transfer coefficient for organic systems (CHEMDAT8).
For organic wastes, the liquid-phase mass transfer coefficient is assumed to be noncontrolling.
The liquid-phase mass transfer correlations presented previously for aqueous surface
impoundments assume the liquid is water, and these are not applicable to an impoundment
containing organic (i.e., nonaqueous) wastes. Consequently, the overall mass transfer coefficient
for organic systems is calculated based on the gas-phase mass transfer coefficient and the
equilibrium partition coefficient as follows:
Vorg = Keq kg,q (2-59)
where
KOLorg = overall mass transfer coefficient for organic waste (m/s).
The vapor-liquid equilibrium coefficient is calculated using Raoult's law similarly to the vapor-
liquid equilibrium coefficient for aqueous systems when Raoult's law is used (Equation 2-46),
except the unit conversion factor for aqueous waste is now calculated based on the organic waste
properties as follows:
ea T-» ^r ^i /-\6 ^ '
where
T = temperature of the system (°K)
MW = molecular weight of the organic waste (g/mol)
pliq = density of organic waste (g/cm3)
106 = unit conversion factor (cm3/m3).
2-44
-------
IWAIR Technical Background Document
Section 2.0
Calculation of fraction emitted (CHEMDAT8). There are no other loss mechanisms
for organic systems besides volatilization and the surface impoundment effluent. The fraction
emitted is calculated based on a plug-flow model solution as follows:
^emitted ~~
-AK,
OL,org
(2-61)
Calculation of emission flux rate (IWAIR). The emission flux rate is calculated as
follows:
f
emitted ^ in
(2-62)
2.4.4.3 Mechanically Aerated Surface Impoundments (Aqueous-Phase Wastes
Only). Mechanical aeration is effected by impellers or mixers that agitate the surface of
impoundment. Correlations are available to estimate the turbulent mass transfer coefficients for
these agitated surfaces based on the power input to the aerators, the impeller size, the rotation
speed, and so forth. These correlations are presented below. Although the agitated surface area
may extend well beyond the diameter of the aerator impeller, there is usually some portion of the
surface impoundment surface area that is not affected by the aerators and that remains quiescent.
The overall quiescent mass transfer coefficient for these areas is calculated exactly as it is for
quiescent impoundments (Equation 2-38 through Equation 2-46).
Note that organic-phase wastes cannot be modeled for aerated impoundments; the
CHEMDAT8 oily film model used to model organic-phase wastes in nonaerated surface
impoundments is not applicable to aerated impoundments, as the aeration breaks up the organic
film modeled.
Calculation of the liquid-phase mass transfer coefficient for turbulent surface
impoundments (CHEMDAT8V The liquid-phase mass transfer coefficient for turbulent surface
impoundments is calculated as
k,,t =
Lc,liq
8.22X1Q-3 J Ptot 1.024(T-20) Ocf MWw
10.76 A. p,
D
D
O2,w
0.5
(2-63)
where
J
Pt,
liquid-phase mass transfer coefficient for turbulent surface impoundments
(m/s)
oxygen transfer rate (Ib O2/h-hp)
total power to the impellers (hp)
liquid temperature in WMU (°C)
2-45
-------
IWAIR Technical Background Document Section 2.0
Ocf = oxygen correction factor5 (unitless)
MWW = molecular weight of water (g/mol) =18 g/mol
A, = surface area for affected by the aeration (i.e., turbulent) (m2) = A x faer
A = surface area of surface impoundment (m2)
faer = fraction of total surface impoundment surface area affected by aeration
(unitless)
D02W = diffusivity of oxygen in water (cm2/s) = 2.4E-5 cm2/s.
Calculation of the gas-phase mass transfer coefficient for turbulent surface
impoundments (CHEMDAT8). The gas-phase mass transfer coefficient for turbulent surface
impoundments is calculated as
kgt = 1.35 x ID'7 Tcgas RegL42 p°-4 Scg°-5 Fr'0-21 DaMWa d^ (2-64)
where
kgt = gas-phase mass transfer coefficient for turbulent surface areas (m/s)
Reg = gas-phase Reynolds number = (dimp2 w pa)/|ig
p = power number = 0.85 (550 Ptot/Naer) gc / [(62.428pw )w3 (dimp/30.48)5 ]
gc = gravitational constant = 32.17 Ibm-ft/s2-lbf
Naer = number of aerators
w = rotational speed (rad/s)
Fr = Froud number = [w2 (dimp/30.48) ]/ gc
MWa = molecular weight of air (g/mol) = 29 g/mol
dimp = impeller diameter (cm).
Calculation of the overall turbulent surface mass transfer coefficient
(CHEMDAT8). The overall turbulent surface mass transfer coefficient is calculated based on the
two-resistance module as follows:
(2-65)
where
K0L,t = overall turbulent surface mass transfer coefficient (m/s).
5 CHEMDAT8 misnames this input power efficiency. The actual power efficiency, used in the equation for
gas-phase turbulent mass transfer coefficient, is hardwired to a value of 0.85 in CHEMDAT8 (see the equation for
power number in the list of parameters for Equation 2-64). In order to maintain consistency with CHEMDAT8,
IWAIR also terms this input power efficiency and hardwires the real "power efficiency" with a value of 0.85. The
default value provided in the IWAIR model and the parameter guidance provided in Appendix B of the IWAIR
User's Guide for this input are consistent with its use as the oxygen correction factor.
2^46
-------
IWAIR Technical Background Document Section 2. 0
The vapor-liquid partition coefficient is calculated using Equation 2-45 (based on Henry's law)
for the initial calculation of the constituent concentration within the surface impoundment. If the
constituent concentration within the surface impoundment exceeds the aqueous solubility limit,
then the overall mass transfer coefficients are re-calculated using Equation 2-46 for the vapor-
liquid partition coefficient (based on Raoult's law).
Calculation of the overall volatilization mass transfer coefficient (CHEMDAT8V The
overall volatilization mass transfer coefficient is calculated based on an area-weighted average as
follows:
(2.66)
where
= overall mass transfer coefficient for quiescent surface areas (m/s)
Aq = quiescent surface area = (1 -faer) A (m ) (Note: A, + Aq must equal A).
Calculation of emission flux rates (IWAIR). Once the overall mass transfer coefficient
is calculated, the calculations of the adsorption rate coefficient, effluent constituent
concentration, fraction emitted, fraction adsorbed, and emission flux rates follow the equations
presented for quiescent, aqueous surface impoundments (Equations 2-47 through Equation 2-57).
2.4.4.4 Diffused Air Aerated Surface Impoundments (Aqueous-Phase Wastes Only).
Diffused air aeration is effected by blowing air through diffusers or spargers located below the
liquid surface (typically near the bottom of the impoundment) and allowing the air bubbles to rise
through the liquid to the liquid surface. The rising air bubbles are assumed to come into
equilibrium with the liquid so that the diffused air acts to "strip" volatiles from the
impoundment. Additionally, the rising bubbles tend to agitate and mix the air-liquid interface,
increasing the mass transfer (or creating turbulence) between the air and liquid. No correlations
have been developed to estimate the "turbulent" mass transfer coefficients when the turbulence is
caused by diffused air aeration; therefore, IWAIR assigns "virtual mechanical aerators" to use as
inputs for calculating the overall mass transfer coefficient for the turbulent surfaces following the
procedures described for mechanically aerated surface impoundments. Again, there is usually
some portion of the surface impoundment surface area that is not affected by the aeration and that
remains quiescent. The overall quiescent mass transfer coefficient for these areas is calculated
exactly as it is for quiescent, aqueous impoundments (Equation 2-38 through Equation 2-46).
Organic-phase wastes cannot be modeled for aerated impoundments; the CHEMDAT8
oily film model used to model organic-phase wastes in nonaerated surface impoundments is not
applicable to aerated impoundments, as the aeration breaks up the organic film modeled.
Calculation of emission rate constant for diffused air (CHEMDAT8). The emission
rate caused by the "stripping" action of the bubbles rising through the wastewater is calculated
assuming that all of the diffused air comes into equilibrium with the wastewater. An effective
first-order emission rate constant is calculated for the diffused air constituent loss as
2^47
-------
IWAIR Technical Background Document Section 2.0
KnQri,
diff ~ ~A A~~ (2-67)
QliqA
where
Kdiff = emission rate constant for diffused air (1/s)
Qair = diffused air flow rate (m3/s).
Again, the vapor-liquid equilibrium partition coefficient is calculated using Equation 2-45 (based
on Henry's law) for the initial calculation of the constituent concentration within the surface
impoundment. If the constituent concentration within the surface impoundment exceeds the
aqueous solubility limit, then the overall mass transfer coefficients are re-calculated using
Equation 2-46 for the vapor-liquid partition coefficient (based on Raoult's law).
Calculation of "virtual mechanical aerator" parameters (IWAIR). Diffused air
agitates the liquid surface, causing an increased emission rate. This effect is modeled by
selecting "virtual mechanical aerator" parameter inputs to be used in calculating the overall
turbulent surface area mass transfer coefficient. The algorithms used to calculate the "virtual
mechanical aerator" parameters for the diffused-air-only surface impoundments are designed to
model a "low" degree of surface turbulence caused by the diffused aeration. If the diffused air
system creates a high degree of surface turbulence, the user could develop alternative mechanical
aerator inputs and model the unit using the BOTH (DIFFUSED AIR a MECHANICAL) option.
The factor that controls the parameters selected for the virtual mechanical aerator is the
turbulent surface area (total surface impoundment area x fraction agitated). Thus, the fraction-
agitated parameter for diffused-air-only surface impoundments has a direct impact on the fraction
of the surface area to which the overall turbulent mass transfer coefficient is applied, and to a
lesser degree, the actual value of the turbulent mass transfer coefficient.
It is assumed that 10 m2 of surface turbulence is generated per horsepower of a typical
aerator. The Treatment Storage and Disposal Facility (TSDF) survey (U.S. EPA, 1991) provides
data on several model units with mechanical aerators, including total aerator power and turbulent
surface area. The values for turbulent surface area per hp for these model units ranges from 3 to
8.4 m2/hp. These units reflect real mechanical aerators; diffused air aerators would typically
produce less turbulence over a greater area, so a greater turbulent area per hp is desired for the
virtual aerators. Thibodeux (1976) provides a range of 0.11 to 20.1 m2/hp that is typical for
mechanically aerated systems. Therefore, a value of 10 m2/hp was selected as greater than the
TSDF reported values and roughly the midpoint of the Thibodeux range. The total power input
for the virtual mechanical aerator is then calculated as
Af
ax
10
p = —SSL. (2-68)
tot - ^ ^ /
2-48
-------
IWAIR Technical Background Document Section 2. 0
where
Ptot = total power to the impellers (hp)
10 = assumed area of agitation per horsepower applied to aerator (m2/hp).
It is also assumed that the horsepower of a single aerator is not to exceed 15 hp, and the
number of aerators should be a whole number. Consequently, the number of aerators is
calculated as follows:
(2-69)
where
roundQ = function that rounds the value to the nearest integer
15 = assumed maximum horsepower of an aerator (hp/aerator)
0.5 = value used to make the roundQ function round up to the next highest integer.
All other aerator parameters (impeller diameter, impeller speed, oxygen transfer rate, and
power efficiency) are selected based on the IWAIR default values for these parameters.
Calculation of the overall volatilization mass transfer coefficient (CHEMDAT8V The
overall volatilization mass transfer coefficient is calculated as an area-weighted average of the
overall quiescent surface area and turbulent surface area mass transfer coefficients (Equation 2-
66). These quiescent surface and turbulent surface mass transfer coefficients are calculated as
described in Sections 2 A A.I and 2 A A3, respectively.
Calculation of effluent concentration (CHEMDAT8). The effluent concentration (and
the concentration within the surface impoundment) is calculated using Equation 2-51, but the
quadratic term a includes the emission rate constant for diffused air as follows:
Quadratic term a for systems with diffused air:
a = —+ -T^+ Khyd + Kads + Kdff (2-70)
res liq
The equation for the quadratic term b remains unchanged, but it includes the quadratic term a
within its equation, so that the value of the quadratic term b term is dependent on the diffused air
rate constant (Kdiff).
Calculation of emission flux rates (IWAIR). The remainder of the calculations
(fraction emitted, fraction adsorbed, and emission flux rates) follow the equations presented for
quiescent, aqueous surface impoundments (Equations 2-55 through Equation 2-57).
2-49
-------
IWAIR Technical Background Document Section 2.0
2.4.4.5 Both Mechanically and Diffused Air Aerated Surface Impoundments
(Aqueous-Phase Wastes Only). Some surface impoundments operate both mechanical aerators
and diffused air aeration. These aerators may be used in separate areas of the surface
impoundment, or the mechanical aerators may operate above the diffused air aeration (i.e.,
mechanically agitating the area where the diffused air bubbles are reaching the liquid surface).
This system is modeled exactly like the diffused aeration system, except that the mechanical
aerator inputs provided by the user are used rather than the values imputed for the "virtual
mechanical aerator." As such, the IWAIR solution is most applicable for surface impoundments
with mechanical aerators placed above the diffused air aeration or for surface impoundments
where the degree of turbulence and or the area affected by the diffused air aeration is small in
comparison to the mechanically agitated surface. In these cases, the area affected by the
mechanical aeration can be used directly to estimate the fraction agitated input parameter (faer).
The equations used to calculate the emissions from the both mechanical and diffused air
aerated surface impoundments follow the method used for diffused-air-only surface
impoundments presented in Section 2.4.4 A (without the need to calculate "virtual mechanical
aerator" parameters).
Note that organic-phase wastes cannot be modeled for aerated impoundments; the
CHEMDAT8 oily film model used to model organic-phase wastes in nonaerated surface
impoundments is not applicable to aerated impoundments, as the aeration breaks up the organic
film modeled.
2-50
-------
IWAIR Technical Background Document Section 3.0
3.0 Development of Dispersion Factors Using
ISCST3
In assessing the potential risk from an emissions source, one of the properties that must
be evaluated is the ability of the atmosphere in the local area to disperse the chemicals emitted.
When a chemical is emitted, the resulting plume moves away from the source and begins to
spread both horizontally and vertically at a rate that is dependant on local atmospheric
conditions. The more the plume spreads (i.e., disperses), the lower the concentration of the
emitted chemicals will be in the ambient air. Dispersion models are designed to integrate
meteorological information into a series of mathematical equations to determine where the
material travels after release and how fast the material is ultimately removed from the
atmosphere.
IWAIR uses dispersion factors to relate an emission rate to an air concentration at some
specified location. A dispersion factor is essentially a measure of the amount of dispersion that
occurs from a unit of emission. Dispersion modeling is complex and requires an extensive data
set; therefore, the IWAIR model has incorporated a database of dispersion factors. For IWAIR,
dispersion was modeled using a standardized unit emission rate (1 |j,g/m2-s) to obtain the air
concentration (referred to as a dispersion factor) at a specific point away from the emission
source. The unit of measure of the dispersion factor is H-g/m3 per |o,g/m2-s. The most important
inputs to dispersion modeling are the emission rate, meteorological data, the area of the WMU,
the height of the WMU relative to the surrounding terrain, and the location of the receptor
relative to the WMU. The default dispersion factors in IWAIR were developed for many
separate scenarios designed to cover a broad range of unit characteristics, including
• 60 meteorological stations, chosen to represent the different climatic and
geographical regions of the contiguous 48 states, Hawaii, Puerto Rico, and parts
of Alaska;
• 4 unit types;
• 17 surface areas for landfills, land application units, and surface impoundments,
and 11 surface areas and 7 heights for waste piles;
• 6 receptor distances from the unit (25, 50, 75, 150, 500, 1,000 meters); and
• 16 directions in relation to the edge of the unit (only the maximum direction is
used).
5-1
-------
IWAIR Technical Background Document Section 3.0
The default dispersion factors were derived by modeling many scenarios with various
combinations of parameters, then choosing as the default the maximum dispersion factor for each
WMU/surface area/height/meteorological station/receptor distance combination.
Based on the size and location of a unit, as specified by the user, IWAIR selects an
appropriate dispersion factor from the default dispersion factors in the model. If the user
specifies a unit surface area or height that falls between two of the sizes already modeled, IWAIR
used an interpolation method to estimate a dispersion factor based on the two closest model unit
sizes.
The ISCST3 dispersion model (U.S. EPA, 1995) was selected to develop the dispersion
factors in IWAIR. ISCST3 was chosen because it can provide reasonably accurate dispersion
estimates for both ground-level and elevated area sources. Section 3.1 describes the development
of the dispersion factor database used in IWAIR. Section 3.2 describes the interpolation method.
3.1 Development of Dispersion Factor Database
Figure 3-1 summarizes the process by which the dispersion factor database was
developed. Each step is described in the following subsections.
3.1.1 Identify WMU Areas and Heights for Dispersion Modeling (Step 1)
Area and height aboveground of a WMU are two of the most sensitive parameters in
dispersion modeling. To construct a database that contains benchmark dispersion coefficients, an
appropriate set of "model" units to run had to be determined. This set of areas and heights was
chosen to cover a range of realistic unit areas and heights and to have a high probability of
achieving interpolation errors less than about 5 percent.
Land application units, landfills, and surface impoundments are all ground-level sources
and are modeled the same way using ISCST3. However, waste piles are elevated sources and
must be modeled separately in ISCST3. Therefore, two sets of areas were developed, one for
ground-level sources (land application units, landfills, and surface impoundments), and one for
waste piles. In addition, a set of heights was developed for waste piles.1
The primary source of data used in the analysis for determining the appropriate range of
WMU areas to model was the Industrial D Screening Survey responses (Schroeder et al., 1987).
These survey data provide information on the distribution of areas of nonhazardous WMUs
across the contiguous 48 states. As a starting point to determine how many and what areas might
be needed to adequately cover the reported range, EPA used a statistical method called the
Dalenius-Hodges procedure to develop area strata from the Industrial D survey data. This
method attempts to break down the distribution of a known variable (in this case, area) that is
assumed to be highly correlated with the model output (in this case, dispersion factor) into a
1 This important distinction in the dispersion modeling between ground-level sources and elevated sources
makes the use of the IWAIR surface impoundment component inappropriate to modeling tanks, which are usually
elevated.
O O
3-2
-------
IWAIR Technical Background Document
Section 3.0
STEP1
Identify WMU areas and heights
for dispersion modeling
STEP 2
STEP 3
Select receptor locations for
dispersion modeling
Identify meteorological
stations for dispersion
modeling
STEP 4
Conduct dispersion modeling
using Industrial Source
Complex Short-Term Model
(ISCST3)
Screening Survey of
Industrial Subtitle D
Establishments
(Shroeder et al., 1987)
Receptor distances used
to generate dispersion
factors: 25, 50,75,150,
500,1,000 meters
STEPS
Select dispersion factors to
populate IWAIR database
Dispersion factors are
calculated for each of the
60 met. stations and for
each receptor distance
Figure 3-1. Development of dispersion factor database.
fixed number of strata in an optimal way. An area near the midpoint (in this case, the median)
for each stratum is then used to represent that stratum.
No data were available on waste pile height. Best professional judgement suggested a
realistic range from 1 to 10 m. (For comparison, 10 m is about the height of a 3-story building.)
Within this range, seven heights were selected at 1 to 2 m intervals, with smaller intervals at
lower heights.
To determine the adequacy of this initial set of areas and heights in achieving the goal of
less than 5 percent interpolation error, EPA examined graphical plots of interpolation errors
using one- or two-dimensional linear interpolation. These interpolation error plots were
generated for three meteorological stations: Fresno, California; Minneapolis, Minnesota; and Salt
Lake City, Utah. These stations were chosen to include a range of different wind roses and
climate regimes to determine whether the interpolation errors differed significantly based on
these factors. Very similar data patterns were seen for these three stations; therefore, EPA felt
that further investigation of potential variations by meteorological station was not needed. The
steps taken to generate the error plots were as follows:
5-3
-------
IWAIR Technical Background Document Section 3. 0
1. For each of the three sample meteorological stations, run ISCST3 to generate
outputs at a set of areas (for ground-level sources) or areas/heights (for waste
piles) that represent midpoints between the initial sets of areas and heights. (The
midpoints are the points at which error should be the largest.) These ISCST3
outputs represent the "true" outputs for purposes of calculating interpolation
errors.
2. For each of the area or area/height midpoints, apply the interpolation algorithm
(the interpolation algorithm is discussed in Section 3.2) to estimate the ISCST3
output value.
3. Compute the percentage interpolation error, defined as
("true" value - interpolated value)
-
("true" value)
(3-1 i
{ }
The error plots using the initial set of areas and heights suggested that additional areas
were needed in specific parts of the distribution. Therefore, three areas were added to the set for
ground-level sources, and four areas were added to the set for waste piles. A new error plot
indicated that this succeeded in reducing the interpolation errors for ground-level sources to
within the 5 percent goal using linear interpolation. Errors for waste piles were still as high as
about 15 percent, exceeding the 5 percent goal. However, generating data for additional surface
areas and heights is only one technique for reducing interpolation errors. Another way to reduce
interpolation errors is to choose a more sophisticated interpolation method. This approach was
taken for waste piles (and is discussed in Section 3.2), and no further additional areas were added
for waste piles.
Table 3-1 shows the final set of surface areas and heights selected for the IWAIR
dispersion database. Seventeen areas were modeled for ground-level sources, and 77
combinations of 1 1 areas and 7 heights were modeled for waste piles.
3.1.2 Select Receptor Locations for Dispersion Modeling (Step 2)
The ISCST3 model allows the user to specify receptors with a Cartesian receptor grid or a
polar receptor grid. In general, Cartesian receptor grids are used for near-source receptors and
polar receptor grids for more distant receptors. Because it takes a substantial amount of time for
the ISCST3 model to execute with a large number of receptor points, it was necessary to reduce
the number of receptors without missing representative outputs. Therefore, a sensitivity analysis
was conducted on area sources to determine the receptor locations and spacings (see Appendix C
for details).
The results of the sensitivity analysis of area sources show that the maximum impacts are
generally higher for a dense receptor grid (i.e., 64 or 32 receptors on each square) than for a
scattered receptor grid (i.e., 16 receptors on each square). For this application, however, the
differences in maximum receptor impacts are not significant between a dense and a scattered
5-4
-------
IWAIR Technical Background Document
Section 3.0
Table 3-1. Final Surface Areas and Heights
Used for ISCST3 Model Runs
Ground-Level Sources
Areas
K)
81
324
567
1551
4047
12,546
40,500
78,957
161,880
243,000
376,776
607,000
906,528
1,157,442
1,408,356
4,749,178
8,090,000
Waste Piles
Areas
(m2)
20
162
486
2100
6,100
10,100
55,550
101,000
500,667
900,333
1,300,000
Heights
(m)
1
2
4
5
6
8
10
receptor grid. Therefore, 16 evenly spaced receptor points on each square were used in the
modeling. The sensitivity analysis also shows that the maximum downwind concentrations
decrease sharply from the edge of the area source to about 1,000 meters from the source.
Therefore, receptor points were placed at 25, 50, 75, 150, 500, and 1,000 meters so that a user
could examine the areas most likely to have risks of concern.
Because the flat terrain option is used in the dispersion modeling, receptor elevations
were not considered.
5-5
-------
IWAIR Technical Background Document Section 3.0
3.1.3 Identify Meteorological Stations for Dispersion Modeling (Step 3)
Meteorological data at more than 200 meteorological stations in the United States are
available on the SCRAM Bulletin Board (http://www.epa.gov/scram001) and from a number of
other sources. Because of the time required to develop dispersion factors, it was not feasible to
include dispersion factors in IWAIR for all of these stations. Therefore, EPA developed an
approach to select a subset of these stations for use in IWAIR. This approach considers the
factors most important for the inhalation pathway risk modeling done by IWAIR.
The approach used involved two main steps:
1. Identify contiguous areas that are sufficiently similar with regard to the parameters
that affect dispersion that they can be reasonably represented by one
meteorological station. The parameters used were
• Surface-level meteorological data (e.g., wind patterns and atmospheric
stability)
• Physiographic features (e.g., mountains, plains)
• Bailey's ecoregions and subregions
• Land cover (e.g., forest, urban areas).
2. For each contiguous area, select one meteorological station to represent the area.
The station selection step considered the following parameters:
• Industrial activity
• Population density
• Location within the area
• Years of meteorological data available
• Average wind speed.
Appendix D describes the selection process in detail. Table 3-2 lists the 60 stations chosen;
Figure 3-2 shows the selected stations and their assigned regions for the contiguous 48 states.
Appendix D provides additional maps showing regions of the 48 states on a larger scale, as well
as Alaska and Hawaii.
Zip codes were overlaid on the regions, and a database matching zip codes to
meteorological stations was generated for use in IWAIR. In addition, latitudinal/longitudinal
coordinates of the polygons are used in IWAIR to select a meteorological station based on a
facility's latitudinal/longitudinal coordinates.
5-6
-------
IWAIR Technical Background Document
Section 3.0
Table 3-2. Surface-Level Meteorological Stations in
Station
Number
26451
25309
13963
23183
93193
23174
24257
23234
23062
14740
12839
12842
13874
03813
22521
94910
24131
94846
03937
12916
13957
14764
94847
14840
14922
13994
13865
24033
03812
13722
Station Name
Anchorage/WSMO Airport
Juneau/International Airport
Little Rock/ Adams Field
Phoenix/Sky Harbor International Airport
Fresno/Air Terminal
Los Angeles/International Airport
Redding/AAF
San Francisco/International Airport
Denver/Stapleton International Airport
Hartford/Bradley International Airport
Miami/International Airport
Tampa/International Airport
Atlanta/ Atlanta-Hartsfield International
Macon/Lewis B Wilson Airport
Honolulu/International Airport
Waterloo/Municipal Airport
Boise/Air Terminal
Chicago/O'Hare International Airport
Lake Charles/Municipal Airport
New Orleans/International Airport
Shreveport/Regional Airport
Portland/International Jetport
Detroit/Metropolitan Airport
Muskegon/County Airport
Minneapolis-St Paul/International Airport
St. Louis/Lambert International Airport
Meridian/Key Field
Billings/Logan International Airport
Asheville/Regional Airport
Raleigh/Raleigh-Durham Airport
IWAIR, by State
State
AK
AK
AR
AZ
CA
CA
CA
CA
CO
CT
FL
FL
GA
GA
HI
IA
ID
IL
LA
LA
LA
ME
MI
MI
MN
MO
MS
MT
NC
NC
(continued)
5-7
-------
IWAIR Technical Background Document
Section 3.0
Table 3-2. (continued)
Station
Number
24011
14935
23050
23169
24128
14820
93815
13968
94224
24232
14751
13739
14778
11641
13880
13877
13897
23047
13958
12924
03927
12960
23023
24127
13737
14742
24233
24157
03860
24089
Station Name
Bismarck/Municipal Airport
Grand Island/Airport
Albuquerque/International Airport
Las Vegas/McCarran International Airport
Winnemucca/WSO Airport
Cleveland/Hopkins International Airport
Dayton/International Airport
Tulsa/International Airport
Astoria/Clatsop County Airport
Salem/McNary Field
Harrisburg/Capital City Airport
Philadelphia/International Airport
Williamsport-Lycoming/County
San Juan/Isla Verde International Airport
Charleston/International Airport
Bristol/Tri City Airport
Nashville/Metro Airport
Amarillo/International Airport
Austin/Municipal Airport
Corpus Christi/International Airport
Dallas/Fort Worth/Regional Airport
Houston/Intercontinental Airport
Midland/Regional Air Terminal
Salt Lake City/International Airport
Norfolk/International Airport
Burlington/International Airport
Seattle/Seattle-Tacoma International
Spokane/International Airport
Huntington/Tri-State Airport
Casper/Natrona Co International Airport
State
ND
NE
NM
NV
NV
OH
OH
OK
OR
OR
PA
PA
PA
PR
SC
TN
TN
TX
TX
TX
TX
TX
TX
UT
VA
VT
WA
WA
WV
WY
-------
.,- ?y
-,5™!--"- ': 'PF
yjgpw ^£t
}»M*P
Figure 3-2. Meteorological stations and region boundaries for the contiguous 48 states.
-------
IWAIR Technical Background Document
Section 3.0
The modeling analysis was conducted
using 5 years of representative meteorological
data from each of the 60 meteorological
stations. Five-year wind roses representing the
frequency of wind directions and wind speeds
for the 60 meteorological stations were
analyzed. These show that the 60
meteorological stations represent a variety of
wind patterns.
Shape of Wind Rose for
60 Meteorological Stations
Shape of Wind Rose
Strongly directional
(>20% in 1 direction)
Moderately directional
(15-20% in 1 direction)
Mildly directional
(10-14% in 1 direction)
Weakly directional
(< 10% in 1 direction)
No. of
Stations
10
14
26
10
Wind direction and wind speed are
typically the most important meteorological
inputs for dispersion modeling analysis. Wind
direction determines the direction of the
greatest impacts (usually in the prevailing wind direction). For IWAIR, however, wind direction
is not important because only the direction of maximum air concentration is used. IWAIR
determines air concentration in 16 directions, and uses only the maximum of these; the actual
direction associated with that maximum is not retained. Wind speed is inversely proportional to
ground-level air concentrations, so that the lower the wind speed, the higher the air
concentration.
Mixing height determines the heights to which pollutants can be diffused vertically.
Stability class is also an important factor in determining the rate of lateral and vertical diffusion.
The more unstable the air, the greater the diffusion.
3.1.4 Conduct Dispersion Modeling Using Industrial Source Complex Short-Term Model,
Version 3 (Step 4)
This section discusses the critical
parameters of the selected model, ISCST3; the
results of sensitivity analyses performed to
investigate several of the model parameters;
and the receptor locations. Results of the
sensitivity analyses are presented in
Appendix C.
It is impossible to make a general
statement about whether IWAIR over- or
underestimates actual dispersion coefficients,
as this would depend completely on site-
specific factors. For some sites, it will
overestimate, and for others, underestimate.
Because the dispersion assumptions built into
IWAIR may not be applicable to all sites,
IWAIR was programmed to accommodate
Key Meteorological Data for
the ISCST3 Model without Depletion
Wind direction determines the direction of the
greatest impacts.
Wind speed is inversely proportional to ground-level
air concentration, so the lower the wind speed, the
higher the concentration.
Stability class influences rate of lateral and vertical
diffusion. The more unstable the air, the lower the
concentration.
Mixing height determines the maximum height to
which emissions can disperse vertically. The lower
the mixing height, the higher the concentration.
5-10
-------
IWAIR Technical Background Document
Section 3.0
user-entered dispersion factors that are a more accurate reflection of the site-specific conditions
prevailing at the user's site, if these are available.
3.1.4.1 General Assumptions. This
section discusses depletion, rural versus urban
mode, and terrain assumptions.
Depletion. ISCST3 can calculate
vapor air concentrations with or without wet
and dry depletion of vapors. Modeled
concentrations without depletion are higher
than those with depletion. The dispersion
factors for IWAIR were modeled without wet
or dry depletion of vapors.
ISCST3 can model dry depletion of
vapors only as a chemical-specific process. By
contrast, ISCST3 can model wet depletion of
vapors as non-chemical-specific process.
Thus, vapor air concentrations modeled
without depletion or with only wet depletion of
vapors can be used for any chemical; vapor air
concentrations modeled with dry depletion of
vapors are chemical-specific and must be
modeled separately for each chemical of
interest.
Assumptions Made for Dispersion Modeling
Dry and wet depletion options were not activated
in the dispersion modeling.
The rural option was used in the dispersion
modeling because the types of WMUs being
assessed are typically in nonurban areas.
Flat terrain was assumed.
An area source was modeled for all WMUs.
To minimize error due to site orientation, a
square area source with sides parallel to x- andy-
axes was modeled.
Receptor points were placed on 25, 50, 75, 150,
500, and 1,000 m receptor squares starting from
the edge of the source, with 16 receptor points
on each square.
Modeling was conducted using a unit emission
rate of 1 ug/nf-s.
Generating chemical-specific dispersion factors that included dry depletion of vapors
would have significantly limited the number of meteorological stations and WMU areas and
heights that could be included in IWAIR. Dry depletion of vapors is expected to have a
relatively small impact on vapor air concentration; by contrast, the differences in air
concentration between different areas and different meteorological stations are considerably
greater. Thus, dry depletion of vapors was not modeled, in order to include a greater number of
more generally applicable dispersion factors.
A sensitivity analysis showed that the differences in the maximum concentrations with
wet depletion and without wet depletion are very small, even for a wet location (less than 0.4
percent). The sensitivity analysis also shows that the run time for calculating concentrations
using the ISCST3 model with wet depletion is 15 to 30 times longer than the run time without
wet depletion for the 5th and 95th percentile of the sizes of land application units. (The difference
is greater for larger sources.) Therefore, concentrations were calculated without wet depletion in
this analysis so that a greater number of meteorological locations could be modeled and included
in IWAIR.
Rural versus Urban Mode. ISCST3 may be run in rural or urban mode, depending on
land use within a 3 km radius from the source. These modes differ with respect to wind profile
3-11
-------
IWAIR Technical Background Document Section 3.0
exponent and potential temperature gradients. Unless the site is located in a heavily metropolitan
area, the rural option is generally more appropriate. Because the types of WMUs being assessed
are typically in nonurban areas, the rural option was used to develop dispersion factors for
IWAIR.
Terrain. Flat terrain for both the source and the surrounding area was assumed in the
modeling analysis for two reasons: (1) ISCST3 can only model flat terrain for area sources,2 and
(2) complex terrain simulations in the surrounding area result in air concentrations that are highly
dependent on site-specific topography. A specific WMU's location in relation to a hill or valley
produces results that would not be applicable to other locations. Complex terrain applications
are extremely site-specific; therefore, model calculations from one particular complex terrain
location cannot be applied to another. Conversely, simulations from flat terrain produce values
that are more universally applicable.
3.1.4.2 Source Release Parameters. This section describes the source parameters and
assumptions used in the dispersion modeling, including source type and elevation, and source
shape and orientation.
Source Type and Elevation. ISCST3 can model three different types of sources: point,
area, and volume. All WMU types modeled in this analysis were modeled as area sources.
Landfills, land application units, and surface impoundments were modeled as ground-level
sources, and waste piles were modeled as elevated sources.
Source Shape and Orientation. The shape of WMUs facilities and their orientation to
the wind affect dispersion. However, in developing generally applicable dispersion factors for
use in a screening model, it was necessary to make some assumptions about shape and
orientation. A square shape was chosen for the general dispersion factors in IWAIR to minimize
the errors caused by source shape and orientation.
A sensitivity analysis was conducted to compare the air concentrations from a square area
source, a rectangular area source oriented east to west, and a rectangular area source oriented
north to south to determine what role source shape and orientation play in determining dispersion
coefficients of air pollutants. The results show that the differences in dispersion factors between
the square area source and the two rectangular area sources are smaller than the differences
between the two rectangular sources. In addition, a square area source has the least amount of
impact on orientation. Because information on source shapes or orientations is not available, a
square source was chosen to minimize the errors caused by source shapes and orientations (see
the sensitivity analysis in Appendix C for details).
ISCST3 can model three types of terrain for point sources: flat, simple, and complex (in simple terrain, the
terrain features are all below the centerline of the plume; in complex terrain, some terrain features are at or above the
centerline of the plume). However, for area sources, only flat terrain can be modeled. Typically, terrain
considerations are only important for buoyant emissions from stacks, where the plume is above ground level. In that
situation, terrain can affect where the plume reaches ground level, and it can significantly affect predicted ground-
level air concentrations. With area sources, the plume is already at ground level, so terrain (either simple or
complex) does not significantly affect ground-level air concentrations regardless of receptor distance.
-------
IWAIR Technical Background Document Section 3.0
3.1.5 Select Dispersion Factors to Populate IWAIR Database (Step 5)
Dispersion factors were calculated by running ISCST3 with a unit emission rate (i.e.,
1 |ig/m2-s). The selected areas for each type of WMU were modeled with 60 representative
meteorological locations in the United States using 5 years of meteorological data to estimate
dispersion factors. Annual average dispersion factors at all receptor points were calculated.
Typically, the location of maximum impacts with respect to the source is determined by
the prevailing wind direction. For each distance, the maximum dispersion factor of the 16
directions was used in the IWAIR database. For ground-level area sources (i.e., landfills, land
application units, and surface impoundments), maximum annual-average dispersion factors are
always located on the first receptor square (i.e., 25 m receptors). For elevated area sources (i.e.,
waste piles), the maximum annual-average dispersion factors are usually located on the first
receptor square and occasionally located on the second or third receptor square. However,
dispersion factors for all six distances are included in the IWAIR database. The annual-average
dispersion factors increase with the increasing area of the sources.
Maximum dispersion factors vary with meteorological location. For landfills, land
application units, and surface impoundments, the maximum dispersion factors at some
meteorological locations can be twice as high as those at other locations. For waste piles, the
maximum dispersion factors at some meteorological locations are more than twice those at other
meteorological locations.
3.2 Interpolation of Dispersion Factor
As described in Section 3.1, a set of areas and heights were identified for modeling
ground-level sources (land application units, landfills, and surface impoundments) and elevated
sources (waste piles), and these were modeled for 60 meteorological locations to produce a set of
dispersion factors at six receptor distances for use in IWAIR. Each dispersion factor is specific
to an area, height, meteorological location, and receptor distance.
This set of dispersion factors may not include a dispersion factor that exactly matches the
user's conditions. The user may be at a different meteorological location, have receptors located
at different distances, or have a unit of a different area and height. For meteorological location
and receptor distance, users must use one of IWAIR's 60 meteorological locations or six
distances (unless they enter their own dispersion factors); there will be some error associated
with this that cannot be reduced. The error associated with differences in the area and height of a
unit, however, may be reduced by interpolating between the dispersion factors contained in
IWAIR.
The simplest form of interpolation is a one-dimensional linear interpolation. A one-
dimensional linear interpolation would estimate a dispersion factor by adjusting for a single
variable (in this case, area) and assuming that dispersion factor is linear with that variable. This
is done as follows:
3-13
-------
IWAIR Technical Background Document Section 3.0
DF =
A -A.
x (DFj-DF;) + DF; (3-2)
where
DF = dispersion factor for specific WMU ([|J,g/m3]/[|j,g/m2-s])
A = area of specific WMU (m2)
Aj = area modeled in dispersion modeling immediately below area of specific
WMU (m2)
Aj = area modeled in dispersion modeling immediately above area of specific
WMU (m2)
DF; = dispersion factor developed for area / ([|j,g/m3]/[|j,g/m2-s])
= dispersion factor developed for areay ([|j,g/m3]/[|a,g/m2-s]).
Linear interpolation can also be two-dimensional to adjust for two variables (in this case, area
and height).3 Finally, nonlinear interpolation (both one- and two-dimensional) may be performed
if the output variable (dispersion factor) is not linear with the input variables (area and height).
For ground-level sources, EPA analyzed interpolation error using a one-dimensional
linear interpolation (see Section 3.1.1). This analysis indicated that interpolation errors of 5
percent or less could be achieved using linear interpolation on the areas identified in Table 3-1.
For waste piles, a similar analysis of interpolation errors using two-dimensional linear
interpolation indicated that a very large number of areas would have to be modeled to reduce
interpolation error to 5 percent using linear interpolation techniques. Therefore, EPA chose to
implement a two-dimensional spline approach instead. A spline is a nonlinear interpolation
technique that takes into account other points near the point of interest rather than just the two
adjacent ones (as in linear interpolation). A cubic spline was used in IWAIR. The equations for
implementing a spline are standard but complex; see, for example, Mathews (1992), Section 5.3,
for details. This approach tends to be more accurate because it accounts for the nonlinear nature
of the relationship between area or height and dispersion factor. However, it may behave
unpredictably, producing inaccurate results, especially near the edge of the surface (where it has
fewer nearby data points to work from) or where the gradient of the surface is steep (i.e.,
relatively large changes in dispersion factor occur for relatively small changes in area or height).
Repeating the error analysis using a two-dimensional spline indicated that interpolation errors of
5 percent or less could be achieved using the areas identified in Table 3-1.
However, as noted above, a spline can occasionally produce inaccurate results. As a
check on the spline method, EPA also included the two-dimensional linear interpolation
3 For a given area, A, and height, h, the algorithm first performs a one-dimensional linear interpolation on
height for the two available areas adjacent to A. From these two interpolated dispersion factors, another one-
dimensional linear interpolation is then performed in the area domain.
-------
IWAIR Technical Background Document Section 3.0
algorithm in the IWAIR code. The linear interpolation is known to underestimate dispersion
factors at all times; therefore, it provides a useful check on the spline. Thus, at an interpolated
point, both a spline interpolation and a two-dimensional linear interpolation are performed. In
general, the spline's estimate is preferred and used, but some tests (e.g., negative splined
concentration) and comparisons against the linearly interpolated value, as well as the values at
the surrounding four grid points, are made first. The linear interpolation value is used, and the
user notified of that fact, if the splined air concentration is
• less than or equal to zero,
• less than the linear interpolated value,
• less than the minimum of the four nearest points in the database, or
• greater than the maximum of the four nearest points in the database.
3-15
-------
-------
IWAIR Technical Background Document
Section 4.0
4.0 Exposure Factors
This section describes the development of the exposure factors used in IWAIR. These
factors are used in the risk equations documented in Section 6. All data in this section are from
the Exposure Factors Handbook (U.S. EPA, 1997'a; hereafter, the EFH). These exposure factors
are used only for carcinogenic chemicals (see box below for carcinogens included in IWAIR; the
user may add additional carcinogens). For noncarcinogens, the HQ is a ratio of air concentration
to the health benchmark (an RfC), and no exposure factors are used.
All exposure factors were developed for the following subpopulations:
Children aged <1 year
Children aged 1-5 years
Children aged 6-11 years
Children aged 12-18 years
Adult residents (aged 19 and older)
Workers.
The age ranges for children were selected for consistency with the data on inhalation rate
in the EFH. Most exposure factors were selected to represent typical or central tendency values,
not high-end values.
Acetaldehyde
Acrylamide
Acrylonitrile
Allyl chloride
Aniline
Benzene
Benzidine
Benzo(a)pyrene
Bromodichloromethane
Butadiene, 1,3-
Carbon tetrachloride
Chlorodibromomethane
Dibromo-3-chloropropane, 1,2-
Dichlorobenzene, p-
Dichloroethane, 1,2-
Dichloroethylene, 1,1-
Carcinogens Included in IWAIR
Dichloropropylene, cis-1,3-
Dichloropropylene, trans-1,3-
Dimethylbenz[a]anthracene, 7,12-
Dinitrotoluene, 2,4-
Dioxane, 1,4-
Diphenylhydrazine, 1,2-
Epichlorohydrin
Ethylbenzene
Ethylene dibromide
Ethylene oxide
Formaldehyde
Hexachloro-1,3 -butadiene
Hexachlorobenzene
Hexachloroethane
Methyl chloride (chloromethane)
Methylcholanthrene, 3-
Methylene chloride
Nitropropane, 2-
N-Nitrosodiethylamine
N-Nitro sodi-w -buty lamine
N-Nitrosopyrrolidine
Propylene oxide
TCDD, 2,3,7,8-
Tetrachloroethane, 1,1,1,2-
Tetrachloroethane, 1,1,2,2-
Tetrachloroethylene
Toluidine, o-
Tribromomethane
Trichloroethane, 1,1,2-
Trichloroethylene
Vinyl chloride
4-1
-------
IWAIR Technical Background Document
Section 4.0
Table 4-1 summarizes the exposure factors used in IWAIR. Sections 4.1 through 4.4
describe how the values for inhalation rate, body weight, exposure duration, and exposure
frequency, respectively, were determined.
Table 4-1. Summary of Exposure Factors Used in IWAIR
Receptor
Child <1
Child 1-5
Child 6-1 1
Child 12-18
Adult Resident
Worker
Inhalation
Rate
(m3/d)
4.5
7.55
11.75
14.0
13.3
10.4
Body
Weight
(kg)
9.1
15.4
30.8
57.2
69.1
71.8
Exposure
Duration
-------
IWAIR Technical Background Document
Section 4.0
Table 4-2. Recommended Inhalation Rates for Residents
Age (yr)
<1
1-2
3-5
6-8
9-11
12-14
15-18
Adults (19-65+)
Inhalation Rate (nrVd)
Males
NA
NA
NA
NA
14
15
17
15.2
Females
NA
NA
NA
NA
13
12
12
11.3
Males and Females
4.5
6.8
8.3
10
NA
NA
NA
NA
NA = Not available.
Source: U.S. EPA, 1997a, Table 5-23.
Table 4-3 summarizes the values for inhalation rate for workers presented in the EFH.
The recommended hourly average of 1.3 m3/h was used in IWAIR. To convert this to a daily
value, an 8 h workday was assumed, yielding a daily inhalation rate for workers of 10.4 nrVd.
This rate is lower than the adult resident average because it only accounts for 8 h/d instead of
24 h/d.
Table 4-3. Recommended Inhalation Rates for Workers
Activity Type
Slow activities
Moderate activities
Heavy activities
Hourly average
Mean
(m3/h)
1.1
1.5
2.3
1.3
Upper Percentile
(m3/h)
NA
NA
NA
3.5
NA = Not available.
Source: U.S. EPA, 1997a, Table 5-23.
4-3
-------
IWAIR Technical Background Document
Section 4.0
4.2 Body Weight
Body weights were needed that were consistent with the inhalation rates used. Therefore,
body weights were needed for children aged <1, 1-5, 6-11, and 12-18 years; adult residents aged
19-29 years; and workers of all ages.
The EFH presents summary data on body weight for adults in EFH Table 7-2. The data
for males and females combined are summarized here in Table 4-4. Because an adult resident
aged 19-29 was desired, the weighted average of the values for adults aged 18-24 and 25-34
was used, weighting each by the number of years in that age range (six in the 18-24 range and
five in the 25-34 range).
Table 4-4. Body Weights for Adults, Males and Females
Combined, by Age
Age
-------
IWAIR Technical Background Document
Section 4.0
Table 4-5. Body Weights for Male and Female Children
Combined, Aged 6 Months to 18 Years
Age
-------
IWAIR Technical Background Document Section 4.0
the above exposure duration for the selected receptor type, then the operating life is used instead.
Land application units are an exception to this assumption. Exposure to constituents applied to
land application units is expected to continue after closure. Therefore, in IWAIR, the exposure
duration for land application units is not capped using the operating life specified, but is always
30 years for residents and 7.2 years for workers.
4.4 Exposure Frequency
Exposure frequency is the number of days per year that a receptor is exposed. A value of
350 d/yr was used for residents, and a value of 250 d/yr was used for workers. These are based,
respectively, on 7 d/wk and 5 d/wk for 50 wk/yr and account for the receptor being elsewhere on
vacation for 2 wk/yr.
4-6
-------
IWAIR Technical Background Document Section 5.0
5.0 Inhalation Health Benchmarks
Chronic inhalation health benchmarks used in IWAIR include RfCs to evaluate noncancer
risk from inhalation exposures, and inhalation CSFs to evaluate risk for carcinogens. Inhalation
CSFs are used in the model for carcinogenic constituents, regardless of the availability of an RfC.
A majority of inhalation health benchmarks were identified in IRIS and HEAST (U.S. EPA,
1997b, 200la). IRIS and HEAST are maintained by EPA, and values from IRIS and HEAST
were used in the model whenever available. Benchmarks from Superfund Risk Assessment Issue
Papers, provisional EPA benchmarks, and benchmarks derived by the Agency for Toxic
Substances and Disease Registry (ATSDR) and the California Environmental Protection Agency
(CalEPA) were also used.
This section presents the noncancer and cancer inhalation benchmarks used in IWAIR.
Section 5.1 describes the different types of human health benchmarks used in IWAIR;
Sections 5.2 and 5.3 discuss data sources and the hierarchy used to select benchmarks for
inclusion in IWAIR; and Section 5.4 provides the inhalation health benchmarks included in
IWAIR for each constituent.
IWAIR provides at least one health benchmark for all chemicals included in its database
except 3,4-dimethylphenol and divalent mercury. Users may override the IWAIR values with
their own values. In this way, users can include new information that becomes available on
health benchmarks after IWAIR is released.
5.1 Background
A chemical's ability to cause an adverse health effect depends on the toxicity of the
chemical, the chemical's route of exposure to an individual (either through inhalation or
ingestion), the duration of exposure, and the dose received (the amount that a human inhales or
ingests). The toxicity of a constituent is defined by a human health benchmark for each route of
exposure. Essentially, a benchmark is a quantitative value used to predict a chemical's possible
toxicity and ability to induce a health effect at certain levels of exposure. These health
benchmarks are derived from toxicity data based on animal studies or human epidemiological
studies. Each benchmark represents a dose-response estimate that relates the likelihood and
severity of adverse health effects to exposure and dose. Because individual chemicals cause
different health effects at different doses, benchmarks are chemical-specific.
The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a
daily exposure to the human population (including sensitive subgroups) that is unlikely to pose
an appreciable risk of deleterious noncancer effects during an individual's lifetime. It is not a
direct estimator of risk but rather a reference point to gauge the potential effects. At exposures
-------
IWAIR Technical Background Document Section 5.0
increasingly greater than the RfC, the potential for adverse health effects increases. Lifetime
exposure above the RfC does not imply that an adverse health effect would necessarily occur
(U.S. EPA, 2001a).
The RfC is the primary benchmark used to evaluate noncarcinogenic hazards posed by
inhalation exposures to chemicals. It is based on the "threshold" approach, which is the theory
that there is a "safe" exposure level (i.e., a threshold) that must be exceeded before an adverse
noncancer effect occurs. RfCs do not provide true dose-response information in that they are
estimates of an exposure level or concentration that is believed to be below the threshold level or
no-observed-adverse-effects level (NOAEL). The degree of uncertainty and confidence levels in
RfCs vary and are based on different toxic effects.
The CSF is an upper-bound estimate (approximating a 95 percent confidence limit) of the
increased human cancer risk from a lifetime exposure to an agent. This estimate is usually
expressed in units of proportion (of a population) affected per mg of agent per kg body weight
per day (mg/kg-d)"1. The unit risk factor (URF), which is calculated from the slope factor, is the
upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent
at a concentration of 1 H-g/m3 in air. That is, if the unit risk factor equals 1.5E-6 (jig/m3)"1, then
1.5 excess tumors are expected to develop per 1,000,000 people if they are exposed to 1 |j,g of the
chemical in 1 m3 of air daily for a lifetime (U.S. EPA, 200la). Unlike RfCs, CSFs and URFs do
not represent "safe" exposure levels; rather, they describe the relationship between level of
exposure and probability of effect or risk.
5.2 Data Sources
Human health benchmarks were obtained primarily from IRIS, EPA's electronic database
containing information on human health effects (U.S. EPA, 200la), and from HEAST, a
comprehensive listing of provisional noncarcinogenic and carcinogenic health toxicity values
derived by EPA (U.S. EPA, 1997b). These sources and others used are described below.
Inhalation CSFs are not available from IRIS (with the exception of benzidene) and are often not
available from other sources, so they were calculated from inhalation URFs (which are available
from IRIS), using the following equation (U.S. EPA, 1997b):
URF-. x BW x 1000
inn , — ., -.
- is <5-1>
where
CSFinh = inhalation cancer slope factor (mg/kg-d)"1
URFinh = inhalation unit risk factor (jig/m3)"1
BW = body weight (kg) = 70 kg
1000 = unit conversion (|ig/mg)
IR = inhalation rate (m3/day) = 20 m3/day
5-2
-------
IWAIR Technical Background Document Section 5.0
The body weight and inhalation rate used in this equation are averages; because these standard
estimates of body weight and inhalation rate are used by EPA in the calculation of URFs, these
values are needed to convert inhalation UKFs to inhalation CSFs.
The following sections describe each of the data sources used.
5.2.1 IRIS
Benchmarks in IRIS are prepared and maintained by EPA, and values from IRIS were
used in IWAIR whenever available. Each chemical file in IRIS contains descriptive and
quantitative information on potential health effects. Health benchmarks for chronic
noncarcinogenic health effects include reference doses (RfDs) and RfCs. Cancer classification,
oral CSFs, and inhalation URFs are included for carcinogenic effects. IRIS is the official
repository of Agency-wide consensus information on human health toxicity benchmarks for use
in risk assessments.
5.2.2 Superfund Technical Support Center
The Superfund Technical Support Center (EPA's National Center for Environmental
Assessment (NCEA)) derives provisional RfCs, RfDs, and CSFs for certain chemicals. These
provisional health benchmarks can be found in Risk Assessment Issue Papers. Some of the
provisional values have been externally peer reviewed. The provisional health benchmarks have
not undergone EPA's formal review process for finalizing benchmarks and do not represent
Agency-wide consensus information.
A health benchmark developed by EPA is considered "provisional" if the value has had
some form of Agency review but does not represent Agency-wide consensus (i.e., it does not
appear on IRIS). At the time each provisional health benchmark was derived, all available
toxicological information was evaluated, the value was calculated using the most current
methodology, and a consensus was reached on the value by an individual EPA program office
(but not Agency-wide) (U.S. EPA, 1997b). All health benchmarks not identified from IRIS,
including minimum risk levels (MRLs) and CalEPA cancer potency factors and reference
exposure levels (RELs), were treated as provisional health benchmarks.
5.2.3 HEAST
HEAST is a comprehensive listing of provisional noncarcinogenic and carcinogenic
health toxicity values (RfDs, RfCs, URFs, and CSFs) derived by EPA (U.S. EPA, 1997b).
HEAST benchmarks are considered secondary to those contained in IRIS. Although the health
toxicity values in HEAST have undergone review and have the concurrence of individual EPA
program offices, either they have not been reviewed as extensively as those in IRIS or their data
set is not complete enough for the values to be listed in IRIS. HEAST benchmarks have not been
updated in several years and do not represent Agency-wide consensus information.
5-3
-------
IWAIR Technical Background Document Section 5.0
5.2.4 Other EPA Documents
EPA has also derived health benchmark values that are reported in other risk assessment
documents, such as Health Assessment Documents (HADs), Health Effect Assessments (HEAs),
Health and Environmental Effects Profiles (HEEPs), Health and Environmental Effects
Documents (HEEDs), Drinking Water Criteria Documents, and Ambient Water Quality Criteria
Documents. Evaluations of potential carcinogen!city of chemicals in support of reportable
quantity adjustments were published by EPA's Carcinogen Assessment Group (CAG) and may
include cancer potency factor estimates. Health toxicity values identified in these EPA
documents are usually dated and are not recognized as Agency-wide consensus information or
verified benchmarks.
5.2.5 ATSDR
ATSDR calculates MRLs that are substance-specific health guidance levels for
noncarcinogenic endpoints. An MRL is an estimate of the daily human exposure to a hazardous
substance that is unlikely to pose an appreciable risk of adverse noncancer health effects over a
specified exposure duration. MRLs are based on noncancer health effects only and are not based
on a consideration of cancer effects. MRLs are derived for acute, intermediate, and chronic
exposure durations for oral and inhalation routes of exposure. Inhalation and oral MRLs are
derived in a manner similar to EPA's RfCs and RfDs, respectively (i.e., ATSDR uses the
NOAEL/uncertainty factor (UF) approach); however, MRLs are intended to serve as screening
levels and are exposure-duration-specific. Also, ATSDR uses EPA's 1994 inhalation dosimetry
methodology (U.S. EPA, 1994b) in the derivation of inhalation MRLs.
5.2.6 CalEPA
CalEPA has developed cancer potency factors for chemicals regulated under California's
Hot Spots Air Toxics Program (CalEPA, 1999a). The cancer potency factors are analogous to
EPA's oral and inhalation CSFs. CalEPA has also developed chronic inhalation RELs,
analogous to EPA's RfC, for 120 substances (CalEPA, 1999b, 2000). CalEPA used EPA's 1994
inhalation dosimetry methodology in the derivation of inhalation RELs. The cancer potency
factors and inhalation RELs have undergone internal peer review by various California agencies
and have been the subject of public comment.
5.3 Hierarchy Used
Different benchmarks from more than one of the above sources may be available for
some chemicals. EPA established a hierarchy for the data sources to determine which
benchmark would be used when more than one was available. In establishing this hierarchy,
EPA sources were preferred over non-EPA sources, and among EPA sources, those reflecting
greater consensus and review were preferred.
Because IRIS is EPA's official repository of Agency-wide consensus human health risk
information, benchmarks from IRIS were used whenever available. Benchmarks from the
Superfund Technical Support Center and HEAST were used if none were available from IRIS. If
5-4
-------
IWAIR Technical Background Document Section 5.0
health benchmarks were not available from IRIS, the Superfund Technical Support Center, or
HEAST, benchmarks from alternative sources were sought. Benchmarks were selected from
sources in the following order of preference:
IRIS
Superfund Technical Support Center Provisional Benchmarks
HEAST
ATSDR MRLs
CalEPA chronic inhalation RELs and cancer potency factors
EPA health assessment documents
Various other EPA health benchmark sources.
5.4 Chronic Inhalation Health Benchmarks Included in IWAIR
The chronic inhalation health benchmarks used in IWAIR are summarized in Table 5-1.
The CAS number, constituent name, RfC (in units of mg/m3), noncancer target organs, inhalation
CSF (mg/kg-d)"1, inhalation URF (jig/m3)"1, and reference for each benchmark are provided in
this table. "RfC target organ or critical effect" refers to the target organ (e.g., kidney, liver) or
critical effect used as the basis for the RfC. The critical effect for a few benchmarks is listed as
"no effect" and refers to the fact that no adverse effects were observed in the principal study. For
acetonitrile, the RfC was based on increased mortality at higher dosage levels; therefore, the
target organ was classified as "death." A key to the references cited and abbreviations used is
provided at the end of the table.
For a majority of IWAIR constituents, human health benchmarks were available from
IRIS (U.S. EPA, 2001a), Superfund Risk Issue Papers, or HEAST (U.S. EPA, 1997b).
Benchmarks also were obtained from ATSDR (2001) or CalEPA (1999a, 1999b, 2000). In most
cases, the benchmarks were taken directly from the cited source. This section describes the
exceptions, in which benchmarks were adapted from the cited source.
• The cancer risk estimates for benzene are provided as ranges in IRIS. The
inhalation URF for benzene is 2.2E-6 to 7.8E-6 (|J.g/m3)4 (U.S. EPA, 2001a).
For IWAIR, the upper-range estimate was used (i.e., 7.8E-6 (jig/m3)"1 for the
inhalation URF).
• Based on use of the linearized multistage model, an inhalation URF of 4.4E-6 per
|j,g/m3 was recommended for vinyl chloride in IRIS and was used for IWAIR to
account for continuous, lifetime exposure during adulthood; an inhalation CSF of
1.5E-2 per mg/kg-d was calculated from the URF.
• The benchmarks for 1,3-dichloropropene were used as surrogate data for cis-1,3-
dichloropropylene and trans-l,3-dichloropropylene. The studies cited in the
IRIS file for 1,3-dichloropropene used a technical-grade chemical that contained
about a 50/50 mixture of the cis- and trans-isomers. The RfC is 2E-2 mg/m3.
The inhalation URF for 1,3-dichloropropene is 4E-6 (|J.g/m3)4 (U.S. EPA, 2001a).
5-5
-------
IWAIR Technical Background Document
Section 5.0
Table 5-1. Chronic Inhalation Health Benchmarks
Name
Acetaldehyde
Acetone
Acetonitrile
Acrolein
Acrylamide
Acrylic acid
Acrylonitrile
Allyl chloride
Aniline
Benzene
Benzidine
Benzo(a)pyrene
Bromodichloromethane
Butadiene, 1,3-
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chlorodibromomethane
Chloroform
Chlorophenol, 2-
Chloroprene
Cresols (total)
Cumene
Cyclohexanol
Dibromo-3-chloropropane, 1,2-
Dichlorodifluoromethane
Dichloroethane, 1,2-
Dichloroethylene, 1,1-
CAS
No.
75-07-0
67-64-1
75-05-8
107-02-8
79-06-1
79-10-7
107-13-1
107-05-1
62-53-3
71-43-2
92-87-5
50-32-8
75-27-4
106-99-0
75-15-0
56-23-5
108-90-7
124-48-1
67-66-3
95-57-8
126-99-8
1319-77-3
98-82-8
108-93-0
96-12-8
75-71-8
107-06-2
75-35-4
RfC
(mg/m3)
9.0E-03
3.1E+01
6.0E-02
2.0E-05
l.OE-03
2.0E-03
l.OE-03
l.OE-03
6.0E-02
2.0E-02
7.0E-01
7.0E-03
6.0E-02
l.OE-01
1.4E-03
7.0E-03
6.0E-01
4.0E-01
2.0E-05
2.0E-04
2.0E-01
2.4E+00
7.0E-02
RfC
Ref
I
A
I
I
I
I
I
I
COO
coo
I
SF
SF
A
AC
H
COO
I
solv
I
H
A
COO
RfC Target Organ
or Critical Effect
Respiratory
Neurological
Death
Respiratory
Respiratory
Respiratory
Neurotoxicity
Spleen
Hematological,
developmental,
neurological
Reproductive
Neurological
Liver
Liver
Liver
Reproductive,
developmental
Respiratory
Neurological
Adrenal, kidney
NA
Reproductive
Liver
Liver
Liver
Used in
URF
2.2E-06
1.3E-03
6.8E-05
6.0E-06
1.6E-06
7.8E-06
6.7E-02
1.1E-03
1.8E-05
2.8E-04
1.5E-05
2.4E-05
6.9E-07
2.6E-05
5.0E-05
IWAIR
URF CSFi
Ref (mg/kg-d)1
I 7.7E-03
I 4.6E+00
I 2.4E-01
C99a 2.1E-02
C99a 5.6E-03
I 2.7E-02
I 2.3E+02
C99a 3.9E+00
AC 6.2E-02
I 9.8E-01
I 5.3E-02
AC 8.4E-02
H 2.4E-03
I 9.1E-02
I 1.8E-01
CSFi
Ref
calc
calc
calc
calc
calc
calc
I
calc
AC
calc
calc
AC
calc
calc
calc
(continued)
5-6
-------
IWAIR Technical Background Document
Section 5.0
Table 5-1. (continued)
Name
Dichloropropane, 1,2-
CAS
No.
78-87-5
RfC
(mg/m3)
4.0E-03
RfC
Ref
I
RfC Target Organ
or Critical Effect
Respiratory
URF URF
(|xg/m3) J Ref
CSFi
(mg/kg-d)1
CSFi
Ref
Dichloropropylene, cis-1,3-
10061-01-5 2.0E-02 SUIT Respiratory
4.0E-06 SUIT 1.4E-02 calc
Dichloropropylene, trans-1,3- 10061-02-6 2.0E-02 SUIT Respiratory
4.0E-06 SUIT 1.4E-02 calc
Dimethylbenz[a]anthracene, 7,12- 57-97-6
7.1E-02 C99a 2.5E+02 calc
Dimethylphenol, 3,4-
95-65-8
Dinitrotoluene, 2,4-
121-14-2
S.9E-05 C99a 3.1E-01 calc
Dioxane, 1,4-
123-91-1 3.0E+00
COO Liver, kidney,
hematological
7.7E-06 C99a 2.7E-02 calc
Diphenylhydrazine, 1,2-
122-66-7
2.2E-04 I
7.7E-01 calc
Epichlorohydrin
106-89-8 l.OE-03 I Respiratory
1.2E-06 I
4.2E-03 calc
Epoxybutane, 1,2-
106-88-7 2.0E-02 I Respiratory
Ethoxyethanol acetate, 2-
111-15-9 3.0E-01 COO Developmental
Ethoxyethanol, 2-
110-80-5 2.0E-01
I Hematological,
reproductive
Ethylbenzene
100-41-4 l.OE+00 I Developmental
1.1E-06 SF 3.9E-03 calc
Ethylene dibromide
106-93-4 2.0E-04 H Reproductive
2.2E-04 I
7.7E-01 calc
Ethylene glycol
107-21-1 4.0E-01
COO Respiratory,
kidney,
developmental
Ethylene oxide
75-21-8 3.0E-02 COO Neurological
l.OE-04 H 3.5E-01 calc
Formaldehyde
50-00-0 9.8E-03 A Respiratory
1.3E-05 I
4.6E-02 calc
Furfural
98-01-1 5.0E-02 H Respiratory
Hexachloro-1,3-butadiene
87-68-3
2.2E-05 I 7.7E-02 calc
Hexachlorobenzene
118-74-1
4.6E-04 I 1.6E+00 calc
Hexachlorocyclopentadiene
77-47-4 2.0E-04 I Respiratory
Hexachloroethane
67-72-1
4.0E-06 I 1.4E-02 calc
Isophorone
78-59-1 2.0E+00
C99b Developmental,
kidney, liver
Mercury (elemental)
7439-97-6 3.0E-04 I Neurotoxicity
Methanol
67-56-1 4.0E+00 COO Developmental
Methoxyethanol acetate, 2-
110-49-6 9.0E-02 COO Reproductive
Methoxyethanol, 2-
109-86-4 2.0E-02 I Reproductive
(continued)
5-7
-------
IWAIR Technical Background Document
Section 5.0
Table 5-1. (continued)
Name
Methyl bromide
Methyl chloride
Methyl ethyl ketone
Methyl isobutyl ketone
Methyl methacrylate
Methyl tert-butyl ether
Methylcholanthrene, 3-
Methylene chloride
N,N-Dimethyl formamide
Naphthalene
n-Hexane
Nitrobenzene
Nitropropane, 2-
N-Nitrosodiethylamine
N-Nitrosodi-n-butylamine
N-Nitrosopyrrolidine
o-Dichlorobenzene
o-Toluidine
p-Dichlorobenzene
Phenol
Phthalic anhydride
Propylene oxide
Pyridine
Styrene
TCDD, 2,3,7,8-
Tetrachloroethane, 1,1,1,2-
CAS
No.
74-83-9
74-87-3
78-93-3
108-10-1
80-62-6
1634-04-4
56-49-5
75-09-2
68-12-2
91-20-3
110-54-3
98-95-3
79-46-9
55-18-5
924-16-3
930-55-2
95-50-1
95-53-4
106-46-7
108-95-2
85-44-9
75-56-9
110-86-1
100-42-5
1746-01-6
630-20-6
RfC
(mg/m3)
5.0E-03
9.0E-02
l.OE+00
8.0E-02
7.0E-01
3.0E+00
3.0E+00
3.0E-02
3.0E-03
2.0E-01
2.0E-03
2.0E-02
2.0E-01
8.0E-01
2.0E-01
1.2E-01
3.0E-02
7.0E-03
l.OE+00
RfC
Ref
I
I
I
H
I
I
H
I
I
I
H
I
H
I
COO
H
I
EPA86
I
RfC Target Organ
or Critical Effect
Respiratory
Neurological
Developmental
Liver, kidney
Respiratory
Kidney, liver, eye
Liver
Liver
Respiratory
Neurotoxicity,
respiratory
Adrenal,
hematological,
kidney, liver
Liver
Body weight
Liver
Liver,
cardiovascular,
kidney,
neurological
Respiratory
Respiratory
Liver
Neurotoxicity
URF URF CSFi CSFi
((ig/nrf)1 Ref (mg/kg-d)1 Ref
1.8E-06 H 6.3E-03 calc
6.3E-03 C99a 2.2E+01 calc
4.7E-07 I 1.6E-03 calc
2.7E-03 H 9.5E+00 calc
4.3E-02 I 1.5E+02 calc
1.6E-03 I 5.6E+00 calc
6.1E-04 I 2.1E+00 calc
6.9E-05 AC 2.4E-01 AC
1.1E-05 C99a 3.9E-02 calc
3.7E-06 I 1.3E-02 calc
3.3E+01 H 1.5E+05 H
7.4E-06 I 2.6E-02 calc
(continued)
5-S
-------
IWAIR Technical Background Document
Section 5.0
Table 5-1. (continued)
Name
Tetrachloroethane, 1,1,2,2-
Tetrachloroethylene
Toluene
Tribromomethane
CAS
No.
79-34-5
127-18-4
108-88-3
75-25-2
RfC
(mg/m3)
3.0E-01
4.0E-01
RfC
Ref
A
I
RfC Target Organ
or Critical Effect
Neurological
Neurological,
respiratory
URF
5.8E-05
5.8E-07
1.1E-06
URF
Ref
I
HAD
I
CSFi
(mg/kg-d)1
2.0E-01
2.0E-03
3.9E-03
CSFi
Ref
calc
HAD
calc
Trichloro-1,2,2-trifluoroethane, 76-13-1
1,1,2-
3.0E+01 H Body weight
Trichlorobenzene, 1,2,4-
120-82-1 2.0E-01 H Liver
Trichloroethane, 1,1,1-
71-55-6
2.2E+00 SF Neurological
Trichloroethane, 1,1,2-
79-00-5
1.6E-05 I
5.6E-02 calc
Trichloroethylene 79-01-6 6.0E-01 COO Neurological, eyes 1.7E-06 HAD 6.0E-03 HAD
Trichlorofluoromethane
75-69-4 7.0E-01 H Kidney, respiratory
Triethylamine
121-44-8 7.0E-03
I
Respiratory
Vinyl acetate
108-05-4 2.0E-01 I Respiratory
Vinyl chloride
75-01-4
l.OE-01
I Liver
4.4E-06
1.5E-02 calc
Xylenes
1330-20-7 4.0E-01 A Neurological
a Sources:
A = ATSDRMRLs(ATSDR,2001)
AC = Developed for the Air Characteristic Study (U.S. EPA, 1999d)
C99a = CalEPA cancer potency factor (CalEPA, 1999a)
C99b = CaEPA chronic RELs (CaEPA, 1999b)
COO = CaEPA chronic RELs (CaEPA, 2000)
I = IRIS (U.S. EPA, 200la)
H = HEAST(U.S. EPA, 1997b)
HAD = Health Assessment Document (U.S. EPA, 1986a, 1987a)
SF = Superfund Risk Issue Paper (U.S. EPA, 1998a, 1999a,b,c)
solv = 63 FR 64371-0402 (U.S. EPA, 1998b)
SUIT = surrogate
b RfC and URF are for 1,3-dichloropropylene (U.S. EPA, 2001a)
c RfC is for total xylenes (ATSDR, 2001).
5-9
-------
IWAIR Technical Background Document Section 5.0
• A provisional subchronic RfC of 2E-2 mg/m3 was developed by the Superfund
Technical Support Center (U.S. EPA, 1999a) for carbon tetrachloride. A
provisional chronic RfC of 7E-3 was derived by applying an uncertainty factor of
3 to account for the use of a subchronic study.
• An inhalation acceptable daily intake (ADI) of 2E-3 mg/kg-d based on an
inhalation study was identified for pyridine (U.S. EPA, 1986b). An ADI is
defined as "the amount of chemical to which humans can be exposed on a daily
basis over an extended period of time (usually a lifetime) without suffering a
deleterious effect." The units of an ADI (mg/kg-d) differ from those of an RfC
(mg/m3), illustrating that the inhalation ADI represents an internal dose, while an
RfC represents an air concentration. In the U.S. EPA (1986b), EPA calculated the
inhalation ADI by
1. Using a lowest-observed-adverse-effect level (LOAEL) of 32.35 mg/m3
(for increased liver weights observed in rats exposed to pyridine via
inhalation)
2. Assuming a rat breathes 0.223 m3/day, absorbs 50 percent of the inhaled
pyridine, and weighs 0.35 kg
3. Converting from intermittent to continuous exposure by multiplying by
7/24 and 5/7.l (A "transformed dose" of 2.15 mg/kg-d results from these
first three steps).
4. Dividing the "transformed dose" of 2.15 mg/kg-d by an uncertainly factor
of 1,000 (10 for interspecies extrapolation, 10 for human variability, and
10 for use of a LOAEL) (U.S. EPA, 1986b).
The equation used in U.S. EPA (1986b) to calculate the inhalation ADI is as
follows:
. , . .. ArkT LOAEL x IR x 0.50 x 5/7 x 7/24
inhalation ADI =
BW x 1000
where
LOAEL = lowest-observed-adverse-effect level (mg/m3) = 32.35
IR = inhalation rate of rat (m3/d) = 0.233
BW = body weight of rat (kg) = 0.35.
1 Rats were exposed to pyridine for 7 hours per day (instead of 24), 5 days per week (instead of 7).
-------
IWAIR Technical Background Document
Section 5.0
For IWAIR, the inhalation ADI was converted to a provisional RfC of 7E-3
mg/m3 by eliminating the parameters that were used to estimate an internal dose:
rat inhalation rate, percent absorption, and rat body weight, thereby resulting in an
air concentration suitable for use as a provisional RfC. The calculation is as
follows:
provisional RfC =
LOAEL x 5/7 x 7/24
1000
where
LOAEL = lowest-observed-adverse-effect level (mg/m3) = 32.35.
Provisional inhalation health benchmarks were developed in the Air Characteristic Study
(U.S. EPA, 1999d) for several constituents lacking IRIS, HEAST, alternative EPA, or ATSDR
values. Those used for IWAIR are summarized in Table 5-2 below. Additional details on the
derivation of these inhalation benchmarks can be found in the Revised Risk Assessment for the
Air Characteristic Study (U.S. EPA, 1999d).
• A provisional RfC was developed in the Air Characteristic Study for
2-chlorophenol using route-to-route extrapolation of the oral RfD.
• Based on oral CSFs from IRIS and HEAST, provisional inhalation URFs and
inhalation CSFs were developed for bromodichloromethane,
chlorodibromomethane, and o-toluidine
Table 5-2. Provisional Inhalation Benchmarks Developed in the Air Characteristic Study
CAS
No.
75-27-4
124-48-1
95-57-8
95-53-4
Chemical Name
Bromodichloromethane
(dichlorobromomethane)
Chlorodibromomethane
(dibromochloromethane)
2-Chlorophenol (o-)
o-Toluidine (2-methylaniline)
RfC
(mg/m3)
1.4E-3
RfC Target
Reproductive,
developmental
Inh URF
(Hg/m3)-1
1.8E-5
2.4E-5
6.9E-5
Inh CSF
(mg/kg-d)1
6.2E-2
8.4E-2
2.4E-1
Finally, chloroform presents an unusual case. EPA has classified chloroform as a Group
B2, Probable Human Carcinogen, based on an increased incidence of several tumor types in rats
and mice (U.S. EPA, 2001a). However, based on an evaluation initiated by EPA's Office of
Water (OW), the Office of Solid Waste (OSW) now believes the weight of evidence for the
5-11
-------
IWAIR Technical Background Document Section 5.0
carcinogenic mode of action for chloroform does not support a mutagenic mode of action;
therefore, a nonlinear low-dose extrapolation is more appropriate for assessing risk from
exposure to chloroform. EPA's Science Advisory Board (SAB), the World Health Organization
(WHO), the Society of Toxicology, and EPA all strongly endorse the nonlinear approach for
assessing risks from chloroform. Although OW conducted its evaluation of chloroform
carcinogenicity for oral exposure, a nonlinear approach for low-dose extrapolation would apply
to inhalation exposure to chloroform as well, because chloroform's mode of action is understood
to be the same for both ingestion and inhalation exposures. Specifically, tumorigenesis for both
ingestion and inhalation exposures is induced through cytotoxicity (cell death) produced by the
oxidative generation of highly reactive metabolites (phosgene and hydrochloric acid), followed
by regenerative cell proliferation (U.S. EPA, 1998c). Chloroform-induced liver tumors in mice
have only been seen after bolus corn oil dosing and have not been observed following
administration by other routes (i.e., drinking water and inhalation). As explained in EPA OW's
March 31, 1998, and December 16, 1998, Federal Register notices pertaining to chloroform
(U.S. EPA 1998c and 1998d, respectively), EPA now believes that "based on the current
evidence for the mode of action by which chloroform may cause tumorigenesis, ... a nonlinear
approach is more appropriate for extrapolating low dose cancer risk rather than the low dose
linear approach..." (U.S. EPA 1998c). OW determined that, given chloroform's mode of
carcinogenic action, liver toxicity (a noncancer health effect) actually "is a more sensitive effect
of chloroform than the induction of tumors" and that protecting against liver toxicity "should be
protective against carcinogenicity given that the putative mode of action ... for chloroform
involves cytotoxicity as a key event preceding tumor development" (U.S. EPA 1998c).
The recent evaluations conducted by OW concluded that protecting against chloroform's
noncancer health effects protects against excess cancer risk. EPA now believes that the
noncancer health effects resulting from inhalation of chloroform would precede the development
of cancer and would occur at lower doses than tumor development. Although EPA has not
finalized a noncancer health benchmark for inhalation exposure (i.e., an RfC), ATSDR has
developed an inhalation MRL for chloroform. Therefore, ATSDR's chronic inhalation MRL for
chloroform (0.1 mg/m3) was used in IWAIR.
5-12
-------
IWAIR Technical Background Document Section 6.0
6.0 Calculation of Risk or Allowable Waste
Concentration
This section describes how IWAIR calculates risk or allowable waste concentration using
the emission rate, dispersion factor, exposure factors, and health benchmarks described in
previous sections.
6.1 Calculation of Risk or Hazard Quotient
IWAIR calculates risk for carcinogens and HQ for noncarcinogens. To calculate risk
from a specified chemical to a specified receptor, IWAIR uses the following steps:
1. Calculate emission rates from user inputs or user-specified emission rates; the
emission rates are chemical-specific and, if calculated by IWAIR, depend on user-
specified waste concentrations.
2. Calculate dispersion factors from user inputs or user-specified dispersion factors;
the dispersion factors are receptor-specific.
3. Calculate air concentrations from emission rates and dispersion factors; the air
concentrations are chemical- and receptor-specific.
4. Calculate risks or HQs from air concentrations and, for carcinogens, exposure
factors.
Calculation of emission rates and dispersion factors (Steps 1 and 2) is discussed in
Sections 2 and 3 of this document. For Step 3, IWAIR calculates air concentration from WMU
emission rates and dispersion factors, as follows:
Cair,j = (EjX 106) X DF (6-1)
where
CairJ = air concentration of chemical y' i
Ej = volatile emission rate of chemical y' (g/m2-s)
106 = unit conversion (|j,g/g)
DF = dispersion factor ([|j,g/m3]/[|j,g/m2-s]).
6-1
-------
IWAIR Technical Background Document Section 6.0
For Step 4, IWAIR then uses this calculated air concentration, the exposure factors
described in Section 4, and the health benchmarks described in Section 5 to calculate risk or HQ.
The following subsections describe this calculation for carcinogens and noncarcinogens.
6.1.1 Calculation of Risk for Carcinogens
Risk for carcinogens is calculated as follows:
C . . x 1Q-3 x CSF. x EF 5 IR. x ED.
Risk. = —^ 1 x £ —! 1 (6_2)
J AT x 365 ih V ;
where
10"3 = unit conversion (mg/|ig)
Riskj = individual risk for chemical j (unitless)
CSFj = cancer slope factor for chemical7 (per mg/kg-d)
i = index on age group (e.g., <1 yr, 1-5 yrs, 6-11 yrs, 12-19 yrs, Adult)
IR; = inhalation rate for age group /' (m3/d)
ED; = exposure duration for age group /' (yr)
EF = exposure frequency (d/yr)
AT = averaging time (yr) = 70
365 = unit conversion (d/yr)
BW; = body weight for age group / (kg).
Averaging time corresponds to a typical lifetime and is a fixed input to this equation
because it must be consistent with the 70-year averaging time used to develop the CSF. This
averaging time reflects the lifetime over which cancer risks are averaged. It is not related to the
exposure duration (which is the length of time a receptor is exposed to a chemical) or the
averaging period used for emission rates (which is the length of time over which emission rates
are averaged; this is set to correspond to the exposure duration).
Equation 6-2 reflects calculation of carcinogenic risk for residents and must be modified
slightly to calculate risk for workers. Exposure factors for adult workers are used in place of age-
specific exposure factors for residents. Thus, the summation over age group, /', is not needed for
workers.
IWAIR also calculates the cumulative risk for all carcinogens modeled in a run. This is a
simple sum of the chemical-specific risks already calculated, as follows:
n
CumRisk = E Riskj (6-3)
6-2
-------
IWAIR Technical Background Document Section 6. 0
where
CumRisk = cumulative individual risk for all carcinogens modeled (unitless)
j = index on chemical
n = number of carcinogens modeled.
6.1.2 Calculation of HQ for Noncarcinogens
The HQ for noncarcinogens, which is not dependent on exposure factors, is calculated as
follows:
C. . x l(
3
where
= hazard quotient for chemical y (unitless)
10"3 = unit conversion (mg/|j,g)
= reference concentration for chemical y (mg/m3).
No cumulative HQ is calculated for noncarcinogens. Such summing of HQs is
appropriate only when the chemicals involved have the same target organ.
6.2 Calculation of Allowable Waste Concentration
The calculation of the allowable waste concentration from a target risk or HQ is
somewhat more complex than the risk calculation for several reasons.
First, emission rates depend on whether the waste modeled is aqueous-phase or organic-
phase. In risk calculation mode, the user establishes the waste type as an input, and IWAIR
calculates emission rates and the ensuing risk or HQ for that waste type. In allowable
concentration mode, IWAIR must determine whether to base the allowable concentration on an
emission rate for an aqueous-phase waste or an organic-phase waste.
Second, if risk is linear with waste concentration, then emission rates may be calculated
for a unit waste concentration, and air concentration and risk and HQ equations may be solved
for waste concentration. This is the case for land application units, landfills, and waste piles.
However, emission rates are not linear with waste concentration for aqueous-phase wastes in
surface impoundments because of nonlinearities in biodegradation processes. In surface
impoundments, biodegradation is first order at low concentrations and eventually becomes zero
order at higher concentrations. The concentration at which this shift occurs is chemical-specific.
This is not the case with organic-phase emissions from surface impoundments, because
biodegradation is not modeled in that scenario because of model limitations. Therefore, for
aqueous-phase wastes in surface impoundments, an iterative risk calculation approach must be
used to calculate allowable waste concentration.
6-3
-------
IWAIR Technical Background Document Section 6.0
Finally, when solving the risk and HQ equations for waste concentration (or when
iteratively solving the risk equations for increasing concentrations), care must be taken to ensure
that the resulting concentration is within physical limits for the associated waste type.
The following subsections describe how allowable waste concentrations are calculated for
land application units, landfills, and waste piles; how allowable waste concentrations are
calculated for surface impoundments; and how IWAIR sets an allowable waste concentration that
observes physical limitations.
6.2.1 Calculating Allowable Waste Concentrations for Land Application Units, Landfills,
and Waste Piles
To calculate an allowable concentration, IWAIR uses the following steps:
1. Calculate unitized emission rates from user inputs or user-specified unitized
emission rates; the emission rates are chemical-specific and correspond to a waste
concentration of 1 mg/kg or mg/L; if calculated by IWAIR, unitized emission
rates are also specific to waste type (i.e., aqueous- or organic-phase).
2. Calculate dispersion factors from user inputs or user-specified dispersion factors;
the dispersion factors are receptor-specific.
3. Calculate target air concentrations from target risk or HQ, health benchmarks,
and, for carcinogens, exposure factors; the air concentrations are chemical- and
receptor-specific.
4. Calculate waste concentrations from air concentrations, dispersion factors, and
unitized emission rates, for aqueous- and organic-phase wastes.
5. Choose an allowable concentration from the waste concentrations calculated for
aqueous- and organic-phase wastes.
Calculation of emission rates and dispersion factors (Steps 1 and 2) is discussed in
Sections 2 and 3 of this document. For Step 3, IWAIR uses the same underlying risk and HQ
equations presented in Section 6.1 to calculate allowable concentration for land application units,
landfills, and waste piles. Equations 6-2 (for risk) and 6-4 (for HQ) may be solved for air
concentration. The risk or HQ in those equations becomes the target risk or HQ selected by the
user.
For Step 4, IWAIR then uses an equation comparable to Equation 6-1 to relate air
concentration to waste concentration. However, this equation must be adapted to reflect the use
of a unitized emission rate associated with a waste concentration of 1 mg/kg. This new equation
assumes that emissions are linear with waste concentration. The adapted equation is as follows:
X DF
6-4
-------
IWAIR Technical Background Document Section 6.0
where
Cair = air concentration (|j,g/m3)
CWaste = waste concentration (mg/kg or mg/L)
Eunit = normalized volatile emission rate of constituent ([g/m2-s]/[mg/kg] or
[g/m2-s]/[mg/L] )
106 = unit conversion (|j,g/g)
DF = dispersion factor ([|j,g/m3]/[|j,g/m2-s]).
Equation 6-5 may be solved for waste concentration to calculate waste concentration from air
concentration. This equation is then used with both an aqueous-phase emission rate and an
organic-phase emission rate, to get an aqueous-phase waste concentration and an organic-phase
waste concentration. Section 6.2.3 describes how IWAIR uses those two concentrations to set an
allowable waste concentration (Step 5).
6.2.2 Calculating Allowable Waste Concentrations for Surface Impoundments
For organic-phase wastes in surface impoundments, emissions are linear with waste
concentration, so waste concentration is calculated following Steps 1 to 4, as described in
Section 6.2.1.
For aqueous-phase wastes in surface impoundments, emissions are not linear with waste
concentration. Therefore, an iterative method adapted from the Newton-Raphson method was
used in IWAIR.
The Newton-Raphson method is a commonly used formula for locating the root of an
equation, i.e., the value of x at which f(x) is zero (Chapra and Canale, 1985). The method is
based on the geometrical argument that the intersection of a tangent to a function at an initial
guess, x,. with the x-axis is a better approximation of the root than xt. As illustrated in Figure 6-1,
the method can be adapted to a nonzero target value of f(x), a; in this case, the intersection of the
tangent with the line corresponding to_y = a is used as the next approximation.
Mathematically, the slope of this tangent, f (*,) is given as follows:
f(Xj) - a
fl f \ *• lr
(X;) = (6-6)
-
where
f'(x;) = the slope of f(x) atxt
f(x;) = the value of f(x) at xt
a = the target value for f(x)
x; = the initial guess for x
xi+1 = the next approximation of x.
6-5
-------
IWAIR Technical Background Document
Section 6.0
x
Figure 6-1. Graphical interpretation of the Newton-Raphson method.
This can be rearranged as follows to solve for xi+1:
f(Xj) - a
(6-7)
Equation 6-7 gives an improved value of x for the next iteration; however, to use it, F(x,)
must first be estimated. This is done using finite difference methods:
f(xi+€)-f(Xi)
(6-8)
6-6
-------
IWAIR Technical Background Document Section 6. 0
where
f(x; + e) = the value of f(x) at xt + e
e = a small value relative to xf
For IWAIR, e was set to 0. lxf.
This method can be applied iteratively until f(x) is within a predefined tolerance of the
target, a. For IWAIR, the stopping criteria was set to f(x) = a ± 1%.
For IWAIR, the variable x in the general Newton-Raphson method is waste concentration,
and the function f(x) is the calculation of either risk or HQ based on waste concentration
following the Steps 1 through 4 laid out in Section 6. 1 for risk mode.
As for the other units, where risk is linear with waste concentration, both an aqueous-
phase waste concentration (using the Newton-Raphsm method) and an organic-phase waste
concentration (using the approach described in Section 6.2.1) are developed. Section 6.2.3
describes how IWAIR uses those concentrations to set an allowable waste concentration (Step 5).
6.2.3 Setting an Allowable Waste Concentration
The final step, Step 5, to setting an allowable waste concentration is to choose between
the waste concentrations based on aqueous-phase emissions and organic-phase emissions and to
ensure that the resulting concentration does not exceed physical limitations.
As discussed in Section 2, wastes are typically assumed to be aqueous phase (i.e., dilute
wastes that partition primarily to water). However, aqueous-phase wastes are likely to occur in
land application units, landfills, and waste piles only up to the soil saturation limit, and in surface
impoundments up to the solubility of the chemical in water. At concentrations above the soil
saturation or solubility limit, wastes are more likely to occur in organic phase, unless waste
matrix effects allow supersaturated conditions to occur. Although it is possible for aqueous-
phase wastes to exist with chemicals present above the saturation or solubility limit, this is an
unusual occurrence. Therefore, IWAIR limits calculated allowable waste concentrations based
on aqueous-phase emission rates to the soil saturation or solubility limit or lower. The solubility
limit is a chemical-specific property and is included in the IWAIR chemical properties database.
The soil saturation limit is dependent on site-specific factors, as well as chemical properties;
therefore, IWAIR calculates it from user inputs as follows:
(6-9)
where
Csat = soil saturation limit (mg/kg)
S = solubility limit (mg/L)
6-7
-------
IWAIR Technical Background Document Section 6. 0
pb = bulk density of soil/waste matrix (kg/L)
Kd = soil-water partition coefficient (L/kg), calculated as shown below in
Equation 6-10 for organic chemicals; this is an input for mercury
ew = water-filled soil porosity (unitless)
H' = dimensionless Henry's law constant (unitless = H/RT)
ea = air-filled soil porosity (unitless).
and
Kd = Koc X foc (6-10)
where
Kd = soil-water partition coefficient (L/kg)
Koc = organic carbon partition coefficient (L/kg), calculated as shown below in
Equation 6-11
foc = fraction organic carbon in waste (unitless).
Fraction organic carbon is set to a fixed value of 0.014. This value was derived from the median
of a set of values for many (but not all) of the locations included in the IWAIR dispersion factor
database.
Koc = 10--- (6-11)
where
Kow = octanol-water partition coefficient (L/kg).
Wastes can occur in the organic phase at concentrations below the soil saturation or
solubility limit, as well as up to 1,000,000 mg/kg or mg/L (ppm). Regardless of whether the
chemical is in the aqueous or organic phase, the concentration cannot exceed 1,000,000 mg/kg or
mg/L (ppm) by definition. Therefore, IWAIR limits calculated allowable waste concentrations
based on organic-phase emission rates to 1,000,000 ppm or lower.
As described in Sections 6.2.1 and 6.2.2, IWAIR calculates waste concentrations for both
aqueous- and organic-phase emission rates. It then chooses between them using the following
decision rules:
• If one of the two concentrations is physically impossible (greater than saturation or
solubility limits for aqueous phase, or greater than 1,000,000 ppm for organic
phase), it is discarded and the other is used.
• If both concentrations are impossible, then the allowable concentration is set to the
saturation or solubility limit or 1,000,000 ppm, depending on which produces the
higher risk. That risk is reported as the maximum achievable risk.
6-8
-------
IWAIR Technical Background Document Section 6.0
• If both concentrations are physically possible, IWAIR selects the lower of the two.
This is the lowest concentration that could produce the target risk. The underlying
waste type (aqueous or organic) is reported. For most chemicals, this will be the
concentration based on aqueous-phase emissions, as these are greater than the
organic-phase emissions for the same concentration and, therefore, produce greater
risk. Formaldehyde is a notable exception and has greater emissions (and therefore
greater risk) from an organic-phase waste than an aqueous-phase waste.
6-9
-------
IWAIR Technical Background Document Section 7.0
7.0 References
ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Minimal Risk Levels
(MRLs)for Hazardous Substances. http://atsdrl.atsdr.cdc.gov:8080/mrls.html
Beltrame, Paolo, Pier Luigi Beltrame, et al. 1980. "Kinetics of phenol degradation by activated
sludge in a continuous stirred reactor." J. WPCF. 52(1).
Beltrame, Paolo, Pier Luigi Beltrame, and Paolo Carniti. 1982. "Kinetics of biodegradation of
mixtures containing 2,4-dichlorophenol in a continuous stirred reactor." La Chimica e
L 'Industria, 64(9). September.
Beltrame, Paolo, Pier Luigi Beltrame, et al., 1982. "Kinetics of biodegradation of mixtures
containing 2,4-dichlorophenol in a continuous stirred reactor." Water Res., 16, pp. 429-
433.
Berglund, R.L., and G.M. Whipple. 1987. Predictive modeling of organic emissions. Chemical
Engineering Progress.
Budavari, S. (Ed.). 1996. The Merck Index, An Encyclopedia of Chemicals, Drugs, and
Biologicals. 12th Edition. Rahway, NJ: Merck & Co. Inc.
CalEPA (California Environmental Protection Agency). 1999a. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part II. Technical Support Document for Describing
Available Cancer Potency Factors. Office of Environmental Health Hazard Assessment,
Berkeley, CA. Available online at http://www.oehha.org/scientific/hsca2.htm.
CalEPA (California Environmental Protection Agency). 1999b. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part III. Technical Support Document for the
Determination ofNoncancer Chronic Reference Exposure Levels. SRP Draft. Office of
Environmental Health Hazard Assessment, Berkeley, CA. Available online at
http ://www. oehha. org/hotspots/RAGSII. html.
CalEPA (California Environmental Protection Agency). 2000. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part III. Technical Support Document for the
Determination ofNoncancer Chronic Reference Exposure Levels. Office of
Environmental Health Hazard Assessment, Berkeley, CA. Available online (in 3
sections) at http://www.oehha.org/air/chronic_rels/22RELS2k.html,
http: //www. oehha. org/air/chroni c_rel s/42kChREL. html,
http://www.oehha.org/air/chroni c_rels/Jan200 IChREL.html.
-------
IWAIR Technical Background Document Section 7.0
CambridgeSoft Corporation. 2001. ChemFinder.com database and internet searching.
http://chemfmder.cambridgesoft.com. Accessed July 2001.
Chapra, S.C., andR.P. Canale. 1985. Numerical Methods for Engineers with Personal
Computer Applications. McGraw-Hill, New York.
Coburn, J., C. Allen, D. Green, and K. Leese. 1988. Site Visits of Aerated and Nonaerated
Impoundments. Summary Report. U.S. EPA 68-03-3253, Work Assignment 3-8.
Research Triangle Institute, RTF, NC.
Demirjian, Y.A., R.R. Redish, et al., 1983. The fate of organic pollutants in a wastewater land
treatment system using lagoon impoundment and spray irrigation. EPA-600/2-83-0770,
NTIS No. PB83-259853, pp. 8-48.
ERG (Eastern Research Group) and Abt Associates. 1992. Technical Support Document for the
Surface Disposal of Sewage Sludge. Prepared for U.S. EPA, OW, Washington, DC.
November 1992.
Hannah, S.A., B.M. Austern, et al., 1986. "Comparative removal of toxic pollutants by six
wastewater treatment processes." WPCF, 58(1), pp. 27-34.
Hasset, J.J., J.C. Means, W.L. Banwart, and S.G. Wood. 1980. Sorption Properties of Sediments
and Energy-Related Pollutants. U.S. Environmental Protection Agency, Athens, GA.
EPA-600/3-80-041.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, E.M. Michalenko, and H.T. Printup.
(Ed.). 1991. Handbook of Environmental Degradation Rates. Lewis Publishers,
Chelsea, MI.
Jury, W.A., D. Russo, G. Streile, and H. El Abd. 1990. Evaluation of volatilization by organic
chemicals residing below soil surface. Water Resources Research 26(1): 13-20. January.
Kincannon, D.F., A. Weinert, et al., 1982. "Predicting treatability of multiple organic priority
pollutant wastewaters from single pollutant treatability studies." Presented at the 37th
Purdue Industrial Waste Conference, Purdue University, West Lafayette, IN.
Kollig, H.P. 1993. Environmental Fate Constants for Organic Chemicals Under Consideration
for EPA 's Hazardous Waste Identification Projects. EPA/600/R-93/132., Athens, GA.
August.
Lesiecki, R.J., M.K. Koczwara, et al., 1987. "Biological treatment of selected aqueous organic
hazardous wastes." Presented at the 13th Annual Research Symposium, Cincinnati, OH.
EPA/600/9-87/015.
Li, C., and E. Voudrais. 1994. Migration and sorption of jet fuel cycloalkane and aromatic
vapors in unsaturated soil. Environmental Progress 13(4): 290-297.
7-2
-------
IWAIR Technical Background Document Section 7.0
Loehr, R., D. Erickson, and L. Kelmar. 1993. Characteristics of residues at hazardous waste
land treatment units. Water Research 27(7): 1127-1138.
Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt. 1990. Handbook of Chemical Property
Estimation Methods: Environmental Behavior of Organic Compounds. American
Chemical Society, Washington, DC.
Mason, B., and L.G. Berry. 1968. Elements of Mineralogy. San Francisco: W.H. Freeman and
Company, p. 410.
Mathews, J.H. 1992. Numerical Methods for Mathematics, Science, and Engineering.
Englewood Cliffs, NJ: Prentice Hall.
Perry, R.H., and D.W. Green. 1984. Perry's Chemical Engineer's Handbook, 6th Edition.
McGraw-Hill, New York.
Petrasek, A.C., 1981. "Removal and partitioning of the volatile priority pollutants in
conventional wastewater treatment plants." Report written for the Municipal
Environmental Research Laboratory, Office of Research and Development, U.S.
Environmental Protection Agency, Cincinnati, OH 45268.
Petrasek, A.C., B.M. Austern, and T.W. Neiheisel. 1983. "Removal and partitioning of volatile
organic priority pollutants in wastewater treatment." Presented at the 9th U.S.-Japan
Conference on Sewage Treatment Technology, Tokyo, Japan.
Fitter, P., 1976. "Determination of biological degradability of organic substances." Water
Research, 10, pp. 231-235.
Reid, R.C., J.M. Prausnitz, and T.K. Sherwood. 1977. The Properties of Gases and Liquids, 3rd
Edition. McGraw-Hill, New York.
Syracuse Research Corporation (SRC). 1999. CHEMFATE Chemical Search, Environmental
Science Center, Syracuse, NY. http://esc.syrres.com/efdb/Chemfate.htm. Accessed July
2001.
Shroeder, K., R. Clickner, andE. Miller. 1987. Screening Survey of Industrial Subtitle D
Establishments. Draft Final Report. Westat, Inc., Rockville, MD., for U.S. EPA Office of
Solid Waste. EPA Contract 68-01-7359. December.
Thibodeaux, L.J., and D.G. Parker. 1976. Desorption Limits of Selected Industrial Gases and
Liquids from Aerated Basins. College of Engineering, University of Arkansas,
Fayetteville, Arkansas.
7-3
-------
IWAIR Technical Background Document Section 7.0
U.S. EPA (Environmental Protection Agency). 1986a. Addendum to the Health Assessment
Document for Tetrachloroethylene (Perchloroethylene). Updated Carcinogenicity
Assessment for Tetrachloroethylene (Perchloroethylene, PERC, PCE). External Review
Draft. EPA/600/8-82-005FA. Office of Health and Environmental Assessment, Office of
Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1986b. Health and Environmental Effects
Profile for Pyridine. EPA/600/X-86-168. Environmental Criteria and Assessment Office,
Office of Research and Development, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1987a. Addendum to the Health Assessment
Document for Trichloroethylene. Updated Carcinogenicity Assessment for
Trichloroethylene. External Review Draft. EPA/600/8-82-006FA. Office of Health and
Environmental Assessment, Office of Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1987b. Processes, Coefficients, and Models for
Simulation Toxic Organics and Heavy Metals in Surface Waters. EPA/600/3-87/015.
Office of Research and Development, Athens, GA.
U.S. EPA (Environmental Protection Agency). 1989. Development of Risk Assessment
Methodology for Municipal Sludge Lnadfilling. EPA 600/6-90-008. ORD, Washington,
DC. August.
U.S. EPA (Environmental Protection Agency). 1991. Hazardous Waste TSDF-Background
Information for Proposed RCRA Air Emission Standards. Volume II-Appendices D-F.
EPA-450/3-89/023b. Office of Air Quality Planning and Standards. Research Triangle
Park, NC.
U.S. EPA (Environmental Protection Agency). 1992. Technical Support Document for the Land
Application of Sewage Sludge-Volume II. EPA 822/R-93-001b. OW, Washington, DC.
November.
U.S. EPA (Environmental Protection Agency). 1994a. Air Emissions Models for Waste and
Wastewater. EPA-453/R-94-080-A Appendix C. OAQPS, RTF, NC.
U.S. EPA (Environmental Protection Agency). 1994b. Methods for Derivation of Inhalation
Reference Concentrations and Application of Inhalation Dosimetry. EPA/600/8-90-
066F. Environmental Criteria and Assessment Office, Office of Health and
Environmental Assessment, Office of Research and Development, Research Triangle
Park, NC.
U.S. EPA (Environmental Protection Agency). 1995. User's Guide for the Industrial Source
Complex (ISC3) Dispersion Models. EPA-454/B-95-003a. Office of Air Quality
Planning and Standards, Research Triangle Park, NC.
7-4
-------
IWAIR Technical Background Document Section 7.0
U.S. EPA (Environmental Protection Agency). 1997'a. Exposure Factors Handbook. Office of
Research and Development, National Center for Environmental Assessment. Office of
Solid Waste and Emergency Response, Washington, DC.
U.S. EPA (Environmental Protection Agency). 1997b. Health Effects Assessment Summary
Tables (HEAST). EPA-540-R-97-036. FY 1997 Update.
U.S. EPA (Environmental Protection Agency). 1997c. Mercury Study Report to Congress.
Volume III—Fate and Transport of Mercury in the Environment. EPA 452/R-97/005.
Office of Air Quality Planning and Standards and Office of Research and Development,
Washington, DC.
U.S. EPA (Environmental Protection Agency). 1997d. Superfund Chemical Data Matrix
(SCDM). Office of Emergency and Remedial Response. Web site at
http://www.epa.gov/oerrpage/superfund/resources/scdm/index.htm. June
U.S. EPA (Environmental Protection Agency). 1998a. Risk Assessment Issue Paper for:
Derivation of a Provisional Chronic RfCfor Chlorobenzene (CASRN108-90-7). 98-
020/09-18-98. National Center for Environmental Assessment. Superfund Technical
Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1998b. Hazardous waste management system;
identification and listing of hazardous waste; solvents; final rule. Federal Register
63 FR 64371-402.
U.S. EPA (Environmental Protection Agency). 1998c. National primary drinking water
regulations: disinfectants and disinfection byproducts notice of data availability; Proposed
Rule. Federal Register 63 (61): 15673-15692. March 31.
U.S. EPA (Environmental Protection Agency). 1998d. National primary drinking water
regulations: disinfectants and disinfection byproducts; final rule. Federal Register 63
(241): 69390-69476. December 16.
U.S. EPA (Environmental Protection Agency). 1999a. Risk Assessment Paper for: The
Derivation of a Provisional Subchronic RfCfor Carbon Tetrachloride (CASRN 56-23-5).
98-026/6-14-99. National Center for Environmental Assessment. Superfund Technical
Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999b. Risk Assessment Issue Paper for:
Evaluating the Carcinogenicity of Ethylbenzene (CASRN 100-41-4). 99-011/10-12-99.
National Center for Environmental Assessment. Superfund Technical Support Center,
Cincinnati, OH.
7-5
-------
IWAIR Technical Background Document Section 7.0
U.S. EPA (Environmental Protection Agency). 1999c. Risk Assessment Issue Paper for:
Derivation of Provisional Chronic and Subchronic RfCsfor 1,1,1-Trichloroethane
(CASRN 71-55-6). 98-025/8-4-99. National Center for Environmental Assessment.
Superfund Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999d. Revised Risk Assessment for the Air
Characteristic Study. EPA-530-R-99-019a. Volume 2. Office of Solid Waste,
Washington, DC.
U.S. EPA (Environmental Protection Agency). 2000. Exposure and Human Health
Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds.
Part I: Estimating Exposure to Dioxin-Like Compounds. Volume 3—Properties,
Environmental Levels, and Background Exposures. Draft Final Report. EPA/600/P-
00/001. Office of Research and Development, Washington, DC. September.
U.S. EPA (Environmental Protection Agency). 2001a. Integrated Risk Information System
(IRIS). National Center for Environmental Assessment, Office of Research and
Development, Washington, DC. Available online at http://www.epa.gov/iris/
U.S. EPA (Environmental Protection Agency). 2001b. WATER9. Version 1.0.0. Office of Air
Quality Planning and Standards, Research Triangle Park, NC. Web site at
http://www.epa.gov/ttn/chief/softward.html. May 1
U.S. NLM (National Library of Medicine). 2001. Hazardous Substances Data Bank (HSDB).
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Accessed July 2001.
7-6
-------
Appendix A
Considering Risks from Indirect Pathways
-------
-------
IWAIR Technical Background Document
Appendix A
Appendix A
Considering Risks from Indirect Pathways
A. 1 What are "Indirect Risks" ?
Direct Pathways: An individual is directly exposed to
the contaminated medium, such as air or
groundwater, into which the chemical was released.
Indirect Pathways: An individual is indirectly
exposed when a chemical that is released into one
medium (for example, air), is subsequently
transported to other media, such as water, soil, or
food, to which the individual comes in contact.
IWAIR assesses exposures by direct
inhalation of a chemical. It is possible,
however, that environmental contaminants
can be transferred to other media resulting in
an indirect exposure to the pollutant. The
purpose of this section is to provide risk
assessors with information on health risks that
may result from volatile emissions other than
from the inhalation pathway. An indirect
pathway of exposure is when a chemical that
is released into one medium (for example, air)
is subsequently transported to other media, such as water, soil, or food, to which a receptor is
exposed. For example, chemical vapors that are released from a WMU and transported to an
adjacent agricultural field may diffuse into vegetation, deposit on vegetation, or may be taken up
by vegetation from the soil. Individuals who subsequently eat the produce from that field may be
exposed to contaminants in their diet. Additional indirect exposures can occur through the
ingestion of contaminated fish, or animal products, such as milk, beef, pork, poultry, and eggs.
Figure A-l shows these pathways graphically. The arrows indicate the flow of pollutants
through the pathways. Pollutants are released from a source, dispersed through the air, and
deposited on crops, pastures, soil, and surface water. From there, they may be taken up into
plants or animal tissues. Humans may then be exposed by ingesting soil (through hand-to-mouth
contact), ingesting plant products, or ingesting animal products (including fish). Although not
shown in Figure A-l, humans may also ingest groundwater and surface water as drinking water
sources. Groundwater exposures are modeled by the Industrial Waste Management Evaluation
Model (IWEM), and surface water sources of drinking water are presumed to be treated to
remove contaminants.
A-3
-------
IWAIR Technical Background Document
Appendix A
Dispersion
Figure A-l. Indirect exposure pathways.
A.2 Determining When Indirect Pathways May Be Important
There are two key factors a facility manager should consider when determining the need
to assess the human health risk from indirect pathways of exposure. First, only certain land uses
near a WMU may pose potential risks through indirect exposure pathways. Second, only certain
chemicals may have properties that favor indirect pathways. These two criteria are explained in
the following paragraphs.
A.2.1 Land Use
As described above, indirect exposures can occur when a vapor-phase constituent in the
air is transported into surface water or taken up by produce or by animal products (via feed plants
or surface water). However, these pathways are unlikely to be of concern unless the land use
near the site includes one or more of the following:
• Residential home-gardening
• Agriculture (including production of produce and animal products for human
consumption)
• Farms that grow feed for animals
A-4
-------
IWAIR Technical Background Document Appendix A
• Recreational fishing
• Recreational hunting areas.
A.2.2 Chemical Properties
In addition to land use, the chemical properties of the constituents in the waste are
important in determining whether indirect pathways are of potential concern. Some chemicals
exhibit properties that tend to favor indirect pathways, while others do not, or do so to a lesser
extent. The chemical properties of interest are those that reflect the tendency for a chemical to be
persistent in the environment, bioaccumulate in plants or animals, or be toxic when ingested.1 A
facility manager should consider these properties when determining whether an assessment of
indirect pathways may be necessary for the WMU. The following subsections provide a brief
description of some of the chemical properties that can be used to predict a constituent's
persistence, bioaccumulation potential, and toxicity.
Persistence
A chemical's persistence refers to how long the chemical remains in the environment
without being chemically or biologically broken down or altered. A chemical considered to be
highly persistent remains in the environment for a relatively long period of time, although it may
move through different media (e.g., from soil to water to sediment). Because persistent
chemicals remain in the environment, they can accumulate in environmental media and/or plant
and animal tissue. As a result, the temporal window for exposure through both direct and
indirect pathways may be extended, and the likelihood of exposure will increase. Persistence is
frequently expressed in terms of half-life. For example, if a chemical has a half-life of 2 days, it
will take 2 days for a given quantity of the chemical to be reduced by one-half due to chemical
and biological processes. The longer the half-life, the more persistent the chemical. A related
chemical property is degradation rate, which is inversely related to half-life. Thus, the lower the
degradation rate, the more persistent the chemical. Data on soil biodegradation rates are
presented for the IWAIR chemicals in Appendix B; this property may be used as a general
indicator of persistence potential.
Bioaccumulation Potential
Bioaccumulation potential refers to a chemical's tendency to accumulate in plants and
animals. For example, plants may accumulate chemicals from the soil through their roots. Some
of these chemicals are transformed or combined with others and used by the plant; others are
simply eliminated; and others accumulate in the plant roots, leaves, or edible parts of the plant.
Animals also bioaccumulate certain chemicals in different tissues or organs. For chemicals that
1 The tendency of chemical constituents to be persistent and bioaccumulate are a function of both the
chemical/physical attributes of the chemical (e.g., Kow) and the environmental setting (such as the physical
characteristics of the system, e.g., dissolved organic carbon, soil pH; or the biology of organisms that inhabit the
system, e.g., crops, fish species); however, it is convenient to think of persistence and bioaccumulation potential as
intrinsic properties when considering indirect exposure pathways.
A-5
-------
IWAIR Technical Background Document
Appendix A
bioaccumulate, the concentration in the plants and animals can be higher than the concentration
in the environment. As a result, a human who eats the plant or animal may be exposed to a
higher concentration in the food than in the contaminated medium.2 Bioaccumulation potential
may be expressed as a bioaccumulation factor (BAF) or a bioconcentration factor (BCF); these
factors express the relationship between the concentration in biota and the concentration in the
environmental medium. Bioaccumulation potential may also be expressed as a biotransfer factor
for animal products, representing the relationship between the exposure concentration and the
mass of contaminated plants ingested daily.
Chemicals that tend to accumulate in
plants and animal tissues often have a
characteristically high affinity for lipids (fats).
This tendency is reflected by the octanol-
water partition coefficient (Kow),3 a laboratory
measurement of the attraction of a chemical
to water versus its attraction to lipids (fats).
In these experiments, octanol is used as a
surrogate for lipids. Because chemicals with
higher Kow values have been shown to have a
greater tendency to accumulate in the fatty
tissue of animals, the BAF and BCF are
generally accepted as useful predictors of
bioaccumulation potential (see text box for
definitions and examples of other parameters
that are often used to evaluate indirect
exposures through the ingestion of produce
and animal products). Some chemicals with
high Kow values, such as polycyclic aromatic
hydrocarbons (PAHs), do not accumulate
appreciably in animals that have the capacity
to metabolize the chemical and eliminate it
from their systems. Moreover, this strong
affinity for lipids also means that the
chemical has a strong affinity for organic
carbon in soil and surface water. Chemicals
that are strongly sorbed to the organic
component in soil may not be readily taken up
by plants. For example, dioxin is poorly
taken up from the soil by virtually all species
of plants that have been tested.
Parameters Used to Evaluate Indirect Exposures
BCF: Bioconcentration Factor for Fish. Defined as
the ratio of chemical concentration in the fish to the
concentration in the surface water. Fish are exposed
only to contaminated water.
BAF: Bioaccumulation Factor for Fish. Defined as
the ratio of the chemical concentration in fish to the
concentration in the surface water. Fish are exposed
to contaminated water and plants/prey.
BSAF: Biota-Sediment Accumulation Factor for
Fish. Generally applied only to highly hydrophobic
organic chemicals, and defined as the ratio of the
lipid-normalized concentration in fish to the organic
carbon-normalized concentration in surface sediment.
Fish are exposed to contaminated pore water,
sediment, and plants/prey.
Br: Plant-Soil Bioconcentration Factor. Defined as
the ratio between the chemical concentration in the
plant and the concentration in soil. It varies by plant
group (e.g., root vegetables, aboveground
vegetables).
Bv: Air-Plant Bioconcentration Factor. Defined as
the mass-based ratio between the chemical
concentration in the plant and the vapor-phase
chemical concentration in the air. It is varies by plant
group (e.g., leafy vegetables, forage).
Ba: Plant-Animal Biotransfer Factor. Defined as the
ratio between the chemical concentration in the
animal tissue and the amount of chemical ingested
per day. It varies by type of animal tissue (e.g., beef,
milk).
Even though the concentration in food may not be significantly higher than in the environmental media,
the consumption rate of produce and meat/dairy products may lead to a substantial exposure to contaminants.
3 Because octanol-water coefficients can span many orders of magnitude, they are normally discussed in
terms of their log values (log Kow).
A-6
-------
IWAIR Technical Background Document Appendix A
Consequently, the use of chemical properties should be supplemented with information from
field studies to determine whether the chemical is of potential concern through indirect exposure
pathways. Data on log Kow are presented for the IWAIR chemicals in Appendix B; they may be
used as a first-cut indicator of bioaccumulation potential. As a general rule, chemicals with
relatively high Kow values tend to accumulate in plants and animals to a greater extent than
chemicals with relatively low Kow values.
Toxicity
The toxicity of chemicals to humans depends on the route of exposure—inhalation or
ingestion. IWAIR contains health benchmarks for inhalation exposures. However, the indirect
pathways discussed here refer to ingestion exposures. Therefore, even if a chemical is released
into the air and tends to bioaccumulate in plant or animal products, if it is not very toxic by the
ingestion pathway, then indirect pathways will be of less concern. Two benchmarks are used to
predict the toxicity of a chemical that is ingested: the cancer slope factor (CSF, which measures
the tendency of a chemical to cause cancer) and the reference dose (RfD, which provides a
threshold below which a chemical is unlikely to result in adverse, noncancer health effects). The
CSF is a measure of carcinogenic potency; consequently, a larger value indicates greater toxicity.
However, the RfD is a threshold at which adverse effects are not expected; therefore, a smaller
value indicates greater toxicity.
Oral toxicity benchmarks are not used in IWAIR; therefore, for convenience, the oral
toxicity benchmarks (oral CSF and RfD) are presented for the IWAIR chemicals in Table A-l.
A.3 Additional Information
Indirect risk assessments are often site-specific, require a significant amount of
information about the area surrounding the WMU, and can be complex depending on the
chemicals of concern. However, indirect pathways should not be overlooked as a potential
source of risk if the chemical properties and surrounding land uses suggest potential risks
through indirect exposures.
If it appears that indirect pathways may be of concern, Methodology for Assessing Health
Risks Associated with Multiple Pathways of Exposure to Combustor Emissions (U.S. EPA,
1998b) presents guidance developed by the Agency for conducting indirect risk assessments for
most chemicals. This document can be used to determine whether further assessment of indirect
pathways is needed, and, if so, how to conduct such an assessment. For dioxin-like compounds,
indirect pathways are evaluated somewhat differently; see U.S. EPA (2000a), Exposure and
Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related
Compounds. Part I: Estimating Exposure to Dioxin-Like Compounds.
A-7
-------
IWAIR Technical Background Document
Appendix A
Table A-l. Oral Health Benchmarks for IWAIR Chemicals
IWAIR Constituent Name
CASRN
RfD RfD CSFo (per CSFo
(mg/kg-d) Source mg/kg-d) Source Comment
1,1,1,2-Tetrachloroethane 630-20-6
1,1,1-Trichloroethane 71-55-6
1,1,2,2-Tetrachloroethane 79-34-5
l,l,2-Trichloro-l,2,2-trifluoroethane 76-13-1
1,1,2-Trichloroethane 79-00-5
1,1 -Dichloroethylene 75-35-4
1,2,4-Trichlorobenzene 120-82-1
l,2-Dibromo-3-chloropropane 96-12-8
1,2-Dichloroethane 107-06-2
3.0E-02 IRIS 2.6E-02 IRIS
2.8E-01 SF
6.0E-02 SF 2.0E-01 IRIS
3.0E+01 IRIS
4.0E-03 IRIS 5.7E-02 IRIS
9.0E-03 IRIS 6.0E-01 IRIS
l.OE-02 IRIS
1.4E+00 HEAST intermediate MRL
available
9.1E-02 IRIS intermediate MRL
available
1 ,2-Dichloropropane
1 ,2-Diphenylhydrazine
1,2-Epoxybutane
1,3 -Butadiene
1,4-Dioxane
2,3,7,8-TCDD
2,4-Dinitrotoluene
2-Chlorophenol
2-Ethoxyethanol
2-Ethoxyethanol acetate
2-Methoxyethanol
2-Methoxyethanol acetate
2-Nitropropane
3 ,4-Dimethylphenol
3 -Methylcholanthrene
7, 12-Dimethylbenz[a]anthracene
78-87-5 9.0E-02 ATSDR 6.8E-02 HEAST
122-66-7 8.0E-01 IRIS
106-88-7
106-99-0
123-91-1 1.1E-02 IRIS
1746-01-6 l.OE-09 ATSDR 1.5E+05 HEAST
121-14-2 2.0E-03 IRIS 6.8E-01 IRIS CSFo is for 2,4-72,6-
mixture
95-57-8 5.0E-03 IRIS
110-80-5 4.0E-01 HEAST
111-15-9 3.0E-01 HEAST
109-86-4 l.OE-03 HEAST
110-49-6 2.0E-03 HEAST
79-46-9
95-65-8 l.OE-03 IRIS
56-49-5
57-97-6
(continued)
A-8
-------
IWAIR Technical Background Document
Appendix A
IWAIR Constituent Name
Acetaldehyde
Acetone
Acetonitrile
Acrolein
Acrylamide
Acrylic acid
Acrylonitrile
Allyl chloride
Aniline
Benzene
Benzidine
Benzo(a)pyrene
Bromodichloromethane
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chlorodibromomethane
Chloroform
Chloroprene
cis- 1 , 3 -Dichloropropylene
Table
CASRN
75-07-0
67-64-1
75-05-8
107-02-8
79-06-1
79-10-7
107-13-1
107-05-1
62-53-3
71-43-2
92-87-5
50-32-8
75-27-4
75-15-0
56-23-5
108-90-7
124-48-1
67-66-3
126-99-8
10061-01-5
A-l. (continued)
RfD
(mg/kg-d)
l.OE-01
2.0E-02
2.0E-04
5.0E-01
l.OE-03
3.0E-03
2.0E-02
l.OE-01
7.0E-04
2.0E-02
2.0E-02
l.OE-02
2.0E-02
3.0E-02
RfD CSFo(per CSFo
Source mg/kg-d) Source Comment
IRIS
HEAST
IRIS 4.5E+00 IRIS
IRIS
HEAST 5.4E-01 IRIS
5.7E-03 IRIS
5.5E-02 IRIS upper range estimate
used for CSFo
IRIS 2.3E+02 IRIS
7.3E+00 IRIS
IRIS 6.2E-02 IRIS
IRIS
IRIS 1.3E-01 IRIS
IRIS
IRIS 8.4E-02 IRIS
IRIS
HEAST
IRIS l.OE-01 IRIS RfD & CSFo are for
Cresols (total)
Cumene
Cyclohexanol
Dichlorodifluoromethane
Epichlorohydrin
1319-77-3 5.0E-02 surr
98-82-8 l.OE-01 IRIS
108-93-0 1.7E-05 solvents
75-71-8 2.0E-01 IRIS
106-89-8 2.0E-03 HEAST 9.9E-03
1,3 -dichloropropene
RfD is for m-cresol
IRIS
(continued)
A-9
-------
IWAIR Technical Background Document
Appendix A
Table A-l. (continued)
IWAIR Constituent Name
Ethylbenzene
Ethylene dibromide
Ethylene glycol
Ethylene oxide
Formaldehyde
Furfural
Hexachloro- 1 , 3 -butadiene
Hexachlorobenzene
Hexachlorocyclopentadiene
Hexachloroethane
Isophorone
Mercury
Methanol
Methyl bromide
Methyl chloride
Methyl ethyl ketone
Methyl isobutyl ketone
Methyl methacrylate
Methyl tert-butyl ether
Methylene chloride
N,N-Dimethyl formamide
Naphthalene
n-Hexane
Nitrobenzene
N-Nitrosodiethylamine
N-Nitrosodi-n-butylamine
CASRN
100-41-4
106-93-4
107-21-1
75-21-8
50-00-0
98-01-1
87-68-3
118-74-1
77-47-4
67-72-1
78-59-1
7439-97-6
67-56-1
74-83-9
74-87-3
78-93-3
108-10-1
80-62-6
1634-04-4
75-09-2
68-12-2
91-20-3
110-54-3
98-95-3
55-18-5
924-16-3
RfD
(mg/kg-d)
l.OE-01
2.0E+00
2.0E-01
3.0E-03
3.0E-04
8.0E-04
6.0E-03
l.OE-03
2.0E-01
l.OE-04
5.0E-01
1.4E-03
6.0E-01
8.0E-02
1.4E+00
6.0E-02
l.OE-01
2.0E-02
1.1E+01
5.0E-04
RfD CSFo(per CSFo
Source mg/kg-d) Source Comment
IRIS
8.5E+01 IRIS
IRIS
l.OE+00 HEAST
IRIS
IRIS
SF 7.8E-02 IRIS
IRIS 1.6E+00 IRIS
IRIS
IRIS 1.4E-02 IRIS
IRIS 9.5E-04 IRIS
surr RfD is for methyl
mercury
IRIS
IRIS
1.3E-02 HEAST
IRIS
HEAST
IRIS
intermediate MRL
available
IRIS 7.5E-03 IRIS
HEAST
IRIS
SF
IRIS
1.5E+02 IRIS
5.4E+00 IRIS
(continued)
A-10
-------
IWAIR Technical Background Document
Appendix A
Table A-l. (continued)
IWAIR Constituent Name
N-Nitrosopyrrolidine
o-Dichlorobenzene
o-Toluidine
p-Dichlorobenzene
Phenol
Phthalic anhydride
Propylene oxide
Pyridine
Styrene
Tetrachloroethylene
Toluene
trans- 1 , 3 -Dichloropropylene
Tribromomethane
Trichloroethylene
Trichlorofluoromethane
Triethylamine
Vinyl acetate
Vinyl chloride
Xylenes
RfD RfD CSFo(per CSFo
CASRN (mg/kg-d) Source mg/kg-d) Source
930-55-2 2.1E+00 IRIS
95-50-1 9.0E-02 IRIS
95-53-4 2.4E-01 HEAST
106-46-7 2.4E-02 HEAST
108-95-2 6.0E-01 IRIS
85-44-9 2.0E+00 IRIS
75-56-9 2.4E-01 IRIS
110-86-1 l.OE-03 IRIS
100-42-5 2.0E-01 IRIS
127-18-4 l.OE-02 IRIS 5.2E-02 HAD
108-88-3 2.0E-01 IRIS
10061-02-6 3.0E-02 IRIS l.OE-01 IRIS
75-25-2 2.0E-02 IRIS 7.9E-03 IRIS
79-01-6 1.1E-02 HAD
75-69-4 3.0E-01 IRIS
121-44-8
108-05-4 l.OE+00 HEAST
75-01-4 3.0E-03 IRIS 7.2E-01 IRIS
1330-20-7 2.0E+00 IRIS
Comment
intermediate MRL
available
RfD & CSFo are for
1 ,3 -dichloropropene
CSFo is for
continuous adult
exposure
a Sources:
ATSDR = ATSDR oral minimal risk levels (ATSDR, 200 1)
IRIS = Integrated Risk Information System (U.S. EPA, 200 1)
HEAST = Health Effects Assessment Summary Tables (U.S. EPA, 1997a)
HAD = Health Assessment Document (U.S. EPA, 1986, 1987)
SF = Superfund Risk Issue Paper (U.S. EPA, 1998c, 1999a, 1999b, 2000b)
solvents = 63 FR 64371-0402 (U.S. EPA, 1998a)
surr = surrogate
A-ll
-------
IWAIR Technical Background Document Appendix A
Finally, as noted above, various chemical properties indicative of the potential for indirect
pathway concern are presented in Appendix B for IWAIR chemicals. For other chemicals, the
following sources may be useful:
• EPA' s Superfund Chemical Data Matrix (SCDM) (U. S. EPA, 1 997b)
• The Merck Index (Budavari, 1996)
• The National Library of Medicine's Hazardous Substances Databank (HSDB),
available on TOXNET (U.S. NLM, 2001)
• Syracuse Research Corporation' s CHEMF ATE database (SRC, 1 999)
• CambridgeSoft.com's ChemFinder database (CambridgeSoft, 2001)
• Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological
Profiles (ATSDR, 2001)
• EPA's Dioxin Reassessment (U.S. EPA, 2000a) — for dioxins only
Half-life
• Howard etal. (1991)
Toxicity (in order of preference)
• Integrated Risk Information System (IRIS) (U.S. EPA, 2001)
• Superfund Technical Support Center Provisional Benchmarks (U.S. EPA, 1998c,
1999a, 1999b, 2000b)
• Health Effects Assessment Summary Tables (HEAST) (U.S. EPA, 1997a)
• Agency for Toxic Substances and Disease Registry oral minimal risk levels
(MRLs) (ATSDR, 2001)
• California Environmental Protection Agency (CalEPA) cancer potency factors
(CalEPA, 1999)
• EPA health assessment documents (U.S. EPA, 1986, 1987, 1998a).
A-12
-------
IWAIR Technical Background Document Appendix A
A.4 References
ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Minimal Risk Levels
(MRLs)for Hazardous Substances. http://atsdrl.atsdr.cdc.gov:8080/mrls.html
Budavari, S. (Ed.). 1996. The Merck Index, An Encyclopedia of Chemicals, Drugs, and
Biologicals. 12th Edition. Merck & Co. Inc., Rahway, NJ.
CalEPA (California Environmental Protection Agency). 1999. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part II. Technical Support Document for Describing
Available Cancer Potency Factors. Office of Environmental Health Hazard Assessment,
Berkeley, CA. Available online at http://www.oehha.org/scientific/hsca2.htm.
CambridgeSoft Corporation. 2001. ChemFinder.com database and internet searching.
http://chemfmder.cambridgesoft.com. Accessed July 2001.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, E.M. Michalenko, and H.T. Printup
(Ed.). 1991. Handbook of Environmental Degradation Rates. Lewi s Publi shers,
Chelsea, MI.
Syracuse Research Corporation (SRC). 1999. CHEMFATE Chemical Search, Environmental
Science Center, Syracuse, NY. http://esc.syrres.com/efdb/Chemfate.htm. Accessed July
2001.
U.S. EPA (Environmental Protection Agency). 1986. Addendum to the Health Assessment
Document for Tetrachloroethylene (Perchloroethylene). Updated Carcinogenicity
Assessment for Tetrachloroethylene (Perchloroethylene, PERC, PCE). External Review
Draft. EPA/600/8-82-005FA. Office of Health and Environmental Assessment, Office of
Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1987. Addendum to the Health Assessment
Document for Trichloroethylene. Updated Carcinogenicity Assessment for
Trichloroethylene. External Review Draft. EPA/600/8-82-006FA. Office of Health and
Environmental Assessment, Office of Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1997a. Health Effects Assessment Summary
Tables (HEAST). EPA-540-R-97-036. FY 1997 Update.
U.S. EPA (Environmental Protection Agency). 1997b. Superfund Chemical Data Matrix
(SCDM). Office of Emergency and Remedial Response. Web site at
http://www.epa.gov/oerrpage/superfund/resources/scdm/index.htm. June.
U.S. EPA (Environmental Protection Agency). 1998a. Hazardous waste management system;
identification and listing of hazardous waste; solvents; final rule. Federal Register
63 FR 64371-402.
A-13
-------
IWAIR Technical Background Document Appendix A
U.S. EPA (Environmental Protection Agency). 1998b. Methodology for Assessing Health Risks
Associated with Multiple Pathways of Exposure to Combustor Emissions. Update to
EPA/600/6-90/003 Methodology for Assessing Health Risks Associated with Indirect
Exposure to Combustor Emissions. EPA 600/R-98/137. National Center for
Environmental Assessment, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1998c. Risk Assessment Paper for: Evaluation
of the Systemic Toxicity of Hexachlorobutadiene (CASRN 87-68-3) Resulting from Oral
Exposure. 98-009/07-17-98. National Center for Environmental Assessment. Superfund
Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999a. Risk Assessment Issue Paper for:
Derivation of Provisional Oral Chronic RfD and Subchronic RfDsfor 1,1,1-
Trichloroethane (CASRN 71-55-6). 98-025/8-4-99. National Center for Environmental
Assessment. Superfund Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999b. Risk Assessment Paper for: An Updated
Systemic Toxicity Evaluation of n-Hexane (CASRN 110-54-3). 98-019/10-1-99. National
Center for Environmental Assessment. Superfund Technical Support Center, Cincinnati,
OH.
U.S. EPA (Environmental Protection Agency). 2000a. Exposure and Human Health
Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds.
Part I: Estimating Exposure to Dioxin-Like Compounds. Volume 3—Properties,
Environmental Levels, and Background Exposures. Draft Final Report. EPA/600/P-
00/001. Office of Research and Development, Washington, DC. September.
U.S. EPA (Environmental Protection Agency). 2000b. Risk Assessment Paper for: Derivation
of a Provisional RfD for 1,1,2,2-Tetrachloroethane (CASRN 79-34-5). 00-122/12-20-00.
National Center for Environmental Assessment. Superfund Technical Support Center,
Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 2001. Integrated Risk Information System
(IRIS). National Center for Environmental Assessment, Office of Research and
Development, Washington, DC. Available online at http://www.epa.gov/iris/ Office of
Solid Waste and Emergency Response, Washington, DC.
U.S. NLM (National Library of Medicine). 2001. Hazardous Substances Data Bank (HSDB).
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Accessed July 2001.
A-14
-------
Appendix B
Physical-Chemical Properties
for Chemicals Included in IWAIR
-------
-------
IWAIR Technical Background Document
Appendix B
Appendix B
Physical-Chemical Properties for
Chemicals Included in IWAIR
This appendix presents the physical-chemical property values included in IWAIR and the
sources of those values. Each table provides the data for one chemical; the chemicals are shown
in CAS-number order. The following source references are used throughout:
Calculated based on EPA (1987)
Calculated based on Lyman (1990)
Calculated based on WATER9 (2001)
Calculated based on EPA's Dioxin Reassessment (2000)
CHEMDAT8
Chemfate
ChemFinder
Dioxin Reassessment
Hansch et al. (1995) (unpub)
Howard etal. (1991)
HSDB
Kollig(1993)
KowWIN
Mackay et al. (1992)
Merck
MRTC
SCDM
U.S. EPA (1987)
Lyman etal. (1990)
U.S. EPA (2001)
U.S. EPA (2000)
U.S. EPA (1994)
SRC (2000)
CambridgeSoft(2001)
U.S. EPA (2000)
Hansch etal. (1995)
Howard etal. (1991)
U.S.NLM(2001)
Kollig(1993)
SRC (2001)
Mackay et al. (1992)
Budavari (1996)
U.S. EPA(1997a)
U.S. EPA(1997b)
B-3
-------
IWAIR Technical Background Document
Appendix B
Table B-l. Chemical-Specific Inputs for Formaldehyde (50-00-0)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.1E-01
3.4E-07
-5.0E-02
3.0E+01
5.5E+05
5.2E+03
O.OE+00
1.1E-06
2.5E-01
5.0E+00
7.2E+00
9.7E+02
2.4E+02
1.7E-01
1.7E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B4
-------
IWAIR Technical Background Document
Appendix B
Table B-2. Chemical-Specific Inputs for Benzo(a)pyrene (50-32-8)
Parameter
HLC
LogKow
MW
Sol
VP
Kh
Density
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Density of the chemical
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E-06
6.1E+00
2.5E+02
1.6E-03
5.5E-09
O.OE+00
1.4E+00
1.5E-08
3.1E-01
l.OE-03
9.3E+00
3.7E+03
2.7E+02
2.5E-02
6.6E-06
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
g/cm3
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
HSDB
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-5
-------
IWAIR Technical Background Document
Appendix B
Table B-3. Chemical-Specific Inputs for N-Nitrosodiethylamine (55-18-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.4E-01
3.6E-06
4.8E-01
l.OE+02
9.3E+04
8.6E-01
O.OE+00
4.5E-08
4.5E-01
4.4E+00
O.OE+00
O.OE+00
2.7E+02
7.4E-02
9.1E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-6
-------
IWAIR Technical Background Document
Appendix B
Table B-4. Chemical-Specific Inputs for Carbon tetrachloride (56-23-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.6E+00
3.0E-02
2.7E+00
1.5E+02
7.9E+02
1.2E+02
5.4E-10
2.2E-08
1.5E+00
1.5E+00
6.9E+00
1.2E+03
2.3E+02
5.7E-02
9.8E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-7
-------
IWAIR Technical Background Document
Appendix B
Table B-5. Chemical-Specific Inputs for 3-Methylcholanthrene (56-49-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
9.4E-07
6.4E+00
2.7E+02
3.2E-03
7.7E-09
O.OE+00
5.7E-09
3.1E-01
l.OE-03
8.2E+00
3.4E+03
2.7E+02
2.4E-02
6.1E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-8
-------
IWAIR Technical Background Document
Appendix B
Table B-6. Chemical-Specific Inputs for 7,12-Dimethylbenz[a]anthracene (57-97-6)
Parameter
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Density
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Density of the chemical
Value
3.1E-08
6.6E+00
2.6E+02
2.5E-02
5.6E-09
O.OE+00
2.9E-07
3.1E-01
l.OE-03
7.0E+00
2.2E+03
1.7E+02
4.7E-02
5.5E-06
l.OE+00
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
g/cm3
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on EPA, 1987.
Calculated based on EPA, 1987.
-
B-9
-------
IWAIR Technical Background Document
Appendix B
Table B-7. Chemical-Specific Inputs for Aniline (62-53-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
l.OE+OO
1.9E-06
9.8E-01
9.3E+01
3.6E+04
4.9E-01
O.OE+00
3.6E-07
2.1E+01
7.1E+00
6.9E+00
1.5E+03
1.8E+02
8.3E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-10
-------
IWAIR Technical Background Document
Appendix B
Table B-8. Chemical-Specific Inputs for Methanol (67-56-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
7.9E-01
4.5E-06
-7.1E-01
3.2E+01
l.OE+06
1.3E+02
O.OE+00
1.1E-06
2.0E-01
1.8E+01
7.9E+00
1.5E+03
2.3E+02
1.6E-01
1.7E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-ll
-------
IWAIR Technical Background Document
Appendix B
Table B-9. Chemical-Specific Inputs for Acetone (67-64-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
7.9E-01
3.9E-05
-2.4E-01
5.8E+01
l.OE+06
2.3E+02
O.OE+00
1.1E-06
1.1E+00
1.3E+00
7.1E+00
1.2E+03
2.3E+02
1.1E-01
1.2E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-12
-------
IWAIR Technical Background Document
Appendix B
Table B-10. Chemical-Specific Inputs for Chloroform (67-66-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.5E+00
3.7E-03
1.9E+00
1.2E+02
7.9E+03
2.0E+02
3.2E-12
4.5E-08
7.9E-01
2.8E+01
6.5E+00
9.3E+02
2.0E+02
7.7E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-13
-------
IWAIR Technical Background Document
Appendix B
Table B-ll. Chemical-Specific Inputs for Hexachloroethane (67-72-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.1E+00
3.9E-03
4.0E+00
2.4E+02
5.0E+01
2.1E-01
O.OE+00
4.5E-08
3.1E-02
l.OE-03
7.2E+00
1.4E+03
1.3E+02
3.2E-02
8.9E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-14
-------
IWAIR Technical Background Document
Appendix B
Table B-12. Chemical-Specific Inputs for N,N-Dimethyl formamide (68-12-2)
Parameter
Ksg
Density
Kh
HLC
Sol
VP
LogKow
MW
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Soil degradation rate
Density of the chemical
Hydrolysis rate
Henry's law constant
Solubility
Vapor pressure
Octanol-water partition coeficient
Molecular Weight
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
l.OE-20
9.4E-01
O.OE+00
7.4E-08
l.OE+06
3.7E+00
-l.OE+00
7.3E+01
1.3E-01
9.7E+00
6.9E+00
1.4E+03
2.0E+02
9.7E-02
1.1E-05
Units
sec-1
g/cm3
sec-1
atm-m3/mol
mg/L
mmHg
unitless
g/mol
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
no value for Ksg in existing hierarchy
Merck
Kollig, 1993
HSDB
HSDB
HSDB
Hanschetal., 1995
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-15
-------
IWAIR Technical Background Document
Appendix B
Table B-13. Chemical-Specific Inputs for Benzene (71-43-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.8E-01
5.6E-03
2.1E+00
7.8E+01
1.8E+03
9.5E+01
O.OE+00
5.0E-07
1.4E+00
1.9E+01
6.9E+00
1.2E+03
2.2E+02
8.9E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-16
-------
IWAIR Technical Background Document
Appendix B
Table B-14. Chemical-Specific Inputs for 1,1,1-Trichloroethane (71-55-6)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
1.7E-02
2.5E+00
1.3E+02
1.3E+03
1.2E+02
2.0E-08
2.9E-08
7.4E-01
3.5E+00
6.8E+00
1.2E+03
2.2E+02
6.5E-02
9.6E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-17
-------
IWAIR Technical Background Document
Appendix B
Table B-15. Chemical-Specific Inputs for Methyl bromide (74-83-9)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.7E+00
6.2E-03
1.2E+00
9.5E+01
1.5E+04
1.6E+03
O.OE+00
2.9E-07
3.5E-01
1.1E+01
7.6E+00
1.3E+03
2.7E+02
l.OE-01
1.3E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-18
-------
IWAIR Technical Background Document
Appendix B
Table B-16. Chemical-Specific Inputs for Methyl chloride (74-87-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.1E-01
8.8E-03
9.1E-01
5.0E+01
5.3E+03
4.3E+03
O.OE+00
2.9E-07
7.2E-01
1.1E+01
7.1E+00
9.5E+02
2.5E+02
1.2E-01
1.4E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-19
-------
IWAIR Technical Background Document
Appendix B
Table B-17. Chemical-Specific Inputs for Vinyl chloride (75-01-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.1E-01
2.7E-02
1.5E+00
6.3E+01
2.8E+03
3.0E+03
O.OE+00
4.5E-08
1.4E-01
1.1E+01
7.0E+00
9.7E+02
2.5E+02
1.1E-01
1.2E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-20
-------
IWAIR Technical Background Document
Appendix B
Table B-18. Chemical-Specific Inputs for Acetonitrile (75-05-8)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
7.9E-01
3.5E-05
-3.4E-01
4.1E+01
l.OE+06
9.1E+01
O.OE+00
2.9E-07
l.OE-01
9.7E+00
7.1E+00
1.3E+03
2.3E+02
1.3E-01
1.4E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-21
-------
IWAIR Technical Background Document
Appendix B
Table B-19. Chemical-Specific Inputs for Acetaldehyde (75-07-0)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
7.8E-01
7.9E-05
-4.7E-01
4.4E+01
l.OE+06
9.0E+02
O.OE+00
1.1E-06
2.0E-01
8.2E+01
8.0E+00
1.6E+03
2.9E+02
1.3E-01
1.3E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-22
-------
IWAIR Technical Background Document
Appendix B
Table B-20. Chemical-Specific Inputs for Methylene chloride (75-09-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
2.2E-03
1.3E+00
8.5E+01
1.3E+04
4.3E+02
O.OE+00
2.9E-07
3.8E-01
1.8E+01
7.0E+00
1.1E+03
2.2E+02
l.OE-01
1.3E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-23
-------
IWAIR Technical Background Document
Appendix B
Table B-21. Chemical-Specific Inputs for Carbon disulfide (75-15-0)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Ksg
Kh
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Soil degradation rate
Hydrolysis rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
3.0E-02
2.0E+00
7.6E+01
1.2E+03
3.6E+02
l.OE-20
O.OE+00
8.9E-01
1.5E+01
6.9E+00
1.2E+03
2.4E+02
1.1E-01
1.3E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
no value for Ksg in existing hierarchy
Kollig, 1993
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-24
-------
IWAIR Technical Background Document
Appendix B
Table B-22. Chemical-Specific Inputs for Ethylene oxide (75-21-8)
Parameter
Density
Kh
Sol
Ksg
LogKow
HLC
MW
VP
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Hydrolysis rate
Solubility
Soil degradation rate
Octanol-water partition coeficient
Henry's law constant
Molecular Weight
Vapor pressure
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.9E-01
6.7E-07
l.OE+06
6.8E-07
-3.0E-01
1.5E-04
4.4E+01
1.3E+03
9.1E-01
4.2E+00
7.1E+00
1.1E+03
2.4E+02
1.3E-01
1.5E-05
Units
g/cm3
sec-1
mg/L
sec-1
unitless
atm-m3/mol
g/mol
mmHg
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Merck
Kollig, 1993
HSDB
Howardetal, 1991
Hanschetal., 1995
Chemfate
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-25
-------
IWAIR Technical Background Document
Appendix B
Table B-23. Chemical-Specific Inputs for Tribromomethane (75-25-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.9E+00
5.3E-04
2.4E+00
2.5E+02
3.1E+03
5.5E+00
O.OE+00
4.5E-08
l.OE+00
1.1E+01
8.0E+00
2.2E+03
2.7E+02
3.6E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-26
-------
IWAIR Technical Background Document
Appendix B
Table B-24. Chemical-Specific Inputs for Bromodichloromethane (75-27-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.0E+00
1.6E-03
2.1E+00
1.6E+02
6.7E+03
5.0E+01
O.OE+00
4.5E-08
7.0E-01
1.1E+01
8.0E+00
1.9E+03
2.7E+02
5.6E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-27
-------
IWAIR Technical Background Document
Appendix B
Table B-25. Chemical-Specific Inputs for 1,1-Dichloroethylene (75-35-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
2.6E-02
2.1E+00
9.7E+01
2.3E+03
6.0E+02
O.OE+00
4.5E-08
9.0E-01
1.1E+01
7.0E+00
1.1E+03
2.4E+02
8.6E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-28
-------
IWAIR Technical Background Document
Appendix B
Table B-26. Chemical-Specific Inputs for Propylene oxide (75-56-9)
Parameter
Density
Kh
VP
Ksg
LogKow
HLC
MW
Sol
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Hydrolysis rate
Vapor pressure
Soil degradation rate
Octanol-water partition coeficient
Henry's law constant
Molecular Weight
Solubility
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.6E-01
O.OE+00
5.4E+02
6.5E-07
3.0E-02
1.2E-04
5.8E+01
4.1E+05
1.7E-01
1.8E+01
7.1E+00
1.1E+03
2.4E+02
1.1E-01
1.2E-05
Units
g/cm3
sec-1
mmHg
sec-1
unitless
atm-m3/mol
g/mol
mg/L
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Merck
Kollig, 1993
HSDB
Howardetal, 1991
Hanschetal., 1995
Chemfate
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-29
-------
IWAIR Technical Background Document
Appendix B
Table B-27. Chemical-Specific Inputs for Trichlorofluoromethane (75-69-4)
Parameter
HLC
LogKow
MW
Sol
VP
Density
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Density of the chemical
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.7E-02
2.5E+00
1.4E+02
1.1E+03
8.0E+02
1.5E+00
O.OE+00
2.2E-08
1.2E-01
1.1E+00
6.9E+00
l.OE+03
2.4E+02
6.6E-02
l.OE-05
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
g/cm3
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Merck
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-30
-------
IWAIR Technical Background Document
Appendix B
Table B-28. Chemical-Specific Inputs for Dichlorodifluoromethane (75-71-8)
Parameter
HLC
LogKow
MW
Sol
VP
Density
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Density of the chemical
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
3.4E-01
2.2E+00
1.2E+02
2.8E+02
4.8E+03
1.5E+00
O.OE+00
4.5E-08
6.7E-02
1.1E+00
7.6E+00
1.3E+03
2.7E+02
7.6E-02
1.1E-05
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
g/cm3
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Merck
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-31
-------
IWAIR Technical Background Document
Appendix B
Table B-29. Chemical-Specific Inputs for l,l,2-Trichloro-l,2,2-trifluoroethane (76-13-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.6E+00
4.8E-01
3.2E+00
1.9E+02
1.7E+02
3.3E+02
O.OE+00
2.2E-08
3.1E-02
l.OE-03
8.8E+00
1.9E+03
2.7E+02
3.8E-02
8.6E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-32
-------
IWAIR Technical Background Document
Appendix B
Table B-30. Chemical-Specific Inputs for Hexachlorocyclopentadiene (77-47-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.7E+00
2.7E-02
5.4E+00
2.7E+02
1.8E+00
6.0E-02
7.9E-07
2.9E-07
3.1E-02
l.OE-03
8.4E+00
2.8E+03
2.7E+02
2.7E-02
7.2E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-33
-------
IWAIR Technical Background Document
Appendix B
Table B-31. Chemical-Specific Inputs for Isophorone (78-59-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.3E-01
6.6E-06
1.7E+00
1.4E+02
1.2E+04
4.4E-01
O.OE+00
2.9E-07
6.0E-01
1.5E+01
8.0E+00
2.5E+03
2.7E+02
5.2E-02
7.5E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-34
-------
IWAIR Technical Background Document
Appendix B
Table B-32. Chemical-Specific Inputs for 1,2-Dichloropropane (78-87-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
2.8E-03
2.0E+00
1.1E+02
2.8E+03
5.2E+01
1.5E-09
6.2E-09
1.4E+00
1.7E+01
7.0E+00
1.4E+03
2.2E+02
7.3E-02
9.7E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-35
-------
IWAIR Technical Background Document
Appendix B
Table B-33. Chemical-Specific Inputs for Methyl ethyl ketone (78-93-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.1E-01
5.6E-05
2.8E-01
7.2E+01
2.2E+05
9.5E+01
O.OE+00
1.1E-06
2.0E-01
2.0E+00
7.1E+00
1.3E+03
2.3E+02
9.2E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-36
-------
IWAIR Technical Background Document
Appendix B
Table B-34. Chemical-Specific Inputs for 1,1,2-Trichloroethane (79-00-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.4E+00
9.1E-04
2.0E+00
1.3E+02
4.4E+03
2.3E+01
8.7E-13
2.2E-08
7.4E-01
3.5E+00
7.2E+00
1.5E+03
2.3E+02
6.7E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-37
-------
IWAIR Technical Background Document
Appendix B
Table B-35. Chemical-Specific Inputs for Trichloroethylene (79-01-6)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.5E+00
l.OE-02
2.7E+00
1.3E+02
1.1E+03
7.3E+01
O.OE+00
2.2E-08
8.8E-01
3.9E+00
6.5E+00
l.OE+03
1.9E+02
6.9E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-38
-------
IWAIR Technical Background Document
Appendix B
Table B-36. Chemical-Specific Inputs for Acrylamide (79-06-1)
Parameter
HLC
LogKow
MW
Sol
VP
Density
Kh
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Ksg
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Density of the chemical
Hydrolysis rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Soil degradation rate
Value
l.OE-09
-9.6E-01
7.1E+01
6.4E+05
7.0E-03
1.1E+00
5.7E-10
2.7E-01
9.7E+00
1.1E+01
3.9E+03
2.7E+02
1.1E-01
1.3E-05
2.0E-06
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
g/cm3
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
sec-1
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Merck
Kollig, 1993
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
Calculated based on data in Howard, 1989
B-39
-------
IWAIR Technical Background Document
Appendix B
Table B-37. Chemical-Specific Inputs for Acrylic acid (79-10-7)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E+00
1.2E-07
3.5E-01
7.2E+01
l.OE+06
4.0E+00
O.OE+00
1.1E-06
1.8E-01
1.8E+01
5.7E+00
6.5E+02
1.6E+02
l.OE-01
1.2E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-40
-------
IWAIR Technical Background Document
Appendix B
Table B-38. Chemical-Specific Inputs for 1,1,2,2-Tetrachloroethane (79-34-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.6E+00
3.4E-04
2.4E+00
1.7E+02
3.0E+03
4.6E+00
1.6E-10
1.8E-07
6.8E-01
6.2E+00
6.9E+00
1.4E+03
1.9E+02
4.9E-02
9.3E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-41
-------
IWAIR Technical Background Document
Appendix B
Table B-39. Chemical-Specific Inputs for 2-Nitropropane (79-46-9)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.8E-01
1.2E-04
8.7E-01
8.9E+01
1.7E+04
1.8E+01
O.OE+00
4.5E-08
4.1E-01
9.7E+00
7.3E+00
1.5E+03
2.3E+02
8.5E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B42
-------
IWAIR Technical Background Document
Appendix B
Table B-40. Chemical-Specific Inputs for Methyl methacrylate (80-62-6)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.4E-01
3.4E-04
1.4E+00
l.OE+02
1.5E+04
3.8E+01
O.OE+00
2.9E-07
4.3E+00
1.8E+01
6.5E+00
1.1E+03
1.9E+02
7.5E-02
9.2E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B43
-------
IWAIR Technical Background Document
Appendix B
Table B-41. Chemical-Specific Inputs for Phthalic anhydride (85-44-9)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.5E+00
1.6E-08
-6.2E-01
1.5E+02
6.2E+03
5.2E-04
1.6E-12
4.3E-04
7.8E-02
1.8E+01
8.0E+00
2.9E+03
2.7E+02
5.9E-02
9.7E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B44
-------
IWAIR Technical Background Document
Appendix B
Table B-42. Chemical-Specific Inputs for Hexachloro-l,3-butadiene (87-68-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.6E+00
8.1E-03
4.8E+00
2.6E+02
3.2E+00
2.2E-01
O.OE+00
4.5E-08
3.1E-02
l.OE-03
7.5E+00
2.0E+03
2.2E+02
2.7E-02
7.0E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B45
-------
IWAIR Technical Background Document
Appendix B
Table B-43. Chemical-Specific Inputs for Naphthalene (91-20-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
l.OE+OO
4.8E-04
3.4E+00
1.3E+02
3.1E+01
8.5E-02
O.OE+00
1.7E-07
l.OE+OO
4.3E+01
7.4E+00
2.0E+03
2.2E+02
6.0E-02
8.4E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B46
-------
IWAIR Technical Background Document
Appendix B
Table B-44. Chemical-Specific Inputs for Benzidine (92-87-5)
Parameter
HLC
LogKow
MW
Sol
VP
Kh
Density
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Density of the chemical
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
3.9E-11
1.7E+00
1.8E+02
5.0E+02
8.0E-09
O.OE+00
1.3E+00
l.OE-06
6.6E-01
3.1E+01
7.5E+00
2.6E+03
1.6E+02
3.5E-02
7.6E-06
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
g/cm3
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
HSDB
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B47
-------
IWAIR Technical Background Document
Appendix B
Table B-45. Chemical-Specific Inputs for o-Dichlorobenzene (95-50-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
1.9E-03
3.4E+00
1.5E+02
1.6E+02
1.4E+00
O.OE+00
4.5E-08
5.8E-01
2.5E+00
6.9E+00
1.5E+03
2.1E+02
5.6E-02
8.9E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B48
-------
IWAIR Technical Background Document
Appendix B
Table B-46. Chemical-Specific Inputs for o-Toluidine (95-53-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
l.OE+OO
2.7E-06
1.3E+00
1.1E+02
1.7E+04
3.2E-01
O.OE+00
1.1E-06
8.6E-01
3.1E+01
7.2E+00
1.7E+03
1.9E+02
7.2E-02
9.2E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B49
-------
IWAIR Technical Background Document
Appendix B
Table B-47. Chemical-Specific Inputs for 2-Chlorophenol (95-57-8)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
3.9E-04
2.1E+00
1.3E+02
2.2E+04
2.3E+00
O.OE+00
5.4E-08
8.9E-01
1.5E+01
6.9E+00
1.5E+03
1.9E+02
6.6E-02
9.5E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-50
-------
IWAIR Technical Background Document
Appendix B
Table B-48. Chemical-Specific Inputs for 3,4-Dimethylphenol (95-65-8)
Parameter
Kh
Density
MW
Sol
VP
Ksg
LogKow
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
HLC
Definition
Hydrolysis rate
Density of the chemical
Molecular Weight
Solubility
Vapor pressure
Soil degradation rate
Octanol-water partition coeficient
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Henry's law constant
Value
O.OE+OO
9.8E-01
1.2E+02
4.8E+03
3.6E-02
1.1E-06
2.2E+00
l.OE+00
5.5E+00
7.5E+00
1.9E+03
2.0E+02
6.3E-02
8.4E-06
1.2E-06
Units
sec-1
g/cm3
g/mol
mg/L
mmHg
sec-1
unitless
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
atm-m3/mol
Reference
Kollig, 1993
HSDB
HSDB
HSDB
HSDB
Howardetal, 1991
Hanschetal., 1995
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
Calculated Based on Lyman, 1990.
B-51
-------
IWAIR Technical Background Document
Appendix B
Table B-49. Chemical-Specific Inputs for l,2-Dibromo-3-chloropropane (96-12-8)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.1E+00
1.5E-04
2.3E+00
2.4E+02
1.2E+03
5.8E-01
1.3E-10
4.5E-08
1.6E-01
1.1E+01
8.1E+00
2.4E+03
2.7E+02
3.2E-02
8.9E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-52
-------
IWAIR Technical Background Document
Appendix B
Table B-50. Chemical-Specific Inputs for Furfural (98-01-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Ksg
Kh
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Soil degradation rate
Hydrolysis rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
4.0E-06
4.1E-01
9.6E+01
1.1E+05
2.2E+00
l.OE-20
O.OE+00
5.4E-01
1.8E+01
6.6E+00
1.2E+03
1.6E+02
8.5E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
no value for Ksg in existing hierarchy
Kollig, 1993
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-53
-------
IWAIR Technical Background Document
Appendix B
Table B-51. Chemical-Specific Inputs for Cumene (98-82-8)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.6E-01
1.2E+00
3.6E+00
1.2E+02
6.1E+01
4.5E+00
O.OE+00
l.OE-06
2.9E+00
3.1E+01
7.0E+00
1.5E+03
2.1E+02
6.0E-02
7.8E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-54
-------
IWAIR Technical Background Document
Appendix B
Table B-52. Chemical-Specific Inputs for Nitrobenzene (98-95-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
2.4E-05
1.8E+00
1.2E+02
2.1E+03
2.5E-01
O.OE+00
4.1E-08
2.3E+00
1.1E+01
7.1E+00
1.8E+03
2.0E+02
6.8E-02
9.4E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-55
-------
IWAIR Technical Background Document
Appendix B
Table B-53. Chemical-Specific Inputs for Ethylbenzene (100-41-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.7E-01
7.9E-03
3.1E+00
1.1E+02
1.7E+02
9.6E+00
O.OE+00
8.0E-07
2.1E+00
6.8E+00
7.0E+00
1.4E+03
2.1E+02
6.9E-02
8.5E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-56
-------
IWAIR Technical Background Document
Appendix B
Table B-54. Chemical-Specific Inputs for Styrene (100-42-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.1E-01
2.7E-03
2.9E+00
l.OE+02
3.1E+02
6.1E+00
O.OE+00
2.9E-07
1.1E-01
3.1E+01
6.9E+00
1.4E+03
2.1E+02
7.1E-02
8.8E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-57
-------
IWAIR Technical Background Document
Appendix B
Table B-55. Chemical-Specific Inputs for p-Dichlorobenzene (106-46-7)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
2.4E-03
3.4E+00
1.5E+02
7.4E+01
l.OE+00
O.OE+00
4.5E-08
2.3E+00
6.4E+00
7.2E+00
1.7E+03
2.2E+02
5.5E-02
8.7E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-58
-------
IWAIR Technical Background Document
Appendix B
Table B-56. Chemical-Specific Inputs for 1,2-Epoxybutane (106-88-7)
Parameter
Kh
Density
VP
Ksg
HLC
LogKow
MW
Sol
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Hydrolysis rate
Density of the chemical
Vapor pressure
Soil degradation rate
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
O.OE+OO
8.4E-01
1.8E+02
6.2E-07
1.8E-04
2.6E-01
7.2E+01
9.5E+04
4.8E-01
1.1E+01
6.8E+00
1.1E+03
2.3E+02
9.3E-02
l.OE-05
Units
sec-1
g/cm3
mmHg
sec-1
atm-m3/mol
unitless
g/mol
mg/L
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Kollig, 1993
HSDB
HSDB
Howardetal, 1991
Chemfate
Chemfate
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-59
-------
IWAIR Technical Background Document
Appendix B
Table B-57. Chemical-Specific Inputs for Epichlorohydrin (106-89-8)
Parameter
HLC
LogKow
MW
Sol
VP
Density
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Density of the chemical
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
3.0E-05
2.5E-01
9.3E+01
6.6E+04
1.6E+01
1.2E+00
9.8E-07
2.9E-07
1.4E-01
1.1E+01
8.2E+00
2.1E+03
2.7E+02
8.9E-02
1.1E-05
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
g/cm3
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Merck
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-60
-------
IWAIR Technical Background Document
Appendix B
Table B-58. Chemical-Specific Inputs for Ethylene dibromide (106-93-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.2E+00
7.4E-04
2.0E+00
1.9E+02
4.2E+03
1.3E+01
2.0E-08
4.5E-08
5.5E-01
1.1E+01
7.3E+00
1.7E+03
2.5E+02
4.3E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-61
-------
IWAIR Technical Background Document
Appendix B
Table B-59. Chemical-Specific Inputs for 1,3-Butadiene (106-99-0)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
6.1E-01
7.4E-02
2.0E+00
5.4E+01
7.4E+02
2.1E+03
O.OE+00
2.9E-07
6.9E-01
1.5E+01
7.2E+00
1.1E+03
2.7E+02
l.OE-01
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-62
-------
IWAIR Technical Background Document
Appendix B
Table B-60. Chemical-Specific Inputs for Acrolein (107-02-8)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.4E-01
1.2E-04
-l.OE-02
5.6E+01
2.1E+05
2.7E+02
2.1E+01
2.9E-07
3.4E-01
7.8E+00
7.2E+00
1.3E+03
2.5E+02
1.1E-01
1.2E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-63
-------
IWAIR Technical Background Document
Appendix B
Table B-61. Chemical-Specific Inputs for Allyl chloride (107-05-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.4E-01
1.1E-02
1.5E+00
7.7E+01
3.4E+03
3.7E+02
O.OE+00
5.8E-07
3.1E-01
1.1E+01
7.6E+00
1.5E+03
2.7E+02
9.4E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-64
-------
IWAIR Technical Background Document
Appendix B
Table B-62. Chemical-Specific Inputs for 1,2-Dichloroethane (107-06-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
9.8E-04
1.5E+00
9.9E+01
8.5E+03
7.9E+01
3.0E-10
4.5E-08
9.8E-01
2.1E+00
7.1E+00
1.3E+03
2.3E+02
8.5E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-65
-------
IWAIR Technical Background Document
Appendix B
Table B-63. Chemical-Specific Inputs for Acrylonitrile (107-13-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.1E-01
l.OE-04
2.5E-01
5.3E+01
7.4E+04
1.1E+02
O.OE+00
3.5E-07
7.5E-01
1.8E+01
7.1E+00
1.3E+03
2.4E+02
1.1E-01
1.2E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-66
-------
IWAIR Technical Background Document
Appendix B
Table B-64. Chemical-Specific Inputs for Ethylene glycol (107-21-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E+00
6.0E-08
-1.4E+00
6.2E+01
l.OE+06
9.2E-02
O.OE+00
6.7E-07
6.1E-02
1.8E+01
8.1E+00
2.1E+03
2.0E+02
1.2E-01
1.4E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-67
-------
IWAIR Technical Background Document
Appendix B
Table B-65. Chemical-Specific Inputs for Vinyl acetate (108-05-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.3E-01
5.1E-04
7.3E-01
8.6E+01
2.0E+04
9.0E+01
O.OE+00
1.1E-06
3.1E-01
1.8E+01
7.2E+00
1.3E+03
2.3E+02
8.5E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-68
-------
IWAIR Technical Background Document
Appendix B
Table B-66. Chemical-Specific Inputs for Methyl isobutyl ketone (108-10-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.0E-01
1.4E-04
1.2E+00
l.OE+02
1.9E+04
2.0E+01
O.OE+00
1.1E-06
4.5E-01
7.4E-01
6.7E+00
1.2E+03
1.9E+02
7.0E-02
8.4E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-69
-------
IWAIR Technical Background Document
Appendix B
Table B-67. Chemical-Specific Inputs for Toluene (108-88-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
8.7E-01
6.6E-03
2.8E+00
9.2E+01
5.3E+02
2.8E+01
O.OE+00
3.6E-07
2.4E+00
6.7E+00
6.9E+00
1.3E+03
2.2E+02
7.8E-02
9.2E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-70
-------
IWAIR Technical Background Document
Appendix B
Table B-68. Chemical-Specific Inputs for Chlorobenzene (108-90-7)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E+00
3.7E-03
2.9E+00
1.1E+02
4.7E+02
1.2E+01
O.OE+00
5.4E-08
l.OE+01
3.9E-01
7.0E+00
1.4E+03
2.2E+02
7.2E-02
9.5E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-71
-------
IWAIR Technical Background Document
Appendix B
Table B-69. Chemical-Specific Inputs for Cyclohexanol (108-93-0)
Parameter
Density
Kh
VP
Ksg
LogKow
HLC
MW
Sol
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Hydrolysis rate
Vapor pressure
Soil degradation rate
Octanol-water partition coeficient
Henry's law constant
Molecular Weight
Solubility
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.6E-01
O.OE+00
8.0E-01
4.5E-08
1.2E+00
l.OE-04
l.OE+02
4.3E+04
5.4E-01
1.8E+01
6.3E+00
9.1E+02
1.1E+02
7.6E-02
9.4E-06
Units
g/cm3
sec-1
mmHg
sec-1
unitless
atm-m3/mol
g/mol
mg/L
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Merck
Kollig, 1993
HSDB
Howardetal, 1991
Hanschetal., 1995
Chemfate
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-72
-------
IWAIR Technical Background Document
Appendix B
Table B-70. Chemical-Specific Inputs for Phenol (108-95-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E+00
4.0E-07
1.5E+00
9.4E+01
8.3E+04
2.8E-01
O.OE+00
8.0E-07
1.3E+01
9.7E+01
7.1E+00
1.5E+03
1.8E+02
8.3E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-73
-------
IWAIR Technical Background Document
Appendix B
Table B-71. Chemical-Specific Inputs for 2-Methoxyethanol (109-86-4)
Parameter
Kh
Density
Sol
VP
Ksg
LogKow
HLC
MW
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Hydrolysis rate
Density of the chemical
Solubility
Vapor pressure
Soil degradation rate
Octanol-water partition coeficient
Henry's law constant
Molecular Weight
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
O.OE+OO
9.6E-01
l.OE+06
6.2E+00
2.9E-07
-7.7E-01
8.1E-08
7.6E+01
l.OE+00
2.0E+01
O.OE+OO
O.OE+OO
2.7E+02
9.5E-02
1.1E-05
Units
sec-1
g/cm3
mg/L
mmHg
sec-1
unitless
atm-m3/mol
g/mol
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Kollig, 1993
HSDB
HSDB
HSDB
Howardetal, 1991
Hanschetal., 1995
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-74
-------
IWAIR Technical Background Document
Appendix B
Table B-72. Chemical-Specific Inputs for 2-Methoxyethanol acetate (110-49-6)
Parameter
LogKow
Kh
Density
MW
Sol
VP
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
HLC
Definition
Octanol-water partition coeficient
Hydrolysis rate
Density of the chemical
Molecular Weight
Solubility
Vapor pressure
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Henry's law constant
Value
l.OE-01
O.OE+00
l.OE+00
1.2E+02
l.OE+06
2.0E+00
2.9E-07
l.OE+00
2.0E+01
O.OE+00
O.OE+00
2.7E+02
6.6E-02
8.7E-06
3.1E-07
Units
unitless
sec-1
g/cm3
g/mol
mg/L
mmHg
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
atm-m3/mol
Reference
KowWIN
Kollig, 1993
HSDB
HSDB
HSDB
HSDB
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
Calculated Based on Lyman, 1990.
B-75
-------
IWAIR Technical Background Document
Appendix B
Table B-73. Chemical-Specific Inputs for n-Hexane (110-54-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
6.5E-01
1.4E-02
4.0E+00
8.6E+01
1.2E+01
1.5E+02
O.OE+00
5.0E-07
1.5E+00
1.5E+01
6.9E+00
1.2E+03
2.2E+02
7.3E-02
8.1E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-76
-------
IWAIR Technical Background Document
Appendix B
Table B-74. Chemical-Specific Inputs for 2-Ethoxyethanol (110-80-5)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.3E-01
1.2E-07
-l.OE-01
9.0E+01
l.OE+06
5.3E+00
O.OE+00
2.9E-07
l.OE+00
2.0E+01
7.9E+00
1.8E+03
2.3E+02
8.2E-02
9.8E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-77
-------
IWAIR Technical Background Document
Appendix B
Table B-75. Chemical-Specific Inputs for Pyridine (110-86-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.8E-01
8.9E-06
6.7E-01
7.9E+01
l.OE+06
2.1E+01
O.OE+00
1.1E-06
2.4E-01
3.5E+01
7.0E+00
1.4E+03
2.2E+02
9.3E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-78
-------
IWAIR Technical Background Document
Appendix B
Table B-76. Chemical-Specific Inputs for 2-Ethoxyethanol acetate (111-15-9)
Parameter
LogKow
Kh
Density
HLC
Sol
VP
Ksg
MW
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Octanol-water partition coeficient
Hydrolysis rate
Density of the chemical
Henry's law constant
Solubility
Vapor pressure
Soil degradation rate
Molecular Weight
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
5.9E-01
O.OE+00
9.7E-01
1.8E-06
2.3E+05
2.3E+00
2.9E-07
1.3E+02
l.OE+00
2.0E+01
O.OE+00
O.OE+00
2.7E+02
5.7E-02
8.0E-06
Units
unitless
sec-1
g/cm3
atm-m3/mol
mg/L
mmHg
sec-1
g/mol
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
KowWIN
Kollig, 1993
HSDB
HSDB
HSDB
HSDB
Howardetal, 1991
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-79
-------
IWAIR Technical Background Document
Appendix B
Table B-77. Chemical-Specific Inputs for Hexachlorobenzene (118-74-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.0E+00
1.3E-03
5.9E+00
2.8E+02
5.0E-03
1.8E-05
O.OE+00
3.8E-09
3.1E-02
l.OE-03
9.6E+00
3.3E+03
2.0E+02
2.9E-02
7.8E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-80
-------
IWAIR Technical Background Document
Appendix B
Table B-78. Chemical-Specific Inputs for 1,2,4-Trichlorobenzene (120-82-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.5E+00
1.4E-03
4.0E+00
1.8E+02
3.5E+01
4.3E-01
O.OE+00
4.5E-08
4.4E-01
1.1E+00
7.7E+00
2.2E+03
2.5E+02
4.0E-02
8.4E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-81
-------
IWAIR Technical Background Document
Appendix B
Table B-79. Chemical-Specific Inputs for 2,4-Dinitrotoluene (121-14-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.3E+00
9.3E-08
2.0E+00
1.8E+02
2.7E+02
1.5E-04
O.OE+00
4.5E-08
7.8E-01
9.7E+00
8.0E+00
3.1E+03
2.8E+02
3.7E-02
7.9E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-82
-------
IWAIR Technical Background Document
Appendix B
Table B-80. Chemical-Specific Inputs for Triethylamine (121-44-8)
Parameter
Density
Kh
Ksg
VP
LogKow
HLC
MW
Sol
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Hydrolysis rate
Soil degradation rate
Vapor pressure
Octanol-water partition coeficient
Henry's law constant
Molecular Weight
Solubility
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
7.3E-01
O.OE+00
O.OE+00
5.7E+01
1.5E+00
1.4E-04
l.OE+02
5.5E+04
1.1E+00
9.7E+00
7.0E+00
1.3E+03
2.2E+02
6.6E-02
7.8E-06
Units
g/cm3
sec-1
sec-1
mmHg
unitless
atm-m3/mol
g/mol
mg/L
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Merck
Kollig, 1993
HSDB
HSDB
Hanschetal., 1995
Chemfate
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-83
-------
IWAIR Technical Background Document
Appendix B
Table B-81. Chemical-Specific Inputs for 1,2-Diphenylhydrazine (122-66-7)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
1.5E-06
2.9E+00
1.8E+02
6.8E+01
4.3E-04
O.OE+00
4.5E-08
1.9E+00
1.9E+01
1.4E+01
5.4E+03
2.7E+02
3.4E-02
7.3E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-84
-------
IWAIR Technical Background Document
Appendix B
Table B-82. Chemical-Specific Inputs for 1,4-Dioxane (123-91-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
l.OE+OO
4.8E-06
-3.9E-01
8.8E+01
l.OE+06
3.8E+01
O.OE+00
4.5E-08
3.9E-01
1.8E+01
7.3E+00
1.5E+03
2.4E+02
8.7E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-85
-------
IWAIR Technical Background Document
Appendix B
Table B-83. Chemical-Specific Inputs for Chlorodibromomethane (124-48-1)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
2.5E+00
7.8E-04
2.2E+00
2.1E+02
2.6E+03
4.9E+00
O.OE+00
4.5E-08
3.5E-02
1.1E+01
8.2E+00
2.1E+03
2.7E+02
3.7E-02
1.1E-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-86
-------
IWAIR Technical Background Document
Appendix B
Table B-84. Chemical-Specific Inputs for Chloroprene (126-99-8)
Parameter
Density
LogKow
MW
Sol
VP
Kh
Ksg
HLC
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Henry's law constant
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
9.6E-01
2.1E+00
8.9E+01
1.7E+03
2.1E+02
O.OE+00
4.5E-08
1.2E-02
2.2E-01
1.1E+01
6.2E+00
7.8E+02
1.8E+02
8.4E-02
l.OE-05
Units
g/cm3
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
atm-m3/mol
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-87
-------
IWAIR Technical Background Document
Appendix B
Table B-85. Chemical-Specific Inputs for Tetrachloroethylene (127-18-4)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.6E+00
1.8E-02
2.7E+00
1.7E+02
2.0E+02
1.9E+01
O.OE+00
2.2E-08
6.8E-01
6.2E+00
7.0E+00
1.4E+03
2.2E+02
5.1E-02
9.4E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-88
-------
IWAIR Technical Background Document
Appendix B
Table B-86. Chemical-Specific Inputs for 1,1,1,2-Tetrachloroethane (630-20-6)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.5E+00
2.4E-03
2.6E+00
1.7E+02
1.1E+03
1.2E+01
4.3E-10
1.2E-07
6.8E-01
6.2E+00
6.9E+00
1.4E+03
1.9E+02
4.8E-02
9.1E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-89
-------
IWAIR Technical Background Document
Appendix B
Table B-87. Chemical-Specific Inputs for N-Nitrosodi-n-butylamine (924-16-3)
Parameter
HLC
LogKow
MW
Sol
VP
Kh
Density
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Density of the chemical
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
3.2E-04
2.4E+00
1.6E+02
1.3E+03
3.0E-02
O.OE+00
9.0E-01
4.5E-08
l.OE+00
l.OE-04
O.OE+00
O.OE+00
2.7E+02
4.2E-02
6.8E-06
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
g/cm3
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
HSDB
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-90
-------
IWAIR Technical Background Document
Appendix B
Table B-88. Chemical-Specific Inputs for N-Nitrosopyrrolidine (930-55-2)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E+00
1.2E-08
-1.9E-01
l.OE+02
l.OE+06
9.2E-02
O.OE+00
4.5E-08
l.OE+00
l.OE-04
O.OE+00
O.OE+00
2.7E+02
8.0E-02
l.OE-05
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-91
-------
IWAIR Technical Background Document
Appendix B
Table B-89. Chemical-Specific Inputs for Cresols (total) (1319-77-3)
Parameter
Density
HLC
LogKow
MW
Sol
VP
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.1E+00
9.5E-07
2.0E+00
1.1E+02
2.3E+04
1.8E-01
O.OE+00
2.8E-07
1.7E+01
2.3E+01
8.9E+00
2.8E+03
2.7E+02
7.4E-02
9.5E-06
Units
g/cm3
atm-m3/mol
unitless
g/mol
mg/L
mmHg
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-92
-------
IWAIR Technical Background Document
Appendix B
Table B-90. Chemical-Specific Inputs for Xylenes (1330-20-7)
Parameter
HLC
LogKow
MW
Sol
VP
Density
Kh
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Henry's law constant
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Density of the chemical
Hydrolysis rate
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
6.7E-03
3.2E+00
1.1E+02
1.8E+02
8.0E+00
8.7E-01
O.OE+00
2.9E-07
1.8E+00
4.1E+01
7.9E+00
2.1E+03
2.7E+02
6.9E-02
8.5E-06
Units
atm-m3/mol
unitless
g/mol
mg/L
mmHg
g/cm3
sec-1
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Merck
Kollig, 1993
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-93
-------
IWAIR Technical Background Document
Appendix B
Table B-91. Chemical-Specific Inputs for Methyl tert-butyl ether (1634-04-4)
Parameter
Kh
Density
VP
Ksg
LogKow
HLC
MW
Sol
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Hydrolysis rate
Density of the chemical
Vapor pressure
Soil degradation rate
Octanol-water partition coeficient
Henry's law constant
Molecular Weight
Solubility
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
O.OE+OO
7.4E-01
2.5E+02
4.5E-08
9.4E-01
5.9E-04
8.8E+01
5.1E+04
7.1E-01
1.8E+01
6.8E+00
1.1E+03
2.2E+02
7.5E-02
8.6E-06
Units
sec-1
g/cm3
mmHg
sec-1
unitless
atm-m3/mol
g/mol
mg/L
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Kollig, 1993
HSDB
HSDB
Howardetal, 1991
Hanschetal., 1995
Chemfate
Chemfate
Chemfate
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-94
-------
IWAIR Technical Background Document
Appendix B
Table B-92. Chemical-Specific Inputs for 2,3,7,8-TCDD (1746-01-6)
Parameter
Density
Ksg
HLC
Kh
LogKow
MW
Sol
VP
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Dw
Da
Definition
Density of the chemical
Soil degradation rate
Henry's law constant
Hydrolysis rate
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusion coefficient in water
Diffusivity of chemical in air
Value
1.8E+00
1.4E-08
3.3E-05
O.OE+00
6.8E+00
3.2E+02
1.9E-05
1.5E-09
3.1E-02
l.OE-03
7.0E+00
2.4E+03
1.6E+02
6.8E-06
4.7E-02
Units
g/cm3
sec-1
atm-m3/mol
sec-1
unitless
g/mol
mg/L
mmHg
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
Mackay et al, 1992
Howardetal, 1991
Dioxin Reassessment
Dioxin Reassessment
Dioxin Reassessment
Dioxin Reassessment
Dioxin Reassessment
Dioxin Reassessment
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on EPA's Dioxin Reassessment, 2000.
B-95
-------
IWAIR Technical Background Document
Appendix B
Table B-93. Chemical-Specific Inputs for Mercury (7439-97-6)
Parameter
Density
Kh
Ksg
HLC
LogKd
MW
Sol
VP
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Dw
Da
Definition
Density of the chemical
Hydrolysis rate
Soil degradation rate
Henry's law constant
soil-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusion coefficient in water
Diffusivity of chemical in air
Value
1.4E+01
O.OE+00
O.OE+00
7.1E-03
3.0E+00
2.0E+02
5.6E-02
2.0E-03
l.OE+00
l.OE-04
O.OE+00
O.OE+00
2.7E+02
3.0E-05
5.5E-02
Units
g/cm3
sec-1
sec-1
atm-m3/mol
unitless
g/mol
mg/L
mmHg
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
not applicable for metallic species
not applicable for metallic species
MRTC
MRTC
MRTC
Merck
Merck
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on EPA, 1987.
B-96
-------
IWAIR Technical Background Document
Appendix B
Table B-94. Chemical-Specific Inputs for Divalent mercury (7439-97-7)
Parameter
Kh
Ksg
HLC
LogKd
MW
Sol
Density
VP
Dw
Da
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Definition
Hydrolysis rate
Soil degradation rate
Henry's law constant
soil-water partition coeficient
Molecular Weight
Solubility
Density of the chemical
Vapor pressure
Diffusion coefficient in water
Diffusivity of chemical in air
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Value
O.OE+OO
O.OE+00
7.1E-10
4.8E+00
2.0E+02
7.4E+04
5.6E+00
l.OE+00
1.8E-05
5.5E-02
Units
sec-1
sec-1
atm-m3/mol
unitless
g/mol
mg/L
g/cm3
mmHg
cm2/s
cm2/s
Reference
not applicable for metallic species
not applicable for metallic species
MRTC
MRTC
MRTC
Merck
HSDB
HSDB
Calculated based on WATER9, 2001.
Calculated based on EPA, 1987.
B-97
-------
IWAIR Technical Background Document
Appendix B
Table B-95. Chemical-Specific Inputs for cis-l,3-Dichloropropylene (10061-01-5)
Parameter
Density
LogKow
MW
Sol
VP
Kh
HLC
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Henry's law constant
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
2.0E+00
1.1E+02
2.7E+03
3.3E+01
1.3E-06
2.4E-03
7.1E-07
7.6E-01
1.1E+01
6.8E+00
1.3E+03
2.3E+02
7.6E-02
l.OE-05
Units
g/cm3
unitless
g/mol
mg/L
mmHg
sec-1
atm-m3/mol
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
HSDB
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-98
-------
IWAIR Technical Background Document
Appendix B
Table B-96. Chemical-Specific Inputs for trans-l,3-Dichloropropylene (10061-02-6)
Parameter
Density
LogKow
MW
Sol
VP
Kh
HLC
Ksg
Kl
Kmax
VP Coeff A
VPCoeffB
VP Coeff C
Da
Dw
Definition
Density of the chemical
Octanol-water partition coeficient
Molecular Weight
Solubility
Vapor pressure
Hydrolysis rate
Henry's law constant
Soil degradation rate
Aqueous degradation rate (low)
Aqueous degradation rate (max)
Antoine's coefficient A
Antoine's coefficient B
Antoine's coefficient C
Diffusivity of chemical in air
Diffusion coefficient in water
Value
1.2E+00
2.0E+00
1.1E+02
2.7E+03
2.3E+01
1.3E-06
1.8E-03
7.1E-07
7.6E-01
1.1E+01
6.8E+00
1.3E+03
2.3E+02
7.6E-02
l.OE-05
Units
g/cm3
unitless
g/mol
mg/L
mmHg
sec-1
atm-m3/mol
sec-1
L/g-hr
mg VO/g-hr
K
K
K
cm2/s
cm2/s
Reference
SCDM
SCDM
SCDM
SCDM
SCDM
Kollig, 1993
HSDB
Howardetal, 1991
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8 or degradation database for CHEMDAT6
CHEMDAT8
CHEMDAT8
CHEMDAT8
Calculated based on WATER9, 2001.
Calculated based on WATER9, 2001.
B-99
-------
IWAIR Technical Background Document Appendix B
References
Budavari, S. (ed.). 1996. The Merck Index, An Encyclopedia of Chemicals, Drugs, and
Biologicals. 12th edition. Merck & Co. Inc., Rahway, NJ.
CambridgeSoft Corporation. 2001. ChemFinder.com database and internet searching.
http://chemfmder.cambridgesoft.com. Accessed July 2001.
Hansch, C., A. Leo, and D. Hoekman. 1995. Exploring QSAR -Hydrophobic, Electonic, and
Steric Constants. Washington, DC: American Chemical Society.
Howard, P.H. 1989. Handbook of Environmental Fate and Exposure Data for Organic
Chemicals, Volume I - Large Production and Priority Pollutants. Lewis Publishers,
Chelsea, MI.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, E.M.Michalenko, and H.T. Printup
(ed.). 1991. Handbook of 'Environmental Degradation Rates. Lewis Publishers, Chelsea,
MI.
Kollig, H.P. 1993. Environmental Fate Constants for Organic Chemicals Under Consideration
for EPA's Hazardous Waste Identification Projects. EPA/600/R-93/132., Athens, GA.
August.
Lyman,WJ., W.F. Reehl, and D.H. Rosenblatt. 1990. Handbook of Chemical Property
Estimation Methods: Environmental Behavior of Organic Compounds. American
Chemical Society, Washington, DC.
Mackay, D., W.Y. Shiu, and K.C. Ma. 1992. Illustrated Handbook of Physical-Chemical
Properties and Environmental Fate for Organic Chemicals. Volume II: Polynuclear
Aromatic Hydrocarbons, PolychlorinatedDioxins, andDibenzofurans. Lewis Publishers,
Boca Raton, FL. pp. 430, 524.
SRC (Syracuse Research Corporation). 2000. CHEMFATE Chemical Search. Environmental
Research Center, Syracuse, NY. Website at http://esc-
plaza.syrres.com/efdb/Chemfate.htm.
SRC (Syracuse Research Corporation). 2001. KowWin. Environmental Research Center,
Syracuse, NY. Website at http://esc.syrres.com/interkow/kowdemo.html. Accessed
October 2001.
U.S. EPA (Environmental Protection Agency). 1987. Processes, Coefficients, andModelsfor
Simulating Toxic Organics and Heavy Metals in Surface Waters. EPA/600/3-87/015.
Environmental Research Laboratory, Athens, GA. June.
U.S. EPA (Environmental Protection Agency). 1994. Air Emissions Models for Waste and
Wastewater. EPA-453/R-94-080-A Appendix C. OAQPS, RTF, NC.
B-100
-------
IWAIR Technical Background Document Appendix B
U.S. EPA (Environmental Protection Agency). 1997'a. Mercury Study Report to Congress.
Volume III - Fate and Transport of Mercury in the Environment. EPA 452/R-97/005.
Office of Air Quality Planning and Standards and Office of Research and Development,
Washington, DC.
U.S. EPA (Environmental Protection Agency). 1997b. Superfund Chemical Data Matrix
(SCDM). Office of Emergency and Remedial Response, Website at
http://www.epa.gov/oerrpage/superfund/resources/scdm/index.htm. June.
U.S. EPA (Environmental Protection Agency). 2000. Exposure and Human Health Reassessment
of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. Parti:
Estimating Exposure to Dioxin-Like Compounds. Volume 3 -Properties, Environmental
Levels, and Background Exposures. Draft Final Report. EPA/600/P-00/001. Office of
Research and Development, Washington, DC. September.
U.S. EPA (Environmental Protection Agency). 2001. WATER9. Version 1.0.0. Office of Air
Quality Planning and Standards, Research Triangle Park, NC. Website at
http://www.epa.gov/ttn/chief/software.html. May 1.
U.S. NLM (National Library of Medicine). 2001. Toxicology Data Network (TOXNET)
Hazardous Substances Data Bank. Website at http://toxnet.nlm.nih.gov. April 18.
B-101
-------
-------
Appendix C
Sensitivity Analysis of ISCST3 Air
Dispersion Model
-------
-------
IWAIR Technical Background Document Appendix C
Appendix C
Sensitivity Analysis of ISCST3 Air
Dispersion Model
This appendix describes the sensitivity analysis performed on depletion options, source
shape and orientation, and receptor location and spacing.
C.I Options with and without Depletion
A sensitivity analysis was conducted using the ISCST3 model to determine whether the
wet depletion option should be used when developing dispersion factors for IWAIR. A
discussion of the analysis follows.
The wet depletion option may be used when estimating air concentrations with ISCST3.
The concentrations modeled without depletion are higher than those modeled with depletion.
Because it takes much longer to run the ISCST3 model with wet depletion than without wet
depletion, a sensitivity analysis was performed to investigate the differences in estimated air
concentrations with and without selecting wet depletion.
In this investigation, the 5th and the 95th percentile of sizes of land application units were
used to determine the relationship between concentrations with depletions and sizes of units;
those areas are 1,200 m2 and 1,700,000 m2, respectively.
Two meteorological stations representing a wet location and a dry location were selected
for the sensitivity analysis: Atlanta, Georgia, with 49.8 inches precipitation per year (a relatively
high annual precipitation rate), and Winnemucca, Nevada, with 8.1 inches precipitation per year
(a relatively low annual precipitation rate). The reason for selecting a wet site and a dry site was
to examine (1) whether wet depletion has a more significant impact for a wet site than a dry site;
and (2) the differences in ambient concentrations that a very wet site can make with and without
selecting wet depletion.
Annual average concentrations with and without wet depletion also were calculated using
5 years of meteorological data from Atlanta and Winnemucca for the 5th and 95th percentile of
areas of land application units. The results show that the differences in the maximum
concentrations with and without wet depletion are small for both locations. However, the
C-3
-------
IWAIR Technical Background Document Appendix C
differences in the maximum concentrations between those calculated with wet depletion and
those calculated without wet depletion are about 5 to 10 times greater for the wet site (Atlanta)
than the dry site (Winnemuca). Tables C-la and C-lb show that for the 95th percentile unit size,
at 50 meters from the edge of the unit, the differences in the maximum concentrations are only
0.03 percent and 0.37 percent for Winnemucca and Atlanta, respectively. This means that model
concentrations with and without wet depletion are about the same.
C-4
-------
Table C-la. Differences in Values of Vapor Air Concentration Calculated with Wet Depletion and without Wet Depletion
(Atlanta, GA Site)
5th Percentile
w/o wet depletion
Distance Concentrations
(m) (ug/ni / g/ni -s)
19.3 (1)
47.3 (1)
75.2 (1)
100
103.2 (1)
187.0 (1)
200
300
400
500
600
800
1000
1500
2000
3000
4000
5000
10000
7.40752
0.93175
0.38178
0.25129
0.21003
0.06886
0.07091
0.03390
0.02026
0.01359
0.00981
0.00590
0.00400
0.00205
0.00128
0.00068
0.00044
0.00031
0.00011
w/ wet depletion
Concentrations
(ug/ni / g/ni -s)
7.40716
0.93159
0.38168
0.25121
0.20996
0.06882
0.07086
0.03387
0.02024
0.01357
0.00979
0.00589
0.00399
0.00205
0.00128
0.00067
0.00043
0.00031
0.00011
Difference
(ug/m /g/m-s)
0.00036
0.00016
0.00010
0.00008
0.00007
0.00004
0.00005
0.00003
0.00002
0.00002
0.00002
0.00001
0.00001
0.00000
0.00000
0.00001
0.00001
0.00000
0.00000
Difference in
Percentage
0.005%
0.017%
0.026%
0.032%
0.033%
0.058%
0.071%
0.088%
0.099%
0.147%
0.204%
0.169%
0.250%
0.000%
0.000%
1.471%
2.273%
0.000%
0.000%
95th Percentile
w/o wet depletion
Distance Concentrations
(m) (ug/ni / g/ni -s)
651.9 (1)
676.9 (1)
701.9 (1)
726.9 (1)
801.9 (1)
1000
1100
1200
1300
1400
1500
1600
1800
2000
3000
4000
5000
10000
0.00614
0.00574
0.00539
0.00507
0.00427
0.00400
0.00342
0.00296
0.00260
0.00230
0.00205
0.00185
0.00152
0.00128
0.00068
0.00044
0.00031
0.00011
w/ wet depletion
Concentrations
(ug/ni / g/ni -s)
0.00612
0.00573
0.00537
0.00505
0.00426
0.00399
0.00341
0.00295
0.00259
0.00229
0.00205
0.00184
0.00152
0.00128
0.00067
0.00043
0.00031
0.00011
Difference
(ug/ni / g/ni -s)
0.00002
0.00001
0.00002
0.00002
0.00001
0.00001
0.00001
0.00001
0.00001
0.00001
0.00000
0.00001
0.00000
0.00000
0.00001
0.00001
0.00000
0.00000
Difference in
Percentage
0.33%
0.17%
0.37%
0.39%
0.23%
0.25%
0.29%
0.34%
0.38%
0.43%
0.00%
0.54%
0.00%
0.00%
1.47%
2.27%
0.00%
0.00%
These refer to the distances from the center of emission source to the maximum concentration points along 0, 25, 50, 75, and 150 meter receptor squares, respectively.
o
-------
Table C-lb. Differences in Values of Vapor Air Concentration Calculated with Wet Depletion and without Wet Depletion
(Winnemucca, NV Site)
5th Percentile
w/o wet depletion
Distance Concentrations
(m) (ug/m / g/m -s)
17.3 (1)
423(V>
613(l)
923(l)
100
167.3 (1)
200
300
400
500
600
800
1000
1500
2000
3000
4000
5000
10000
7.79132
1.08468
0.48369
0.27965
0.24315
0.09949
0.07296
0.03600
0.02181
0.01475
0.01070
0.00649
0.00443
0.00229
0.00144
0.00077
0.00050
0.00036
0.00013
w/ wet depletion
Concentrations
(ug/m / g/m -s)
7.79125
1.08464
0.48367
0.27963
0.24313
0.09948
0.07295
0.03599
0.02180
0.01474
0.01070
0.00648
0.00443
0.00229
0.00144
0.00077
0.00050
0.00036
0.00013
Difference
(ug/m / g/m -s)
0.00007
0.00004
0.00002
0.00002
0.00002
0.00001
0.00001
0.00001
0.00001
0.00001
0.00000
0.00001
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
Difference in
Percentage
0.001%
0.004%
0.004%
0.007%
0.008%
0.010%
0.014%
0.028%
0.046%
0.068%
0.000%
0.154%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
95th Percentile
w/o wet depletion
Distance Concentrations
(m) (ug/m / g/m -s)
651.9 (1)
676.9 (1)
701.9(1)
726.9 (1)
801.9(1)
1000
1100
1200
1300
1400
1500
1600
1800
2000
3000
4000
5000
10000
23.14326
13.86979
11.62889
10.25373
7.84900
5.85241
4.69239
3.98357
3.43255
2.99083
2.63019
2.33211
1.93762
1.65686
0.91889
0.61160
0.45013
0.17843
w/ wet depletion
Concentrations
(ug/m / g/m -s)
23.13885
13.86551
11.62486
10.24985
7.84548
5.84988
4.68991
3.98130
3.43045
2.98887
2.62837
2.33042
1.93554
1.65487
0.91727
0.61020
0.44890
0.17767
Difference
(ug/m / g/m -s)
0.00441
0.00428
0.00403
0.00388
0.00352
0.00253
0.00248
0.00227
0.00210
0.00196
0.00182
0.00169
0.00208
0.00199
0.00162
0.00140
0.00123
0.00076
Difference in
Percentage
0.02%
0.03%
0.03%
0.04%
0.04%
0.04%
0.05%
0.06%
0.06%
0.07%
0.07%
0.07%
0.11%
0.12%
0.18%
0.23%
0.27%
0.43%
(i)
These refer to the distances from the center of emission source to the maximum concentration points along 0, 25, 50, 75, and 150 meter receptor squares, respectively.
-------
IWAIR Technical Background Document Appendix C
C.2 Source Shape and Orientation
A sensitivity analysis was conducted using the ISCST3 air model to determine what role
source shape and orientation play in determining dispersion coefficients of air pollutants. A
discussion of this analysis follows.
Three different sources were chosen for this analysis. The sources were a square (Source
No. 1), a rectangle oriented east to west (Source No. 2), and a rectangle oriented north to south
(Source No. 3). All three sources had an area of 400 m2 in order to ensure that equal emission
rates were compared. The rectangles were selected to be exactly two times longer and half as
wide as the square (see Figure C-l).
Two meteorological stations. Little Rock, Arkansas, and Los Angeles, California, were
selected for this modeling analysis in order to compare two different meteorological regimes.
Little Rock was selected because of its evenly distributed wind directions, and Los Angeles was
selected because it has a predominantly southwest wind direction (see Figure C-2). Five years of
meteorological data were used for this analysis.
Each area source was modeled with similar receptor grids to ensure consistency. Sixteen
receptors were placed on the edge of each of the area sources, and another 16 were placed 25 m
out from the edge. Each of these two receptor groups were modeled as a Cartesian receptor grid.
Two receptor rings were also placed at 50 and 100 m out from the center of the source. This
polar receptor grid consisted of 16 receptors with a 22.5° interval between receptors. See
Figures C-3a through C-3c for receptor locations.
The ISCST3 model was run using the meteorological data from Little Rock, Arkansas,
and Los Angeles, California, and the results are shown in Tables C-2a and C-2b. The results
indicated that the standard deviation of the differences in air concentrations is greatest between
the two rectangular source shapes (source No. 2 and source No. 3). This difference is due to the
orientation of the source. This occurs for both the Cartesian receptor grid and the polar receptor
grid at both meteorological locations. This shows that the model is sensitive to the orientation of
the rectangular area source.
Standard deviations are significantly smaller when the square source (Source No. 1) is
compared with either rectangular source (Source No. 2 or 3). This shows that the differences in
dispersion factors between the square source and the two rectangular sources are less than the
differences between the two rectangular sources. A square area source also contributes the least
amount of impact of orientation. Because the dispersion factors in IWAIR must applicable to a
variety of source shapes and orientations, a square source will minimize the errors caused by
different source shapes and orientations.
C-7
-------
IWAIR Technical Background Document
Appendix C
(meters)
Figure C-l. Source shapes and orientations.
-------
IWAIR Technical Background Document
Appendix C
Los Angeles, California
NNW
NW
NE
WNW
ENE
ESE
Little Rock, Arkansas
NNW
NW
NE
WNW
W
WSW
ENE
ESE
sw
Figure C-2. Wind roses.
C-9
-------
IWAIR Technical Background Document
Appendix C
(meters)
Figure C-3a. Receptor locations (Source No. 1).
(meters)
Figure C-3b. Receptor locations (Source No. 2).
C-10
-------
IWAIR Technical Background Document
Appendix C
-50 0 50
(meters)
Figure C-3c. Receptor locations (Source No. 3).
C-ll
-------
O
i
to
Table C-2a. Comparisons of Dispersion Factors (ug/m31 ug/s-m2) for Different Source Shapes and Orientations
(Little Rock, Arkansas)
Source No. 1 (20m x 20m)
Source No. 2 (40m x 10m)
Source No. 3 (10m x 40m)
Polar Receptor Grid
X(m) Y(m) UAC X(m) Y (m) UAC X (m) Y (m) UAC
19 46 0.190
38 92 0.050
35 35 0.249
71 71 0.067
46 19 0.321
92 38 0.095
50 0 0.124
100 0 0.030
46 -19 0.085
92 -38 0.023
35 -35 0.106
71 -71 0.030
19 -46 0.117
38 -92 0.033
0 -50 0.1 2
0 -100 0.0 5
-19 -46 0.1 4
-38 -92 0.0 8
-35 -35 0.161
-71 -71 0.043
-46 -19 0.159
-92 -38 0.044
-50 0 0.103
-100 0 0.027
-46 19 0.126
-92 38 0.035
-35 35 0.152
-71 71 0.041
-19 46 0.173
-38 92 0.047
0 50 0.224
0 100 0.068
19 46 0.199
38 92 0.051
35 35 0.243
71 71 0.067
46 19 0.361
92 38 0.098
50 0 0.128
100 0 0.030
46 -19 0.096
92 -38 0.024
35 -35 0.109
71 -71 0.030
19 -46 0.113
38 -92 0.032
0 -50 0.117
0 -100 0.033
-19 -46 0.128
-38 -92 0.036
-35 -35 0.158
-71 -71 0.043
-46 -19 0.185
-92 -38 0.046
-50 0 0.114
-100 0 0.027
-46 19 0.145
-92 38 0.036
-35 35 0.160
-71 71 0.042
-19 46 0.179
-38 92 0.047
0 50 0.191
0 100 0.061
19 46 0.211
38 92 0.051
35 35 0.278
71 71 0.069
46 19 0.256
92 38 0.088
50 0 0.147
100 0 0.033
46 -19 0.084
92 -38 0.023
35 -35 0.103
71 -71 0.029
19 -46 0.128
38 -92 0.034
0 -50 0.143
0 -100 0.037
-19 -46 0.150
-38 -92 0.038
-35 -35 0.170
-71 -71 0.045
-46 -19 0.140
-92 -38 0.043
-50 0 0.107
-100 0 0.027
-46 19 0.118
-92 38 0.034
-35 35 0.153
-71 71 0.041
-19 46 0.187
-38 92 0.048
0 50 0.276
0 100 0.074
Standard Deviation:
Differences in UACs
Sources No. 1 and No. 2
Differences in UACs
Sources No. 1 and No. 3
Differences in UACs
Sources No. 2 and No. 3
Diff. In UAC "/oofDiff. Diff. In UAC "/oofDiff. Diff. In UAC "/oofDiff.
0.010 5%
0.001 1%
-0.007 -3%
-0.001 -1%
0.041 1 %
0.003 %
0.004 %
0.000 - %
0.011 1 %
0.001 %
0.003 %
0.000 0%
-0.005 -4%
-0.001 -4%
-0.005 -4%
-0.002 -5%
-0.006 -4%
-0.002 -4%
-0.003 -2%
0.000 1%
0.026 16%
0.002 4%
0.011 11%
0.000 2%
0.019 15%
0.001 4%
0.008 5%
0.001 3%
0.007 4%
0.000 0%
-0.032 -14%
-0.008 -11%
0.012 7%
0.021 11%
0.001 2%
0.028 11%
0.001 2%
-0.065 -20%
-0.007 -7%
0.023 19%
0.003 9%
-0.001 -1%
-0.001 -2%
-0.003 -3%
0.000 -1%
0.011 9%
0.001 2%
0.021 17%
0.002 5%
0.016 12%
0.001 2%
0.009 6%
0.001 3%
-0.019 -12%
-0.002 -4%
0.004 4%
0.000 1%
-0.008 -6%
-0.001 -4%
0.001 0%
0.001 2%
0.014 8%
0.001 3%
0.052 23%
0.006 9%
0.018 9%
0.012 6%
0.000 1%
0.035 14%
0.002 3%
-0.105 -29%
-0.010 -10%
0.020 15%
0.003 11%
-0.011 -12%
-0.001 -5%
-0.006 -6%
-0.001 -2%
0.016 14%
0.002 7%
0.026 22%
0.004 11%
0.022 17%
0.002 6%
0.012 8%
0.001 3%
-0.045 -24%
-0.004 -8%
-0.007 -6%
0.000 0%
-0.027 -18%
-0.003 -7%
-0.007 -5%
-0.001 -2%
0.008 4%
0.001 3%
0.085 44%
0.014 22%
0.028 14%
(continued)
-------
Table C-2a. (continued)
Source No. 1 (20m x 20m)
Source No. 2 (40m x 10m)
Source No. 3 (10m x 40m)
Cartesion Receptor Grid
X(m) Y(m) UAC X(m) Y (m) UAC X(m) Y (m) UAC
-10 -10 3.014
-5 -10 4.266
0 -10 4.354
5 -10 3.961
10 -10 2.175
10 -5 5.211
10 0 5.968
10 5 6.012
10 10 4.946
5 10 6.804
0 10 6.846
-5 10 6.157
-10 10 3.245
-10 5 4.923
-10 0 5.169
-10 -5 4.809
-35 -35 0.164
-17.5 -35 0.219
0 -35 0.243
17.5 -35 0.186
35 -35 0.108
35 -17.5 0.141
35 0 0.277
35 17.5 0.503
35 35 0.254
17.5 35 0.315
0 35 0.417
-17.5 35 0.272
-35 35 0.155
-35 17.5 0.211
-35 0 0.213
-35 -17.5 0.265
-20 -5 2.675
-10 -5 4.219
0 -5 4.307
10 -5 4.069
20 -5 1.899
20 -2.5 3.875
20 0 4.704
20 2.5 4.918
20 5 4.468
10 5 6.758
0 5 6.830
-10 5 6.353
-20 5 2.793
-20 2.5 3.801
-20 0 4.032
-20 -2.5 3.727
-45 -30 0.158
-22.5 -30 0.247
0 -30 0.284
22.5 -30 0.192
45 -30 0.088
45 -15 0.105
45 0 0.164
45 15 0.396
45 30 0.263
22.5 30 0.373
0 30 0.445
-22.5 30 0.286
-45 30 0.131
-45 15 0.155
-45 0 0.145
-45 -15 0.193
-5 -20 2.673
-2.5 -20 3.451
0 -20 3.526
2.5 -20 3.152
5 -20 2.011
5 -10 5.567
5 0 5.913
5 10 5.834
5 20 4.344
2.5 20 5.550
0 20 5.604
-2.5 20 4.954
-5 20 3.052
-5 10 5.166
-5 0 5.287
-5 -10 4.991
-30 -45 0.132
-15 -45 0.167
0 -45 0.179
15 -45 0.147
30 -45 0.100
30 -22.5 0.160
30 0 0.401
30 22.5 0.466
30 45 0.200
15 45 0.234
0 45 0.341
-15 45 0.214
-30 45 0.146
-30 22.5 0.232
-30 0 0.298
-30 -22.5 0.264
Standard Deviation:
Differences in UACs
Sources No. 1 and No. 2
Differences in UACs
Sources No. 1 and No. 3
Differences in UACs
S ources No. 2 and No. 3
Diff. In UAC %ofDiff. Diff. In UAC %ofDiff. Diff. In UAC %ofDiff.
-0.339 -11%
-0.047 -1%
-0.047 -1%
0.109 3%
-0.276 -13%
-1.337 -26%
-1.264 -21%
-1.094 -18%
-0.477 -10%
-0.047 -1%
-0.016 0%
0.196 3%
-0.451 -14%
-1.121 -23%
-1.137 -22%
-1.081 -22%
-0.006 -4%
0.027 12%
0.041 17%
0.006 3%
-0.020 -19%
-0.036 -25%
-0.113 -41%
-0.107 -21%
0.009 3%
0.058 18%
0.028 7%
0.014 5%
-0.024 -15%
-0.056 -27%
-0.068 -32%
-0.073 -27%
0.463 15%
-0.341 -11%
-0.815 -19%
-0.827 -19%
-0.809 -20%
-0.164 -8%
0.355 7%
-0.055 -1%
-0.178 -3%
-0.602 -12%
-1.254 -18%
-1.242 -18%
-1.203 -20%
-0.193 -6%
0.244 5%
0.118 2%
0.182 4%
-0.032 -19%
-0.052 -24%
-0.063 -26%
-0.039 -21%
-0.008 -7%
0.019 14%
0.124 45%
-0.037 -7%
-0.054 -21%
-0.081 -26%
-0.076 -18%
-0.057 -21%
-0.009 -6%
0.022 10%
0.084 40%
-0.002 -1%
0.435 17%
-0.002 0%
-0.769 -18%
-0.781 -18%
-0.918 -23%
0.112 6%
1.692 44%
1.209 26%
0.916 19%
-0.125 -3%
-1.208 -18%
-1.226 -18%
-1.399 -22%
0.259 9%
1.365 36%
1.255 31%
1.264 34%
-0.026 -16%
-0.079 -32%
-0.104 -37%
-0.045 -23%
0.012 14%
0.055 52%
0.236 144%
0.070 18%
-0.063 -24%
-0.139 -37%
-0.104 -23%
-0.071 -25%
0.015 11%
0.078 50%
0.153 106%
0.071 37%
0.747 41%
(continued)
-------
Table C-2b. Comparisons of Dispersion Factors (ug/m31
(Los Angeles,
ug/s-m2) for Different Source Shapes and Orientations
California)
Source No. 1 (20m x 20m)
Source No. 2 (40m x 10m)
Source No. 3 (10m x 40m)
Polar Receptor Grid
X(m) Y(m) UAC X(m) Y (m) UAC X(m) Y (m) UAC
19 46 0.059
38 92 0.016
35 35 0.188
71 71 0.046
46 19 0.582
92 38 0.172
50 0 0.278
100 0 0.068
46 -19 0.061
92 -3S 0.015
35 -35 0.062
71 -71 0.016
19 -46 0.080
38 -92 0.023
0 -50 0.086
0 -100 0.023
-19 -46 0.099
-38 -92 0.028
-35 -35 0.122
-71 -71 0.033
-46 -19 0.218
-92 -38 0.060
-50 0 0.320
-100 0 0.093
-46 19 0.264
-92 38 0.074
-35 35 0.137
-71 71 0.037
-19 46 0.063
-38 92 0.017
0 50 0.067
0 100 0.020
19 46 0.065
38 92 0.016
35 35 0.168
71 71 0.045
46 19 0.607
92 38 0.174
50 0 0.293
100 0 0.067
46 -19 0.062
92 -38 0.015
35 -35 0.068
71 -71 0.017
19 -46 0.076
38 -92 0.022
0 -50 0.084
0 -100 0.024
-19 -46 0.092
-38 -92 0.027
-35 -35 0.119
-71 -71 0.032
-46 -19 0.223
-92 -38 0.061
-50 0 0.378
-100 0 0.098
-46 19 0.273
-92 38 0.075
-35 35 0.123
-71 71 0.035
-19 46 0.066
-38 92 0.017
0 50 0.058
0 100 0.018
19 46 0.069
38 92 0.016
35 35 0.284
71 71 0.052
46 19 0.461
92 38 0.161
50 0 0.293
100 0 0.074
46 -19 0.087
92 -38 0.016
35 -35 0.062
71 -71 0.017
19 -46 0.087
38 -92 0.024
0 -50 0.096
0 -100 0.024
-19 -46 0.108
-38 -92 0.028
-35 -35 0.143
-71 -71 0.034
-46 -19 0.226
-92 -38 0.061
-50 0 0.278
-100 0 0.087
-46 19 0.260
-92 38 0.073
-35 35 0.164
-71 71 0.039
-19 46 0.073
-38 92 0.018
0 50 0.080
0 100 0.021
Standard Deviation:
Differences in UACs
S ources No. 1 and No. 2
Differences in UACs
Sources No. 1 and No. 3
Differences in UACs
S ources No. 2 and No. 3
Diff. In UAC %of Diff. Diff. In UAC %of Diff. Diff. In UAC %of Diff.
0.006 9%
0.000 -1%
-0.020 -11%
-0.001 -3%
0.025 4%
0.003 2%
0.014 5%
-0.001 -2%
0.002 3%
0.000 0%
0.006 10%
0.001 4%
-0.004 -4%
-0.001 -5%
-0.003 -3%
0.000 1%
-0.006 -7%
-0.001 -2%
-0.003 -2%
0.000 -1%
0.005 2%
0.001 1%
0.057 18%
0.005 6%
0.009 3%
0.001 1%
-0.014 -10%
-0.002 -5%
0.003 4%
0.000 -2%
-0.008 -12%
-0.002 -9%
0.013 6%
0.010 17%
0.000 3%
0.096 51%
0.006 13%
-0.121 -21%
-0.011 -6%
0.015 5%
0.005 8%
0.026 43%
0.002 10%
0.000 0%
0.001 3%
0.007 9%
0.001 3%
0.009 11%
0.001 3%
0.009 9%
0.000 1%
0.021 18%
0.001 4%
0.008 4%
0.001 1%
-0.042 -13%
-0.006 -6%
-0.005 -2%
-0.001 -2%
0.027 20%
0.002 4%
0.010 15%
0.001 3%
0.014 21%
0.001 6%
0.030 14%
0.005 7%
0.001 4%
0.116 69%
0.007 16%
-0.146 -24%
-0.014 -8%
0.001 0%
0.007 10%
0.025 40%
0.002 11%
-0.006 -9%
0.000 -1%
0.011 14%
0.002 8%
0.012 15%
0.000 2%
0.016 17%
0.001 3%
0.024 20%
0.002 5%
0.003 2%
0.000 0%
-0.099 -26%
-0.011 -11%
-0.013 -5%
-0.002 -2%
0.041 33%
0.003 9%
0.007 11%
0.001 5%
0.022 37%
0.003 15%
0.040 18%
(continued)
-------
IWAIR Technical Background Document
Appendix C
HI
1/3
UJ ^
C g
Terences
rces No. 2
5 §
CO
»m
— "O
.s s
u 6
C Z
s «
«IS U
5 §
cc
B N
•^
s §
u o
e z
5 §
cc
^
Q
o
U
c
5
t
_
o
3
c
t
Q
!—
_
U
c
if
Q
^^^?^^^^^^S5m^^^Sm^o^^^^?mS^^^^^
-Hrjrjm^^t^^m^^rj^t^mmm^^^ooTMpMpm^^^^^
£25dSs"S5£^SSSS^5SS^252-SS5SS^^5
i T1 T1 T1 i ° i iT1 °i i i ,000 ooo
-^-^xOxOxO 0^0^0^0^0^0^0^0^0-^-^-^-^-^xO 0^^^0^0^0^0^0^0 0 0
^SSS^mS^SSS£SSS^SSSSig222SSSSSgi
**^m^^^^^M^m* = = ^i««*^ = «^MM^N^*^m
-g-SS55;^SS^^S-"-2SSS^""S-S25S--5
ooooO-oo0rtrtrt0ooo0000oooo00000ooo
£
«
0
^
s
o
5
0
•a
s
•g
a
o
w
' — '
ji
U
a>
f^
«
H
V
e
s
s
o
£
o
•^I
X
g
o
o
z
9
o
O!
"g1
o
X
g
o
^
^
o
z
a
o
IK
"g1
X
g
o
G-
^
o
z
U
9
o
IK
o
z
«
^
o
cc
2
o
o
a.
Q
t2
c
o
Q
t.
R
U
U
^
^
if
o
U
>^
^^
_§
>
s
X
U
^
S
ix
J
X
U
^
^_^
_£
ix
^
^
X
So5S°^^'^^SmrJrfo5:'~-'^2!Nr5o^^'-"°rfS25S''"^^
omm^R^l^^^^^^l^do^^^^oooo^^^^^odo
i i i i iii i i i i iii
^^o^^o^^^^m^rs^t-^^^^o^^^^^rNO^^om^
(Nmr^rJ^-n-n-n^-^-^-^-rJ-n-n-noooooooooooooooo
v~> m m ^
i(N^(xq(-^^(N i i i |T)' ^=—>, — ^(DT)T)T)T)' — i ' ' f^l f^l f^l f^l
'
^^^^^^^^.^^^^^^^oo^^^^-^^t-^^-^^-o^o^rJ^
r^S-Noo'nS^-Noo^S^'^-HirjO^^-H-HOOrnPirj-H-H-H-Hr^'^-N
m ^t TI- m >— i^l-m^omoooor^r^mmmoooooooooooooooo
^^^^^^0^(n(nininin'^0^^^^^^^0^ooooo.n0^
I(N ^ "^ "^ '
OO OOOOOOO OOOOO
-------
IWAIR Technical Background Document Appendix C
C.3 Receptor Locations and Spacings
A sensitivity analysis was conducted using the ISCST3 model to determine the impact of
receptor locations and spacings on estimated air concentrations. A discussion of the analysis
follows.
Because it takes a substantial amount of time for the ISCST3 model to execute, it was
necessary to choose a limited number of receptors to be represented in the dispersion factor
database in IWAIR. The larger the number of receptor points, the longer the run time. However,
modeling fewer receptors may result in the omission of the maximum point for assessing
exposure impacts. Therefore, a sensitivity analysis was conducted to determine the number of
receptors needed to adequately capture maximum air concentrations and to locate ideal receptor
placements.
A wind rose was plotted for each of the 60 meteorological stations to be included in
IWAIR for a 5-year time period in order to choose two meteorological stations for this sensitivity
analysis. The stations at Little Rock, Arkansas, and Los Angeles, California, were selected. The
wind roses show that Little Rock has very evenly distributed wind directions, and Los Angeles
has a predominant southwest to west wind (Figure C-2). Little Rock and Los Angeles were
chosen to determine if a higher density of receptors should be placed downwind of a site near Los
Angeles, as compared to a site near Little Rock. Similarly, the 5th, 50th, and 95th percentile of
areas of land application units were used in the sensitivity analysis to determine the extent of
which the area of the unit affects receptor locations and spacings. The areas of the 5th, 50th, and
95th percentile of sizes of land application units are 1,200 m2, 100,000 m2, and 1,700,000 m2,
respectively.
The dispersion modeling was conducted using two sets of receptor grids. The first set of
receptor points (Cartesian receptor grid) was placed around the modeled source with distances of
0, 25, 50, 75, and 150 m from the edge of the unit. Square-shaped, ground-level area sources
were used in the modeling. Therefore, these receptors are located on five squares surrounding
the source. The second set of receptor points (polar receptor grid) was placed outside of the first
set of receptors to 10 km from the center of the source. Because the ISCST3 model's area source
algorithm does not consider elevated terrain, receptor elevations were not entered in the
modeling.
In this sensitivity analysis, both downwind and lateral receptor spacings were investigated
for the three unit sizes using 5 years of meteorological data from Little Rock and Los Angeles.
For the first set of receptor points (i.e., Cartesian receptor grid), five downwind distances of 0,
25, 50, 75, and 150 m from the edge of the source were used. For lateral receptor spacing,
choices of 64, 32, and 16 equally spaced receptor points for each square were used in the
modeling to identify the number of receptors needed to adequately characterize the maximum
impacts (see Figures C-4a through C-4c for Cartesian receptor locations and spacings ((50th
percentile)). For the second set of receptor points (i.e., polar receptor grid), about 20 downwind
distances (i.e., receptor rings) were used. Receptor lateral intervals of 22.5° and 10° were used to
determine whether 22.5° spacing can adequately characterize the maximum impacts. With a
C-16
-------
IWAIR Technical Background Document Appendix C
22.5° interval, there are 16 receptors on each ring. There are 36 receptors on each ring for the
10° interval. See Figures E-5a and C-5b for polar receptor locations (5th percentile).
The results (Figures C-6a through C-6f) show that the maximum downwind
concentrations decrease sharply from the edge of the area source to 150 m from the source. The
maximum concentrations decrease more sharply for a smaller area source than for a larger one.
This means that more close-to-source receptors are generally needed for a small area source than
for a large one.
The results also show that the maximum impacts are generally higher for a dense receptor
grid (i.e., 64 or 32 receptors on each square) than for a scattered receptor grid (i.e., 16 receptors
on each square). However, the differences of the maximum receptor impacts are not significant
between a dense and a scattered receptor grid (Figures C-6a through C-6f). The above
conclusions apply to both Little Rock and Los Angeles. This means that the distribution of wind
directions does not play an important role in determining receptor lateral spacings.
Figures C-7a through C-7f compare the maximum concentrations at each ring for 22.5°
and 10° intervals. The results show that the differences of the maximum concentrations are
greater for close-to-source receptors than for more distant receptors, and the differences are
greater for larger area sources than for smaller area sources. The differences of the maximum
concentrations for 22.5° and 10° intervals are generally small, and the concentrations tend to be
the same at 10 km. The conclusions were drawn from both Little Rock and Los Angeles
meteorological data.
C-17
-------
IWAIR Technical Background Document
Appendix C
-400 -300
200 300 400
-300
-200
100-| -[ |-100
Land Application Unit
-100-1
-200- " tj.****^****^*****^* " h200
-300-
400 1 1 1 1 1 1 1 1—400
400 -300 -200 -100 0 100 200 300 400
(meters)
Figure C-4a. Cartesian receptor grid (64 receptors each square).
-400 -300 -200 -100 0 100 200 300 400
00J 1 1 1 1 1 1 1
300-| + + + + + + + + +
+ + + + + + + + + |-200
100-| + +
1—200
-400 -300 -200 -100
100 200 300 400
(meters)
Figure C-4b. Cartesian receptor grid (32 receptors each square).
C-18
-------
IWAIR Technical Background Document
Appendix C
LiidApglrnnUn
(meters)
Figure C-4c. Cartesian receptor grid (16 receptors each square).
C-19
-------
IWAIR Technical Background Document
Appendix C
-1000 -800 -600 -400 -200
200 400 600 800 1000
—I 1 1 1 k»o
-1000 -800 -600 -400 -200 0 200 400 600 800 1000
(meters)
Figure C-5a. Polar receptor grid (22.5 degree).
-1000 -800 -600 -400 -20(
200 400 600 800 10(
800-
600-
400-
200-
-200-
-400-
-600-
-800-
.mnn-
-
* *
*
* • * *. * \ *****/*.* * • *
+ + ++ +++++"" +
+ +++ +++ +
+
+ + + + +
+
-800
-600
-400
—200
—200
—400
—600
—800
— mnn
-600 -400 -200 0 200 400
(meters)
Figure C-5b. Polar receptor grid (10 degree).
C-20
-------
IWAIR Technical Background Document
Appendix C
•Sfc
A
10
8
6
4
2
0
• 64 receptors
•32 receptors
16 receptors
50 100 150
Distance from the edge of the unit (m)
200
Figure C-6a. Maximum concentrations, Cartesian grid
(5th percentile area, land application unit, Los Angeles, CA).
20
•Sfc
A
0
\
- 64 receptors
-32 receptors
16 receptors
0 50 100 150
Distance from the edge of the unit (m)
200
Figure C-6b. Maximum concentrations, Cartesian grid
(50th percentile area, land application unit, Los Angeles, CA).
C-21
-------
IWAIR Technical Background Document
Appendix C
O
U
•Sfc
A
30
10
0
• 64 receptors
•32 receptors
16 receptors
0 50 100 150
Distance from the edge of the unit (m)
200
Figure C-6c. Maximum concentrations, Cartesian grid
(95th percentile area, land application unit, Los Angeles, CA).
°p p
1 b
a ^s.
S 2
5§ 0
£A ^^ n±n^r.
16 receptors
0 50 100 150 200
Distance from the edge of the unit (m)
Figure C-6d. Maximum concentrations, Cartesian grid
(5th percentile area, land application unit, Little Rock, AR).
C-22
-------
IWAIR Technical Background Document
Appendix C
90 -r
^ ^u
^ 15
E
a A in
o if IU
1 0
\
\
^^
£A ^^ ,_4-«_n
16 receptors
0 50 100 150 200
Distance from the edge of the unit (m)
Figure C-6e. Maximum moncentrations, Cartesian grid
(50th percentile area, land application unit, Little Rock, AR).
30
20
•
10
0
- 64 receptors
-32 receptors
16 receptors
0 50 100 150
Distance from the edge of the unit (m)
200
Figure C-6f. Maximum concentrations, Cartesian grid
(95th percentile area, land application unit, Little Rock, AR).
C-23
-------
IWAIR Technical Background Document
Appendix C
a
o
U
0.6
0.5
0.4
0-3
°'2
0.1
0.0
•22.5 "Interval
•10° Interval
0 2000 4000 6000 8000 10000
Distance from the edge of the unit (m)
Figure C-7a. Maximum concentrations, polar grid
(5th percentile area, land application unit, Los Angeles, CA).
5.0
4.0
3.0
2.0
1-0
0.0
•22.5 "Interval
•10° Interval
0
2000 4000 6000 8000 10000
Distance from the edge of the unit (m)
Figure C-7b. Maximum concentrations, polar grid
(50th percentile area, land application unit, Los Angeles, CA).
C-24
-------
IWAIR Technical Background Document
Appendix C
^-^
^
.8
C A
o 5f
.8
A
10 ______________________________
8 -
6 -
4 -
2
j
i
\
\
V
\^
^••••••^^^^
* — ~-
T"> CO T«^-^«.,T^.1
1 0° Tntrn-nl
i i i i
0 2000 4000 6000 8000 10000
Distance from the edge of the unit (m)
Figure C-7c. Maximum concentrations, polar grid
(95th percentile area, land application unit, Los Angeles, CA).
0
•22.5° Interval
•10° Interval
2000 4000 6000 8000 10000
Distance from the edge of the unit (m)
Figure C-7d. Maximum concentrations, polar grid
(5th percentile area, land application unit, Little Rock, AR).
C-25
-------
IWAIR Technical Background Document
Appendix C
^ A n i
^^ t.u
*e ? 0
g O.VJ
a A o n
o if ^-u
1 1 0
•Sfc
^ 0.0 -
(
OO £ ° T f 1
i l ()u Intrrvil
I
1
V^
D 2000 4000 6000 8000 10000
Distance from the edge of the unit (m)
Figure C-7e. Maximum concentrations, polar grid
(50th percentile area, land application unit, Little Rock, AR).
« 8 1
^ R
S D
a A 4
o if ^
^ n
I
\
V
"^
TO 10 T 1
1 fl° Tntrrvil
^^ u i i i i
0 2000 4000 6000 8000 10000
Distance from the edge of the unit (m)
Figure C-7f. Maximum concentrations, polar grid
(95th percentile area, land application unit, Little Rock, AR).
C-26
-------
Appendix D
Selection of Meteorological Stations
-------
-------
IWAIR Technical Background Document Appendix D
Appendix D
Selection of Meteorological Stations
Meteorological data for more than 200 meteorological stations in the United States are
available on the SCRAM Bulletin Board (http://www.epa.gov/scram001) and from a number of
other sources. Because of the time required to develop dispersion factors, it was not feasible to
include dispersion factors in IWAIR for all of these stations. Therefore, EPA developed an
approach to select a subset of these stations for use in IWAIR. This approach considers the
factors most important for the inhalation pathway risk modeling done by IWAIR.
The approach used involved two main steps:
1. Identify contiguous areas that are sufficiently similar with regard to the parameters
that affect dispersion that they can be reasonably represented by one
meteorological station. The parameters used were
• Surface-level meteorological data (e.g., wind patterns and atmospheric
stability)
• Physiographic features (e.g., mountains, plains)
• Bailey's ecoregions and subregions
• Land cover (e.g., forest, urban areas).
2. For each contiguous area, select one meteorological station to represent that area.
The station selection step considered the following parameters:
Industrial activity
Population density
Location within the area
Years of meteorological data available
Average wind speed.
These steps are described in the following sections.
D-3
-------
IWAIR Technical Background Document Appendix D
D.I Identify Contiguous Areas
A hierarchical procedure based on features affecting wind flow was used to divide the
country into regions. The primary delineation of areas was based on geographic features
affecting synoptic (broad area) winds, including mountain ranges and plains. These features are
also known as physiography. Data were obtained from Fenneman and Johnson (1946),
Wahrhaftig (1965), and State of Hawaii (1997). The secondary delineation was based on features
affecting mesoscale (10 to 1,000 km) winds, including coastal regions and basic land cover
classifications of forest, agriculture, and barren lands. These land cover features were obtained
from U.S. Geological Survey (1999).
The methodology for identifying contiguous areas used wind data and atmospheric
stability data derived from surface-level meteorological data as the primary consideration,
modified by physiography, Bailey's ecoregions and subregions, and land cover. The approach
focused on how well the wind speed and direction and atmospheric stability patterns measured at
a surface-level meteorological station represented the surrounding area. The limit of appropriate
representation varied by area of the country and was substantially determined by terrain and
topography. For example, a station in the Midwest, where topography and vegetation are
uniform, may adequately represent a very large area, while a mountainous station, where ridges
and valleys affect the winds, may represent a much smaller area.
D.I.I Primary Grouping on Wind-Rose and Atmospheric Stability Data
The surface-level meteorological data were downloaded from EPA's SCRAM Web site
(www.epa.gov/scram001). SCRAM has these data for 1984 to 1991. A 5-year period is
commonly used to obtain an averaged depiction of the winds for each station; 5 years covers
most of the usual variation in meteorological conditions. EPA selected a single 5-year period
(1986 to 1990) from the middle of the available period for the purpose of comparing wind roses.
A single period provided consistency across stations. Not all stations had 5 years of data in this
time period. Three years of data was considered a desirable minimum; therefore, stations that
had less than 3 years of data during this time period were not considered for selection. A total of
223 stations in the contiguous 48 states were considered, plus 17 in Alaska, 3 in Hawaii, and 1 in
Puerto Rico.
Two types of wind data were considered: wind directionality and wind speed. Wind
directionality describes the tendency of winds to blow from many different directions (weakly
directional) or primarily from one direction (strongly directional). Strongly directional winds
will tend to disperse air pollutants in a consistent direction, resulting in higher air concentrations
in that direction and higher overall maximum air concentrations. Weakly directional winds will
tend to disperse pollutants in multiple directions, resulting in lower air concentrations in any one
direction and lower overall maximum air concentration.
Wind speed also affects dispersion. A greater average wind speed tends to disperse
pollutants more quickly, resulting in lower air concentrations than lower average wind speeds
would produce. Wind speed was used in the station selection process, but not to identify
contiguous areas of the country.
D-4
-------
IWAIR Technical Background Document Appendix D
A wind rose is a graphical depiction of the frequency of wind speeds by wind direction
(see Figure D-l). Wind roses were produced from the surface-level meteorological data for each
station using WRPLOT (available from www.epa.gov/scram001/models/relat/wrplot.zip).
Winds are plotted in 16 individual directions; thus, if every direction has the same frequency, the
wind would blow from each direction 6.25 percent of the time. Based on the wind roses, each
station was assigned to one of four bins based on the frequency of wind in the predominant
direction (the direction from which the wind blows the greatest percentage of the time). These
bins were as follows:
• W, weakly directional: blowing from the predominant direction less than
10 percent of the time
• A, mildly directional: blowing from the predominant direction 10 to 14 percent of
the time
• B, moderately directional: blowing from the predominant direction 15 to
20 percent of the time
• C, strongly directional: blowing from the predominant direction more than
20 percent of the time.
Atmospheric stability class frequency distributions were also used for some stations.
Atmospheric stability is a measure of vertical movement of air and can be classified as stable,
unstable, or neutral. For sources at ground level and slightly elevated (i.e., not tall stacks), such
as are modeled in IWAIR, pollutants tend to stay close to the ground in a stable atmosphere,
thereby increasing the air concentration of the pollutant. In an unstable atmosphere, the
pollutants will tend to disperse more in the vertical direction, thereby decreasing the air
concentration of the pollutant. Atmospheric stability varies throughout the day and year, as well
as by location, because atmospheric stability is determined from variable factors such as wind
speed, strength of solar radiation, and the vertical temperature profile above the ground. In
addition, the presence of large bodies of water, hills, large urban areas, and types and height of
vegetation all affect atmospheric stability. If all other factors are the same at two stations, the
one with stable air a larger percentage of the time will have higher air concentrations than the
station with stable air a smaller percentage of the time.
Stability class distributions were readily available for only 108 of the 223 stations
considered for the United States. To apply the stability class data, the distributions were
summarized as percent unstable, percent neutral, and percent stable.
All stations with their assigned wind-rose bins and stability class distributions were
marked on a map and then grouped geographically with others nearby with the same or an
adjacent assigned bin and a similar stability class distribution. Figure D-l illustrates the
usefulness of this approach with respect to wind-rose data. It shows the 1992 wind roses for
eight cities in Texas and Louisiana. A visual inspection of these graphics reveals that the wind
patterns for these stations differ significantly.
D-5
-------
IWAIR Technical Background Document
Appendix D
Houston, Texas, 1992.
Corpus Christi, Texas, 1992.
San Antonio, Texas, 1992.
Dallas/Ft. Worth, Texas, 1992.
New Orleans, Louisiana, 1992.
Baton Rouge, Louisiana, 1992.
Shreveport, Louisiana, 1992.
Lake Charles, Louisiana, 1992.
Figure D-l. Wind-rose data for Texas and Louisiana.
D-6
-------
IWAIR Technical Background Document Appendix D
D.1.2 Secondary Grouping Considerations
After spatially grouping the wind roses in similar bins, the next step was to delineate
geographic areas around these groups of meteorological stations using maps of physiography,
Bailey's ecoregions, and land cover. Physiography includes major topographic features, such as
mountains or plains. Land cover classifications include urban, crop land, grassland, forest, large
waterbody, wetland, barren, and snow or ice. Regional boundaries were chosen to coincide with
physiographic, Bailey's ecoregion, and land cover boundaries to the extent possible.
D.2 Station Selection
The above approach used to delineate contiguous areas ensures that the stations grouped
together are fairly similar in most cases. Therefore, the selection of an appropriate station to
represent each area was based on other considerations, including
• Previous EPA work on meteorological station selection. Earlier efforts already
identified stations that were representative of broad regions.
• Number of years of surface-level meteorological data available. More years of
data provide a more realistic long-term estimate of air concentration.
• Industrial activity, based on TRI facility locations. More industrial activity
suggests these locations are representative of more potential IWAIR users.
• Population density, based on land cover data. High population density in urban
areas indicates more potential receptors; therefore, these are areas EPA would like
to represent very well, so as to minimize potential error and uncertainty.
• Central location within the area. All other factors being equal, central locations
are more likely to be representative of the entire contiguous geographic area
because they have the smallest average distance from all points in the region.
• Wind speed. Lower wind speeds lead to less dispersion and higher air
concentrations.
EPA considered two previous studies covering meteorological station selection. An
assessment for EPA's Superfund program Soil Screening Levels (SSLs) (EQM and Pechan,
1993) selected a set of 29 meteorological stations as being representative of the nine general
climate regions of the contiguous 48 states. In EPA's SSL study, it was determined that
29 meteorological stations would be a sufficient sample to represent the population of 200
meteorological stations and predict mean dispersion values with a high (95 percent) degree of
confidence. The 29 meteorological stations were distributed among nine climate regions based
on meteorological representativeness and variability across each region. These 29 stations have
been used in a variety of EPA studies. The 2001 Surface Impoundment Study (SIS) (U.S. EPA,
2001) added 12 stations to the list of 29 for assessment of inhalation risks.
D-7
-------
IWAIR Technical Background Document Appendix D
Industrial activity was based on a map of the locations of the WMUs in the 1985
Industrial D database (Schroeder et al., 1987) and facilities listing on-site land disposal-based
emissions in the 1998 TRI (U.S. EPA, 2000). Population density was considered by identifying
urban areas on the land cover map. Wind speed was summarized as average speed in the
prevailing wind direction. This value is not readily extractable from the wind roses; therefore, it
was obtained from the International Station Meteorological Climate Summary CD (NO AA,
1992) of meteorological data. For a few stations, this value was unreal!stically low; in those
cases, an average wind speed in the prevailing wind direction was estimated from the wind rose
data.
EPA used a hierarchical procedure to select a representative station, as follows:
• If the area contained one of the 29 SSL stations, it was selected.
• If the area contained one of the stations added to the SSL list for the SIS, it was
selected.
• Stations with less than 5 years of data in SCRAM were eliminated, unless no
station had 5 years of data.
• Stations in locations with greater industrial activity (as indicated by TRI facilities
reporting on-site land-based disposal) or greater population (based on urban areas
from land cover maps) were preferred.
• Stations centrally located in the area were preferred if the above factors did not
identify a clear choice.
• If all other factors were equal, stations with lower average wind speeds were
selected to ensure that air concentration was not underestimated. Variations in
wind speed within regions were minor.
D.3 New Meteorological Station Boundaries by Region
As a result of this work, the list of 60 stations shown in Table D-l, sorted by state and
station name, was chosen for use in IWAIR. Appendix D-l provides additional data on all of the
meteorological stations considered. Selection of the stations is discussed in the following
sections; for purposes of that discussion, the United States was divided into the following
sections: West Coast, Desert Southwest, Western Mountains, Texas (excluding the Gulf Coast),
Gulf Coast, Southeast, Middle Atlantic, Northeast, Great Lakes, Central States, Alaska, Hawaii,
and Puerto Rico. The process of selecting stations and delineating the region assigned to each
station is discussed by these sections.
Figure D-2 shows the selected stations and their assigned regions for the contiguous 48
states. Figures D-3, D-4, and D-5 show these boundaries on a larger scale for the western,
southeastern, and northeastern United States overlaid on the location of facilities from the 1998
TRI data. The Bailey's ecoregions, physiographic features, and land cover were instrumental in
D-8
-------
IWAIR Technical Background Document
Appendix D
Table
Station
Number
26451
25309
13963
23183
93193
23174
24257
23234
23062
14740
12839
12842
13874
03813
22521
94910
24131
94846
03937
12916
13957
14764
94847
14840
14922
13994
13865
24033
03812
13722
D-l. Surface-Level Meteorology Stations
Station Name
Anchorage/WSMO Airport
Juneau/International Airport
Little Rock/ Adams Field
Phoenix/Sky Harbor International Airport
Fresno/Air Terminal
Los Angeles/International Airport
Redding/ AAF
San Francisco/International Airport
Denver/Stapleton International Airport
Hartford/Bradley International Airport
Miami/International Airport
Tampa/International Airport
Atlanta/ Atlanta-Hartsfield International
Macon/Lewis B Wilson Airport
Honolulu/International Airport
Waterloo/Municipal Airport
Boise/Air Terminal
Chicago/OHare International Airport
Lake Charles/Municipal Airport
New Orleans/International Airport
Shreveport/Regional Airport
Portland/International Jetport
Detroit/Metropolitan Airport
Muskegon/County Airport
Minneapolis-St Paul/International Airport
St. Louis/Lambert International Airport
Meridian/Key Field
Billings/Logan International Airport
Asheville/Regional Airport
Raleigh/Raleigh-Durham Airport
in IWAIR
State
AK
AK
AR
AZ
CA
CA
CA
CA
CO
CT
FL
FL
GA
GA
HI
IA
ID
IL
LA
LA
LA
ME
MI
MI
MN
MO
MS
MT
NC
NC
(continued)
D-9
-------
IWAIR Technical Background Document
Appendix D
Table D-l. (continued)
Station
Number
24011
14935
23050
23169
24128
14820
93815
13968
94224
24232
14751
13739
14778
11641
13880
13877
13897
23047
13958
12924
03927
12960
23023
24127
13737
14742
24233
24157
03860
24089
Station Name
Bismarck/Municipal Airport
Grand Island/Airport
Albuquerque/International Airport
Las Vegas/McCarran International Airport
Winnemucca/WSO Airport
Cleveland/Hopkins International Airport
Dayton/International Airport
Tulsa/International Airport
Astoria/Clatsop County Airport
Salem/McNary Field
Harrisburg/Capital City Airport
Philadelphia/International Airport
Williamsport-Lycoming/County
San Juan/Isla Verde International Airport
Charleston/International Airport
Bristol/Tri City Airport
Nashville/Metro Airport
Amarillo/International Airport
Austin/Municipal Airport
Corpus Christi/International Airport
Dallas/Fort Worth/Regional Airport
Houston/Intercontinental Airport
Midland/Regional Air Terminal
Salt Lake City/International Airport
Norfolk/International Airport
Burlington/International Airport
Seattle/Seattle-Tacoma International
Spokane/International Airport
Huntington/Tri-State Airport
Casper/Natrona Co International Airport
State
ND
NE
NM
NV
NV
OH
OH
OK
OR
OR
PA
PA
PA
PR
SC
TN
TN
TX
TX
TX
TX
TX
TX
UT
VA
VT
WA
WA
WV
WY
D-10
-------
£5
»^X»Jr^
Mr Lswy193! iW?
an?* JKVm, 4, Jt#/
i*—-* * xCTir1^ '-%>«i*%i
Ci
r
I
t
s
g.
Ci
S
Figure D-2. Meteorological stations and region boundaries for the contiguous 48 states.
1
s
b
-------
IWAIR Technical Background Document
Appendix D
0 T0140 280 420 »0
Kilometers
Zf Cod* Cwilitkls to S»*eci«c TR1 Fa
-------
0 65 130 260 mo SO
Kit-meters
£5
r
I
•
I
X
g.
1
s
Figure D-4. Meteorological stations and region boundaries for the southeastern United States with TRI facilities.
b
-------
0 55110 220 330 440
] KBonwters
W««
e
New
ZIP Code Ctnliews MrSMcUct Tfti RUM*
MM6 f
* -,>*
•\. »fw"
:'ۥ,"
Figure D-5. Meteorological stations and region boundaries for the northeastern United States with TRI facilities.
-------
IWAIR Technical Background Document Appendix D
assigning final boundaries for each selected station. Figures D-6, D-7, and D-8 also show the
contiguous 48 states and the selected stations overlaid on Bailey's ecoregions, physiographic
features, and land cover, respectively. Figures D-9 and D-10 show physiographic features for
Alaska and Hawaii, respectively.
D.3.1 West Coast
The West Coast is defined by a narrow coastal plain and mountain chains running parallel
to the coast of the Pacific Ocean. In many areas, the mountainous region is broken by a large
central valley, such as in California. Due to the potential number of facilities in California that
may use IWAIR, the California central valley was regionally delineated; the central valleys in
Washington and Oregon were combined with some rural mountainous areas to their east.
The northwestern Pacific coast contains a narrow plain between the Pacific Ocean and the
Coast Ranges. The Astoria/Clatsop County Airport station (94224) in Oregon represents the
region from the Strait of Juan de Fuca south to the Oregon/California border. The wind rose
shows generally weak directionality (bin W), and the average wind speed is 8 knots.
The California coast is divided just north of Point Conception above Los Angeles. The
northern section is represented by the San Francisco International Airport (23234). The wind
rose shows strong directionality (bin C), and the average wind speed is 12 knots.
The southern California coast contains the Los Angeles basin south to the California/
Mexico border. This region is represented by the Los Angeles International Airport (23174).
The wind rose shows strong directionality (bin C), and the average wind speed is 8 knots.
The California central valley region, which encompasses the Sacramento Valley to the
north and the San Joaquin Valley to the south, is defined by the Coast Range and Diablo Range
on the west and the Sierra Nevada mountains on the east. The valley extends south to the
northern rim of the Los Angeles basin. This valley was divided into two sections between
Sacramento and Redding because of the variation in wind regimes. The southern section is
represented by Fresno Air Terminal (93193). The wind rose shows strong directionality (bin C).
The northern division, whose northern border is represented by an ecoregion change to the
Willamette Valley and Puget Trough Section, is represented by the Redding AAF (24257). The
wind rose shows moderate directionality (bin B).
The inland portion of Washington is bounded by the Coast Ranges on the west, the edge
of the Humid Temperate Domain to the east, the Washington/Canada border to the north, and the
Columbia River to the south. This region is represented by the Seattle-Tacoma International
Airport (24233). The wind rose shows moderate directionality (bin B), and the average wind
speed is 10 knots.
D-15
-------
N
A
100 0 100200300*0 Kilometers
Figure D-6. Meteorological stations and region boundaries for the continental United States
with Bailey's ecoregions (Bailey et al., 1994).
(continued)
-------
IWAIR Technical Background Document
Appendix D
•a
a>
S
=
o
S
0/j
sS
e
-i
1
55
ink
«b
O
.ft
£
O
4
•%
O
K
«J
1^5
•5J
9
-------
•jif
f~~|
I I CO L U M 8 !A f LATEA U
[^j GREAT PLAINS
[~~1 INTERIOR LOW PLATEAUS
I I LOITER CALIFORNIUM
M Cn MIDDLE ROCKS MOUNTAINS
»OtS*SOtsa m MEW EKGLAHD
lolldaiY I I NORTHERN ROCKS' MOUNTAINS
K* I I OUACHFTA
AO IRQ NDAC K | j OZARK PLATEAUS
APPSIACMKN HATEAUS I 1 PACIFC IOROER
I 1 BASIN AND RANGE | j PIEDMONT
|—-| HUE RIDGE | 1 SOUTHERN ROCKS' MOUNTAINS
(23CASCADE-SIERRA MOUNTAINS I I ST. LAW RENC E VALLEY
[—] CENTRAL LOWI LAND [^SUPERIOR UPLAND
f—| COASTAL f LAIN [~~] VALLEY AN D RIOG E
[H3COLORAPO PLATEAUS j S WYOMING SASIM
fi|«
100 0 100 200 300 400 Kilometers
Figure D-l. Meteorological stations and region boundaries for the continental United States with
physiography (Fenneman and Johnson, 1946).
-------
o undary
* All Met Stations
I j States
US Land C over
] Urban
Cropland and Pasture
Grassland and Shrublarsd
Forest
Water Bodies
Wetland
B a rr e n
Tuodfa
^EEj Snova or Ice
BBJ N v: a*,]
200 0 200 400 600 Kilometers
£5
Ci
r
I
t
s
g.
Ci
S
Figure D-8. Meteorological stations and region boundaries for the continental United States with land
cover (USGS, 1999).
1
-------
27502
27401
Legend
» NOT SELECTED
"""""• BOUNDARY
S
Mode raiah^ High Rugged Mtrs
\ \ Genecalljf Flat
| | Plateaus and Highlands of Rolling Topography
bony Mountairs ^eneralh^' Rolling
| | E4remefy High Rugged Mtos
Figure D-9. Meteorological stations and region boundaries for Alaska with physiography (Wahrhaftig, 1965).
-------
£5
r
I
•
Kauai
(22536
Legend
•JC NEW
• NOT SELECTED
HIGHELEV
100-700
701 - 1300
i 1301 -2200
2201 - 3300
| 3301 - 4500
6501 - 10000
10001 - 14000
.^Oahu
Molokai
Maul
Kahoola«e
Lanai
0 25 50 100 150 200
• • • ^^^m ' r
HllO
I
I
X
g.
Figure D-10. Meteorological stations for Hawaii with physiography (State of Hawaii, 1997).
1
-------
IWAIR Technical Background Document Appendix D
D.3.2 Desert Southwest
The Desert Southwest is defined by various deserts and mountain ranges. One
distinguishing feature is the transition between low desert in southern Arizona and high desert in
northern Arizona. The southern boundary of this section is the United States/Mexico border.
Southern Arizona contains the Sonoran Desert. This region of low desert is represented
by the station at Phoenix/Sky Harbor International Airport (23183). The region is bounded to the
north between Phoenix and Prescott, Arizona, along the southern edge of the Columbia Plateau,
which represents the transition from low to high desert. The wind rose shows moderate
directionality (bin B), and the average wind speed is 6 knots.
Northern Arizona, southeastern California, southern Nevada, and southern Utah are
represented by the station at Las Vegas/McCarran International Airport (23169). This region is
characterized by high desert, including the Columbia Plateau. Relatively few facilities and people
are located here. The wind rose shows mild directionality (bin A), and the average wind speed is
10 knots.
The mountainous region of western New Mexico and far west Texas is represented by the
station at Albuquerque International Airport (23050). This region is bounded on the east by the
Sacramento Mountains east of El Paso, Texas, and by the Sangre de Cristo Mountains east of
Albuquerque, New Mexico. The wind rose shows weak directionality (bin W), and the average
wind speed is 8 knots.
D.3.3 Western Mountains
The Western Mountains include numerous mountain ranges, plateaus, and valleys that
affect wind flows. The northern portion of the Western Mountains is bounded on the west by the
eastern edge of the Humid Temperate Domain and on the east by the Great Plains in western
Montana. The southern boundary is approximately at the southern edge of the Temperate Steppe
Regime Mountains. This region is represented by the station at Spokane International Airport.
The wind rose shows mild directionality (bin A), and the average wind speed is 9 knots.
The inland region of Oregon includes both the central valley area and the Great Sandy
Desert, east to the Columbia Plateau. The western boundary is the Coast Ranges. The Black
Rock Desert forms the southern boundary. This region is represented by the station at McNary
Field in Salem, Oregon (24232). The wind rose shows moderate directionality (bin B), and the
average wind speed is 9 knots. Facilities in the eastern portion of this region should consider
obtaining local meteorological data and running the ISCST3 model to obtain local dispersion
factors for IWAIR; this area is not well-represented by any of the surrounding stations but did not
have enough population or TRI facilities to warrant adding another station to IWAIR.
The Snake River Plain of southern Idaho forms the region represented by Boise Air
Terminal (24131) in Idaho. This region is bounded by the Salmon River Mountains on the north
and the Columbia Plateau to the west and south. The wind rose shows moderate directionality
(bin B), and average wind speed is 9 knots.
D-22
-------
IWAIR Technical Background Document Appendix D
Northern Nevada and northeastern California are represented by the station at
Winnemucca WSO Airport (24128) in Nevada. This is the Great Basin area. The wind rose
shows mild directionality (bin A), and the average wind speed is 8 knots.
The Salt Lake Basin and the Great Divide Desert in Utah and Colorado are represented by
the station at Salt Lake City International Airport (24127) in Utah. The eastern boundary of this
region is formed by the Wind River Range and the Front Range. The wind rose shows moderate
directionality (bin B), and the average wind speed is 9 knots.
D.3.4 Texas (Excluding the Gulf Coast)
The state of Texas is a very large section encompassing many wind regimes. These are
bounded by mountains, deserts, forests, the Gulf of Mexico, and plains. The Gulf Coast region is
covered in Section D.3.5.
The Texas Panhandle region is represented by the station at Amarillo International
Airport (23047). The western boundary is formed by the Sangre de Cristo Mountains in New
Mexico. The northern boundary is the southern edge of the Great Plains. The southern boundary
divides this region from the West Texas region to its south. The wind rose shows mild
directionality (bin A), and the average wind speed is 13 knots.
The West Texas region includes high plateaus and is represented by the station at
Midland Regional Airport (23023). The western boundary of this region is formed by the
Sacramento Mountains. The wind rose for this region shows moderate directionality (bin B), and
the average wind speed is 10 knots.
Central Texas is represented by the station at Dallas/Ft. Worth airport (03927). The
majority of the population in this region is located in the vicinity of Dallas and Ft. Worth. Also,
most of the industrial facilities in this region are located in that vicinity. The southwestern
portion of this region encompasses the Edwards Plateau. The eastern boundary is formed by the
transition to forest in eastern Texas. The wind rose shows strong directionality (bin C), and the
average wind speed is 11 knots.
South Central Texas includes the area north of the southern coastal region and south
Texas. The eastern boundary is formed by the eastern edge of the Prairie Parkland (Subtropical)
Province. The southern boundary is formed by the transition from grassland and crop land to the
shrub land in Southern Texas. This region is represented by the station at Austin Municipal
Airport (13958). The wind rose shows moderate directionality (bin B), and the average wind
speed is 8 knots.
Southern Texas includes the southern coast of the Gulf of Mexico, including Corpus
Christi and Brownsville, Texas. This region is represented by the station at Corpus Christi
International Airport (12924). The southern and western borders are formed by the Rio Grande
River. The eastern border is the Gulf of Mexico. The northern boundary is formed by the
transition from shrub land in Southern Texas to grassland and crop land in South Central Texas.
The wind rose shows strong directionality (bin C), and the average wind speed is 12 knots.
D-23
-------
IWAIR Technical Background Document Appendix D
D.3.5 Gulf Coast
The wind regime along the Gulf of Mexico is strongly influenced by that body of water.
However, its effects do not reach very far inland. A series of regions have been designated to
represent the coastal section.
The middle Texas Gulf Coast is represented by the station at Houston Intercontinental
Airport (12960). Although Houston itself is somewhat inland, it is expected to have a more
coastal environment due to Galveston Bay. This region extends south past Victoria to the
vegetative boundary marking Southern Texas. The wind rose in this region shows mild
directionality (bin A), and the average wind speed is 8 knots.
The western portion of the Louisiana Gulf Coast and the far eastern portion of the Texas
Gulf Coast has the vegetative land cover change to forest as its northern border. This relatively
small area includes a high concentration of industrial facilities along the coast. The station at
Lake Charles Municipal Airport (03937) represents this region. The wind rose shows mild
directionality (bin A), and the average wind speed is 9 knots.
The Central Gulf Coast extends from eastern Louisiana through the Florida panhandle.
This entire region is part of the Outer Coastal Plain Mixed Forest Province and is characterized
by weakly directional winds. The station at New Orleans International Airport (12916) in
Louisiana represents this region. The wind rose shows weak directionality (bin W), and the
average wind speed is 8 knots.
The West Coast of the Florida Peninsula is heavily influenced by the Gulf of Mexico,
which has warmer water than the Atlantic Ocean off the East Coast of the Florida Peninsula. This
region extends from the Florida Panhandle to the north to Cape Romano, just north of the
Everglades in South Florida. The station at Tampa International Airport (12842) represents this
region. The wind rose shows mild directionality (bin A), and the average wind speed is 7 knots.
D.3.6 Southeast
The Southeast section extends from the Atlantic coastal region of Florida and the Florida
Keys northward through Georgia and South Carolina. This region has an extremely broad coastal
plain, requiring it to be divided between coastal region and more inland regions for Georgia and
South Carolina. This section also includes the inland areas of Louisiana, Mississippi, and
Alabama.
The southern tip of Florida includes the Everglades, which have been drained along the
Atlantic coast to provide land for Miami, Ft. Lauderdale, West Palm Beach, and other coastal
cities. This region, which includes the Florida Keys, is represented by the station at Miami
International Airport (12839). Its wind rose shows mild directionality (bin A), and the average
wind speed is 9 knots.
A long stretch of the Southeastern Atlantic Coast extends from north of Vero Beach,
Florida (i.e., just south of Cape Canaveral), through Georgia and South Carolina. The Atlantic
D-24
-------
IWAIR Technical Background Document Appendix D
Ocean forms the eastern boundary, and the land cover boundary between the more forested coast
and more agricultural inland area forms the western boundary. The station at Charleston
International Airport (13880) represents this region. The wind rose shows weak directionality
(bin W), and the average wind speed is 8 knots.
The inland coastal plain of Georgia and South Carolina extends inland from the coastal
forest/agriculture land cover boundary to the physiographic boundary between the Coastal Plain
and the Blue Ridge. This region is represented by the station at Macon's Lewis B. Wilson
Airport (03813) in Georgia. The wind rose shows weak directionality (bin W), and the average
wind speed is 8 knots.
Further inland in Georgia and South Carolina lies the Blue Ridge region. This region is
delineated by physiographic boundaries—the transition to the Coastal Plain on the coastal side
and to the Appalachian Plateaus on the inland side. The station at Atlanta Hartsfield
International Airport (13874) represents this region. The wind rose shows mild directionality
(bin A), and the average wind speed is 9 knots.
The inland areas of Alabama and Mississippi are represented by the station at Meridian
Key Field (13865), which is located in Mississippi close to the Alabama border. This region
extends from the Central Gulf Coast region northward into southern Tennessee (including
Memphis) and westward into the Coastal Plain region of eastern Arkansas. The wind rose shows
mild directional (bin A), and the average wind speed is 7 knots.
The inland portion of Louisiana and eastern Texas is part of the Coastal Plain. This region
extends northward to the Ouachita Mountains, which are just south of the Ozark Plateau in
Arkansas. The western boundary is the vegetative transition from the forests in this region to the
prairies in Texas. This region is represented by the station at Shreveport Regional Airport
(13957) in Louisiana. The wind rose is mildly directional (bin A), and the average wind speed is
9 knots.
D.3.7 Middle Atlantic
The Middle Atlantic section includes coastal areas with bays, sounds, inlets, and barrier
islands; a broad coastal plain; and the southern Appalachian Mountains. The physiographic
features generally extend from northeast to southwest, parallel to the coast of the Atlantic Ocean.
The coastal region of North Carolina and Virginia is represented by the station at Norfolk
International Airport (13737) in Virginia. This region is bounded by the Atlantic Ocean on the
east, the physiographic boundary to the Piedmont section to the west, the political border
between North Carolina and South Carolina to the south, and a line bisecting the Chesapeake
Bay to the north. The wind rose shows mild directionality (bin A), and the average wind speed is
10 knots.
The Piedmont region of North Carolina and Virginia is just inland from the coastal
region. This region is delineated on the east by the physiographic boundary with the coastal plain,
and on the west with the physiographic boundary with the Appalachian Mountains. This region is
D-25
-------
IWAIR Technical Background Document Appendix D
also part of the Southeastern Mixed Forest Province of Bailey's ecoregions. The station at
Raleigh-Durham Airport (13722) in North Carolina represents this region. The wind rose
shows weak directionality (bin W), and the average wind speed is 8 knots.
The eastern portion of the southern Appalachian Mountains lies to the west of the
Piedmont region of North Carolina and Virginia. This region extends to the southwest to include
a portion of western South Carolina and northeastern Georgia. The station at Asheville Regional
Airport (03812) in North Carolina represents this region. The wind rose shows moderate
directionality (bin B), and the average wind speed is 10 knots.
The western portion of the southern Appalachian Mountains, including the Cumberland
Plateau, lies in western Virginia, eastern Tennessee, northwestern Georgia, and northeastern
Alabama. The western edge of this region follows the physiographic boundary between the
Appalachian Plateaus and the Interior Low Plateaus. The station at Bristol Tri City Airport
(13877) in Tennessee represents this region. The wind shows weak directionality (bin W), and
the average wind speed is 8 knots.
The Appalachian Mountains of West Virginia and eastern Kentucky are characterized by
mountainous ridges and valleys extending from northeast to southwest. This region is represented
by the station at Huntington Tri-State Airport (03860) in West Virginia. The wind rose shows
mild directionality (bin A), and the average wind speed is 7 knots.
The inland region encompassing northern Virginia, part of Maryland, and eastern
Pennsylvania is composed of another section of the Appalachian Mountains. Boundaries are
approximated by the Bailey's Central Appalachian Forest province. The station at
Harrisburg/Capital City Airport (14751) in Pennsylvania represents this region. The wind rose
shows mild directionality (bin A), and the average wind speed is 9 knots.
The northern portion of the Chesapeake Bay northward through New Jersey, eastern
Pennsylvania, and New York City is characterized by the Eastern Broadleaf Forest (Oceanic)
Province in the coastal plain. The station at Philadelphia International Airport (13739) in
Pennsylvania represents this region. The wind rose shows mild directionality (bin A), and the
average wind speed is 9 knots.
D.3.8 Northeast
The Northeast section includes New England. This region is characterized by forests to
the north, large urban areas along the southern coastal plain, and the mountain ridges and valleys
of the northern Appalachian Mountains. This section is bounded by the Atlantic Ocean on the
east, the U.S./Canada border on the north, and the coastal plain of the eastern Great Lakes to the
west.
The station at Bradley International Airport (14740) in Hartford, Connecticut, represents
the New England region, which encompasses Connecticut, Massachusetts, Rhode Island and a
small portion of Vermont, New Hampshire, and eastern New York. The wind rose shows mild
directionality (bin A), and the average wind speed is 8 knots.
D-26
-------
IWAIR Technical Background Document Appendix D
Northern New England is represented by the station located at the International Jetport
(14764) in Portland, Maine. This region includes Maine and most of New Hampshire and
Vermont. The northwest portion of Vermont is not included in this region. The wind rose shows
mild directionality (bin A), and the average wind speed is 9 knots.
The station at the International Airport (14742) in Burlington, Vermont, represents a
very small region. Burlington is located in a valley between mountainous areas of the northern
Appalachian Mountains. The wind rose shows moderate directionality (bin B), and the average
wind speed is 10 knots.
The remainder of the northern Appalachian Mountains in New York and Pennsylvania is
represented by the station at Williamsport-Lycoming (14778) in Pennsylvania. This region is
bounded on the west by the Adirondack Mountains, just to the east of the coastal plain of Lake
Ontario. The wind rose shows mild directionality (bin A), and the average wind speed is 9 knots.
D.3.9 Great Lakes
The Great Lakes are bodies of water large enough to affect weather patterns in that
portion of the country. Land and sea breezes affect wind patterns along the coasts, especially
along Lake Michigan in the summer. The moisture of the lakes also affects winter precipitation
patterns (i.e., lake effect snow storms).
The Eastern Great Lakes divide the United States and Canada. On the U.S. side, the
western portion of New York, a small portion of Pennsylvania, and northeastern Ohio border the
eastern shores of Lake Ontario and Lake Erie. Mountains form the eastern boundary. The
southwestern border is drawn southward from the southern shore of Lake Erie. The station at
Hopkins International Airport (14820) in Cleveland, Ohio, represents this region. The wind rose
shows moderate directionality (bin B), and the average wind speed is 10 knots.
The Lower Peninsula of Michigan is bordered by the Great Lakes on three sides.
Although this region has relatively few topographic features, the presence of the lakes may result
in different dispersion analyses for the eastern and western portions of the state. Therefore, the
Lower Peninsula has been divided into two regions—East and West.
The eastern region of the Lower Peninsula of Michigan is bordered by Lake Erie, Lake St.
Clair, and Lake Huron and includes Saginaw Bay and a small abutment with Canada. This region
is represented by the station at Detroit Metropolitan Airport (94847). The wind rose shows mild
directionality (bin A), and the average wind speed is 10 knots.
The western region of the Lower Peninsula of Michigan is bordered by Lake Michigan on
the west and the Straits of Mackinac on the north. The eastern portion of the Upper Peninsula of
Michigan is also included in this region. The station at Muskegon County Airport (14840)
represents this region. The wind rose shows weak directionality (bin W), and the average wind
speed is 11 knots.
D-27
-------
IWAIR Technical Background Document Appendix D
The western shore of Lake Michigan, which includes Green Bay, is formed by the
northeastern portion of Illinois, eastern Wisconsin, and part of the Upper Peninsula of Michigan.
Lake Superior forms the northern boundary of this region, and the western boundary is formed by
the hills to the east of the Wisconsin River and the Upper Mississippi River. This region is
represented by the station at O'Hare International Airport (94846) in Chicago, Illinois. The wind
rose shows mild directionality (bin A), and the average wind speed is 9 knots.
D.3.10 Central States
This section includes the Central Lowlands (south of the Great Lakes), the Midwest, and
the Great Plains. The elevation for this section is generally lowest in the Mississippi Valley,
which extends through the Midwest and drains a large portion of the center of the continental
United States. This section also includes other major river valleys, including the Ohio,
Tennessee, and Missouri. This section is bordered on the east by the Appalachian Mountains, on
the west by the Rocky Mountains, on the north by the border with Canada, and on the south by
the Southeast, Texas, and the Desert Southwest.
The Central Lowland is the area south of the Great Lakes and west of the Appalachian
Mountains. This area is divided into several regions based on wind rose data. The region that
includes central Indiana, Ohio, and western Pennsylvania is represented by the new station at
Dayton International Airport (93815) in Ohio. The western boundary is formed by a transition
from hills in this region to flat land to its west. The northern boundary is formed by the Great
Lakes section, and the eastern and southeastern boundaries are formed by the Appalachian
Mountains. The wind rose shows mild directionality (bin A), and the average wind speed is 10
knots.
The region encompassing parts of Illinois, northeastern Missouri, and most of Iowa is
relatively flat farmland. The station at Waterloo Municipal Airport (94910) in Iowa represents
this region. The wind rose shows mild directionality (bin A), and the average wind speed is 11
knots.
The region of southern Indiana, south-central Illinois, and east-central Missouri includes
the industrial area surrounding St. Louis, Missouri. The station at Lambert International Airport
(13994) in St. Louis, Missouri, represents this region. The wind rose shows mild directionality
(bin A), and the average wind speed is 10 knots.
The region to the south of the one represented by St. Louis includes western Kentucky,
central and western Tennessee north of Memphis, and southeastern Missouri east of the Ozark
Plateau. This region is represented by the station at Nashville Metropolitan Airport (13897) in
Tennessee. The wind rose shows moderately directionality (bin B), and the average wind speed is
8 knots.
Adams Field (13963) in Little Rock, Arkansas, represents a small region that includes
the higher portions of the Ozark Plateau in southern Missouri and northern Arkansas and the
Ouachita Mountains in central Arkansas. The wind rose shows weak directionality (bin W), and
the average wind speed is 7 knots.
D-28
-------
IWAIR Technical Background Document Appendix D
The northern portion of the Midwest includes the portion of Wisconsin west of the Lake
Michigan coastal plain, Minnesota, and the eastern portion of North and South Dakota. The
western boundary through the Dakotas is the physiographic boundary between the Central
Lowland and the Great Plains. This region is represented by the station at Minneapolis-St. Paul
International Airport (14922) in Minnesota. The wind rose shows mild directionality (bin A), and
the average wind speed is 11 knots.
The Great Plains lie between the Central Lowlands to the east and the Rocky Mountains
to the west. The headwaters of the Mississippi and the Missouri rivers are located in the Great
Plains. Lands at higher elevations are more grassland and shrub land used for cattle ranges,
while the lower elevations are used more frequently for crops. The region that includes the
western portion of North and South Dakota and eastern Montana is represented by the station at
Bismarck Municipal Airport (24011) in North Dakota. The wind rose shows weak directionality
(bin W), and the average wind speed is 12 knots.
The central portion of Montana is more rugged, but still part of the Great Plains. The
Rocky Mountains form the western and southwestern boundaries of this region, which is
represented by the station at Billings Logan International Airport (24033) in Montana. The wind
rose shows strong directionality (bin C), and the average wind speed is 10 knots.
The original station at Casper/Natrona County International Airport (24089) in Wyoming
represents Wyoming east of the Front Range of the Rocky Mountains, southwestern South
Dakota, and western Nebraska. The wind rose shows strong directionality (bin C), and the
average wind speed is 14 knots. In this region, most cities are located in valleys or near the base
of a mountain ridge. The wind regime at Casper, therefore, may not adequately represent
facilities at other locations in this region.
The region represented by the station at Stapleton International Airport (23062) in
Denver, Colorado, has facilities clustered in the Denver vicinity. The southern boundary is
formed by the southern edge of the Great Plains. The wind rose shows mild directionality (bin
A), and the average wind speed is 8 knots. Grand Junction, Colorado, which is located in the
western portion of the state, is included in this region although it exhibits a different wind
regime. Facilities located in the western portion of Colorado should consider entering dispersion
factors based on their local meteorological data; this area is not well-represented by any of the
surrounding stations, and did not have enough population or TRI facilities to warrant adding
another station to IWAIR.
The north-central portion of the Great Plains includes most of Nebraska, northern Kansas,
western Iowa, southwestern South Dakota, and northwestern Missouri. This region is represented
by the station at Grand Island Airport (14935) in Nebraska. The wind rose shows moderate
directionality (bin B), and the average wind speed is 12 knots.
The southern portion of the Great Plains includes eastern Oklahoma, most of Kansas, and
the lower area of the western Ozark Plateau in southwestern Missouri and northwestern
Arkansas. This region is represented by the station at Tulsa International Airport (13968). The
wind rose shows moderate directionality (bin B), and the average wind speed is 11 knots.
D-29
-------
IWAIR Technical Background Document Appendix D
D.3.11 Alaska
Alaska contains a wide variety of topography and land cover (see Figure D-9). The
northern portion of the state, which includes the North Shore oil fields, is primarily tundra on flat
topography. The southwestern portion is grassland and shrub land on flat to rolling topography.
The remainder of the state includes large, forested valleys and rugged mountains with glaciers.
The coastal areas include numerous islands. IWAIR includes two stations in Alaska, but cannot
represent the entire state. The 1998 TRI data were used to select the locations of the included
stations.
The station at Juneau International Airport (25309) represents the southeastern portion of
Alaska. This region extends from just west of Yakutat Bay southward to Dixon Entrance. Canada
forms the northeastern border, and the Gulf of Alaska is on the west. The wind rose shows strong
directionality (bin C).
The station at Anchorage WSMO Airport is in a unique wind regime in a coastal valley
surrounded by mountains. However, several TRI facilities report land-based air emissions for this
region. Anchorage is located at the northern end of Cook Inlet. Industrial facilities are located
just to its south on the western portion of the Kenai Peninsula. This region, therefore, is bounded
by the Alaska Range to the west and north, the Chugach Mountains to the east, and the Gulf of
Alaska to the south. The wind rose shows mild directionality (bin A), and the average wind speed
is 8 knots.
All Alaska zip codes and coordinates that are not located within the regions assigned to
the stations at Juneau and Anchorage are assigned to a "no data" region. Users entering
coordinates in the "no data" region will be required to enter user-defined dispersion factors,
based on local meteorological data.
D.3.12 Hawaii
The station at Honolulu International Airport (22521) on Oahu represents Hawaii. The
wind rose shows strong directionality (bin C).
D.3.13 Puerto Rico
The station at San Juan represents Puerto Rico; this is the only station in Puerto Rico.
The wind rose shows strong directionality (bin C), and the averge wind speed is 11 knots.
D.4 References
Bailey, Robert G., Peter E. Avers, Thomas King, W. Henry McNab (eds). 1994. Ecoregions and
Subregions of the United States (map). Washington, DC: U.S. Geological Survey. Scale
1:7,500,000; colored. Accompanied by a supplementary table of map unit descriptions
compiled and edited by McNab, W. Henry, and Bailey, Robert G. Prepared for the U.S.
Department of Agriculture, Forest Service, http://www.epa.gov/docs/grdwebpg/bailey.
D-30
-------
IWAIR Technical Background Document Appendix D
EQM ( Environmental Quality Management, Inc.) and E.H. Pechan & Associates. 1993.
Evaluation of Dispersion Equations in Risk Assessment Guidance for Super fund (RAGS):
Volume I - Human Health Evaluation Manual. Prepared for U.S. Environmental
Protection Agency, Office of Emergency and Remedial Response, Toxics Integration
Branch. Washington, DC.
Fenneman, N.M., and Johnson, D.W. 1946. Physical Divisions of the United States (map).
Washington, DC: U.S. Geological Survey.
NOAA (National Oceanic and Atmospheric Administration). 1992. International Station
Meteorological Climate Summary, Version 2.0. CD-ROM. National Climatic Data
Center. Asheville, NC.
Schroeder, K., R. Clickner, and E. Miller. 1987. Screening Survey of Industrial Subtitle D
Establishments. Draft Final Report. Westat, Inc., Rockville, MD, for U.S. EPA Office of
Solid Waste. Contract 68-01-7359.
State of Hawaii. 1997. Elevation Contours (100 Foot Intervals) (map). Edition 1. Office of
Planning, Honolulu, Hawaii. June, http://www.hawaii.gov/dbedt/gis/physical.htm
(Elevation contours - 100 ft intervals).
U.S. EPA (Environmental Protection Agency). 2000. Toxics Release Inventory (TRI) 1998
Public Data Release. Office of Pollution Prevention and Toxics, Washington, DC.
U.S. EPA (Environmental Protection Agency). 2001. Industrial Surface Impoundments in the
United States. Office of Solid Waste and Emergency Response, Washington, DC. EPA
530-R-01-005.
U.S. Geological Survey. 1999. North American Land Cover Characteristics (map). EROS Data
Center, Sioux Falls, SD. http://nationalatlas.gov/atlasftp.html
Wahrhaftig, Clyde. 1965. Physiographic Divisions of Alaska. U.S. Geological Survey
Professional Paper 482, Plate 1 (map). Washington, DC: U.S. Geological Survey.
D-31
-------
-------
Appendix D-l
Data for Meteorological Stations Considered
for Inclusion in IWAIR
-------
-------
Table Dl-1. Data for All Meteorological Stations Considered; Grouped by Region and Final Assignment
Station
No.
Station Name
State
Status
Wind
Speed
(knots)
Wind-Rose
Bin"
Wind
Directionality0
Stability Class"
Notes
West Coast
23174
23188
23234
24283
24233
24227
24257
24225
93193
23232
94224
94240
24284
LOS ANGELES/INT'L ARPT
SAN DIEGO/LINDBERGH FIELD
SAN FRANCISCO/INT'L ARPT
ARCATA/ARPT
SEATTLE/SEATTLE-TACOMA INT'L
OLYMPIA/ARPT
REDDING/AAF
MEDFORD/JACKSON COUNTY ARPT
FRESNO/AIR TERMINAL
SACRAMENTO/EXECUTIVE ARPT
ASTORIA/CLATSOP COUNTY ARPT
QUILLAYUTE/WSO AIRPORT
NORTH BEND/FAA AIRPORT
CA
CA
CA
CA
WA
WA
CA
OR
CA
CA
OR
WA
OR
original
original
original
new
original
new
8
8
12
NA
10
8
NA
6
7
9
8
7
NA
C
B
C
A
B
B
B
A
C
A
W
w
B
30/52
17/41
24/52
11/24
18/45
17/41
17/39
11/28
24/45
12/34
9/26
8/22
15/30
20/43/37
NA
17/54/29
NA
15/60/25
NA
NA
24/38/38
29/29/42
24/35/40
NA
NA
NA
3 yrs data
4 yrs data
4 yrs data
3 yrs data
Desert Southwest
23050
23081
23044
23169
23184
23161
03160
23154
93129
23183
23160
Western
24127
24027
ALBUQUERQUE/INT'L ARPT
GALLUP/FAA AIRPORT
EL PASO/INTL ARPT
LAS VEGAS/MCCARRAN INT'L ARPT
PRESCOTTMUNICIPAL
DAGGETT/FAA AIRPORT
DESERT ROCK
ELY/YELLAND FIELD
CEDAR CITY/FAA AIRPORT
PHOENIX/SKY HARBOR INT'L ARPT
TUCSON/TNTL ARPT
Mountains
SALT LAKE CITY/INT'L ARPT
ROCK SPRINGS/FAA AIRPORT
NM
NM
TX
NV
AZ
CA
NV
NV
UT
AZ
AZ
UT
WY
original
original
original
original
8
NA
8
10
NA
NA
NA
10
NA
6
7
9
NA
W
A
W
A
C
C
A
C
A
B
B
B
B
9/23
11/26
8/18
13/33
25/52
24/60
13/29
22/49
13/31
16/35
18/41
18/46
20/42
26/36/37
NA
28/30/42
27/38/35
NA
NA
NA
NA
NA
33/18/49
28/31/41
22/44/34
NA
local mountain effects
3 yrs data
4 yrs data
4 yrs data
(continued)
-------
Table Dl-1. (continued)
Station
No.
24128
24121
23185
24131
24156
24157
24243
24146
24153
24155
24232
24221
24229
24230
Texas
03927
23034
03969
13959
12924
12919
13958
12962
12921
23023
13962
Station Name
WINNEMUCCA/WSO AIRPORT
ELKOMUNICIPAL ARPT
RENO/CANNON INTL ARPT
BOISE/AIR TERMINAL
POCATELLOMUNICIPAL ARPT
SPOKANE/INT'L ARPT
YAKIMA/AIR TERMINAL
KALISPELL/GLACIER PK INTL AP
MSSOULA/JOHNSON-BELL FLD
PENDLETONMUNICIPAL ARPT
SALEM/MCNARY FIELD
EUGENE/MAHLON SWEET ARPT
PORTLAND/INTL ARPT
REDMOND/FAA AIRPORT
(excluding Gulf Coast)
DALLAS/FORT WORTH/REGIONAL AR
SAN ANGELO/WSO AIRPORT
STEPHENVILLE
WACO/MADISON-COOPER ARPT
CORPUS CHRISTI/INT'L ARPT
BROWNSVILLE/INTL ARPT
AUSTIN/MUNICIPAL ARPT
HONDO/WSMO AIRPORT
SANANTONIO/WSFO
MIDLAND/REGIONAL AIR TERMINAL
ABILENE/MUNICIPAL ARPT
State Status
NV original
NV
NV
ID original
ID
WA new
WA
MT
MT
OR
OR original
OR
OR
OR
TX new
TX
TX
TX
TX new
TX
TX new
TX
TX
TX new
TX
Wind
Speed
(knots)
8
8
10
9
10
9
7
8
7
NA
9
9
7
NA
11
10
NA
12
12
12
8
NA
9
10
11
Wind-Rose Wind
Bin"
A
W
W
B
B
A
B
A
W
A
B
A
A
A
C
c
C
c
c
c
B
B
B
B
B
Directionality0
10/23
9/24
9/22
16/37
16/44
13/35
18/40
11/25
9/24
11/28
16/31
14/30
11/29
13/29
22/43
21/42
22/44
22/43
21/48
21/48
17/40
15/36
16/41
16/37
17/45
Stability Class"
23/39/38
NA
NA
21/45/34
18/51/31
17/55/28
26/39/35
NA
NA
22/47/31
16/53/31
NA
15/58/26
NA
17/53/30
NA
NA
NA
NA
NA
19/48/32
NA
NA
NA
NA
Notes
2 yrs data only
4 yrs data
4 yrs data
4 yrs data
4 yrs data
3 yrs data
3 yrs data
(continued)
-------
Table Dl-1. (continued)
Station
No. Station Name
23047 AMARILLO/INT'L ARPT
23009 ROSWELL/TNDUSTRIAL AIR PARK
23042 LUBBOCK/REGIONAL ARPT
13966 WICHITA FALLS/MUNICIPAL ARPT
State Status
TX new
NM
TX
TX
Wind
Speed
(knots)
13
9
11
12
Wind-Rose Wind
Bin"
A
A
A
A
Directionality0
14/39
12/32
12/31
14/39
Stability Class"
14/64/23
NA
14/60/26
NA
Notes
4 yrs data
Gulf Coast
03937 LAKE CHARLES/MUNICIPAL ARPT
12917 PORT ARTHUR/JEFFERSON COUNTY
12842 TAMPA/INT'L ARPT
12835 FORT MYERS/PAGE FIELD
93805 TALLAHASSEE/MUNICIPAL ARPT
12916 NEW ORLEANS/INT'L ARPT
1 3894 MOBILE/WSO AIRPORT
12832 APALACfflCOLA/MUNICIPAL ARPT
13899 PENSACOLA/REGIONAL ARPT
1 3 970 BATON ROUGE/RYAN ARPT
12960 HOUSTON/INTERCONTINENTAL ARPT
12912 VICTORIA/WSO AIRPORT
LA new
TX
FL SIS
FL
FL
LA SIS
AL
FL
FL
LA
TX original
TX
9
9
7
7
7
8
9
NA
9
8
8
10
A
A
A
A
A
W
w
W
A
W
A
A
10/25
12/29
10/28
10/29
13/29
8/22
9/26
9/21
11/26
8/21
12/29
13/37
19/46/36
18/48/34
23/36/41
NA
24/32/44
22/41/38
NA
NA
NA
21/40/38
18/46/36
NA
3 yrs data
Southeast
03813 MACON/LEWIS B WILSON ARPT
03820 AUGUSTA/BUSH FIELD
93842 COLUMBUS/METROPOLITAN ARPT
13883 COLUMBIA/METRO ARPT
12839 MIAMI/INT'LARPT
12836 KEY WEST/INTL ARPT
12843 VERO BEACH/MUNICIPAL AIRPORT
12844 WEST PALM BEACH/INTL ARPT
GA new
GA
GA
SC
FL original
FL
FL
FL
8
7
8
6a
9
11
NA
10
W
W
A
A
A
B
A
A
9/26
6/17
11/25
11/27
13/34
16/39
10/27
12/34
22/39/40
NA
NA
21/40/39
18/43/39
NA
NA
NA
3 yrs data
not representative of rest
of region
3 yrs data
(continued)
-------
Table Dl-1. (continued)
Station
No.
13865
03881
13895
13876
03856
03940
93862
13893
13874
13873
03870
13880
12834
12816
13889
12815
03822
13861
13957
Station Name
MERIDIAN/KEY FIELD
CENTRE VILLE/WSMO
MONTGOMERY/WSO ARPT
BIRMINGHAM/MUNICIPAL ARPT
HUNTSVILLE/MADISON COUNTY JET
JACKSON/THOMPSON FIELD
TUPELO
MEMPHIS/INTL ARPT
ATLANTA/ATLNC-HARTSFIELD INT'
ATHENS/MUNICIPAL ARPT
GREER/GREENVL-SPARTANBRG AP
CHARLESTON/INT'L ARPT
DAYTONA BEACH/REGIONAL ARPT
GAINESVILLE/MUNICIPAL AIRPORT
JACKSONVILLE/INTL ARPT
ORLANDO/rNTL ARPT
SAVANNAH/MUNICIPAL ARPT
WAYCROSS/WSMO
SHREVEPORT/REGIONAL ARPT
State Status
MS SIS
AL
AL
AL
AL
MS
MS
TN
GA original
GA
SC
SC original
FL
FL
FL
FL
GA
GA
LA SIS
Wind
Speed
(knots)
7
NA
7
7
8
8
NA
7
9
8
8a
8
9
NA
8
7
8
NA
9
Wind-Rose Wind
Bin"
A
W
W
A
A
A
A
A
A
A
A
W
W
W
W
W
W
W
A
Directionality0
12/28
9/24
7/19
11/24
11/27
10/30
12/28
11/27
14/32
11/25
13/32
9/24
8/19
7/18
6/16
9/25
7/19
8/21
12/29
Stability Class"
22/38/40
NA
NA
NA
20/45/36
21/41/38
NA
20/44/36
20/46/34
22/41/37
21/43/36
18/43/38
NA
NA
NA
NA
20/40/40
NA
20/43/37
Notes
4 yrs data
4 yrs data
4 yrs data
4 yrs data
Middle Atlantic
03812
13741
03860
93814
03889
93820
03872
13866
13722
13881
13723
ASHEVILLE/REGIONAL ARPT
ROANOKE/WOODRUM ARPT
HUNTINGTON/TRI-STATE ARPT
COVINGTON/GREATER CINCINNATI
JACKSON/JULIAN CARROLL ARPT
LEXINGTON/BLUEGRASS FIELD
BECKLEY/RALEIGH CO MEMORIAL A
CHARLESTON/KANAWHA ARPT
RALEIGH/RALEIGH-DURHAM ARPT
CHARLOTTE/DOUGLAS INTL ARPT
GREENSBORO JTiGH POINT / WTNSTO
NC SIS
VA
WV original
KY
KY
KY
WV
WV
NC original
NC
NC
10
10
7
9
NA
9
10
8
8
8
7
B
A
A
A
A
A
A
A
W
W
A
19/41
11/28
13/31
13/31
13/35
13/32
11/25
10/26
9/26
9/25
13/31
18/49/32
18/48/34
20/47/34
NA
NA
18/51/32
NA
NA
20/44/37
21/42/37
20/43/37
4 yrs data
(continued)
-------
Table Dl-1. (continued)
Station
No.
13737
93729
13748
13740
13739
13781
93721
93730
14734
04781
94789
14732
13743
13877
13882
13891
14751
14737
93738
Station Name
NORFOLK/INT'L ARPT
CAPE HATTERAS/WSO
WILMINGTON/NEW HANOVER COUNTY
RICHMOND/R E BYRD INTL ARPT
PfflLADELPfflA/INT'L ARPT
WILMINGTON/GREATER WILMINGTON
BALTIMORE/BLT-WASHNGTN INTL
ATLANTIC CITY/AIRPORT NAFEC
NEWARK/INTL ARPT
ISLIP
NEW YORK/J F KENNEDY INTL AR
NEW YORK/LAGUARDIA ARPT
WASHINGTON DC/NATIONAL ARPT
BRISTOL/TRI CITY AIRPORT
CHATTANOOGA/LOVELL FIELD
KNOXVILLE/MC GHEE TYSON ARPT
HARRISBURG/CAPITAL CITY ARPT
ALLENTOWN/BETLEHEM-EASTON ARP
WASHINGTON DC/DULLES INTL AR
State Status
VA SIS
NC
NC
VA
PA original
DE
MD
NJ
NJ
NY
NY
NY
VA
TN new
TN
TN
PA original
PA
VA
Wind
Speed
(knots)
10
lla
9a
7
9
9
9
10
NA
NA
12
12
9
8
7
7
9
10
9
Wind-Rose Wind
Bin"
A
A
A
A
A
A
A
A
A
A
A
A
B
W
w
A
A
A
A
Directionality0
11/28
12/31
11/26
11/28
11/31
12/29
13/33
10/25
11/26
10/25
10/25
11/27
17/33
9/21
9/23
12/27
11/29
10/27
11/27
Stability Class"
14/60/26
NA
NA
NA
16/54/30
15/53/31
16/51/33
14/53/32
13/61/26
NA
NA
NA
NA
22/40/38
NA
21/44/35
17/51/33
14/57/29
NA
Notes
4 yrs data
4 yrs data
4 yrs data
Northeast
14740
14739
14765
14742
14764
14606
14745
HARTFORD/BRADLEY INT'L ARPT
BOSTON/LOGAN INTL ARPT
PROVIDENCE/T F GREEN STATE AR
BURLINGTON/INT'L ARPT
PORTLAND/INT'L JETPORT
BANGOR/FAA AIRPORT
CONCORD/MUNICIPAL ARPT
CT original
MA
RI
VT SIS
ME original
ME
NH
8
NA
10
10
9
NA
9
A
A
A
B
A
A
A
14/27
12/29
10/26
20/37
11/25
11/24
13/28
15/54/31
10/72/17
NA
13/61/26
14/55/31
NA
NA
position in valley
funnels winds
(continued)
-------
Table Dl-1. (continued)
Station
No.
14778
14735
04725
94725
14771
04751
14777
Station Name
WILLIAMSPORT-LYCOMING /COUNTY
ALBANY/COUNTY ARPT
BINGHAMTON/EDWIN A LINK FIELD
MASSENA/FAA AIRPORT
SYRACUSE/HANCOCK INTL ARPT
BRADFORD/FAA AIRPORT
WILKES-BARRE/WB-SCRANTON WSO
State Status
PA SIS
NY
NY
NY
NY
PA
PA
Wind
Speed
(knots)
9
10
10
NA
10
NA
8
Wind-Rose Wind
Bin"
A
A
A
A
A
A
A
Directionality0
12/32
13/30
10/28
11/28
11/31
11/31
12/29
Stability Class"
16/56/28
14/60/27
12/64/23
NA
NA
NA
15/56/29
Notes
3 yrs only
Great Lakes
14820
14733
14768
14860
14840
14848
94860
14847
14850
94846
14898
14839
94847
94849
14822
14826
14836
94830
Central
13897
03816
CLEVELAND/HOPKINS INT'L ARPT
BUFFALO/GREATER BUFFALO INTL
ROCHESTER/ROCHESTER-MONROE CO
ERIE/INTL ARPT
MUSKEGON/COUNTY ARPT
SOUTH BEND/MCHIANA REGIONAL
GRAND RAPIDS/KENT CO INTL AR
SAULT STE MARIE/NWSO
TRAVERSE CITY/FAA AIRPORT
CfflCAGO/O'HARE INT'L ARPT
GREEN BAY/AUSTIN STRAUBEL FIE
MILWAUKEE/GENERAL MITCHELL FI
DETROIT/METROPOLITAN ARPT
ALPENA/PHELPS COLLINS AP
DETROIT/CITY AIRPORT
FLINT/BISHOP ARPT
LANSING/CAPITAL CITY ARPT
TOLEDO/EXPRESS ARPT
States
NASHVILLE/METRO ARPT
PADUCAH/WSO AIRPORT
OH original
NY
NY
PA
MI SIS
IN
MI
MI
MI
IT. original
WI
WI
MI new
MI
MI
MI
MI
OH
TN SIS
KY
10
12
11
10
11
10
10
9
NA
9
10
11
10
8
NA
10
11
10
8
NA
B
A
B
B
W
A
A
A
A
A
A
A
A
W
W
A
A
A
B
B
19/42
14/37
15/37
17/38
9/23
12/31
11/27
13/28
11/31
11/29
10/27
11/29
11/27
9/25
9/25
10/30
10/28
14/33
16/32
18/33
13/63/24
11/67/21
13/64/24
NA
12/66/22
13/62/25
13/61/26
NA
NA
14/59/27
14/57/29
NA
12/62/26
NA
NA
13/61/26
NA
NA
20/44/36
NA
2 yrs data
4 yrs data
4 yrs data
3 yrs data
3 yrs data
(continued)
-------
Table Dl-1. (continued)
Station
No.
13963
13968
13964
13985
93997
03928
13995
13967
13994
93817
93821
03945
03966
14922
94822
14913
14918
14925
14914
14936
14991
14920
14837
14935
14943
13984
13996
Station Name
LITTLE ROCK/ADAMS FIELD
TULSA/INT'LARPT
FORT SMITH/MUNICIPAL ARPT
DODGE CITY/MUNICIPAL ARPT
RUSSELL/FAA AIRPORT
WICHITA/MID-CONTINENT ARPT
SPRINGFIELD/REGIONAL ARPT
OKLAHOMA CITY/WILL ROGERS WOR
ST LOUIS/LAMBERT INT'L ARPT
EVANSVILLE/DRESS REGIONAL ARP
LOUISVILLE/STANDIFORD FIELD
COLUMBIA/REGIONAL ARPT
ST LOUIS/SPIRIT OF ST LOUIS
MINNEAPOLIS-ST PAUL/INT'L ARP
ROCKFORD/GREATER ROCKFORD ARP
DULUTH/INTL ARPT
INTERNATIONAL FALLS/INTL ARP
ROCHESTER/MUNICIPAL ARPT
FARGO/HECTOR FIELD
HURON/REGIONAL ARPT
EAU CLAIRE/FAA AIRPORT
LA CROSSE/MUNICIPAL ARPT
MADISON/DANE CO REGIONAL ARPT
GRAND ISLAND/ARPT
SIOUX CITY/MUNICIPAL ARPT
CONCORDIA/BLOSSER MUNICIPAL A
TOPEKA/MUNICIPAL ARPT
State Status
AR original
OK SIS
AR
KS
KS
KS
MO
OK
MO new
IN
KY
MO
MO
MN original
IL
MN
MN
MN
ND
SD
WI
WI
WI
NE original
IA
KS
KS
Wind
Speed
(knots)
7
11
6
14
NA
12
10
12
10
9
8
9
NA
11
9
11
9
12
13
12
NA
NA
9
12
11
13
11
Wind-Rose
Bin"
W
B
B
B
B
C
B
C
A
W
A
B
A
A
B
A
W
A
A
A
W
A
B
B
A
A
A
Wind
Directionality0
8/23
19/42
16/38
18/37
15/35
21/39
19/42
21/45
10/25
8/22
11/28
16/34
10/23
10/23
17/29
11/27
9/25
12/28
14/32
13/31
7/20
14/31
15/28
15/31
14/27
12/29
10/28
Stability Class"
NA
15/53/31
NA
13/65/22
NA
13/59/27
17/51/31
14/59/27
16/54/29
18/48/34
NA
17/52/31
NA
14/59/28
13/60/28
12/64/25
NA
NA
NA
NA
NA
NA
NA
14/57/29
NA
NA
NA
Notes
in valley between
mountain groups
4 yrs data
3 yrs data
4 yrs data
4 yrs data
a.k.a. Lincoln
(continued)
-------
Table Dl-1. (continued)
Station
No.
03947
14939
14941
94918
24023
14942
14944
23062
93037
23066
23065
24018
24011
24037
24013
94014
24025
24033
94008
24143
24089
24028
24090
24021
24029
93815
14827
93819
14895
14821
Station Name
KANSAS CITY/INTL ARPT
LINCOLN/MUNICIPAL ARPT
NORFOLK/KARL STEFAN MEM ARPT
NORTH OMAHA/NWSFO ARPT
NORTH PLATTE/LEE BIRD FLD
OMAHA/EPPLE Y AIRFIELD
SIOUX FALLS/FOSS FIELD
DENVER/STAPLETON INT'L ARPT
COLORADO SPRINGS/MUNICIPAL AR
GRAND JUNCTION/WALKER FIELD
GOODLAND/RENNER FIELD
CHEYENNE/MUNICIPAL ARPT
BISMARCK/MUNICIPAL ARPT
MILES CITY/MUNICIPAL ARPT
MINOT/FAA AIRPORT
WILLISTON/SLOULIN INTL ARPT
PIERRE/FAA AIRPORT
BILLINGS/LOGAN INT'L ARPT
GLASGOW/INTL ARPT
GREAT FALLS/INTL ARPT
CASPER/NATRONA CO INT'L ARPT
SCOTTSBLUFF/COUNTY AIRPORT
RAPID CITY/REGIONAL ARPT
LANDER/HUNT FIELD
SHERIDAN/COUNTY ARPT
DAYTON/INT'L ARPT
FORT WAYNE/BAER FIELD
INDIANAPOLIS/INTL ARPT
AKRON/AKRON-CANTON REGIONAL
COLUMBUS/PORT COLUMBUS INTL
State Status
MO
NE
NE
NE
NE
NE
SD
CO original
CO
CO
KS
WY
ND original
MT
ND
ND
SD
MT SIS
MT
MT
WY original
NE
SD
WY
WY
OH new
IN
IN
OH
OH
Wind
Speed
(knots)
11
10
NA
NA
11
10
NA
8
10
8
12
13
12
9
NA
9
NA
10
11
13
14
11
15
8
11
10
11
9
9
8
Wind-Rose Wind
Bin"
B
A
A
A
A
B
W
A
A
B
A
B
W
A
A
W
A
C
B
C
C
C
B
A
A
A
A
A
A
W
Directionality0
15/34
13/30
11/27
11/31
11/26
18/38
9/24
14/34
12/33
16/38
13/30
16/40
9/24
12/27
13/31
8/22
11/27
24/41
16/32
26/52
26/49
22/40
16/40
11/27
13/32
11/28
13/27
11/28
12/31
7/21
Stability Class"
15/56/29
NA
NA
NA
NA
NA
NA
25/38/37
NA
NA
NA
13/63/24
14/53/33
18/50/32
NA
NA
NA
17/60/23
NA
NA
13/61/26
NA
NA
NA
NA
15/57/28
NA
16/54/30
13/60/26
15/53/31
Notes
a.k.a. Boulder 94018
3 yrs data
3 yrs data
4 yrs only
(continued)
-------
Table Dl-1. (continued)
Station
No.
14852
94823
94910
14933
14940
14923
14842
93822
Station Name
YOUNGSTOWNMUNICIPAL ARPT
PITTSBURGH/WSCOM 2 AIRPORT
WATERLOO/MUNICIPAL ARPT
DES MOINES/INTL ARPT
MASON CITY/FAA AIRPORT
MOLINE/QUAD-CITY ARPT
PEORIA/GREATER PEORIA ARPT
SPRINGFIELD/CAPITAL ARPT
State Status
OH
PA
IA new
IA
IA
IL
IL
IL
Wind
Speed
(knots)
10
10
11
11
NA
11
9
11
Wind-Rose
Bin"
A
A
A
A
A
A
A
A
Wind
Directionality0
11/28
10/29
12/27
12/28
11/26
10/25
14/29
13/30
Stability Class" Notes
13/62/25
13/57/29
NA
NA
NA 4 yrs data
13/58/29
15/56/29
14/59/27
Alaska
25309
26451
26409
27502
27401
26615
26533
25624
26411
25507
25503
25501
JUNEAU/INT'L ARPT
ANCHORAGE/WSMO AIRPORT
ANCHORAGE
BARROW/W POST-W ROGERS ARPT
BARTER ISLAND/WSO AIRPORT
BETHEL/WSO AIRPORT
BETTLES/BETTLES FIELD
COLD BAY/ARPT
FAIRBANKS/INTL ARPT
HOMER/ARPT
KING SALMON/ARPT
KODIAK/USCGBASE
AK new
AK new
AK
AK
AK
AK
AK
AK
AK
AK
AK
AK
NA
8
6
11
C
A
21/43
12/29
NA 3 yrs data, large facility
in the Toxics Release
Inventory (TRI), unique
location due to coastal
mountains
NA multiple facilities in
TRI, unique wind
regime due to location
surrounded by
mountains and water
(continued)
-------
Table Dl-1. (continued)
Station
No.
26616
26510
26617
26442
25339
Station Name
KOTZEBUE/RALPH WEIN MEMORIAL
MC GRATH/ARPT
NOME/MUNICIPAL ARPT
VALDEZ/WSO
YAKUTAT/STATE ARPT
State Status
AK
AK
AK
AK
AK
Wind
Speed
(knots)
6
8
8
Wind-Rose
Bin"
Wind
Directionality0
Stability Class" Notes
Hawaii
22521
21504
22536
Puerto
11641
HONOLULU/INT'L ARPT
HILO/GENERAL LYMAN FIELD
LIHUE/ARPT
Rico
SAN JUAN/ISLA VERDE INT'L ARP
ffl new
HI
HI
PR new
NA
NA
NA
11
C
B
C
C
39/66
16/37
34/69
22/56
NA
NA winds affected by
mountains, so not
representative of entire
island
NA 3 yrs data, adequately
represented by Honolulu
NA
a International Station Meteorological Climate Summary (ISMCS) value unrealistically low; estimated from wind-rose data.
b Key to wind-rose bins:
W: Weakly directional, one-directional wind < 10%
A: Mildly directional, one-directional wind 10-14%
B: Moderately directional, one-directional wind 15-20%
C: Strongly directional, one-directional wind > 20%
c % in 1 direction/% in 3 directions
d % Unstable/% Neutral/% Stable
-------
-&EPA Industrial Waste Air Model
(IWAIR) User's Guide
United States
Environmental Protection
Agency
-------
Solid Waste and EPA 530-R-02-011
Emergency Response August 2002
(5306W) www.epa.gov/industrialwaste
-------
February 2002
Industrial Waste Air Model (IWAIR)
User's Guide
Office of Solid Waste
U.S. Environmental Protection Agency
Washington, DC 20460
Printed on Recycled Paper
-------
-------
IWAIR User's Guide Table of Contents
Contents
Section Number
List of Figures v
List of Tables vi
List of Acronyms and Abbreviations vii
1.0 Introduction 1-1
1.1 Guide for Industrial Waste Management and IWAIR 1-1
1.2 Model Design 1-2
1.2.1 Emission Model 1-2
1.2.2 Dispersion Model 1-4
1.2.3 Risk Model 1-4
1.3 Overview of Approach to Estimating Risk or Allowable Concentration 1-5
1.4 Capabilities and Appropriate Application of the Model 1-8
1.5 About This User's Guide 1-10
2.0 Getting Started 2-1
2.1 Hardware and Software Requirements 2-1
2.2 Installing and Uninstalling the Program 2-1
2.3 Running IWAIR 2-3
2.4 Navigating in IWAIR 2-3
2.5 Menus 2-7
2.5.1 Start a New Analysis 2-7
2.5.2 Save and Re-Open an Analysis 2-7
2.5.3 Print Reports 2-9
2.5.4 Exit IWAIR 2-10
2.6 Online Help 2-10
2.7 Troubleshooting 2-10
3.0 Selecting Calculation Method, WMU Type, and Modeling Pathway 3-1
3.1 Selecting Calculation Method 3-1
3.2 Selecting WMU Type 3-2
3.3 Determining Appropriate Modeling Pathway 3-3
4.0 Completing Risk/Hazard Quotient Calculations 4-1
4.1 Method, Meteorological Station, WMU (Screen 1A) 4-6
4.2 Wastes Managed (Screen 2A) 4-10
4.3 Enter WMU Data for Using CHEMDAT8 Emission Rates 4-15
4.4 Emission Rates 4-23
4.4.1 Using CHEMDAT8 Emission Rates (Screen 4A) 4-24
4.4.2 User-Specified Emission Rates (Screen 4B) 4-25
in
-------
IWAIR User's Guide Table of Contents
Contents (continued)
Section Number
4.5 Dispersion Factors 4-26
4.5.1 Using ISCST3 Default Dispersion Factors (Screen 5A) 4-26
4.5.2 User-Specified Dispersion Factors (Screen 5B) 4-29
4.6 Risk Results (Screen 6) 4-30
5.0 Completing Allowable Waste Concentration Calculations 5-1
5.1 Method, Meteorological Station, WMU (Screen 1A) 5-7
5.2 Wastes Managed (Screen 2A) 5-11
5.3 Enter WMU Data for Using CHEMDAT8 Emission Rates 5-15
5.4 Emission Rates 5-21
5.4.1 Using CHEMDAT8 Emission Rates (Screen 4A) 5-22
5.4.2 User-Specified Emission Rates (Screen 4B) 5-24
5.5 Dispersion Factors 5-24
5.5.1 Using ISCST3 Default Dispersion Factors (Screen 5A) 5-25
5.5.2 User-Specified Dispersion Factors (Screen 5B) 5-27
5.6 Allowable Concentration Results (Screen 6) 5-29
6.0 Example Calculations 6-1
6.1 Calculation of Risk and Hazard Quotient 6-1
6.2 Calculation of Allowable Concentration 6-5
7.0 References 7-1
Appendix A Considering Risks from Indirect Pathways A-l
Appendix B Parameter Guidance B-l
Appendix C Physical-Chemical Property Values C-l
IV
-------
IWAIR User's Guide Table of Contents
Figures
Number Page
1-1 IWAIR approach for estimating risk or allowable waste concentrations 1-6
2-1 Menu bar in the IWAIR program 2-6
3-1 Receptor Locations 3-6
4-1 IWAIR approach for completing risk calculations, Pathway 1: Using CHEMDAT8
emission rates and ISCST3 default dispersion factors 4-2
4-2 IWAIR approach for completing risk calculations, Pathway 2: Using CHEMDAT8
emission rates and user-specific dispersion factors 4-3
4-3 IWAIR approach for completing risk calculations, Pathway 3: Using user-specified
emission rates and ISCST3 default dispersion factors 4-4
4-4 IWAIR approach for completing risk calculations, Pathway 4: Using user-specified
emission rates and dispersion factors 4-5
5-1 IWAIR approach for completing allowable waste concentration calculations,
Pathway 1: Using CHEMDAT8 emission rates and ISCST3 default dispersion
factors 5-3
5-2 IWAIR approach for completing allowable waste concentration calculations,
Pathway 2: Using CHEMDAT8 emission rates and user-specified dispersion
factors 5-4
5-3 IWAIR approach for completing allowable waste concentration calculations,
Pathway 3: Using user-specified emission rates and ISCST3 default dispersion
factors 5-5
5-4 IWAIR approach for completing allowable waste concentration calculations,
Pathway 4: Using user-specified emission rates and dispersion factors 5-6
-------
IWAIR User's Guide Table of Contents
Tables
Number Page
1-1 Constituents Included in IWAIR 1-3
2-1 IWAIR Tabs and Associated Screens 2-5
2-2 Troubleshooting Common Problems in IWAIR 2-10
6-1 Inputs Used for Example Calculation: Landfill 6-2
6-2 Parameter Values Used in Estimating Time-Weighted-Average Exposure 6-4
6-3 Unitized Emission Rates for Allowable Concentration Mode Example Calculation
([g/m2-s]/[mg/kg]) 6-6
VI
-------
IWAIR User's Guide
Table of Contents
Acronyms and Abbreviations
ATSDR Agency for Toxic Substances and Disease Registry
BAF Bioaccumulation factor
BCF Bioconcentration factor
BOD Biological oxygen demand
CAA Clean Air Act
CalEPA California Environmental Protection Agency
CAS Chemical Abstract Service
COD Chemical oxygen demand
CSF Cancer slope factor
DCOM Distributed component model
EPA Environmental Protection Agency
HEAST Health Effects Assessment Summary Tables
HQ Hazard quotient
HSDB Hazardous Substances Databank
IRIS Integrated Risk Information System
ISCST3 Industrial Source Complex, Short-Term Model, Version 3
IWAIR Industrial Waste Air Model
IWEM Industrial Waste Management Evaluation Model
MLVSS Mixed-liquor volatile suspended solids
MLSS Mixed-liquor suspended solids
MRL Minimum risk level
PAH Polycyclic Aromatic Hydrocarbons
RfC Reference concentration
REL Reference exposure level
SCDM Superfund Chemical Data Matrix
TOC Total organic carbon
TSS Total suspended solids
WMU Waste management unit
vn
-------
-------
IWAIR User's Guide Section 1.0
1.0 Introduction
This document describes how to use the Industrial Waste Air Model (IWAIR). A
companion document, the Industrial Waste Air Model Technical Background Document,
provides technical background information. This section of the User's Guide provides an
overview of IWAIR, its purpose, operation, and application; describes the three major
components of the system—the emissions, dispersion, and results models; and provides an
overview of the remainder of the User's Guide.
1.1 Guide for Industrial Waste Management and IWAIR
The U.S. Environmental Protection Agency (EPA) and representatives from 12 state
environmental agencies developed a voluntary Guide for Industrial Waste Management
(hereafter, the Guide) to recommend a baseline of protective design and operating practices to
manage nonhazardous industrial waste throughout the country. The guidance is designed for
facility managers, regulatory agency staff, and the public, and it reflects four underlying
objectives:
• Adopt a multimedia approach to protect human health and the environment;
• Tailor management practices to risk in the enormously diverse universe of waste,
using the innovative, user-friendly modeling tools provided in the Guide;
• Reaffirm state and tribal leadership in ensuring protective industrial waste
management, and use the Guide to complement state and tribal programs;
• Foster partnerships among facility managers, the public, and regulatory agencies.
The Guide recommends best management practices and key factors to consider to protect
groundwater, surface water, and ambient air quality in siting, operating, and designing waste
management units (WMUs); monitoring WMUs' impact on the environment; determining
necessary corrective action; closing WMUs; and providing postclosure care. In particular, the
guidance recommends risk-based approaches to choosing liner systems and waste application
rates for groundwater protection and to evaluating the need for air controls. The CD-ROM
version of the Guide includes user-friendly air and groundwater models to conduct these risk
evaluations.
Chapter 5 of the Guide, entitled "Protecting Air Quality," highlights several key
recommendations:
1-1
-------
IWAIR User's Guide Section 1.0
• Adopt controls to minimize particulate emissions.
• Determine whether WMUs at a facility are addressed by Clean Air Act (CAA)
requirements and comply with those requirements.
• If WMUs are not specifically addressed by CAA requirements, use IWAIR to
assess risks associated with volatile air emissions from units.
• Implement pollution prevention programs, treatment measures, or emissions
controls to reduce volatile air emission risks.
EPA developed IWAIR and this User's Guide to accompany the Guide to evaluate
inhalation risks. Workers and residents in the vicinity of a unit may be exposed to volatile
chemicals from the unit in the air they breathe. Exposure to some of these chemicals at sufficient
concentrations may cause a variety of cancer and noncancer health effects (such as
developmental effects in a fetus or neurological effects in an adult). With a limited amount of
site-specific information, IWAIR can estimate whether specific wastes or waste management
practices may pose an unacceptable risk to human health.
1.2 Model Design
IWAIR is an interactive computer program with three main components: (1) an emission
model to estimate release of constituents from WMUs; (2) a dispersion model to estimate fate
and transport of constituents through the atmosphere and determine ambient air concentrations at
specified receptor locations; and (3) a risk model to calculate either the risk to exposed
individuals or waste constituent concentrations that can be protectively managed in the unit. The
program requires only a limited amount of site-specific information, including facility location,
WMU characteristics, waste characteristics, and receptor information. A brief description of
each component follows. The IWAIR Technical Background Document contains a more detailed
explanation of each.
1.2.1 Emission Model
The emission model uses waste characterization, WMU, and facility information to
estimate emissions for 95 constituents (identified in Table 1-1) for four types of units: land
application units, landfills, waste piles, and surface impoundments. You can also add chemical
properties to model additional chemical constituents. The emission model selected for
incorporation into IWAIR is EPA's CHEMDAT8 model. This model has undergone extensive
review by both EPA and industry representatives and is publicly available from EPA's Web page
(http://www.epa.gov/ttn/chief/software.html).
To facilitate emission modeling with CHEMDAT8, IWAIR prompts you to provide the
required waste- and unit-specific data. Once you have entered these data, the model calculates
and displays chemical-specific emission rates. If you decide not to develop or use the
CHEMDAT8 rates, you can enter your own site-specific emission rates (g/m2-s).
1-2
-------
IWAIR User's Guide
Section 1.0
Table 1-1. Constituents Included in IWAIR
CAS
Number
Compound Name
CAS
Number
Compound Name
75070 Acetaldehyde
67641 Acetone
75058 Acetonitrile
107028 Acrolein
79061 Acrylamide
79107 Acrylic acid
107131 Acrylonitrile
107051 Allyl chloride
62533 Aniline
71432 Benzene
92875 Benzidine
50328 Benzo(a)pyrene
75274 Bromodichloromethane
106990 Butadiene, 1,3-
75150 Carbon disulfide
56235 Carbon tetrachloride
108907 Chlorobenzene
124481 Chlorodibromomethane
67663 Chloroform
95578 Chlorophenol, 2-
126998 Chloroprene
10061015 cis-1,3-Dichloropropylene
1319773 Cresols (total)
98828 Cumene
108930 Cyclohexanol
96128 Dibromo-3-chloropropane, 1,2-
75718 Dichlorodifluoromethane
107062 Dichloroethane, 1,2-
75354 Dichloroethylene, 1,1-
78875 Dichloropropane, 1,2-
57976 Dimethylbenz[a]anthracene, 7,12-
95658 Dimethylphenol, 3,4-
121142 Dinitrotoluene, 2,4-
123911 Dioxane, 1,4-
122667 Diphenylhydrazine, 1,2-
106898 Epichlorohydrin
106887 Epoxybutane, 1,2-
111159 Ethoxyethanol acetate, 2-
110805 Ethoxyethanol, 2-
100414 Ethylbenzene
106934 Ethylene dibromide
107211 Ethylene glycol
75218 Ethylene oxide
50000 Formaldehyde
98011 Furfural
87683 Hexachloro-l,3-butadiene
118741 Hexachlorobenzene
77474 Hexachlorocyclopentadiene
67721 Hexachloroethane
78591 Isophorone
7439976 Mercury*
67561 Methanol
110496 Methoxyethanol acetate, 2-
109864 Methoxyethanol, 2-
74839 Methyl bromide
74873 Methyl chloride
78933 Methyl ethyl ketone
108101 Methyl isobutyl ketone
80626 Methyl methacrylate
1634044 Methyl tert-butyl ether
56495 Methylcholanthrene, 3-
75092 Methylene chloride
68122 N,N-Dimethyl formamide
91203 Naphthalene
110543 n-Hexane
98953 Nitrobenzene
79469 Nitropropane, 2-
55185 N-Nitrosodiethylamine
924163 N-Nitrosodi-n-butylamine
930552 N-Nitrosopyrrolidine
95501 o-Dichlorobenzene
95534 o-Toluidine
106467 p-Dichlorobenzene
108952 Phenol
85449 Phthalic anhydride
75569 Propylene oxide
110861 Pyridine
100425 Styrene
1746016 TCDD, 2,3,7,8-
630206 Tetrachloroethane, 1,1,1,2-
79345 Tetrachloroethane, 1,1,2,2-
127184 Tetrachloroethylene
108883 Toluene
10061026 trans-1,3-Dichloropropylene
75252 Tribromomethane
76131 Trichloro-l,2,2-trifluoroethane, 1,1,2-
120821 Trichlorobenzene, 1,2,4-
71556 Trichloroethane, 1,1,1-
79005 Trichloroethane, 1,1,2-
79016 Trichloroethylene
75694 Trichlorofluoromethane
121448 Triethylamine
108054 Vinyl acetate
75014 Vinyl chloride
1330207 Xylenes
*Chemical properties for both elemental and divalent forms of mercury are included.
1-3
-------
IWAIR User's Guide Section 1.0
1.2.2 Dispersion Model
IWAIR's second modeling component estimates dispersion of volatilized contaminants
and determines air concentrations at specified receptor locations, using default dispersion factors
developed with EPA's Industrial Source Complex, Short-Term Model, version 3 (ISCST3).
ISCST3 was run to calculate dispersion for a standardized unit emission rate (1 n-g/m2- s) to
obtain a dispersion factor, which is measured in |J,g/m3 per |J,g/m2 -s. The total air concentration
estimates are then developed by IWAIR by multiplying the constituent-specific emission rates
derived from CHEMDAT8 (or the rates you specified) with a site-specific dispersion factor.
Running ISCST3 to develop a new dispersion factor for each location/WMU is time consuming
and requires extensive meteorological data and technical expertise. Therefore, IWAIR
incorporates default dispersion factors developed using ISCST3 for many separate scenarios
designed to cover a broad range of unit characteristics, including
• 60 meteorological stations, chosen to represent the different climatic and
geographical regions of the contiguous 48 states, Hawaii, Puerto Rico, and parts
of Alaska;
• 4 unit types;
• 17 surface areas for landfills, land application units, and surface impoundments,
and 11 surface areas and 7 heights for waste piles;
• 6 receptor distances from the unit (25, 50, 75, 150, 500, 1,000 meters);
• 16 directions in relation to the edge of the unit (only the one resulting in the
maximum air concentration is used).
The default dispersion factors were derived by modeling each of these scenarios, then
choosing as the default the maximum dispersion factor of the 16 directions for each
WMU/surface area/height/meteorological station/receptor distance combination.
Based on the size and location of the unit you specify, IWAIR selects an appropriate
dispersion factor from the default dispersion factors in the model. If you specify a unit surface
area or height that falls between two of the sizes already modeled, an interpolation method will
estimate dispersion in relation to the modeled unit sizes.
Alternatively, you may enter a site-specific dispersion factor developed by conducting
independent modeling with ISCST3 or with a different model and proceed to the next step, the
risk calculation.
1.2.3 Risk Model
The third component combines the constituent's air concentration with receptor exposure
factors and toxicity benchmarks to calculate either the risk from concentrations managed in the
unit or the allowable waste concentration (Cwaste) in the unit that must not be exceeded to protect
1-4
-------
IWAIR User's Guide Section 1.0
human health. In calculating either estimate, the model applies default values for exposure
factors, including inhalation rate, body weight, exposure duration, and exposure frequency.
These default values are based on data presented in EPA's Exposure Factors Handbook (U.S.
EPA, 1997a) and represent average exposure conditions. IWAIR contains standard health
benchmarks (cancer slope factors [CSFs] for carcinogens and reference concentrations [RfCs] for
noncarcinogens) for 94 of the 95 constituents included in IWAIR.1 These health benchmarks are
obtained primarily from the Integrated Risk Information System (IRIS) and the Health Effects
Assessment Summary Tables (HEAST) (U.S. EPA, 2001, 1997b); for a complete list of sources,
see Appendix B, Section B.2.2.3. IWAIR uses these data to estimate risk or hazard quotients
(HQs) or to estimate allowable waste concentrations. You may override the IWAIR health
benchmarks with your own values.
1.3 Overview of Approach to Estimating Risk or Allowable Concentration
Figure 1-1 provides an overview of the stepwise approach you will follow to estimate risk
or allowable waste concentrations with IWAIR. The seven steps of the estimation process are
shown down the right side of the figure, and the user input requirements are specified to the left
of each step. As you provide input data, the program proceeds to the next step. Each step of the
estimation process is summarized below (later sections of this User's Guide provide more
detailed instructions):
1. Select Calculation Method. To begin, select one of two calculation
methods—risk or allowable concentration. Use the risk calculation to arrive at
chemical-specific and cumulative risk estimates; you must know the
concentrations of constituents in the waste to use this option. Use the allowable
concentration calculation method to estimate waste concentrations that may be
managed protectively in new units.
2. Identify Waste Management Unit. Four WMU types can be modeled: surface
impoundments, land application units, active landfills, and waste piles. For each
WMU, you will be asked to specify some design and operating parameters, such
as waste quantity, surface area, and depth for surface impoundments and landfills;
height for waste piles; and tilling depth for land application units. The amount of
unit-specific data needed as input will vary depending on whether you elect to
have IWAIR calculate CHEMDAT8 emission rates or enter your own. IWAIR
provides default values for several of the operating parameters that you may use,
if appropriate.
1 At the time IWAIR was released, no accepted health benchmark was available for 3,4-dimethylphenol
from the hierarchy of sources used to populate the IWAIR health benchmark database, nor were data available from
these sources to allow the development of a health benchmark with any confidence. In addition, IWAIR contains
chemical properties for both elemental and divalent forms of mercury, but contains a health benchmark only for
elemental mercury; no accepted benchmark was available for divalent mercury.
-------
IWAIR User's Guide
Section 1.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
• WMU information (e.g.,
operating parameters)
User Specifies:
• Constituents (choose up to 6)
• Concentration for risk calculation
User Specifies:
• Emission rate option
• Facility location for meteorological input
User Specifies:
• Dispersion factor option
• Receptor information (e.g., distance and type)
User Specifies:
• Risk level for allowable concentration
calculation
Risk calculation
or
Allowable waste concentration
calculation
T
Identify WMU
Land application unit
Waste pile
Surface impoundment, aerated
and quiescent
Landfill
Define the Waste Managed
Add/modify properties data, as
desired
CHEMDAT8
or
User-specified emission rates
Determine Dispersion Factors
Interpolated from ISCST3 default
dispersion factors
or
User-specified dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
T
Calculate Results
Risk Calculation
1. Chemical-specific carcinogenic risk
2. Chemical-specific noncarcinogenic risk
3. Total cancer risk
or
Allowable Waste Concentration
(CV3.t.) Calculation
* '-'waste f°r wastewaters (mg/L)
* Cwastefor solid wastes (mg/kg)
Figure 1-1. IWAIR approach for estimating risk or allowable waste concentrations.
This figure shows the steps in the tool to assist you in developing risk or
allowable waste concentration estimates.
1-6
-------
IWAIR User's Guide Section 1.0
3. Define the Waste Managed. If you choose to calculate chemical-specific risk
estimates, specify constituents and concentrations in the waste. If you choose to
calculate allowable waste concentrations, then specify only constituents of
concern (no concentrations). You can also add chemicals or modify chemical
property data in this step.
4. Determine Emission Rates. You can elect to develop CHEMDAT8 emission
rates or provide your own site-specific emission rates for use in calculations.
IWAIR will also ask for facility location information to link the facility's location
to one of the 60 IWAIR meteorological stations. Data from the meteorological
stations provide wind speed and temperature information needed to develop
emission estimates. In some circumstances, you may already have emissions
information from monitoring or from a previous modeling exercise. As an
alternative to using the CHEMDAT8 rates, you may provide your own site-
specific emission rates developed with a different model or based on emission
measurements.
5. Determine Dispersion Factors. You can provide site-specific dispersion factors
(|j,g/m3 per |o,g/m2-s) or have the model develop dispersion factors based on WMU
information that you specify and the IWAIR default dispersion data. These
dispersion factors are specific to the meteorological station selected. Because a
number of assumptions were made in developing the IWAIR default dispersion
data (for example, flat terrain was assumed), you may elect to provide site-specific
dispersion factors that can be developed by conducting independent modeling
with ISCST3 or with a different model. Whether you use IWAIR or provide
dispersion factors from another source, specify distance to the receptor from the
edge of the WMU, and the receptor type (i.e., resident or worker). These data are
used to define points of exposure and exposure duration.
6. Calculate Ambient Air Concentration. For each receptor, the model combines
emission rates and dispersion data to estimate ambient air concentrations for up to
six waste constituents you have specified.
7. Calculate Results. The model calculates results by combining estimated ambient
air concentrations at a specified exposure point with receptor exposure factors and
toxicity benchmarks. Presentation of results depends on whether you chose to
calculate risk or the allowable waste concentration.
Risk Calculation: Results are estimates of cancer and noncancer risks from
inhalation exposure to volatilized constituents in the waste. If risks are too high,
your options are to (1) implement unit controls to reduce volatile air emissions;
(2) implement pollution prevention programs or treatment measures to reduce
volatile compound concentrations before the waste enters the unit; or (3) conduct
a full, site-specific risk assessment to more precisely characterize risks from the
unit.
1-7
-------
IWAIR User's Guide Section 1.0
Allowable Concentration Calculation: Results are estimates of constituent
concentrations in waste that can be protectively managed in the unit so as not to
exceed a defined risk level (e.g., 1E-6 or an HQ of 1) for specified receptors.
This information should be used to determine preferred characteristics for wastes
entering the unit. There are several options if it appears that planned waste
concentrations may be too high: (1) implement pollution prevention programs or
treatment measures to reduce volatile compound concentrations in the waste;
(2) modify waste management practices to better control volatile compounds (for
example, use closed tanks rather than surface impoundments); or (3) conduct a
full site-specific risk assessment to more precisely characterize risks from the unit.
1.4 Capabilities and Appropriate Application of the Model
In many cases, IWAIR will provide a reasonable alternative to conducting a full-scale
site-specific risk analysis to determine if a WMU poses unacceptable risk to human health.
However, because the model can accommodate only a limited amount of site-specific
information, it is important to understand its capabilities and recognize situations when it may be
most appropriate to use in a specific way, when it may not be appropriate to use at all, or when
another model would be a better choice.
Capabilities
The model provides a reasonable, protective representation of volatile compound
inhalation risks associated with WMUs.
The model is easy to use and requires a minimal amount of data and expertise.
The model is flexible and provides features to meet a variety of user needs.
You can enter emission and/or dispersion factors derived from another model
(perhaps to avoid some of the limitations below) and still use IWAIR to conduct a
risk evaluation.
The model can calculate risk from specified waste concentrations or allowable
concentrations based on a target risk or HQ.
You can modify health benchmarks and target risk level, when appropriate and in
consultation with other stakeholders.
You can add additional volatile organic chemicals to the 95 chemicals included
with IWAIR.
-------
IWAIR User's Guide Section 1.0
Appropriate Applications
• Release Mechanisms and Exposure Routes. The model considers exposures from
breathing ambient air. It does not address potential risks attributable to particulate
releases, nor does it address risks associated with indirect routes of exposure (i.e,
noninhalation routes of exposure). Appendix A discusses the potential for
indirect risks. Additionally, in the absence of user-specified emission rates,
volatile emission estimates are developed with CHEMDAT8 based on unit- and
waste-specific data. The CHEMDAT8 model was developed to address only
volatile emissions from WMUs. The model does not account for all competing
removal mechanisms; specifically, runoff, erosion, and leaching are not modeled.
In so much as these competing processes actually occur, the model would tend to
slightly overestimate the volatile emissions.
• Waste Management Practices. Although you specify a number of unit-specific
parameters that have a significant impact on the inhalation pathway (e.g., size,
type, and location of WMU, which is important in identifying meteorological
conditions), the model cannot accommodate information concerning control
technologies, such as covers, that might influence the degree of volatilization
(e.g., whether a waste pile is covered immediately after application of new waste).
In this case, it may be necessary to generate site-specific emission rates and enter
those into IWAIR. In addition, IWAIR cannot be used to estimate emissions from
land application units using spray techniques for waste application; the emissions
model component for land application units is only applicable to tilled land
application units; again, in this case, it will be necessary to generate site-specific
emission rates and enter them into IWAIR. IWAIR also cannot be used to model
tanks; the surface impoundment component should not be used to model tanks, as
most tanks have some height above the ground, and the dispersion factors used in
IWAIR for surface impoundments are all for a ground-level source.
• Terrain and Meteorological Conditions. If a facility is located in an area of
intermediate or complex terrain or with unusual meteorological conditions, it may
be necessary to either generate site-specific air dispersion modeling results for the
site and enter those results into the program, or use a site-specific risk modeling
approach other than IWAIR. The model will inform you which of the 60
meteorological stations is used for a facility. If the local meteorological
conditions are very different from the meteorological conditions at the site chosen
by the model, it would be more accurate to choose a different model or enter a
different location that results in the selection of a more appropriate meteorological
station.
The terrain type surrounding a facility can influence air dispersion modeling
results and, ultimately, risk estimates. In performing air dispersion modeling to
develop the IWAIR default dispersion factors, it was assumed that the facility was
located in an area of flat terrain. The Guideline on Air Quality Models (U.S. EPA,
1-9
-------
IWAIR User's Guide Section 1.0
1993) can assist you in determining whether a facility is in an area of simple,
intermediate, or complex terrain.
• Receptor Type and Location. IWAIR has predetermined worker and resident
receptors and predetermined exposure factors. The program cannot be used to
characterize risk for other possible exposure scenarios. The model contains
dispersion factors for six receptor locations. IWAIR cannot evaluate other
receptor locations unless you enter your own dispersion factors.
1.5 About This User's Guide
The focus of this User's Guide is to help you understand how to use IWAIR. The
remainder of this document is organized into five sections and three appendices:
• Section 2, Getting Started, identifies system requirements for running IWAIR,
provides stepwise guidance for installing the program, and introduces you to
program screens and navigational tools (e.g., tabs, menus, and buttons). This
section covers saving and retrieving data and printing reports. It also includes a
troubleshooting guide.
• Section 3, Selecting Calculation Method, WMUType, and Modeling Pathway,
assists you in selecting the appropriate calculation method (i.e., calculation of risk
estimates or calculation of allowable waste concentration), WMU type, and
modeling pathway. This section describes the types of units IWAIR addresses.
With both risk and allowable concentration calculations, you can select from the
following four modeling pathways:
— Pathway 1: Using CHEMDAT8 emission rates and ISCST3 default
dispersion factors
— Pathway 2: Using CHEMDAT8 emission rates and user-specified
dispersion factors
— Pathway 3: Using user-specified emission rates and ISCST3 default
dispersion factors
— Pathway 4: Using user-specified emission rates and dispersion factors.
Depending on the calculation method, you will be directed to follow the detailed
guidance provided in Section 4 for completing a risk calculation or in Section 5
for completing an allowable concentration calculation. Each of these sections
provides pathway-specific guidance, as needed.
1-10
-------
IWAIR User's Guide Section 1.0
• Section 4, Completing Risk/Hazard Quotient Calculations., provides detailed
guidance to develop risk estimates for wastes of known chemical concentration(s).
Follow the screen-by-screen guidance to arrive at risk estimates.
• Section 5, Completing Allowable Waste Concentration Calculations., provides
detailed guidance to predict allowable waste levels based on a user-specified risk
level. Again, follow the screen-by-screen guidance to complete an allowable
concentration calculation.
• Section 6, Example Calculations, provides a detailed example of how the program
calculates air concentration and inhalation risk or allowable waste concentrations.
It does not cover emission or dispersion calculations.
• Appendix A, Considering Risks from Indirect Pathways, describes the types of
pathways by which an individual may be exposed to a contaminant, explains
which pathways are accounted for in IWAIR, and discusses exposures
unaccounted for in IWAIR.
• Appendix B, Parameter Guidance, describes and provides additional information
on all parameter values needed to run IWAIR.
• Appendix C, Physical-Chemical Property Values, provides molecular weights and
densities for IWAIR constituents.
A separate document, Industrial Waste Air Model Technical Background Document,
provides detailed discussions on the CHEMDAT8 emission model, the ISCST3 model and
modeling efforts conducted to develop the IWAIR default dispersion factors, and health
benchmarks included in IWAIR.
1-11
-------
-------
IWAIR User's Guide Section 2.0
2.0 Getting Started
2.1 Hardware and Software Requirements
The IWAIR tool consists of a 32-bit Visual Basic application and an Access 2000
database. It is designed to run on an IBM-compatible computer with Windows 95, 98, NT4, or
2000. The recommended hardware configuration to run IWAIR includes at least 32 MB of RAM
(preferably 64 MB), a Pentium 120 MHz CPU processor (preferably Pentium n or above), and 30
MB of free hard-drive space (preferably 50 MB).
The most recent version of the appropriate Windows operating system must be installed
on the computer. As of the publication of this document, the most recent versions are Windows
95B, Windows 98 SE, Windows NT4 with Service Pack 6a, and Windows 2000 with Service
Pack 2. Service packs are available from the Microsoft Web site (www.microsoft.com).
Microsoft recommends that these service packs be re-installed after any software is installed or
uninstalled. If the computer is running Windows 95B or Windows 98SE, the distributed
component model (DCOM) software also must be installed. This software is available from the
Microsoft Web site (www.microsoft.com/com/dcom/dcom95/dcoml_3.asp for Windows 95,
www.microsoft.com/com/dcom/dcom98/dcoml_3.asp for Windows 98). The program does not
require any additional software when running under Windows NT or Windows 2000 (other than
the latest service packs mentioned above).
2.2 Installing and Uninstalling the Program
You receive the IWAIR computer program on the Guidance CD-ROM. The installation
consists of three files: setup.exe, setup.1st, and iwair.cab. Depending on the security settings of
your operating system, this software may need to be installed and uninstalled by someone with
administrator privileges. Instructions for installing and uninstalling the program are provided
below. Any updated instructions are located on the Guidance CD-ROM in readme.txt.
Installing
1. Close all applications, such as word processors and e-mail programs. Close or
disable virus protection software.1
2. Insert the CD-ROM into your CD-ROM drive.
1 Many vims protection programs interfere with or slow down the installation of software. You should scan
any software files for viruses before installing.
-------
IWAIR User's Guide Section 2.0
3. Open MY COMPUTER.
4. Select the CD-ROM drive.
5. Double-clickonsetup.exe.
6. You will see some files being copied to your hard drive. The WELCOME TO THE IWAIR
INSTALLATION PROGRAM screen then appears. If all your other applications were closed
(Step 1), then click |OK|.
7. The next screen is IWAIR SETUP. This screen displays the default location for the
IWAIR files to be installed. If you want to change the location, click the I CHANGE
DIRECTORY] button and specify a different directory. Otherwise, just click the large
button (shows a computer with an open box in front of it).
8. The next screen is IWAIR - CHOOSE PROGRAM GROUP. The default is to create a new
program group named "IWAIR." You can change the program group if you prefer
a different one. Press the I CONTINUE | button to install the program.
9. The next screen is IWAIR SETUP. The progress bar shows the progress of the files
that are being installed to your hard drive.
10. The final screen displays the message, "IWAIR setup was completed
successfully." Click on the I OKI button.
11. If you are using Windows 2000 or Windows NT4, you should install the latest
Service Pack.
12. Restart your computer.
OR
1. Close all applications, such as word processors and e-mail programs. Close or
disable virus protection software.2
2. Insert the CD-ROM into your CD-ROM drive.
3. Click on the Windows I START] button and select RUN.
4. Type "D:\SETUP" or, as appropriate, replace "D:" in this command with the
correct drive designation for your CD-ROM drive.
5. Proceed with Step 6 above.
2 Many vims protection programs interfere with or slow down the installation of software. You should scan
any software files for viruses before installing.
-------
IWAIR User's Guide Section 2.0
Uninstalling
1. Click on the Windows I START] button.
2. Select SETTINGS, and then CONTROL PANEL.
3. Select ADD/REMOVE PROGRAMS.
4. Select IWAIR and then CHANGE/REMOVE. When asked "Are you sure you want to
completely remove IWAIR and all of its components," select the I YES I button.
5. If you are using Windows 2000 or Windows NT4, you should re-install your latest
Service Pack and restart your computer.
2.3 Running IWAIR
To execute the program, press the Windows I START] button. Select PROGRAMS, IWAIR, IWAIR.
(If you selected a different name for the group during the installation process, you must select
PROGRAMS, then the group name you selected, then IWAIR.)
Begin working in IWAIR by clicking on the I START] button of the program title screen.
IWAIR can model one unit (choice of four unit types: surface impoundment, land application
unit, active landfill, and waste pile), up to six chemicals of concern, and up to five different
receptors during a single simulation. Once IWAIR's I START] button is selected, the program
automatically opens the METHOD, MET. STATION, WMU screen.
2.4 Navigating in IWAIR
The following tools facilitate interaction with the IWAIR program:
• Tabs
• Menus
• Command buttons
• Message prompts.
Each of these tools is explained in more detail in this section. Although this guide assumes the
use of a mouse to navigate through the screens and features, you may also navigate using key
strokes (see the "Navigation without the Mouse" explanation at the end of this section).
Tabs
Tabs facilitate navigation between the different screens in the program. Clicking a tab
opens the screen associated with it. You can enter information and edit data on an open screen.
There are six tabs, one for each of the following screens:
• METHOD, MET. STATION, WMU
-------
IWAIR User's Guide Section 2.0
WASTES MANAGED
WMU DATA FOR CHEMDAT8
EMISSION RATES
DISPERSION FACTORS
RESULTS.
Table 2-1 describes each of these tabs and how each screen associated with a tab assists
you in providing the program with the inputs needed to perform the calculations. The program
automatically opens the next screen after the required information is entered into the data fields
and the I DONE | command button is clicked.
At any time in the program, you can return to a screen that has already been visited by
clicking the tab associated with the screen. You can view information entered on the screen and
can also change any information entered on a previously visited screen. Changing data on a
previously visited screen has no effect on screens before the changed screen, but does affect
screens following the changed screen. Whenever you change data on a previously visited screen,
you will have to proceed through the following screens in order (even if the data on them have
been retained) to return to where you were before you went back and made the change; this is so
that calculated values will be recalculated with the new data. For example, if you were on the
EMISSION RATES screen and returned to the METHOD, MET STATION, WMU screen to change meteorological
stations, you would still have to proceed through the WASTES MANAGED and WMU DATA FOR CHEMDAT8
screens, clicking on | DONE |, to return to the EMISSION RATES screen. If you enter data on a screen,
return to a previous screen without clicking | DONE |, and make changes to the previous screen, the
new data you entered will be lost, and you will need to re-enter them when you return to the
screen you were working on. These data will not be lost if you do not change anything on the
previous screen and if you return to the subsequent screen using | TAB | rather than | DONE |.
Menus
As shown in Figure 2-1, a menu is also provided with IWAIR that allows you to perform
tasks such as starting a new run, loading data from a previous run, saving data from the current
run, printing reports, and exiting the program. The menu options are covered in detail in
Section 2.5.
Command Buttons
In addition to tabs and menus, one or more command buttons are provided on each screen
that initiate an action by the program. For instance, click the I DONE | command button after you
have entered all data on a screen to calculate and proceed to the next screen.
Message Prompts
The program uses message boxes to communicate important information and to confirm
actions before executing a command. For instance, an error message is shown when incorrect,
invalid, or incomplete information is entered.
2-4
-------
IWAIR User's Guide
Section 2.0
Table 2-1. IWAIR Tabs and Associated Screens
Tab
Description of Screen Associated with Tab
Method, Met.
Station, WMU
Select calculation method (i.e., risk calculation or allowable waste concentration
calculation).
Select WMU type. The WMU choices include surface impoundment, land application
unit, active landfill, and waste pile.
Enter zip code or latitude and longitude of site to allow the program to select the most
representative meteorological station from the program's 60 stations.
Select whether estimations will be made based on program-generated CHEMDAT8
emission rates and default ISCST3 dispersion factors, user-specified emission rates
and default dispersion factors, or a combination of both IWAIR-generated and user-
specified estimates.
Wastes Managed
Identify up to six chemicals that are present in the waste managed in the WMU of
concern. You can choose to view chemicals by CAS number or by chemical name (95
chemicals are included in the database that is installed with the IWAIR program).
Add or modify chemical data.
If you selected to perform a risk calculation and to use CHEMDAT8, you must
provide the concentration of each chemical in the WMU.
WMU Data for
CHEMDAT8
This tab is enabled and its associated screens are opened if you elected to have IWAIR
develop chemical-specific emission rates using EPA's CHEMDAT8 model. You must
provide a variety of site-specific data (e.g., unit dimensions and waste loading
information). Default values are provided adjacent to the data box for several of the input
parameters.
Emission Rates
View and confirm CHEMDAT8 emission rates or enter user-specified emission rates.
Enter source and justification for user-specified emission rates on this screen.
Dispersion Factors
Calculate dispersion factors or provide user-specified dispersion factors. Identify up to
five receptors (i.e., potentially exposed individuals). For each receptor, specify the
distance to the receptor and the receptor type (i.e., resident or worker). The program
calculates the dispersion factors based on distance to the receptor, as well as WMU area
and meteorological station. Alternatively, you may enter your own dispersion factors.
Enter source and justification for the user-supplied dispersion factors on this screen.
Results
Two different results screens are associated with this tab, one for risk calculation and one
for allowable concentration calculation. You can
• Select the receptor for which the calculation is to be performed.
• View the chemicals of concern that were selected under the WASTES MANAGED screen.
• View input data determined in the previous screen (distance from the unit to the
receptor, receptor type, and dispersion factors). IWAIR uses these data in the risk or
waste concentration calculations.
• View and override program-supplied health benchmarks. If you choose to override
these data, you should also provide the source and justification for the user-supplied
benchmarks.
• In the risk calculation mode, click the I CALCULATE | button to generate and display risk
estimates for carcinogens, and HQs for noncarcinogens.
• In the allowable concentration mode, select target risk level (e.g., 1E-5, 1E-6) and/or
an HQ (e.g., 0.5, 1) to serve as the starting point for the allowable concentration
calculation for each chemical. Then click the I CALCULATE | button to generate and
display the allowable waste concentrations for each chemical of concern.
2-5
-------
IWAIR User's Guide
Section 2.0
Industrial Waste - [la. Waste Management Unit Type ]
AIR
File Help
^
Open Analysis,,,
iave Analysis,,,
Print Report,,,
Exit
concentration
Rates
itmn, WMU T
I
Dispersion Factors
Results
Wastes Managed
WMU Data for CHEMDAT8
i Method
Calculation to estimate risk for specified
chemical concentrations
Calculation to estimate chemical
concentrations based on specified risk
3. Selection of Best Meteorological Station for Site -
(• Search by zip code
Search by latitude and longitude coordinates
-2. Select Waste Management Unit (WMU) Type
(» Surface impoundment
P Land application unit
r Active landfill
C Waste pile
R3 Industrial Waste -[la. Waste Management Unit Type ]
File Help
View Help for Screen
Ml Contents
T
'MU \
ispersion Factors
Wastes Managed
I
I
P g , |J
WMU Data for CH EM DATS
1
1. Select Calculation Method
Calculate risk
Calculate allowable
concentration
Calculation to estimate risk for specified
chemical concentrations
Calculation to estimate chemical
concentrations based on specified risk
3. Selection of Best Meteorological Station for Site -
(* Search by zip code
C Search by latitude and longitude coordinates
-2. Select Waste Management Unit (WMU) Type
f* Surface impoundment
C Land application unit
C Active landfill
C Waste pile
Figure 2-1. Menu bar in the IWAIR program.
Navigation without the Mouse
Although you typically navigate IWAIR's graphical user interface using a mouse or other
pointing device, the keyboard may be used to make selections and proceed through the screens.
The I TAB | key moves the cursor from one input box or control (e.g., command button, option
button, drop-down list) to the next. The I BACK-TAB | key (I SHIFT | + | TAB |) moves the cursor in the
reverse order on the current screen. When the cursor is on a command button, press the I ENTER |
key to "click" the button. Option buttons always appear in a set of at least two options; when the
cursor is on any option button, press a cursor arrow key to mark a different option button as
being selected and then use the I TAB | key to move out of that option button group. A drop-down
box displays one choice of several; when the cursor is on the box, use the up-arrow and down-
arrow keys to display the desired choice. At any time, you can press the | ALT| key to access the
FILE and HELP menus at the top of the window.
2-6
-------
IWAIR User's Guide Section 2.0
2.5 Menus
As shown in Figure 2-1, the IWAIR menu bar consists of two choices: FILE and HELP. HELP
is described in Section 2.6. The FILE menu options are described in this section.
The FILE menu provides the following features: start a new analysis, save and re-open an
analysis, print reports, and exit IWAIR. Each of these features is discussed below.
2.5.1 Start a New Analysis
During an IWAIR session, you may want to discard all data and start over with a new
analysis, so as to model a different WMU, different chemicals, or a different scenario. The NEW
ANALYSIS option lets you clear the current analysis without exiting and restarting IWAIR. It is not
necessary to select NEW ANALYSIS when you start IWAIR.
NEW ANALYSIS clears all entered data and resets IWAIR to initial defaults, with one
exception: the facility information for printed report headers is retained when you select NEW
ANALYSIS. This information may be edited when you print a report.
To start a new analysis, select FILE, NEW ANALYSIS. You will be prompted with "Discard all
changes and restart calculations?"
• Click on | YES I to start a new analysis.
• Click on | No I to return to your existing analysis.
2.5.2 Save and Re-Open an Analysis
You can save an analysis and re-open it later using the FILE, SAVE ANALYSIS and FILE, OPEN
ANALYSIS features. IWAIR saves all user-entered data, as well as calculated and user-override
emission rates and dispersion factors, and current facility information for report headers (if any
has been entered during the session). It does not save calculated values from the RESULTS screen
(air concentrations, risks, HQs, and allowable concentrations); these must be recalculated from
the RESULTS screen.
IWAIR does not save chemical properties data or user-defined health benchmarks with a
saved analysis, but uses the current chemical properties and user-defined health benchmark
values in the chemical database at the time an analysis is re-opened. Therefore, the results may
change if you have changed the chemical properties or user-defined health benchmarks of any
chemical in the saved analysis since you saved the analysis. Changes to user-defined health
benchmarks will be reflected when you recalculate the results, as you are required to do. Changes
to other chemical properties that affect emission rates will not be reflected unless you recalculate
emission rates by clicking | DONE | on the WMU DATA FOR CHEMDAT8 screen. In addition, the chemical
database must contain entries for all chemicals in the saved analysis, or the analysis will not
reload. This would only occur if you had saved an analysis containing user-defined chemicals,
then subsequently deleted any of those chemicals from the chemical database, or if you tried to
open a file saved by another user containing user-defined chemicals specific to his or her
2-7
-------
IWAIR User's Guide Section 2.0
chemical database and not found in yours. See Appendix A, Sections A.4.2 and A.5.2, for more
details on adding or modifying chemical data.
IWAIR can only reload analyses saved from the current version of IWAIR.
You can save an analysis only from the RESULTS screen. You can open a saved analysis
from any screen, but once the analysis is reloaded, you will be returned to the METHOD, MET. STATION,
WMU screen. You should then move through the tabs in sequence by clicking | DONE |, even if you
have not changed anything. This will recalculate your analysis (though you will have to re-enter
any user-override emission rates or dispersion factors) and ensure the accuracy of the results. If
you wish to view saved user-override emission rates or dispersion factors before you do this, you
can use the tabs to move directly to other screens without clicking | DONE | on each screen.
IWAIR was not designed to do calculations other than as part of a complete sequence through the
screens. Therefore, although you may be able to view results by recalculating only on the RESULTS
screen (without clicking through the previous screens using the I DONE | buttons), doing so may
result in model errors.
If an analysis fails to reload (either because it is missing a chemical or was saved from a
previous version of IWAIR), you will be returned to the METHOD, MET. STATION, WMU tab with all
values reset, as if you had selected NEW ANALYSIS.
To save the current analysis, navigate to the RESULTS screen, and select FILE, SAVE ANALYSIS.
This opens a SAVE As dialog box.
• Enter the desired file name in the FILE NAME box and click on | SAVE | to save the
analysis to a new file.
• Click on an existing file name and click on | SAVE | to save the analysis over an
existing file. You will be warned that the file already exists and asked if you want
to replace it.
- Click on | YES I to replace the existing file.
- Click on | No I to return to the SAVE As box and change the file name.
• Click on | CANCEL | to abort saving the analysis; you will be returned to the current
analysis.
To reload a previously saved analysis, select FILE, OPEN ANALYSIS. You will be prompted
with "You will lose unsaved data. Continue?"
• Click on | YES I to open a FILE OPEN dialog box; from this box, select the desired file
by clicking on it.
- Click on | OPEN I or double-click on the file name to open it. You may see
the IWAIR screens flashing on your screen as IWAIR reloads your data.
2-8
-------
IWAIR User's Guide Section 2.0
Click on | CANCEL | to abort opening a saved analysis and return to your
existing analysis.
• Click on | No I to return to your existing analysis.
2.5.3 Print Reports
You can print a report containing the data and results from the current analysis using the
PRINT REPORT function. Reports are divided into five sections:
• Part la: General Parameters. This section includes facility information;
information on the meteorological station, WMU type, and computation options
used; and WMU characteristics. The facility information for the header includes
facility name, facility type, address, date of sample analysis, name of user, and
additional information; you will be prompted to enter or edit this, if you desire,
before printing the report.
• Part Ib: Chemical Properties. This section includes the CAS number and all
chemical properties except health benchmarks for each chemical in the analysis.
• Part 2: Health Benchmark Information. This section includes the IWAIR and user-
defined health benchmarks and references for each chemical in the analysis.
• Part 3: Receptors and Dispersion Factors. This section includes the receptor data,
IWAIR and user-override dispersion factors, and exposure duration for each
receptor.
• Part 4: Final Results. This section includes the waste concentration, IWAIR and
user-override emission rates, and the risk and HQ for each chemical and receptor.
The exact data in each report vary somewhat depending on the type of WMU and the type of
analysis. The reports are 5 to 8 pages long, depending on how many chemicals and receptors you
have selected. The report only prints in full and to the default printer. You cannot print selected
pages or sections, nor can you print reports to a file.
The facility information you enter for the report header is retained until you exit IWAIR;
each time you print a report, you have the option to edit it. This information is saved in a saved
analysis; therefore, if you open a saved analysis, the saved information will overwrite the current
information.
You can print a report only once you have completed an analysis (i.e., you have reached
the RESULTS screen). Once you have done this, you can print a report from any screen (i.e., if you
have gone back to look at a previous screen); however, printing a report always returns you to the
RESULTS screen, regardless of where you printed from.
To print a report, select FILE, PRINT REPORT. You will be prompted with "Edit facility
information for report header?"
-------
IWAIR User's Guide
Section 2.0
• Click on | YES I to enter or edit facility information to be printed in the report
header.
• Click on | No I to retain the current facility information for the report header (or to
leave it blank if you have not entered facility information during the current
IWAIR session).
• Click on | CANCEL | to abort printing.
Once you have edited (or chosen not to edit) the facility information for the report header, you
will be prompted to "Click OK to route the reports to local printer." The report cannot be
aborted at this point. Reports are printed to the default printer defined on your system.
2.5.4 Exit IWAIR
To exit IWAIR, select FILE, EXIT, or click on the X in the upper right corner of the screen.
IWAIR will ask "Do you want to exit IWAIR?"
• Click on | YES I to exit IWAIR. Any unsaved data will be lost.
• Click on | No I to return to your analysis.
2.6 Online Help
The program provides online help that can be accessed from any screen, either by
pressing the IF11 key or by selecting the HELP menu. The IF11 key and the VIEW HELP FOR SCREEN
selection on the HELP menu display the information corresponding to Sections 4 and 5 of this
document that is pertinent to the currently displayed program screen. A hyperlink at the top of
the HELP screen brings up the parameter guidance help corresponding to Appendix B of this
document. In some cases, this may be preceded by hyperlinks for risk versus allowable
concentration calculations. The CONTENTS selection on the HELP menu displays the table of contents
for the online help.
2.7 Troubleshooting
Table 2-2 lists some common problems you may encounter and how to solve them.
Table 2-2. Troubleshooting Common Problems in IWAIR
Problem Category
Description of Problem
Solutions
Installation
Windows 95B and NT4 SP6a
ask to restart computer to
update Windows system
files.
Click on | YES |. After restart is complete, double-click on
setup.exe again to finish the install. Windows system files
updated will be in the system folders in the Windows
directory, and the old ones will be renamed
"filename.dll.old".
(continued)
2-10
-------
IWAIR User's Guide
Section 2.0
Table 2-2. (continued)
Problem Category
Description of Problem
Solutions
Windows NT4 SP6a, error
occurs installing
CRVIEWER.DLL.
Choose | IGNORE |, and the program will install completely.
This does not in any way affect the functionality of the
software.
Display
The gray screens in the
program appear "blotched"
and are not uniformly gray.
Changing your monitor's display settings will fix this
problem. Under the CONTROL PANEL, DISPLAY, SETTINGS
tab, make sure that the Color Pallette is set for High Color
(16 bit) or True Color (32 bit) or higher. Note that these
options may not be available on all machines, depending
on the type of monitor, graphics card, and video driver
used.
Screens are not displayed
correctly, display is not
optimized.
The IWAIR program display is optimized for screen
resolutions of 800 x 600 pixels. At lower resolutions, not
all of the IWAIR screens are displayed. The screens
appear smaller at higher resolutions.
Printing
Text is cut off at the edges.
Due to the large quantity of data to be displayed on the
reports, the margins selected for the reports are only 0.25
inches. Text may be cut off if the printer has a larger
unprintable area. Printing functions were tested on an HP
Laser Jet 4/4M and higher-grade printers.
Override values print in
reports even though no
override values were entered.
If no override values are entered, IWAIR may repeat the
calculated emission rates or dispersion factors in the
override column of the printed report.
Miscellaneous
Low system resources
message is displayed,
program crashes, program
runs slowly.
IWAIR may be unstable when other applications are also
open because of the memory required for running IWAIR.
Close all other applications before starting IWAIR to free
up the maximum resources for the program. If your
computer's resources are still low, reboot the computer
and restart IWAIR.
2-11
-------
-------
IWAIR User's Guide Section 3.0
3.0 Selecting Calculation Method, WMU Type,
and Modeling Pathway
3.1 Selecting Calculation Method
Each time you begin the program, select the mode of calculation. You can choose from
two calculation methods: risk and allowable concentration. Click on the option button associated
with either the risk calculation or the allowable concentration calculation mode. Each of these
options is discussed below.
Risk Calculation Method
The first calculation method, risk calculation, allows you to develop inhalation risk
estimates based on waste concentration levels that you specify. Results from the risk calculation
method include (1) chemical-specific cancer risk estimates, (2) total cancer risk estimates (i.e.,
the summation of the chemical-specific risk estimates), and (3) noncancer risk estimates (i.e.,
HQs for noncarcinogens in the waste). Use the risk calculation option to develop risk estimates
when you know the concentrations of the constituents in the waste. If the program results
indicate that the waste poses an unacceptable risk to exposed individuals, then you should
consider conducting a more site-specific analysis or implementing corrective measures to reduce
the fraction of constituents released to the atmosphere. Such measures could include
pretreatment of waste to reduce volatile chemical concentrations before the waste enters the unit
or applying unit control technologies or practices to reduce volatile air emissions. Chapter 5 of
the Guide for Industrial Waste Management, "Protecting Air Quality," identifies and discusses
some emission control options.
Allowable Concentration Calculation Method
The second calculation method is an allowable concentration calculation that results in
the development of waste concentrations (Cwaste) that are protective of human health when
managed as described. The calculation method can be applied in calculating waste
concentrations for both wastewaters (Cwaste in mg/L) and solid waste (Cwaste in mg/kg).
Concentrations are estimated based on user-defined target cancer and noncancer risk levels (e.g.,
IE-5 for carcinogens, or an HQ of 1 for noncarcinogens), which you will set on a later screen,
the RESULTS SCREEN. The program uses information gathered on the IWAIR screens to calculate for
each chemical an allowable waste concentration that would not pose an inhalation risk to the
receptor greater than the selected target level. You can use the allowable concentration
calculation option to estimate waste concentrations for a WMU that has not yet received a waste,
5-1
-------
IWAIR User's Guide Section 3.0
to determine what concentration(s) would pose an unacceptable risk to potentially exposed
individuals.
3.2 Selecting WMU Type
Identify the WMUs that are used to manage wastes of concern at your facility and run the
model separately for each WMU. Each of the four IWAIR unit types (described below) reflects
waste management practices that are likely to occur at Industrial Subtitle D facilities.
Surface Impoundment. In the IWAIR tool, surface impoundments are considered to be
ground-level, flowthrough units. The major source of volatile emissions associated with surface
impoundments is the uncovered liquid surface exposed to the air (U.S. EPA, 1991).
Impoundments can be quiescent (nonaerated) or aerated. Aeration or agitation is applied to aid in
the treatment of the waste. Emissions tend to increase with an increase in surface turbulence
because of enhanced mass transfer between the liquid and air (U.S. EPA, 1991). IWAIR can
conduct emission modeling for both aerated and nonaerated surface impoundments. Parameters
to which emissions are most sensitive include surface area, unit depth, waste concentration,
retention time, wind speed for quiescent systems, and biodegradation.
The surface impoundment component of the IWAIR tool should not be used to model
tanks. Although tanks have many common characteristics with surface impoundments with
respect to volatile emissions, tanks are usually aboveground units, and height of the unit above
the ground has a significant effect on dispersion factors. Therefore, the dispersion factors
included in IWAIR for surface impoundments (which are presumed to be ground-level) are
inappropriate for tanks and would produce erroneous results if so used.
Tilled Land Application Units. Wastes managed in land application units can be tilled or
sprayed directly onto the soil and subsequently mixed with the soil by discing or tilling. Waste in
a land application unit is a mixture of waste and soil. IWAIR allows the modeling of tilled land
application units only. Spray application was not included because the degree of volatilization
associated with this type of application practice is very site-specific and is influenced by a
number of variables, including meteorological conditions and application equipment. Therefore,
IWAIR is unsuitable for modeling spray land application units. Important characteristics for the
tilled land application unit include surface area (the exposed area from which volatile emissions
can be released) and the application rate (which affects the depth of the contamination, which,
along with area, defines the extent of the source for volatile emissions).
Landfills. IWAIR allows modeling of emissions released from the surface of an active
(i.e., receiving wastes) landfill. Volatilization can occur from the surface of the landfill.
Important unit characteristics for the landfill include surface area and unit depth. IWAIR
assumes that the landfill being modeled is a ground-level emission source.
Waste Piles. Waste piles are typically elevated sources used as temporary storage units
for solid wastes. Important characteristics for the waste pile include surface area and height.
These parameters define the exposed area from which volatile emissions can be released.
5-2
-------
IWAIR User's Guide Section 3.0
3.3 Determining Appropriate Modeling Pathway
Regardless of the calculation method selected (risk or allowable concentration),
determine which modeling pathway to follow in using the tool. After deciding on the appropriate
calculation method and modeling pathway, proceed to either Section 4 for detailed guidance on
completing risk calculations or Section 5 for guidance on allowable waste calculations.
You can choose from four pathways that provide you with the flexibility of conducting
modeling using IWAIR-generated emissions rates and dispersion factors, user-specified emission
and dispersion estimates, or a combination of both IWAIR-generated and user-specified
estimates:
• Pathway 1: Using CHEMDAT8 emission rates and ISCST3 default dispersion
factors
• Pathway 2: Using CHEMDAT8 emission rates and user-specified dispersion
factors
• Pathway 3: Using user-specified emission rates and ISCST3 default dispersion
factors
• Pathway 4: Using user-specified emission rates and dispersion factors.
In selecting a pathway, consider the availability of site-specific information. For
example, if you have access to a limited amount of site-specific data and do not have access to
emissions measurement data, then you will likely want to follow either Pathway 1 or 2 to allow
IWAIR to develop CHEMDAT8 emissions rates. Similarly, if you do not have the ability (i.e.,
resources or access to technical capabilities) to conduct site-specific air dispersion modeling,
then you will want to follow either Pathway 1 or 3 to allow IWAIR to develop dispersion factors.
If site-specific emission and dispersion rates are accessible or if resources are available to
develop these data, Pathway 4 will provide the most refined site-specific results.
Additionally, consider model assumptions and capabilities. Because a number of
assumptions are made by IWAIR in modeling emissions and dispersion, use of these features
may not be appropriate in all cases. Review the following overviews of CHEMDAT8 emission
modeling and ISCST3 default dispersion factors, as well as Section 1.4 on IWAIR's capabilities
and limitations, prior to choosing a pathway.
Using CHEMDAT8 Emission Rates
EPA's CHEMDAT8 model has been incorporated into the IWAIR program to assist you
in the development of chemical-specific emission rates. This model has undergone extensive
review by both EPA and industry representatives and is publicly available from EPA's Web page
(http://www.epa.gov/ttn/chief/software.html).
5-3
-------
IWAIR User's Guide
Section 3.0
CHEMDAT8 considers many of the
competing removal pathways that might limit
air emissions, including adsorption and
hydrolysis in surface impoundments and
biodegradation in all types of units.
Adsorption is the tendency of a chemical to
attach or bind to the surface of particles in the
waste and therefore to not volatilize into the
air. Biodegradation is the tendency of a
chemical to be broken down or decomposed
into less-complex chemicals by organisms in
the waste or soil; because this is a highly site-
specific process, IWAIR allows you to choose
whether to model biodegradation for all
WMU types. Similarly, hydrolysis is the
tendency of a chemical to be broken down or
decomposed into less-complex chemicals by
reaction with water. IWAIR does not model
these breakdown products produced as a
result of biodegradation or hydrolysis.
Chemicals that decompose by either
biodegradation or hydrolysis have lower
potential for volatile emission to the air.
Loss of contaminant by leaching or
runoff is not included in the CHEMDAT8
model. Both leaching and runoff are a
function of a chemical's tendency to become
soluble in water and follow the flow of water
(e.g., due to rainfall) down through the soil to
groundwater (leaching) or downhill to surface
water (runoff). These two mechanisms would
also result in less chemical being available for
volatile emission to the air. CHEMDAT8 is
considered to provide reasonable to slightly
high (environmentally conservative) estimates
of air emissions from the various emission
sources. See the IWAIR Technical
Background Document for a more detailed
discussion of the emissions modeling.
IWAIR Assumptions Made for
Modeling Volatile
Emissions with CHEMDAT8
• Annual average temperature is determined by
assigned meteorological station; user may override.
• Waste is homogeneous.
Quiescent and Aerated Surface Impoundment
Assumptions'.
• Flowthrough unit is operating at steady state.
• For aqueous-phase wastes, waste in the surface
impoundment is well mixed.
• Organic-phase wastes are modeled under plug flow
conditions.
• For aqueous-phase wastes, biodegradation rate is
first order with respect to biomass concentrations.
• For aqueous-phase wastes, biodegradation rate
follows Monod kinetics with respect to
contaminant concentrations.
• For aqueous-phase wastes, hydrolysis rate is first
order with respect to contaminant concentrations.
• For aqueous-phase wastes, biodegradation is
modeled by default; user may turn off.
Tilled Land Application Unit Assumptions:
• The volume of the land application unit remains
constant. As new waste is applied, an equal
volume of waste/soil mixture becomes buried or
otherwise removed from the active tilling depth.
• Biodegradation is modeled by default; user may
turn off.
• For organic-phase wastes, biodegradation and
hydrolysis are not modeled.
Landfill Assumptions:
• Only one cell is active at a time.
• The active cell is modeled as instantaneously filled
at time t = 0 and open for the life of the landfill
divided by the number of cells. Cells are either
depleted of the constituent or capped at the end of
this period.
• Biodegradation is not modeled by default; user
may turn on.
Waste Pile Assumptions:
• Waste pile operates with fixed volume.
• Waste pile is modeled as a square box with
essentially vertical sides.
• Biodegradation is not modeled by default; user
may turn on.
5-4
-------
IWAIR User's Guide
Section 3.0
Using ISCST3 Default Dispersion Factors
The IWAIR default dispersion factors
were developed by conducting air dispersion
modeling with EPA's ISCST3 (U.S. EPA,
1995). This model is capable of modeling
ground-level and elevated area sources. For
IWAIR, landfills, land application units, and
surface impoundments were modeled as
ground-level area sources and waste piles were
modeled as elevated area sources.
Because the ISCST3 model has
considerable run times for area sources,
modeling was conducted for a limited number
of WMUs of representative sizes (i.e., surface
areas, and heights for waste piles) using
meteorological data obtained from 60
meteorological stations. The representative
WMU sizes were selected from the range of
sizes seen in the 1985 Screening Survey of
Industrial Subtitle D Establishments
(Shroeder et al., 1987). This database was the
most comprehensive database that EPA had on waste unit characteristics. It contains data on
6,254 surface impoundments, 1,281 waste piles, 702 land application units, and 790 landfills.
The IWAIR program is designed to cover the range of unit characteristics contained in the
database. Specific areas to be modeled were selected from the skewed distribution of areas
found in the Industrial D Survey database so that all WMUs in the database would be adequately
represented and interpolation errors would be minimized. As a result, 17 surface areas were
selected for modeling for the landfills, land application units, and surface impoundments. Eleven
surface areas were selected for waste piles. In
addition, 7 heights were selected to be
modeled for waste piles, and waste piles were
modeled at all possible combinations of the
11 areas and 7 heights.
Assumptions Made for Dispersion Modeling
An area source was modeled for all WMUs.
To minimize error due to site orientation, a
square area source with sides parallel to x- and
y-axes was modeled.
Modeling was conducted using a unit emission
rate of 1 ug/nf-s.
Receptor points were placed on 25, 50, 75, 150,
500, and 1,000 m receptor squares starting from
the edge of the source, with 16 receptor points
on each square.
Dry and wet depletion options were not activated
in the dispersion modeling.
The rural option was used in the dispersion
modeling because the types of WMUs being
assessed are typically in nonurban areas.
Flat terrain was assumed.
The ISCST3 modeling was conducted
with data obtained from 60 meteorological
stations chosen to represent the various
climatic and geographical regions of the
contiguous 48 states, Hawaii, Puerto Rico,
and parts of Alaska. The dispersion modeling
was conducted using 5 years of data from
each of the 60 meteorological stations. The
meteorological data required as input to the
ISCST3 model included hourly readings for
Key Meteorological Data for
the ISCST3 Model without Depletion
Wind direction determines the direction of the
greatest impacts.
Wind speed is inversely proportional to ground-level
air concentration, so the lower the wind speed, the
higher the concentration.
Stability class influences rate of lateral and vertical
diffusion. The more unstable the air, the lower the
concentration.
Mixing height determines the maximum height to
which emissions can disperse vertically. The lower
the mixing height, the higher the concentration.
5-5
-------
IWAIR User's Guide
Section 3.0
the following parameters: wind direction, wind speed (m/s), ambient temperature (K), mixing
height, and stability class.
Dispersion factors were obtained as output by running the model with a unit emission rate
(i.e., 1 |j,g/m2-s). The selected areas for each type of WMU were modeled using meteorological
inputs obtained from the 60 representative meteorological locations. Receptors were placed in
16 directions at distances of 25, 50, 75, 150, 500, and 1,000 meters from the edge of the WMU.
Figure 3-1 illustrates the pattern of receptor placement around the unit for a 10,000 m2 unit; only
receptors at 150 m or less are shown for clarity reasons. Receptor placement was made based on
a sensitivity analysis that was conducted to determine the locations and spacings that would
provide adequate resolution without modeling an excessive number of receptors. The resulting
maximum annual average air concentrations at each distance serve as the IWAIR default
dispersion factors.
200 <
100 <
0)
*> o <
£
-100 <
-200 <
-2
> • 4
» • • •
*
> • 4
DO -100
> • 4
WMU
0
(meters)
> • 4
• • • 4
> • 4
>
>
>
100 200
Figure 3-1. Receptor Locations.
5-6
-------
IWAIR User's Guide Section 3.0
Based on the WMU surface area (and height, for waste piles) that you provide, the
IWAIR tool selects an appropriate dispersion factor. If the entered WMU surface area or height
lies between two modeled areas or heights, dispersion factors for the WMU are estimated by an
interpolation between dispersion factors for WMUs in the database with areas and heights above
and below that of the WMU area you entered. For example, if you specify a landfill with a
surface area of 8,000 m2, the program will determine that this surface area falls between two
modeled units with surface areas of 4,047 m2 and 12,546 m2. A linear interpolation method is
then applied to estimate a dispersion factor for the 8,000 m2 landfill, based on the default
dispersion factors stored in the IWAIR database for two similarly sized units. For waste piles, a
two-dimensional nonlinear interpolation method (called a spline) is used. See the IWAIR
Technical Background Document for more information on the spline approach.
5-7
-------
-------
IWAIR User's Guide Section 4.0
4.0 Completing Risk/Hazard Quotient
Calculations
IWAIR allows you to develop inhalation risk estimates for wastes of known chemical
concentrations. Results from the risk calculation method include chemical-specific cancer risk
estimates, total cancer risk estimates (i.e., the summation of the chemical-specific risk estimates),
and chemical-specific noncancer risk estimates (i.e., HQs for noncarcinogens in the waste).1
IWAIR is structured in a stepwise framework. Through the use of a series of screens,
IWAIR assists in selecting calculation options, identifying and entering required inputs, and
generating desired outputs. There are four different pathways you can follow in performing a
calculation:
• Pathway 1: Using CHEMDAT8 emission rates and ISCST3 default dispersion
factors
• Pathway 2: Using CHEMDAT8 emission rates and user-specified dispersion
factors
• Pathway 3: Using user-specified emission rates and ISCST3 default dispersion
factors
• Pathway 4: Using user-specified emission rates and dispersion factors.
Guidance for determining which modeling pathway to follow is provided in Section 3.3. The
stepwise approach employed by IWAIR to assist in calculating risk, whether you are following
Pathway 1, 2, 3, or 4, is shown in Figures 4-1, 4-2, 4-3, and 4-4, respectively. The seven steps of
the estimation process are shown down the right side of each figure, and the user input
requirements are specified to the left of each step. The types of input data required will vary
depending on the modeling pathway chosen. Screen-by-screen, IWAIR walks you through the
steps of a risk calculation to arrive at inhalation risk estimates.
This section provides screen-by-screen guidance that describes the data that are required
as input to each screen and the assumptions that are interwoven in the calculation being
performed. The guidance provided in this section will assist you in completing a risk calculation.
You will not need to reference all of the information provided in this section because the
guidance addresses all four of the modeling pathways. Follow only those subsections that are
applicable to your chosen pathway.
1 Noncancer risks are not summed across chemicals, because summation is only appropriate when the same
target organ is affected.
-------
IWAIR User's Guide
Section 4.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
User Specifies:
• Constituents (choose up to 6)
• Concentrations
User Specifies:
• CHEMDAT8 option
• Facility location for meteorological input
• WMU information (i.e., design and
operating parameters)
j
User Specifies: ^
• Receptor information (i.e., distance
and type) J
Define the Waste Managed
Add/modify chemical properties
data, as desired
Determine Dispersion Factors
Interpolated from ISCST3 default
dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Calculate Results
Risk Calculation
1. Chemical-specific carcinogenic risk
2. Chemical-specific noncarcinogenic risk
3. Total cancer risk
Figure 4-1. IWAIR approach for completing risk calculations, Pathway 1: Using
CHEMDAT8 emission rates and ISCST3 default dispersion factors.
4-2
-------
IWAIR User's Guide
Section 4.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
User Specifies:
• Constituents (choose up to 6)
• Concentrations
User Specifies:
• CHEMDAT8 option
• Facility location for meteorological input
• WMU information (i.e., design and
operating parameters)
User Specifies:
• Dispersion factors
• Receptor information (i.e., distance
and type) for reference only
Define the Waste Managed
Add/modify chemical properties
data, as desired
User-specified dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Calculate Results
Risk Calculation
1. Chemical-specific carcinogenic risk
2. Chemical-specific noncarcinogenic risk
3. Total cancer risk
Figure 4-2. IWAIR approach for completing risk calculations, Pathway 2: Using
CHEMDAT8 emission rates and user-specific dispersion factors.
4-3
-------
IWAIR User's Guide
Section 4.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
User Specifies:
• Constituents (choose up to 6)
Define the Waste Managed
Add/modify chemical properties
data, as desired
User Specifies:
• Emission rates
User-specified emission rates
User Specifies:
• WMU area (and height for waste pile)
• Facility location for meteorological input
• Receptor information (i.e., distance and
type)
Determine Dispersion Factors
Interpolated from ISCST3 default
dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Calculate Results
Risk Calculation
1. Chemical-specific carcinogenic risk
2. Chemical-specific noncarcinogenic risk
3. Total cancer risk
Figure 4-3. IWAIR approach for completing risk calculations, Pathway 3: Using user-
specified emission rates and ISCST3 default dispersion factors.
4-4
-------
IWAIR User's Guide
Section 4.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
User Specifies:
• Constituents (choose up to 6)
User Specifies:
• Emission rates
User Specifies:
• Dispersion factors
• Receptor information (e.g., distance
and type) for reference only
Define the Waste Managed
Add/modify chemical properties
data, as desired
Determine Emission Rates
User-specified emission rates
User-specified dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Calculate Results
Risk Calculation
1. Chemical-specific carcinogenic risk
2. Chemical-specific noncarcinogenic risk
3. Total cancer risk
Figure 4-4. IWAIR approach for completing risk calculations, Pathway 4: Using user-
specified emission rates and dispersion factors.
4-5
-------
IWAIR User's Guide
Section 4.0
A. Select
calculation
method
C. Select met
station search
option
Enter zip code
and search for
met station
Enter latitude
and longitude
and search for
met station
D. View
selected met
station
File Help
Emission R.ates | ' * i .dors j Results
Method, Met. Station, WMU } -ed J WMU Data for CHEMDAT3 1
i 1. Select Calculation Method p2. Select Waste Management Unit (WMU) Type _
(• fcaicuiate risk' Calculation to estimate risk for specified W
•4 ! ' chemical concentrations ** Surface impoundment
f* Calculate allowable Calculation to estimate chemical f Land application unit
concentration concentrations based on specified risk
1 C Active landfill
1 3. Selection of Best Meteorological Station for Site i ^ Waste pile
Y (* Search by zip code
f* Search by latitude and longitude coordinates
Enter 5 digit Zip Code of Site
' • Search
i . in ii ] .1 I i i 1 . ' i'.»
-» r r r
1 I
Selected Meteorological Station for Site
4 View Map
! 4. Select Emissions and Dispersion Option *
Use CHEMDAT8 to estimate emission ^
Use CHEMDAT8 rates and use dispersion factors
provided
1 OR 1
Enter Emission Directly enter emission rates without
_, using CHEMDAT8 and use disperion
factors provided
OR
Enter Emission & Directly enter emission rates and
Dispersion Data aspersion factors
- B. Select
WMU type
_ E. Select
emission and
dispersion
option
Screen 1A. Method, Meteorological Station, WMU
4.1 Method, Meteorological Station, WMU (Screen 1A)
A. Select Calculation Method (Screen 1A)
Select the calculation method by clicking on the | CALCULATE RISK | option button. Detailed
guidance for selecting the appropriate mode of calculation is provided in Section 3.1.
B. Select Waste Management Unit (WMU) Type (Screen 1A)
Identify the WMUs that are used to manage wastes of concern at your facility and run the
model separately for each unit type. The four unit types that are addressed as part of this
guidance include surface impoundments (aerated and quiescent), active landfills, waste piles, and
tilled land application units. A detailed description of these unit types is provided in Section 3.2.
Select one of the four WMU types shown in Screen 1A by clicking on the appropriate option
button.
C. Select Meteorological Station Search Option (Screen 1A)
The two search options available include searching by the site's 5-digit zip code or by its
latitude and longitude. Select the appropriate search option and enter the appropriate
information. This information is used to link the facility's location to one of the 60 IWAIR
meteorological stations. The 60 stations cover the 48 contiguous states, Hawaii, Puerto Rico, and
parts of Alaska. Data from the 60 stations (shown on maps in Screen IB, viewed by clicking on
4-6
-------
IWAIR User's Guide Section 4.0
the | VIEW AMP | button shown on Screen 1 A) were used as inputs to the air dispersion modeling
effort conducted to develop the default dispersion factors contained in the IWAIR tool. They are
also used as inputs to CHEMDAT8 emission modeling (e.g., temperature and wind speed).
Additional information on this air dispersion modeling effort and the 60 representative
meteorological stations is provided in Section 3.3.
Enter 5-Digit Zip Code and Search for Meteorological Station
Enter a 5-digit zip code and click on the | SEARCH | button to identify the default
meteorological station. If the zip code was entered incorrectly or if no data were provided
at all, message boxes will appear to indicate the specific problem that the tool
encountered so that you can supply the needed data. The zip code database includes zip
codes established through 1999. If your facility has a new zip code that was established
more recently, you will get an error message indicating that it is not a valid zip code
because it is not in IWAIR's database. If this occurs, you can use your old zip code, use a
nearby zip code, or select a meteorological station using latitude and longitude.
Enter Latitude and Longitude Information and Search for Meteorological Station
As shown in Screen 1 A, enter the latitude and longitude of the site in degrees, minutes,
and seconds. At a minimum, the program requires degrees for latitude and longitude to
be entered. If available, the minutes and seconds should be supplied to ensure that the
most appropriate station is selected for a site. After these data are entered, click on the
I SEARCH | button to identify the default meteorological station. If the latitude and longitude
information was entered incorrectly or if no data were provided at all, message boxes will
be displayed that indicate the specific problem that the tool encountered so that you can
supply the needed data.
D. View Selected Meteorological Station (Screen 1A)
The meteorological station selected by the tool will be displayed in the text box. Once
the meteorological station is selected, you are encouraged to click on the VIEW MAP | button to
view the maps showing the 60 meteorological stations to ensure that the selection was made
correctly. For example, if the latitude of a site was entered incorrectly, then the selected
meteorological station would likely not be the most representative station. In this case, the map
will help you identify this error before proceeding with the calculations. Clicking on the | VIEW
MAP | button will bring up a map of the 48 contiguous states (Screen IB, shown here). You may
view six additional maps (regional maps for the northeastern, southeastern, and western areas of
the 48 contiguous states, as well as maps of Hawaii, Alaska, and Puerto Rico) by clicking on the
appropriate button at the bottom of Screen IB. The | CLOSE| button returns you to the METHOD, MET.
STATION, WMU Screen (Screen 1 A).
4-7
-------
IWAIR User's Guide
Section 4.0
| Industrial Waste - [Ib. Maps showing the Met Stations]
File Help
Emission Rates
I
Dispersion Factors
Results
Method, Met. Station, WMU \~
Vastes Managed
WMU Data for CHEMDAT8
120°W
Continental U.S. Western U.S. Northeastern U.S. Southeastern U.S. Alaska Hawaii Puerto Rico
Alaska Hawaii
I close ||
Screen IB. Map of 48 Contiguous States Showing 60 Meteorological Stations
E. Select Emission and Dispersion Option (IWAIR-Generated or User-Specified)
(Screen 1A)
You must select from the IWAIR emission and dispersion data options. Under these
options, you have the flexibility of conducting modeling using IWAIR-generated emission rate
and dispersion factor estimates, user-specified emission and dispersion estimates, or a
combination of IWAIR-generated and user-specified estimates.
The tool uses emission rate and dispersion factor estimates in both the risk and allowable
concentration modes. As seen in Screen 1 A, you must select one of the three options provided
for obtaining emission and dispersion data:
• Use CHEMDAT8
Select | USE CHEMDAT81 to use CHEMDAT8 for calculating the emissions from
your unit regardless of whether you want to calculate or enter dispersion factors.
This allows you to enter a variety of unit-specific information that IWAIR will use
4-8
-------
IWAIR User's Guide Section 4.0
to develop chemical-specific emission rate estimates through the use of EPA's
CHEMDAT8 model. These inputs also provide the information needed to use the
ISCST3 dispersion factors provided with IWAIR; however, you may also enter
your own dispersion factors. You will be allowed to override the IWAIR
emission estimates on subsequent screens. This option corresponds to Pathways 1
and 2 (see Section 3.3 and Figures 4-1 and 4-2).
• Enter Emission Rates
Select | ENTER EMISSION RATES | to enter your own site-specific emission rates (g/m2-s)
on a subsequent screen. Rates may be developed based on monitoring data or
measurements or by conducting modeling with a different emission model. Under
this option, IWAIR can be used to estimate dispersion based on ISCST3 default
dispersion factors. If this option is selected, you will still be allowed to override
the IWAIR dispersion factors on subsequent screens with site-specific dispersion
factors (|J,g/m3 per |j,g/m2-s). Once the | ENTER EMISSION RATES | command button is
selected, a message box will appear that directs you to enter WMU area (m2). If a
waste pile is being modeled, a subsequent box will appear for the height of the
unit to be entered. These WMU data are used by the model to calculate dispersion
estimates. This option corresponds to Pathway 3 (see Section 3.3 and Figure 4-3).
Enter Emission, Dispersion Data.
Select | ENTER EMISSION & DISPERSION DATA| to enter your own emission estimates
(g/m2-s) and dispersion factors (n-g/m3 per |j,g/m2-s). This option corresponds to
Pathway 4 (see Section 3.3 and Figure 4-4).
4-9
-------
IWAIR User's Guide
Section 4.0
B. Select
sorting option
for identifying
chemicals
A. Add/
modify
chemicals
C. Identify
chemicals in
waste
File Help
Results
Method, Met. Station, WMU
Wastes Managed
WMU Data for CHE MDAT8
Identify Chemicals of Concern
To select chemical in management unit, click on chemical in list and click "Add »", or double-click on chemical in list
To remove chemical in management unit, select chemical to remove and click "«Remove"
To add a chemical to the list or to modity properties tor a user-detined chemical, click "Add/Modify Chemicals"
(• Sort by chemical name
T Sort by CAS number
Add/Modify Chemicals
Benzo(a)pyrene [50-32-8]
Bromodichloromethane [75-27-4]
E^^if!5IP!EMlS8Hn^^B
Carbon tetrachloride [56-23-5]
£hlorobenzene [103-90-7]
Chlorodibromomethane [124-48-1]
Chloroform [67-66-3]
Chloroprene [126-99-3]
cis-1,3-Dichloropropylene [10061 -01 -5]
Cresols (total) [1319-77-3]
Cumene [98-82-8]
Cyclohexanol [108-93-0]
Dichlorodifluoromethane [75-71-3]
Epichlorohydrin [106-89-8]
Hhylbenzene [100-41-4]
Ethylene dibromide [106-93-4]
Ethylene glycol [107-21-1]
Ethylene oxide [75-21-8]
Select
chemical t
remove
Chemicals in waste
1,1,1,2-Tetrachloroethane
Acetone
Carbon disulfide
Screen 2A. Wastes Managed
4.2 Wastes Managed (Screen 2A)
To perform a risk calculation, identify the chemical(s) in the waste being managed, and if
you are using CHEMDAT8, enter the concentration (mg/L or mg/kg) of each chemical. You may
also choose to add or modify chemical data from this screen.
A. Add/Modify Chemicals (Screen 2A)
IWAIR includes a list of chemicals from which you can identify waste constituents. As a
convenience to the user, IWAIR includes data on 95 constituents (shown with their CAS number
in Section 1, Table 1-1). However, this list of chemicals may not include all the organic
chemicals in your waste, and the data for these 95 chemicals may not match your site-specific
conditions for some properties. Therefore, IWAIR has the capability to add or modify chemicals.
To add or modify chemical data, click on the | ADD/MODIFY CHEMICALS | button. This will bring up
Screen 2B, ADD/MODIFY CHEMICALS.
4-10
-------
IWAIR User's Guide
Section 4.0
53 Industrial Waste - [2b. Add/Modify Chemicals]
File Help
,,Ja.|x|
AS. Clear entry
Wastes
Enter information for new chemical into form or double-dick chemical from list box on which to base new entry.
A6. Save entry
r Chemical Properties —
Chemical name:
f*
CAS number:
Molecular wt
(g/g-mole):
Density (g/cm3):
{-•
Vapor pressure
(mmHg):
Henry's law constant
Catm-m3/mol-K):
SolubBy (mgjL):
Soil biodegradation
rste(s-1):
Antoine's constants: A:
Health benchmarks:
Cancer slope factor
(mgjkgM)-1:
(enter leading spaces if necessary)
Diffussvity in water
(cm2/s):
Diffusivity in air
(cm2/s):
log(Kow):
K1 (L/g-h):
Kmax (mg VO/g-h):
Reference
concentration (mg/m3):
Chemicals currently in database:
Sort by chemical name
Sort by CAS number
1,1,1,2-Tetrachloroethane [630-20-6]
1,1,1-Trichloroethane [71-55-6]
1,1,2,2-Tetrachloroethane [79-34-5]
1,1,2-Trichloro-1,2,2-trifluoroethane [76-13-1 ]
1,1,2-Trichloroethane [79-00-5]
1,1-Dichloroethylene [75-35-4]
1,2,4-Trichlorobenzene [120-82-1]
1,2-Dibromo-3-chloropropane [96-12-8]
1,2-Dichloroethane [107-06-2]
1,2-Dichloropropane [78-87-5]
1,2-Diphenylhydraiine [122-66-7]
1,2-Epoxybutane [106-88-7]
1,3-Butadiene [106-99-0]
1,4-Dioxane [123-91-1]
Delete User-Defined Chemical
Screen 2B. Add/Modify Chemicals
The ADD/MODIFY CHEMICALS screen will initially appear with no data in any of the fields. You
have four options:
• Add a new chemical. To do this, enter all data, including chemical name and
CAS number, manually.
• Add a new entry for a chemical already in the database To do this, select an
existing entry for the chemical for which you wish to add an entry; if you select a
user-defined entry, IWAIR will ask if you want to create a new entry. Click on
I YES |. If you select an original IWAIR entry, IWAIR will automatically create a
new entry.
• Modify the data in an existing user-defined entry. To do this, select the
chemical to modify; when IWAIR asks if you want to create a new entry, click on
I No |. Original IWAIR entries may not be modified; if you select one, IWAIR will
automatically create a new entry.
• Delete an existing user-defined entry. Select the entry to delete. Original
IWAIR entries may not be deleted.
4-11
-------
IWAIR User's Guide Section 4.0
To ensure the integrity of the original IWAIR data and distinguish user-defined entries,
IWAIR will automatically generate a unique identifier for each chemical entry added to the data
set in the format "User X," where "X" is an entry number and "User" indicates it is a user-
defined entry. This identifier will be appended to the chemical name to uniquely identify each
entry. This identifier will be shown on screens and reports whenever the chemical is identified to
clearly indicate which chemical entry has been used.
Mercury is included in the IWAIR database in both divalent and elemental forms, but
because of code modifications needed for mercury (to reflect differences in its behavior, since it
is not an organic chemical), you may not create additional or modified entries for mercury.
Al. Select Sorting Order for Identifying Chemicals (Screen 2B)
The list of chemicals that is currently available in the database is shown here so that you
can select constituents to modify. This list includes the 95 constituents included with
IWAIR, as well as any you have already added to the IWAIR database. To facilitate the
chemical selection process, IWAIR allows you to sort this list of chemicals alphabetically
by chemical name, or by CAS number. As shown in Screen 2B, select a sort order by
clicking on the button to the left of the sorting option of choice.
A2. Select a Chemical to Modify (Screen 2B)
If you wish to add a new entry for an existing chemical or modify an existing user-defined
entry, double-click on the chemical name in the list of chemicals. This will display the
data for that chemical on the ADD/MODIFY CHEMICALS screen. If you select one of the 95
original IWAIR chemicals, a new entry will be generated automatically with a new,
unique identifier. If you select a user-defined entry, IWAIR will ask if you want to create
a new entry. Click on | YES | to create a new entry (you will be able to modify the data) or
I No | to edit the existing entry.
A3. Enter or View Chemical Name and CAS Number (Screen 2B)
If you selected a chemical to modify or to update with a new entry, the chemical name
and CAS number will be displayed. These may not be edited, to preserve the integrity of
the unique chemical identifiers. If you are adding a new chemical and therefore entering
all data manually, you will need to enter an appropriate chemical name and CAS number
in these text boxes. Do not include a "User X" designation in your chemical
name—IWAIR will append that automatically. Chemical names may not contain
apostrophes (') or quotation marks ("). CAS numbers that are shorter than the maximum
length should be prefaced with leading spaces, not zeros.
A4. Enter Chemical Properties Data (Screen 2B)
Enter values for all chemical properties shown on the screen. Use the mouse to click in
each text box, or use the | TAB | key to move between the boxes. Except for health
benchmarks, you may only enter numeric values (although you may enter numeric values
4-12
-------
IWAIR User's Guide Section 4.0
in scientific notation). For health benchmarks, "NA" may also be entered. Be sure to
enter values in the units shown. Additional guidance on obtaining values for these
parameters is available in Appendix B, Section B.2.2.3.
You may enter user-defined health benchmarks both here, in a user-defined chemical
record, and on the RESULTS screen. On the RESULTS screen, you can enter them directly into
an IWAIR chemical record without overwriting the original IWAIR value. If you are
entering a new or modified chemical entry, you should enter any user-defined health
benchmarks here. However, you need not create a new chemical entry here just to change
the benchmark of an IWAIR chemical; you can enter the user-defined health benchmark
on the RESULTS screen.
AS. Clear Entry (Screen 2B)
To clear an unwanted entry from the ADD/MODIFY CHEMICALS screen without saving, click on
the | CLEAR | button. You will be asked to confirm that you want to clear the data.
A6. Save Entry (Screen 2B)
Once all data have been entered, you can save by clicking on the | SAVE| button. IWAIR
does some limited range checking to ensure values are within physically possible ranges;
if an entry is not in the acceptable range, IWAIR will display an error message with the
accepted range. These ranges are intended to eliminate only impossible entries (e.g.,
negative values for many properties) or values that will cause the model to fail. The
actual range for most of the chemical properties is likely smaller than the accepted range.
Once all data values have been validated and the entry added to the database, the form
will be cleared.
A 7. Delete a Chemical (Screen 2B)
You may delete a user-defined chemical entry on the ADD/MODIFY CHEMICALS screen by
selecting the chemical from the list of chemical entries and clicking on the | DELETE USER-
DEFINED CHEMICAL | button. It is not necessary to double-click on the chemical to bring up its
data before deleting; a single click to select the entry in the list is sufficient. If you have
selected an original IWAIR chemical entry, an error message will appear indicating that
the entry cannot be deleted. If you have selected a user-defined entry, a message will
appear to confirm that you want to delete the entry. If you select I YES |, the entry will be
deleted from the database and you will be returned to the ADD/MODIFY CHEMICALS screen. The
list of chemicals on this screen will be updated to reflect the removal of the entry. If you
select I No |, you will be returned to the screen, and the chemical will not be deleted.
Note that the deletion of a chemical entry used in a saved analysis will lead to the failure
of the saved analysis to reload.
4-13
-------
IWAIR User's Guide Section 4.0
A8. Return to Wastes Managed Screen (Screen 2B)
Once you have completed all desired data additions, modifications, and deletions, click
the | RETURN | button to return to the WASTES MANAGED screen. If you have unsaved data,
IWAIR will warn you and ask if you want to proceed. If you select I YES |, the unsaved
data will be lost. If you select I No |, you will be returned to the ADD/MODIFY CHEMICALS
screen, where you can save your data by selecting | SAVE |.
The list of available chemicals in the WASTES MANAGED screen will be updated to include any
new entries and to omit any deleted entries.
B. Select Sorting Option for Identifying Chemicals (Screen 2A)
Once you have returned to the WASTES MANAGED screen, you can identify waste constituents
from the list of chemicals included in IWAIR. This list includes the 95 constituents included
with IWAIR, as well as any you add to the IWAIR database using the ADD/MODIFY CHEMICALS feature.
The 95 constituents included with IWAIR are shown with their CAS number in Section 1, Table
1-1. To facilitate the chemical identification process, IWAIR allows you to sort this list of
chemicals alphabetically by chemical name, or by CAS number. As shown in Screen 2A, select a
sort order by clicking on the button to the left of the desired sorting option.
C. Identify Chemicals in Waste (Screen 2A)
Identify up to six chemicals in a waste for modeling with IWAIR. Identify a chemical by
clicking on the chemical name or CAS number and clicking on the | ADD» | command button. To
remove a waste constituent from consideration, select the check box located to the left of the
chemical name and click the | «REMOVE| command button. User-defined entries are identified in
this list by the modifier "User X" appended to the chemical name, where "X" is a unique
number.
You may choose to simultaneously model the same chemical using multiple entries from
the chemical database. You may want to do this to compare results based on changes you have
made in chemical properties. However, you should note that the resulting total risk (across all
chemicals modeled) presented on the RESULTS screen will reflect double-counting for any
chemicals duplicated and will, therefore, not be an accurate estimate of total risk. Chemical-
specific risk results will be accurate.
D. View Selected Chemicals (Screen 2A)
The chemicals you identified for consideration are displayed in text boxes shown on
Screen 2A. You can remove waste constituents from consideration by selecting the check box to
the left of the chemical and clicking the | «REMOVE| command button.
4-14
-------
IWAIR User's Guide Section 4.0
E. Enter Waste Concentrations (Screen 2A)
If you are using CHEMDAT8, enter a chemical-specific waste concentration for each
chemical identified. This is not necessary if you are not using CHEMDAT8. The concentration
should be expressed as mg/L for wastewaters and mg/kg for solid wastes.
The total concentration (the sum of all concentrations entered) may not exceed the
physical limit of 1,000,000 mg/L or mg/kg; if this occurs, an error message will be displayed and
the program will not proceed until the total concentration is less than or equal to 1,000,000 mg/L
or mg/kg. In addition, if the total concentration exceeds 10 percent (100,000 mg/L or mg/kg), a
message will be displayed advising you to consider characterizing the waste as an organic waste
in the WASTE MANAGEMENT UNITS screen (Screen 3 A, 3B, 3C, or 3D). The distinction between aqueous
and organic wastes is discussed briefly in Section 4.3C and in more detail in Appendix B,
Sections B.3.1.4, B.3.2.4, B.3.3.4, and B.3.4.4.
Chemicals with entered waste concentrations that lead to concentrations in the unit in
excess of the solubility limit in the IWAIR database (for surface impoundments) or the soil
saturation limit calculated by IWAIR (for other unit types) for that chemical will be modeled
somewhat differently by CHEMDAT8. Typically, chemicals above saturation or solubility limits
in the unit will come out of solution, and if this is occurring, the waste would be best modeled as
an organic-phase waste. However, these limits can be somewhat site-specific; therefore, IWAIR
does not prevent you from entering waste concentrations in excess of these limits, nor does it
require you to model wastes with concentrations in excess of these limits as organic-phase
wastes. Instead, IWAIR assumes that the chemical remains in solution, either because of waste
matrix effects in your unit or because the actual solubility or soil saturation limit in your unit is
higher than that specified in the database or calculated by IWAIR because of site-specific
conditions. However, even though IWAIR continues to model such wastes as aqueous-phase
wastes (unless you select organic-phase), it uses a different partition coefficient that more
appropriately models this situation. IWAIR will notify you that this was done after emissions are
calculated (because determining when this is the case depends on data entered after the WASTES
MANAGED screen). In addition, printed reports will document the use of the alternative emissions
modeling approach.
4.3 Enter WMU Data for Using CHEMDAT8 Emission Rates
If you elected to use CHEMDAT8 emission rates in the risk calculations (i.e., selected the
USE CHEMDAT81 command button shown previously on Screen 1 A), you will need to enter WMU
data as specified in this section. If you did not elect to use CHEMDAT8 emission rates, then you
should proceed to Section 4.4, Emission Rates. If you elected to enter emission rates and use
ISCST3 dispersion factors, you will be asked to enter the WMU area (and height, if a waste pile)
for ISCST3 before proceeding to the emissions screen.
This section provides guidance on providing input data needed to develop CHEMDAT8
emission estimates for the four unit types addressed by IWAIR.
4-15
-------
IWAIR User's Guide Section 4.0
Surface Impoundments. The major source of volatile emissions associated with surface
impoundments is the uncovered liquid surface exposed to the air (U.S. EPA, 1991).
Aeration and/or agitation are applied to aid in treatment of the waste, and emissions tend
to increase with an increase in surface turbulence because of enhanced transfer of liquid-
phase contaminants to the air (U.S. EPA, 1991). Parameters to which emissions are most
sensitive include surface area, unit depth, waste concentration, retention time, wind speed
for quiescent systems, and biodegradation. Retention time is not an explicit input, but is
a function of impoundment volume and flow.
Land Application Units. Waste can be tilled or sprayed directly onto the soil and
subsequently mixed with the soil by discing or tilling. Waste in a land application unit is
a mixture of sludge and soil. IWAIR allows the modeling of tilled land application units.
If your unit uses spray application, another model may be more appropriate. Air
emissions from land treatment units are dependent on the chemical/physical properties of
the organic constituents, such as vapor pressure, diffusivity, and biodegradation rate.
Operating and field parameters affect the emission rate, although their impact is not as
great as that of the constituent properties.
Active Landfill. IWAIR allows the modeling of emissions released from the surface of
an active (i.e., receiving wastes) landfill. The landfill model is sensitive to the air
porosity of the solid waste, the liquid loading in the solid waste, the waste depth
(assumed to be the same as the unit depth), the constituent concentration in the waste, and
the volatility of the constituent (U.S. EPA, 1991).
Waste Piles. The waste pile emission model is sensitive to the air porosity of the solid
waste, the liquid loading in the solid waste, the waste pile height, the constituent
concentration in the waste, and the volatility of the constituent (U.S. EPA, 1991).
Screens 3A, 3B, 3C, and 3D, respectively, identify the CHEMDAT8 input requirements
for surface impoundments, land application units, landfills, and waste piles. Guidance for
completing each screen is provided below. For some of the required inputs, default values are
provided in the screen text boxes, as well as to the right of the text boxes. These default values
were selected to represent average or typical operating conditions. If appropriate, the defaults
can be applied in the absence of site-specific data; however, you always have the option of
overriding any defaults. The basis for these default values is provided in the IWAIR Technical
Background Document.
4-16
-------
IWAIR User's Guide
Section 4.0
File Help
Emission Rates
Method Met. Station, WMU
I
1
Jispersion Factors j
Wastes Managed | WMU Data for CHEMDATB j
Surface Impoundment Information
Wind speed (m/s)
Temperature (C)
,-SI Dimensions , Loading Informatior
Biodegradation (*" On P
Operating life (yr)
Depth of unit Cm)
Area of unit (m2)
Annual flow of waste
(mS/yr)
No aeration (quiescent)
Diffused air aeration
Mechanical aeration
Both (diffused air & mechanical)
Fraction of surface area agitated
Submerged air flow (m3/s)
[3.473 |
|15.45 |
3ff
10000
2500
r
r
r
(?
C
C
n
n
Type of waste: Aqueous (• Organic C
Default
Molecular weight of waste (g/mol)
Density of waste (g/cm3)
Active biomass (g/L) |n-ns | 0.05
Total suspended solids in influent (grt_) |o.2 | o.2
Total organics into WMU (mg/L) [200 "| 200
Total biorate (mg/g biomass-h) |19 1 9
Default
Oxygen transfer rate (Ib 02/h-lip) |3 | 3
Number of aerators
Total power (hp)
Power efficiency (fraction) |o.83 | 0.83
Impeller diameter (cm) [61 61
Impeller speed (radfc) |l30 130
Done
E. Enter waste
data
D. Enter
mechanical
aeration
information
Screen 3A. WMU Data for CHEMDAT8: Surface Impoundment
A. View met
data for site
Industrial Waste - [3b. Land Application Unit]
File Help
Emission Rates |
Method, Met Station, WMU ]
Dispersion Factors
Wastes Managed
y Results
] WMU Data for CHEMDATB
]
—Meteorological Station Parameters
Wind speed (m/s) b .473
Temperature (C)
—Waste/Soil Mixture Porosity Information
Default
Total porosity (volume ITT: i 0 61
fraction) L I
Air porosity (volume [Q^ I g ^
fraction) L— 1
Land Application Unit Information
Biodegradation (T gn p gff
Opersiting life (yr)
Tilling depth of unit (m)
Area of unit (m2)
Annual waste quantity (Mg/yr)
Number of applications per year
Waste bulk density (g/cm3)
20
1
500
100
^
•
Default
1.3
-Waste Characteristics Information (Only for Risk Calculation)
Aqueous (? Organic C
Molecular weight of waste (g/g-mole)
Screen 3B. WMU Data for CHEMDAT8: Land Application Unit
4-17
-------
IWAIR User's Guide
Section 4.0
File Help
Dispersion Factors
Results
Method Met Station, WUU
Wastes Managed
WMU Data for CHEMDAT8
l-Meteorological Station Parameters-
I speed (m/s)
Temperature (C)
3.473
115.45
—Waste Porosity Information—
Default
Total porosity (volume fraction) In.5 0.5
Air porosity (volume traction)
Landfill Information
— Landfill Dimensions and Loading information
Biodegradation C On (• Off
Operating life (yr) |20
Total area of landfill (m2) |SOO
Total depth of landfill (m) |2
Total number of cells in landfill 1 2
Annual quantity of waste disposed in Rrjoo
landfill (Mg/yr) I
Bulk density of waste (g/cm3) [1 .2
Default
4
1.2
Waste Characteristics Information (Only for Risk Calculation)'
Aqueous (* Organic f
Molecular weight of waste (g/g-mole)
Screen 3C. WMU Data for CHEMDAT8: Landfill
Industrial Waste - [3d. Waste Pile]
File Help
Emission Rates ]
M etti o d, M et. Stati o n, WM U ]
Dispersion Factors
Wastes Managed
1 Results
1 WMU Data for CHEMDATB 1
—Meteorological Station Parameters
Wind speed (m/s) |3'473
Temperature (C) |15.45
Waste Pile Information
Waste Pile Dimensions and Loading Information
Biodegradation P On (* Off
Operating life (yr)
Height of waste pile unit (m)
Area of unit (m2)
|20
F
|300
Average quantity of waste in waste pile (Mg/yr) H 00
Bulk density of waste (g/cm3) h 4
Default
F. Enter
waste
porosity
information
Default
Total porosity (volume i 1
fraction) |°-5 | °-5
Air porosity (volume fraction) IQ 25 1 0.25
Aqueous (• Organic P
*
Molecular weight of waste (g/g-mole)
Done
Screen 3D. WMU Data for CHEMDAT8: Waste Pile
4-18
-------
IWAIR User's Guide Section 4.0
A. View Meteorological Data for Site (Screens 3A, 3B, 3C, and 3D)
Both wind speed and temperature can affect the volatilization rate of a chemical.
Average wind speed and temperature are used as input to the CHEMDAT8 model. Average
annual wind speed is used to select the most appropriate empirical emission correlation equation
in CHEMDAT8; there are several of these correlations, and each one applies to a specific range
of wind speeds and unit sizes. Average annual temperature is used to adjust Henry's law
constant and vapor pressure values (temperature-dependent chemical properties) from a standard
temperature to the ambient temperature at the unit. Drawing from the meteorological data stored
in IWAIR, the program will display the average annual temperature and wind speed available for
the representative meteorological station that was determined for the site in Screen 1 A. You can
enter average wind speed and temperature for your site if the default values are significantly
different.2
B. Enter Unit Design and Operating Data
For all unit types, you may select whether or not biodegradation occurs in your unit.
Select the | ON | option to turn biodegradation on and the | OFF | option to turn it off. The default
setting varies by unit type. See Appendix B, Sections B.3.1.2, B.3.2.3, B.3.3.3, and B.3.4.3, for
further details about the implications of turning biodegradation on or off and the appropriateness
of difference choices for different unit types.
Enter Surface Impoundment Design Data (Screen 3A)
Enter the unit dimensions and loading information in the text boxes shown in Screen 3 A.
The data include the operating life at the unit (yrs), the depth of the unit (m), the area of
the unit (m2), and the annual flow of the waste (m3/yr).
Enter Land Application Unit Design and Operating Information (Screen 3B)
Enter the unit dimensions and loading information in the text boxes shown in Screen 3B.
The data include the operating life of the unit (yrs), tilling depth of the unit (m), area of
the unit (m2), annual waste quantity (Mg/yr), number of applications per year, and waste
bulk density (g/cm3).
Enter Landfill Design and Operating Information (Screen 3C)
Enter the unit dimensions and loading information in the text boxes in Screen 3C. The
model assumes that the landfill is divided into cells, with only one cell active at a time.
Emissions are modeled from the active cell. The data to be entered include the operating
life of the unit (yrs), total area of the unit (m2), depth of the unit (m), number of cells in
your unit, annual quantity of wastes disposed in the unit (Mg/yr), and bulk density of
waste (g/cm3).
These inputs are not used in the dispersion modeling, which uses hourly data, not annual averages.
Therefore, changes to these inputs will not affect the dispersion factors.
4-19
-------
IWAIR User's Guide Section 4.0
Enter Waste Pile Design and Operating Information (Screen 3D)
Enter the unit dimensions and loading information in the text boxes in Screen 3D. The
data include the operating life of the unit (yrs), the height of the pile (m), area of the unit
(m2), annual quantity of waste in the pile (Mg/yr), and bulk density of the waste (g/cm3).
C. For Aerated Surface Impoundments Only — Enter Aeration Data (Screen 3A)
IWAIR models both quiescent (nonaerated) and aerated impoundments. Aeration or
agitation of a liquid waste in an impoundment enhances transfer air (oxygen) to the liquid to
improve mixing or to increase biodegradation (U.S. EPA, 1991). Aeration is achieved through
the use of mechanical mixers, such as impellers (i.e., mechanically aerated), or by sparging air,
which bubbles up from the bottom of the unit (i.e., diffused air aerated). First, select the aeration
option that best describes your unit by clicking the appropriate option button. If you selected one
of the aerated options, provide information to characterize the aeration in your unit. For all
aeration options, you will need to enter the fraction of the surface area agitated (unitless). If you
selected an option including diffused air aeration (diffused air only or both diffused air and
mechanical aeration), you will also need to enter the total submerged air flow (m3/s) of all
diffusers in the impoundment.
If you choose to model an aerated impoundment, you will not have the option of
modeling an organic-phase waste; IWAIR cannot model an organic-phase waste in an aerated
impoundment because of limitations in CHEMDAT8.
D. For Mechanically Aerated Surface Impoundments Only - Enter Mechanical Aeration
Information (Screen 3A)
If a surface impoundment is mechanically aerated, you will need to provide additional
operating parameter information. These data include oxygen transfer rate (Ib O2/hr-hp), number
of aerators, total power (hp), power efficiency (fraction), impeller diameter (cm), and impeller
speed (rad/s).
E. Enter Waste Characteristics Data (Screens 3A, 3B, 3C, and 3D)
For Surface Impoundments Only - Enter Waste Characteristics Data (Screens 3A)
For nonaerated impoundments, specify whether the waste being modeled is an aqueous-
or organic-phase waste. IWAIR cannot model organic-phase wastes for aerated
impoundments; therefore, if you selected an aeration option other than nonaerated, the
organic option will not be enabled. Appendix B, Section B.3.1.4 contains detailed
guidance on determining whether your waste is aqueous or organic, including definitions
of those terms. Briefly, in making the determination of whether a waste is aqueous or
organic, you should examine the fraction of the waste that is organic. Consider the
following guidance in making this determination.
4-20
-------
IWAIR User's Guide Section 4.0
Organic: If the total concentration of all organics in the waste is greater than 10
percent, then the waste is probably most appropriately modeled as organic.
IWAIR will suggest this if the combined concentration of all chemicals
entered is greater than 100,000 or mg/L, or 10 percent, but it will not
automatically select the organic option; IWAIR always defaults to
aqueous, and you must explicitly select the organic option if you determine
that it is more appropriate.
Aqueous: If the total concentration of all organics in the waste is less than 10
percent, then the waste is probably more appropriately modeled as
aqueous. The default in IWAIR is always aqueous.
Based on your selection of aqueous or organic, IWAIR will apply either the aqueous or
the organic waste equilibrium partitioning algorithm. For organic wastes, the model uses
Raoult's law, and the liquid-to-air partition coefficient becomes proportional to the
contaminant's partial vapor pressure. For aqueous wastes, which are assumed to partition
predominantly to water (e.g., rain and water in the soil), the model uses Henry's law and
the liquid-to-air partition coefficient becomes proportional to the contaminant's Henry's
law coefficient.3 This is discussed in greater detail in Appendix B, Section B.3.1.4.
If you choose to model an organic-phase waste, you will also need to enter the waste
density (g/cm3) and the average molecular weight of the waste (g/mol). Appendix B,
Section B.3.1.4, provides details on how to estimate these parameters.
Additional waste characteristics information to be entered for surface impoundments
includes active biomass (g/L), total suspended solids into WMU (mg/L), total organics
into WMU (mg/L), and total biorate (mg/g biomass-hr). These parameters are discussed
in more detail in Appendix B.
Land Application Units, Landfills, and Waste Piles Only -Enter Waste
Characteristics Data (Screens 3B, 3C, and 3D)
Specify whether the waste being modeled is an aqueous- or organic-phase waste.
Appendix B, Sections B.3.2.4, B.3.3.4, and B.3.4.4, contain detailed guidance on
determining whether your waste is aqueous or organic, including definitions of those
terms. Briefly, in making the determination of whether a waste is aqueous or organic,
you should examine the fraction of the waste that is organic. Consider the following
guidance in making this determination.
Organic: If the total concentration of all organics in the waste is greater than 10
percent, then the waste is probably most appropriately modeled as organic.
IWAIR will suggest this if the combined concentration of all chemicals
3 This assumes the chemical concentration in the impoundment is at or below the chemical's solubility limit.
If it is above the solubility limit, IWAIR uses a hybrid of the aqueous-phase and organic-phase modeling approaches.
See Appendix B, Section B.3.1.4.
4^21
-------
IWAIR User's Guide Section 4.0
entered is greater than 100,000 mg/kg, or 10 percent, but it will not
automatically select the organic option; IWAIR always defaults to
aqueous, and you must explicitly select the organic option if you determine
that it is more appropriate.
Aqueous: If the total concentration of all organics in the waste is less than 10
percent, then the waste is probably more appropriately modeled as
aqueous. The default in IWAIR is always aqueous.
Based on your selection of aqueous or organic, IWAIR will apply either the aqueous or
the organic waste equilibrium partitioning algorithm. For organic wastes, the model uses
Raoult's law and the liquid-to-air partition coefficient becomes proportional to the
contaminant's partial vapor pressure. For aqueous wastes, which are assumed to partition
predominantly to water (e.g., rain and water in the soil), the model uses Henry's law, and
the liquid-to-air partition coefficient becomes proportional to the contaminant's Henry's
law coefficient.4 This is discussed in greater detail in Appendix B, Sections B.3.2.4,
B.3.3.4, and B.3.4.4.
If you choose to model an organic-phase waste, you will also need to enter the average
molecular weight of the waste (g/mol). Appendix B, Sections B.3.2.4, B.3.3.4, and
B.3.4.4, provide details on how to estimate this parameter.
F. For Land Application Units, Landfills, and Waste Mies Only — Enter Waste Porosity
Information (Screens 3B, 3C, and 3D)
Waste (or soil/waste mixture for land application units) porosity information required as
input includes total porosity (unitless) and air porosity (unitless). Total porosity includes air
porosity and the space occupied by oil and water within waste. Total porosity (et), also
sometimes called saturated water content, can be calculated from the bulk density (BD) of the
waste and particle density (ps) as follows:
. BD
et = * - —
where BD and ps are expressed in the same units.
In the absence of site-specific data, IWAIR identifies default values of 0.5 and 0.25,
respectively, for total porosity and air porosity. Air porosity cannot exceed total porosity.
Done. Once you provide the required WMU inputs, click the |DONE| button to enable the
EMISSION RATES tab and open the EMISSION RATES screen. Proceed to Section 4.4, Emission Rates.
4 This assumes the chemical concentration in the unit is at or below the chemical's solubility limit. If it is
above the solubility limit, IWAIR uses a hybrid of the aqueous-phase and organic-phase modeling approaches. See
Appendix B, Sections B.3.2.4, 3.3.4, and B.3.4.4.
4^22
-------
IWAIR User's Guide
Section 4.0
IWAIR must calculate emission rates before displaying the EMISSION RATES screen. This is usually
very quick, but if your computer is slow, or if you are modeling a land application unit with a
large number of total applications (i.e., number of applications per year times operating life),
there can be a noticeable delay before the EMISSION RATES screen is displayed. This is normal, but
should typically not exceed 1 minute on a fast machine or 5 minutes on a slow machine.
4.4 Emission Rates
Guidance for using CHEMDAT8 emission rates or entering your own emission rates is
provided in this section. View and confirm the CHEMDAT8 emission rates as directed in
Section 4.4.1. If you did not elect to use CHEMDAT8 (i.e., if you selected the I ENTER EMISSION
RATES] or | ENTER EMISSION ft DISPERSION DATA] command buttons shown previously on Screen 1A),
proceed to Section 4.4.2, User-Specified Emission Rates.
Please note that all calculated and entered values on the EMISSION RATES screen will be lost if
you return to a previous screen and make changes. This includes both calculated and entered
override emission rate values.
Industrial Waste - [4a. Emission Rates For Wastes From WMU]
File Help
Method, Met. Station, WMU
Wastes Managed
WMU Data for CHEMDAT8
Emission Rates
Dispersion Factors
Results
Chemical Emissions Estimated Using CHEMDAT8
(Emission of chemical = concentration of waste x emission rate)
Chemical emissions
Aqueous Organic Override
Chemicals selected (£fm2/s)
For surface impoundments:
Effluent cone.
(mgJL)
Fraction
adsorbed
1,1,1,2-Tetrachloroethane
Acetone
Carbon diiulficle
Source and Justification for User Override Values
justification
Done
Screen 4A. CHEMDAT8: Emission Rates
4-23
-------
IWAIR User's Guide Section 4.0
4.4.1 Using CHEMDAT8 Emission Rates (Screen 4A)
A. View CHEMDAT8 Emission Rates or Enter User-Specified Emissions (Screen 4A)
Screen 4A shows the calculated CHEMDAT8 emission rates. For surface
impoundments, this screen also shows the calculated effluent concentrations and fraction
adsorbed for each chemical. With the exception of waste managed in aerated surface
impoundments (assumed to be aqueous because of model limitations), emission rates will be
displayed under the AQUEOUS or ORGANIC column headings depending on how you characterized
your waste on the WMU DATA FOR CHEMDAT8 screens (Screens 3 A, 3B, 3C, or 3D). If you wish to
override the displayed rates, enter alternate rates (g/m2-s) in the text boxes located under the
OVERRIDE heading.
For surface impoundments, landfills, and waste piles, emissions are modeled at
equilibrium and are assumed to reflect a long-term average emission rate, which is shown on this
screen. In contrast, land application units are not assumed to be at equilibrium; rather, emissions
are calculated for each year of the specified operating life plus 30 years postclosure. The
emission rates shown on this screen are the maximum single-year emission rates for each
chemical (which may not reflect the same year for all chemicals). This emission rate is used
directly to calculate the air concentration used for calculating noncarcinogenic risk. However,
for carcinogenic risk, the maximum 7- or 30-year average emission rate (7-year for a worker and
30-year for a resident, corresponding to the default exposure durations for each receptor type) is
used to calculate air concentration and risk. If you enter user-override emission rates for any unit
type, they should reflect a long-term average emission rate. Override emission rates are used as
entered in all risk calculations, including both carcinogenic and noncarcinogenic calculations for
land application units.
B. Enter Source and Justification for User-Specified Emission Rates (Screen 4A)
If alternative emission rates are entered, IWAIR will prompt you to identify the source
and justification for these data. This documentation should be entered in the text box displayed
on the screen. It is important to provide this documentation as a reference that will allow you or
another user to view and understand saved files at a later date. This information is also printed in
reports. Confirm the emission rates to be used in the calculations by clicking the |DONE| button.
The program will then automatically enable the DISPERSION FACTORS tab and open the DISPERSION
FACTORS screen. Proceed to Section 4.5, Dispersion Factors.
4-24
-------
IWAIR User's Guide
Section 4.0
Industrial Waste - [4b. User Override Emission Rates]
File Help
Method, Met. Station, WMU
Wastes Managed
WMU Data for CHEMDAT8
Emission Rates
Results
User Override Chemical Emissions
(Emission of chemical = concentration of waste x emission rate)
User override emissions
Chemicals
1,1,1,2-Tetrachloroethane
Acetone
arbon disuliide
1e-6
|2e-6
Ee^T
Source and Justification for User Override Values
justification
Done
Screen 4B. User-Specified Emission Rates
4.4.2 User-Specified Emission Rates (Screen 4B)
A. Enter User-Specified Emissions (Screen 4B)
Enter site-specific emission rates (g/m2-s) in the text box under USER OVERRIDE EMISSIONS. If
you have measured or calculated emission rates in g/s for your entire unit, you will need to divide
that emission rate by the total area of your unit (in m2) to obtain area-normalized emission rates
in g/m2-s. These emission rates should reflect long-term average emissions, not a short-term
peak.
B. Enter Source and Justification for User-Specified Emission Rates (Screen 4B)
The program will prompt you to provide justification for user-specified emission rates
and documentation of the estimation method applied. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
Done. Once you have entered the emission data and source/justification, click the | DONE|
button to enable the DISPERSION FACTORS tab and open the DISPERSION FACTORS screen. Proceed to
Section 4.5, Dispersion Factors.
4-25
-------
IWAIR User's Guide
Section 4.0
4.5 Dispersion Factors
Dispersion modeling outputs are used to estimate air concentrations to which the various
human receptors are exposed. Guidance for using the ISCST3 default dispersion factors or
entering your own site-specific dispersion factors is provided in Sections 4.5.1 and 4.5.2,
respectively. If you elected to use ISCST3 dispersion factors provided in IWAIR (i.e., selected
the | USE CHEMDAT81 or | ENTER EMISSION RATES | command buttons shown previously on Screen 1 A),
you will need to follow the guidance provided in Section 4.5.1. If you did not elect to use the
default dispersion factors, you should proceed to Section 4.5.2, User-Specified Dispersion
Factors.
Please note that all calculated and entered dispersion factors values on the DISPERSION
FACTORS screen will be lost if you return to a previous screen and make changes. This does not
include receptor locations and types but does include calculated and entered override dispersion
factor values.
R3 Industrial Waste - [5. Dispersion Factors]
File Help
T n o v c 111 d c d c ] .:t L 111 r 11: n e r: i o n i a c i o r:, c n i c r v .:t I LI c: i n i o " M:: c i o v u 111 c I u" c o I L 11 n n
Dispersion factors for location and unit
size [(ugjtnS per (ug/m2-s)]
C. View
IWAIR
dispersion
factors or
enter user-
specified
dispersion
factors
D. Enter
source and
justification
for user-
specified
dispersion
factors
Screen 5A. Using ISCST3 Default Dispersion Factors
4.5.1 Using ISCST3 Default Dispersion Factors (Screen 5A)
In Screen 5A, you will provide receptor information (i.e., receptor type and distance to
the receptor) and click the | CALCULATE | button; IWAIR will develop site-specific dispersion factors
based on default dispersion data. If you wish to override the IWAIR-developed dispersion
factors, enter alternate site-specific unitized dispersion factors. If you enter alternative dispersion
4-26
-------
IWAIR User's Guide Section 4.0
factors, you should document the source and the justification for these data in the text box on the
screen.
A. Select Receptor Type and Distance (Screen 5A)
Enter information concerning the receptors of concern (i.e., potentially exposed
individuals). You can specify up to five receptors, including the distance to receptor and the
receptor type. You can specify two receptor types, resident or worker, at six distances (25, 50,
75, 150, 500, and 1,000 meters) from the edge of the WMU. You can delete the last receptor
entered by deleting both the distance to receptor and receptor type entries.
Distance to Receptor - For each receptor of concern, determine the distance from the
edge of the unit to the receptor. Based on this distance, select from the six default distances (25,
50, 75, 150, 500, and 1,000 meters) the one that best approximates the location of your receptor,
using the drop-down box positioned under the DISTANCE TO RECEPTOR column heading. Note that
selecting a distance smaller than the actual distance to receptors near your unit will overestimate
risk, and selecting a distance larger than the actual distance will underestimate risk. These
distances correspond to the distances for which air dispersion modeling was conducted to
develop the IWAIR default dispersion factors. The IWAIR Technical Background Document
discusses the analysis that was conducted in determining the appropriateness of these default
distances.
Receptor Type - Two different types of exposed individuals, worker and resident, can be
modeled with IWAIR. The dispersion factors do not vary with receptor type; however, receptor
type is chosen here for convenience. The difference between these two receptor types lies in the
exposure factors, such as body weight and inhalation rate, used to calculate risk for carcinogens.
There is no difference between them for noncarcinogens, because calculation of noncarcinogenic
risk does not depend on exposure factors. The IWAIR Technical Background Document
describes the exposure factors used for residents and workers. The assumptions for workers
reflect a full-time, outdoor worker. The exposure duration for workers is the smaller of 7.2 years
or the operating life of the unit. The assumptions for residents reflect males and females from
birth through age 30; it is important to consider childhood exposures because children typically
have higher intake rates per kilogram of body weight than adults. The actual exposure duration
used for residents is the smaller of 30 years or the operating life of the unit that you entered.5 For
exposure durations less than 30 years, exposure starts at birth and continues for the length of the
exposure duration, using the appropriate age-specific exposure factors. Use the drop-down box
positioned under the RECEPTOR TYPE column heading to select either WORKER or RESIDENT.
B. Direct IWAIR to Estimate Dispersion Factors (Screen 5A)
After the requested receptor information is provided, click on the | CALCULATE! button to
direct the program to determine an appropriate dispersion factor based on the IWAIR default
5 An exception to this is that the exposure duration for land application units is 7.2 years for workers and 30
years for residents regardless of the operating life entered for the unit. This allows IWAIR to account for postclosure
exposures, which are assumed to occur with land application units but not with other units.
4^27
-------
IWAIR User's Guide Section 4.0
dispersion data. The resulting dispersion factor will be displayed for each receptor of concern. A
discussion of the development of IWAIR default dispersion data and the methodology used by
the program in selecting an appropriate dispersion factor for each WMU/receptor combination is
provided in Section 3.3. A more detailed discussion of the air dispersion modeling effort is
provided in the IWAIR Technical Background Document.
For waste piles, IWAIR uses a two-dimensional nonlinear spline to interpolate dispersion
factors for areas and heights different from those included in the dispersion factor database. This
technique is more accurate than a two-dimensional linear interpolation and is less likely to
underestimate the actual dispersion factor. However, on rare occasions, the spline may produce
results inconsistent with the data points nearest the actual area and height. If this occurs, IWAIR
shifts to the linear interpolation technique, which generally produces somewhat lower dispersion
factors. If this occurs, you will see a message to that effect. The interpolation techniques used
for dispersion factors are discussed in greater detail in the IWAIR Technical Background
Document.
C. View IWAIR Dispersion Factors or Enter User-Specified Dispersion Factors
(Screen 5A)
You may override the program-calculated dispersion factors by entering alternative
dispersion data in the text box located under the USER OVERRIDE column (see Screen 5A).
D. Enter Source and Justification for User-Specified Dispersion Factors (Screen 5A)
If you choose to provide alternative dispersion factors, document the source and the
justification for these data in the text box that will appear. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date. This information also appears on printed reports.
Done. Once the program has developed dispersion factors, click the | DONE | button to
open the RESULTS tab. Proceed to Section 4.6, Results.
4-28
-------
IWAIR User's Guide
Section 4.0
Industrial Waste - [5. Dispersion Factors]
File Help
To override default dispersion factors, enter values into "User override" column
Wastes Managed
WMU Data for CHEMDATB
Dispersion Factors
Results
Receptor Distance, Type, and Dispersion Factor
Dispersion factors for location and unit
size [(Ud/m3 per (ug/m2-s)]
Source and Justification for User Override Values
Done
C. Enter
source and
justification
for user-
specified
dispersion
factors
Screen 5B. User-Specified Dispersion Factors
4.5.2 User-Specified Dispersion Factors (Screen 5B)
A. Select Receptor Type and Distance (Screen SB)
Enter information concerning the receptors of concern (i.e., potentially exposed
individuals). You can specify up to five receptors. The receptor information includes the
distance to receptor and the receptor type. You can specify two receptor types (residents or
workers) at six distances (25, 50, 75, 150, 500, and 1,000 meters) from the edge of the WMU.
You can delete the last receptor by deleting both the distance to receptor type and receptor type
entries.
Distance to Receptor - For each receptor of concern, determine the distance from the
edge of the unit to the receptor. Based on this distance, select from the six default distances (25,
50, 75, 150, 500, and 1,000 meters) the one that best approximates the location of your receptor,
using the drop-down box positioned under the DISTANCE TO RECEPTOR column heading. These values
are only for your reference and are not used in calculations, since you are entering your own
dispersion factors.
Receptor Type - Two different types of exposed individuals, WORKER and RESIDENT, can be
modeled with IWAIR. The dispersion factors do not vary with receptor type; however, receptor
type is chosen here for convenience. The difference between these two receptors is in the
exposure factors, such as body weight and inhalation rate, used to calculate risk for carcinogens.
There is no difference between them for noncarcinogens because calculation of noncarcinogenic
4-29
-------
IWAIR User's Guide Section 4.0
risk does not depend on exposure factors. The IWAIR Technical Background Document
describes the exposure factors used for residents and workers. The assumptions for workers
reflect a full-time, outdoor worker. The exposure duration for workers is the smaller of 7.2 years
or the operating life of the unit. The assumptions for residents reflect males and females from
birth through age 30; it is important to consider childhood exposures because children typically
have higher intake rates per kilogram of body weight than adults. The actual exposure duration
used for residents is the smaller of 30 years or the operating life of the unit that you entered.6 For
exposure durations less than 30 years, exposure starts at birth and continues for the length of the
exposure duration, using the appropriate age-specific exposure factors. Use the drop-down box
positioned under the RECEPTOR TYPE column heading to select either WORKER or RESIDENT.
B. Enter User-Specified Dispersion Factors (Screen SB)
For each receptor specified, enter site-specific unitized dispersion factors (n.g/m3 per
|j,g/m2-s) in the text box located under USER OVERRIDE. You may need to normalize modeled
dispersion factors to a unit concentration by dividing the modeled dispersion factor by the
emission rate used in dispersion modeling (in |j,g/m2-s) if it was not 1 |J,g/m2-s. For example, if
you ran your dispersion model using an emission rate of IE-6 |o,g/m2-s, then you would need to
divide all your dispersion factors by IE-6 to normalize them to a concentration of 1 |J,g/m2-s.
C. Enter Source and Justification for User-Specified Dispersion Factors (Screen SB)
The program will prompt you to provide justification for user-specified dispersion data
and documentation of the estimation method applied. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
Done. Once you have entered dispersion data, click on the | DONE| button to open the
RESULTS tab. Proceed to Section 4.6, Results.
4.6 Risk Results (Screen 6)
The cancer and noncancer risk estimates attributable to emissions from a WMU can be
calculated for residents and workers using IWAIR. The program combines the constituent's air
concentration with receptor exposure factors and toxicity benchmarks to calculate the risk from
concentrations managed in the unit. For each receptor, IWAIR calculates air concentrations
using emission and dispersion data specified or calculated in previous screens. To reflect
exposure that would occur in a lifetime (i.e., from childhood through adulthood), the model
applies a time-weighted-average approach. This approach considers exposure that would occur
during five different phases of life (i.e., Child < 1 year, Child 1-5 yrs, Child 6-11 yrs, Child
12-18 yrs, and Adult). The exposure factors addressed as part of this approach include
inhalation rate, body weight, exposure duration, and exposure frequency. Default values applied
An exception to this is that the exposure duration for land application units is 7.2 years for workers and 30
years for residents regardless of the operating life entered for the unit. This allows IWAIR to account for postclosure
exposures, which are assumed to occur with land application units but not with other units.
4^30
-------
IWAIR User's Guide
Section 4.0
by IWAIR were identified based on data presented in EPA's Exposure Factors Handbook
(U.S. EPA, 1997a) and represent average exposure conditions. IWAIR incorporates standard
toxicity benchmarks (CSFs for carcinogens and RfCs for noncarcinogens) for 95 constituents.
These health benchmarks were obtained primarily from EPA's IRIS and the HEAST (U.S. EPA,
2001, 1997b). IWAIR uses these data to perform a risk calculation. See the IWAIR Technical
Background Document for documentation of the equations.
Please note that all calculated values on the RESULTS screen will be lost if you return to a
previous screen and make changes.
Bfn Industrial Waste - [6. Results: Risk based on Chemical Concentrations]
File Help
Method Met Station, WMU
Wastes Managed
WMU Data for CHEMDAT8
Emission Rates
Dispersion Factors
Results
-Results: Calculate Risk at Specified Condition
Select receptor
Distance to receptor Cm)
justification
Source and Justification for User Override Values
1 ,1 ,1 ,2-Tetrachloroethane
Full Citations
RfCref Chemical- Hazard
' specific^ .uctient
Carbon disulfide
lii |2.34E+0( |NA | No ret. _^J |3.1E+01
.39E+o( |NA | NO ret _»J |7.0E-m [iralTj |
l~l I I HI I HI
dl dl
I UP I 3
4 ) Calculate
Screen 6. Risk Results
A. Select Receptor (Screen 6)
Select a single receptor to serve as the focal exposure point for the calculations by
clicking on the option button associated with the receptor of choice. As discussed above under
Section 4.5, you can specify up to five receptors for consideration. However, results can only be
seen on the screen for one receptor at a time. Once results are calculated and displayed for the
receptor of choice, you can select a different receptor by clicking on one of the other receptor
option buttons. You do not need to enter exposure duration—this is set by IWAIR and will be
displayed when you click on the | CALCULATE | button.
4-31
-------
IWAIR User's Guide Section 4.0
B. View or Override Health Benchmarks (Screen 6)
Screen 6 allows you to view the health benchmarks that IWAIR will use in calculating
risk estimates. For each benchmark, the table on the RESULTS screen shows the value and a brief
reference. To see more-complete citations, click on the | FULL CITATIONS | button in the SOURCE AND
JUSTIFICATION box in the upper right corner of the screen.
IWAIR gives you the option of entering your own health benchmarks. If you choose not
to use the IWAIR data, you can enter alternative health benchmarks by opening the drop-down
box in the RFC REF. column of the desired health benchmark and selecting USER-DEFINED, and then
entering a value in the text box for the benchmark. Enter CSFs (per mg/kg-d) in text boxes
located under the CSF heading and RfCs (mg/m3) under the RFC heading. Do not use a reference
dose in the place of a reference concentration. Once you have entered alternative benchmarks,
they are available in future runs, and you may toggle between them and the IWAIR values using
the drop-down reference box.
You must enter a user-defined health benchmark for two chemicals in IWAIR's chemical
database: divalent mercury and 3,4-dimethylphenol. At the time IWAIR was released, no
accepted health benchmarks were available for these chemicals from the hierarchy of sources
used to populate the IWAIR health benchmark database, nor were there data available from these
sources to allow the development of a health benchmark with any confidence. Thus, if you want
to model one of these chemicals, you will have to enter at least one user-defined health
benchmark. See Section 5 of the IWAIR Technical Background Document for further discussion
of how health benchmarks were developed for IWAIR.
C. Enter Source and Justification for User-Specified Values (Screen 6)
If you choose to override the IWAIR-provided benchmarks, you should specify the source
and the justification of the alternative data in the text box. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
D. Direct IWAIR to Calculate Risk (Screen 6)
Click on the |CALCULATE! button to calculate exposure duration, air concentration, risk, and
HQ for each chemical.
E. View Air Concentration (Screen 6)
Air concentration at the selected receptor point is displayed for each chemical identified
as managed. For land application units, IWAIR calculates three different air concentrations,
based on three different underlying emission rates: a 30-year average for residents for
carcinogens, a 7-year average for workers for carcinogens, and a 1-year maximum for residents
or workers exposed to noncarcinogens. Depending on the receptor selected and the chemical,
IWAIR displays the appropriate air concentration. However, for chemicals that are both
carcinogens and noncarcinogens, only the 30- or 7-year average used for the carcinogenic risk
4-32
-------
IWAIR User's Guide Section 4.0
calculation is displayed. To calculate the 1-year maximum used in the noncarcinogenic HQ
calculation, multiply the emission rate shown on the EMISSION RATES screen by the dispersion factor,
and then multiply by 1,000,000 (to convert units).
F. View Risk and Hazard Quotient (Screen 6)
Cancer risk estimates and HQs (both unitless), respectively, are displayed for each
carcinogen and noncarcinogen identified as being managed. IWAIR calculates lifetime excess
individual cancer risk. This is the probability that an individual exposed at the specified level,
under the specified exposure assumptions, will consequently contract cancer during his or her
lifetime. Although the risk is unitless, it reflects probability. Thus, a risk of IE-5 means that an
individual has 1 chance in 100,000 of contracting cancer as a result of exposure.
For noncarcinogens, the HQ is a ratio of the air concentration to which an individual is
exposed, to the RfC. The RfC is an estimate (with uncertainty spanning perhaps an order of
magnitude) of a daily exposure to the human population (including sensitive subgroups) that is
unlikely to pose an appreciable risk of deleterious noncancer effects during an individual's
lifetime. It is not a direct estimator of risk but rather a reference point to gauge the potential
effects. At exposures increasingly greater than the RfC, the potential for adverse health effects
increases; however, lifetime exposure above the RfC does not imply that an adverse health effect
would necessarily occur.
In addition, a total cancer risk estimate, which is the sum of the chemical-specific risk
estimates, is displayed. No total noncancer risk is calculated because noncancer risks are
appropriately summed only when the same target organ is affected.
Done. Click the | DONE | button to initiate a new run or save the run that you have just
completed. A dialog box will appear to guide you through starting a new run or saving the
current run.
4-33
-------
-------
IWAIR User's Guide
Section 5.0
5.0 Completing Allowable Waste Concentration
Calculations
IWAIR allows you to develop allowable waste concentrations (Cwaste) that may be
protectively managed in a WMU. The calculation method can be applied in calculating waste
concentrations for both wastewaters (Cwaste in mg/L) and solid waste (Cwaste in mg/kg). These
concentrations are estimated based on user-defined target cancer and noncancer risk levels (e.g.,
IE-5 or 1E-6 for carcinogens, or an HQ of 0.5 or 1 for noncarcinogens), which you define on
the RESULTS screen.
The release of a chemical into the
atmosphere is influenced by whether a waste
is an aqueous- or organic-phase waste.
IWAIR can apply either an aqueous or
organic waste equilibrium partitioning
algorithm. These partitioning algorithms are
discussed in detail in the IWAIR Technical
Background Document.
EPA anticipates that most Industrial D
wastes managed by the users of IWAIR will
be aqueous-phase wastes with no chemicals
above the typical solubility or saturation
limits; therefore, the allowable concentration
calculation is initially based on an aqueous-
phase waste. For some chemicals in some
units, it may not be possible to reach the
target risk without the concentration
exceeding the solubility limit (in wastewaters) or the soil saturation limit (in solid wastes) of the
chemical. Once these limits are exceeded, the waste is better modeled as organic. In this case,
IWAIR will switch to organic-phase emission rates and continue.1 If the target risk is still not
reached when the concentration reaches the maximum 1,000,000 mg/kg or mg/L, then the
program will output a concentration of 1,000,000 and will note the maximum risk (or HQ)
achievable.
Aqueous-phase waste: a waste that is predominantly
water, with low concentrations of organics. All
chemicals remain in solution in the waste and are
usually present at concentrations below typical
solubility or saturation limits. However, it is possible
for the specific components of the waste to raise the
effective solubility or saturation level for a chemical,
allowing it to remain in solution at concentrations
above the typical solubility or saturation limit.
Organic-phase waste: a waste that is predominantly
organic chemicals, with a high concentration of
organics. Concentrations of some chemicals may
exceed solubility or saturation limits, causing those
chemicals to come out of solution and form areas of
free product in the WMU. In surface impoundments,
this can result in a thin organic film over the entire
surface.
1 For formaldehyde, the organic-phase emissions are higher than aqueous-phase emissions, and in order to
be protective, the allowable concentration calculation is always based on an organic-phase waste.
5-1
-------
IWAIR User's Guide Section 5.0
IWAIR is structured in a stepwise framework. Through the use of a series of screens,
IWAIR assists in selecting calculation options, identifying and entering required inputs, and
generating desired outputs. There are four different pathways you can follow in performing a
calculation:
• Pathway 1: Using CHEMDAT8 emission rates and ISCST3 default dispersion
factors
• Pathway 2: Using CHEMDAT8 emission rates and user-specified dispersion
factors
• Pathway 3: Using user-specified emission rates and ISCST3 default dispersion
factors
• Pathway 4: Using user-specified emission rates and dispersion factors.
Guidance for determining which modeling pathway to follow is provided in Section 3.3. The
stepwise approach employed by IWAIR to assist in calculating waste concentration, whether you
are following Pathway 1, 2, 3, or 4, is shown in Figures 5-1, 5-2, 5-3, and 5-4, respectively. The
seven steps of the estimation process are shown down the right side of each figure, and the user
input requirements are specified to the left of each step. The types of input data required will
vary depending on the modeling pathway chosen. Screen-by-screen, IWAIR walks you through
the steps of an allowable concentration calculation to arrive at protective waste concentration
estimates.
This section provides screen-by-screen guidance that describes the data that are required
as input to each screen and the assumptions that are interwoven in the calculation being
performed. The guidance provided in this section will assist you in completing an allowable
concentration calculation. You will not need to reference all of the information provided in this
section because the guidance addresses all four of the modeling pathways. Follow only those
subsections that are applicable to your chosen pathway.
5-2
-------
IWAIR User's Guide
Section 5.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
User Specifies:
• Constituents (choose up to 6)
User Specifies:
• CHEMDAT8 option
• Facility location for meteorological input
• WMU information (i.e., design and
operating parameters)
User Specifies:
• Receptor information (i.e., distance and type)
User Specifies:
• Risk level
Allowable concentration
calculation
T
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
Define the Waste Managed
Add/modify chemical properties
data, as desired
CHEMDAT8
Determine Dispersion Factors
Interpolated from ISCST3 default
dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Calculate Results
Allowable Waste Concentration Calculation
ste for wastewaters (mg/L)
ste f°r solid wastes (mg/kg)
Figure 5-1. IWAIR approach for completing allowable waste concentration calculations,
Pathway 1: Using CHEMDAT8 emission rates and ISCST3 default
dispersion factors.
5-3
-------
IWAIR User's Guide
Section 5.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
User Specifies:
• Constituents (choose up to 6)
User Specifies:
• CHEMDAT8 option
• Facility location for meteorological input
• WMU information (i.e., design and
operating parameters)
User Specifies:
• Dispersion factors
• Receptor information (i.e., distance and type)
User Specifies:
• Risk level
Allowable concentration
calculation
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
Define the Waste Managed
Add/modify chemical properties
data, as desired
CHEMDAT8
Determine Dispersion Factors
User-specified dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Calculate Results
Allowable Waste Concentration Calculation
ste f°r wastewaters (mg/L)
t for solid wastes (mg/kg)
Figure 5-2. IWAIR approach for completing allowable waste concentration calculations,
Pathway 2: Using CHEMDAT8 emission rates and user-specified dispersion
factors.
5-4
-------
IWAIR User's Guide
Section 5.0
User Specifies:
• Calculation option
Allowable concentration
calculation
User Specifies:
• WMU type
User Specifies:
• Constituents (choose up to 6)
Land application unit
Waste pile
Surface impoundment
Landfill
Add/modify chemical properties,
as desired
User Specifies:
• Emission rates
Determine Emission Rates
User-specified emission rates
User Specifies:
• WMU area (and height for waste pile)
• Facility location for meteorological input
• Receptor information (i.e., distance and type)
Determine Dispersion Factors
Interpolated from ISCST3 default
dispersion factors
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
User Specifies:
• Risk level
Allowable Waste Concentration Calculation
3
for solid wastes (mg/kg)
Figure 5-3. IWAIR approach for completing allowable waste concentration calculations,
Pathway 3: Using user-specified emission rates and ISCST3 default
dispersion factors.
5-5
-------
IWAIR User's Guide
Section 5.0
User Specifies:
• Calculation option
User Specifies:
• WMU type
User Specifies:
• Constituents (choose up to 6)
User Specifies:
• Emission rates
User Specifies:
• Dispersion factors
• Receptor information (i.e., distance and type)
User Specifies:
• Risk level
Allowable concentration
calculation
Identify WMU
Land application unit
Waste pile
Surface impoundment
Landfill
Define the Waste Managed
Add/modify chemical properties,
as desired
User-specified emission rates
Determine Dispersion Factors
User-specified dispersion factors
T
Calculate Ambient Air Concentrations
Calculates ambient air concentrations for
each receptor based on emission and
dispersion data
Allowable Waste Concentration Calculation
for solid wastes (mg/kg)
Figure 5-4. IWAIR approach for completing allowable waste concentration calculations,
Pathway 4: Using user-specified emission rates and dispersion factors.
5-6
-------
IWAIR User's Guide
Section 5.0
A. Select
calculation
method
C. Select met
station search
option
Enter zip code
and search for
met station
Enter latitude
and longitude
and search for
met station
D. View
selected met
station
File Help
Emission R.ates | ' M .dors j Results
Method, Met. Station, WMU } -ed J WMU Data for CHEMDAT3 1
| 1. Select Calculation Method p2. Select Waste Management Unit (WMU) Type _
(• fcaicuiate risk' Calculation to estimate risk for specified W
•4 ! ' chemical concentrations ** Surface impoundment
f* Calculate allowable Calculation to estimate chemical f Land application unit
concentration concentrations based on specified risk
1 C Active landfill
1 3. Selection of Best Meteorological Station for Site i ^ Waste pile
Y (* Search by zip code
f* Search by latitude and longitude coordinates
Enter 5 digit Zip Code of Site
' • Search
i . in ii ] .1 I i i 1 . ' i'.»
-> r r r
1 I
Selected Meteorological Station for Site
4 View Map
! 4. Select Emissions and Dispersion Option *
Use CHEMDAT8 to estimate emission ^
Use CHEMDAT8 rates and use dispersion factors
provided
1 OR 1
Enter Emission Directly enter emission rates without
_, using CHEMDAT8 and use disperion
factors provided
OR
Enter Emission & Directly enter emission rates and
Dispersion Data aspersion factors
- B. Select
WMU type
_ E. Select
emission and
dispersion
option
Screen 1A. Method, Meteorological Station, WMU
5.1 Method, Meteorological Station, WMU (Screen 1A)
A. Select Calculation Method (Screen 1A)
Select the calculation method by clicking on the | CALCULATE ALLOWABLE CONCENTRATION | option
button. Detailed guidance for selecting the appropriate mode of calculation is provided in
Section 3.1.
B. Select Waste Management Unit (WMU) Type (Screen 1A)
Identify the WMUs that are used to manage wastes of concern at your facility and run the
model separately for each unit type. The four unit types that are addressed as part of this
guidance include surface impoundments (aerated and quiescent), active landfills, waste piles, and
tilled land application units. A detailed description of these unit types is provided in Section 3.2.
Select one of the four WMU types shown in Screen 1A by clicking on the appropriate option
button.
C. Select Meteorological Station Search Option (Screen 1A)
The two search options available include searching by the site's 5-digit zip code or by its
latitude and longitude. Select the appropriate search option and enter the appropriate
information. This information is used to link the facility's location to one of the 60 IWAIR
meteorological stations. The 60 stations cover the 48 contiguous states, Hawaii, Puerto Rico, and
5-7
-------
IWAIR User's Guide Section 5.0
parts of Alaska. Data from the 60 stations (shown on maps in Screen IB, viewed by clicking on
the | VIEW AMP | button shown on Screen 1 A) were used as inputs to the air dispersion modeling
effort conducted to develop the default dispersion factors contained in the IWAIR tool. They are
also used as inputs to CHEMDAT8 emission modeling (e.g., annual average temperature and
wind speed). Additional information on this air dispersion modeling effort and the 60
representative meteorological stations is provided in Section 3.3.
Enter 5-Digit Zip Code and Search for Meteorological Station
Enter a 5-digit zip code and click on the | SEARCH | button to identify the default
meteorological station. If the zip code was entered incorrectly or if no data were provided
at all, message boxes will appear to indicate the specific problem that the tool
encountered so that you can supply the needed data. The zip code database includes zip
codes established through 1999. If your facility has a new zip code that was established
more recently, you will get an error message indicating that it is not a valid zip code
because it is not in IWAIR's database. If this occurs, you can use your old zip code, use a
nearby zip code, or select a meteorological station using latitude and longitude.
Enter Latitude and Longitude Information and Search for Meteorological Station
As shown in Screen 1 A, enter the latitude and longitude of the site in degrees, minutes,
and seconds. At a minimum, the program requires degrees for latitude and longitude to
be entered. If available, the minutes and seconds should be supplied to ensure that the
most appropriate station is selected for a site. After these data are entered, click on the
I SEARCH | button to identify the default meteorological station. If the latitude and longitude
information was entered incorrectly or if no data were provided at all, message boxes will
be displayed that indicate the specific problem that the tool encountered so that you can
supply the needed data.
D. View Selected Meteorological Station (Screen 1A)
The meteorological station selected by the tool will be displayed in the text box. Once
the meteorological station is selected, you are encouraged to click on the | VIEW MAP | button to
view the maps showing the 60 meteorological stations to ensure that the selection was made
correctly. For example, if the latitude of a site was entered incorrectly, then the selected
meteorological station would likely not be the most representative station. In this case, the map
will help you identify this error before proceeding with the calculations. Clicking on the | VIEW
MAP | button will bring up a map of the 48 contiguous states (Screen IB, shown here). You may
view six additional maps (regional maps for the northeastern, southeastern, and western areas of
the 48 contiguous states, as well as maps of Hawaii, Alaska, and Puerto Rico) by clicking on the
appropriate button at the bottom of Screen IB. The | CLOSE| button returns you to the METHOD, MET.
STATION, WMU SCREEN (Screen 1 A).
5-8
-------
IWAIR User's Guide
Section 5.0
| Industrial Waste - [Ib. Maps showing the Met Stations]
File Help
Emission Rates
I
Dispersion Factors
T
Results
Method, Met. Station, WMU \~
astes Managed J '.•v'MU Data for CHEMDAT8 1
120°W
Continental U.S. Western U.S. Northeastern U.S. Southeastern U.S. Alaska Hawaii Puerto Rico
Alaska Hawaii
I close ||
Screen IB. Map of 48 Contiguous States Showing 60 Meteorological Station
E. Select Emission and Dispersion Option (IWAIR-Generated or User-Specified)
(Screen 1A)
You must select from the IWAIR emission and dispersion data options. Under these
options, you have the flexibility of conducting modeling using IWAIR-generated emission rate
and dispersion factor estimates, user-specified emission and dispersion estimates, or a
combination of IWAIR-generated and user-specified estimates.
The tool uses emission rate and dispersion factor estimates in both the risk and allowable
concentration modes. As seen in Screen 1 A, you must select one of the three options provided
for obtaining emission and dispersion data:
5-9
-------
IWAIR User's Guide Section 5.0
• Use CHEMDAT8
Select | USE CHEMDAT81 to use CHEMDAT8 for calculating the emissions from
your unit regardless of whether you want to calculate or enter dispersion factors.
This allows you to enter a variety of unit-specific information that IWAIR will use
to develop chemical-specific emission rate estimates through the use of EPA's
CHEMDAT8 model. These inputs also provide the information needed to use the
ISCST3 dispersion factors provided with IWAIR; however, you may also enter
your own dispersion factors. You will not be allowed to override the IWAIR
emission estimates on subsequent screens in allowable concentration mode. This
option corresponds to Pathways 1 and 2 (see Section 3.3 and Figures 5-1 and 5-2).
• Enter Emission Rates
Select | ENTER EMISSION RATES | to enter your own site-specific emission rates (g/m2-s
per mg/kg of mg/L) on a subsequent screen. Rates may be developed based on
monitoring data or measurements or by conducting modeling with a different
emission model. If your emission rates are in g/s, they will also have to be
normalized by dividing by the area of the unit in m2. In addition, these emission
rates must be unitized (i.e., normalized to a unit waste concentration). This can be
done by dividing the emission rate in g/m2-s by the waste concentration in mg/L or
mg/kg. Under this option, IWAIR can be used to estimate dispersion based on
ISCST3 default dispersion factors. If this option is selected, you will still be
allowed to override the IWAIR dispersion factors on subsequent screens with site-
specific unitized dispersion factors (|a.g/m3 per |j,g/m2-s). Once the | ENTER EMISSION
RATES | command button is selected, a message box will appear that directs you to
enter WMU area (m2). If a waste pile is being modeled, a subsequent box will
appear for the height of the unit to be entered. These WMU data are used by the
model to calculate dispersion estimates. This option corresponds to Pathway 3
(see Section 3.3 and Figure 5-3).
• Enter Emission, Dispersion Data
Select | ENTER EMISSION & DISPERSION DATA| to enter your own emission estimates
(g/m2-s per mg/kg or mg/L) and unitized dispersion factors (|J.g/m3 per |j,g/m2-s).
Emission rates may be developed based on monitoring data or measurements or
by conducting modeling with a different emission model. If your emission rates
are in g/s, they will also have to be normalized by dividing by the area of the unit
in m2. In addition, these emission rates must be unitized (i.e., normalized to a unit
waste concentration). This can be done by dividing the emission rate in g/m2-s by
the waste concentration in mg/L or mg/kg. Dispersion factors may also need to be
unitized by dividing by the emission rate (in g/m2-s) used in dispersion modeling.
This option corresponds to Pathway 4 (see Section 3.3 and Figure 5-4).
5-10
-------
IWAIR User's Guide
Section 5.0
B. Select
sorting
option for
identifying
chemicals
A. Add/
modify
chemicals
C. Identify
chemicals
in waste
i
— i
File Help
Emission Rates
Method, Met. Station, WMU f
To select chemical in management unit, cl
To remove chemical in management unit,
To add a chemical to the list or to modify r.
J[* Sort by chemical name
r Sort by CAS number
• Add/Modify Chemicals
Benzo(a)pyrene [50-32-8]
Bromodichloromethane [75-27-4]
Carbon disulfide [7S-15-0]
SfflWSIIJHPIIPilBBJBflBBBBiil
Chlorobeniene [1 08-90-7]
Chlorodibromomethane [124-48-1]
Chloroform [67-66-3]
Chloroprene [126-99-8]
Cresols (total) [1 31 9-77-3]
Cumene [98-82-8]
Cyclohexanol [108-93-0]
Dichlorodifluoromethane [75-71 -8]
Epichlorohydrin [1 06-89-8]
Bhylbenzene [100-41-4]
Bhylene dibromide [106-93-4]
Bhylene glycol [107-21-1]
Bhylene oxide [75-21-8]
J Jispersion Factors J Results
Wastes Manag
Bd |
Identify Chemicals of Concern
ck on chemical in list and click "Add »". or double-click on chemical in list
select chemical to remove and click "^Remove"
roperties for a user-defined chemical, click "Add>Modify Chemicals"
•i
Add--
«
Remove
Selec
chen
remo
r
r
r
r
r
r
"t
ve
Chemicals in waste
1 ,1 ,1 ,2-Tetrachloroethane
Acetone
Carbon tetrachloride
Done
D. View
chemicals
Screen 2A. Wastes Managed
5.2 Wastes Managed (Screen 2A)
To perform an allowable concentration calculation, identify the chemical(s) of concern in
the waste.
A. Add/Modify Chemicals (Screen 2A)
IWAIR includes a list of chemicals from which you can identify waste constituents. As a
convenience to the user, IWAIR includes data on 95 constituents (shown with their CAS number
in Section 1, Table 1-1). However, this list of chemicals may not include all the organic
chemicals in your waste, and the data for these 95 chemicals may not match your site-specific
conditions for some properties. Therefore, IWAIR has the capability to add or modify chemicals.
To add or modify chemical data, click on the | ADD/MODIFY CHEMICALS | button. This will bring up
Screen 2B, ADD/MODIFY CHEMICALS.
5-11
-------
IWAIR User's Guide
Section 5.0
H P| Industrial Waste - [2b. Add/Modify Lhemicalsl
A3. Enter or
view chemical
name and
CAS number
A4. Enter
chemical
properties data
A5. Clear entry
A6. Save entry
-
File Help
Emission Rates |
y
Dispersion Factors | Results
Wastes Managed
1 WMU Data for CHEMDAT8 "|
Enter information for new chemical into form or double-click chemical from list box on which to base new entry.
Chemical name: |j
-•
CAS number:
Molecular wt
(B/cj-mole):
Density (gfcmS): 1
«
Vapor pressure 1
(mmHcj):
Henry's law constant I
(atm-m3/mol-K):
Solubility (mgrt_): 1
Soil biodegradation I —
rate (s-1):
Antoine's constants: A:
Health benchmarks:
Cancer slope factor I
(mg/kg/d)-1 :
- - (enter eading spaces if necessary)
Diff usivity in water |~
(cm2/s):
Diff usivity in air
(cm2/s):
log(Kow): I
K1 (L/g-h): I
Kmax (mg VO/g-h): I
Hydrolysis rate 1
(s-1): I
Reference I
concentration (mg/m3): I
Chemicals currently in database:
T Sort by chemical name
C Sort by CAS number
1 ,1 ,1 ,2-Tetrachloroethane [630-20-6] _^|
1 ,1 ,1 -Trichloroethane [71 -5S-6]
1,1 ,2 ,2-Tetrachloroethane [79-34-5] I
1 ,1 ,2-Trichloro-1 ,2,2-trifluoroethane [76-1 3-1 ]
1 ,1 ,2-Trichloroethane [79-00-5] 9
1 ,1 -Dichloroethylene [75-35-4]
1 ,2,4-Trichlorobenzene [1 20-32-1 ]
1 ,2-Dibromo-3-chloropropane [96-1 2-8]
1 ,2-Dichloroethane [107-06-2]
1 ,2-Dichloropropane [78-87-5]
1 ,2-Diphenylhydrazine [1 22-66-7]
1 ,2-Epoxybutane [106-88-7]
1 ,3-Butadiene [106-99-0]
1,4-Dioxane [123-91-1] H
1 1 — _
^\ 1 M
J
Al. Select
sorting option
for identifying
chemicals
A2. Select a
chemical to
modify
A7. Delete a
chemical
A8. Return to
wastes
managed
screen
Screen 2B. Add/Modify Chemicals
The ADD/MODIFY CHEMICALS screen will initially appear with no data in any of the fields. You
have four options:
• Add a new chemical. To do this, enter all data, including chemical name and
CAS number, manually.
• Add a new entry for a chemical already in the database. To do this, select an
existing entry for the chemical for which you wish to add an entry; if you select a
user-defined entry, IWAIR will ask if you want to create a new entry. Click on
I YES |. If you select an original IWAIR entry, IWAIR will automatically create a
new entry.
• Modify the data in an existing user-defined entry. To do this, select the
chemical to modify; when IWAIR asks if you want to create a new entry, click on
I No |. Original IWAIR entries may not be modified; if you select one, IWAIR will
automatically create a new entry.
• Delete an existing user-defined entry. Select the entry to delete. Original
IWAIR entries may not be deleted.
5-12
-------
IWAIR User's Guide Section 5.0
To ensure the integrity of the original IWAIR data and distinguish user-defined entries,
IWAIR will automatically generate a unique identifier for each chemical entry added to the data
set in the format "User X," where "X" is an entry number and "User" indicates it is a user-
defined entry. This identifier will be appended to the chemical name to uniquely identify each
entry. This identifier will be shown on screens and reports whenever the chemical is identified to
clearly indicate which chemical entry has been used.
Mercury is included in the IWAIR database in both divalent and elemental forms, but
because of code modifications needed for mercury (to reflect differences in its behavior, since it
is not an organic chemical), you may not create additional or modified entries for mercury.
Al. Select Sorting Order for Identifying Chemicals (Screen 2B)
The list of chemicals that is currently available in the database is shown here so that you
can select constituents to modify. This list includes the 95 constituents included with
IWAIR, as well as any you have already added to the IWAIR database. To facilitate the
chemical selection process, IWAIR allows you to sort this list of chemicals alphabetically
by chemical name, or by CAS number. As shown in Screen 2B, select a sort order by
clicking on the button to the left of the sorting option of choice.
A2. Select a Chemical to Modify (Screen 2B)
If you wish to add a new entry for an existing chemical or modify an existing user-defined
entry, double-click on the chemical name in the list of chemicals. This will display the
data for that chemical on the ADD/MODIFY CHEMICALS screen. If you select one of the 95
original IWAIR chemicals, a new entry will be generated automatically with a new,
unique user-defined identifier. If you select a user-defined entry, IWAIR will ask if you
want to create a new entry. Click on | YES | to create a new entry (you will be able to
modify the data) or | No| to edit the existing entry.
A3. Enter or View Chemical Name and CAS Number (Screen 2B)
If you selected a chemical to modify or to update with a new entry, the chemical name
and CAS number will be displayed. These may not be edited, to preserve the integrity of
the unique chemical identifiers. If you are adding a new chemical and therefore entering
all data manually, you will need to enter an appropriate chemical name and CAS number
in these text boxes. Do not include a "User X" designation in your chemical
name—IWAIR will append that automatically. Chemical names may not contain
apostrophes (') or quotations marks ("). CAS numbers that are shorter than the maximum
length should be prefaced with leading spaces, not zeros.
A4. Enter Chemical Properties Data (Screen 2B)
Enter values for all chemical properties shown on the screen. Use the mouse to click in
each text box, or use the | TAB | key to move between the boxes. Except for health
benchmarks, you may only enter numeric values (although you may enter numeric values
5-13
-------
IWAIR User's Guide Section 5.0
in scientific notation). For health benchmarks, you may also enter "NA." Be sure to
enter values in the units shown. Additional guidance on obtaining values for these
parameters is available in Appendix B, Section B.2.2.3.
You may enter user-defined health benchmarks may be entered both here, in a user-
defined chemical record, and on the RESULTS screen. On the RESULTS screen, you can enter
them directly into an IWAIR chemical record without overwriting the original IWAIR
value. If you are entering a new or modified chemical entry, you should enter any user-
defined health benchmarks here. However, you need not create a new chemical entry
here just to change the benchmark of an IWAIR chemical; you can enter the user-defined
health benchmark on the RESULTS screen.
AS. Clear Entry (Screen 2B)
To clear an unwanted entry from the ADD/MODIFY CHEMICALS screen without saving, click on
the | CLEAR | button. You will be asked to confirm that you want to clear the data.
A6. Save Entry (Screen 2B)
Once all data have been entered, you can save by clicking on the | SAVE| button. IWAIR
does some limited range checking to ensure values are within physically possible ranges;
if an entry is not in the acceptable range, IWAIR will display an error message with the
accepted range. These ranges are intended to eliminate only impossible entries (e.g.,
negative values for many properties) or values that will cause the model to fail. The
actual typical range for most of the chemical properties is likely smaller than the accepted
range. Once all data values have been validated and the entry added to the database, the
form will be cleared.
A 7. Delete a Chemical (Screen 2B)
You may delete a user-defined chemical entry on the ADD/MODIFY CHEMICALS screen by
selecting the chemical from the list of chemical entries and clicking on the (DELETE USER-
DEFINED CHEMICAL | button. It is not necessary to double-click on the chemical to bring up its
data before deleting; a single click to select the entry in the list is sufficient. If you have
selected an original IWAIR chemical entry, an error message will appear indicating that
the entry cannot be deleted. If you have selected a user-defined entry, a message will
appear to confirm that you want to delete the entry. If you select I YES |, the entry will be
deleted from the database and you will be returned to the ADD/MODIFY CHEMICALS screen. The
list of chemicals on this screen will be updated to reflect the removal of the entry. If you
select I No |, you will be returned to the screen, and the chemical will not be deleted.
Note that the deletion of a chemical entry used in a saved analysis will lead to the failure
of the saved analysis to reload.
5-14
-------
IWAIR User's Guide Section 5.0
A8. Return to Wastes Managed Screen (Screen 2B)
Once you have completed all desired data additions, modifications, and deletions, click
the | RETURN | button to return to the WASTES MANAGED screen. If you have unsaved data,
IWAIR will warn you and ask if you want to proceed. If you select I YES |, the unsaved
data will be lost. If you select I No |, you will be returned to the ADD/MODIFY CHEMICALS
screen, where you can save your data by selecting | SAVE |. The list of available chemicals
in the WASTES MANAGED screen will be updated to include any new entries and to omit any
deleted entries.
B. Select Sorting Option for Identifying Chemicals (Screen 2A)
Once you have returned to the WASTES MANAGED screen, you can identify waste constituents
from the list of chemicals included in IWAIR. This list includes the 95 constituents included
with IWAIR, as well as any you add to the IWAIR database using the ADD/MODIFY CHEMICALS feature.
The 95 constituents included with IWAIR are shown with their CAS number in Section 1, Table
1-1. To facilitate the chemical identification process, IWAIR allows you to sort this list of
chemicals alphabetically by chemical name, or by CAS number. As shown in Screen 2A, select a
sort order by clicking on the button to the left of the sorting option of choice.
C. Identify Chemicals in Waste (Screen 2A)
Identify up to six chemicals in a waste for modeling with IWAIR. Identify a chemical by
clicking on the chemical name or CAS number and clicking on the | ADD» | command button. To
remove a waste constituent from consideration, select the check box located to the left of the
chemical name and click the | «REMOVE| command button. User-defined entries are identified in
this list by the modifier "User X" appended to the chemical name, where "X" is a unique
number.
You may choose to simultaneously model the same chemical using multiple entries from
the chemical database. You may want to do this to compare results based on changes you have
made in chemical properties.
D. View Selected Chemicals (Screen 2A)
The chemicals you identified for consideration are displayed in text boxes shown on
Screen 2A. You can remove waste constituents from consideration by selecting the check box to
the left of the chemical and clicking the | «REMOVE| command button.
5.3 Enter WMU Data for Using CHEMDAT8 Emission Rates
If you elected to use CHEMDAT8 emission rates in the calculations (i.e., selected the
| USE CHEMDAT81 command button shown previously on Screen 1 A), you will need to enter WMU
data as specified in this section. If you did not elect to use CHEMDAT8 emission rates, then you
should skip this section and proceed to Section 5.4, Emission Rates. If you elected to enter
5-15
-------
IWAIR User's Guide Section 5.0
emission rates and use ISCST3 dispersion factors, you will be asked to enter the WMU area (and
height, if a waste pile) for ISCST3 before proceeding to the emissions screen.
This section provides guidance on providing input data needed to develop CHEMDAT8
emission estimates for the four unit types addressed by IWAIR.
Surface Impoundments. The major source of volatile emissions associated with surface
impoundments is the uncovered liquid surface exposed to the air (U.S. EPA, 1991).
Aeration and/or agitation are applied to aid in treatment of the waste, and emissions tend
to increase with an increase in surface turbulence because of enhanced transfer of liquid-
phase contaminants to the air (U.S. EPA, 1991). Parameters to which emissions are most
sensitive include surface area, unit depth, waste concentration, retention time, wind speed
for quiescent systems, and biodegradation. Retention time is not an explicit input, but a
function of impoundment volume and flow.
Land Application Units. Waste can be tilled or sprayed directly onto the soil and
subsequently mixed with the soil by discing or tilling. Waste in a land application unit is
a mixture of sludge and soil. IWAIR allows the modeling of tilled land application units.
If your unit uses spray application, another model may be more appropriate. Air
emissions from land treatment units are dependent on the chemical/physical properties of
the organic constituents, such as vapor pressure, diffusivity, and biodegradation rate.
Operating and field parameters affect the emission rate, although their impact is not as
great as that of the constituent properties.
Active Landfills. IWAIR allows the modeling of emissions released from the surface of
an active (i.e., receiving wastes) landfill. The landfill model is sensitive to the air
porosity of the solid waste, the liquid loading in the solid waste, the waste depth
(assumed to be the same as the unit depth), the constituent concentration in the waste, and
the volatility of the constituent (U.S. EPA, 1991).
Waste Piles. The waste pile emission model is sensitive to the air porosity of the solid
waste, the liquid loading in the solid waste, the waste pile height, the constituent
concentration in the waste, and the volatility of the constituent (U.S. EPA, 1991).
Screens 3A, 3B, 3C, and 3D, respectively, identify the CHEMDAT8 input requirements
for surface impoundments, land application units, landfills, and waste piles. Guidance for
completing each screen is provided below. For some of the required inputs, default values are
provided in the screen text boxes, as well as to the right of the text boxes. These default values
were selected to represent average or typical operating conditions. If appropriate, the defaults
can be applied in the absence of site-specific data; however, you always have the option of
overriding any defaults. The basis for these default values is provided in the IWAIR Technical
Background Document.
5-16
-------
IWAIR User's Guide
Section 5.0
File Help
Emission Rates
Method Met. Station, WMU
I
1
Jispersion Factors j
Wastes Managed | WMU Data for CHEMDATB j
Surface Impoundment Information
Wind speed (m/s)
Temperature (C)
,-SI Dimensions , Loading Informatior
Biodegradation (*" On P
Operating life (yr)
Depth of unit Cm)
Area of unit (m2)
Annual flow of waste
(m3/yr)
No aeration (quiescent)
Diffused air aeration
Mechanical aeration
Both (diffused air & mechanical)
Fraction of surface area agitated
Submerged air flow (m3/s)
[3.473 |
|15.45 |
3ff
10000
2500
r
r
r
(?
C
C
n
n
Type of waste: Aqueous (• Organic C
Default
Molecular weight of waste (g/mol)
Density of waste (g/cm3)
Active biomass (g/L) |n-ns | 0.05
Total suspended solids in influent (grt_) |o.2 | o.2
Total organics into WMU (mg/L) [200 "| 200
Total biorate (mg/g biomass-h) |19 1 9
Default
Oxygen transfer rate (Ib 02/h-hp) |3 | 3
Number of aerators
Total power (hp)
Power efficiency (fraction) |o.83 | 0.83
Impeller diameter (cm) [61 61
Impeller speed (radfc) |l30 130
Done
E. Enter waste
data
D. Enter
mechanical
aeration
information
Screen 3A. WMU Data for CHEMDAT8: Surface Impoundment
File Help
Emission Rates
Dispersion Factors
Results
Method, Mel Station, WMU
Wastes Managed
WMU Data for CHEMDATB
-Meteorological Station Parameters
Wind speed (m/s) I3.473
Temperature (C) |15.45
—Waste/Soil Mixture Porosity Information
Default
Total porosity (volume i^j I 0.61
fraction) l_ I
Air porosity (volume [J^ I g ^
fraction) I 1
Land Application Unit Information
-AU Dimensions and Loading Information
Biodegradation (? Qn f Off
Operating life (yr)
Tilling depth of unit (m)
Area of unit (m2)
Annual waste quantity (Mg/yr)
Number of applications per year
Waste bulk density (g/cm3)
-Waste Characteristics Information (Only for Risk Calculation)-
Aqueous (* Organic C
Molecular weight of waste (g/g-mole)
Screen 3B. WMU Data for CHEMDAT8: Land Application Unit
5-17
-------
IWAIR User's Guide
Section 5.0
File Help
Method, Met. Station, WMU
Wastes Managed
WMU Data for CHEMDAT8
-Meteorological Station Parameters
Wind speed (m/s) 13.473
Temperature (C)
[—Waste Porosity Information-
Default
Total porosity (volume fraction) [o~5I 0.5
Air porosity (volume fraction) |o.25 0.25
Ldi.illill Information
Waste Characteristics Information (Only for Risk Calculation)"
Aqueous (• Organic C
Molecular weight of waste (g/g-mole) I I
-Lanafill Dimensions ana Loaaing information ~
Biodegradation C On (• Off
Operating life (yr)
Total area of landfill (m2)
Total depth of landfill (m)
Total number of cells in landfill
Annual quantity of waste disposed in
landfill (Mgf/r)
Bulk density of waste (g/cm3)
|20
[SOP
|2
|12
|1000
Default *•
1.2
Screen 3C. WMU Data for CHEMDAT8: Landfill
Industrial Waste - [3d. Waste Pile]
File Help
Emission Rales
Dispersion Factors
Method Met Station, WMU
Wastes Managed
I
Results
WMU Data for CHEMDATB ]
—Meteorological Station Parameters
Wind speed (m/s) |3'473
Temperature (C) |15.45
Waste Pile Information
Waste Pile Dimensions and Loading Information
Biodegradation (~ On (• Off
Default
Operating life (yr) Kn
Height of waste pile unit (m) 4
Area of unit (m2) (sOO I
Average quantity of waste in waste pile (Mg/yr) MOO
Bulk density of waste (g/cm3) R~4 I ^ 4
.Total porosity (volume
fraction)
Air porosity (volume fraction)
0.5 |
Q.25 |
Default
0.5
0.25
Aqueous
G Organic C
Molecular weight of waste (g/g-mole)
Screen 3D. WMU Data for CHEMDAT8: Waste Pile
5-18
-------
IWAIR User's Guide Section 5.0
A. View Meteorological Data for Site (Screens 3A, 3B, 3C, and 3D)
Both wind speed and temperature can affect the volatilization rate of a chemical.
Average wind speed and temperature are used as input to the CHEMDAT8 model. Average
annual wind speed is used to select the most appropriate empirical emission correlation equation
in CHEMDAT8; there are several of these correlations, and each one applies to a specific range
of wind speeds and unit sizes. Average annual temperature is used to adjust Henry's law constant
and vapor pressure values (temperature-dependent chemical properties) from a standard
temperature to the ambient temperature at the unit. Drawing from the meteorological data stored
in IWAIR, the program will display the average annual temperature and wind speed available for
the representative meteorological station that was determined for the site in Screen 1 A. You can
enter average wind speed and temperature for your site if the default values are significantly
different.2
B. Enter Unit Design and Operating Data
For all unit types, you may select whether or not biodegradation occurs in your unit.
Select the | ON | option to turn biodegradation on and the | OFF | option to turn it off. The default
setting varies by unit type. See Appendix B, Sections B.3.1.2, B.3.2.3, B.3.3.3, and B.3.4.3, for
further details about the implications of turning biodegradation on or off and the appropriateness
of difference choices for different unit types.
Enter Surface Impoundment Design Data (Screen 3A)
Enter the unit dimensions and loading information in the text boxes shown in Screen 3 A.
The data include the operating life of the unit (yrs), the depth of the unit (m), the area of
the unit (m2), and the annual flow of the waste (m3/yr).
Enter Land Application Unit Design and Operating Information (Screen 3B)
Enter the unit dimensions and loading information in the text boxes shown in Screen 3B.
The data include the operating life of the unit (yrs), tilling depth of the unit (m), area of
the unit (m2), annual waste quantity (Mg/yr), number of applications per year, and waste
bulk density (g/cm3).
Enter Landfill Design and Operating Information (Screen 3C)
Enter the unit dimensions and loading information in the text boxes in Screen 3C. The
model assumes that the landfill is divided into cells, with only one cell active at a time.
Emissions are modeled from the active cell. The data to be entered include the operating
life of the unit (yrs), total area of the unit (m2), depth of the unit (m), number of cells in
your unit, annual quantity of wastes disposed in the unit (Mg/yr), and bulk density of
waste (g/cm3).
These inputs are not used in the dispersion modeling, which uses hourly data, not annual averages.
Therefore, changes to these inputs will not affect the dispersion factors.
5-19
-------
IWAIR User's Guide Section 5.0
Enter Waste Pile Design and Operating Information (Screen 3D)
Enter the unit dimensions and loading information in the text boxes in Screen 3D. The
data include the operating life of the unit (yrs), the height of the pile (m), area of the unit
(m2), annual quantity of waste in the pile (Mg/yr), and bulk density of the waste (g/cm3).
C. For Aerated Surface Impoundments Only — Enter Aeration Data (Screen 3A)
IWAIR models both quiescent (nonaerated) and aerated impoundments. Aeration or
agitation of a liquid waste in an impoundment enhances transfer air (oxygen) to the liquid to
improve mixing or to increase biodegradation (U.S. EPA, 1991). Aeration is achieved through
the use of mechanical mixers, such as impellers (i.e., mechanically aerated), or by sparging air,
which bubbles up from the bottom of the unit (i.e., diffused air aerated). First, select the aeration
option that best describes your unit by clicking the appropriate option button. If you selected one
of the aerated options, provide information to characterize the aeration in your unit. For all
aeration options, you will need to enter the fraction of the surface area agitated (unitless). If you
selected an option including diffused air aeration (diffused air only or both diffused air and
mechanical aeration), you will also need to enter the total submerged air flow (m3/s) of all
diffusers in the impoundment.
If you choose to model an aerated impoundment, you will not have the option of
modeling an organic-phase waste; IWAIR cannot model an organic-phase waste in an aerated
impoundment because of limitations in CHEMDAT8.
D. For Mechanically Aerated Surface Impoundments Only - Enter Mechanical Aeration
Information (Screen 3A)
If a surface impoundment is mechanically aerated, you will need to provide additional
operating parameter information. These data include oxygen transfer rate (Ib O2/hr-hp), number
of aerators, total power (hp), power efficiency (fraction), impeller diameter (cm), and impeller
speed (rad/s).
E. For Surface Impoundments Only - Enter Waste Characteristics Data (Screens 3A)
The waste characteristic information to be entered for surface impoundments includes
active biomass (g/L), total suspended solids into WMU (mg/L), total organics into WMU (mg/L),
and total biorate (mg/g biomass-hr). These parameters are discussed in more detail in
Appendix B.
F. For Land Application Units, Landfills, and Waste Piles Only - Enter Waste Porosity
Information (Screens 3B, 3C, and 3D)
Waste (or soil/waste mixture for land application units) porosity information required as
input includes total porosity (unitless) and air porosity (unitless). Total porosity includes air
porosity and the space occupied by oil and water within waste. Total porosity (et), also
sometimes called saturated water content, can be calculated from the bulk density (BD) of the
waste and particle density (ps) as follows:
5^20
-------
IWAIR User's Guide Section 5.0
et =
BD
where BD and ps are expressed in the same units.
In the absence of site-specific data, IWAIR identifies default values of 0.5 and 0.25,
respectively, for total porosity and air porosity. Air porosity cannot exceed total porosity.
Done. Once you provide the required WMU inputs, click the |DONE| button to enable the
EMISSION RATES tab and open the EMISSION RATES screen. Proceed to Section 5.4, Emission Rates.
IWAIR must calculate emission rates before displaying the EMISSION RATES screen. This is usually
very quick, but if your computer is slow, or if you are modeling a land application unit and with a
large number of total applications (i.e., number of applications per year times operating life),
there can be a noticeable delay before the EMISSION RATES screen is displayed. This is normal, but
should typically not exceed 1 minute on a fast machine or 5 minutes on a slow machine.
5.4 Emission Rates
Guidance for using CHEMDAT8 emission rates or entering your own emission rates is
provided in this section. View and confirm the CHEMDAT8 emission rates as directed in
Section 5.4.1. If you did not elect to use CHEMDAT8 (i.e., if you selected the | ENTER EMISSION
RATES | or | ENTER EMISSION & DISPERSION DATA| command buttons shown previously on Screen 1 A),
proceed to Section 5.4.2, User-Specified Emission Rates.
Please note that all calculated and entered values on the EMISSION RATES screen will be lost if
you return to a previous screen and make changes. This includes both calculated and entered
override emission rate values.
5-21
-------
IWAIR User's Guide
Section 5.0
Hg Industrial Waste - [4a. Emission Rates For Wastes From WMU]
File Help
Method, Met. Station, WMU
Wastes Managed
WMU Data for CHEMDAT8
Emission Rates
Dispersion Factors
Chemical Emissions Estimated Using CHEMDAT8
(Emission of chemical = concentration of waste x emission rate)
I Chemical emissions
Aqueous Organic Override
Chemicals selected {gfm2/s) per (ragftis)
I3.16E-09
1,1,1,2-Tetrachloroethane
Screen 4A. CHEMDAT8 Emission Rates
5.4.1 Using CHEMDAT8 Emission Rates (Screen 4A)
A. View CHEMDA T8 Emission Rates (Screen 4A)
Screen 4A shows the calculated CHEMDAT8 emission rates. Emission rates for the
allowable concentration mode are unitized to a unit waste concentration (i.e., a waste
concentration of 1 mg/kg). For land application units, landfills, and waste piles, emission rates
are linear with concentration; therefore, this unitized emission rate can be adjusted to any specific
concentration by multiplying by the concentration. For surface impoundments, however,
emissions are not linear in the aqueous phase because of biodegradation, which is first order at
low concentrations and shifts to zero order at higher concentrations. The concentration at which
this occurs is chemical-specific. Therefore, for surface impoundments, this screen does not
display emission rates. The actual emission rate used in risk calculations is calculated later,
during the risk calculations.
For landfills and waste piles, emissions are modeled at equilibrium and are assumed to
reflect a long-term average emission rate, normalized to a waste concentration of 1 mg/kg, which
is shown on this screen. In contrast, land application units are not assumed to be at equilibrium;
rather, emissions are calculated for each year of the specified operating life, plus 30 years
postclosure. The emission rates shown on this screen are the maximum single-year emission
5-22
-------
IWAIR User's Guide
Section 5.0
rates for each chemical (which may not reflect the same year for all chemicals), normalized to a
waste concentration of 1 mg/kg. This emission rate is used directly to calculate air concentration
for calculating noncarcinogenic risk. However, for carcinogenic risk, the maximum 7- or 30-year
average emission rate (7-year for a worker and 30-year for a resident, corresponding to the
default exposure durations for each receptor type) is used to calculate air concentration and then
risk.
For all unit types other than surface impoundments, emission rates will be displayed
under both the AQUEOUS and ORGANIC column headings; IWAIR will determine which of these to use
during calculation of the allowable concentration depending on the target risk or HQ and the
chemical's solubility or saturation limit.
These emission rates may not be overridden. Confirm the emission rates to be used in the
calculations by clicking the | DONE | button. The program will automatically enable the DISPERSION
FACTORS tab and open the DISPERSION FACTORS screen. Proceed to Section 5.5, Dispersion Factors.
|R| Industrial Waste - [4b. User Override Emission Rates] [
File Help
Method, Met. Station, WMU J Wastes Managed ~] Wh
Emission
-lates 1 Dispersion F ztors T Results |
User Override Chemical Emissions
(Emission of chemical = concentration of
Chemicals
H ,1 ,1 ,2-Tetrachloroethane
[Acetone
Icarbon disulfide
waste x emission rate)
m
User override emissions *
(gAn2/s)
|i^ |
|2e^6 |
|3e^6| |
Source and Justification for User Override Values
justification
1
Done
A. Enter user-
specified
emissions
B. Enter
source and
justification
for user-
specified
emission rates
Screen 4B. User-Specified Emission Rates
5-23
-------
IWAIR User's Guide Section 5.0
5.4.2 User-Specified Emission Rates (Screen 4B)
A. Enter User-Specified Emissions (Screen 4B)
Enter site-specific normalized emission rates (g/m2-s per mg/kg or g/m2-s per mg/L) in
the text box located under USER OVERRIDE. Your emission rates must be normalized to a unit
concentration. If you have measured or calculated emission rates in g/s for your entire unit, you
will need to divide that emission rate by the total area of your unit (in m2) to obtain area-
normalized emission rates in g/m2-s. You can normalize this emission rate to a unit
concentration by dividing by the waste concentration in mg/L or mg/kg at the time when the
emission rate was measured or calculated. These emission rates should reflect long-term average
emissions, not a short-term peak.
B. Enter Source and Justification for User-Specified Emission Rates (Screen 4B)
The program will prompt you to provide justification for using user-specified emission
rates and documentation of the estimation method applied. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
Done. Once you have entered emission data and source/justification, click the | DONE|
button to enable the DISPERSION FACTORS menu tab and open the DISPERSION FACTORS screen. Proceed to
Section 5.5, Dispersion Factors.
5.5 Dispersion Factors
Dispersion modeling outputs are used to estimate air concentrations to which the various
human receptors are exposed. Guidance for using the ISCST3 default dispersion factors or
entering your own site-specific dispersion factors is provided in Sections 5.5.1 and 5.5.2,
respectively. If you elected to use ISCST3 dispersion factors provided in IWAIR (i.e., selected
the | USE CHEMDAT81 or | ENTER EMISSION RATES | command buttons shown previously on Screen 1 A),
you will need to follow the guidance provided in Section 5.5.1. If you did not elect to use the
default dispersion factors, you should proceed to Section 5.5.2, User-Specified Dispersion
Factors.
Please note that all calculated and entered dispersion factors on the DISPERSION FACTORS
screen will be lost if you return to a previous screen and make changes. This does not include
receptor locations and types but does include calculated and entered override dispersion factor
values.
5-24
-------
IWAIR User's Guide
Section 5.0
Industrial Waste - [5. Dispersion Factors]
File Help
T n n v c r11 d c d c T ,:i u 11 d I: p e r: I u n i a c i o r:, c n i c r v ,:i I u c: I n i o LI:: c r u v c 1r1 c I c c u I u r n n
Dispersion factors for location and unit
size [(ugjtnS per (ug/m2-s)]
C. View
IWAIR
dispersion
factors or
enter user-
specified
dispersion
factors
D. Enter
source and
justification
for user-
specified
dispersion
factors
Screen 5A. Using ISCST3 Default Dispersion Factors
5.5.1 Using ISCST3 Default Dispersion Factors (Screen 5A)
In Screen 5A, you will provide receptor information (i.e., receptor type and distance to
the receptor) and click on the | CALCULATE | button; IWAIR will develop site-specific dispersion
factors based on default dispersion data. If you wish to override the IWAIR-developed
dispersion factors, enter alternate site-specific unitized dispersion factors. If you enter alternative
dispersion factors, you should document the source and the justification for these data in the text
box on the screen.
A. Select Receptor Type and Distance (Screen 5A)
Enter information concerning the receptors of concern (i.e., potentially exposed
individuals). You can specify up to five receptors, including the distance to receptor and the
receptor type. You can specify two receptor types at six distances (25, 50, 75, 150, 500, and
1,000 meters) from the edge of the WMU. You can delete the last receptor entered by deleting
both the distance to receptor and receptor type entries.
Distance to Receptor - For each receptor of concern, determine the distance from the
edge of the unit to the receptor. Based on this distance, select from the six default distances (25,
50, 75, 150, 500, and 1,000 meters) the one that best approximates the location of your receptor,
using the drop-down box positioned under the DISTANCE TO RECEPTOR column heading. Note that
selecting a distance smaller than the actual distance to receptors near your unit will overestimate
5-25
-------
IWAIR User's Guide Section 5.0
risk, and selecting a distance larger than the actual distance will underestimate risk. These
distances correspond to the distances for which air dispersion modeling was conducted to
develop the IWAIR default dispersion factors. The IWAIR Technical Background Document
discusses the analysis that was conducted in determining the appropriateness of these default
distances.
Receptor Type - Two different types of exposed individuals, worker and resident, can be
modeled with IWAIR. The dispersion factors do not vary with receptor type; however, receptor
type is chosen here for convenience. The difference between these two receptors is in the
exposure factors, such as body weight and inhalation rate, used to calculate risk for carcinogens.
There is no difference between them for noncarcinogens because calculation of noncarcinogenic
risk does not depend on exposure factors. The IWAIR Technical Background Document
describes the exposure factors used for residents and workers. The assumptions for workers
reflect a full-time, outdoor worker. The exposure duration for workers is the smaller of 7.2 years
or the operating life of the unit. The assumptions for residents reflect males and females from
birth through age 30; it is important to consider childhood exposures because children typically
have higher intake rates per kilogram of body weight than adults. The actual exposure duration
used for residents is the smaller of 30 years or the operating life that you entered for the unit. For
exposure durations less than 30 years, exposure starts at birth and continues for the length of the
exposure duration, using the appropriate age-specific exposure factors. Use the drop-down box
positioned under the RECEPTOR TYPE column heading to select either WORKER or RESIDENT.
B. Direct IWAIR to Estimate Dispersion Factors (Screen 5A)
After the requested receptor information is provided, click on the | CALCULATE! button to
direct the program to determine an appropriate dispersion factor based on the IWAIR default
dispersion data. The resulting dispersion factor will be displayed for each receptor of concern. A
discussion of the development of IWAIR default dispersion data and the methodology used by
the program in selecting an appropriate dispersion factor for each WMU/receptor combination is
provided in Section 3.3. A more detailed discussion of the air dispersion modeling effort is
provided in the IWAIR Technical Background Document.
For waste piles, IWAIR uses a two-dimensional nonlinear spline to interpolate dispersion
factors for areas and heights different from those included in the dispersion factor database. This
technique is more accurate than a two-dimensional linear interpolation and is less likely to
underestimate the actual dispersion factor. However, on rare occasions, the spline may produce
results inconsistent with the data points nearest the actual area and height. If this occurs, IWAIR
shifts to the linear interpolation technique, which generally produces somewhat lower dispersion
factors. If this occurs, you will see a message to that effect. The interpolation techniques used
for dispersion factors are discussed in greater detail in the IWAIR Technical Background
Document.
5-26
-------
IWAIR User's Guide
Section 5.0
C. View IWAIR Dispersion Factors or Enter User-Specified Dispersion Factors
(Screen 5A)
You may override the program-calculated dispersion factors by entering alternative
dispersion data in the text box located under the USER OVERRIDE column (see Screen 5A).
D. Enter Source and Justification for User-Specified Dispersion Factors (Section 5A)
If you choose to provide alternative dispersion factors, document the source and the
justification for these data in the text box that will appear. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
Done. Once the program has developed dispersion factors, click the | DONE | button to
open the RESULTS tab. Proceed to Section 5.6, Results.
Industrial Waste - [5. Dispersion Factors]
File Help
Method, Met. Station, WMU
Wastes Managed
WMU Data for CHEMDAT8
Emission Rates
Dispersion Factors
Results
Receptor Distance, Type, and Dispersion Factor
To override default dispersion factors, enter values into "User override" column
Dispersion factors for location and unit
size [(ug/m3 per (ug/m2-s)]
Receptor Distance to
no. receptor (m)
Receptor type
[worker -r \
[Resident ^|
I Resident T|
Source and Justification for User Override Values
Done
C. Enter
source and
justification
for user-
specified
dispersion
factors
Screen 5B. User-Specified Dispersion Factors
5.5.2 User-Specified Dispersion Factors (Screen 5B)
A. Select Receptor Type and Distance (Screen SB)
Enter information concerning the receptors of concern (i.e., potentially exposed
individuals). You can specify up to five receptors. The receptor information includes the
5-27
-------
IWAIR User's Guide Section 5.0
distance to receptor and the receptor type. You can specify two receptor types in sixteen
directions at six distances (25, 50, 75, 150, 500, and 1,000 meters) from the edge of the WMU.
You can delete the last receptor entered by deleting both the distance to receptor and receptor
type entries.
Distance to Receptor - For each receptor of concern, determine the distance from the
edge of the unit to the receptor. Based on this distance, select from the six default distances (25,
50, 75, 150, 500, and 1,000 meters) the one that best approximates the location of your receptor,
using the drop-down box positioned under the DISTANCE TO RECEPTOR column heading. These values
are only for your reference and are not used in calculations, since you are entering your own
dispersion factors.
Receptor Type - Two different types of exposed individuals, worker and resident, can be
modeled with IWAIR. The dispersion factors do not vary with receptor type; however, receptor
type is chosen here for convenience. The difference between these two receptor types lies in the
exposure factors, such as body weight and inhalation rate, used to calculate risk for carcinogens.
There is no difference between them for noncarcinogens because calculation of noncarcinogenic
risk does not depend on exposure factors. The IWAIR Technical Background Document
describes the exposure factors used for residents and workers. The assumptions for workers
reflect a full-time, outdoor worker. The exposure duration for workers is the smaller of 7.2 years
or the operating life of the unit. The assumptions for residents reflect males and females from
birth through age 30; it is important to consider childhood exposures because children typically
have higher intake rates per kilogram of body weight than adults. The actual exposure duration
used for residents is the smaller of 30 years or the operating life of the unit that you entered. For
exposure durations less than 30 years, exposure starts at birth and continues for the length of the
exposure duration, using the appropriate age-specific exposure factors. Use the drop-down box
positioned under the RECEPTOR TYPE column heading to select either WORKER or RESIDENT.
B. Enter User-Specified Dispersion Factors (Screen SB)
For each receptor specified, enter site-specific unitized dispersion factors (n-g/m3 per
|o,g/m2-s) in the text box located under USER OVERRIDE. You may need to normalize modeled
dispersion factors to a unit concentration by dividing the modeled dispersion factor by the
emission rate used in dispersion modeling (in |j,g/m2-s) if it was not 1 |J,g/m2-s. For example, if
you ran your dispersion model using an emission rate of IE-6 |j,g/m2-s, then you would need to
divide all your dispersion factors by IE-6 to normalize them to a concentration of 1 |J,g/m2-s.
C. Enter Source and Justification for User-Specified Dispersion Factors (Screen SB)
The program will prompt you to provide justification for using user-specified dispersion
data and documentation of the estimation method applied. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
Done. Once you have entered dispersion data, click the | DONE| button to open the RESULTS
tab. Proceed to Section 5.6, Results.
5-28
-------
IWAIR User's Guide Section 5.0
5.6 Allowable Concentration Results (Screen 6)
Allowable waste concentrations can be calculated from user-specified risk levels. The
program combines the constituent's air concentration with receptor exposure factors and toxicity
benchmarks to calculate the waste concentrations that are protective of human health. For each
receptor, IWAIR calculates air concentrations using emission and dispersion data specified or
calculated in previous screens. To reflect exposure that would occur in a lifetime (i.e., from
childhood through adulthood), the model applies a time-weighted-average approach. This
approach considers exposure that would occur during five different phases of life (i.e., Child < 1
yr, Child 1-5 yrs, Child 6-11 yrs, Child 12-18 yrs, and Adult). The exposure factors addressed
as part of this approach include inhalation rate, body weight, exposure duration, and exposure
frequency. The default values that are applied in developing these time-weighted-average
exposures were identified based on data presented in EPA's Exposure Factors Handbook (U.S.
EPA, 1997a) and represent average exposure conditions. IWAIR incorporates standard toxicity
benchmarks (CSFs for carcinogens and RfCs for noncarcinogens) for 95 constituents. These
health benchmarks were obtained primarily from the EPA's IRIS and the HEAST (U.S. EPA,
2001, 1997b). IWAIR uses these data to perform an allowable concentration calculation. See
the IWAIR Technical Background Document for documentation of the equations.
The approach applied by IWAIR to calculate allowable concentration employs an
iterative calculation algorithm. The program sets an initial waste concentration, calculates risk,
compares that to the target risk, then adjusts the waste concentration and recalculates until the
target risk is achieved.
If you are modeling a land application unit, landfill, waste pile, or quiescent surface
impoundment and have elected to use CHEMDAT8 to calculate emissions, IWAIR will perform
allowable concentration calculations for both an aqueous-phase waste and an organic-phase
waste and will output the lower (or more protective) of the two resulting concentrations. For
most chemicals, that will be the aqueous-phase concentration, but for a few chemicals (most
notably formaldehyde), it will be the organic-phase concentration.3 If you elected to enter your
own emission rates, or if you are modeling an aerated surface impoundment, IWAIR will only
calculate and output concentrations for an aqueous-phase waste.
In performing allowable concentration calculations, IWAIR ensures that calculated
aqueous-phase concentrations do not exceed the soil saturation limit (for land-based units) or the
solubility limit (for surface impoundments) for that chemical. This prevents impossible results
from occurring. Similarly, the program also ensures that calculated organic-phase concentrations
do not exceed 1,000,000 mg/kg. If the target risk or HQ cannot be achieved by any possible
concentration (i.e., in an aqueous-phase waste up to the soil saturation or solubility limit, or in an
organic-phase waste up to 1,000,000 mg/kg), then the program will note the maximum risk or
HQ that can be reached, and the calculated concentration will be set to the concentration that
3 Any concentration at or below the soil saturation limit or solubility limit may occur in either an aqueous-
phase waste or an organic-phase waste. The phase of the waste is not solely determined by the concentration of any
one chemical. For most chemicals, the same concentration in an aqueous-phase waste will produce higher emissions
than in an organic-phase waste; however, formaldehyde is a notable exception.
5^29
-------
IWAIR User's Guide
Section 5.0
results in the maximum possible risk or HQ. This will be either the soil saturation limit or
1,000,000 if you are modeling a land-based unit using CHEMDAT8; the soil saturation limit if
you are modeling a land-based unit with your own emission factors; or the solubility if you are
modeling a surface impoundment.
For chemicals with both a CSF and an RfC, allowable concentrations are calculated based
on both of these health benchmarks, and the final allowable concentration is based on the one
that leads to the lowest, most protective concentration. This is almost always the one based on
the CSF.
Please note that all calculated values on the RESULTS screen will be lost if you return to a
previous screen and make changes.
Industrial Waste - [6. Results: Allowable Chemical Concentrations based on Target Risk]
File Help
Screen 6. Allowable Concentration Results
A. Select Receptor (Screen 6)
Select a single receptor to serve as the focal exposure point for the calculations by
clicking on the option button associated with the receptor of choice. As discussed above in
Section 5.5, you can specify up to five receptors of concern; however, results can only be seen on
the screen for one receptor at a time. Once results are calculated and displayed for one receptor,
you can select another receptor by clicking on one of the other receptor option buttons. You do
not need to enter exposure duration because it is set by IWAIR and will be displayed when you
click on the | CALCULATE | button.
5-30
-------
IWAIR User's Guide Section 5.0
B. Specify Risk Level (Screen 6)
Specify target cancer and noncancer risk levels. As shown in Screen 6, a drop-down box
is used to allow you to select an appropriate risk level (e.g., an HQ of 1 for noncarcinogens or
IE-6 for carcinogens).
C. View or Override Health Benchmarks (Screen 6)
Screen 6 allows you to view the health benchmarks that IWAIR will use in calculating
risk estimates. For each benchmark, the table on the RESULTS screen shows the value and a brief
reference. To see more-complete citations, click on the | FULL CITATIONS | button in the SOURCE AND
JUSTIFICATION box in the upper right corner of the screen.
IWAIR gives you the option of entering your own health benchmarks. If you choose not
to use the IWAIR data, you can enter alternative health benchmarks by opening the drop-down
box in the RFC REF. column of the desired health benchmark and selecting USER-DEFINED, and then
entering a value in the text box for the benchmark. Enter CSFs (per mg/kg-d) in text boxes
located under the CSF heading and RfCs (mg/m3) under the RFC heading. Do not use a reference
dose in the place of a reference concentration. Once you have entered alternative benchmarks,
they are available in future runs, and you may toggle between them and the IWAIR values using
the drop-down reference box.
You must enter a user-defined health benchmark for two chemicals in IWAIR's chemical
database: divalent mercury and 3,4-dimethylphenol. At the time IWAIR was released, no
accepted health benchmarks were available for these chemicals from the hierarchy of sources
used to populate the IWAIR health benchmark database, nor were there data available from these
sources to allow the development of a health benchmark with any confidence. Thus, if you want
to model one of these chemicals, you will have to enter at least one user-defined health
benchmark. See Section 5 of the IWAIR Technical Background Document for further discussion
of how health benchmarks were developed for IWAIR.
D. Enter Source and Justification for User-Specified Values (Screen 6)
If you choose to override the IWAIR-provided benchmarks, you should specify the source
and the justification of the alternative data in the text box. It is important to provide this
documentation as a reference that will allow you or another user to view and understand saved
files at a later date.
E. Direct IWAIR to Calculate Allowable Waste Concentrations (Screen 6)
Click on the | CALCULATE | button to calculate exposure duration, air concentration, and
waste concentration estimates.
5-31
-------
IWAIR User's Guide Section 5.0
F. View Air Concentration (Screen 6)
Air concentration at the selected receptor point is displayed for each chemical identified
as managed. For land application units, IWAIR calculates three different air concentrations,
based on three different underlying emission rates: a 30-year average for residents for
carcinogens, a 7-year average for workers for carcinogens, and a 1-year maximum for residents
or workers exposed to noncarcinogens. Depending on the receptor selected and the chemical,
IWAIR displays the appropriate air concentration. However, for chemicals that are both
carcinogens and noncarcinogens, only the 30- or 7-year average used for the carcinogenic risk
calculation is displayed. To calculate the 1-year maximum used in the noncarcinogenic HQ
calculation, multiply the emission rate shown on the EMISSION RATES screen by the dispersion factor
and then multiply by 1,000,000 (to convert units).
G. View Allowable Waste Concentration (Screen 6)
Waste concentration estimates will be displayed for each chemical of concern. If
CHEMDAT8 emission rates were used in the calculations, the waste phase (aqueous or organic)
that served as the basis for these rates will be displayed to the right of the waste concentration
text boxes.
For chemicals with both a CSF and an RfC, allowable concentrations are calculated based
on both of these health benchmarks, and the final allowable concentration is based on the one
that leads to the lowest, most protective concentration. This is almost always the one based on
the CSF.
When using the IWAIR tool in allowable concentration calculation mode, you need to
remember that the specified target levels are chemical-specific and do not represent total or
cumulative cancer risk levels (i.e., the summation of the chemical-specific risk estimates). If
multiple chemicals of concern are present in the waste, the cumulative cancer risk will likely be
greater than the specific target risk level unless the target risk could not be reached for some or
all of the chemicals. If the target risk is reached for all chemicals, you can estimate the
cumulative risk posed to the receptor of concern by multiplying the number of carcinogens in the
waste by the specified target risk level. For example, if a waste being managed contains five
carcinogens and the single target risk level specified is IE-6, then the cumulative risk posed to
the receptor of concern would be equal to the product of the number of carcinogens in the waste
(5) times the target risk level (IE-6) or 5E-6.
Done. Click the | DONE | button to initiate a new run or save the run that you have just
completed. A dialog box will appear to guide you through starting a new run or saving the
current run.
5-32
-------
IWAIR User's Guide Section 6.0
6.0 Example Calculations
With IWAIR, you can calculate estimates of cancer and noncancer inhalation risk or
estimates of allowable waste concentration from a specified target risk level. The following
example calculations demonstrate how IWAIR calculates risk or allowable concentration from
emission rates and dispersion factors, using the equations presented in Section 6 of the IWAIR
Technical Background Document, "Calculation of Risk/Hazard Quotient or Allowable Waste
Concentration." You may either use IWAIR-calculated emission rates and dispersion factors or
enter your own values; these example calculations do not cover how IWAIR calculates emission
rates and dispersion factors.
The example calculations are based on a hypothetical exposure situation with the
following conditions:
• The WMU modeled is a landfill.
• The waste managed in the landfill contains the carcinogen hexachlorobenzene and
the noncarcinogen acrolein.
• The emission rates and dispersion factors are IWAIR-calculated values, not user-
override values.
• The exposed individual is a resident living 25 meters from the edge of the unit.
Additional inputs used for the emission and dispersion modeling are summarized in Table 6-1.
6.1 Calculation of Risk and Hazard Quotient
To calculate risk from a specified chemical to a specified receptor, IWAIR uses the
following steps:
1. Calculate emission rates from your inputs or use the emission rates that you
entered; the emission rates are chemical-specific and, if calculated by IWAIR,
depend on the waste concentrations that you entered.
2. Calculate dispersion factors from your inputs or use your entered dispersion
factors; the dispersion factors are receptor-specific.
3. Calculate air concentrations from emission rates and dispersion factors; the air
concentrations are chemical- and receptor-specific.
-------
IWAIR User's Guide
Section 6.0
Table 6-1. Inputs Used for Example Calculation: Landfill
Parameter
Method, Met. Station, WMU Parameters
Meteorological Station
WMU Type
Example Calculation Value
Huntington, WV
Landfill
Wastes Managed Parameters
Chemicals
Concentration (mg/kg)
Waste Management Unit Parameters
Temperature (°C)
Wind speed (m/s)
Total porosity (volume fraction)
Air porosity (volume fraction)
Biodegradation
WMU operating life (yr)
WMU area (m2)
WMU depth (m)
Number of cells
Annual waste quantity (Mg/y)
Waste bulk density (g/cm3)
Hexachlorobenzene, Acrolein
Hexachlorobenzene: 10
Acrolein: 3
13.12 (met station default)
3.179 (met station default)
0.5 (default)
0.25 (default)
Off (default)
30
10,000
2
25
500
1.2 (default)
Receptor Parameters
Receptor type
Receptor distance (m)
Resident
25
6-2
-------
IWAIR User 's Guide Section 6. 0
4. Calculate risks or HQs from air concentrations and, for carcinogens, exposure
factors.
This example calculation does not cover the calculation of emission rates and dispersion factors
in Steps 1 and 2. Using the inputs shown in Table 6-1, IWAIR calculates an emission rate of
1.56E-8 g/m2-s for hexachlorobenzene, an emission rate of 5.36E-9 g/m2-s for acrolein, and a
dispersion factor of 3.37 [|j,g/m3]/[|j,g/m2-s], which is not chemical-specific (but corresponds to a
receptor at 25 m).
Starting with Step 3, IWAIR calculates air concentration, as follows:
Cairj = (EJ X 1Q6) X DF (6-1)
where
Cgjrj = air concentration of chemical y (|J,g/m3)
EJ = volatile emission rate of chemicaly (g/m2-s)
106 = unit conversion (|j,g/g)
DF = dispersion factor ([|j,g/m3]/[|j,g/m2-s]).
Plugging the values for emission rates and dispersion factor shown above into
Equation 6-1 gives the following air concentration values:
c*h* = 1.56E-8xl06x3.37
= 5.26E-2
Cair,acrolein = 5.36E-9 x 106 x 3.37
= 1.806E-2
In Step 4, for carcinogens, IWAIR uses the calculated air concentration, the exposure
factors, and the CSF to calculate carcinogenic risk, as follows:
C . . x 1(T3 x CSF. x EF 5 IR. x ED.
Risk. = -2^ * x E _! 1 (6_2)
J AT x 365 i"! BW. v '
where
Riskj = individual risk for chemicaly (unitless)
6-3
-------
IWAIR User's Guide
Section 6.0
airj
io
-3 =
ED;
EF
365
AT
BW;
air concentration for chemical j (|J,g/m3) = 5.26E-2 for hexachlorobenzene,
calculated above
unit conversion (mg/|ig)
cancer slope factor for chemical y (per mg/kg-d) =1.6 for hexachlorobezene
index on age group (e.g., <1 yr, 1-5 yrs, 6-11 yrs, 12-19 yrs, Adult)
inhalation rate for age group / (m3/d) - varies by age group, see Table 6-2
exposure duration for age group / (yr) - varies by age group, see Table 6-2
exposure frequency (d/yr) = 350
unit conversion (d/yr)
averaging time (yr) = 70
body weight for age group /' (kg) - varies by age group, see Table 6-2.
Table 6-2. Parameter Values Used in Estimating Time-Weighted-Average Exposure
Age Range
Child < 1 year
Child 1-5 years
Child 6-11 years
Child 12- 18 years
Adult
Body Weight
(kg)
9.1
15.4
30.8
57.2
69.1
Inhalation Rate
(nWday)
4.5
7.55
11.75
14.0
13.3
Exposure Duration
(yrs)
1
5
6
7
11
Exposure
Frequency
(d/yr)
350
350
350
350
350
Plugging the air concentration value for hexachlorobenzene and the exposure factors shown
above into Equation 6-2 gives the following carcinogenic risk value:
5.26E-2 x 1Q-3x 1.6x350 f 4.5 x 1 7.55x5 11.75x6 14.0x7 13.3 x
x + + + +
70 x 365
^ 9.1 15.4 30.8 57.2
= 1.04E-5
69.1
In Step 4, for noncarcinogens, IWAIR uses the calculated air concentration and the RfC
to calculate noncarcinogenic risk (HQ), as follows:
-3
HQj =
(6-3)
6-4
-------
IWAIR User 's Guide Section 6. 0
where
= hazard quotient for chemical y (unitless)
Cairj = air concentration for chemical y' (|o,g/m3) = 1.806E-2 for acrolein, calculated
above
10"3 = unit conversion (mg/|j,g)
RfCj = reference concentration for chemical y' (mg/m3) = 2E-5 for acrolein.
Plugging the air concentration value for acrolein into Equation 6-3 above gives the following
HQ, or noncarcinogenic risk value:
Q = 1.806E-2xlQ-3
^acrolein 9 p _ «
= 9.03E-1
6.2 Calculation of Allowable Concentration
To calculate an allowable concentration, IWAIR uses the following steps:
1. Calculate unitized emission rates from your inputs or use your entered unitized
emission rates; the emission rates are chemical-specific and correspond to a waste
concentration of 1 mg/kg or mg/L; if calculated by IWAIR, unitized emission
rates are also specific to waste type (i.e., aqueous- or organic-phase).
2. Calculate dispersion factors from your inputs or use your entered dispersion
factors; the dispersion factors are receptor-specific.
3. Calculate target air concentrations from target risk or HQ, health benchmarks,
and, for carcinogens, exposure factors; the air concentrations are chemical- and
receptor-specific.
4. Calculate waste concentrations from air concentrations, dispersion factors, and
unitized emission rates, for aqueous- and organic-phase wastes.
5. Choose an allowable concentration from the waste concentrations calculated for
aqueous- and organic-phase wastes.
This example calculation does not cover the calculation of unitized emission rates and dispersion
factors in Steps 1 and 2. Using the inputs shown in Table 6-1, IWAIR calculates the unitized
emission rates for aqueous and organic phases for hexachlorobenzene and acrolein, shown in
Table 6-3, and a dispersion factor of 3.37 [|j,g/m3]/[|j,g/m2-s], which is not chemical-specific.
These will be used in Step 4.
6-5
-------
IWAIR User's Guide
Section 6.0
Table 6-3. Unitized Emission Rates for Allowable Concentration
Mode Example Calculation ([g/m2-s]/[mg/kg])
Chemical
Hexachl orob enzene
Acrolein
Aqueous-phase
1.56E-9
1.79E-9
Organic-phase
1.12E-13
7.28E-10
Starting with Step 3, IWAIR calculates target air concentrations by solving Equations 6-2 and 6-3
above for air concentration. For carcinogens,
airj
isk x AT x 365
10
-3
5
E
x
(6-4)
BW;
Plugging a target risk value of IE-5 into Equation 6-4 gives the following air concentration:
air.hcb
lE-Sx 70x365
10-* x 1.6x350 x
( A*v1 TZ**S.
4.5x1 + /.:>:> x:j
( 9.1 15.4
= 5.03E-2
11.75x6 14.0x7
30.8 57.2
+ 13.3 x 11 1
69.1 )
For noncarcinogens,
Cairj
(6-5)
Plugging a target HQ of 1 into Equation 6-5 gives the following air concentration:
Cair,j = 1X
= 2E-2
In Step 4, IWAIR uses an equation comparable to Equation 6-1 to relate target air
concentration to waste concentration. However, this equation must be adapted to reflect the use
of a unitized emission rate associated with a waste concentration of 1 mg/kg. The emission rate,
Ej, is replaced by Cwaste xEjimttized, where Cwaste is waste concentration in mg/kg and Ejimdtimd is the
unitized emission rate for chemical y in [g/m2-s]/[mg/kg]. This new equation, which assumes that
emissions are linear with waste concentration, is as follows:
6-6
-------
IWAIR User 's Guide Section 6. 0
Cai, = (C^te^un* X ^ X DF (6-6)
where
Cair = air concentration (|j,g/m3)
CWaste = waste concentration (mg/kg)
Eunit = normalized volatile emission rate of constituent ([g/m2-s]/[mg/kg])
106 = unit conversion (|j,g/g)
DF = dispersion factor ([|j,g/m3]/[|j,g/m2-s]).
Equation 6-6 may be solved for waste concentration, as follows:
_ air
IWAIR uses this equation with both an aqueous-phase emission rate and an organic-phase
emission rate, to estimate an aqueous-phase waste concentration and an organic-phase waste
concentration.
For hexachlorobenzene in an aqueous-phase waste, plugging the air concentration
calculated above, the unitized emission rate for aqueous-phase waste shown in Table 6-3, and the
dispersion factor shown earlier into Equation 6-7 gives the following waste concentration:
5.03E-2
1.56E-9 x 106 x 3.37
= 9.57
For hexachlorobenzene in an organic-phase waste, plugging the air concentration
calculated above, the unitized emission rate for organic-phase waste shown in Table 6-3, and the
dispersion factor shown earlier into Equation 6-7 gives the following waste concentration:
5.03E-2
waste
1.12E-13 x 106 x 3.37
= 1.33E+5
In Step 5, IWAIR then examines these waste concentrations to ensure that they do not
exceed physical limits (i.e., soil saturation concentration for aqueous-phase wastes and 1E+6
mg/kg for organic-phase wastes). If either waste concentration exceeds the applicable limit, it is
6-7
-------
IWAIR User 's Guide Section 6. 0
discarded.1 If both values are possible, IWAIR selects the lower of the two as the allowable
concentration.
The soil saturation concentration for hexachlorobenzene, given the inputs in Table 6-1, is
26 mg/kg. Because the aqueous-phase concentration for hexachlorobenzene calculated above
(Cwaste = 9.57) does not exceed 26 mg/kg, it is possible and is not discarded. Similarly, the
organic-phase concentration does not exceed 1E+6 mg/kg, and is therefore possible and not
discarded. Since both aqueous-phase and organic-phase concentrations are possible, IWAIR
selects the lower of the two as the allowable concentration. In this case, the aqueous-phase waste
value is lower for the target risk of IE- 5; consequently, the allowable concentration for
hexachlorobenzene is 9.57 mg/kg, based on an aqueous-phase waste.
The calculations for Steps 4 and 5 are similar for acrolein. In an aqueous-phase waste,
plugging the air concentration calculated above, the unitized emission rate for aqueous-phase
waste shown in Table 6-3, and the dispersion factor shown earlier into Equation 6-7 gives the
following waste concentration:
2E-2
1.79E-9 x 106 x 3.37
= 3.32
For acrolein in an organic-phase waste, plugging the air concentration calculated above,
the unitized emission rate for organic-phase waste shown in Table 6-3, and the dispersion factor
shown earlier into Equation 6-7 gives the following waste concentration:
C = 2E-2
waste 7.28E-10 x 106 x 3.37
= 8.15
The soil saturation concentration for acrolein, given the inputs in Table 6-1, is about
45,700 mg/kg. Because the calculated aqueous-phase concentration for acrolein is below this
level, the value is possible and is not discarded.
Similarly, the organic-phase concentration does not exceed 1E+6 mg/kg and is therefore
possible and not discarded. Since both aqueous-phase and organic-phase concentrations are
possible, IWAIR selects the lower of the two as the allowable concentration. In this case, the
aqueous-phase waste value is lower. Thus, for a target HQ of 1, the allowable concentration of
acrolein is 3.32 mg/kg, based on an aqueous-phase waste.
1 If they are both discarded, the soil saturation limit or 1E+6 is used, whichever results in the greatest risk.
-------
IWAIR User's Guide Section 7.0
7.0 References
Shroeder, K., R. Clickner, andE. Miller. 1987. Screening Survey of Industrial Subtitle D
Establishments. Draft Final Report. Westat, Inc., Rockville, MD., for U.S. EPA Office of
Solid Waste. EPA Contract 68-01-7359. December.
U.S. EPA (Environmental Protection Agency). 1991. Hazardous Waste TSDF—Background
Information for Proposed Air Emissions Standards. EPA-450/3-89-023a. Office of Air
Quality Planning and Standards, Research Triangle Park, NC. Pp. C-19-C-30.
U.S. EPA (Environmental Protection Agency). 1993. Guidance on Air Quality Models
(Revised). EPA/450/2-78-027R. Office of Air Quality Planning and Standards, Research
Triangle Park, NC. February.
U.S. EPA (Environmental Protection Agency). 1995. User's Guide for the Industrial Source
Complex (ISC3) Dispersion Models. EPA-454/B-95-003a. Office of Air Quality
Planning and Standards, Research Triangle Park, NC.
U.S. EPA (Environmental Protection Agency). 1997a. Exposure Factors Handbook. Office of
Research and Development, National Center for Environmental Assessment.
U.S. EPA (Environmental Protection Agency). 1997b. Health Effects Assessment Summary
Tables (HEAST). EPA-540-R-97-036. FY 1997 Update.
U.S. EPA (Environmental Protection Agency). 2001. Integrated Risk Information System
(IRIS). National Center for Environmental Assessment, Office of Research and
Development, Washington, DC. Available online at http://www.epa.gov/iris/ Office of
Solid Waste and Emergency Response, Washington, DC.
7-1
-------
-------
Appendix A
Considering Risks from Indirect Pathways
-------
-------
IWAIR User's Guide
Appendix A
Appendix A
Considering Risks from Indirect Pathways
A. 1 What are "Indirect Risks" ?
Direct Pathways: An individual is directly exposed to
the contaminated medium, such as air or
groundwater, into which the chemical was released.
Indirect Pathways: An individual is indirectly
exposed when a contaminant that is released into one
medium (for example, air), is subsequently
transported to other media, such as water, soil, or
food, to which the individual comes in contact.
IWAIR assesses exposures by direct
inhalation of a contaminant. It is possible,
however, that environmental contaminants
can be transferred to other media resulting in
an indirect exposure to the pollutant. The
purpose of this section is to provide risk
assessors with information on health risks that
may result from volatile emissions other than
from the inhalation pathway. An indirect
pathway of exposure is when a contaminant
that is released into one medium (for
example, air) is subsequently transported to other media, such as water, soil, or food, to which a
receptor is exposed. For example, chemical vapors that are released from a WMU and
transported to an adjacent agricultural field may diffuse into vegetation, deposit on vegetation, or
may be taken up by vegetation from the soil. Individuals who subsequently eat the produce from
that field may be exposed to contaminants in their diet. Additional indirect exposures can occur
through the ingestion of contaminated fish, or animal products, such as milk, beef, pork, poultry,
and eggs.
Figure A-l shows these pathways graphically. The arrows indicate the flow of pollutants
through the pathways. Pollutants are released from a source, dispersed through the air, and
deposited on crops, pastures, soil, and surface water. From there, they may be taken up into
plants or animal tissues. Humans may then be exposed by ingesting soil (through hand-to-mouth
contact), ingesting plant products, or ingesting animal products (including fish). Although not
shown in Figure A-l, humans may also ingest groundwater and surface water as drinking water
sources. Groundwater exposures are modeled by the Industrial Waste Management Evaluation
Model (IWEM), and surface water sources of drinking water are presumed to be treated to
remove contaminants.
A-3
-------
IWAIR User's Guide
Appendix A
Figure A-l. Indirect exposure pathways.
A.2 Determining When Indirect Pathways May Be Important
There are two key factors a facility manager should consider when determining the need
to assess the human health risk from indirect pathways of exposure. First, only certain land uses
near a WMU may pose potential risks through indirect exposure pathways. Second, only certain
chemicals may have properties that favor indirect pathways. These two criteria are explained in
the following paragraphs.
A.2.1 Land Use
As described above, indirect exposures can occur when a vapor-phase constituent in the
air is transported into surface water or taken up by produce or by animal products (via feed plants
or surface water). However, these pathways are unlikely to be of concern unless the land use
near the site includes one or more of the following:
• Residential home-gardening
• Agriculture (including production of produce and animal products for human
consumption)
• Farms that grow feed for animals
A-4
-------
IWAIR User's Guide Appendix A
• Recreational fishing
• Recreational hunting areas.
A.2.2 Chemical Properties
In addition to land use, the chemical properties of the constituents in the waste are
important in determining whether indirect pathways are of potential concern. Some chemicals
exhibit properties that tend to favor indirect pathways, while others do not, or do so to a lesser
extent. The chemical properties of interest are those that reflect the tendency for a chemical to be
persistent in the environment, bioaccumulate in plants or animals, or be toxic when ingested.1 A
facility manager should consider these properties when determining whether an assessment of
indirect pathways may be necessary for the WMU. The following subsections provide a brief
description of some of the chemical properties that can be used to predict a constituent's
persistence, bioaccumulation potential, and toxicity.
Persistence
A chemical's persistence refers to how long the chemical remains in the environment
without being chemically or biologically broken down or altered. A chemical considered to be
highly persistent remains in the environment for a relatively long period of time, although it may
move through different media (e.g., from soil to water to sediment). Because persistent
chemicals remain in the environment, they can accumulate in environmental media and/or plant
and animal tissue. As a result, the temporal window for exposure through both direct and
indirect pathways may be extended, and the likelihood of exposure will increase. Persistence is
frequently expressed in terms of half-life. For example, if a chemical has a half-life of 2 days, it
will take 2 days for a given quantity of the chemical to be reduced by one-half due to chemical
and biological processes. The longer the half-life, the more persistent the chemical. A related
chemical property is degradation rate, which is inversely related to half-life. Thus, the lower the
degradation rate, the more persistent the chemical. Data on soil biodegradation rates are
presented for the IWAIR chemicals in Appendix B of the IWAIR Technical Background
Document; this property may be used as a general indicator of persistence potential.
Bioaccumulation Potential
Bioaccumulation potential refers to a chemical's tendency to accumulate in plants and
animals. For example, plants may accumulate chemicals from the soil through their roots. Some
of these chemicals are transformed or combined with others and used by the plant; others are
simply eliminated; and others accumulate in the plant roots, leaves, or edible parts of the plant.
Animals also bioaccumulate certain chemicals in different tissues or organs. For chemicals that
1 The tendency of chemical constituents to be persistent and bioaccumulate are a function of both the
chemical/physical attributes of the chemical (e.g., Kow) and the environmental setting (such as the physical
characteristics of the system, e.g., dissolved organic carbon, soil pH; or the biology of organisms that inhabit the
system, e.g., crops, fish species); however, it is convenient to think of persistence and bioaccumulation potential as
intrinsic properties when considering indirect exposure pathways.
A-5
-------
IWAIR User's Guide
Appendix A
bioaccumulate, the concentration in the plants and animals can be higher than the concentration
in the environment. As a result, a human who eats the plant or animal may be exposed to a
higher concentration in the food than in the contaminated medium.2 Bioaccumulation potential
may be expressed as a bioaccumulation factor (BAF) or a bioconcentration factor (BCF); these
factors express the relationship between the concentration in biota and the concentration in the
environmental medium. Bioaccumulation potential may also be expressed as a biotransfer factor
for animal products, representing the relationship between the exposure concentration and the
mass of contaminated plants ingested daily.
Chemicals that tend to accumulate in
plants and animal tissues often have a
characteristically high affinity for lipids (fats).
This tendency is reflected by the octanol-
water partition coefficient (Kow),3 a laboratory
measurement of the attraction of a chemical
to water versus its attraction to lipids (fats).
In these experiments, octanol is used as a
surrogate for lipids. Because chemicals with
higher Kow values have been shown to have a
greater tendency to accumulate in the fatty
tissue of animals, the BAF and BCF are
generally accepted as useful predictors of
bioaccumulation potential (see text box for
definitions and examples of other parameters
that are often used to evaluate indirect
exposures through the ingestion of produce
and animal products). Some chemicals with
high Kow values, such as polycyclic aromatic
hydrocarbons (PAHs), do not accumulate
appreciably in animals that have the capacity
to metabolize the chemical and eliminate it
from their systems. Moreover, this strong
affinity for lipids also means that the
chemical has a strong affinity for organic
carbon in soil and surface water. Chemical
contaminants that are strongly sorbed to the
organic component in soil may not be readily
taken up by plants. For example, dioxin is
poorly taken up from the soil by virtually all
species of plants that have been tested.
Parameters Used to Evaluate Indirect Exposures
BCF: Bioconcentration Factor for Fish. Defined as
the ratio of chemical concentration in the fish to the
concentration in the surface water. Fish are exposed
only to contaminated water.
BAF: Bioaccumulation Factor for Fish. Defined as
the ratio of the chemical concentration in fish to the
concentration in the surface water. Fish are exposed
to contaminated water and plants/prey.
BSAF: Biota-Sediment Accumulation Factor for
Fish. Generally applied only to highly hydrophobic
organic chemicals, and defined as the ratio of the
lipid-normalized concentration in fish to the organic
carbon-normalized concentration in surface sediment.
Fish are exposed to contaminated pore water,
sediment, and plants/prey.
Br: Plant-Soil Bioconcentration Factor. Defined as
the ratio between the chemical concentration in the
plant and the concentration in soil. It varies by plant
group (e.g., root vegetables, aboveground
vegetables).
Bv: Air-Plant Bioconcentration Factor. Defined as
the mass-based ratio between the chemical
concentration in the plant and the vapor-phase
chemical concentration in the air. It is varies by plant
group (e.g., leafy vegetables, forage).
Ba: Plant-Animal Biotransfer Factor. Defined as the
ratio between the chemical concentration in the
animal tissue and the amount of contaminant ingested
per day. It varies by type of animal tissue (e.g., beef,
milk).
Even though the concentration in food may not be significantly higher than in the environmental media,
the consumption rate of produce and meat/dairy products may lead to a substantial exposure to contaminants.
3 Because octanol-water coefficients can span many orders of magnitude, they are normally discussed in
terms of their log values (log Kow).
A-6
-------
IWAIR User's Guide Appendix A
Consequently, the use of chemical properties should be supplemented with information from
field studies to determine whether the chemical is of potential concern through indirect exposure
pathways. Data on log Kow are presented for the IWAIR chemicals in Appendix B of the IWAIR
Technical Background Document, they may be used as a first-cut indicator of bioaccumulation
potential. As a general rule, chemicals with relatively high Kow values tend to accumulate in
plants and animals to a greater extent than chemicals with relatively low Kow values.
Toxicity
The toxicity of chemicals to humans depends on the route of exposure—inhalation or
ingestion. IWAIR contains health benchmarks for inhalation exposures. However, the indirect
pathways discussed here refer to ingestion exposures. Therefore, even if a chemical is released
into the air and tends to bioaccumulate in plant or animal products, if it is not very toxic by the
ingestion pathway, then indirect pathways will be of less concern. Two benchmarks are used to
predict the toxicity of a contaminant that is ingested: the cancer slope factor (CSF, which
measures the tendency of a chemical to cause cancer) and the reference dose (RfD, which
provides a threshold below which a chemical is unlikely to result in adverse, noncancer health
effects). The CSF is a measure of carcinogenic potency; consequently, a larger value indicates
greater toxicity. However, the RfD is a threshold at which adverse effects are not expected;
therefore, a smaller value indicates greater toxicity.
Oral toxicity benchmarks are not used in IWAIR; therefore, for convenience, the oral
toxicity benchmarks (oral CSF and RfD) are presented for the IWAIR chemicals in Table A-l.
A.3 Additional Information
Indirect risk assessments are often site-specific, require a significant amount of
information about the area surrounding the WMU, and can be complex depending on the
chemicals of concern. However, indirect pathways should not be overlooked as a potential
source of risk if the chemical properties and surrounding land uses suggest potential risks
through indirect exposures.
If it appears that indirect pathways may be of concern, Methodology for Assessing Health
Risks Associated with Multiple Pathways of Exposure to Combustor Emissions (U.S. EPA,
1998b) presents guidance developed by the Agency for conducting indirect risk assessments for
most chemicals. This document can be used to determine whether further assessment of indirect
pathways is needed, and, if so, how to conduct such an assessment. For dioxin-like compounds,
indirect pathways are evaluated somewhat differently; see U.S. EPA (2000a), Exposure and
Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related
Compounds. Part I: Estimating Exposure to Dioxin-Like Compounds.
A-7
-------
IWAIR User's Guide
Appendix A
Table A-l. Oral Health Benchmarks for IWAIR Chemicals
IWAIR Constituent Name
CASRN
RfD RfD CSFo (per CSFo
(mg/kg-d) Source mg/kg-d) Source Comment
1,1,1,2-Tetrachloroethane 630-20-6
1,1,1-Trichloroethane 71-55-6
1,1,2,2-Tetrachloroethane 79-34-5
l,l,2-Trichloro-l,2,2-trifluoroethane 76-13-1
1,1,2-Trichloroethane 79-00-5
1,1 -Dichloroethylene 75-35-4
1,2,4-Trichlorobenzene 120-82-1
l,2-Dibromo-3-chloropropane 96-12-8
1,2-Dichloroethane 107-06-2
3.0E-02 IRIS 2.6E-02 IRIS
2.8E-01 SF
6.0E-02 SF 2.0E-01 IRIS
3.0E+01 IRIS
4.0E-03 IRIS 5.7E-02 IRIS
9.0E-03 IRIS 6.0E-01 IRIS
l.OE-02 IRIS
1.4E+00 HEAST intermediate MRL
available
9.1E-02 IRIS intermediate MRL
available
1 ,2-Dichloropropane
1 ,2-Diphenylhydrazine
1,2-Epoxybutane
1,3 -Butadiene
1,4-Dioxane
2,3,7,8-TCDD
2,4-Dinitrotoluene
2-Chlorophenol
2-Ethoxyethanol
2-Ethoxyethanol acetate
2-Methoxyethanol
2-Methoxyethanol acetate
2-Nitropropane
3 ,4-Dimethylphenol
3 -Methylcholanthrene
7, 12-Dimethylbenz[a]anthracene
78-87-5 9.0E-02 ATSDR 6.8E-02 HEAST
122-66-7 8.0E-01 IRIS
106-88-7
106-99-0
123-91-1 1.1E-02 IRIS
1746-01-6 l.OE-09 ATSDR 1.5E+05 HEAST
121-14-2 2.0E-03 IRIS 6.8E-01 IRIS CSFo is for 2,4-72,6-
mixture
95-57-8 5.0E-03 IRIS
110-80-5 4.0E-01 HEAST
111-15-9 3.0E-01 HEAST
109-86-4 l.OE-03 HEAST
110-49-6 2.0E-03 HEAST
79-46-9
95-65-8 l.OE-03 IRIS
56-49-5
57-97-6
(continued)
A-8
-------
IWAIR User's Guide
Appendix A
Table A-l. (continued)
IWAIR Constituent Name
Acetaldehyde
Acetone
Acetonitrile
Acrolein
Acrylamide
Acrylic acid
Acrylonitrile
Allyl chloride
Aniline
Benzene
Benzidine
Benzo(a)pyrene
Bromodichloromethane
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chlorodibromomethane
Chloroform
Chloroprene
cis- 1 , 3 -Dichloropropylene
CASRN
75-07-0
67-64-1
75-05-8
107-02-8
79-06-1
79-10-7
107-13-1
107-05-1
62-53-3
71-43-2
92-87-5
50-32-8
75-27-4
75-15-0
56-23-5
108-90-7
124-48-1
67-66-3
126-99-8
10061-01-5
RfD
(mg/kg-d)
l.OE-01
2.0E-02
2.0E-04
5.0E-01
l.OE-03
3.0E-03
2.0E-02
l.OE-01
7.0E-04
2.0E-02
2.0E-02
l.OE-02
2.0E-02
3.0E-02
RfD CSFo(per CSFo
Source mg/kg-d) Source Comment
IRIS
HEAST
IRIS 4.5E+00 IRIS
IRIS
HEAST 5.4E-01 IRIS
5.7E-03 IRIS
5.5E-02 IRIS upper range estimate
used for CSFo
IRIS 2.3E+02 IRIS
7.3E+00 IRIS
IRIS 6.2E-02 IRIS
IRIS
IRIS 1.3E-01 IRIS
IRIS
IRIS 8.4E-02 IRIS
IRIS
HEAST
IRIS l.OE-01 IRIS RfD & CSFo are for
Cresols (total)
Cumene
Cyclohexanol
Dichlorodifluoromethane
Epichlorohydrin
1319-77-3 5.0E-02 surr
98-82-8 l.OE-01 IRIS
108-93-0 1.7E-05 solvents
75-71-8 2.0E-01 IRIS
106-89-8 2.0E-03 HEAST 9.9E-03
1,3 -dichloropropene
RfD is for m-cresol
IRIS
(continued)
A-9
-------
IWAIR User's Guide
Appendix A
Table A-l. (continued)
IWAIR Constituent Name
Ethylbenzene
Ethylene dibromide
Ethylene glycol
Ethylene oxide
Formaldehyde
Furfural
Hexachloro- 1 , 3 -butadiene
Hexachlorobenzene
Hexachlorocyclopentadiene
Hexachloroethane
Isophorone
Mercury
Methanol
Methyl bromide
Methyl chloride
Methyl ethyl ketone
Methyl isobutyl ketone
Methyl methacrylate
Methyl tert-butyl ether
Methylene chloride
N,N-Dimethyl formamide
Naphthalene
n-Hexane
Nitrobenzene
N-Nitrosodiethylamine
N-Nitrosodi-n-butylamine
CASRN
100-41-4
106-93-4
107-21-1
75-21-8
50-00-0
98-01-1
87-68-3
118-74-1
77-47-4
67-72-1
78-59-1
7439-97-6
67-56-1
74-83-9
74-87-3
78-93-3
108-10-1
80-62-6
1634-04-4
75-09-2
68-12-2
91-20-3
110-54-3
98-95-3
55-18-5
924-16-3
RfD
(mg/kg-d)
l.OE-01
2.0E+00
2.0E-01
3.0E-03
3.0E-04
8.0E-04
6.0E-03
l.OE-03
2.0E-01
l.OE-04
5.0E-01
1.4E-03
6.0E-01
8.0E-02
1.4E+00
6.0E-02
l.OE-01
2.0E-02
1.1E+01
5.0E-04
RfD CSFo(per CSFo
Source mg/kg-d) Source Comment
IRIS
8.5E+01 IRIS
IRIS
l.OE+00 HEAST
IRIS
IRIS
SF 7.8E-02 IRIS
IRIS 1.6E+00 IRIS
IRIS
IRIS 1.4E-02 IRIS
IRIS 9.5E-04 IRIS
surr RfD is for methyl
mercury
IRIS
IRIS
1.3E-02 HEAST
IRIS
HEAST
IRIS
intermediate MRL
available
IRIS 7.5E-03 IRIS
HEAST
IRIS
SF
IRIS
1.5E+02 IRIS
5.4E+00 IRIS
(continued)
A-10
-------
IWAIR User's Guide
Appendix A
Table A-l. (continued)
IWAIR Constituent Name
N-Nitrosopyrrolidine
o-Dichlorobenzene
o-Toluidine
p-Dichlorobenzene
Phenol
Phthalic anhydride
Propylene oxide
Pyridine
Styrene
Tetrachloroethylene
Toluene
trans- 1 , 3 -Dichloropropylene
Tribromomethane
Trichloroethylene
Trichlorofluoromethane
Triethylamine
Vinyl acetate
Vinyl chloride
Xylenes
RfD RfD CSFo(per CSFo
CASRN (mg/kg-d) Source mg/kg-d) Source
930-55-2 2.1E+00 IRIS
95-50-1 9.0E-02 IRIS
95-53-4 2.4E-01 HEAST
106-46-7 2.4E-02 HEAST
108-95-2 6.0E-01 IRIS
85-44-9 2.0E+00 IRIS
75-56-9 2.4E-01 IRIS
110-86-1 l.OE-03 IRIS
100-42-5 2.0E-01 IRIS
127-18-4 l.OE-02 IRIS 5.2E-02 HAD
108-88-3 2.0E-01 IRIS
10061-02-6 3.0E-02 IRIS l.OE-01 IRIS
75-25-2 2.0E-02 IRIS 7.9E-03 IRIS
79-01-6 1.1E-02 HAD
75-69-4 3.0E-01 IRIS
121-44-8
108-05-4 l.OE+00 HEAST
75-01-4 3.0E-03 IRIS 7.2E-01 IRIS
1330-20-7 2.0E+00 IRIS
Comment
intermediate MRL
available
RfD & CSFo are for
1 ,3 -dichloropropene
CSFo is for
continuous adult
exposure
a Sources:
ATSDR = ATSDR oral minimal risk levels (ATSDR, 200 1)
IRIS = Integrated Risk Information System (U.S. EPA, 200 1)
HEAST = Health Effects Assessment Summary Tables (U.S. EPA, 1997a)
HAD = Health Assessment Document (U.S. EPA, 1986, 1987)
SF = Superfund Risk Issue Paper (U.S. EPA, 1998c, 1999a, 1999b, 2000b)
solvents = 63 FR 64371-0402 (U.S. EPA, 1998a)
surr = surrogate
A-ll
-------
IWAIR User 's Guide Appendix A
Finally, as noted above, various chemical properties indicative of the potential for indirect
pathway concern are presented in the IWAIR Technical Background Document for IWAIR
chemicals. For other chemicals, the following sources may be useful:
• EPA' s Superfund Chemical Data Matrix (SCDM) (U. S. EPA, 1 997b)
• The Merck Index (Budavari, 1996)
• The National Library of Medicine's Hazardous Substances Databank (HSDB),
available on TOXNET (U.S. NLM, 2001)
• Syracuse Research Corporation' s CHEMF ATE database (SRC, 1 999)
• CambridgeSoft.com's ChemFinder database (CambridgeSoft, 2001)
• Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological
Profiles (ATSDR, 2001)
• EPA's Dioxin Reassessment (U.S. EPA, 2000a) — for dioxins only
Half-life
• Howard etal. (1991)
Toxicity (in order of preference)
• Integrated Risk Information System (IRIS) (U.S. EPA, 2001)
• Superfund Technical Support Center Provisional Benchmarks (U.S. EPA, 1998c,
1999a, 1999b, 2000b)
• Health Effects Assessment Summary Tables (HEAST) (U.S. EPA, 1997a)
• Agency for Toxic Substances and Disease Registry oral minimal risk levels
(MRLs) (ATSDR, 2001)
• California Environmental Protection Agency (CalEPA) cancer potency factors
(CalEPA, 1999)
• EPA health assessment documents (U.S. EPA, 1986, 1987, 1998a).
A-12
-------
IWAIR User's Guide Appendix A
A.4 References
ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Minimal Risk Levels
(MRLs)for Hazardous Substances. http://atsdrl.atsdr.cdc.gov:8080/mrls.html
Budavari, S. (Ed.). 1996. The Merck Index, An Encyclopedia of Chemicals, Drugs, and
Biologicals. 12th Edition. Merck & Co. Inc., Rahway, NJ.
CalEPA (California Environmental Protection Agency). 1999. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part II. Technical Support Document for Describing
Available Cancer Potency Factors. Office of Environmental Health Hazard Assessment,
Berkeley, CA. Available online at http://www.oehha.org/scientific/hsca2.htm.
CambridgeSoft Corporation. 2001. ChemFinder.com database and internet searching.
http://chemfmder.cambridgesoft.com. Accessed July 2001.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, E.M. Michalenko, and H.T. Printup
(Ed.). 1991. Handbook of Environmental Degradation Rates. Lewi s Publi shers,
Chelsea, MI.
Syracuse Research Corporation (SRC). 1999. CHEMFATE Chemical Search, Environmental
Science Center, Syracuse, NY. http://esc.syrres.com/efdb/Chemfate.htm. Accessed July
2001.
U.S. EPA (Environmental Protection Agency). 1986. Addendum to the Health Assessment
Document for Tetrachloroethylene (Perchloroethylene). Updated Carcinogenicity
Assessment for Tetrachloroethylene (Perchloroethylene, PERC, PCE). External Review
Draft. EPA/600/8-82-005FA. Office of Health and Environmental Assessment, Office of
Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1987. Addendum to the Health Assessment
Document for Trichloroethylene. Updated Carcinogenicity Assessment for
Trichloroethylene. External Review Draft. EPA/600/8-82-006FA. Office of Health and
Environmental Assessment, Office of Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1997a. Health Effects Assessment Summary
Tables (HEAST). EPA-540-R-97-036. FY 1997 Update.
U.S. EPA (Environmental Protection Agency). 1997b. Superfund Chemical Data Matrix
(SCDM). Office of Emergency and Remedial Response. Web site at
http://www.epa.gov/oerrpage/superfund/resources/scdm/index.htm. June.
U.S. EPA (Environmental Protection Agency). 1998a. Hazardous waste management system;
identification and listing of hazardous waste; solvents; final rule. Federal Register
63 FR 64371-402.
A-13
-------
IWAIR User's Guide Appendix A
U.S. EPA (Environmental Protection Agency). 1998b. Methodology for Assessing Health Risks
Associated with Multiple Pathways of Exposure to Combustor Emissions. Update to
EPA/600/6-90/003 Methodology for Assessing Health Risks Associated with Indirect
Exposure to Combustor Emissions. EPA 600/R-98/137. National Center for
Environmental Assessment, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1998c. Risk Assessment Paper for: Evaluation
of the Systemic Toxicity of Hexachlorobutadiene (CASRN 87-68-3) Resulting from Oral
Exposure. 98-009/07-17-98. National Center for Environmental Assessment. Superfund
Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999a. Risk Assessment Issue Paper for:
Derivation of Provisional Oral Chronic RfD and Subchronic RfDsfor 1,1,1-
Trichloroethane (CASRN 71-55-6). 98-025/8-4-99. National Center for Environmental
Assessment. Superfund Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999b. Risk Assessment Paper for: An Updated
Systemic Toxicity Evaluation of n-Hexane (CASRN 110-54-3). 98-019/10-1-99. National
Center for Environmental Assessment. Superfund Technical Support Center, Cincinnati,
OH.
U.S. EPA (Environmental Protection Agency). 2000a. Exposure and Human Health
Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds.
Part I: Estimating Exposure to Dioxin-Like Compounds. Volume 3—Properties,
Environmental Levels, and Background Exposures. Draft Final Report. EPA/600/P-
00/001. Office of Research and Development, Washington, DC. September.
U.S. EPA (Environmental Protection Agency). 2000b. Risk Assessment Paper for: Derivation
of a Provisional RfD for 1,1,2,2-Tetrachloroethane (CASRN 79-34-5). 00-122/12-20-00.
National Center for Environmental Assessment. Superfund Technical Support Center,
Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 2001. Integrated Risk Information System
(IRIS). National Center for Environmental Assessment, Office of Research and
Development, Washington, DC. Available online at http://www.epa.gov/iris/ Office of
Solid Waste and Emergency Response, Washington, DC.
U.S. NLM (National Library of Medicine). 2001. Hazardous Substances Data Bank (HSDB).
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Accessed July 2001.
A-14
-------
Appendix B
Parameter Guidance
-------
-------
IWAIR User's Guide Appendix B
Appendix B
Parameter Guidance
This appendix provides you with guidance on all parameter values needed to run IWAIR.
This guidance covers all parameters that you may enter in text boxes and most selections from
drop-down boxes. It does not include most option buttons, as those are covered in the
operational guidance in Sections 4 and 5. However, a few options are covered here, as well as in
Sections 4 and 5.
This appendix is organized by screen. Some parameters are applicable only to risk mode
or allowable concentration mode; those are so noted.
B.I Method, Met. Station, WMU (Screen 1A)
Most of the options on Screen 1A are covered in the operational guidance in Sections 4
and 5. There are only two parameters for this screen: zip code and latitude/longitude. You will
only need to enter data for one or the other.
Zip Code. This is the 5-digit zip code for the physical location of your facility. IWAIR
uses this zip code to assign the most appropriate meteorological station to your site; therefore,
you should not use the zip code from a mailing address, such as a post office box or a company
headquarters. The zip code database includes zip codes established through 1999. If your
facility has a new zip code that was established more recently, you will get an error message
indicating that it is not a valid zip code, because it is not in IWAIR's database. If this occurs,
you can use your old zip code, use a nearby zip code, or select a meteorological station using
latitude and longitude.
Latitude and Longitude. These are the latitude and longitude coordinates for the
physical location of your facility. At a minimum, the program requires that degrees for latitude
and longitude be entered. If available, the minutes and seconds should be supplied to ensure that
the most appropriate station is selected for a site. Latitude and longitude can be obtained from
most maps of the area where your facility is located.
B-3
-------
IWAIR User's Guide Appendix B
B.2 Wastes Managed and Add/Modify Chemicals (Screens 2A and 2B)
B.2.1 Wastes Managed
Sections 4 and 5 cover the selection of chemicals for your waste. There is only one
parameter to be entered on Screen 2A: waste concentration. This is only needed for risk
calculations.
Waste Concentration (mg/L or mg/kg). This is the concentration of each chemical in
your waste. It should reflect the waste or influent going into your unit, not the concentration
within the unit. For surface impoundments, it should be in mg/L or ppm. For land application
units, landfills, and waste piles, it should be in mg/kg or ppm. This value must be greater than
zero; the sum of all concentrations entered must be less than or equal to one million.
B.2.2 Add/Modify Chemicals (Screen 2B)
The ADD/MODIFY CHEMICALS screen requires you to enter numerous chemical-specific
parameters. These are organized below into chemical identifiers, physical-chemical properties,
and health benchmarks.
B.2.2.1 Chemical Identifiers
Chemical Name. If you are entering a new chemical, you can enter the chemical name
here. If you are modifying or making a new entry for an existing chemical, you will not need to
enter a chemical name; IWAIR will fill it in automatically. Do not add any user designation to
the end of the chemical name you enter—IWAIR will do that automatically. Enter the chemical
name exactly as you would like it to sort and display. For example, if you want 1,2,4-
trichlorobenzene to sort under T instead of 1, enter it as "trichlorobenzene, 1,2,4-".
CAS Number. If you are entering a new chemical, you can enter the Chemical Abstracts
Service (CAS) number here. If you are modifying or making a new entry for an existing
chemical, you will not need to enter a CAS number; IWAIR will fill it in automatically. IWAIR
does not use leading zeros on CAS numbers; therefore, for consistency with the data provided
with IWAIR, it is recommended that you use leading spaces instead of leading zeros for CAS
numbers shorter than the maximum length.
B.2.2.2 Physical-Chemical Properties. Data on many physical-chemical properties can
be obtained from the following sources:
• EPA's Superfund Chemical Data Matrix (SCDM) (U. S. EPA, 1997b),
• The Merck Index (Budavari, 1996),
• The National Library of Medicine's Hazardous Substances Databank (HSDB),
available on TOXNET (U.S. NLM, 2001),
B-4
-------
IWAIR User's Guide Appendix B
• Syracuse Research Corporation's CHEMFATE database (SRC, 1999),
• CambridgeSoft.com's ChemFinder database (CambridgeSoft, 2001), and
• Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological
Profiles (ATSDR, 2001).
In addition, a useful source of data on chemical properties for dioxins is EPA's Dioxin
Reassessment (U.S. EPA, 2000a).
Molecular Weight (g/mol). Molecular weight is used to estimate emissions. Values can
be obtained from the literature, including from the SCDM; HSDB; and CHEMF ATE. This value
must be greater than or equal to 1 g/mol (the molecular weight of a single hydrogen ion). No
maximum limit is enforced. IWAIR has been tested for molecular weights between 1 and 400
g/mol.
Density (g/cm3). IWAIR uses density to determine if chemicals present in organic phase
in surface impoundments are likely to float (if they are less dense than water) or sink (if they are
more dense that water). Unless the value is very near 1 g/cm3 (the density of water), the model is
not sensitive to variations in the value. Values can be obtained from the literature, including
from the SCDM; Merck Index; and HSDB. This value must be greater than zero. No maximum
limit is enforced. IWAIR has been tested for densities between 0.01 and 14 g/cm3.
Vapor Pressure (mmHg). Vapor pressure and the mole fraction in the liquid phase are
used to calculate the constituent's partial vapor pressure. The partial vapor pressure is
subsequently used as the partition coefficient for organic-phase wastes and aqueous-phase wastes
with chemicals present above solubility or saturation limits. Values can be obtained from the
literature, including from the SCDM and HSDB. Vapor pressure may be reported in other units,
such as atmospheres or torr; torr is equivalent to mmHg, but data in atmospheres will need to be
converted. Different vapor pressures may be reported for the same chemical at different
temperatures. For best results, choose a vapor pressure reported at a temperature around
20-25°C. This value must be greater than zero. No maximum limit is enforced. IWAIR has
been tested for vapor pressures between 0 and 5,300 mmHg.
Henry's Law Constant (atm-n^/mol). Henry's law constant reflects the tendency of
chemicals to volatilize from dilute aqueous solutions; it is used as the partition coefficient for
aqueous-phase wastes with chemicals present below solubility or saturation limits. Values can
be obtained from the literature, including from the SCDM; 2000 Dioxin Reassessment (for
dioxins); HSDB; CHEMF ATE; and ChemFinder. If Henry's law constant is not available, it can
be calculated from the chemical's vapor pressure, molecular weight, and solubility using the
following equation (Lyman et al., 1990):
H =
X
uoooJ
-------
IWAIR User 's Guide Appendix B
where
H = Henry' s law constant (atm-m3/mol)
VP = vapor pressure (mmHg)
S = solubility (mg/L)
MW = molecular weight (g/mol)
760 = unit conversion (mmHg/atm)
1000 = unit conversion (L/m3)
1000 = unit conversion (mg/g).
The value for Henry's law constant must be greater than zero. No maximum limit is enforced.
IWAIR has been tested for Henry's law constants between 4E- 1 1 and 1.2 atm-m3/mol-K.
Solubility (mg/L). This is the solubility of the individual chemical in water. Solubility is
used for surface impoundments to identify wastes that may be supersaturated so that emissions
equations may be based on the most appropriate partition coefficient (Henry's law for aqueous-
phase wastes below saturation or solubility limits, and partial vapor pressure for wastes above
saturation or solubility limits and organic-phase wastes). Values can be obtained from the
literature, including from the SCDM; Merck Index; Dioxin Reassessment (for dioxins); HSDB;
and CHEMFATE. This value must be greater than zero and less than or equal to one million.
IWAIR has been tested for solubilities from 1.93E-5 to 1,000,000 mg/L.
Soil Biodegradation Rate (s'1). The soil biodegradation rate is a first-order rate constant
used to estimate soil biodegradation losses in land application units, landfills, and waste piles.
The tendency to biodegrade in soil is often reported as half-life; this is not comparable to
biodegradation rate and should not be used in IWAIR. However, you can calculate the soil
biodegradation rate from the half-life as follows:
k =
tl/2
where
ks = soil biodegradation rate (s"1)
ln(2) = natural log of 2
t1/2 = half-life (s).
An excellent reference for soil biodegradation data (and the one used for all soil biodegradation
rates included with IWAIR) is Howard et al. (1991). This reference provides both high-end and
low-end half-life data for soil biodegradation. The high-end values were used in IWAIR. In
general, half-lives are reported in hours. Values for very short half-lives are given in minutes or
seconds. All values, except the ones already given in seconds, must be converted to seconds
before using the above equation to convert to biodegradation rate. The soil biodegradation rate
may be zero if the chemical does not biodegrade; however, because a zero value would cause
IWAIR to try to divide by zero, IWAIR converts values entered as zero to 1E-20, which results
B-6
-------
IWAIR User's Guide Appendix B
in negligible biodegradation. No maximum limit is enforced. IWAIR has been tested for soil
biodegradation rates from IE-20 to 0.0004 s"1.
Antoine's Constants: A, B, or C. Antoine's constants are used to adjust vapor pressure
and Henry's law constant to ambient temperature. While not explicitly reported with units, they
are intended to adjust vapor pressure in mmHg based on temperature in degrees Celsius. Values
for Antoine's constants are available in Reid et al. (1977). A and B must be greater than or equal
to zero. C may be negative. No maximum limits are enforced. IWAIR has been tested for A
values from 0 to 14; B values from 0 to 5,400; and C values from 0 to 292.
Diffusivity in Water (cnf/s). Diffusivity in water is used to estimate emissions.
Diffusivity in water can be calculated from the chemical's molecular weight and density, using
the following correlation equation based on Water9 (U.S. EPA, 2001c):
» = 0.0001518X
where
Dw = diffusivity in water (cm2/s)
T = temperature (°C)
273.16 = unit conversion (°C to °K)
MW = molecular weight (g/mol)
p = density (g/cm3).
If density is not available, diffusivity in water can be calculated using the following correlation
equation based on U.S. EPA (1987b):
D,= 0.00022 x
The value for diffusivity in water must be greater than zero. No maximum limit is enforced.
IWAIR has been tested for values of diffusivity in water from 5E-6 to 3E-5 cm2/s.
Diffusivity in Air (cnf/s). Diffusivity in air is used to estimate emissions. Diffusivity in
air can be calculated from the chemical's molecular weight and density, using the following
correlation equation based on Water9 (U.S. EPA, 200Ic):
0.00229 X(T +273.16) 1-5xJ0.034 + *MWcor
V V MWy
0.333
B-7
-------
IWAIR User's Guide Appendix B
where
Da = diffusivity in air (cm2/s)
T = temperature (°C)
273.16 = unit conversion (°C to °K)
MW = molecular weight (g/mol)
p = density (g/cm3).
MWcor = molecular weight correlation:
MWOT = (l-0.000015xMW2)
If MWcor is less than 0.4, then MWcor is set to 0.4.
If density is not available, diffusivity in air can be calculated using the following correlation
equation based on U.S. EPA (1987b):
-f-V
= 1.9x1 MW Uj
For dioxins, diffusivity in air can be calculated from the molecular weight using the following
correlation equation based on EPA's Dioxin Reassessment (U.S. EPA, 2000a):
x0-068
Diffusivity in air values must be greater than or equal to zero. No maximum limit is enforced.
IWAIR has been tested for values of diffusivity in air from 0 to 0.25 cm2/s.
Octanol-Water Partition Coefficient (log Kon). Km is used to estimate emissions and to
calculate the soil saturation concentration limit for land application units, landfills, and waste
piles. Because Km can cover an extremely wide range of values, it is typically reported as the log
of Km and should be entered as the log in IWAIR. Values can be obtained from the literature,
including the SCDM. Log Kow is unitless. Log Kow may have negative values, reflecting Km
values less than 1. Due to model limitations, log Kow may not be less than -10 or greater than 10;
IWAIR has been tested for this entire range.
Hydrolysis Constant (s'1). This value, which is used to estimate losses by hydrolysis, is
the hydrolysis rate constant at neutral pH. An excellent source of data on hydrolysis rate
constants (and the one used for all hydrolysis rate constants included with IWAIR) is Kollig
(1993). The hydrolysis constant may be zero if the chemical does not hydrolyze; it cannot be less
than zero. No maximum limit is enforced. IWAIR has been tested for values of hydrolysis
constants from 0 to 22 s"1.
-------
IWAIR User's Guide Appendix B
Kj (L/g-h). Kj is used to estimate biodegradation losses in surface impoundments. There
are very few literature sources for K,. The primary source of data is Coburn et al. (1988). Values
for K! in CHEMDAT8 and IWAIR were taken from this source. If you have rate study data at
very low concentrations, that rate can be used for K,. K, may be zero if the chemical does not
biodegrade; it cannot be less than zero. No maximum limit is enforced. IWAIR has been tested
for values of K, from 0 to 25 L/g-h.
Kmax (mg volatile organics/g-h). Kmax is used to estimate biodegradation losses in surface
impoundments. There are very few literature sources for Kmax. The primary source of data is
Coburn et al. (1988). Values for Kmax in CHEMDAT8 and IWAIR were taken from this source.
If you have rate study data at very high concentrations, that rate can be used forKmax. Kmax may
be zero if the chemical does not biodegrade; it cannot be less than zero. No maximum limit is
enforced. IWAIR has been tested for values of Kmax from 0 to 100 mg VO/g-h.
B.2.2.3 Health Benchmarks
Cancer Slope Factor (CSF) (mg/kg/d)'1. The inhalation CSF is used to evaluate risk for
carcinogens. The CSF is an upper-bound estimate (approximating a 95 percent confidence limit)
of the increased human cancer risk from a lifetime exposure to an agent. Inhalation CSFs are
used in the model for carcinogenic constituents, regardless of the availability of an RfC. If a
value for the inhalation CSF is not available, you should enter "NA" in the CSF field, rather than
zero. IWAIR must have a numeric value for either the inhalation CSF or RfC to calculate risk or
allowable concentration. If a numeric value is entered, it must be greater than zero. No
maximum limit is enforced. IWAIR has been tested for CSF values from 0.00001 to 150,000
(mg/kg/d)-1.
Reference Concentration (RfC) (mg/m3). The RfC is used to evaluate noncancer hazards
posed by inhalation exposures to chemicals. The RfC is an estimate (with uncertainty spanning
perhaps an order of magnitude) of a daily exposure to the human population (including sensitive
subgroups) that is unlikely to pose an appreciable risk of deleterious noncancer effects during an
individual's lifetime. If a value for the RfC is not available, you should enter "NA" in the RfC
field, rather than zero. IWAIR must have a numeric value for either the inhalation CSF or RfC to
calculate risk or allowable concentration. If a numeric value is entered, it must be greater than
zero. No maximum limit is enforced. IWAIR has been tested for RfC values from 0.00001 to
40 mg/m3.
Human health benchmarks contained in databases developed by EPA were used
whenever available. Benchmarks were obtained in the following order of preference:
• Integrated Risk Information System (IRIS) (U.S. EPA, 2001b)
• Superfund Technical Support Center Provisional Benchmarks (U.S. EPA, 1998b,
1999a, 1999b, 2000b)
• Health Effects Assessment Summary Tables (HEAST) (U.S. EPA, 1997a)
B-9
-------
IWAIR User's Guide Appendix B
• Agency for Toxic Substances and Disease Registry (ATSDR) minimal risk levels
(MRLs) (ATSDR, 2001)
• California Environmental Protection Agency (CalEPA) chronic inhalation
reference exposure levels (RELs) and cancer potency factors (CalEPA, 1999a,
1999b, 2000)
• EPA health assessment documents (U.S. EPA, 1986, 1987a, 1998a)
• Various other EPA health benchmark sources.
B.3 WMU Data for CHEMDAT8 (Screens 3A through 3D)
B.3.1 WMU Data for CHEMDAT8 - Surface Impoundment (Screen 3A)
B.3.1.1 Meteorological Station Parameters. These inputs are used only for the
emissions modeling, not the dispersion modeling, which uses hourly meteorological data, not
annual averages. Therefore, changes to these inputs will not affect the dispersion factors.
Wind Speed (m/s). IWAIR uses wind speed to select the most appropriate empirical
emission correlation equation in CHEMDAT8; there are several of these correlations, and each
one applies to a specific range of wind speeds and unit sizes. By default, IWAIR uses the
average annual wind speed from the meteorological station that was assigned to your location.
However, you may wish to override the default if you have site-specific data on wind speed. If
you do override, you should use an overall annual average in all directions, not any measure of
peak wind speed or average only in the prevailing wind direction. Also, wind speed is often
reported in knots or mph. However, for use in IWAIR, wind speed must be converted to m/s.
This value must be greater than zero. No maximum limit is enforced. IWAIR has been tested
for values of wind speed from 0.01 to 100 m/s; however, a realistic range for average annual
wind speed is about 2 to 10 m/s.
Temperature (°C). IWAIR uses temperature to correct various temperature-dependent
chemical properties used in emissions modeling (Henry's law constant and vapor pressure) from
a standard temperature to the ambient temperature. By default, IWAIR uses the average annual
temperature from the meteorological station that was assigned to your location. However, you
may wish to override the default if you have site-specific data on temperature. If you do
override, you should use an annual average temperature. Temperature may be reported in
degrees Fahrenheit (°F); however, for use in IWAIR, temperature must be converted to degrees
Celsius (°C). This value must be greater than or equal to -100°C. No maximum limit is
enforced. IWAIR has been tested for values of temperature from 0 to 50°C.
B.3.1.2 SI Dimensions, Loading Information
Biodegradation (on/off). This option, in conjunction with the ACTIVE BIOMASS input, allows
you to determine what type of biodegradation is modeled for your unit. In biologically active
surface impoundments, two processes occur: growth of biomass, which provides a growing
B-10
-------
IWAIR User's Guide Appendix B
matrix for chemical adsorption and loss through settling, and direct biodegradation of chemical
constituents as the bacteria that compose the biomass consume constituent mass. Direct
biodegradation cannot occur if there is no active biomass. If an impoundment is biologically
active, it may go through a transitional period during which there is active biomass (so
adsorption and settling losses occur) but the biomass is not yet adapted to consume the specific
chemicals present (so direct biodegradation is not occurring). This transitional period will
usually end as the biomass acclimate and adapt to the chemicals present.
Setting biodegradation to I OFF | turns off direct biodegradation. It does not affect
adsorption loss. Setting active biomass to zero turns off biomass growth, so that adsorption
losses are limited to adsorption to inlet solids. Setting active biomass to zero also turns off direct
biodegradation (in fact, if you have set biodegradation |ON I and then set active biomass to zero,
IWAIR will automatically reset the biodegradation option to I OFF |). If you set biodegradation to
I OFF |, IWAIR will remove the default value for active biomass, and you will have to enter a
value (typically zero, but this is not required, and it may be greater than zero if you wish to model
the transitional period before direct biodegradation occurs).
If your impoundment is biologically active, it recommended that you leave
biodegradation set to I ON I (the default). If your impoundment is not biologically active, it is
recommended that you set biodegradation to I OFF | and active biomass to zero.
Operating Life (yr). This parameter is the expected remaining operating life of your unit,
from the time you are modeling until you expect it to be closed. Operating life does not affect
emissions estimates for surface impoundments, which are modeled at steady state. However,
operating life may affect exposure duration. IWAIR uses default exposure durations of 30 years
for residents and 7.2 years for workers. However, proper closure of a surface impoundment
typically ends all exposures. Therefore, if the operating life you specify is less than 30 or 7.2
years, IWAIR caps the exposure duration at the operating life. Values in excess of 30 years will
not affect the results for residents, and values in excess of 7.2 years will not affect the results for
workers. Operating life should be entered in years. This value must be greater than zero. No
maximum limit is enforced. IWAIR has been tested for values of operating life from 0.01 to 100
years.
Depth of Unit (m). This is the average depth of your unit in meters (m). If your unit is
not a constant depth, use the average or most typical depth. If you have depth reported in units
such as feet, you will need to convert them to meters. This value must be greater than zero. No
maximum limit is enforced. IWAIR has been tested for values of depth from 0.01 to 30 m.
Area of Unit (m2). This is the total surface area of your unit in m2. Areas may be
reported in acres or hectares; these values will need to be converted to m2 for use in IWAIR.
This value must be greater than or equal to 81 m2 and less than or equal to 8,090,000 m2; these
are the smallest and largest areas for which IWAIR can interpolate dispersion factors for ground-
level sources. IWAIR has been tested for this full range.
Annual Flow of Waste (m3/yr). This is the total amount of waste that flows through your
impoundment in a year, in m3/yr. Flow is often reported in millions of gallons per day (MGD) or
B-ll
-------
IWAIR User's Guide
Appendix B
other units; you will need to convert to m3/yr for use in IWAIR. This value must be greater than
zero. No maximum limit is enforced. IWAIR has been tested for values of annual flow of waste
from 0.01 to 10,000,000 nrVyr.
B.3.1.3 Aeration Option Information
Type of Aeration. This option allows you to identify whether your impoundment is
aerated and, if so, the specific type of aeration. IWAIR can model no aeration (quiescent),
diffused air aeration, mechanical aeration, and both (diffused air and mechanical).
If your impoundment is not aerated, choose No AERATION.
If your impoundment is aerated only by mechanical aerators (these are rotating impellers),
choose MECHANICAL AERATION.
If your impoundment is aerated only by diffused air flow from submerged aerators,
choose DIFFUSED AIR AERATION.
If your impoundment is aerated by both mechanical aerators and diffused air aerators,
choose BOTH (DIFFUSED AIR a MECHANICAL).
Fraction of Surface Area Agitated Unless you chose No AERATION, you will need to enter
the fraction of surface area agitated. If you have data on agitated area, you can divide the agitated
area by the total area (in the same units) to obtain this fraction. Alternatively, you can estimate
this visually. This input is a unitless fraction and must be greater than zero and less than or equal
to one. IWAIR has been tested with values of fraction agitated from 0.01 to 1.
Submerged Air Flow (m3/s). Submerged air flow is used for diffused air systems; you
will need to enter a value if you chose either DIFFUSED AIR AERATION or BOTH (DIFFUSED AIR a MECHANICAL).
This is the total air flow of all diffusers in the impoundment. For example, if you had two
diffusers, each with an air flow of 0.1 m3/s,
you would enter 0.2 m3/s here. If you enter a
value here, it must be greater than zero. No
maximum limit is enforced. IWAIR has been
tested for values of submerged air flow from
0.01 to 100m3/s.
B.3.1.4 Waste Characteristics
Information
Type of Waste. In order to generate
an accurate estimate of a constituent's volatile
emissions, you must define the physical and
chemical characteristics of the waste you are
modeling. In particular, you must identify
whether or not the waste is best described as a
Aqueous-phase waste: a waste that is predominantly
water, with low concentrations of organics. All
chemicals remain in solution in the waste and are
usually present at concentrations below typical
solubility limits. However, it is possible for the
specific components of the waste to raise the
effective solubility level for a chemical, allowing it to
remain in solution at concentrations above the typical
solubility limit.
Organic-phase waste: a waste that is predominantly
organic chemicals, with a high concentration of
organics. Concentrations of some chemicals may
exceed solubility, causing those chemicals to come
out of solution and form areas of free product in the
WMU. In surface impoundments, this can result in a
thin organic film over the entire surface.
B-12
-------
IWAIR User's Guide Appendix B
dilute mixture of chemical compounds (aqueous) or if the waste should be considered organic,
containing high levels of organic compounds or a separate nonaqueous organic phase. These two
different types of waste matrices influence the degree of partitioning that will occur from the
waste to the air. Partitioning describes the affinity that a contaminant has for one phase (for
example, air) relative to another phase (for example, water) that drives the volatilization of
organic chemicals. Your choice of waste matrix will significantly affect the rate of emissions
from the waste. The following discussion is intended to provide background on emissions
modeling as it relates to waste type, guidance on making this selection, and clarification of the
modeling consequences of choosing AQUEOUS versus ORGANIC in IWAIR. Note that you will only be
asked to choose a waste type for risk calculations; for allowable concentration calculations,
IWAIR calculates emission rates for both aqueous and organic waste types and selects the one
that achieves the target risk or HQ at the lowest concentration applicable to the waste type.
A WMU contains solids, liquids (such as water), and air. Individual chemical molecules
are constantly moving from one of these media to another: they may be absorbed to solids,
dissolved in liquids, or assume a vapor form in air. At equilibrium, the movement into and out
of each medium is equal, so that the concentration of the chemical in each medium is constant.
The emissions model used in IWAIR, CHEMDAT8, assumes that equilibrium has been reached.
Partitioning refers to how a chemical tends to distribute itself among these different
media. Different chemicals have differing affinities for particular phases—some chemicals tend
to partition more heavily to air, while others tend to partition more heavily to water. The
different tendencies of different chemicals are described by partition coefficients or equilibrium
constants.
Of particular interest in modeling volatile emissions of a chemical from a liquid waste
matrix is the chemical's tendency to change from a liquid form to a vapor form. As a general
rule, a chemical's vapor pressure describes this tendency. The pure component vapor pressure is
a measure of this tendency for the pure chemical. A chemical in solution in another liquid (such
as a waste containing multiple chemicals) will exhibit a partial vapor pressure, which is the
chemical's share of the overall vapor pressure of the mixture; this partial vapor pressure is lower
than the pure component vapor pressure and is generally equal to the pure component vapor
pressure times the constituent's mole fraction (a measure of concentration reflecting the number
of moles of the chemical per total moles) in the solution. This general rule is known as Raoult's
law.
Most chemicals do not obey Raoult's law in dilute (i.e., low concentration) aqueous
solutions, but exhibit a greater tendency to partition to the vapor phase from dilute solutions than
would be predicted by Raoult's law. These chemicals exhibit a higher partial vapor pressure than
the direct mole fraction described above would predict.1 This altered tendency to partition to the
vapor phase in dilute solutions is referred to as Henry's law. To calculate the emissions of a
1 There are some exceptions to this behavior in dilute solutions. A notable exception is formaldehyde,
which has lower activity in dilute aqueous solution, which means that formaldehyde will have greater emissions in a
high concentration, organic-phase waste.
B-13
-------
IWAIR User's Guide Appendix B
constituent from a dilute solution, a partition coefficient called Henry's law constant is used.
Henry's law constant relates the partial vapor pressure to the concentration in the solution.
To account for these differences in the tendency of chemicals to partition to vapor phase
from different types of liquid waste matrices, CHEMDAT8 models emissions in two regimes: a
dilute aqueous phase, modeled using Henry's law constant as the partition coefficient, and an
organic phase, modeled using the partial vapor pressure predicted by Raoult's law as the partition
coefficient. In fact, there is not a clear point at which wastes shift from dilute aqueous phase to
organic phase; this is a model simplification. However, several rules of thumb may be used to
determine when the Raoult's law model would be more appropriate. The clearest rule is that any
chemical present in excess of its solubility limit in a wastewater has exceeded the bounds of
"dilute aqueous" and is more appropriately modeled using Raoult's law. Chemicals exceeding
solubility limits will typically come out of solution and behave more like pure, organic-phase
component. However, solubility limits can vary depending on site-specific parameters, such as
temperature and pH of the waste. In addition, waste matrix effects2 can cause chemicals to
remain in solution at concentrations above their typical solubility limit. This scenario (an
aqueous-phase waste with concentrations above typical solubility limits) is also best modeled
using Raoult's law. Another rule of thumb is that a waste with a total organics concentration in
excess of about 10 percent (or 100,000 ppm) is likely to behave more like an organic-phase waste
than a dilute aqueous-phase waste and be more appropriately modeled using Raoult's law.
For surface impoundments, where the waste is a liquid, the model uses an approach that
considers the resistance to mass transfer (i.e., movement of chemical mass from one phase to the
other) in the liquid and gas phases at the surface of the impoundment. Emissions are calculated
using an overall mass transfer coefficient, which is based on the partition coefficient (as
described above), the liquid-phase mass transfer factor (which accounts for resistance to transfer
in the liquid phase), and the gas-phase mass transfer factor (which accounts for resistance to
transfer in the gas phase). This is referred to as the two-film model. For organic-phase wastes,
the mass transfer is dominated by the gas-phase resistance and the partition coefficient; the
liquid-phase mass transfer resistance is negligible and is, therefore, omitted from the calculation.
This is referred to as the one-film model, or the oily film model.
In the two-film model for surface impoundments, the gas-phase and liquid-phase mass
transfer coefficients are strongly affected by the turbulence of the surface impoundment surface.
Turbulence may be caused by mechanical aeration or, to a lesser extent, diffused air aeration.
Therefore, whether the impoundment is aerated or not and how it is aerated are important inputs.
When in allowable concentration calculation mode, IWAIR calculates both aqueous-
phase and organic-phase emission rates. However, aqueous-phase emission rates, as discussed
above, are only applicable up to the solubility limit. If the use of the aqueous-phase emission
"Waste matrix effects" refers to the effect that the composition of the waste has on a constituent's
solubility in the waste or the tendency for the chemical to evaporate from the waste. For example, hexane has a
solubility in distilled water of approximately 12 mg/L; however, its solubility in methanol is much higher (more than
100,000 mg/L) (Perry and Green, 1984). Therefore, it is likely that hexane will remain dissolved in a solution of 10
percent methanol in water at higher concentrations than the aqueous solubility limit of 12 mg/L suggests.
-------
IWAIR User 's Guide Appendix B
rate results in an allowable concentration in excess of the solubility limit, IWAIR will use the
organic-phase rate instead.
Molecular Weight of Waste (g/mol) (Only for Risk Calculation). If you choose to
model an organic-phase waste, you will need to enter the average molecular weight of the waste.
This may be calculated from the molecular weights of the component constituents as follows:
E (C.) x (1 m3)
MW = _ _ - _ - _
1~te E (C./MW,) x (1 m3)
where
MWwaste = molecular weight of waste (g/mol)
Q = waste concentration of contaminant / (mg/L = g/m3)
MW; = molecular weight of contaminant /' (g/mol).
This assumes that the average molecular weight of the unspecified fraction of the organic waste
matrix has the same average molecular weight as the specified fraction (i.e., the input
contaminant concentrations). Appendix C provides values for molecular weight for all IWAIR
chemicals.
This value must be greater than or equal to 1 (the molecular weight of a hydrogen ion).
No maximum limit is enforced. IWAIR has been tested for values from 1 to 400 g/mol.
Density of Waste (g/cm3) (Only for Risk Calculation). If you choose to model an
organic-phase waste, you will need to enter the density of the waste. It is best to use a measured
value for this, but you can estimate it as follows:
waste
where
Pwaste = density of waste (g/cm3)
Q = waste concentration of contaminant / (mg/L = g/m3)
pi = density of contaminant /' (g/cm3).
Appendix C provides values for density for all IWAIR chemicals.
This value must be greater than zero. No maximum limit is enforced. IWAIR has been
tested for values from 0.01 to 3 g/cm3.
Active Biomass (g/L). This input, in conjunction with the BIODEGRADATION option, allows
you to determine what type of biodegradation is modeled for your unit. In biologically active
B-15
-------
IWAIR User's Guide Appendix B
surface impoundments, two processes occur: growth of biomass, which provides a growing
matrix for chemical adsorption and loss through settling, and direct biodegradation of chemical
constituents as the bacteria that compose the biomass consume constituent mass. Direct
biodegradation cannot occur if there is no active biomass. If an impoundment is biologically
active, it may go through a transitional period during which there is active biomass (so
adsorption and settling losses occur) but the biomass is not yet adapted to consume the specific
chemicals present (so direct biodegradation is not occurring). This transitional period will
usually end as the biomass acclimate and adapt to the chemicals present. See also the discussion
in Section B.3.1.2 on biodegradation and how active biomass interacts with the biodegradation
setting.
This input refers to the biomass concentration within the surface impoundment. Most of
the biodegradation rate constants use mixed-liquor volatile suspended solids (MLVSS) as the
measure of bioconcentration. Therefore, MLVSS in the impoundment is the preferred source for
this input if you have those data available. If not, you can approximate this (in order of
preference) using biomass concentration in the impoundment, mixed-liquor suspended solids
(MLSS) in the impoundment, MLVSS in the effluent, biomass concentration in the effluent, or
MLSS in the effluent. Alternatively, you may choose to use the IWAIR default of 0.05 g/L;
however, this default is only appropriate for biologically active impoundments. If you are
modeling a biologically inactive impoundment, this value should be set to zero, which turns off
direct biodegradation and biomass growth, so that adsorption losses are limited to adsorption to
inlet solids. This value must be greater than or equal to zero and less than or equal to 1,000 g/L.
IWAIR has been tested for this full range.
Total Suspended Solids in Influent (g/L). Total suspended solids (TSS) is used, in
conjunction with total organics, to estimate growth of solids in the impoundment. This input is
the TSS in the impoundment influent, not within the impoundment. If those data are not
available, you can approximate this (in order of preference) using total solids in the influent,
MLSS in the influent, MLVSS in the influent, biomass concentration in the influent, TSS within
the impoundment, total solids within the impoundment, or MLSS within the impoundment.
Alternatively, you may choose to use the IWAIR default of 0.2 g/L. This value must be greater
than or equal to zero and less than or equal to 1,000 g/L. IWAIR has been tested for this full
range.
Total Organics into WMU (mg/L). Total organics is used, in conjunction with TSS, to
estimate new biomass growth, so it most accurately refers to biodegradable organics. For this
reason, the most preferred data source is biological oxygen demand (BOD) in the influent. If
BOD is not available, you can estimate this using chemical oxygen demand (COD) or total
organic carbon (TOC) in the influent. Values of BOD, COD, or TOC in the effluent may be used
if influent values are not available, but these need to be adjusted up to account for removal in the
impoundment by dividing by (1 - removal efficiency). Alternatively, you can use the IWAIR
default value of 200 mg/L. This value must be greater than or equal to the sum of the
concentrations you entered for organic chemicals in the WASTES MANAGED screen and must be less
than or equal to 1,000,000 mg/L. IWAIR has been tested for this full range.
B-16
-------
IWAIR User's Guide Appendix B
Total Biorate (mg/g biomass-h). This is the degradation rate of total organics in the
impoundment. Total biorate can be measured from the maximum oxygen uptake rate from
respirometry studies, converting the oxygen uptake rate to grams carbon assuming mineralization
(formation of CO2). Alternatively, you can use the IWAIR default value of 19 mg/g biomass-h).
This value must be greater than or equal to zero. No maximum limit is enforced. IWAIR has
been tested for values from 0 to 100 mg/g biomass-h.
B.3.1.5 Mechanical Aeration Information
These inputs are needed for only if you selected MECHANICAL AERATION or BOTH (DIFFUSED AIR a
MECHANICAL).
Oxygen Transfer Rate (Ib Ofli-hp). This is the oxygen transfer rating of your aerator,
measured using water, and should be available from the design specifications of your aerator. If
no data are available, you can use the IWAIR default of 3.0 Ib O2/h-hp. This value must be
greater than zero. No maximum limit is enforced. IWAIR has been tested for values from 0.01
to 3 Ib O2/h-hp.
Number of Aerators. This is the number of impellers in your impoundment. You should
be able to count them visually if you do not have these data readily available. This value must be
greater than or equal to 1 and should be an integer. No maximum limit is enforced. IWAIR has
been tested for values from 1 to 150.
Total Power (hp). This is the power from all impellers in the impoundment combined.
You can calculate it by summing the power of each impeller (make sure they are all in the same
units first). Impeller power should be part of the design specifications for your aerators. In a
survey of surface impoundments managing nonhazardous wastes (U.S. EPA, 200la), the reported
average power per aerator ranged from 4 to 100 hp. If you cannot determine the power of your
aerators, you can estimate aerator power. Aeration and mixing power requirements often depend
on the volume of liquid needing aeration or mixing, although the range of appropriate values can
be wide. Additionally, many impoundments are aerated near the unit's influent, but a large
portion of the impoundment may remain unaerated. Consequently, the lower limit for aeration
may be more difficult to assess than the upper limit. A reasonable upper limit for aeration power
based on high aeration requirements is approximately 150 hp per million gallons of
impoundment volume (Metcalf and Eddy, 1979). This factor can be applied to the total volume
of the unit to assess a maximum power limit. A lower limit based on mixing is approximately 10
hp/million gallons; this factor can be applied to the unit volume times the fraction aerated to
yield a lower limit. The minimum value for total power must be greater the 0.25 hp. No
maximum limit is enforced. IWAIR has been tested for values from 0.26 to 3,000 hp.
Power Efficiency (fraction). Power efficiency is a misnomer that is carried over from
CHEMDAT8. This input is really the oxygen correction factor for the liquid-phase turbulent
mass transfer coefficient. The actual power efficiency, used in the equation for gas-phase
turbulent mass transfer coefficient, is hardwired to a value of 0.85 in CHEMDAT8. In order to
maintain consistency with CHEMDAT8, IWAIR also terms this input "power efficiency" but
B-17
-------
IWAIR User's Guide Appendix B
uses it as the oxygen correction factor, and hardwires the real power efficiency with a value of
0.85.
This correction factor is used to adjust the oxygen transfer rate input (which applies to
pure water) for application to wastewaters. A value for your aerator should be available from
your aerator supplier. If no data are available, you can use the IWAIR default of 0.83; this value
is consistent with its use as the oxygen correction factor. This value must be greater than zero
and less than or equal to 1. IWAIR has been tested for values from 0.01 to 1.
Impeller Diameter (cm). This is the diameter of each impeller, from one end of the
impeller to the other. If you have different impellers of different diameters, use either an average
or the most typical. If this value is in meters, feet, or inches, it must be converted to centimeters
for use in IWAIR. If you cannot determine the diameter of your impellers, you can use the
IWAIR default value of 61 cm. This value must be greater than zero and less than 100 times the
square root of the area of the unit in m2 (i.e., the impeller cannot be longer than the side length of
the unit, assuming the unit is square, which maximizes the smallest side length). IWAIR has
been tested for this full range.
Impeller Speed (rad/s). This is a measure of rotational speed (in radians per second). It
should be part of the specifications of your aerators, although it may be reported in rotations per
minute (rpm). If so, you will need to convert it to radians per second. One rotation is equal to
360 degrees, or 6.28 radians. If your aerators have different speeds, use an average or the most
typical value. If you cannot determine the speed of your impellers, you can use the IWAIR
default value of 130 rad/s. This value must be greater than zero. No maximum limit is enforced.
IWAIR has been tested for a range from 0.01 to 1,000 rad/s.
B.3.2 WMU Data for CHEMDAT8 - Land Application Unit (Screen 3B)
B.3.2.1 Meteorological Station Parameters. These inputs are used only for the
emissions modeling, not the dispersion modeling, which uses hourly meteorological data, not
annual averages. Therefore, changes to these inputs will not affect the dispersion factors.
Wind Speed (m/s). IWAIR uses wind speed to select the most appropriate empirical
emission correlation equation in CHEMDAT8; there are several of these correlations, and each
one applies to a specific range of wind speeds and unit sizes. By default, IWAIR uses the
average annual wind speed from the meteorological station that was assigned to your location.
However, you may wish to override the default if you have site-specific data on wind speed. If
you do override, you should use an overall annual average in all directions, not any measure of
peak wind speed or average only in the prevailing wind direction. Also, wind speed is often
reported in knots or mph. However, for use in IWAIR, wind speed must be converted to m/s.
This value must be greater than zero. No maximum limit is enforced. IWAIR has been tested
for values of wind speed from 0.01 to 100 m/s; however, a realistic range for average annual
wind speed is about 2 to 10 m/s.
Temperature (°C). IWAIR uses temperature to correct various temperature-dependent
chemical properties used in emissions modeling (Henry's law constant and vapor pressure) from
B-18
-------
IWAIR User's Guide Appendix B
a standard temperature to the ambient temperature. By default, IWAIR uses the average annual
temperature from the meteorological station that was assigned to your location. However, you
may wish to override the default if you have site-specific data on temperature. If you do
override, you should use an annual average temperature. Temperature may be reported in
degrees Fahrenheit (°F); however, for use in IWAIR, temperature must be converted to degrees
Celsius (°C). This value must be greater than or equal to -100°C. No maximum limit is
enforced. IWAIR has been tested for values of temperature from 0 to 50°C.
B.3.2.2 Waste/Soil Mixture Porosity Information
Total Porosity (volume fraction). Porosity refers to the spaces in a soil or waste matrix
that are not soil particles. These spaces may be filled with air or water. Total porosity is the sum
of both air- and water-filled porosity. Sometimes porosity is referred to as saturated water
content. Porosity values are used in the emissions model, and they can be used to estimate soil
saturation concentration limits. If measured data on porosity are not available, porosity can be
estimated from the bulk density and particle density of the waste as follows:
et = 1 - BD/ps
where
et = total porosity (unitless)
BD = bulk density of waste (g/cm3)
ps = particle density of waste (g/cm3).
If particle density is not available, a typical value for mineral material is 2.65 g/cm3 (Mason and
Berry, 1968).
Porosity must be greater than zero and less than 1. IWAIR has been tested for values
from 0.01 to 0.99.
Air Porosity (volume fraction). Air-filled porosity is the porosity that is filled with air
instead of water. This can be calculated from volumetric moisture content (which is equivalent
to water-filled porosity) and total porosity as follows:
6a = 6t - 6w
where
ea = air-filled porosity (unitless)
et = total porosity (unitless)
ew = water-filled porosity = volumetric water content (unitless).
B-19
-------
IWAIR User's Guide Appendix B
Air-filled porosity must be greater than zero and less than or equal to the total porosity. IWAIR
has been tested for this full range.
B.3.2.3 LAU Dimensions and Loading Information
Biodegradation (on/off). This option lets you choose whether to model biodegradation
losses in the unit. Land application units are designed to biodegrade wastes; therefore, the
biodegradation option is turned on by default. Biodegradation rates can be very site-specific. If
you believe that the actual rates in your unit are different than those included in the IWAIR
chemical properties database, the best choice would be to enter user-defined chemical entries
using your own soil biodegradation rates and select biodegradation ION I. However, if you wish
to model a land application unit without biodegradation, you can select biodegradation | OFF |.
Operating Life (yr). This parameter is the expected remaining operating life of your unit,
from the time you are modeling until you expect it to be closed. Operating life does not affect
exposure duration for land application units the way it does for other unit types, because
exposures can continue postclosure for land application units. Operating life does affect average
emission rates for land application units. Emissions are estimated for each year of operation plus
30 years postclosure, and then the maximum 7- and 30-year averages are calculated. For land
application units, IWAIR uses default exposure durations used by IWAIR of 30 years for
residents and 7.2 years for workers, regardless of operating life. Operating life should be entered
in years. This value must be greater than zero. No maximum limit is enforced; however, see the
discussion below under number of applications per year on how operating life affects the
maximum number of applications per year. IWAIR has been tested for values of operating life
from 0.01 to 100 years.
Tilling Depth of Unit (m). This is the depth to which your land application unit is tilled
and the depth to which wastes are mixed with soil; once constituents get below this depth, they
are no longer mixed with newly applied waste. Tilling depth should be entered in m; if it is in
other units, it must be converted to m. Tilling depth must be greater than zero. No maximum
limit is enforced. IWAIR has been tested for tilling depths from 0.01 to 1 m.
Area of Unit (m2). This is the total surface area of your unit in m2. Areas may be
reported in acres or hectares; these values will need to be converted to m2 for use in IWAIR.
This value must be greater than or equal to 81 and less than or equal to 8,090,000 m2; these are
the smallest and largest areas for which IWAIR can interpolate dispersion factors for ground-
level sources. IWAIR has been tested for this full range of values.
Annual Waste Quantity (Mg/yr). This is the total amount of waste that you manage in
your land application unit in a year, in Mg/yr. You may need to estimate this by multiplying the
waste quantity applied per application by the number of applications per year. This value must
be greater than zero. The maximum limit depends on the other inputs. The waste quantity,
number of applications per year, bulk density, and area imply a depth of application as follows:
dapp = Q/CNappl >< BD x A)
B-20
-------
IWAIR User's Guide Appendix B
where
dapp = depth of application (m)
Q = annual waste quantity (Mg/yr)
Nappl = number of applications per year (yr"1)
BD = bulk density of waste (g/cm3 = Mg/m3 )
A = area of unit (m2).
This depth of application may not exceed the tilling depth and, realistically, should be
considerably less than the tilling depth. IWAIR has been tested for values of annual waste
quantity from 0.01 to 10,000,000 Mg/yr.
Number of Applications per Year. This is the number of times you apply waste to the
land application unit per year. You may need to convert a frequency of application to the
corresponding number of applications per year. For example, if you apply waste weekly, you
would enter 52 applications per year in IWAIR. This value must be an integer greater than or
equal to 1. The maximum number of applications per year depends on the operating life you
specified. IWAIR models land application unit emissions in time steps equal to the time between
applications (so, if you entered 52 applications per year, IWAIR would model in 1-week time
steps), for a period equal to the operating life of the unit plus 30 years. The total number of time
steps modeled is thus:
Nsteps= (tlife-30)xNappl
where
Nsteps = total number of time steps modeled (unitless)
tiife = operating life of unit (yr)
Nappl = number of applications per year (yr"1).
This total number of time steps, Nsteps, cannot exceed 32,766 because of code limitations for
integer variables. This is unlikely to result in practical limitations, unless the operating life is
very long and the number of applications per year very high. For example, you could have daily
applications (365 applications/year) for 59 years and still be just within this limitation. IWAIR
has been tested for values from 1 to 52.
Waste Bulk Density (g/cm3). This is the overall, or bulk, density of your waste. This
should be available from measurements. Bulk density must be in g/cm3. This value must be
greater than zero. IWAIR has been tested for values from 0.01 to 14 g/cm3.
B-21
-------
IWAIR User's Guide
Appendix B
B.3.2.4 Waste Characteristics Information (Only for Risk Calculation)
Aqueous-phase waste: a waste that is predominantly
water, with low concentrations of organics. All
chemicals remain in solution in the waste and are
usually present at concentrations below typical
saturation limits. However, it is possible for the
specific components of the waste to raise the
effective saturation level for a chemical, allowing it
to remain in solution at concentrations above the
typical saturation limit.
Organic-phase waste: a waste that is predominantly
organic chemicals, with a high concentration of
organics. Concentrations of some chemicals may
exceed saturation limits, causing those chemicals to
come out of solution and form areas of free product
in the WMU.
Type of Waste. In order to generate
an accurate estimate of a constituent's volatile
emissions, you must define the physical and
chemical characteristics of the waste you are
modeling. In particular, you must identify
whether or not the waste is best described as a
dilute mixture of chemical compounds
(aqueous) or if the waste should be
considered organic, containing high levels of
organic compounds or a separate nonaqueous
organic phase. These two different types of
waste matrices influence the degree of
partitioning that will occur from the waste to
the air. Partitioning describes the affinity that
a contaminant has for one phase (for example,
air) relative to another phase (for example,
water) that drives the volatilization of organic chemicals. Your choice of waste matrix will
significantly affect the rate of emissions from the waste. The following discussion is intended to
provide background on emissions modeling as it relates to waste type, guidance on making this
selection, and clarification of the modeling consequences of choosing AQUEOUS versus ORGANIC in
IWAIR. Note that you will only be asked to choose a waste type for risk calculations; for
allowable concentration calculations, IWAIR calculates emission rates for both aqueous and
organic waste types and selects the one that achieves the target risk or HQ at the lowest
concentration applicable to the waste type.
A WMU contains solids, liquids (such as water), and air. Individual chemical molecules
are constantly moving from one of these media to another: they may be absorbed to solids,
dissolved in liquids, or assume a vapor form in air. At equilibrium, the movement into and out
of each medium is equal, so that the concentration of the chemical in each medium is constant.
The emissions model used in IWAIR, CHEMDAT8, assumes that equilibrium has been reached.
Partitioning refers to how a chemical tends to distribute itself among these different
media. Different chemicals have differing affinities for particular phases—some chemicals tend
to partition more heavily to air, while others tend to partition more heavily to water. The
different tendencies of different chemicals are described by partition coefficients or equilibrium
constants.
Of particular interest in modeling volatile emissions of a chemical from a liquid waste
matrix is the chemical's tendency to change from a liquid form to a vapor form. As a general
rule, a chemical's vapor pressure describes this tendency. The pure component vapor pressure is
a measure of this tendency for the pure chemical. A chemical in solution in another liquid (such
as a waste containing multiple chemicals) will exhibit a partial vapor pressure, which is the
chemical's share of the overall vapor pressure of the mixture; this partial vapor pressure is lower
than the pure component vapor pressure and is generally equal to the pure component vapor
B-22
-------
IWAIR User's Guide Appendix B
pressure times the constituent's mole fraction (a measure of concentration reflecting the number
of moles of the chemical per total moles) in the solution. This general rule is known as Raoult's
law.
Most chemicals do not obey Raoult's law in dilute (i.e., low concentration) aqueous
solutions, but exhibit a greater tendency to partition to the vapor phase from dilute solutions than
would be predicted by Raoult's law. These chemicals exhibit a higher partial vapor pressure than
the direct mole fraction described above would predict.3 This altered tendency to partition to the
vapor phase in dilute solutions is referred to as Henry's law. To calculate the emissions of a
constituent from a dilute solution, a partition coefficient called Henry's law constant is used.
Henry's law constant relates the partial vapor pressure to the concentration in the solution.
To account for these differences in the tendency of chemicals to partition to vapor phase
from different types of liquid waste matrices, CHEMDAT8 models emissions in two regimes: a
dilute aqueous phase, modeled using Henry's law constant as the partition coefficient, and an
organic phase, modeled using the partial vapor pressure predicted by Raoult's law as the partition
coefficient. In fact, there is not a clear point at which wastes shift from dilute aqueous phase to
organic phase; this is a model simplification. However, several rules of thumb may be used to
determine when the Raoult's law model would be more appropriate. The clearest rule is that any
chemical present in excess of its soil saturation concentration has exceeded the bounds of "dilute
aqueous" and is more appropriately modeled using Raoult's law. Chemicals exceeding
saturation limits will typically come out of solution and behave more like pure, organic-phase
component. However, saturation limits can vary depending on site-specific parameters, such as
temperature and pH of the waste. In addition, waste matrix effects4 can cause chemicals to
remain in solution at concentrations above their typical saturation limit. This scenario (an
aqueous-phase waste with concentrations above typical saturation limits) is also best modeled
using Raoult's law. Another rule of thumb is that a waste with a total organics concentration in
excess of about 10 percent (or 100,000 ppm) is likely to behave more like an organic-phase waste
than a dilute aqueous-phase waste and be more appropriately modeled using Raoult's law.
For land application units, where the waste is either a solid or mixed with a solid (such as
soil), the CHEMDAT8 emissions model considers two-phase partitioning of the waste into the
liquid (either aqueous or organic) phase and the air phase, using the partition coefficients
described above, to estimate the equilibrium vapor composition in the pore (or air) space within
the WMU. Emissions are subsequently estimated from the WMU by calculating the rate of
diffusion of the vapor-phase contaminant through the porous waste/soil media.
3 There are some exceptions to this behavior in dilute solutions. A notable exception is formaldehyde,
which has lower activity in dilute aqueous solution, which means that formaldehyde will have greater emissions in a
high concentration, organic-phase waste.
4 "Waste matrix effects" refers to the effect that the composition of the waste has on a constituent's
solubility in the waste or the tendency for the chemical to evaporate from the waste. For example, hexane has a
solubility in distilled water of approximately 12 mg/L; however, its solubility in methanol is much higher (more than
100,000 mg/L) (Perry and Green, 1984). Therefore, it is likely that hexane will remain dissolved in a solution of 10
percent methanol in water at higher concentrations than the aqueous solubility limit of 12 mg/L suggests.
B-23
-------
IWAIR User 's Guide Appendix B
When in allowable concentration calculation mode, IWAIR calculates both aqueous-
phase and organic-phase emission rates. However, aqueous-phase emission rates, as discussed
above, are only applicable up to the saturation limit. If the use of the aqueous-phase emission
rate results in an allowable concentration in excess of the saturation limit, IWAIR will use the
organic-phase rate instead.
Molecular Weight of Waste (g/mol). If you choose to model an organic-phase waste, you
will need to enter the average molecular weight of the waste. This may be calculated from the
molecular weights of the component constituents as follows:
v (C) x (1 Mg)
MW
(1 Mg)
where
MWwaste = molecular weight of waste (g/mol)
C; = waste concentration of contaminant /' (mg/kg = g/Mg)
MW; = molecular weight of contaminant /' (g/mol).
This assumes that the average molecular weight of the unspecified fraction of the organic waste
matrix has the same average molecular weight as the specified fraction (i.e., the input
contaminant concentrations). This value must be greater than or equal to 1 (the molecular weight
of a single hydrogen ion). No maximum limit is enforced.
B.3.3 WMU Data for CHEMDAT8 - Landfill (Screen 3C)
B.3.3.1 Meteorological Station Parameters. These inputs are used only for the
emissions modeling, not the dispersion modeling, which uses hourly meteorological data, not
annual averages. Therefore, changes to these inputs will not affect the dispersion factors.
Wind Speed (m/s). IWAIR uses wind speed to select the most appropriate empirical
emission correlation equation in CHEMDAT8; there are several of these correlations, and each
one applies to a specific range of wind speeds and unit sizes. By default, IWAIR uses the
average annual wind speed from the meteorological station that was assigned to your location.
However, you may wish to override the default if you have site-specific data on wind speed. If
you do override, you should use an overall annual average in all directions, not any measure of
peak wind speed or average only in the prevailing wind direction. Also, wind speed is often
reported in knots or mph. However, for use in IWAIR, wind speed must be converted to m/s.
This value must be greater than zero. No maximum limit is enforced. IWAIR has been tested
for values of wind speed from 0.01 to 100 m/s; however, a realistic range for average annual
wind speed is about 2 to 10 m/s.
Temperature (°C). IWAIR uses temperature to correct various temperature-dependent
chemical properties used in emissions modeling (Henry's law constant and vapor pressure) from
a standard temperature to the ambient temperature. By default, IWAIR uses the average annual
B-24
-------
IWAIR User's Guide Appendix B
temperature from the meteorological station that was assigned to your location. However, you
may wish to override the default if you have site-specific data on temperature. If you do
override, you should use an annual average temperature. Temperature may be reported in
degrees Fahrenheit (°F); however, for use in IWAIR, temperature must be converted to degrees
Celsius (°C). This value must be greater than or equal to -100°C. No maximum limit is
enforced. IWAIR has been tested for values of temperature from 0 to 50°C.
B.3.3.2 Waste Porosity Information
Total Porosity (volume fraction). Porosity refers to the spaces in a soil or waste matrix
that are not soil particles. These spaces may be filled with air or water. Total porosity is the sum
of both air- and water-filled porosity. Sometimes porosity is referred to as saturated water
content. Porosity values are used in the emissions model, and they can be used to estimate soil
saturation concentration limits. If measured data on porosity are not available, porosity can be
estimated from the bulk density and particle density of the waste as follows:
et = 1 - BD/ps
where
et = total porosity (unitless)
BD = bulk density of waste (g/cm3)
ps = particle density of waste (g/cm3).
If particle density is not available, a typical value for mineral material is 2.65 g/cm3 (Mason and
Berry, 1968).
Porosity must be greater than zero and less than 1. IWAIR has been tested for values
from 0.01 to 0.99.
Air Porosity (volume fraction). Air-filled porosity is the porosity that is filled with air
instead of water. This can be calculated from volumetric moisture content (which is equivalent
to water-filled porosity) and total porosity as follows:
6a = 6t - 6w
where
ea = air-filled porosity (unitless)
et = total porosity (unitless)
ew = water-filled porosity = volumetric water content (unitless).
Air-filled porosity must be greater than zero and less than or equal to the total porosity. IWAIR
has been tested for this full range.
B-25
-------
IWAIR User's Guide Appendix B
B.3.3.3 Landfill Dimensions and Loading Information
Biodegradation (on/off). This option lets you choose whether to model biodegradation
losses in the unit. Landfills are generally not designed to biodegrade wastes; therefore, the
biodegradation option is turned off for landfills by default. However, biodegradation may occur
in your landfill. If you believe it does and want to model it, you can select biodegradation | ON I.
Soil biodegradation rates can be very site-specific. If you believe that the actual rates in your unit
are different than those included in the IWAIR chemical properties database, you can enter user-
defined chemical entries using your own soil biodegradation rates.
Operating Life (yr). This parameter is the expected remaining operating life of your unit,
from the time you are modeling until you expect it to be closed. For landfills, this value is used
in emissions calculations. In addition, it affects exposure duration. IWAIR uses default
exposure durations of 30 years for residents and 7.2 years for workers. However, proper closure
of a landfill typically ends all exposures. Therefore, if the operating life you specify is less than
30 or 7.2 years, IWAIR caps the exposure duration at the operating life. Values in excess of 30
years will not affect the results for residents, and values in excess of 7.2 years will not affect the
results for workers. Operating life should be entered in years. This value must be greater than
zero. No maximum limit is enforced. IWAIR has been tested for values of operating life from
0.01 to 100 years.
Total Area of Landfill (nt2). This is the total surface area of your unit in m2. Be sure to
enter total area and not just the area of the active cell. Areas may be reported in acres or
hectares; these values will need to be converted to m2 for use in IWAIR. This value must be
greater than or equal to 81 and less than or equal to 8,090,000 m2, which are the smallest and
largest areas for which IWAIR can interpolate dispersion factors for ground-level sources.
IWAIR has been tested for this full range of values.
Total Depth of Landfill (m). This is the average depth of your unit in meters (m). If
your unit is not a constant depth, use the average or most typical depth. If you have depth
reported in units such as feet, you will need to convert them to m. This value must be greater
than zero. No maximum limit is enforced. IWAIR has been tested for values of depth from 0.01
to 30 m.
Total Number of Cells in Landfill. Landfills are typically filled one cell at a time. This
input is the total number of cells in your landfill. IWAIR models one open cell at a time, with
each cell open for a period equal to the operating life divided by the total number of cells. This
value must be greater than or equal to 1. No maximum limit is enforced. IWAIR has been tested
for values from 1 to 10,000.
Annual Quantity of Waste Disposed in Landfill (Mg/yr). This is the total amount of
waste that you manage in your landfill in a year, in Mg/yr. This value must be greater than zero.
The maximum limit depends on other inputs. The waste quantity, operating life, area, and depth
imply a loading rate as follows:
L = (Q x tlife)/(A x D)
B-26
-------
IWAIR User's Guide
Appendix B
where
L
Q
tlife
A
D
loading rate (Mg/m3 = g/cm3)
annual waste quantity (Mg/yr)
operating life (yr)
area of landfill (m2)
depth (m).
This loading rate may not exceed the bulk density of the waste. IWAIR has been tested for
values of annual waste quantity from 0.01 to 10,000,000 Mg/yr.
Bulk Density of Waste (g/cm3). This is the overall, or bulk, density of your waste. This
should be available from measurements. Bulk density must be in g/cm3. This value must be
greater than zero. IWAIR has been tested for values from 0.01 to 14 g/cm3.
B.3.3.4 Waste Characteristics Information (Only for Risk Calculation)
Type of Waste. In order to generate
an accurate estimate of a constituent's volatile
emissions, you must define the physical and
chemical characteristics of the waste you are
modeling. In particular, you must identify
whether or not the waste is best described as a
dilute mixture of chemical compounds
(aqueous) or if the waste should be
considered organic, containing high levels of
organic compounds or a separate nonaqueous
organic phase. These two different types of
waste matrices influence the degree of
partitioning that will occur from the waste to
the air. Partitioning describes the affinity that
a contaminant has for one phase (for example,
air) relative to another phase (for example,
water) that drives the volatilization of organic
chemicals. Your choice of waste matrix will significantly affect the rate of emissions from the
waste. The following discussion is intended to provide background on emissions modeling as it
relates to waste type, guidance on making this selection, and clarification of the modeling
consequences of choosing AQUEOUS versus ORGANIC in IWAIR. Note that you will only be asked to
choose a waste type for risk calculations; for allowable concentration calculations, IWAIR
calculates emission rates for both aqueous and organic waste types and selects the one that
achieves the target risk or HQ at the lowest concentration applicable to the waste type.
A WMU contains solids, liquids (such as water), and air. Individual chemical molecules
are constantly moving from one of these media to another: they may be absorbed to solids,
dissolved in liquids, or assume a vapor form in air. At equilibrium, the movement into and out
Aqueous-phase waste: a waste that is predominantly
water, with low concentrations of organics. All
chemicals remain in solution in the waste and are
usually present at concentrations below typical
saturation limits. However, it is possible for the
specific components of the waste to raise the
effective saturation level for a chemical, allowing it
to remain in solution at concentrations above the
typical saturation limit.
Organic-phase waste: a waste that is predominantly
organic chemicals, with a high concentration of
organics. Concentrations of some chemicals may
exceed saturation limits, causing those chemicals to
come out of solution and form areas of free product
in the WMU.
B-27
-------
IWAIR User's Guide Appendix B
of each medium is equal, so that the concentration of the chemical in each medium is constant.
The emissions model used in IWAIR, CHEMDAT8, assumes that equilibrium has been reached.
Partitioning refers to how a chemical tends to distribute itself among these different
media. Different chemicals have differing affinities for particular phases—some chemicals tend
to partition more heavily to air, while others tend to partition more heavily to water. The
different tendencies of different chemicals are described by partition coefficients or equilibrium
constants.
Of particular interest in modeling volatile emissions of a chemical from a liquid waste
matrix is the chemical's tendency to change from a liquid form to a vapor form. As a general
rule, a chemical's vapor pressure describes this tendency. The pure component vapor pressure is
a measure of this tendency for the pure chemical. A chemical in solution in another liquid (such
as a waste containing multiple chemicals) will exhibit a partial vapor pressure, which is the
chemical's share of the overall vapor pressure of the mixture; this partial vapor pressure is lower
than the pure component vapor pressure and is generally equal to the pure component vapor
pressure times the constituent's mole fraction (a measure of concentration reflecting the number
of moles of the chemical total moles) in the solution. This general rule is known as Raoult's law.
Most chemicals do not obey Raoult's law in dilute (i.e., low concentration) aqueous
solutions, but exhibit a greater tendency to partition to the vapor phase from dilute solutions than
would be predicted by Raoult's law. These chemicals exhibit a higher partial vapor pressure than
the direct mole fraction described above would predict.5 This altered tendency to partition to the
vapor phase in dilute solutions is referred to as Henry's law. To calculate the emissions of a
constituent from a dilute solution, a partition coefficient called Henry's law constant is used.
Henry's law constant relates the partial vapor pressure to the concentration in the solution.
To account for these differences in the tendency of chemicals to partition to vapor phase
from different types of liquid waste matrices, CHEMDAT8 models emissions in two regimes: a
dilute aqueous phase, modeled using Henry's law constant as the partition coefficient, and an
organic phase, modeled using the partial vapor pressure predicted by Raoult's law as the partition
coefficient. In fact, there is not a clear point at which wastes shift from dilute aqueous phase to
organic phase; this is a model simplification. However, several rules of thumb may be used to
determine when the Raoult's law model would be more appropriate. The clearest rule is that any
chemical present in excess of its soil saturation concentration has exceeded the bounds of "dilute
aqueous" and is more appropriately modeled using Raoult's law. Chemicals exceeding
saturation limits will typically come out of solution and behave more like pure, organic-phase
component. However, saturation limits can vary depending on site-specific parameters, such as
temperature and pH of the waste. In addition, waste matrix effects6 can cause chemicals to
5 There are some exceptions to this behavior in dilute solutions. A notable exception is formaldehyde,
which has lower activity in dilute aqueous solution, which means that formaldehyde will have greater emissions in a
high concentration, organic-phase waste.
6 "Waste matrix effects" refers to the effect that the composition of the waste has on a constituent's
solubility in the waste or the tendency for the chemical to evaporate from the waste. For example, hexane has a
solubility in distilled water of approximately 12 mg/L; however, its solubility in methanol is much higher (more than
-------
IWAIR User's Guide Appendix B
remain in solution at concentrations above their typical saturation limit. This scenario (an
aqueous-phase waste with concentrations above typical saturation limits) is also best modeled
using Raoult's law. Another rule of thumb is that a waste with a total organics concentration in
excess of about 10 percent (or 100,000 ppm) is likely to behave more like an organic-phase waste
than a dilute aqueous-phase waste and be more appropriately modeled using Raoult's law.
For landfills, where the waste is either a solid or mixed with a solid (such as soil), the
CHEMDAT8 emissions model considers two-phase partitioning of the waste into the liquid
(either aqueous or organic) phase and the air phase, using the partition coefficients described
above, to estimate the equilibrium vapor composition in the pore (or air) space within the WMU.
Emissions are subsequently estimated from the WMU by calculating the rate of diffusion of the
vapor-phase contaminant through the porous waste/soil media.
When in allowable concentration calculation mode, IWAIR calculates both aqueous-
phase and organic-phase emission rates. However, aqueous-phase emission rates, as discussed
above, are only applicable up to the saturation limit. If the use of the aqueous-phase emission
rate results in an allowable concentration in excess of the saturation limit, IWAIR will use the
organic-phase rate instead.
Molecular Weight of Waste (g/mol). If you choose to model an organic-phase waste, you
will need to enter the average molecular weight of the waste. This may be calculated from the
molecular weights of the component constituents as follows:
MW E (Q x (1 Mg)
MWW , =
E (C/MW;) x (l Mg)
where
MWwaste = molecular weight of waste (g/mol)
C; = waste concentration of contaminant / (mg/kg = g/Mg)
MW; = molecular weight of contaminant /' (g/mol).
This assumes that the average molecular weight of the unspecified fraction of the organic waste
matrix has the same average molecular weight as the specified fraction (i.e., the input
contaminant concentrations). This value must be greater than or equal to 1 (the molecular weight
of a single hydrogen ion). No maximum limit is enforced.
B.3.4 WMU Data for CHEMDAT8 - Waste Pile (Screen 3D)
B.3.4.1 Meteorological Station Parameters. These inputs are used only for the
emissions modeling, not the dispersion modeling, which uses hourly meteorological data, not
annual averages. Therefore, changes to these inputs will not affect the dispersion factors.
100,000 mg/L) (Perry and Green, 1984). Therefore, it is likely that hexane will remain dissolved in a solution of 10
percent methanol in water at higher concentrations than the aqueous solubility limit of 12 mg/L suggests.
B-29
-------
IWAIR User's Guide Appendix B
Wind Speed (m/s). IWAIR uses wind speed to select the most appropriate empirical
emission correlation equation in CHEMDAT8; there are several of these correlations, and each
one applies to a specific range of wind speeds and unit sizes. By default, IWAIR uses the
average annual wind speed from the meteorological station that was assigned to your location.
However, you may wish to override the default if you have site-specific data on wind speed. If
you do override, you should use an overall annual average in all directions, not any measure of
peak wind speed or average only in the prevailing wind direction. Also, wind speed is often
reported in knots or mph. However, for use in IWAIR, wind speed must be converted to m/s.
This value must be greater than zero. No maximum limit is enforced. IWAIR has been tested
for values of wind speed from 0.01 to 100 m/s; however, a realistic range for average annual
wind speed is about 2 to 10 m/s.
Temperature (°C). IWAIR uses temperature to correct various temperature-dependent
chemical properties used in emissions modeling (Henry's law constant and vapor pressure) from
a standard temperature to the ambient temperature. By default, IWAIR uses the average annual
temperature from the meteorological station that was assigned to your location. However, you
may wish to override the default if you have site-specific data on temperature. If you do
override, you should use an annual average temperature. Temperature may be reported in
degrees Fahrenheit (°F); however, for use in IWAIR, temperature must be converted to degrees
Celsius (°C). This value must be greater than or equal to -100°C. No maximum limit is
enforced. IWAIR has been tested for values of temperature from 0 to 50°C.
B.3.4.2 Waste Porosity Information
Total Porosity (volume fraction). Porosity refers to the spaces in a soil or waste matrix
that are not soil particles. These spaces may be filled with air or water. Total porosity is the sum
of both air- and water-filled porosity. Sometimes porosity is referred to as saturated water
content. Porosity values are used in the emissions model, and they can be used to estimate soil
saturation concentration limits. If measured data on porosity are not available, porosity can be
estimated from the bulk density and particle density of the waste as follows:
et = 1 - BD/ps
where
et = total porosity (unitless)
BD = bulk density of waste (g/cm3)
ps = particle density of waste (g/cm3).
If particle density is not available, a typical value for mineral material is 2.65 g/cm3 (Mason and
Berry, 1968).
Porosity must be greater than zero and less than 1. IWAIR has been tested from 0.01 to
0.99.
B-30
-------
IWAIR User's Guide Appendix B
Air Porosity (volume fraction). Air-filled porosity is the porosity that is filled with air
instead of water. This can be calculated from volumetric moisture content (which is equivalent
to water-filled porosity) and total porosity as follows:
6a = 6t - 6w
where
ea = air-filled porosity (unitless)
et = total porosity (unitless)
ew = water-filled porosity = volumetric water content (unitless).
Air-filled porosity must be greater than zero and less than or equal to the total porosity. IWAIR
has been tested for this full range.
B.3.4.3 Waste Pile Dimensions and Loading Information
Biodegradation (on/off). This option lets you choose whether to model biodegradation
losses in the unit. Waste piles are generally not designed to biodegrade wastes; therefore, the
biodegradation option is turned off for waste piles by default. However, biodegradation may
occur in your waste pile, particularly if residence times of waste in the waste pile are long (on the
order of 60 days to one year). With such residence times, naturally occurring microorganisms
could potentially acclimate and degrade contaminants within the waste pile. If you believe that
biodegradation does occur in your waste pile and you want to model it, you can select
biodegradation | ON I. Soil biodegradation rates can be very site-specific. If you believe that the
actual rates in your unit are different than those included in the IWAIR chemical properties
database, you can enter user-defined chemical entries using your own soil biodegradation rates.
Operating Life (yr). This parameter is the expected remaining operating life of your unit,
from the time you are modeling until you expect it to be closed. Operating life does not affect
emissions estimates for waste piles, which are modeled at steady state. However, operating life
may affect exposure duration. IWAIR uses default exposure durations of 30 years for residents
and 7.2 years for workers. However, proper closure of a waste pile typically ends all exposures.
Therefore, if the operating life you specify is less than 30 or 7.2 years, IWAIR caps the exposure
duration at the operating life. Values in excess of 30 years will not affect the results for
residents, and values in excess of 7.2 years will not affect the results for workers. Operating life
should be entered in years. This value must be greater than zero. No maximum limit is enforced.
IWAIR has been tested for values of operating life from 0.01 to 100 years.
Height of Waste Pile Unit (m). This is the average height of your waste pile in meters
(m). If your waste pile is not a constant height, use the average or most typical height. If you
have height reported in units such as feet, you will need to convert them to m. This value must
be greater than or equal to 1 m and less than or equal to 10 m; these are the smallest and largest
heights for which IWAIR can interpolate dispersion factors for waste piles. IWAIR has been
tested for this full range.
B-31
-------
IWAIR User's Guide
Appendix B
Area of Unit (m2). This is the total surface area of your unit in m2. Areas may be
reported in acres or hectares; these values will need to be converted to m2 for use in IWAIR.
This value must be greater than or equal to 20 and less than or equal to 1,300,000 m2; these are
the smallest and largest areas for which IWAIR can interpolate dispersion factors for waste piles.
IWAIR has been tested for this full range of values.
Average Quantity of Waste in Waste Pile (Mg/yr). This is the average amount of waste
in your waste pile over a year, in Mg/yr. This value must be greater than zero. No maximum
limit is enforced. IWAIR has been tested for values of annual waste quantity from 0.01 to
10,000,000 Mg/yr.
Bulk Density of Waste (g/cm3). This is the overall, or bulk, density of your waste. This
should be available from measurements. Bulk density must be in g/cm3. This value must be
greater than zero. IWAIR has been tested for values from 0.01 to 14 g/cm3.
B.3.4.4 Waste Characteristics Information (Only for Risk Calculation)
Type of Waste. In order to generate
an accurate estimate of a constituent's volatile
emissions, you must define the physical and
chemical characteristics of the waste you are
modeling. In particular, you must identify
whether or not the waste is best described as a
dilute mixture of chemical compounds
(aqueous) or if the waste should be
considered organic, containing high levels of
organic compounds or a separate nonaqueous
organic phase. These two different types of
waste matrices influence the degree of
partitioning that will occur from the waste to
the air. Partitioning describes the affinity that
a contaminant has for one phase (for example,
air) relative to another phase (for example,
water) that drives the volatilization of organic
chemicals. Your choice of waste matrix will significantly affect the rate of emissions from the
waste. The following discussion is intended to provide background on emissions modeling as it
relates to waste type, guidance on making this selection, and clarification of the modeling
consequences of choosing AQUEOUS versus ORGANIC in IWAIR. Note that you will only be asked to
choose a waste type for risk calculations; for allowable concentration calculations, IWAIR
calculates emission rates for both aqueous and organic waste types and selects the one that
achieves the target risk or HQ at the lowest concentration applicable to the waste type.
A WMU contains solids, liquids (such as water), and air. Individual chemical molecules
are constantly moving from one of these media to another: they may be absorbed to solids,
dissolved in liquids, or assume a vapor form in air. At equilibrium, the movement into and out
Aqueous-phase waste: a waste that is predominantly
water, with low concentrations of organics. All
chemicals remain in solution in the waste and are
usually present at concentrations below typical
saturation limits. However, it is possible for the
specific components of the waste to raise the
effective saturation level for a chemical, allowing it
to remain in solution at concentrations above the
typical saturation limit.
Organic-phase waste: a waste that is predominantly
organic chemicals, with a high concentration of
organics. Concentrations of some chemicals may
exceed saturation limits, causing those chemicals to
come out of solution and form areas of free product
in the WMU.
B-32
-------
IWAIR User's Guide Appendix B
of each medium is equal, so that the concentration of the chemical in each medium is constant.
The emissions model used in IWAIR, CHEMDAT8, assumes that equilibrium has been reached.
Partitioning refers to how a chemical tends to distribute itself among these different
media. Different chemicals have differing affinities for particular phases—some chemicals tend
to partition more heavily to air, while others tend to partition more heavily to water. The
different tendencies of different chemicals are described by partition coefficients or equilibrium
constants.
Of particular interest in modeling volatile emissions of a chemical from a liquid waste
matrix is the chemical's tendency to change from a liquid form to a vapor form. As a general
rule, a chemical's vapor pressure describes this tendency. The pure component vapor pressure is
a measure of this tendency for the pure chemical. A chemical in solution in another liquid (such
as a waste containing multiple chemicals) will exhibit a partial vapor pressure, which is the
chemical's share of the overall vapor pressure of the mixture; this partial vapor pressure is lower
than the pure component vapor pressure and is generally equal to the pure component vapor
pressure times the constituent's mole fraction (a measure of concentration reflecting the number
of moles of the chemical per total moles) in the solution. This general rule is known as Raoult's
law.
Most chemicals do not obey Raoult's law in dilute (i.e., low concentration) aqueous
solutions, but exhibit a greater tendency to partition to the vapor phase from dilute solutions than
would be predicted by Raoult's law. These chemicals exhibit a higher partial vapor pressure than
the direct mole fraction described above would predict.7 This altered tendency to partition to the
vapor phase in dilute solutions is referred to as Henry's law. To calculate the emissions of a
constituent from a dilute solution, a partition coefficient called Henry's law constant is used.
Henry's law constant relates the partial vapor pressure to the concentration in the solution.
To account for these differences in the tendency of chemicals to partition to vapor phase
from different types of liquid waste matrices, CHEMDAT8 models emissions in two regimes: a
dilute aqueous phase, modeled using Henry's law constant as the partition coefficient, and an
organic phase, modeled using the partial vapor pressure predicted by Raoult's law as the partition
coefficient. In fact, there is not a clear point at which wastes shift from dilute aqueous phase to
organic phase; this is a model simplification. However, several rules of thumb may be used to
determine when the Raoult's law model would be more appropriate. The clearest rule is that any
chemical present in excess of its soil saturation concentration has exceeded the bounds of "dilute
aqueous" and is more appropriately modeled using Raoult's law. Chemicals exceeding
saturation limits will typically come out of solution and behave more like pure, organic-phase
component. However, saturation limits can vary depending on site-specific parameters, such as
7 There are some exceptions to this behavior in dilute solutions. A notable exception is formaldehyde,
which has lower activity in dilute aqueous solution, which means that formaldehyde will have greater emissions in a
high concentration, organic-phase waste.
B-33
-------
IWAIR User's Guide Appendix B
temperature and pH of the waste. In addition, waste matrix effects8 can cause chemicals to
remain in solution at concentrations above their typical saturation limit. This scenario (an
aqueous-phase waste with concentrations above typical saturation limits) is also best modeled
using Raoult's law. Another rule of thumb is that a waste with a total organics concentration in
excess of about 10 percent (or 100,000 ppm) is likely to behave more like an organic-phase waste
than a dilute aqueous-phase waste and be more appropriately modeled using Raoult's law.
For waste piles, where the waste is either a solid or mixed with a solid (such as soil), the
CHEMDAT8 emissions model considers two-phase partitioning of the waste into the liquid
(either aqueous or organic) phase and the air phase, using the partition coefficients described
above, to estimate the equilibrium vapor composition in the pore (or air) space within the WMU.
Emissions are subsequently estimated from the WMU by calculating the rate of diffusion of the
vapor-phase contaminant through the porous waste/soil media.
When in allowable concentration calculation mode, IWAIR calculates both aqueous-
phase and organic-phase emission rates. However, aqueous-phase emission rates, as discussed
above, are only applicable up to the saturation limit. If the use of the aqueous-phase emission
rate results in an allowable concentration in excess of the saturation limit, IWAIR will use the
organic-phase rate instead.
Molecular Weight of Waste (g/mol). If you choose to model an organic-phase waste, you
will need to enter the average molecular weight of the waste. This may be calculated from the
molecular weights of the component constituents as follows:
E (C.) x (1 Mg)
MW = - —
1V1VV waste
(C/MW;) X (1 Mg)
where
MWwaste = molecular weight of waste (g/mol)
C; = waste concentration of contaminant /' (mg/kg = g/Mg)
MW; = molecular weight of contaminant / (g/mol).
This assumes that the average molecular weight of the unspecified fraction of the organic waste
matrix has the same average molecular weight as the specified fraction (i.e., the input
contaminant concentrations). This value must be greater than or equal to 1 (the molecular weight
of a single hydrogen ion). No maximum limit is enforced.
"Waste matrix effects" refers to the effect that the composition of the waste has on a constituent's
solubility in the waste or the tendency for the chemical to evaporate from the waste. For example, hexane has a
solubility in distilled water of approximately 12 mg/L; however, its solubility in methanol is much higher (more than
100,000 mg/L) (Perry and Green, 1984). Therefore, it is likely that hexane will remain dissolved in a solution of 10
percent methanol in water at higher concentrations than the aqueous solubility limit of 12 mg/L suggests.
-------
IWAIR User's Guide Appendix B
B.4 User-Override Emission Rates (Screens 4A and 4B)
Override Emission Rates. You may choose either to enter your own emission rates for
all chemicals modeled or to override IWAIR's calculated emission rates for some or all of the
chemicals modeled. Override emission rates may be based on measured data or modeled results
from an emissions model outside of IWAIR, but regardless of source, should reflect a long-term
average, not a short-term peak.
This input has different units in risk calculation mode versus allowable concentration
mode:
• In risk mode, this input should be the actual measured or modeled emissions from
your unit, normalized on area (in g/m2/s). If emission rates are based on modeled
rates, they should correspond to the actual waste concentrations in your unit.
Emissions in g/s should be normalized to area by dividing by the area of the unit.
• In allowable concentration mode, the emission rate should either be based on
modeled emissions corresponding to a waste concentration of 1 mg/kg or 1 mg/L,
or they should be normalized to concentration by dividing by the actual waste
concentration present when the emissions were measured or modeled. The units
for allowable concentration mode emission rates (g/m2-s per mg/kg or mg/L)
reflect this. Emissions measured or modeled in g/s should also be normalized to
area by dividing by the area of the unit.
You may input one override emission rate per chemical. In risk mode, IWAIR assumes
this emission rate corresponds to the waste type (aqueous or organic) you chose on Screen 3,
WMU DATA FOR CHEMDAT8. In allowable concentration mode, IWAIR assumes this emission rate
corresponds to an aqueous waste. As a result, IWAIR will not output concentrations in
concentration mode in excess of each chemical's solubility or saturation limit if you have entered
user-override emission factors.
Source and Justification for User-Override Values. If you enter override emission
factors, you must document their source in this field. The justification field may not be left
blank.
B.5 ISCST3 or User-Override Dispersion Factors (Screen 5A)
Distance to Receptor (m). This is the distance from the edge of your unit to the receptor
for whom you want to estimate risk or allowable concentration. You must choose from one of
the six values available in IWAIR: 25, 50, 75, 150, 500, or 1,000 m. Choose the distance that
best approximates the location of your receptors. If you are using IWAIR's dispersion factors,
they will correspond to the distance you select; selecting a distance smaller than the actual
distance to receptors near your unit will overestimate risk, and selecting a distance larger than the
actual distance will underestimate risk. If you enter your own dispersion factors, this input is
only for your reference and is not used in calculations. Therefore, you should select the distance
that most closely approximates the distance your dispersion factor applies to.
B-35
-------
IWAIR User's Guide Appendix B
Receptor Type. Two different types of exposed individuals, worker and resident, can be
modeled with IWAIR. The dispersion factors do not vary with receptor type; however, receptor
type is chosen here for convenience. The difference between these two receptor types lies in the
exposure factors, such as body weight and inhalation rate, used to calculate risk for carcinogens.
There is no difference between them for noncarcinogens because calculation of noncarcinogenic
risk does not depend on exposure factors. The assumptions for residents reflect males and
females from birth through age 30; it is important to consider childhood exposures because
children typically have higher intake rates per kilogram of body weight than adults. The actual
exposure duration used for residents is the smaller of 30 years or the operating life of the unit that
you entered (except for land application units, for which the exposure duration for residents is
always 30 years regardless of operating life). Exposure for residents starts at birth and continues
for the length of the exposure duration, using the appropriate age-specific exposure factors. The
assumptions for workers reflect a full-time, outdoor worker; all exposure is assumed to occur as
an adult. The exposure duration for workers is the smaller of 7.2 years or the operating life of the
unit (except for land application units, for which the exposure duration for workers is always 7.2
years regardless of operating life). For more information on the specific exposure factors used
for residents and workers, see the IWAIR Technical Background Document.
User-Override Dispersion Factors. You may choose either to enter your own dispersion
factors for all receptors modeled or to override IWAIR's calculated dispersion factors for some
or all of the receptors modeled. Note that dispersion factors are not chemical-specific, nor are
they specified to receptor type (resident or worker). Dispersion factors may be based on
measured air concentrations or air concentrations modeled outside of IWAIR. If based on
modeled air concentrations, they should correspond to an emission rate of 1 |j,g/m2-s. If based on
measured air concentration data, they should be normalized to emission rate by dividing by the
actual emission rate measured or modeled. The units for dispersion factors (|J,g/m3 per |j,g/m2-s)
reflect this. Note that when you enter your own dispersion factors, you are not limited to the six
receptor distances included in IWAIR. In this circumstance, those distances are for your
reference only.
Source and Justification for User-Override Values. If you enter override dispersion
factors, you must document their source in this field. If your receptor distances differ from the
distances available in IWAIR, it may be useful to document here the actual receptor distances for
each numbered receptor. The justification field may not be left blank.
B.6 Results Screen (Screen 6)
B.6.1 Target Risk and Hazard Quotient Value
These inputs are needed for allowable concentration mode only. In risk mode, risk and
HQ are calculated by IWAIR.
Risk Value for Carcinogens. Choose one of the five values available. A higher risk
value represents greater risk and will result in lower allowable concentrations. This value is not
required if no carcinogens are being modeled (i.e., CSF is NA for all chemicals modeled).
B-36
-------
IWAIR User's Guide Appendix B
Hazard Quotient Value for Noncarcinogens. Choose one of the five values available.
A higher HQ value represents greater likelihood of health effects and will result in lower
allowable concentrations. This value is not required if no noncarcinogens are being modeled
(i.e., RfC is NA for all chemicals modeled).
B.6.2 Health Benchmarks
Parameter guidance for health benchmarks is provided in Section B.2.2.3.
B.7 References
ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Minimal Risk Levels
(MRLs)for Hazardous Substances. http://atsdrl.atsdr.cdc.gov:8080/mrls.html
Budavari, S. (Ed.). 1996. The Merck Index, An Encyclopedia of Chemicals, Drugs, and
Biologicals. 12th Edition. Merck & Co. Inc., Rahway, NJ.
CalEPA (California Environmental Protection Agency). 1999a. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part II. Technical Support Document for Describing
Available Cancer Potency Factors. Office of Environmental Health Hazard Assessment,
Berkeley, CA. Available online at http://www.oehha.org/scientific/hsca2.htm.
CalEPA (California Environmental Protection Agency). 1999b. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part III. Technical Support Document for the
Determination ofNoncancer Chronic Reference Exposure Levels. SRP Draft. Office of
Environmental Health Hazard Assessment, Berkeley, CA. Available online at
http ://www. oehha. org/hotspots/RAGSII. html.
CalEPA (California Environmental Protection Agency). 2000. Air Toxics Hot Spots Program
Risk Assessment Guidelines: Part III. Technical Support Document for the
Determination ofNoncancer Chronic Reference Exposure Levels. Office of
Environmental Health Hazard Assessment, Berkeley, CA. Available online (in 3
sections) at http://www.oehha.org/air/chronic_rels/22RELS2k.html,
http: //www. oehha. org/air/chroni c_rel s/42kChREL. html,
http://www.oehha.org/air/chroni c_rels/Jan200 IChREL.html.
CambridgeSoft Corporation. 2001. ChemFinder.com database and internet searching.
http://chemfmder.cambridgesoft.com. Accessed July 2001.
Coburn, J., C. Allen, D. Green, and K. Leese. 1988. Site Visits of Aerated and Nonaerated
Impoundments. Summary Report. U.S. EPA 68-03-3253, Work Assignment 3-8.
Research Triangle Institute, RTF, NC.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, and E.M. Michalenko Printup, H.T.
(Ed.). 1991. Handbook of Environmental Degradation Rates. Lewi s Publi shers,
Chelsea, MI.
B-37
-------
IWAIR User's Guide Appendix B
Kollig, H.P. 1993. Environmental Fate Constants for Organic Chemicals Under Consideration
for EPA 's Hazardous Waste Identification Projects. EPA/600/R-93/132., Athens, GA.
August.
Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt. 1990. Handbook of Chemical Property
Estimation Methods: Environmental Behavior of Organic Compounds. American
Chemical Society, Washington, DC.
Mason, B., and L.G. Berry. 1968. Elements of Mineralogy. W.H. Freeman and Company. San
Francisco, p. 410.
Metcalf and Eddy, Inc. 1979. Wastewater Engineering: Treatment, Disposal and Reuse. Edited
by Tchobanoglous, G., McGraw-Hill, Inc.
Perry, R.H., and D.W. Green. 1984. Perry's Chemical Engineer's Handbook, 6th Edition.
McGraw-Hill, New York.
Reid, R.C., J.M. Prausnitz, and T.K. Sherwood. 1977. The Properties of Gases and Liquids, 3rd
Edition. McGraw-Hill, New York.
Syracuse Research Corporation (SRC). 1999. CHEMFATE Chemical Search, Environmental
Science Center, Syracuse, NY. http://esc.syrres.com/efdb/Chemfate.htm. Accessed July
2001.
U.S. EPA (Environmental Protection Agency). 1986. Addendum to the Health Assessment
Document for Tetrachloroethylene (Perchloroethylene). Updated Carcinogenicity
Assessment for Tetrachloroethylene (Perchloroethylene, PERC, PCE). External Review
Draft. EPA/600/8-82-005FA. Office of Health and Environmental Assessment, Office of
Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1987a. Addendum to the Health Assessment
Document for Trichloroethylene. Updated Carcinogenicity Assessment for
Trichloroethylene. External Review Draft. EPA/600/8-82-006FA. Office of Health and
Environmental Assessment, Office of Research and Development, Washington DC.
U.S. EPA (Environmental Protection Agency). 1987b. Processes, Coefficients, and Models for
Simulation Toxic Organics and Heavy Metals in Surface Waters. EPA/600/3-87/015.
Office of Research and Development, Athens, GA.
U.S. EPA (Environmental Protection Agency). 1997a. Health Effects Assessment Summary
Tables (HEAST). EPA-540-R-97-036. FY 1997 Update.
U.S. EPA (Environmental Protection Agency). 1997b. Superfund Chemical Data Matrix
(SCDM). Office of Emergency and Remedial Response. Web site at
http://www.epa.gov/oerrpage/superfund/resources/scdm/index.htm. June
B-38
-------
IWAIR User's Guide Appendix B
U.S. EPA (Environmental Protection Agency). 1998a. Hazardous waste management system;
identification and listing of hazardous waste; solvents; final rule. Federal Register
63 FR 64371-402.
U.S. EPA (Environmental Protection Agency). 1998b. Risk Assessment Paper for: Evaluation
of the Systemic Toxicity ofHexachlorobutadiene (CASRN 87-68-3) Resulting from Oral
Exposure. 98-009/07-17-98. National Center for Environmental Assessment. Superfund
Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999a. Risk Assessment Issue Paper for:
Derivation of Provisional Oral Chronic RfD and Subchronic RfDsfor 1,1,1-
Trichloroethane (CASRN 71-55-6). 98-025/8-4-99. National Center for Environmental
Assessment. Superfund Technical Support Center, Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 1999b. Risk Assessment Paper for: An Updated
Systemic Toxicity Evaluation of n-Hexane (CASRN 110-54-3). 98-019/10-1-99. National
Center for Environmental Assessment. Superfund Technical Support Center, Cincinnati,
OH.
U.S. EPA (Environmental Protection Agency). 2000a. Exposure and Human Health
Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds.
Part I: Estimating Exposure to Dioxin-Like Compounds. Volume 3—Properties,
Environmental Levels, and Background Exposures. Draft Final Report. EPA/600/P-
00/001. Office of Research and Development, Washington, DC. September.
U.S. EPA (Environmental Protection Agency). 2000b. Risk Assessment Paper for: Derivation
of a Provisional RfD for 1,1,2,2-Tetrachloroethane (CASRN 79-34-5). 00-122/12-20-00.
National Center for Environmental Assessment. Superfund Technical Support Center,
Cincinnati, OH.
U.S. EPA (Environmental Protection Agency). 200la. Industrial Surface Impoundments in the
United States. EPA 530-R-01-005. Office of Solid Waste, Washington, DC. March.
http://www.epa.gov/OSWRCRA/hazwaste/! dr/icr/ldr-impd.htm#sis.
U.S. EPA (Environmental Protection Agency). 2001b. Integrated Risk Information System
(IRIS). National Center for Environmental Assessment, Office of Research and
Development, Washington, DC. Available online at http://www.epa.gov/iris/ Office of
Solid Waste and Emergency Response, Washington, DC.
U.S. EPA (Environmental Protect! on Agency). 2001c. WATER9. Version 1.0.0. Office of Air
Quality Planning and Standards, Research Triangle Park, NC. Web site at
http://www.epa.gov/ttn/chief/softward.html. May 1.
U.S. NLM (National Library of Medicine). 2001. Hazardous Substances Data Bank (HSDB).
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Accessed July 2001.
B-39
-------
-------
Appendix C
Physical-Chemical Property Values
-------
-------
IWAIR User's Guide
Appendix C
Table C-l. Molecular Weights and Densities for IWAIR Constituents
CAS
50000
50328
55185
56235
56495
57976
62533
67561
67641
67663
67721
68122
71432
71556
74839
74873
75014
75058
75070
75092
75150
75218
75252
75274
75354
75569
75694
75718
76131
77474
78591
78875
78933
79005
79016
79061
79107
79345
79469
80626
Chemical Name
Formaldehyde
Benzo(a)pvrene
N-Nitrosodiethvlamine
Carbon tetrachloride
3-Methylcholanthrene
7,1 2-Dimethy Ibenz [al anthracene
Aniline
Methanol
Acetone
Chloroform
Hexachloroethane
N,N-Dimethyl formamide
Benzene
1,1,1- Trichloroethane
Methyl bromide
Methyl chloride
Vinyl chloride
Acetonitrile
Acetaldehyde
Methylene chloride
Carbon disulfide
Ethvlene oxide
Tribromomethane
Bromodichloromethane
1.1-Dichloroethvlene
Proovlene oxide
Trichlorofluoromethane
Dichlorodifluoromethane
1 .1 .2-Trichloro- 1 .2.2-trifluoroethane
Hexachlorocvclopentadiene
Isoohorone
1 ,2-Dichloropropane
Methyl ethyl ketone
1,1 ,2- Trichloroethane
Trichloroethvlene
Acrvlamide
Acrylic acid
1,1 ,2,2-Tetrachloroethane
2-Nitroorooane
Methyl methacrvlate
Molecular Weight (g/mole)
30
252
102
154
268
256
93
32
58
119
237
73
78
133
95
50
63
41
44
85
76
44
253
164
97
58
137
121
187
273
138
113
72
133
131
71
72
168
89
100
Density (g/cm3)
0.82
1.35
0.94
1.59
1.28
1.02
1.02
0.79
0.79
1.48
2.09
0.94
0.88
1.34
1.68
0.91
0.91
0.79
0.78
1.33
1.26
0.89
2.90
1.98
1.21
0.86
1.49
1.49
1.56
1.70
0.93
1.16
0.81
1.44
1.46
1.12
1.05
1.60
0.98
0.94
C-3
-------
IWAIR User's Guide
Appendix C
Table C-l. Molecular Weights and Densities for IWAIR Constituents
CAS
85449
87683
91203
92875
95501
95534
95578
95658
96128
98011
98828
98953
100414
100425
106467
106887
106898
106934
106990
107028
107051
107062
107131
107211
108054
108101
108883
108907
108930
108952
109864
110496
110543
110805
110861
111159
118741
120821
121142
121448
Chemical Name
Phthalic anhydride
Hexachloro- 1 ,3-butadiene
Naphthalene
Benzidine
o-Dichlorobenzene
o-Toluidine
2-Chlorophenol
3,4-Dimethylphenol
1 ,2-Dibromo-3-chloropropane
Furfural
Cumene
Nitrobenzene
Ethylbenzene
Styrene
p-Dichlorobenzene
1 ,2-Epoxybutane
Epichlorohydrin
Ethylene dibromide
1,3-Butadiene
Acrolein
Allvl chloride
1 ,2-Dichloroethane
Acrvlonitrile
Ethvlene alvcol
Vinvl acetate
Methyl isobutvl ketone
Toluene
Chlorobenzene
Cvclohexanol
Phenol
2-Methoxvethanol
2-Methoxvethanol acetate
n-Hexane
2-Ethoxvethanol
Pvridine
2-Ethoxvethanol acetate
Hexachlorobenzene
1 ,2,4- Trichlorobenzene
2.4-Dinitrotoluene
Triethvlamine
Molecular Weight (g/mole)
148
261
128
184
147
107
129
122
236
96
120
123
106
104
147
72
93
188
54
56
77
99
53
62
86
100
92
113
100
94
76
118
86
90
79
132
285
181
182
101
Density (g/cm3)
1.53
1.56
1.03
1.25
1.31
1.00
1.26
0.98
2.09
1.16
0.86
1.20
0.87
0.91
1.25
0.84
1.18
2.18
0.61
0.84
0.94
1.24
0.81
1.11
0.93
0.80
0.87
1.11
0.96
1.05
0.96
1.01
0.65
0.93
0.98
0.98
2.04
1.46
1.32
0.73
C4
-------
IWAIR User's Guide
Appendix C
Table C-l. Molecular Weights and Densities for IWAIR Constituents
CAS
122667
123911
124481
126998
127184
630206
924163
930552
1319773
1330207
1634044
1746016
7439976
7439977
10061015
10061026
Chemical Name
1 ,2-Diphenvlhvdrazine
1,4-Dioxane
Chlorodibromomethane
Chloroprene
Tetrachloroethylene
1 ,1 ,1 ,2-Tetrachloroethane
N-Nitrosodi-n-butylamine
N-Nitrosopyrrolidine
Cresols (total)
Xylenes
Methyl tert-butyl ether
2,3,7,8-TCDD
Mercury
Divalent Mercury
cis- 1 ,3-Dichloropropylene
trans- 1 ,3-Dichloropropylene
Molecular Weight (g/mole)
184
88
208
89
166
168
158
100
108
106
88
322
201
201
111
111
Density (g/cm3)
1.16
1.03
2.45
0.96
1.62
1.54
0.90
1.09
1.06
0.87
0.74
1.83
13.53
5.60
1.22
1.22
C-5
-------
-------
EPA/600/R-93/182
September 1993
Technical Guidance Document:
QUALITY ASSURANCE AND QUALITY CONTROL
FOR WASTE CONTAINMENT FACILITIES
by
David E. Daniel
University of Texas at Austin
Department of Civil Engineering
Austin, Texas 78712
and
Robert M. Koerner
Geosynthetic Research Institute
West Wing, Rush Building No. 10
Philadelphia, Pennsylvania 19104
Cooperative Agreement No. CR-815546-01-0
Project Officer
David A. Carson
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
-------
DISCLAIMER
The information in the document has been funded wholly or in part by the United States
Environmental Protection Agency under assistance agreement number CR-815546-01-0. It has
been subject to the Agency's peer and administrative review and has been approved for publication
as a U.S. EPA document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
This document contains numerous references to various procedures for performing tests as
part of the process of quality control and quality assurance. Standards published by the American
Society for Testing and Materials (ASTM) are referenced wherever possible because ASTM
procedures represent consensus standards. Other testing procedures referenced in this document
were generally developed by an individual or a small group of individuals and, therefore, do not
represent consensus standards. The mention of non-consensus standards does not constitute their
endorsement.
The reader is cautioned against using this document for the direct preparation of site
specific quality assurance plans or related documents without giving proper consideration to the
site- and project-specific requirements. To do so would ignore the educational context of the
accompanying text, innovations made since the publication of the document, and the prevailing
unique and site-specific aspects of all waste containment facilities.
ii
-------
FOREWORD
Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased generation of
materials that, if improperly dealt with, can threaten both public health and the
environment. The United States Environmental Protection Agency (U.S. EPA) is
charged by Congress with protecting the Nation's land, air, and water resources.
Under a mandate of national environmental laws, the Agency strives to formulate
and implement actions leading to a compatible balance between human activities
and the ability of natural systems to support and nurture life. These laws
direct the U.S. EPA to perform research to define our environmental problems,
measure the impacts, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning,
implementing, and managing research, development, and demonstration programs to
provide an authoritative, defensible engineering basis in support of the
policies, programs, and regulations of the U.S. EPA with respect to drinking
water, wastewater, pesticides, toxic substances, solid and hazardous wastes, and
Superfund-related activities. This publication is one of the products of that
research and provides a vital communication link between the researcher and the
user community.
This document provides information needed to develop comprehensive quality
assurance plans and to carry out quality control procedures at waste containment
sites. It discusses quality assurance and quality control issues for compacted
soil liners, soil drainage systems, geosynthetic drainage systems, vertical
cutoff walls, ancillary materials, and appurtenances.
E. Timothy Oppelt
Director
Risk Reduction Engineering Laboratory
iii
-------
ABSTRACT
This Technical Guidance Document provides comprehensive guidance on
procedures for quality assurance and quality control for waste containment
facilities. The document includes a discussion of principles and concepts,
compacted soil liners, soil drainage systems, geosynthetic drainage systems,
vertical cutoff walls, ancillary materials, appurtenances, and other details.
The guidance document outlines critical quality assurance (QA) and quality
control (QC) issues for each major segment and recommends specific procedures,
observations, tests, corrective actions, and record keeping requirements. For
geosynthetics, QA and QC practices for both manufacturing and construction are
suggested.
The main body of the text details recommended procedures for quality
assurance and control. Appendices include a list of acronyms, glossary, and
index. A companion document was under development by the American Society for
Testing and Materials (ASTM) at the time of this writing that will contain all
of the ASTM standards referenced in this guidance document as well as most, if
not all, of the other test procedures that are referenced in this guidance
document.
This report was submitted in fulfillment of CR-815546 by the University
of Texas, Austin, under the sponsorship of the U.S. Environmental Protection
Agency. This report covers a period from June 1991 to July 1993, and work was
completed as of August 1993.
IV
-------
Table of Contents
Page No.
Disclaimer ii
Foreword iii
Abstract iv
List of Figures xii
List of Tables xix
Acknowledgments xx
Chapter 1 Manufacturing Quality Assurance (MQA) and Construction Quality 1
Assurance (CQA) Concepts and Overview
1.1 Introduction 1
1.1.1 Scope 1
1.1.2 Definitions 2
1.2 Responsibility and Authority 3
1.3 Personnel Qualifications 10
1.4 Written MQA/CQA Plan 11
1.5 Documentation 11
1.5.1 Daily Inspection Reports 11
1.5.2 Daily Summary Reports 11
1.5.3 Inspection and Testing Reports 12
1.5.4 Problem Identification and Corrective Measures Reports 13
1.5.5 Drawings of Record 13
1.5.6 Final Documentation and Certification 14
1.5.7 Document Control 14
1.5.8 Storage of Records 14
1.6 Meetings 15
1.6.1 Pre-Bid Meeting 15
1.6.2 Resolution Meeting 15
1.6.3 Pre-construction Meeting 16
1.6.4 Progress Meetings 17
1.7 Sample Custody ' 17
1.8 Weather 17
1.9 Work Stoppages 17
1.10 References 18
Chapter 2 Compacted Soil Liners 19
2.1 Introduction and Background 19
2.1.1 Types of Compacted Soil Liners 19
2.1.1.1 Natural Mineral Materials 19
-------
2.1.1.2 Bentonite-Soil Blends , 19
2.1.1.3 Other 19
2.1.2 Critical CQC and CQA Issues , ' 21
2.1.3 Liner Requirements .' 21
2.1.3.1 Subgrade Preparation 22
2.1.3.2 Material Selection 23
2.1.3.3 Preprocessing 23
2.1.3.4 Placement, Remolding, arid Compaction 24
2.1.3.5 Protection 24
2.1.3.6 Final Surface Preparation 24
2.1.4 Compaction Requirements L . , 24
2.1.4.1 Compaction Curve , , 24
2.1.4.2 Compaction Tests , 26
2.1.4.3 Percent Compaction 27
2.1.4.4 Estimating Optimum Water Content and Maximum
Dry Unit Weight 27
2.1.4.4.1 Subjective Assessment 28
2.1.4.4.2 One-Point Compaction Test 28
2.1.4.4.3 Three-Point Compaction Test (ASTM D-5080) 29
2.1.4.5 Recommended Procedure for Developing Water
Content-Density Specification , 30
2.1.5 Test Pads 34
2.2 Critical Construction Variables that Affect Soil Liners 35
2.2.1 Properties of the Soil Material 35
2.2.1.1 Plasticity Characteristics 35
2.2.1.2 Percentage Fines 37
2.2.1.3 Percentage Gravel, 38
2.2.1.4 Maximum Particle Size 39
2.2.1.5 Clay Content and Activity 39
2.2.1.6 Clod Size 39
2.2.1.7 Bentonite 40
2.2.2 Molding Water Content 42
2.2.3 Type of Compaction ' 46
2.2.4 Energy of Compaction 48
2.2.5 Bonding of Lifts . 52
2.2.6 Protection Against Desiccation and Freezing 53
2.3 Field Measurement of Water Content and Dry Unit Weight 53
2.3.1 Water Content Measurement . , 53
VI
-------
2.3.1.1 Overnight Oven Drying (ASTM D-2216) 53
2.3.1.2 Microwave Oven Drying (ASTM D-4643) 53
2.3.1.3 Direct Heating (ASTM D-4959) 54
2.3.1.4 Calcium Carbide Gas Pressure Tester (ASTM D-4944) 54
2.3.1.5 Nuclear Method (ASTM D-3017) 54
2.3.2 Unit Weight 56
2.3.2.1 Sand Cone (ASTM D-1556) 56
2.3.2.2 Rubber Balloon (ASTM D-2167) 57
2.3.2.3 Drive Cylinder (ASTM D-2937) 57
2.3.2.4 Nuclear Method (ASTM D-2922) 58
2.4 Inspection of Borrow Sources Prior to Excavation 61
2.4.1 Sampling for Material Tests 61
2.4.2 Material Tests 61
2.4.2.1 Water Content 62
2.4.2.2 Atterberg Limits 63
2.4.2.3 Particle Size Distribution 63
2.4.2.4 Compaction Curve 63
2.4.2.5 Hydraulic Conductivity 63
2.4.2.6 Testing Frequency 65
2.5 Inspection during Excavation of Borrow Soil 65
2.6 Preprocessing of Materials 67
2.6.1 Water Content Adjustment 67
2.6.2 Removal of Oversize Particles 68
2.6.3 Pulverization of Clods 68
2.6.4 Homogenizing Soils 68
2.6.5 Bentonite 68
2.6.5.1 Pugmill Mixing 70
2.6.5.2 In-Place Mixing 70
2.6.5.3 Measuring Bentonite Content 70
2.6.6 Stockpiling Soils 72
2.7 Placement of Loose Lift of Soil 72
2.7.1 Surface Scarification 73
2.7.2 Material Tests and Visual Inspection 73
2.7.2.1 Material Tests 73
2.7.2.2 Visual Observations 73
2.7.2.3 Allowable Variations 73
2.7.2.4 Corrective Abtion 75
2.7.3 Placement and Control of Loose Lift Thickness 75
vn
-------
2.8 Remolding and Compaction of Soil 76
2.8.1 Compaction Equipment 76
2.8.2 Number of Passes 77
2.8.3 Water Content and Dry Unit Weight 78
2.8.3.1 Water Content and Unit Weight Tests 78
2.8.3.2 Sampling Patterns 78
2.8.3.3 Tests with Different Devices to Minimize Systematic Errors 80
2.8.3.4 Allowable Variations and Outliers 80
2.8.3.5 Corrective Action 82
2.8.4 Hydraulic Conductivity Tests on Undisturbed Samples 82
2.8.4.1 Sampling for Hydraulic Conductivity Testing 83
2.8.4.2 Hydraulic Conductivity Testing 84
2.8.4.3 Frequency of Testing 84
2.8.4.4 Outliers 84
2.8.5 Repair of Holes from Sampling and Testing 85
2.8.6 Final Lift Thickness 85
2.8.7 Pass/Fail Decision 85
2.9 Protection of Compacted Soil 86
2.9.1 Desiccation 86
2.9.1.1 Preventive Measures 86
2.9.1.2 Observations . , 86
2.9.1.3 Tests 86
2.9.1.4 Corrective Action 86
2.9.2 Freezing Temperatures 86
2.9.2.1 Compacting Frozen Soil 86
2.9.2.2 Protection After Freezing 87
2.9.2.3 Investigating Possible Frost Damage 87
2.9.2.4 Repair 88
2.9.3 Excess Surface Water 88
2.10 Test Pads , 88
2.10.1 Purpose of Test Pads 88
2.10.2 Dimensions 89
2.10.3 Materials , 89
2.10.4 Construction 89
2.10.5 Protection 90
2.10.6 Tests and Observations 91
2.10.7 In Situ Hydraulic Conductivity 91
2.10.7.1 Sealed Double-Ring Infiltrometer 91
viii
-------
2.10.7.2 Two-Stage Borehole Test 93
2.10.7.3 Other Field Tests 95
2.10.7.4 Laboratory Tests 95
2.10.8 Documentation 95
2.11 Final Approval 95
2.12 References 95
Chapter 3 Geomembranes 99
3.1 Types of Geomembranes and Their Formulations 99
3.1.1 High Density Polyethylene (HOPE) 100
3.1.1.1 Resin 100
3.1.1.2 Carbon Black 101
3.1.1.3 Additives 103
3.1.2 Very Low Density Polyethylene (VLDPE) 103
3.1.2.1 Resin 104
3.1.2.2 Carbon Black 104
3.1.2.3 Additives 105
3.1.3 Other Extruded Geomembranes 105
3.1.4 Polyvinyl Chloride (PVC) 106
3.1.4.1 Resin 106
3.1.4.2 Plasticizer 106
3.1.4.3 Filler 107
3.1.4.4 Additives 107
3.1.5 Chlorosulfonated Polyethylene (CSPE-R) 107
3.1.5.1 -Resin 107
3.1.5.2 Carbon Black 109
3.1.5.3 Fillers 109
3.1.5.4 Additives 109
3.1.5.5 Reinforcing Scrim 109
3.1.6 Other Calendered Geomembranes 110
3.2 Manufacturing 110
3.2.1 Blending, Compounding, Mixing and/or Masticating 111
3.2.2 Regrind, Reworked or Trim Reprocessed Material 111
3.2.3 High Density Polyethylene (HOPE) 113
3.2.3.1 Hat Die-Wide Sheet 114
3.2.3.2 ' Flat Die -Factory Seamed 115
3.2.3.3 Blown Film 115
jx
-------
3.2.3.4 Textured Sheet 117
3.2.4 Very Low Density Polyethylene (VLDPE) 120
3.2.4.1 Rat Die -Wide Sheet , 120
3.2.4.2 Flat Die -Factory Seamed 120
3.2.4.3 Blown Film 12i
3.2.4.4 Textured Sheet 121
3.2.5 Coextrusion Processes 123
3.2.6 Polyvinyl Chloride (PVC) 124
3.2.6.1 Calendering 124
3.2.6.2 Panel Fabrication 127
3 .2.7 Chlorosulfonated Polyethylene-Scrim Reinforced (CSPE-R) 1 29
3.2.7.1 Calendering 129
3.2.7.2 Panel Fabrication 131
3.2.8 Spread Coated Geomembranes 131
3.3 Handling 122
3.3.1 Packaging 132
3.3.1.1 Rolls 132
3.3.1.2 Accordion Folded 133
3.3.2 Shipment, Handling and Site Storage 1 34
3.3.3 Acceptance and Conformance Testing 135
3.3.4 Placement
3.3.4.1 Subgrade (Subbase) Conditions 136
3.3.4.2 Temperature Effects - Sticking/Cracking 138
3 . 3 .4. 3 Temperature Effects - Expansion/Contraction 1 39
3.3.4.4 Spotting 140
3.3.4.5 Wind Considerations 140
3.4 Seaming and Joining 141
3.4.1 Overview of Field Seaming Methods 141
3.4.2 Details of Field Seaming Methods 145
3.4.3 Test Strips and Trial Seams 146
3.5 Destructive Test Methods for Seams 150
3.5.1 Overview 150
3.5.2 Sampling Strategies 151
3.5.2.1 Fixed Increment Sampling 151
3.5.2.2 Randomly Selected Sampling 152
-------
3.5.2.3 Other Sampling Strategies 153
3.5.3 Shear Testing of-Geomembrane Seams 153
3.5.4 Peel Testing of Geomembrane Seams 157
3.5.5 General Specification Items 160
3.6 Nondestructive Test Methods for Seams, , 161
3.6.1 Overview , 161
3.6.2 Currently Available Methods 162
3.6.3 Recommendations for Various Seam Types 165
3.6.4 General Specification Items , 165
3.7 Protection and Backfilling 167
3.7.1 Soil Backfilling of Geomembranes '• 167
3.7.2 Geosynthetic Covering of Geomembranes 170
3.7.3 General Specification Items 171
3.8 References 172
Chapter 4 Geosynthetic Clay Liners 174
4.1 Types and Composition of Geosynthetic Clay Liners 174
4.2 Manufacturing 176
4.2.1 Raw Materials 176
4.2.2 Manufacturing 177
4.2.3 Covering of the Rolls 179
4.3 Handling ' 180
4.3.1 Storage at the Manufacturing Facility 180
4.3.2 Shipment ' 181
4.3.3 Storage at the Site •; 181
4.3.4 Acceptance and Conformance Testing 184
4.4 Installation 185
4.4.1 Placement 185
4.4.2 Joining 187
4.4.3 Repairs 187
4.5 Backfilling or Covering 188
4.6 References 189
Chapters Soil Drainage Systems 191
5.1 Introduction and Background 191
5.2 Materials 191
5.3 Control of Materials 195
5.4 Location of Borrow Sources 196
xi
-------
5.5 Processing of Materials 196
5.6 Placement 197
5.6.1 Drainage Layers 197
5.6.2 Drainage Trenches 197
5.7 Compaction 19g
5.8 Protection 199
5.9 References 201
Chapter 6 Geosynthetic Drainage Systems 202
6.1 Overview 202
6.2 Geotextiles 202
6.2.1 Manufacturing of Geotextiles 202
6.2.1.1 Resins and Their Additives 204
6.2,1.2 Fiber Types 206
6.2.1.3 Geotextile Types 207
6.2.1.4 General Specification Items 207
6.2.2 Handling of Geotextiles 210
6.2.2.1 Protective Wrapping 210
6.2.2.2 Storage at Manufacturing Facility 210
6.2.2.3 Shipment 212
6.2.2.4 Storage at Field Site 212
6.2.2.5 Acceptance and Conformance Testing 212
6.2.2.6 Placement 213
6.2.3 Seaming 214
6.2.3.1 Seam Types and Procedures 214
6.2.3.2 Seam Tests 217
6.2.3.3 Repairs 217
6.2.4 Backfilling or Covering 217
6.3 Geonets and Geonet/Geotextile Geocomposites 218
6.3.1 Manufacturing of Geonets 218
6.3.2 Handling of Geonets 221
6.3.2.1 Packaging 222
6.3.2.2 Storage at Manufacturing Facility 222
6.3.2.3 Shipment 222
6.3.2.4 Storage at the Site 222
6.3.2.5 Acceptance and Conformance Testing 222
6.3.2.6 Placement 223
6.3.3 Joining of Geonets 223
Xll
-------
6.3.4 Geonet/Geotextile Geocomposites 225
6.4 Other Types of Geocomposites 226
6.4.1 Manufacturing of Drainage Composites 228
6.4.2 Handling of Drainage Geocomposites 231
6.4.2.1 Packaging 231
6.4.2.2 Storage at Manufacturing Facility 231
6.4.2.3 Shipment . 231
6.4.2.4 Storage at Field Site 231
6.4.2.5 Acceptance and Conformance Testing 231
6.4.2.6 Placement 232
6.4.3 Joining of Drainage Geocomposites 232
6.4.4 Covering 233
6.5 .References 233
Chapter? Vertical Cutoff Walls 235
7.1 Introduction 235
7.2 Types of Vertical Cutoff Walls 237
7.2.1 Sheet Pile Walls 237
7.2.2 Geomembrane Walls 238
7.2.3 Walls Constructed with Slurry Techniques 239
7.3 Construction of Slurry Trench Cutoff Walls 241
7.3.1 Mobilization 241
7.3.2 Site Preparation 241
7.3.3 Slurry Preparation and Properties 241
7.3.4 Excavation of Slurry Trench 243
7.3.5 Soil-Bentonite (SB) Backfill 244
7.3.6 Cement-Bentonite (CB) Cutoff Walls 248
7.3.7 Geomembrane in Slurry trench cutoff walls 250
7.3.8 Other Backfills 250
7.3.9 Caps , 251
7.4 Other Types of Cutoff Walls 251
7.5 Specific CQA Requirements 251
7.6 Post Construction Tests for Continuity 252
7.7 References 252
Chapters Ancillary Materials, Appurtenances, and Other Details 253
8.1 Plastic Pipe (aka "Geopipe") 253
8.1.1 Polyvinyl Chloride (PVC) Pipe 254
8.1.2 High Density Polyethylene (HOPE) Smooth Wall Pipe 256
8.1.3 High Density Polyethylene (HOPE) Corrugated Pipe 257
Xlll
-------
8.1.4 Handling of Plastic Pipe 258
8.1.4.1 Packaging 259
8.1.4.2 Storage at Manufacturing Facility 259
8.1.4.3 Shipment 259
8.1.4.4 Storage at Field Site 259
8.1.5 Conformance Testing and Acceptance 259
8.1.6 Placement 261
8.2 Sumps, Manholes and Risers 261
8.3 Liner System Penetrations 264
8.4 Anchor Trenches 266
8.4.1 Geomembranes 266
8.4.2 Other Geosynthetics 268
8.5 Access Ramps 268
8.6 Geosynthetic Reinforcement Materials 270
8.6.1 Geotextiles for Reinforcement 272
8.6.2 Geogrids 273
8.7 Geosynthetic Erosion Control Materials 275
8.8 Floating Geomembrane Covers for Surface Impoundments 278
8.9 References 280
Appendix A List of Acroynms 282
Appendix B Glossary 285
Appendix C Index 3Q1
XIV
-------
List of Figures
Figure Title __ Page NQ,
1.1 Organizational Structure of MQA/CQA Inspection Activities 4
2.1 Examples of Compacted Soil Liners in Liner and Cover Systems 20
2.2 Tie-In of New SoU Liner to Existing Soil Liner 22
2.3 Compaction Curve 25
2.4 One-Point Compaction Test 29
2.5 Form of Water Content-Dry Unit Weight Specification Often Used in the Past 30
2.6 Recommended Procedure to Determine Acceptable Zone of Water Content/
Dry Unit Weight Values Based Upon Hydraulic Conductivity Considerations 32
2.7 Acceptable Zone of Water Content/Dry Unit Weights Determined by
Superposing Hydraulic Conductivity and Shear Strength Data 33
2.8 Relationship between Hydraulic Conductivity and Plasticity Index 36
2.9 Relationship between Hydraulic Conductivity and Percent Fines 37
2.10 Relationship between Hydraulic Conductivity and Percentage Gravel Added
to Two Clayey Soils . 38
2.11 Relationship between Hydraulic Conductivity and Clay Content 40
2.12 Relationship between Clay Content and Plasticity Index 41
2.13 Effect of Addition of Bentonite to Hydraulic Conductivity of Compacted
SiltySand 42
2.14 Effect of Molding Water Content on Hydraulic Conductivity 43
2.15 Photograph of Highly Plastic Clay Compacted with Standard Proctor Effort
at a Water Content of 16% (1% Dry of Optimum) 44
2.16 Photograph of Highly Plastic Clay Compacted with Standard Proctor Effort
at a Water Content of 20% (3% Wet of Optimum) 45
2.17 Four Types of Laboratory Compaction Tests 46
2.18 Effect of Type of Compaction on Hydraulic Conductivity 47
2.19 Footed Rollers with Partly and Fully Penetrating Feet 48
2.20 Effect of Compactive Energy on Hydraulic Conductivity 49
2.21 Illustration of Why Dry Unit Weight Is a Poor Indicator of Hydraulic
Conductivity for Soil Compacted Wet of Optimum 50
2.22 Line of Optimums 51
2.23 Flow Pathways Created by Poorly Bonded Lifts 52
2.24 Schematic Diagram of Nuclear Water Content - Density Device 55
2.25 Sand Cone Device 56
2.26 Schematic Diagram of Rubber Balloon Device 58
2.27 Schematic Diagram of Drive Ring 59
2.28 Measurement of Density with Nuclear Device by (a) Direct Transmission and
(B) Backscattering 60
2.29 Recommended Procedure for Preparation of a Test Specimen Using Variable
(But Documented) Compactive Energy for Each Trial 64
2.30 Schematic Diagram of Pugmill 71
2.31 Schematic Diagram of Soil Liner Test Pad 90
2.32 Schematic Diagram of Sealed Double Ring Infiltrometer (SDRI) 91
2.33 Three Procedures for Computing Hydraulic Gradient from Infiltration Test 92
2.34 Schematic Diagram of Two-Stage Borehole Test 94
3.1 HOPE Resin Pellets 100
3.2 Carbon Black in Particulate Form and as a Concentrate 102
xv
-------
3.3 CSPE Resin Pieces 108
3.4 Photographs of Materials to be Reprocessed 112
3.5 Cross-Section Diagram of a Horizontal Single-Screw Extruder for
Polyethylene ^3
3.6 Photograph of a Polyethylene Geomembrane Exiting from a Relatively
Narrow Flat Horizontal Die 114
3.7 Photograph of Blown Film Manufacturing of Polyethylene Geomembranes
and Sketch of Blown Film Manufacturing of Polyethylene Geomembranes 116
3.8 Various Methods Currently Used to Create Textured Surfaces on HOPE
Geomembranes
3.9 Geomembrane Surface Temperature Differences Between Black and
White Colors
154
3.10 Sketches of Various Process Mixers 125
3.11 Various Types of Four-Roll Calenders 126
3.12 Photographs of Calendered Rolls of Geomembranes After Manufacturing
a i o ™d,?a?t01T Fabrication of Rolls into Large Panels for Field Deployment 128
3.13 Multiple-Ply Scrim Reinforced Geomembrane 130
3.14 Rolls of Polyethylene Awaiting Shipment to a Job Site 133
3.15 Photograph of Truck Shipment of Geomembranes 135
3.16 Photographs Showing the Unrolling (Upper) and Unfolding (Lower) of
Geomembranes J37
|-J7 HOPE Geomembrane Showing Sun Induced Wrinkles 139
3.18 Wind Damage to Deployed Geomembrane 141
3-19 Various Methods Available to Fabricate Geomembrane Seams 143
3.20 Fabrication of a Geomembrane Test Strip 147
o'?J Photograph of a Field Tensiometer Performing a Geomembrane Seam Test 148
3.22 Test Strip Process Flow Chart 149
3.23 Completed Patch on a Geomembrane Seam Which had Previously Been
Sampled for Destructive Tests 152
3.24 Shear Test of a Geomembrane Seam Evaluated in a CQC/CQA Laboratory
Environment
3.25 Peel Test of a Geomembrane Seam Evaluated in a CQC/CQA Laboratory
Environment
3.26 Advancing Primary Leachate Collection Gravel in "Fingers" Over the
Deployed Geomembrane
4'1 SnSrS Svection Sketches of Currently Available Geosynthetic Clay Liners
(vjL/LS)
4.2 Schematic Diagrams of the Manufacture of Different Types of Geosynthetic
Clay Liners (GCLs) 178
4.3 Indoor Factory Storage of Geosynthetic Clay Liners (GCLs) Waiting for
Shipment to a Job Site 180
4.4 Fork Lift Equipped with a "Stinger" and GCL Rolls on a Flat-Bed Trailer 182
4.S Photograph of Temporary Storage of GCLs in their Shipping Trailers and
at Project Site 183
4.6 Field Deployment of a GCL on a Soil Subgrade and an Underlying
Geosynthetic 186
4.7 Premature Hydration of a Geosynthetic Clay Liner Being Gathered and
Discarded due to its Exposure to Rainfall Before Covering 189
5.1 Grain Size Distribution Curve 192
5.2 Filter Layer Used to Protect Drainage Layer from Plugging 194
xvi
-------
5.3 Typical Design of a Drainage Trench 198
5.4 CQC and CQA Personnel Observing Placement of Select Waste on
Drainage Layer 200
6.1 Cross Section of a Landfill Illustrating the Use of Different Geosynthetics
Involved in Waste Containment Drainage Systems 203
6.2 Polyester Resin Chips and Carbon Black Concentrate Pellets Used for
Geotextile Fiber Manufacturing 205
6.3 Types of Polymeric Fibers Used in the Construction of Different Types of
Geotextiles 206
6.4 Three Major Types of Geotextiles 208
6.5 Photographs of Temporary Storage of Geotextiles 211
6.6 Various Types of Sewn Seams for Joining Geotextiles 215
6.7 Fabrication of a Geotextile Field Seam in a "Flat" or "Prayer" Seam Type 216
6.8 Typical Geonets Used in Waste Containment Facilities 219
6.9 Counter Rotating Die Technique for Manufacturing Drainage Geonets and
Example of Laboratory Prototype 220
6.10 Geonets Being Temporarily Stored at the Job Site 223
6.11 Photograph of Geonet Joining by Using Plastic Fasteners 224
6.12 Various Types of Drainage Geocomposites 227
6.13 Vacuum Forming System for Fabrication of a Drainage Geocomposite 229
6.14 Photograph of Drainage Core Joining via Male-to-Female Interlock 232
7.1 Example of Vertical Cutoff Wall to Limit Flow of Ground Water into
Excavation 235
7.2 Example of Vertical Cutoff Wall to Limit Flow of Ground Water through
Buried Waste 236
7.3 Example of Vertical Cutoff Wall to Restrict Inward Migration of Ground
Water 236
7.4 Example of Vertical Cutoff Wall to Limit Long-Term Contaminant Transport 236
7.5 Interlocking Steel Sheet Piles 237
7.6 Examples of Interlocks for Geomembrane Walls 238
7.7 Hydrostatic Pressure from Slurry Maintains Stable Walls of Trench 239
7.8 Diagram of Construction Process for Soil-Bentonite-Backfilled Slurry Trench
Cutoff Wall i 240
7.9 Construction of Dike to Raise Ground Surface for Construction of Slurry
Trench ... 242
7.10 Backhoe for Excavating Slurry Trench 244
7.11 Clamshell for Excavating Slurry Trench 245
7.12 Mixing Backfill with Bentonite Slurry 246
7.13 Pushing Soil-Bentonite Backfill Into Slurry Trench with Dozer 247
7.14 Examples of Problems Produced by Improper Backfilling of Slurry Trench 248
7.15 Diaphragm-Wall Construction 249
8.1 Cross Section of a Possible Removal Pipe Scheme in a Primary Leachate
Collection and Removal System 253
8.2 Plan View of a Possible Removal Pipe Scheme in a Primary Leachate
Collection and Removal System 254
8.3 Photograph of PVC Pipe to be Used in a Landfill Leachate Collection System 255
8.4 Photograph of HOPE Smooth Wall Pipe Risers Used as Primary and
Secondary Removal Systems from Sump Area to Pump and Monitoring
Station 256
XVll
-------
8.5 Photograph of HDPE Corrugated Pipe Being Coupled and After Installed 258
8.6 A Possible Buried Pipe Trench Cross Section Scheme Showing Soil Backfill
Terminology and Approximate Dimensions 262
8.7 Various Possible Schemes for Leachate Removal 263
8.8 Pipe Penetrations through Various Types of Barrier Materials 265
8.9 Various Types of Geomembrane Anchors Trenches 267
8.10 Typical Access Ramp Geometry and Cross Section 269
8.11 Geogrid or Geotextile Reinforcement of (a) Cover Soil above Waste,
(b) Leachate Collection Layer beneath Waste, and (c) Liner System Placed
above Existing Waste ("Piggybacking") 271
8.12 Photographs of Geogrids Used as Soil (or Waste) Reinforcement Materials 274
8.13 Examples of Geosynthetic Erosion Control Systems 277
8.14 Surface Impoundments with Geomembrane Floating Covers along with
Typical Details of the Support System and/or Anchor Trench and Batten Strips 279
XVlll
-------
List of Tables
Table Title ' ' Page No.
1.1 Recommended Implementation Program for Construction Quality Control
(CQC) for Geosynthetics (Beginning January 1,1993) 8
1.2 Recommended Implementation Program for Construction Quality Assurance
(CQA) for Geosynthetics (Beginning January 1,1993) 9
1.3 Recommended Personnel Qualifications 10
2.1 Compaction Test Details 26
2.2 Materials Tests 62
2.3 Recommended Minimum Testing Frequencies for Investigation of Borrow
Source 65
2.4 Criteria for Describing Dry Strength (ASTM D-2488) 66
2.5 Criteria for Describing Plasticity (ASTM D-2488) 67
2.6 Recommended Tests on Bentonite to Determine Bentonite Quality and Gradation 70
2.7 Recommended Tests to Verify Bentonite Content 72
2.8 Recommended Materials Tests for Soil Liner Materials Sampled after
Placement in a Loose Lift (Just Before Compaction) 74
2.9 Recommended Maximum Percentage of Failing Material Tests 75
2.10 Recommended Tests and Observations on Compacted Soil 79
2.11 Recommended Maximum Percentage of Failing Compaction Tests 82
3.1 Types of Commonly Used Geomembranes and Their Approximate
Weight Percentage Formulations 99
3.2 Fundamental Methods of Joining Polymeric Geomembranes 142
3.3 Possible Field Seaming Methods for Various Geomembranes Listed in
this Manual 145
3.4 Recommended Test Method Details for Geomembrane Seams in Shear and
in Peel and for Unseamed Sheet 155
3.5 Nondestructive Geomembrane Seam Testing Methods 163
3.6 Applicability Of Various Nondestructive Test Methods To Different Seam
Types And Geomembrane Types 166
3.7 Critical Cone Heights For Selected Geomembranes In Simulated Laboratory
Puncture Studies 167
3.8 Coefficients Of Thermal Expansion/Contraction Of Various Nonreinforced
Geomembrane Polymers 170
5.1 Effect of Fines on Hydraulic Conductivity of a Washed Filter Aggregate 193
5.2 Recommended Tests and Testing Frequencies for Drainage Material 196
6.1 Compounds Used in The Manufacture of Geotextiles (Values Are
Percentages Based on Weight) 204
XIX
-------
Acknowledgments
«™ -A Ti aU / Srate£ully acknowledge the following individuals and organizations who
provided many of the photographs included in this report: Stephen T. Butchko of Tensar
Environmental Systems, Inc., Richard W. Carriker of James Clem Corporation, Steven R. Day of
Geo-Con, Inc., Anthony E Eith of RUST Environmental and Infrastructure, Inc., Vito Galante of
Waste Management of North America, Inc., Gary Kolbasuk of National Seal Co., David C.
rSS? Accidental Chemical Corp., David L. Snyder of Webtec, Edward Staff, Jr., of Staff
SSSSn r°" Fred Struve £f £undle Lini*g Systems, Inc., Michael T. Taylor of JPS
Elastomencs Corp., and Dennis B. Wedding of Hoechst Celanese Corp.
m The authors wish to express their sincere appreciation to the following individuals who
SS525? MartC£Tedi ? 6a^r ^ion,of this manuscript: Craig H. Benson, Gordon P.
r£vTESlJJ n ^p^L^'t?^ ?•• Calabria'James G" CoUin'Jose D- Constantino, Steven R.
P T' ^ ^ Dlckmson' Thomas N. Dobras, Lee Embrey, Jeffrey C. Evans,
m T^Um' ^ ^mT' Janice Hal1' Bil1 Hawkins, Georg Heerten, William A
M^f ?°er?fF' °aVld CT- L^W«S. Larry D- Lydi<*, Lance Mabry, Stephen F. Maher,
Sft ^Pl™1111' clan ?ggS' Greg0ry N" ^hardson, Charles Rivette, Mark D
T a.f?r £ SPS ^r68 Stenborg' Frank Taylor, Stephen J. Trautwein, James F. Urek,
thXt ^ ^Tn^ Hv; W.yne' ?el°n R" Wilson' and John P" Workman. The authors also
thank Joseph A. Dieltz who, through the Industrial Fabrics Association International, provided
assistance in obtaining reviews of an earlier draft of this document "viucu
^n rt The authors also gratefully acknowledge the many individuals, too numerous to name here,
who over the years have shared their experiences and recommendations concerning quality
Sff ^ 1uallty control with the authors. The member organizations of the Geolynthetic
»fr^£^5TT^^6? ^ ^Sg? °f this effort' Finally'the assistance of and input by
Mr. Robert E. Landreth with the U.S. EPA is gratefully acknowledged
XX
-------
Chapter 1
Manufacturing Quality Assurance (MQA) and
Construction Quality Assurance (CQA) Concepts and Overview
1.1 Introduction
As a prelude to description of the detailed components of a waste containment facility,
some introductory comments are felt to be necessary. These comments are meant to clearly define
the role of the various parties associated with the manufacture, installation and inspection of all
components of a total liner and/or closure system for landfills, surface impoundments and waste
piles.
1.1.1 Scope
Construction quality assurance (CQA) and construction quality control (CQC) are widely
recognized as critically important factors in overall quality management for waste containment
facilities. The best of designs and regulatory requirements will not necessarily translate to waste
containment facilities that are protective of human health and the environment unless the waste
containment and closure facilities are properly constructed. Additionally, for geosynthetic
materials, manufacturing quality assurance (MQA) and manufacturing quality control (MQC) of the
manufactured product is equally important. Geosynthetics refer to factory fabricated polymenc
materials like geomembranes, geotextiles, geonets, geogrids, geosynthetic clay liners, etc.
The purpose of this document is to provide detailed guidance for proper MQA and CQA
procedures for waste containment facilities. (The document also is applicable to MQC and CQC
programs on the part of the manufacturer and contractor). Although facility designs are different,
MQA and CQA procedures are the same. In this document, no distinction is made concerning the
type of waste to be contained (e.g., hazardous or nonhazardous waste) because the MQA and CQA
procedures needed to inspect quality lining systems, fluid collection and removal systems, and
final cover systems are the same regardless of the waste type. This technical guidance document
has been written to apply to all types of waste disposal facilities, including new hazardous waste
landfills and impoundments, new municipal solid waste landfills, nonhazardous waste liquid
impoundments, and final covers for new facilities and site remediation projects.
This document is intended to aid those who are preparing MQA/CQA plans, reviewing
MQA/CQA plans, performing MQA/CQA observations and tests, and reviewing field MQC/CQC
and MQA/CQA procedures. Permitting agencies may use this document as a technical resource to
aid in the review of site-specific MQA/CQA plans and to help in identification of any deficiencies in
the MQA/CQA plan. Owner/operators and their MQA/CQA consultants may consult this document
for guidance on the plan, the process, and the final certification report. Field inspectors may use
this document and the references herein as a guide to field MQA/CQA procedures. Geosynthetic
manufacturers may use the document to help in establishing appropriate MQC procedures and as a
technical resource to explain the reasoning behind MQA procedures. Construction personnel may
use this document to help in establishing appropriate CQC procedures and as a technical resource
to explain the reasoning behind CQA procedures.
This technical guidance document is intended to update and expand EPA's Technical
Guidance Document, "Construction Quality Assurance for Hazardous Waste Land Disposal
-------
Facilities," (EPA, 1986). The scope of this document includes all natural and geosynthetic
components that might normally be used in waste containment facilities, e.g., in liner systems
fluid collection and removal systems, and cover systems.
This document draws heavily upon information presented in three EPA Technical Guidance
Documents: Design Construction, and Evaluation of Clay Liners for Waste Management
7?nioufS ?S^' 1988a)> Lining of Waste Containment and Other Impoundment Facilities"
inni \ Inspection Techniques for the Fabrication of Geomembrane Field Seams" (EPA
1991a). In addition, general technical backup information concerning many of the principles
involved in construction of liner and cover systems for waste containment facilities is provided in
two additional EPA documents: "Requirements for Hazardous Waste Landfill Design
Construction, and Closure" (EPA, 1989) and "Design and Construction of RCRA/CERCLA Final'
Covers (EPA, 1991b). Additionally, there are numerous books and technical papers in the open
literature which form a large data base from which information and reference will be drawn in the
appropriate sections.
1.1.2 Definitions
n/^o ^ ™riAtical t0 defme and understand the differences between MQC and MQA and between
CQC and CQA and to counterpoint where the different activities contrast and/or complement one
another. The following definitions are made.
• Manufacturing Quality Control (MQC): A planned system of inspections that is used to
directry monitor and control the manufacture of a material which is factory originated
MQC is normally performed by the manufacturer of geosynthetic materials and is
necessary to ensure minimum (or maximum) specified values in the manufactured
product. MQC refers to measures taken by the manufacturer to determine compliance
with the requirements for materials and workmanship as stated in certification documents
and contract plans.
• Manufacturing Quality Assurance (MQA): A planned system of activities that provides
assurance that the materials were constructed as specified in the certification documents
and contract plans. MQA includes manufacturing facility inspections, verifications,
audits and evaluation of the raw materials and geosynthetic products to assess the quality
of toe manufactured materials. MQA refers to measures taken by the MQA organization
to determine if the manufacturer is in compliance with the product certification and
contract plans for a project.
• Construction Quality Control (CQC): A planned system of inspections that is used to
directly monitor and control the quality of a construction project (EPA, 1986)
Construction quality control is normally performed by the geosynthetics installer, or for
natural soil materials by the earthwork contractor, and is necessary to achieve quality in
the constructed or installed system. Construction quality control (CQC) refers to
measures taken by the installer or contractor to determine compliance with the
requirements for materials and workmanship as stated in the plans and specifications for
the project.
• Construction Quality Assurance (CQA): A planned system of activities that provides ±e
owner and permitting agency assurance that the facility was constructed as specified in
the design (EPA, 1986). Construction quality assurance includes inspections,
verifications, audits, and evaluations of materials and workmanship necessary to
determine and document the quality of the constructed facility. Construction quality
-------
assurance (CQA) refers to measures taken by the CQA organization to assess if the
installer or contractor is in compliance with the plans and specifications for a project.
MQA and CQA are performed independently from MQC and CQC. Although MQA/CQA
and MQC/CQC are separate activities, they have similar objectives and, in a smoothly running
construction project, the processes will complement one another. Conversely, an effective
MQA/CQA program can lead to identification of deficiencies in the MQC/CQC process, but a
MQA/CQA program by itself (in complete absence of a MQC/CQC program) is unlikely to lead to
acceptable quality management. Quality is best ensured with effective MQC/CQC and MQA/CQA
programs. See Fig. 1.1 for the usual interaction of the various elements in a total inspection
program.
1.2 Responsibility and Authority
Many individuals are involved directly or indirectly in MQC/CQC and MQA/CQA
activities. The individuals, their affiliation, and their responsibilities and authority are discussed
below.
The principal organizations and individuals involved in designing, permitting, constructing,
and inspecting a waste containment facility are:
• Permitting Agency. The permitting agency is often a state regulatory agency but may
include local or regional agencies and/or the federal U. S. Environmental Protection
Agency (EPA). Other federal agencies, such as the U.S. Army Corps of Engineers, the
U.S. Bureau of Reclamation, the U.S. Bureau of Mines, etc., or their regional or state
affiliates are sometimes also involved. It is the responsibility of the permitting agency to
review the owner/operator's permit application, including the site-specific MQA/CQA
plan, for compliance with the agency's regulations and to make a decision to issue or
deny a permit based on this review. The permitting agency also has the responsibility to
review all MQA/CQA documentation during or after construction of a facility, possibly
including visits to the manufacturing facility and construction site to observe the
MQC/CQC and MQA/CQA practices, to confirm that the approved MQA/CQA plan was
followed and that the facility was constructed as specified in the design.
• Owner/Operator. This is the organization that will own and operate the disposal unit.
The owner/operator is responsible for the design, construction, and operation of the
waste disposal unit. This responsibility includes complying with the requirements of the
permitting agency, the submission of MQA/CQA documentation, and assuring the
permitting agency that the facility was constructed as specified in the construction plans
and specifications and as approved by the permitting agency. The owner/operator has
the authority to select and dismiss organizations charged with design, construction, and
MQA/CQA. If the owner and operator of a facility are different organizations, the
owner is ultimately responsible for these activities. Often the owner/operator, or owner,
will be a municipality rather than a private corporation. The interaction of a state office
regulating another state or local organization should have absolutely no impact on
procedures, intensity of effort and ultimate decisions of the MQA/CQA or MQC/CQC
process as described herein.
-------
Figure 1.1 - Organizational Structure of MQA/GQA Inspection Activities
4
-------
• Owner's Representative. The owner/operator usually has an official representative who
is responsible for coordinating schedules, meetings, and field activities. This
responsibility includes communications to other members in the owner/operator's
organization, owner's representative* permitting agency, material suppliers, general
contractor, specialty subcontractors or installers, and MQA/CQA engineer.
• Design Engineer. The design engineer's primary responsibility is to design a waste
containment facility that fulfills the operational requirements of the owner/operator,
complies with accepted design practices for waste containment facilities, and meets or
exceeds the minimum requirements of the permitting agency. The design engineer may
be an employee of the owner/operator or a design consultant hired by the
owner/operator. The design engineer may be requested to change some aspects of the
design if unexpected conditions are encountered during construction (e.g., a change in
site conditions, unanticipated logistical problems during construction, or lack of
availability of certain materials). Because design changes during construction are not
uncommon, the design engineer is often involved in the MQA/CQA process. The plans
and specifications referred to in this manual will generally be the product of the Design
Engineer. They are a major and essential part of the permit application process and the
subsequently constructed facility.
• Manufacturer. Many components, including all geosynthetics, of a waste containment
facility are manufactured materials. The manufacturer is responsible for the manufacture
of its materials and for quality control during manufacture, i.e., MQC. The minimum or
maximum (when appropriate) characteristics of acceptable materials should be specified
in the permit application. The manufacturer is responsible for certifying that its materials
conform to those specifications and any more stringent requirements or specifications
included in the contract of sale to the owner/operator or its agent. The quality control
steps taken by a manufacturer are critical to overall quality management in construction
of waste containment facilities. Such activities often take the form of process quality
control, computer-aided quality control and the like. All efforts at producing better
quality materials are highly encouraged. If requested, the manufacturer should provide
information to the owner/operator, permitting agency, design engineer, fabricator,
installer, or MQA engineer that describes the quality control (MQC) steps that are taken
during the manufacturing of the product. In addition, the manufacturer should be
willing to allow the owner/operator, permitting agency, design engineer, fabricator,
installer, and MQA engineer to observe the manufacturing process and quality control
procedures if they so desire. Such visits should be able to be made on an announced or
unannounced basis. However, such visits might be coordinated with the manufacturer
to assure that the appropriate people are present to conduct the tour and that the proper
geosynthetic is scheduled for that date so as to obtain the most information from the
visit. The manufacturer should have a designated individual who is in charge of the
MQC program and to whom questions can be directed and/or through whom visits can
be arranged. Random samples of materials should be able to be taken for subsequent
analysis and/or archiving. However, the manufacturer should retain the right to insist
that any proprietary information concerning the manufacturing of a product be held
confidential. Signed agreements of confidentiality are at the option of the manufacturer.
The owner/operator, permitting agency, design engineer, fabricator, installer, or MQA
engineer may request that they be allowed to observe the manufacture and quality control
of some or all of the raw materials and final product to be utilized on a particular job; the
manufacturer should be willing to accommodate such requests. Note that these same
comments apply to marketing organizations which represent a manufactured product
made by others, as well as the manufacturing organization itself.
-------
• Fabricator. Some materials are fabricated from manufactured components For
example, certain geomembranes are fabricated by seaming together smaller
manufactured geomembrane sheets at the fabricator's facility. The minimum
characteristics of acceptable fabricated materials are specified in the permit application
1 he fabricator is responsible for certifying that its materials conform to those
specifications and any more stringent requirements or specifications included in the
fabrication contract with the owner/operator or its agent. The quality control steps taken
by a fabricator are critical to overall quality in construction of waste containment
facilities. If requested, the fabricator should provide information to the owner/operator
permitting agency, design engineer, installer, or MQA engineer that describes the quality
control steps that are taken during the fabrication of the product. In addition, the
fabricator should be willing to allow the owner/operator, permitting agency, design
engineer, installer, or MQA engineer to observe the fabrication process and quality
control procedures if they so desire. Such visits may be made on an announced or
unannounced basis. However, such visits might be coordinated with the fabricator to
assure that the appropriate people are present to conduct the tour and that the proper
gee-synthetic is scheduled for that date so as to obtain the most information from the
visit. Random samples of materials should be able to be taken for subsequent analysis
and/or archiving. However, the fabricator should retain the right to insist that any
proprietary information concerning the fabrication of a product be held confidential
bigned agreements of confidentiality are at the option of the fabricator The
owner/operator permitting agency, design engineer, or MQA engineer may request that
they be allowed to observe the fabrication process and quality control of some or all
fabricated materials to be utilized on a particular job; the fabricator should be willing to
accommodate such a requests.
General Contractor. The general contractor has overall responsibility for construction of
a waste containment facility and for CQC during construction. The general contractor
arranges for purchase of materials that meet specifications, enters into a contract with
one or more fabricators (if fabricated materials are needed) to supply those materials
contracts with an installer (if separate from the general contractor's organization) and
has overall control over the construction operations, including scheduling and COG
I he general contractor has the primary responsibility for ensuring that a facility is
constructed in accord with the plans and specifications that have been developed by the
design engineer and approved by the permitting agency. The general contractor is also
responsible for informing the owner/operator and the MQA/CQA engineer of the
scheduling and occurrence of all construction activities. Occasionally a waste
containment facility may be constructed without a general contractor. For example an
owner/operator may arrange for all the necessary material, fabrication, and installation
contracts. In such cases, the owner/operator's representative will serve the same
tunction as the general contractor.
Installation Contractor. Manufactured products (such as geosynthetics) are placed and
installed in the field by an installation contractor who is the general contractor a
subcontractor to the general contractor, or is a specialty contractor hired directly by the
owner/operator. The installer's personnel may be employees of the owner/operator
manufacturer, or fabricator, or they may work for an independent installation company
mred by the general contractor or by the owner/operator directly. The installer is
responsible for handling, storage, placement, and installation of manufactured and/or
fabricated materials. The installer should have a CQC plan to detail the proper manner
that materials are handled, stored, placed, and installed. The installer is also responsible
for informing the owner/operator and the MQA/CQA engineer of the scheduling and
-------
occurrence of all geosynthetic construction activities.
Earthwork Contractor. The earthwork contractor is responsible for grading the site to
elevations and grades shown on the plans and for constructing earthen components of
the waste containment facility, e.g., compacted clay liners and granular drainage layers
according to the specifications. The earthwork contractor may be hired by the general
contractor or if the owner/operator serves as the general contractor, by the
owner/operator directly. In some cases, the general contractor's personnel may serve as
the earthwork contractor. The earthwork contractor is responsible not only for grading
the site to proper elevations but also for obtaining suitable earthen materials, transport
and storage of those materials, preprocessing of materials (if necessary), placement and
compaction of materials, and protection of materials during and (in some cases) after
placement. If a test pad is required, the earthwork contractor is usually responsible for
construction of the test pad. It is highly suggested that the same earthwork contractor
that constructs the test fill also construct the waste containment facility compacted clay
liner so that the experience gained from the test fill process will not be lost. Earthwork
functions must be carried out in accord with plans and specifications approved by the
permitting agency. The earthwork contractor should have a CQC plan (or agree to one
written by others) and is responsible for CQC operations aimed at controlling materials
and placement of those materials to conform with project specifications. The earthwork
contractor is also responsible for informing the owner/operator and the CQA engineer of
the scheduling and occurrence of all earthwork construction activities.
CQC Personnel .Construction quality control personnel are individuals who work for
the general contractor, installation contractor, or earthwork contractor and whose job it is
to ensure that construction is taking place in accord with the plans and specifications
approved by the permitting agency. In some cases, CQC personnel, perhaps even a
separate company, may also be part of the installation or construction crews. In other
cases, supervisory personnel provide CQC or, for large projects, separate CQC
personnel, perhaps even a separate company, may be utilized. It is recommended that a
certain portion of the CQC staff should be certified* as per the implementation schedule
of Table 1.1. The examinations have been available as of October, 1992.
MQA/CQA Engineer. The MQA/CQA engineer has overall responsibility for
manufacturing quality assurance and construction quality assurance. The engineer is
usually an individual experienced in a variety of activities although particular specialists
in soil placement, polymeric materials and geosynthetic placement will invariably be
involved in a project. The MQA/CQA engineer is responsible for reviewing the
MQA/CQA plan as well as general plans and specifications for the project so that the
MQA/CQA plan can be implemented with no contradictions or unresolved discrepancies.
Other responsibilities of the MQA/CQA engineer include education of inspection
personnel on MQA/CQA requirements and procedures and special steps that are needed
on a particular project, scheduling and coordinating of MQA/CQA inspection activities,
ensuring that proper procedures are followed, ensuring that testing laboratories are
conforming to MQA/CQA requirements and procedures, ensuring that sample custody
procedures are followed, confirming that test data are accurately reported and that test
data are maintained for later reporting, and preparation of periodic reports. The most
important duty of the MQA/CQA engineer is overall responsibility for confirming that
the facility was constructed in accord with plans and specifications approved by the
* A certification program is available from the National Institute for Certification of Engineering Technologies
(NICET); 1420 King Street; Alexandria, Virginia 22314 (phone: 703-684-2835)
-------
permitting agency. In the event of nonconformance with the project specifications or
CQA Plan, the MQA/CQA engineer should notify the owner/operator as to the details
and, if appropriate, recommend work stoppage and possibly remedial actions. The
MQA/CQA engineer is normally hired by the owner/operator and functions separately of
the contractors and owner/operator. The MQA/CQA engineer must be a registered
professional engineer who has shown competency and experience in similar projects and
is considered qualified by the permitting agency. It is recommended that the person's
resume and record on like facilities must be submitted in writing and accordingly
accepted by the permitting agency before activities commence. The permitting agency
may request additional information from the prospective MQA/CQA engineer and his/her
associated organization including experience record, education, registry and ownership
details. The permitting agency may accept or deny the MQA/CQA engineer's
qualifications based on such data and revelations. If the permitting agency requests
additional information or denies the MQA/CQA engineer's qualifications it should be
done prior to construction, so that alternatives can be made which do not negatively
impact on the progress of the work. The MQA/CQA engineer is usually required to be at
the construction site during all major construction operations to oversee MQA/CQA
personnel. The MQA/CQA engineer is usually the MQA/CQA certification engineer who
certifies the completed project.
Table 1.1 - Recommended Indentation Program for Construction Quality Control
(CQC) for Geosynthetics* (Beginning January 1,1993)
Field Crews**
At Each Site
1-4
55
End of
18 Months
(i.e., June 30, 1994)
1- Level H
1 - Level H
2 - Level I
End of
36 Months
1- Level HI***
1 - Level III***
1- Level I
"•Certification for natural materials is under development as of this writing
**Performing a Critical Operation; Typically 4 to 6 People/Crew
***Or PE with applicable experience
MQA/CQA Personnel. Manufacturing quality assurance and construction quality
assurance personnel are responsible for making observations and performing field tests
to ensure that a facility is constructed in accord with the plans and specifications
approved by the permitting agency. MQA/CQA personnel normally are employed by the
same firm as the MQA/CQA engineer, or by a firm hired by the firm employing the
MQA/CQA engineer. Construction MQA/CQA personnel report to the MQA/CQA
engineer. A relatively large proportion (if not the entire group) of the MQA/CQA staff
should be certified. Table 1.2 gives the currently recommended implementation
schedule. As mentioned previously, certification examinations have been available as of
October, 1992, from the National Institute for Certification of Engineering Technologies
in Alexandria, Virginia.
-------
Testing Laboratory. Many MQC/CQC and MQA/CQA tests are performed by
commercial laboratories. The testing laboratory should have its own internal QC plan to
ensure that laboratory procedures conform to the appropriate American Society for
Testing and Materials (ASTM) standards or other applicable testing standards. The
testing laboratory is responsible for ensuring that tests are performed in accordance with
applicable methods and standards, for following internal QC procedures, for
maintaining sample chain-of-custody records, and for reporting data. The testing
laboratory must be willing to allow the owner/operator, permitting agency, design
engineer, installer, or MQA/CQA engineer to observe the sample preparation and testing
procedures, or record-keeping procedures, if they so desire. The owner/operator,
permitting agency, design engineer, or MQA/CQA engineer may request that they be
allowed to observe some or all tests on a particular job at any time, either announced or
unannounced. The testing laboratory personnel must be willing to accommodate such a
request, but the observer should not interfere with the testing or slow the testing
process.
Table 1.2 - Recommended Implementation Program for Construction Quality Assurance
(CQA) for Geosynthetics* (Beginning January 1,1993)
No. of End of . End of
Field Crews** 18 Months 36 Months
At Each Site (i.e., June 30.1994) (i.e.. January 1.1996)
1-2 1-Level II 1-Level HI***
3-4
>5
1- Level II
1 - Level I
1- Level II
2 -Level I
1 - Level HI***
1- Level I
1 - Level HI***
1 - Level II
1- Level!
Certification for natural materials is under development as of this writing
**Performing a Critical Operation; Typically 4 to 6 People/Crew
***Or PE with applicable experience
MQA/CQA Certifying Engineer. The MQA/CQA certifying engineer is responsible for
certifying to the owner/operator and permitting agency that, in his or her opinion, the
facility has been constructed in accord with plans and specifications and MQA/CQA
document approved by the permitting agency. The certification statement is normally
accompanied by a final MQA/CQA report that contains all the appropriate
documentation, including daily observation reports, sampling locations, test results,
drawings of record or sketches, and other relevant data. The MQA/CQA certifying
engineer may be the MQA/CQA engineer or someone else in the MQA/CQA engineer's
organization who is a registered professional engineer with experience and competency
in certifying like installations.
-------
1.3 Personnel Qualifications
The key individuals involved in MQA/CQA and their minimum recommended qualifications
are listed in Table 1.3.
Table 1.3 - Recommended Personnel Qualifications
Individual
Minimum Recommended Qualifications
Design Engineer
Owner's Representative
Manufacturer/Fabricator
MQC Personnel
MQC Officer
Geosynthetic Installer's
Representative
CQC Personnel
CQA Personnel
MQA/CQA Engineer
MQA/CQA Certifying Engineer
Registered Professional Engineer
The specific individual designated by the owner with knowledge
of the project, its plans, specifications and QC/QA documents.
Experience in manufacturing, or fabricating, at least
1,000,000 m2 (10,000,000 ft2) of similar geosynthetic
materials.
Manufacturer, or fabricator, trained personnel in charge of
quality control of the geosynthetic materials to be used in the
specific waste containment facility.
The individual specifically designated by a manufacturer or
fabricator, in charge of geosynthetic material quality control.
Experience installing at least 1,000,000 m2 (10,000,000 ft2)
of similar geosynthetic materials.
Employed by the general contractor, installation contractor or
earthwork contractor involved in waste containment facilities;
certified to the extent shown in Table 1.1.
Employed by an organization that operates separately from the
contractor and the owner/operator; certified to the extent shown
in Table 1.2.
Employed by an organization that operates separately from the
contractor and owner/operator; registered Professional Engineer
and approved by permitting agency.
Employed by an organization that operates separately from the
contractor and owner/operator, registered Professional Engineer
in the state in which the waste containment facility is
constructed and approved by the appropriate permitting agency.
10
-------
1.4 Written MO A/CO A Plan
Quality assurance begins with a quality assurance plan. This includes both MQA and
CQA. These activities are never ad hoc processes that are developed while they are being
implemented. A written MQA/CQA plan must precede any field construction activities.
The MQA/CQA plan is the owner/operator's written plan for MQA/CQA activities. The
MQA/CQA plan should include a detailed description of all MQA/CQA activities that will be used
during materials manufacturing and construction to manage the installed quality of the facility. The
MQA/CQA plan should be tailored to the specific facility to be constructed and be completely
integrated into the project plans and specifications. Differences should be settled before any
construction work commences.
Most state and federal regulatory agencies require that a MQA/CQA plan be submitted by
the owner/operator and be approved by that agency prior to construction. The MQA/CQA plan is
usually part of the permit application.
A copy of the site-specific plans and specifications, MQA/CQA plan, and MQA/CQA
documentation reports should be retained at the facility by the owner/operator or the MQA/CQA
engineer. The plans, specifications, and MQA/CQA documents may be reviewed during a site
inspection by the permitting agency and will be the chief means for the facility owner/operator to
demonstrate to the permitting agency that MQA/CQA objectives for a project are being met
Written MQA/CQA plans vary greatly from project to project. No general outline or
suggested list of topics is applicable to all projects or all regulatory agencies. The elements covered
in this document provides guidance on topics that should be addressed in the written MQA/CQA
plan.
1.5 Documentation
A major purpose of the MQA/CQA process is to provide documentation for those
individuals who were unable to observe the entire construction process (e.g., representatives of the
permitting agency) so that those individuals can make informed judgments about the quality of
construction for a project. MQA/CQA procedures and results must be thoroughly documented.
1.5.1 Daily Inspection Reports
Routine daily reporting and documentation procedures should be required. Inspectors
should prepare daily written inspection reports that may ultimately be included in the final
MQA/CQA document. Copies of these reports should be available from the MQA/CQA engineer.
The daily reports should include information about work that was accomplished, tests and
observations that were made, and descriptions of the adequacy of the work that was performed.
1.5.2 Daily Summary Reports
A daily written summary report should be prepared by the MQA/CQA engineer. This
report provides a chronological framework for identifying and recording all other reports and aids
in tracking what was done and by whom. As a minimum, the daily summary reports should
contain the following (modified from Spigolon and Kelly, 1984, and EPA, 1986):
11
-------
• Date, project name, location, waste containment unit under construction, personnel
involved in major activities and other relevant identification information;
• Description of weather conditions, including temperature, cloud cover, and precipitation;
• Summaries of any meetings held and actions recommended or taken;
• Specific work units and locations of construction underway during that particular day;
• Equipment and personnel being utilized in each work task, including subcontractors;
• Identification of areas or units of work being inspected;
• Unique identifying sheet number of geomembranes for cross referencing and document
control;
• Description of off-site materials received, including any quality control data provided by
the supplier, J
• Calibrations or recalibrations of test equipment, including actions taken as a result of
recalibration;
• Decisions made regarding approval of units of material or of work, and/or corrective
actions to be taken in instances of substandard or suspect quality;
• Unique identifying sheet numbers of inspection data sheets and/or problem reporting and
corrective measures used to substantiate any MQA/CQA decisions described in the
previous item;
• Signature of the MQA/CQA engineer.
1.5.3 Inspection and Testing Reports
. observations, results of field tests, and results of laboratory tests performed on site or
off site should be recorded on a suitable data sheet. Recorded observations may take the form of
notes, charts, sketches, photographs, or any combination of these. Where possible, a checklist
may be useful to ensure that pertinent factors are not overlooked.
, , a minimum> the inspection data sheets should include the following information
(modified from Spigolon and Kelly, 1984, and EPA, 1986):
• Description or tide of the inspection activity;
• Location of the inspection activity or location from which the sample was obtained;
• Type of inspection activity and procedure used (reference to standard method when
appropriate or specific method described in MQA/CQA plan);
• Unique identifying geomembrane sheet number for cross referencing and document
control;
12
-------
• Recorded observation or test data;
• Results of the inspection activity (e.g., pass/fail); comparison with specification
requirements;
• Personnel involved in the inspection besides the individual preparing the data sheet;
• Signature of the MQA/CQA inspector and review signature by the MQA/CQA engineer.
1.5.4 Problem Identification and Corrective Measures Reports
A problem is defined as material or workmanship that does not meet the requirements of the
plans, specifications or MQA/CQA plan for a project or any obvious defect in material or
workmanship, even if there is conformance with plans, specifications and the MQA/CQA plan. As
a minimum, problem identification and corrective measures reports should contain the following
information (modified from EPA, 1986):
• Location of the problem;
• Description of the problem (in sufficient detail and with supporting sketches or
photographic information where appropriate) to adequately describe the problem;
• Unique identifying geomembrane sheet number for cross referencing and document
control;
• Probable cause;
• How and when the problem was located (reference to inspection data sheet or daily
summary report by inspector);
• Where relevant, estimation of how long the problem has existed;
• Any disagreement noted by the inspector between the inspector and contractor about
whether or not a problem exists or the cause of the problem;
• Suggested corrective measure(s);
• Documentation of correction if corrective action was taken and completed prior to
finalization of the problem and corrective measures report (reference to inspection data
sheet, where applicable);
• Where applicable, suggested methods to prevent similar problems;
• Signature of the MQA/CQA inspector and review signature of MQA/CQA engineer.
1.5.5 Drawings of Record
Drawings of record (also called "as-built" drawings) should be prepared to document the
actual lines and grades and conditions of each component of the disposal unit. For soil
components, the record drawings shall include survey data that show bottom and top elevations of
a particular component, the plan dimensions of the component, and locations of all destructive test
samples. For geosynthetic components, the record drawings often show the dimensions of all
13
-------
geomembrane field panels, the location of each panel, identification of all seams and panels with
appropriate identification numbering or lettering, location of all patches and repairs, and location of
all destructive test samples. Separate drawings are often needed to show record cross sections and
special features such as sump areas.
1.5.6 Final Documentation and Certification
At the completion of a project, or a component of a large project, the owner/operator should
submit a final report to the permitting agency. This report may include all of the daily inspection
reports, the daily MQA/CQA engineer's summary reports, inspection data sheets, problem
identification and corrective measures reports, and other documentation such as quality control
data provided by manufacturers or fabricators, laboratory test results, photographs, as-built
drawings, internal MQA/CQA memoranda or reports with data interpretation or analyses, and
design changes made by the design engineer during construction. The document should be
certified correct by the MQA/CQA certifying engineer.
The final documentation should emphasize that areas of responsibility and lines of authority
were clearly defined, understood, and accepted by all parties involved in the project (assuming that
this was the case). Signatures of the owner/operator's representative, design engineer, MQA/CQA
engineer, general contractor's representative, specialty subcontractor's representative, and
MQA/CQA certifying engineer may be included as confirmation that each party understood and
accepted the areas of responsibility and lines of authority outlined in the MQA/CQA plan.
1.5.7 Document Control
The MQA/CQA documents which have been agreed upon should be maintained under a
document control procedure. Any portion of the document(s) which are modified must be
communicated to and agreed upon by all parties involved. An indexing procedure should be
developed for convenient replacement of pages in the MQA/CQA plan, should modifications
become necessary, with revision status indicated on appropriate pages.
A control scheme should be implemented to organize and index all MQA/CQA documents.
This scheme should be designed to allow easy access to all MQA/CQA documents and should
enable a reviewer to identify and retrieve original inspection reports or data sheets for any
completed work element.
1.5.8 Storage of Records
During construction, the MQA/CQA engineer should be responsible for all MQA/CQA
documents. This includes a copy of the design criteria, plans, specifications, MQA/CQA plan, and
originals of all data sheets and reports. Duplicate records should be kept at another location to
avoid loss of this valuable information if the originals are destroyed.
Once construction is complete, the document originals should be stored by the
owner/operator in a manner that will allow for easy access while still protecting them from damage.
An additional copy should be kept at the facility if this is in a different location from the
owner/operator's main files. A final copy should be kept by the permitting agency. All
documentation should be maintained through the operating and post-closure monitoring periods of
the facility by the owner/operator and the permitting agency in an agreed upon format (paper hard
copy, microfiche, electronic medium, etc.).
14
-------
1.6 Meetings
Communication is extremely important to quality management. Quality construction is
easiest to achieve when all parties involved understand clearly their responsibility and authority.
Meetings can be very helpful to make sure that responsibility and authority of each organization is
clearly understood. During construction, meetings can help to resolve problems or
misunderstandings and to find solutions to unanticipated problems that have developed.
1.6.1 Pre-Bid Meeting
The first meeting is held to discuss the MQA/CQA plan and to resolve differences of
opinion before the project is let for bidding. The pre-bid meeting is held after the permitting
agency has issued a permit for a waste containment facility and before a construction contract has
been awarded. The pre-bid meeting is held before construction bids are prepared so that the
companies bidding on the construction will better understand the level of MQA/CQA to be
employed on the project. Also, if the bidders identify problems with the MQA/CQA plan, this
affords the owner/operator an opportunity to rectify those problems early in the process.
1.6.2 Resolution Meeting
The objectives of the resolution meeting are to establish lines of communication, review
construction plans and specifications, emphasize the critical aspects of a project necessary to ensure
proper quality, begin planning and coordination of tasks, and anticipate any problems that might
cause difficulties or delays in construction. The meeting should be attended by the
owner/operator's representative, design engineer, representatives of the general contractor and/or
major subcontractors, the MQA/CQA engineer, and the MQA/CQA certifying engineer.
The resolution meeting normally involves the following activities:
• An individual is assigned to take minutes (usually a representative of the owner/operator
or of the MQA/CQA engineer's organization);
• Individuals are introduced to one another and their responsibilities (or potential
responsibilities) are identified;
• Copies of the project plans and specifications are made available for discussion;
• The MQA/CQA plan is distributed;
• Copies of any special permit restrictions that are relevant to construction or MQA/CQA
are distributed;
• The plans and specifications are described, any unique design features are discussed (so
the contractors will understand the rationale behind the general design), any potential
construction problems are identified and discussed, and questions from any of the
parties concerning the construction are discussed;
• The MQA/CQA plan is reviewed and discussed, with the MQA/CQA engineer and
MQA/CQA certifying engineer identifying their expectations and identifying the most
critical components;
15
-------
• Procedures for MQC/CQC proposed by installers and contractors are reviewed and
discussed;
• Corrective actions to resolve potential construction problems are discussed;
• Procedures for documentation and distribution of documents are discussed;
• Each organization's responsibility, authority, and lines of communication are discussed;
• Suggested modifications to the MQA/CQA plan that would improve quality management
on the project are solicited; and
• Construction variables (e.g., precipitation, wind, temperature) and schedule are
discussed.
m It is very important that the procedures for inspection and testing be known to all, that the
criteria for pass/fail decisions be clearly defined (including the resolution of test data outliers), that
all parties understand the key problems that the MQA/CQA personnel will be particularly careful to
identify, that each individual's responsibilities and authority be understood, and that procedures
regarding resolution of problems be understood. The resolution meeting may be held in
conjunction with either the pre-bid meeting (rarely) or the pre-construction meeting (often).
1.6.3 Pre-construcrion Meeting
The pre-construction meeting is held after a general construction contract has been awarded
and the major subcontractors and material suppliers are established. It is usually held concurrent
S?*,£,(IJlti^tion of construction. The purpose of this meeting is to review the details of the
MQA/CQA plan, to make sure that the responsibility and authority of each individual is clearly
understood, to agree on procedures to resolve construction problems, and to establish a foundation
of cooperation in quality management. The pre-construction meeting should be attended by the
owner/operator's representative, design engineer, representatives of the general contractor and
major subcontractors, the MQA/CQA engineer, the MQA/CQA certifying engineer, and a
representative from the permitting agency, if that agency expects to visit the site during
construction or independently observe MQA/CQA procedures.
The pre-construction meeting should include the following activities:
• Assign an individual (usually representative of MQA/CQA engineer) to take minutes;
• Introduce parties and identify their responsibility and authority;
• Distribute the MQA/CQA plan, identify any revisions made after the resolution meeting
and answer any questions about the MQA/CQA plan, procedures, or documentation;
• Discuss responsibilities and lines of communication;
• Discuss reporting procedures, distribution of documents, schedule for any regular
meetings, and resolution of construction problems;
• Review site requirements and logistics, including safety procedures;
16
-------
• Review the design, discuss the most critical aspects of the construction, and discuss
scheduling and sequencing issues;
• Discuss MQC procedures that the geosynthetics manufacturer(s) will employ;
• Discuss CQC procedures that the installer or contractor will employ, for example,
establish and agree on geomembrane repair procedures;
• Make a list of action items that require resolution and assign responsibilities for these
items.
1.6.4 Progress Meetings
Weekly progress meetings should be held. Weekly meetings can be helpful in maintaining
lines of communication, resolving problems, identifying action items, and improving overall
quality management. When numerous critical work elements are being performed, the frequency
of these meetings can be increased to biweekly, or even daily. Persons who should attend this
meeting are those involved in the specific issues being discussed. At all times the MQA/CQA
engineer, or designated representative, should be present.
1.7 Sample Custody
All samples shall be identified as described in the MQA/CQA plan. Whenever a sample is
taken, a chain of custody record should be made for that sample. If the sample is transferred to
another individual or laboratory, records shall be kept of the transfer so that chain of custody can
be traced. The purpose of keeping a record of sample custody is to assist in tracing the cause of
anomalous test results or other testing problem, and to help prevent accidental loss of test samples.
Soil samples are usually discarded after testing. Destructive testing samples of
geosynthetic materials are often taken in triplicate, with one sample tested by CQC personnel, one
tested by CQA personnel, and the third retained in storage as prescribed in the CQA plan.
1.8 Weather
Weather can play a critical role in the construction of waste containment facilities.
Installation of all geosynthetic materials (including geosynthetic clay liners) and natural clay liners
is particularly sensitive to weather conditions, including temperature, wind, humidity, and
precipitation. The contractor or installer is responsible for complying with the contract plans and
specifications (along with the MQC/CQC plans for the various components of the system).
Included in this information should be details which restrict the weather conditions in which certain
activities can take place. It is the responsibility of the contractor or installer to make sure that these
weather restrictions are observed during construction.
1.9 Work Stoppages
Unexpected work stoppages can occur due to a variety of causes, including labor strikes,
contractual disputes, weather, QC/QA problems, etc. The MQA/CQA engineer should be
particularly careful during such stoppages to determine (1) whether in-place materials are covered
and protected from damage (e.g., lifting of a geomembrane by wind or premature hydration of
geosynthetic clay liners); (2) whether partially covered materials are protected from damage (e.g.,
desiccation of a compacted clay liners); and (3) whether manufactured materials are properly
stored and properly or adequately protected (e.g., whether geotextiles are protected from ultraviolet
17
-------
exposure). The cessation of construction should not mean the cessation of MQA/CQA inspection
and documentation. F
1.10 References
Spigolon, S.J., and M.F. Kelly (1984), "Geotechnical Assurance of Construction of Disposal
Facilities, U. S. Environmental Protection Agency, EPA 600/2-84-040, Cincinnati, Ohio.
U.S. Environmental Protection Agency (1986), "Technical Guidance Document, Construction
Quality Assurance for Hazardous Waste Land Disposal Facilities," EPA/530-SW-86-031
Cincinnati, Ohio, 88 p. '
U.S. Environmental Protection Agency (1988a), "Design, Construction, and Evaluation of Clay
Liners for Waste Management Facilities," EPA/530-SW-86-007F, Cincinnati, Ohio.
U.S. Environmental Protection Agency (1988b), "Lining of Waste Containment and Other
Impoundment Facilities," EPA/600/2-88/052, Cincinnati, Ohio.
U. S. Environmental Protection Agency (1989), "Requirements for Hazardous Waste Landfill
Design, Construction, and Closure," EPA/625/4-89/022, Cincinnati, Ohio.
U.S. Environmental Protection Agency (1991a), "Inspection Techniques for the Fabrication of
Geomembrane Field Seams," EPA/530/SW-91/051, Cincinnati, Ohio.
and Consmction of
18
-------
Chapter 2
Compacted Soil Liners
2.1 Introduction and Background
2.1.1 Types of Compacted Soil Liners
Compacted soil liners have been used for many years as engineered hydraulic barriers for
waste containment facilities. Some liner and cover systems contain a single compacted soil liner,
but others may contain two or more compacted soil liners. Compacted soil liners are frequently
used in conjunction with geomembranes to form a composite liner, which usually consists of a
geomembrane placed directly on the surface of a compacted soil liner. Examples of soil liners used
in liner and cover systems are shown in Fig. 2.1.
Compacted soil liners are composed of clayey materials that are placed and compacted in
layers called lifts. The materials used to construct soil liners include natural mineral materials
(natural soils), bentonite-soil blends, and other material
2.1.1.1 Natural Mineral Materials
The most common type of compacted soil liner is one that is constructed from naturally
occurring soils that contain a significant quantity of clay. Soils are usually classified as CL, CH,
or SC soils in the Unified Soil Classification System (USCS) and ASTM D-2487. Soil liner
materials are excavated from locations called borrow pits. These borrow areas are located either on
the site or offsite. The soil in the borrow pit may be used directly without processing or may be
processed to alter the water content, break down large pieces of material, or remove oversized
particles. Sources of natural soil liner materials include lacustrine deposits, glacial tills, aeolian
materials, deltaic deposits, residual soils, and other types of soil deposits. Weakly cemented or
highly weathered rocks, e.g., mudstones and shales, can also be used for soil liner materials,
provided they are processed properly.
2.1.1.2 Bentonite-Soil Blends
If the soils found in the vicinity of a waste disposal facility are not sufficiently clayey to be
suitable for direct use as a soil liner material, a common practice is to blend natural soils available
on or near a site with bentonite. The term bentonite is used in different ways by different people.
For purposes of this discussion, bentonite is any commercially processed material that is composed
primarily of the mineral smectite. Bentonite may be supplied in granular or pulverized form. The
dominant adsorbed cation of commercial bentonite is usually sodium or calcium, although the
sodium form is much more commonly used for soil sealing applications. Bentonite is mixed with
native soils either in thin layers or in a pugmill.
2.1.1.3 Other
Other materials have occasionally been used for compacted soil liners. For example,
bentonite may be blended with flyash to form a liner under certain circumstances. Modified soil
minerals and commercial additives, e.g., polymers, have sometimes been used.
19
-------
TYPICAL LINER SYSTEMS
Single Composite Liner:
Geomembrane
Composite
Liner
Double Composite Liner:
Primary
Composite -
Liner
Leak Detection -
Secondary
Composite -
Liner
Geomembrane
Low-Permeability
Compacted Soil Liner
- Soil or Geotextlle Filter
Drainage Material
(Geosynthetlc or
Granular Soli)
Geomembrane
Low-Permeability
Compacted Soil Liner
TYPICAL COVER SYSTEM
Top Soil
Soil or Geotextile Filter
Drainage Layer
Geomembrane
Low Permeability
Compacted Soil
Liner
Waste
Figure 2.1 - Examples of Compacted Soil Liners in Liner and Cover Systems
20
-------
2.1.2 Critical COG and COA Issues
The CQC and CQA processes for soil liners are intended to accomplish three objectives:
1. Ensure that soil liner materials are suitable.
2. Ensure that soil liner materials are properly placed a. ^ compacted.
3. Ensure that the completed liner is properly protected.
Some of these issues, such as protection of the liner from desiccation after completion, simply
require application of common-sense procedures. Other issues, such preprocessing of materials,
are potentially much more complicated because, depending on the material, many construction
steps may be involved. Furthermore, tests alone will not adequately address many of the critical
CQC and CQA issues -- visual observations by qualified personnel, supplemented by intelligently
selected tests, provide the best approach to ensure quality in the constructed soil liner.
As discussed in Chapter 1, the objective of CQA is to ensure that the final product meets
specifications. A detailed program of tests and observations is necessary to accomplish this
objective. The objective of CQC is to control the manufacturing or construction process to meet
project specifications. With geosynthetics, the distinction between CQC and CQA is obvious: the
geosynthetics installer performs CQC while an independent organization conducts CQA.
However, CQC and CQA activities for soils are more closely linked than in geosynthetics
installation. For example, on many earthwork projects the CQA inspector will typically determine
the water content of the soil and report the value to the contractor; in effect, the CQA inspector is
also providing CQC input to the contractor. On some projects, the contractor is required to
perform extensive tests as part of the CQC process, and the CQA inspector performs tests to check
or confirm the results of CQC tests.
The lack of clearly separate roles for CQC and CQA inspectors in the earthwork industry is
a result of historic practices and procedures. This chapter is focused on CQA procedures for soil
liners, but the reader should understand that CQA and CQC practices are often closely linked in
earthwork. In any event, the QA plan should clearly establish QA procedures and should consider
whether there will be QC tests and observations to complement the QA process.
2.1.3 Liner Requirements
The construction of soil liners is a challenging task that requires many careful steps. A
blunder concerning any one detail of construction can have disastrous impacts upon the hydraulic
conductivity of a soil liner. For example, if a liner is allowed to desiccate, cracks might develop
that could increase the hydraulic conductivity of the liner to above the specified requirement
As stated in Section 2.1.2, the CQC and CQA processes for soil liners essentially consist
of using suitable materials, placing and compacting the materials properly, and protecting the
completed liner. The steps required to fulfill these requirements may be summarized as follows:
1. The subgrade on which the soil liner will be placed should be properly prepared.
2. The materials employed in constructing the soil liner should be suitable and should
conform to the plans and specifications for the project.
21
-------
4.
5.
6.
3. The soil liner material should be preprocessed, if necessary, to adjust the water
content, to remove oversized particles, to break down clods of soil, or to add
amendments such as bentonite.
The soil should be placed in lifts of appropriate thickness and then be properly
remolded and compacted.
The completed soil liner should be protected from damage caused by desiccation or
freezing temperatures.
The final surface of the soil liner should be properly prepared to support the next
layer that will be placed on top of the soil liner.
The six steps mentioned above are described in more detail in the succeeding subsections to
provide the reader with a general introduction to the nature of CQC and CQA for soil liners.
Detailed requirements are discussed later.
2.1.3.1 Subgrade Preparation
The subgrade on which a soil liner is placed should be properly prepared, i.e., provide
adequate support for compaction and be free from mass movements. The compacted soil liner may
be placed on a natural or geosynthetic material, depending on the particular design and the
individual component in the liner or cover system. If the soil liner is the lowest component of the
liner system, native soil or rock forms the subgrade. In such cases the subgrade should be
compacted to eliminate soft spots. Water should be added or removed as necessary to produce a
suitably firm subgrade per specification requirements. In other instances the soil liner may be
placed on top of geosynthetic components of the liner system, e.g., a geotextile. In such cases, the
main concern is the smoothness of the geosynthetic on which soil is placed and conformity of the
geosynthetic to the underlying material (e.g., no bridging over ruts left by vehicle traffic).
Sometimes it is necessary to "tie in" a new section of soil liner to an old one, e.g., when a
landfill is being expanded laterally. It is recommended that a lateral excavation be made about 3 to
6 m (10 to 20 ft) into the existing soil liner, and that the existing liner be stair-stepped as shown in
Fig. 2.2 to tie the new liner into the old one. The surface of each of the steps in the old liner
should be scarified to maximize bonding between the new and old sections.
New Section of Soil Liner
"Stair-Step" Cut Made into
Old Section of Liner to Tie In
New Liner with Old Liner
Old Section of Soil Liner
Figure 2.2 - Tie-In of New Soil Liner to Existing Soil Liner
22
-------
2.1.3.2 Material Selection
Soil liner materials are selected so that a low hydraulic conductivity will be produced after
the soil is remolded and compacted. Although the performance specification is usually hydraulic
conductivity, CQA considerations dictate that restrictions be placed on certain properties of the soil
used to build a liner. For example, limitations may be placed on the liquid limit, plastic limit,
plasticity index, percent fines, and percent gravel allowed in the soil liner material.
The process of selecting construction materials and verifying the suitability of the materials
varies from project to project. In general, the process is as follows:
1. A potential borrow source is located and explored to determine the vertical and
lateral extent of the source and to obtain representative samples, which are tested for
properties such as liquid limit, plastic limit, percent fines, etc.
2. Once construction begins, additional CQC and CQA observations and tests may be
performed in the borrow pit to confirm the suitability of materials being removed.
3. After a lift of soil has been placed, additional CQA tests should be performed for
final verification of the suitability of the soil liner materials.
On some projects, the process may be somewhat different. For example, a materials company may
offer to sell soil liner materials from a commercial pit, in which case the first step listed above
(location of borrow source) is not relevant.
A variety of tests is performed at various stages of the construction process to ensure that
the soil liner material conforms with specifications. However, tests alone will not necessarily
ensure an adequate material — observations by qualified CQA inspectors are essential to confirm
that deleterious materials (such as stones or large pieces of organic or other deleterious matter) are
not present in the soil liner material.
2.1.3.3 Preprocessing
Some soil liner materials must be processed prior to use. The principal preprocessing steps
that may be required include the following:
1. Drying of soil that is too wet.
2. Wetting of soil that is too dry.
3. Removal of oversized particles.
4. Pulverization of clods of soil.
5. Homogenization of nonuniform soil.
6. Addition of bentonite.
Tests are performed by CQA personnel to confirm proper preprocessing, but visual observations
by CQC and CQA personnel are needed to confirm that proper procedures have been followed and
that the soil liner material has been properly preprocessed.
23
-------
2.1.3.4 Placement Remolding, and Compaction
Soil liners are placed and compacted in lifts. The soil liner material must first be placed in a
loose lift of appropriate thickness. If a loose lift is too thick, adequate compactive energy may not
be delivered to the
The ^Pe and wei§ht of compaction equipment can have an important influence upon the
hydraulic conductivity of the constructed liner. The CQC/CQA program should be designed to
ensure that the soil liner material will be properly placed, remolded, and compacted as described in
the plans and specifications for the project.
2.1.3.5 Protection
The completed soil liner must be protected from damage caused by desiccation or freezing
temperatures. Each completed lift of the soil liner, as well as the completed liner must be
protected.
2.1.3.6 Final Surface Preparation
The surface of the liner must be properly compacted and smoothed to serve as a foundation
lor an overlying geomembrane liner or other component of a liner or cover system. Verification of
final surface preparation is an important part of the CQA process.
2.1.4 Compaction Requirements
One of the most important aspects of constructing soil liners that have low hydraulic
conductivity is the proper remolding and compaction of the soil. Background information on soil
compaction is presented in this subsection.
2.1.4.1 Compaction Curve
A compaction curve is developed by preparing several samples of soil at different water
contents and then sequentially compacting each of the samples into a mold of known volume with a
specified compaction procedure. The total unit weight (y), which is also called the wet density of
each specimen is determined by weighing the compacted specimen and dividing the total weight by
the total volume. The water content (w) of each compacted specimen is determined by oven drying
*ej specimen. The dry unit weight (yd), which is sometimes called the dry density, is calculated as
(2.1)
The (w, yd) points are plotted and a smooth curve is drawn between the points to define the
compaction curve (Fig. 2.3). Judgment rather than an analytic algorithm is usually employed to
draw the compaction curve through the measured points.
The maximum dry unit weight (yd,max) occurs at a water content that is called the optimum
water content, wopt (Fig. 2.3). The main reason for developing a compaction curve is to determine
the optimum water content and maximum dry unit weight for a given soil and compaction
24
-------
WEIGHT-VOLUME TERMINOLOGY
Weights Volumes
W
Ws
Air
tWaterS
f f f f
V V V V
Solids.
Vs
w
Ww
Ws
O)
1
d.max
COMPACTION CURVE
Maximum Dry
Unit Weight
Zero Air Voids Curve
Optimum
Water
Content
w
opt
Molding Water Content (w)
Figure 2.3 - Compaction Curve
The zero air voids curve (Fig. 2.3), also known as the 100% saturation curve, is a curve
that relates dry unit weight to water content for a saturated soil that contains no air. The equation
for the zero air voids curve is:
25
-------
Yd = Yw/[w + (1/GS)]
(2.2)
where Gs is the specific gravity of solids (typically 2.6 to 2.8) and yw is the unit weight of water.
If the soil's specific gravity of solids changes, the zero air voids curve will also change.
Theoretically, no points on a plot of dry unit weight versus water content should lie above the zero
air voids curve, but in practice some points usually lie slightly above the zero air voids curve as a
result of soil variability and inherent limitations in the accuracy of water content and unit weight
measurements (Schmertmann, 1989).
Benson and Boutwell (1992) summarize the maximum dry unit weights and optimum water
content measured on soil liner materials from 26 soil liner projects and found that the degree of
saturation at the point of (wopt, y d,max) ranged from 71% to 98%, based on an assumed Gs value
of 2.75. The average degree of saturation at the optimum point was 85%.
2.1.4.2 Compaction Tests
Several methods of laboratory compaction are commonly employed. The two procedures
that are most commonly used are standard and modified compaction. Both techniques usually
involve compacting the soil into a mold having a volume of 0.00094 m3 (1/30 ft3). The number of
lifts, weight of hammer, and height of fall are listed in Table 2.1. The compaction tests are
sometimes called Proctor tests after Proctor, who developed the tests and wrote about the
procedures in several 1933 issues of Engineering News Record. Thus, the compaction curves are
sometimes called Proctor curves, and the maximum dry unit weight may be termed the Proctor
density.
Table 2.1 - Compaction Test Details
Procedure
Standard
Modified
Number
of Lifts
3
5
Weight of
Hammer
24.5N
(5.5 Ibs)
44.5N
(10 Ibs)
Height of
Fall
305mm
(12 in.)
457 mm
(18 in.)
Compactive
594 kN-m/m3
(12,375 ft-lb/ft3)
2,693 kN-m/m3
(56,250 ft-lb/ft3)
Proctor's original test, now frequently called the standard Proctor compaction test, was
developed to control compaction of soil bases for highways and airfields. The maximum dry unit
weights attained from the standard Proctor compaction test were approximately equal to unit
weights observed in the field on well-built fills using compaction equipment available in the 1920s
and 1930s. During World War II, much heavier compaction equipment was developed and the
unit weights attained from field compaction sometimes exceeded the laboratory values. Proctor's
original procedure was modified by increasing compactive energy. By today's standards:
26
-------
• Standard Compaction (ASTM D-698) produces maximum dry unit weights
approximately equal to field dry unit weights for soils that are well compacted using
modest-sized compaction equipment.
• Modified Compaction (ASTM D-1557) produces maximum dry unit weights
approximately equal to field dry unit weights for soils that are well compacted using the
heaviest compaction equipment available.
2.1.4.3 Percent Compaction
The compaction test is used to help CQA personnel to determine: 1) whether the soil is at
the proper water content for compaction, and 2) whether the soil has received adequate compactive
effort. Field CQA personnel will typically measure the water content of the field-compacted soil
(w) and compare that value with the optimum water content (w0pt) from a laboratory compaction
test. The construction specifications may limit the value of w relative to w0pt, e.g., specifications
may require w to be between 0 and +4 percentage points of w0po Field CQC personnel should
measure the water content of the soil prior to remolding and compaction to ensure that the material
is at the proper water content before the soil is compacted. However, experienced earthwork
personnel can often tell if the soil is at the proper water content from the look and feel of the soil.
Field CQA personnel should measure the water content and unit weight after compaction to verify
that the water content and dry unit weight meet specifications. Field CQA personnel often compute
the percent compaction, P, which is defined as follows:
P = Yd/Yd,maxxlOO% (2.3)
where Yd is the dry unit weight of the field-compacted soil. Construction specifications often
stipulate a minimum acceptable value of P.
In summary, the purpose of the laboratory compaction test as applied to CQC and CQA is
to provide water content (w0pt) and dry unit weight (Yd.max) reference points. The actual water
content of the field-compacted soil liner may be compared to the optimum value determined from a
specified laboratory compaction test. If the water content is not in the proper range, the
engineering properties of the soil are not likely to be in the range desired. For example, if the soil
is too wet, the shear strength of the soil may be too low. Similarly, the dry unit weight of the
field-compacted soil may be compared to the maximum dry unit weight determined from a
specified laboratory compaction test. If the percent compaction is too low, the soil has probably
not been adequately compacted in the field. Compaction criteria may also be established in ways
that do not involve percent compaction, as discussed later, but one way or another, the laboratory
compaction test provides a reference point.
2.1 A A Estimating Optimum Water Content and Maximum Dry Unit Weight
Many CQA plans require that the water content and dry unit weight of the field-compacted
soil be compared to values determined from laboratory compaction tests. Compaction tests are a
routine part of nearly all CQA programs. However, from a practical standpoint, performing
compaction tests introduces two problems:
1. A compaction test often takes 2 to 4 days to complete ~ field personnel cannot wait
for the completion of a laboratory compaction test to make "pass-fail" decisions.
27
-------
2. The soil will inevitably be somewhat variable — the optimum water content and
maximum dry unit weight will vary. The values of w0pt and Yd,max appropriate for
one location may not be appropriate for another location. This has been termed a
"mismatch" problem (Noorany, 1990).
Because dozens (sometimes hundreds) of field water content and density tests are
performed, it is impractical to perform a laboratory compaction test each and every time a field
measurement of water content and density is obtained. Alternatively, simpler techniques for
estimating the maximum dry unit weight are almost always employed for rapid field CQA
assessments. These techniques are subjective assessment, one-point compaction test, and three-
point compaction test.
2.1.4.4.1 Subjective Assessment
Relatively homogeneous fill materials produce similar results when repeated compaction
tests are performed on the soil. A common approach is to estimate optimum water content and
maximum dry unit weight based on the results of previous compaction tests. The results of at least
2 to 3 laboratory compaction tests should be available from tests on borrow soils prior to actual
compaction of any soil liner material for a project. With subjective assessment, CQA personnel
estimate the optimum water content and maximum dry unit weight based upon the results of the
previously-completed compaction tests and their evaluation of the soil at a particular location in the
field. Slight variations in the composition of fill materials will cause only slight variations in wopt
and Yd,max- As an approximate guide, a relatively homogeneous borrow soil would be considered
a material in which Wopt does not vary by more than ± 3 percentage points and Yd,max does not
vary by more than ± 0.8 kN/ft3 (5 pcf). The optimum water content and maximum dry unit
weight should not be estimated in this manner if the soil is heterogeneous - too much guess work
and opportunity for error would exist.
2.1.4.4.2 One-Point Compaction Test
The results of several complete compaction tests should always be available for a particular
borrow source prior to construction, and the data base should expand as a project progresses and
additional compaction tests are performed. The idea behind a one-point compaction test is shown
in Fig. 2.4. A sample of soil is taken from the field and dried to a water content that appears to be
just dry of optimum. An experienced field technician can usually tell without much difficulty when
the water content is just dry of optimum. The sample of soil is compacted into a mold of known
volume according to the compaction procedure relevant to a particular project, e.g., ASTM D-698
or D-1557. The weight of the compacted specimen is measured and the total unit weight is
computed. The sample is dried using one of the rapid methods of measurement discussed later to
determine water content. Dry unit weight is computed from Eq. 2.2. The water content-dry unit
weight point from the one-point compaction test is plotted as shown in Fig. 2.4 and used in
conjunction with available compaction curves to estimate wopt and Yd,max- One assumes that the
shape of the compaction is similar to the previously-developed compaction curves and passes
through the one point that has been determined.
The dashed curve in Fig. 2.4 is the estimated compaction curve. The one-point compaction
test is commonly used for variable soils. In extreme cases, a one-point compaction test may be
required for nearly all field water content and density measurements for purposes of computing
percent compaction. However, if the material is so variable to require a one-point compaction test
for nearly all field density measurements, the material is probably too variable to be suitable for use
in a soil liner. The best use of the one-point compaction test is to assist with estimation of the
optimum water content and maximum dry unit weight for questionable materials and to fill in data
28
-------
gaps when results of complete compaction tests are not available quickly enough.
t
_o»
"3
Previously-Developed
Compaction Curve
Result of One-Point
Compaction Test
Estimated Yd.
Assumed Compaction
Curve
Previously-Developed
Compaction Curve
Estimated w,
'opt
Water Content
Figure 2.4 - One-Point Compaction Test
2.1.4.4.3 Three-Point Compaction Test (ASTM D-SOSOt
A more reliable technique than the one-point compaction test for estimating the optimum
water content and maximum dry unit weight is to use a minimum of three compaction points to
define a curve rather than relying on a single compaction point. A representative sample of soil is
obtained from the field at the same location where the in-place water content and dry unit weight
have been measured. The first sample of soil is compacted at the field water content. A second
sample is prepared at a water content two percentage points wetter than the first sample and is
compacted. However, for extremely wet soils that are more than 2% wet of optimum (which is
often the case for soil liner materials), the second sample should be dried 2% below natural water
content. Depending on the outcome of this compaction test, a third sample is prepared at a water
content either two percentage points dry of the first sample or two percentage points wet of the
second sample (or, for wet soil liners, 2 percentage points dry of the second sample). A parabola
29
-------
is fitted to the three compaction data points and the optimum water content and maximum dry unit
weight are determined from the equation of the best-fit parabola. This technique is significantly
more time consuming than the one-point compaction test but offers 1) a standard ASTM procedure
and 2) greater reliability and repeatabiUty in estimated wopt and Yd^
2.1.4.5 Recommended Procedure for Developing Water Content-Density Specification
One of the most important aspects of CQC and CQA for soil liners is documentation of the
water content and dry unit weight of the soil immediately after compaction. Historically, the
method used to specify water content and dry unit weight has been based upon experience with
structural fill. Design engineers often require that soil liners be compacted within a specified range
of water content and to a minimum dry unit weight. The "Acceptable Zone" shown in Fig. 2.5
represents the zone of acceptable water content/dry unit weight combinations that is often
prescribed. The shape of the Acceptable Zone shown in Fig. 2.5 evolved empirically from
construction practices applied to roadway bases, structural fills, embankments, and earthen dams.
The specification is based primarily upon the need to achieve a minimum dry unit weight for
adequate strength and limited compressibility. As discussed by Mundell and Bailey (1985),
Boutwell and Hedges (1989), and Daniel and Benson (1990), this method of specifying water
content and dry unit weight is not necessarily the best method for compacted soil liners.
Zero Air Voids Curve
I
Q
Acceptable Zone
d.max
PY
d.max — — —-/— — — —
Molding Water Content (w)
Figure 2.5 - Form of Water Content-Dry Unit Weight Specification Often Used in the Past
30
-------
; The recommended approach is intended to ensure that the soil liner will be compacted to a
water content and dry unit weight that will lead to low hydraulic conductivity and adequate
engineering performance with respect to other considerations, e.g., shear strength. Rational
specification of water content/dry unit weight criteria should be based upon test data developed for
each particular soil. Field test data, would be better than laboratory data^ but the cost of determining
compaction criteria in the field through a series of test sections would almost always be prohibitive.
Because the compactive effort will vary in the field, a logical approach is to select several
compactive efforts in the laboratory that span the range of compactive effort that might be
anticipated in the field. If this is done, the water content/dry unit weight criterion that evolves
would be expected to apply to any reasonable compactive effort.
For most earthwork projects, modified Proctor effort represents a reasonable upper limit on
the compactive effort likely to be delivered to the soil in the field. Standard compaction effort
(ASTM D-698) likely represents a medium compactive effort. It is conceivable that soil in some
locations will be compacted with an effort less than that of standard Proctor compaction. A
reasonable lower limit, of compactive energy is the "reduced completion" procedure in which
standard compaction procedures (ASTM D-698) are followed except that only 15 drops of the
hammer per liftare used instead of the usual 25 drops. The reduced compaction procedure is the
same as the 15 blow compaction test described by the U.S. Army Corps of Engineers (1970). The
reduced compactive effort is expected to correspond to a reasonable minimum level of compactive
energy for a typical soil liner or cover. Other compaction methods, e.g., kneading compaction,
could be used. The key is to span the range of compactive effort expected in the field with
laboratory compaction procedures.
j-t
One satisfactory approach is as follows:
1. Prepare and compact soil in the laboratory with modified, standard, and reduced
compaction procedures to develop compaction curves as shown in Fig. 2.6a. Make
sure that the soil preparation procedures are appropriate; factors such as clod size
reduction may influence the results (Benson and Daniel, 1990). Other compaction
procedures can be used if they better simulate field compaction and span the range
of compactive effort expected in the field. Also, as few as two compaction
procedures can be used if field construction procedures make either the lowest or
highest compactive energy irrelevant.
2. The compacted specimens should be permeated, e.g., per ASTM D-5084. Care
should be taken to ensure that permeation procedures are correct, with important
details such as degree of saturation and effective confining stress carefully selected.
The measured hydraulic conductivity should be plotted as a function of molding
water content as shown in Fig. 2.6b.
3. As shown in Fig. 2.6c, the dry unit weight/water content points should be replotted
with different symbols used to represent compacted specimens that had hydraulic
conductivities greater than the maximum acceptable value and specimens with
hydraulic conductivities less than or equal to the maximum acceptable value. An
"Acceptable Zone" should be drawn to encompass the data points representing test
results meeting or exceeding the design criteria. Some judgment is usually
necessary in constructing the Acceptable Zone from the data points. Statistical
criteria (e.g., Boutwell and Hedges, 1989) may be introduced at this stage.
31
-------
The Acceptable Zone should be modified (Fig. 2.6d) based on other considerations
such as shear strength. Additional tests are usually necessary in order to define the
acceptable range of water content and dry unit weight that satisfies both hydraulic
conductivity and shear strength criteria. Figure 2.7 illustrates how one might
overlap Acceptable Zones defined from hydraulic conductivity and shear strength
considerations to define a single Acceptable Zone. The same procedure can be
applied to take into consideration other factors such as shrink/swell potential
relevant to any particular project.
IS
5
.H
1
—O i
Maximum
Allowable
V4ue
y_
(B)
Molding Water Content
Molding Water Content
I
Acceptable
Zone
5
Modified
Acceptable
Zone
Molding Water Content
Molding WaterContent
Figure 2.6 - Recommended Procedure to Determine Acceptable Zone of Water Content/Dry Unit
Weight Values Based Upon Hydraulic Conductivity Considerations (after Daniel and
Benson, 1990).
32
-------
x:
o>
as
Acceptable Zone
Based on Shear
Strength Criterion
Overall Acceptable Zone
Based on All Criteria
Acceptable Zone
Based on Hydraulic
Conductivity Criterion
Molding Water Content
Figure 2.7 - Acceptable Zone of Water Content/Dry Unit Weights Determined by Superposing
Hydraulic Conductivity and Shear Strength Data (after Daniel and Benson, 1990).
The same general procedure just outlined may also be used for soil-bentonite mixtures.
However, to keep the scope of testing reasonable, the required amount of bentonite should be
determined before the main part of the testing program is initiated. The recommended procedure
for soil-bentonite mixes may be summarized as follows:
1. The type, grade, and gradation of bentonite that will be used should be determined.
-j This process usually involves estimating costs from several potential suppliers. A
sufficient quantity of the bentonite likely to be used for the project should be
obtained and tested to characterize the bentonite (characterization tests are discussed
later).
., '", , 2., A representative sample of the soil to which the bentonite will be added should be
obtained.
33
-------
3. Batches of soil-bentonite mixtures should be prepared by blending in bentonite at
several percentages, e.g., 2%, 4%, 6%, 8%, and 10% bentonite. Bentonite content
is defined as the weight or mass of bentonite divided by the weight or mass of soil
mixed with bentonite. For instance, if 5 kg of bentonite are mixed with 100 kg of
soil, the bentonite content is 5%. Some people use the gross weight of bentonite
rather than oven dry weight. Since air-dry bentonite usually contains 10% to 15%
hygroscopic water by weight, the use of oven-dry, air-dry, or damp weight can
make a difference in the percentage. Similarly, the weight of soil may be defined as
either moist or dry (air- or oven-dry) weight. The contractor would rather work
with total (moist) weights since the materials used in forming a soil-bentonite blend
do contain some water. However, the engineering characteristics are controlled by
the relative amounts of dry materials. A dry-weight basis is generally
recommended for definition of bentonite content, but CQC and CQA personnel
must recognize that the project specifications may or may not be on a dry-weight
basis.
4. Develop compaction curves for each soil-bentonite mixture prepared from Step 3
using the method of compaction appropriate to the project, e.g., ASTM D-698 or
ASTMD-1557.
5. Compact samples at 2% wet of optimum for each percentage of bentonite using the
same compaction procedure employed in Step 4.
6. Permeate the soils prepared from Step 5 using ASTM D-5084 or some other
appropriate test method. Graph hydraulic conductivity versus percentage of
bentonite.
7. Decide how much bentonite to use based on the minimum required amount
determined from Step 6. The minimum amount of bentonite used in the field
should always be greater than the minimum amount suggested by laboratory tests
because mixing in the field is usually not as thorough as in the laboratory.
Typically, the amount of bentonite used in the field is one to four percentage points
greater than the minimum percent bentonite indicated by laboratory tests.
8. A master batch of material should be prepared by mixing bentonite with a
representative sample of soil at the average bentonite content expected in the field.
The procedures described earlier for determining the Acceptable Zone of water
content and dry unit weight are then applied to the master batch.
2.1.5 Test Pads
Test pads are sometimes constructed and tested prior to construction of the full-scale
compacted soil liner. The test pad simulates conditions at the time of construction of the soil liner.
If conditions change, e.g., as a result of emplacement of waste materials over the liner, the
properties of the liner will change in ways that are not normally simulated in a test pad. The
objectives of a test pad should be as follows:
1. To verify that the materials and methods of construction will produce a compacted
soil liner that meets the hydraulic conductivity objectives defined for a project,
hydraulic conductivity should be measured with techniques that will characterize the
large-scale hydraulic conductivity and identify any construction defects that cannot
be observed with small-scale laboratory hydraulic conductivity tests.
34
-------
2. To verify that the proposed CQC and CQA procedures will result in a high-quality
soil liner that will meet performance objectives.
* ', , '
3. To provide a basis of comparison for full-scale CQA: if the test pad meets the
performance objectives - for the liner (as verified by appropriate hydraulic
conductivity tests) and the full-scale liner is .constructed to standards that equal or
exceed those used in building the test pad, then assurance is provided that the full-
scale liner will also meet performance objectives.
4. If appropriate, a test pad provides an opportunity for the facility owner to
demonstrate that unconventional materials or construction techniques will lead to a
soil liner that meets performance objectives.
In terms of CQA, the test pad can provide an extremely powerful tool to ensure that
performance objectives are met. The authors recommend a test pad for any project in which failure
of the soil liner to meet performance objectives would have a potentially important, negative
environmental impact.
A test pad need not be constructed if results are already available for a particular soil and
construction methodology. By the same token, if the materials or methods of construction change,
an additional test pad is recommended to test the new materials or construction procedures.
Specific CQA tests and observations that are recommended for the test pad are described later in
Section 2.10.
2-2 Critical Construction Variables that Affect Soil Liners
Proper construction of compacted soil liners requires careful attention to construction
variables. In this section, basic principles are reviewed to set the stage for discussion of detailed
CQC and CQA procedures.
2.2.1 Properties of the Soil Material
The construction specifications place certain restrictions on the materials that can be used in
constructing a soil liner. Some of the restrictions are more important than others, and it is
important for CQC and CQA-personnel to understand how material properties can influence the
performance of a soil liner.
2.2.1.1 Plasticity Characteristics
The plasticity of a soil refers to the capability of a material to behave as a plastic, moldable
material. Soils are said to be either plastic or non-plastic. Soils that contain clay are usually plastic
whereas those that do not contain clay are usually non-plastic. If the soil is non-plastic, the soil is
almost always considered unsuitable.for a soil liner unless additives such as bentonite are
introduced. •
The plasticity characteristics of a soil are quantified by three parameters: liquid limit, plastic
limit, and plasticity index. These terms are defined as follows:
• Liquid Limit (LL): The water content corresponding to the arbitrary limit between the
liquid and plastic states of consistency of a soil.
• Plastic Limit (PL): The water content corresponding to the arbitrary limit between the
35
-------
plastic and solid states of consistency of a soil.
• Plasticity Index (PI): The numerical difference between liquid and plastic limits, i.e., LL
" XTJL/.
The liquid limit and plastic limit are measured using ASTM D-4318.
Experience has shown that if the soil has extremely low plasticity, the soil will possess
insufficient clay to develop low hydraulic conductivity when the soil is compacted. Also, soils that
have very low Pi's tend to grade into non-plastic soils in some locations. The question of how
low the PI can be before the soil is not sufficiently plastic is impossible to answer universally.
Daniel (1990) recommends that the soil have a PI > 10% but notes that some soils with Pi's as low
as 7% have been used successfully to build soil liners with extremely low in situ hydraulic
conductivity (Albrecht and Cartwright, 1989). Benson et al. (1992) compiled a data base from
CQA documents and related the hydraulic conductivity measured in the laboratory on small,
"undisturbed" samples of field-compacted soil to various soil characteristics. The observed
relationship between hydraulic conductivity and plasticity index is shown in Fig. 2.8. The data
base reflects a broad range of construction conditions, soil materials, and CQA procedures. It is
clear from the data base that many soils with Pi's as low as approximately 10% can be compacted
to achieve a hydraulic conductivity < 1 x 10'7 cm/s.
1.000E-6r
o
£ 1.000E-7
I
T3
O
O
O
ra
1.000E-8
1.000E-9
0 10 20 30 40 50 60 70
Plasticity Index
Figure 2.8 - Relationship between Hydraulic Conductivity and Plasticity Index (Benson et al.,
1992)
36
-------
Soils with high plasticity index (>30% to 40%) tend to form hard clods when dried and
sticky clods when wet. Highly plastic soils also tend to shrink and swell when wetted or dried.
With highly plastic soils, CQC and CQA personnel should be particularly watchful for proper
processing of clods, effective remolding of clods during compaction, and protection from
desiccation.
2.2.1.2 Percentage Fines
Some earthwork specifications place a minimum requirement on the percentage of fines in
the soil liner material. Fines are defined as the fraction of soil that passes through the openings of
the No. 200 sieve (opening size = 0.075 mm). Soils with inadequate fines typically have too little
silt- and clay-sized material to produce suitably low hydraulic conductivity. Daniel (1990)
recommends that the soil liner materials contain at least 30% fines. Data from Benson et al.
(1992), shown in Fig. 2.9, suggest that a minimum of 50% fines might be an appropriate
requirement for many soils. Field inspectors should check the soil to make sure the percentage of
fines meets or exceeds the minimum stated in the construction specifications and should be
particularly watchful for soils with less than 50% fines.
1.000E-6c
1.000E-9
40
100
Figure 2.9 - Relationship between Hydraulic Conductivity and Percent Fines (Benson et al., 1992)
37
-------
2.2.1.3 Percentage Gravel
Gravel is herein defined as particles that will not pass through the openings of a No 4
sieve (opening size = 4.76 mm). Gravel itself has a high hydraulic conductivity. However a
relatively large percentage (up to about 50%) of gravel can be uniformly mixed with a soil lin'er
material without significantly increasing the hydraulic conductivity of the material (Fig 2 10) The
hydraulic conductivity of mixtures of gravel and clayey soil is low because the clayey soil fills the
voids between the gravel particles. The critical observation for CQA inspectors to make is for
possible segregation of gravel into pockets that do not contain sufficient soil to plug the voids
between the gravel particles. The uniformity with which the gravel is mixed with the soil is more
important than the gravel content itself for soils with no more than 50% gravel by weight Gravel
also may possess the capability of puncturing geosynthetic materials - the maximum size and the
angularity of the gravel are very important for the layer of soil that will serve as a foundation layer
for a geomembrane. J
Note: Hydraulic Conductivity of
Gravel Alone = 170 cm/s
Kaolinite
Mine Spoil
40 60 80
Percent Gravel (by Weight)
100
Figure 2.10 - Relationship between Hydraulic Conductivity and Percentage Gravel Added to Two
Clayey Soils (after Shelley and Daniel, 1993).
38
-------
2.2.1.4 Maximum Particle Size
The maximum particle size is important because: (1) cobbles or large stones can interfere
with compaction, and (2) if a geomembrane is placed on top of the compacted soil liner, oversized
particles can damage the geomembrane. Construction specifications may stipulate the maximum
allowable particle size, which is usually between 25 and 50 mm (1 to 2 in.) for compaction
considerations but which may be much less for protection against puncture of an adjacent
geomembrane. If a geomembrane is to be placed on the soil liner, only the upper lift of the soil
liner is relevant in terms of protection against puncture. Construction specifications may place one
set of restrictions on all lifts of soil and place more stringent requirements on the upper lift to
protect the geomembrane from puncture. Sieve analyses on small samples will not usually lead to
detection of an occasional piece of oversized material. Observations by attentive CQC and CQA
personnel are the most effective way to ensure that oversized materials have been removed.
Oversized materials are particularly critical for the top lift of a soil liner if a geomembrane is to be
placed on the soil liner to form a composite geomembrane/soil liner.
2.2.1.5 Clay Content and Activity
The clay content of the soil may be defined in several ways but it is usually considered to
be the percentage of soil that has an equivalent particle diameter smaller than 0.005 or 0.002 mm,
with 0.002 mm being the much more common definition. The clay content is measured by
sedimentation analysis (ASTM D-422). Some construction specifications specify a minimum clay
content but many do not.
A parameter that is sometimes useful is the activity, A, of the soil, which is defined as the
plasticity index (expressed as a percentage) divided by the percentage of clay (< 0.002 mm) in the
soil. A high activity (> 1) indicates that expandable clay minerals such as montmorillonite are
present. Lambe and Whitman (1969) report that the activities of kaolinite, illite, and
montmorillonite (three common clay minerals) are 0.38,0.9, and 7.2, respectively. Activities for
naturally occurring clay liner materials, which contain a mix of minerals, is frequently in the range
of0.510% will generally contain at least 10% to 20% clay.
It is recommended that construction specification writers and regulation drafters indirectly
account for clay content by requiring the soil to have an adequate percentage of fines and a suitably
large plasticity index — by necessity the soil will have an adequate amount of clay.
2.2.1.6 Clod Size
The term clod refers to chunks of cohesive soil. The maximum size of clods may be
specified in the construction specifications. Clod size is very important for dry, hard, clay-rich
soils (Benson and Daniel, 1990). These materials generally must be broken down into small clods
in order to be properly hydrated, remolded, and compacted. Clod size is less important for wet
soils -- soft, wet clods can usually be remolded into a homogeneous, low-hydraulic-conductivity
mass with a reasonable compactive effort.
39
-------
1.000E-6
i
•^ 1.000E-7
T3
O
O
£ 1.000E-8
I
1.000E-9
10 20 30 40 50 60 70 80
Clay Content (2 micron)
Figure 2.11 - Relationship between Hydraulic Conductivity and Clay Content (Benson et al.,
No standard method is available to determine clod size. Inspectors should observe the soil
liner material and occasionally determine the dimensions of clods by direct measurement with a
ruler to verify conformance with construction specifications.
2.2.1.7 Bentonite
Bentonite may be added to clay-deficfent soils in order to fill the voids between the soil
particles with bentonite and to produce a material that, when compacted, has a very low hydraulic
conductivity. The effect of the addition of bentonite upon hydraulic conductivity is shown in Fig.
2.13 for one silty sand. For this particular soil, addition of 4% sodium bentonite was sufficient to
lower the hydraulic conductivity to less than 1 x 10"7 cm/s.
40
-------
/u
60
50
40
oT 30
20
10
n
8 .
o o
o
o
o
o o 8
o
o o° ° o °
o o . o
•O Q . •
O
0
10 20 30 40 50 60 70 80
Clay Content
Figure 2.12 - Relationship between Clay Content and Plasticity Index (Benson et al., 1992)
The critical CQC and CQA parameters are the type of bentonite, the grade of bentonite, the
grain size distribution of the processed bentonite, the amount of bentonite added to the soil, and the
uniformity of mixing of the bentonite with the soil. Two types of bentonite are the primary
commercial materials: sodium and calcium bentonite. Sodium bentonite has much greater water
absorbency and swelling potential, but calcium bentonite may be more stable when exposed to
certain chemicalsv Sodium bentonite is used more frequently than calcium bentonite as a soil
amendment for lining applications.
Any given type of bentonite may be available in several grades. The grade is a function of
impurities in the bentonite, processing procedures, or additives. Some calcium bentonites are
processed with sodium solutions to modify the bentonite to a sodium form. Some companies add
.polymers or other compounds to the bentonite to make the bentonite more absorbent of water or
more resistant to alteration by certain chemicals,
.-•-.' Another variable is the gradation of the bentonite. A facet often overlooked by CQC and
CQA inspectors is the grain size distribution of the processed bentonite. Bentonite can be ground
41
-------
to different degrees. A fine, powdered bentonite will behave differently from a coarse, granular
bentonite - if the bentonite was supposed to be finely ground but too coarse a grade was delivered,
the bentonite may be unsuitable in the mixture amounts specified. Because bentonite is available in
variable degrees of pulverization, a sieve analysis (ASTM D422) of the processed dry bentonite is
recommended to determine the grain size distribution of the material.
The most difficult parameters to control are sometimes the amount of bentonite added to the
soil and the thoroughness of mixing. Field CQC and CQA personnel should observe operational
practices carefully. v
10-5
I
t
•u
8
o
'•5
s
1
5 10 15
Percent Sodium Bentonite
20
Figure 2.13- Effect of Addition of Bentonite to Hydraulic Conductivity of Compacted Silty Sand
2.2.2 Molding Water Content
For natural soils, the degree of saturation of the soil liner material at the time of compaction
is perhaps the single most important variable that controls the engineering properties of the
compacted material. The typical relationship between hydraulic conductivity and molding water
content is shown in Fig. 2.14. Soils compacted at water contents less than optimum (dry of
optimum) tend to have a relatively high hydraulic conductivity; soils compacted at water contents
greater than optimum (wet of optimum) tend to have a low hydraulic conductivity and low
strength. For some soils, the water content relative to the plastic limit (which is the water content
of the soil when the soil is at the boundary between being a solid and plastic material) may indicate
the degree to which the soil can be compacted to yield low hydraulic conductivity. In general if
the water content is greater than the plastic limit, the soil is in a plastic state and should be capable
ol being remolded into a low-hydraulic-conductivity material. Soils with water contents dry of the
plastic limit will exhibit very little "plasticity" and may be difficult to compact into a low-hydraulic-
conducbvity mass without delivering enormous compactive energy to the soil. With soil-bentonite
mixes, molding water content is usually not as critical as it is for natural soils. "
42
-------
£
g>
'
Molding
O
O
O
Water Content
Molding Water Content
Figure 2.14 - Effect of Molding Water Content on Hydraulic Conductivity
The water content of highly plastic soils is particularly critical. A photograph of a highly
plastic soil (PI = 41%) compacted 1% dry of the optimum water content of 17% is shown in Fig.
2.15. Large inter-clod voids are visible; the clods of clay were too dry and hard to be effectively
remolded with the compactive effort used. A photograph of a compacted specimen of the same soil
moistened to 3% wet of optimum and then compacted is shown in Fig. 2.16. At this water
content, the soft soil could be remolded into a homogenous, low-hydraulic-conductivity mass.
43
-------
16
STANDARD
PROCTO
Figure 2.15 - Photograph of Highly Plastic Clay Compacted with Standard Proctor Effort at
Water Content of 16% (1% Dry of Optimum).
a
44
-------
2O %,
STANDARD
PROCTOR
Figure 2.16 - Photograph of Highly Plastic Clay Compacted with Standard Proctor Effort at a
Water Content of 20% (3% Wet of Optimum).
It is usually preferable to compact the soil wet of optimum to minimize hydraulic
conductivity. However, the soil must not be placed at too high a water content. Otherwise, the
shear strength may be too low, there may be great risk of desiccation cracks forming if the soil
dries, and ruts may form when construction vehicles pass over the liner. It is critically important
that CQC and CQA inspectors verify that the water content of the soil is within the range specified
in the construction documents.
45
-------
2.2.3 Type of Compaction
In the laboratory, soil can be compacted in four ways:
1 • Impact Compaction: A ram is repeatedly raised and dropped to compact a lift soil
into a mold (Fig. 2.17a), e.g., standard and modified Proctor.
2- Static Compaction: A piston compacts a lift of soil with a constant stress (Fig.
2.17b).
3 • Kneading Compaction: A "foot" kneads the soil (Fig. 2.17c).
4- Vibratory Compaction: The soil is vibrated to densify the material (Fig. 2.17d).
A. Impact Compaction
Drop
Weight
B. Static Compaction
Controlled Force
C. Kneading Compaction
Controlled Force
- ,.
D. Vibratory Compaction
Figure 2.17 - Four Types of Laboratory Compaction Tests
46
-------
Experience from the laboratory has shown that the type of compaction can affect hydraulic
conductivity, e.g., as shown in Fig. 2.18. Kneading the soil helps to break down clods and
remold the soil into a homogenous mass that is free of voids or large pores. Kneading of the soil
is particularly beneficial for highly plastic soils. For certain bentonite-soil blends that do not form
clods, kneading is not necessary. Most soil liners are constructed with "footed" rollers. The "feet"
on the roller penetrate into a loose lift of soil and knead the soil with repeated passages of the
roller. The dimensions of the feet on rollers vary considerably. Footed rollers with short feet (=
75 mm or 3 in.) are called "pad foot" rollers; the feet are said to be "partly penetrating" because the
foot is too short to penetrate fully a typical loose lift of soil. Footed rollers with long feet (~ 200
mm or 8 in.) are often called "sheepsfoot" rollers; the feet fully penetrate a typical loose lift. Figure
2.19 contrasts rollers with partly and fully penetrating feet.
10 -6
10 -7
o
O
10 -8
1
1
E
=1
B.
O
A Static Compaction
• Kneading Compaction
16
18
20
22
24
26
28
Molding Water Content (%)
Figure 2.18 - Effect of Type of Compaction on Hydraulic Conductivity (from Mitchell et al., 1965)
47
-------
Roller with
Fully Penetrating
Feet
Loose Lift of Soil
Compacted Lift of Soil
Fully Penetrating Feet on Roller
Compact Base of New, Loose of Soil
Into Surface of Old, Previously
Compacted Lift
Roller with
Partly
Penetrating
Feet
Partly Penetrating Feet on Roller Do
Not Extend to Base of New, Loose
Lift of Soil and Do Not Compact New
Lift into Surface of Old Lift
Figure 2.19 - Footed Rollers with Partly and Fully Penetrating Feet
Some construction specifications place limitations on the type of roller that can be used to
compact a soil liner. Personnel performing CQC and CQA should be watchful of the type of roller
to make sure it conforms to construction specifications. It is particularly important to use a roller
with fully penetrating feet if such a roller is required; use of a non-footed roller or pad foot roller
would result in less kneading of the soil.
2.2.4 Energy of Compaction
TU A ^ enerSy used to compact soil can have an important influence on hydraulic conductivity
Ihe data shown in Fig. 2.20 show that increasing the compactive effort produces soil that has a
greater dry unit weight and lower hydraulic conductivity. It is important that the soil be compacted
with adequate energy if low hydraulic conductivity is to be achieved.
In the field, compactive energy is controlled by:
The weight of the roller and the way the weight is distributed (greater weight
produces more compactive energy).
The thickness of a loose lift (thicker lifts produce less compactive energy per unit
volume of soil).
1.
2.
3.
The number of passes of the compactor (more passes produces more compactive
energy). r F
48
-------
C-5
g>
I
"c
(a
£
I
o
O
CO
Low Compactive Effort
10'6
10-7
15 20
Molding Water Content (%)
10
15 20
Molding Water Content (%)
Figure 2.20 - Effect of Compactive Energy on Hydraulic Conductivity (after Mitchell et al., 1965)
Many engineers and technicians assume that percent compaction is a good measure of
compactive energy. Indeed, for soils near optimum water content or dry of optimum, percent
compaction is a good indicator of compactive energy: if the percent compaction is low, then the
compactive energy was almost certainly low. However, for soil compacted wet of optimum,
49
-------
percent compaction is not a particularly good indicator of compactive energy. This is illustrated by
the curves in Fig. 2.21. The same soil is compacted with Compactive Energy A and Energy B
(Energy B > Energy A) to develop the compaction curves shown in Fig. 2.21 Next two
specimens are compacted to the same water content (wA = WB). The dry unit weights are
practically identical (yd>A ~ y^) despite the fact that the energies of compaction were different.
Further, the hydraulic conductivity (k) of the specimen compacted with the larger energy (Energy
B) has a lower hydraulic conductivity than the specimen compacted with Energy A despite the fact
tnat yd,A » Yd3. The percent compaction for the two compacted specimens is computed as follows-
.
V=
o
1
8
.a
I
1
_Compactive
"Energy A
_Compactive
"Energy B
Molding Water Content
I
a
d.A = d,B
Compactive,
Energy
Compactive
Energy A
Molding Water Content
Figure 2.21 - lUustration of Why Dry Unit Weight Is a Poor Indicator of Hydraulic Conductivity
for Soil Compacted Wet of Optimum
50
-------
PA = Yd,A/[Yd,max]A x 100%
PB=Yd3/tYd,max]BxlOO%
Since Yd,A = Yd,B but [Yd,max]B > [Yd,max]A, then PA > PB- Thus, based on percent compaction,
since PA > PB, one might assume Soil A was compacted with greater compactive energy than Soil
B. In fact, just the opposite is true. CQC and CQA personnel are strongly encouraged to monitor
equipment weight, lift thickness, and number of passes (in addition to dry unit weight) to ensure
that appropriate compactive energy is delivered to the soil. Some CQC and CQA inspectors have
failed to realize that footed rollers towed by a dozer must be filled with liquid to have the intended
large weight.
Experience has shown that effective CQC and CQA for soil liners can be accomplished
using the line of optimums as a reference. The "line of optimums" is the locus of (wopt, Yd,max)
points for compaction curves developed on the same soil with different compactive energies (Fig.
2.22). The greater the percentage of actual (w,Yd) points that lie above the line of optimums the
better the overall quality of construction (Benson and Boutwell, 1992). Inspectors are encouraged
to monitor the percentage of field-measured (w,Yd) points that lie on or above the line of optimums.
If the percentage is less than 80% to 90%, inspectors should carefully consider whether adequate
compactive energy is being delivered to the soil (Benson and Boutwell, 1992).
g>
.t=!
1
(I
d.max '
Line of Optimums
w
opt
Molding Water Content (w)
Figure 2.22 - Line of Optimums
51
-------
2.2.5 Bonding of Lifts
• _r u are P°orly bonded, a zone of high hydraulic conductivity will develop at
interfaces between lifts. Poorly bonded lift interfaces provide hydraulic connection between more
permeable zones in adjacent lifts (Fig. 2.23). It is important to bond lifts together to the greatest
extent possible, and to maximize hydraulic tortuosity along lift interfaces, in order to minimize the
overall hydraulic conductivity.
Bonding of lifts is enhanced by:
Making sure the surface of a previously-compacted lift is rough before placing the
new lift of soil (the previously-compacted lift is often scarified with a disc prior to
placement of a new lift), which promotes bonding and increased hydraulic
tortuosity along the lift interface..
2. Using a fully-penetrating footed roller (the feet pack the base of the new lift into the
surface of the previously-compacted lift).
Inspectors should pay particular attention to requirements for scarification and the length of feet on
rollers* , • ,
i.
Good Bonding of Lifts
Poor Bonding of Lifts
Good Bonding of Lifts Causes
Hydraulic Defects in Adjacent
Lifts To Be Hydraulically
Unconnected
Poor Bonding of Lifts Causes
Hydraulic Defects in Adjacent
Lifts To Be Hydraulically
Connected To Each Other
Figure 2.23 - Flow Pathways Created by Poorly Bonded Lifts
52
-------
2.2.6 Protection Against Desiccation and Freezing
Clay soils shrink when they are dried and, depending on the amount of shrinkage, may
crack. Cracks that extend deeper than one lift can be disastrous. Inspectors must be very careful
to make sure that no significant desiccation occurs during or after construction. Water content
should be measured if there are doubts.
Freezing of a soil liner will cause the hydraulic conductivity to increase. Damage caused by
superficial freezing to a shallow depth is easily repaired by rerolling the surface. Deeper freezing is
not so easily repaired and requires detailed investigation discussed in Section 2.9.2.3. CQC &
CQA personnel should be watchful during periods when freezing temperatures are possible.
2.3 Field Measurement of Water Content and Dry Unit Weight
2.3.1 Water Content Measurement
2.3.1.1 Overnight Oven Drying (ASTM 0-2216)
The standard method for determining the water content of a soil is to oven dry the soil
overnight in a forced-convention oven at 110°C. This is the most fundemental and most accurate
method for determining the water content of a soil. All other methods of measurement are
referenced to the value of water content determined with this method.
Were it not for the fact that one has to wait overnight to determine water content with this
method, undoubtedly ASTM D-2216 would be the only method of water content measurement
used in the CQC and CQA processes for soil liners. However, field personnel cannot wait
overnight to make decisions about continuation with the construction process.
2.3.1.2 Microwave Oven Drying (ASTM D-4643)
Soil samples can be dried in a microwave oven to obtain water contents much more quickly
than can be obtained with conventional overnight oven drying. The main problem with microwave
oven drying is that if the soil dries for too long in the microwave oven, the temperature of the soil
will rise significantly above 110°C. If the soil is heated to a temperature greater than 11Q°C, one
will measure a water content that is greater than the water content of the soil determined by drying
at 110°C. Overheating the soil drives water out of the crystal structure of some minerals and
thereby leads to too much loss of water upon oven drying.
To guard against overdrying the soil, ASTM method D-4643 requires that the soil be dried
for three minutes and then weighed. The soil is then dried for an additional minute and
reweighed. The process of drying for one minute and weighing the soil prevents overheating of
the soil and forces the operator to cease the drying process once the weight of the soil has
stabilized.
Under ideal conditions, microwave oven drying can yield water contents that are almost
indistinguishable from values measured with conventional overnight oven drying. Problems that
are sometimes encountered with microwave oven drying include problems in operating the oven if
the soil contains significant metal and occasional problems with samples exploding from expansion
of gas in the interior of the sample during microwave oven drying. Because errors can
occasionally arise with microwave oven drying, the water content determined with microwave
oven drying should be periodically checked with the value determined by conventional over-night
oven drying (ASTM D-2216).
53
-------
2.3.1.3 Direct Hearing fASTM D-495
Direct heating of the soil was common practice up until about two decades ago. To dry a
soil with direct heating, one typically places a mass of soil into a metallic container (such as a
cooking utensil) and then heats the soil over a flame, e.g., a portable cooking stove, until the soil
first appears dry. The mass of the soil plus container is then measured. Next, the soil is heated
some more and then re-weighed. This process is repeated until the mass ceases to decrease
significantly (i.e., to change by < 0.1% or less).
The main problem with direct heating is that if the soil is overheated during drying, the
water content that is measured will be too large. Although ASTM D-4959 does not eliminate this
problem, the ASTM method does warn the user not to overheat the soil. Because errors can do
arise with direct heating, the water content determined with direct heating should be regularly
checked with the value determined by conventional over-night oven drying (ASTM D-2216).
2.3.1.4 Calcium Carbide Gas Pressure Tester fASTM 0-49441
A known mass of moist soil is placed in a testing device and calcium carbide is introduced.
Mixing is accomplished by shaking and agitating the soil with the aid of steel balls and a shaking
apparatus. A measurement is made of the gas pressure produced. Water content is determined
from a calibration curve. Because errors can occasionally arise with gas pressure testing, the water
content determined with gas pressure testing should be periodically checked with the value
determined by conventional over-night oven drying (ASTM D-2216).
2.3.1.5 Nuclear Method fASTM D-30171
The most widely used method of measuring the water content of compacted soil is the
nuclear method. Measurement of water content with a nuclear device involves the moderation or
thermalization of neutrons provided by a source of fast neutrons. Fast neutrons are neutrons with
an energy of approximately 5 MeV. The radioactive source of fast neutrons is embedded in the
interior part of a nuclear water content/density device (Fig. 2.24). As the fast neutrons move into
the soil, they undergo a reduction in energy every time a hydrogen atom is encountered. A series
of energy reductions takes place when a neutron sequentially encounters hydrogen atoms. Finally,
after an average of nineteen collisions with hydrogen atoms, a neutron ceases to lose further energy
and is said to be a "thermal" neutron with an energy of approximately 0.025 MeV. A detector in
the nuclear device senses the number of thermal neutrons that are encountered. The number of
thermal neutrons that are encountered over a given period of time is a function of the number of
fast neutrons that are emitted from the source and the density of hydrogen atoms in the soil located
immediately below the nuclear device. Through appropriate calibration, and with the assumption
that the only source of hydrogen in the soil is water, the nuclear device provides a measure of the
water content of the soil over an average depth of about 200 mm (8 in.).
There are a number of potential sources of error with the nuclear water content measuring
device. The most important potential source of error is extraneous hydrogen atoms not associated
with water. Possible sources of hydrogen other than water include hydrocarbons, methane gas,
hydrous minerals (e.g., gypsum), hydrogen-bearing minerals (e.g., kaolinite, illite, and
montmorillpnite), and organic matter in the soil. Under extremely unfavorable conditions the
nuclear device can yield water content measurements that are as much as ten percentage points in
error (almost always on the high side). Under favorable conditions, measurement error is less than
one percent. The nuclear device should be calibrated for site specific soils and changing conditions
within a given site.
54
-------
Handle
L
jRod ^^
na
source r
37) .
X
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X i
xxxxx
1 '"^
., Guide Rod
Fast Neutron Source
(Am 241 + Be)
/-
Neutron
Detector,,
/ rso™
/ y^ ^^Dete
xxxxx
xxxxx
xxxxx
xxxxx
X X X X
'Vx'x'V
xxxxx
xN,V,V
A/VW
X X X X
xxxxx
^VxVx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
X X X X
xxxxx
V\-Vx\-
xxxxxxxxx
Vx'Vx'Vx'Vx'V
xxxxxxxxxx
xxxxxxxxx
xxxxxxxxxx
XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXX
xxxxxxxxxxxxxxxxx
xxxxx xxxxxxxxxx
xxxxxxxxxxxxxxxxx
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
X X
«
X X
X X
N/v
X X
X X
V,
V ' sVvVVVx'VVV's
XXX XXXXXXXXXX
X XXXXXXXXXXX
XXX XXXXXXXXXX
X XXXXXXXXXXX
XXX XXXXXXXXXX
X XXXXXXXXXXX
XXX XXXXXXXXXX
X XXXXXXXXXXX
XXX XXXXXXXXXX
X XXXXXXXXXXX
XXX XXXXXXXXXX
X XXXXXXXXXXX
XXX XXXXXXXXXX
X XXXXXXXXXXX
xxxxxxxxxxxxxx
X XXXXXXXXXXX
XXXXXXXXX XX XXX
X XXXXXXXXXXX
xxxxxxxxxxxxxx
X XXXXXXXXXXX
xxxxxxxxxxxxxx
X XXXXXXXXXXX
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx-
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
XXXXXXXX XX X X X X
xxxxxxxxxxxxxx
Vxxx
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
X X
XXX
X X
XXX
X X
XX X
XX
XXX
XX
XX X
X X
XXX
X X
*: :
XXX
XXX
VxV
XXX
XXX
VxV
Figure 2.24 - Schematic Diagram of Nuclear Water Content - Density Device
Another potential source of error is the presence of individuals, equipment, or trenches
located within one meter of the device (all of which can cause an error). The device must be
warmed up for an adequate period of time or the readings may be incorrect. If the surface of the
soil is improperly prepared and the device is not sealed properly against a smooth surface,
erroneous measurements can result. If the standard count, which is a measure of the intensity of
radiation from the source, has not been taken recently an erroneous reading may result. Finally,
many nuclear devices allow the user to input a moisture adjustment factor to correct the water
content reading by a fixed amount. If the wrong moisture adjustment factor is stored in the
device's computer, the reported water content will be in error.
,,, It is very important that the CQC and GQA personnel be well versed in the proper use of
nuclear water content measurement devices. There are many opportunities for error if personnel
are not properly trained or do not correctly use the equipment. As indicated later, the nuclear
device should be checked with other types of equipment to ensure that site-specific variables are
not influencing test results. Nuclear equipment may be checked against other nuclear devices
(particularly new devices or recently calibrated devices) to minimize potential for errors.
55
-------
2.3.2 Unit Weight
2.3.2.1 Sand Cone fASTM D-15561
The sand cone is a device for determining the volume of a hole that has been excavated into
soil. The idea is to determine the weight of sand required to fill a hole of unknown volume.
Through calibration, the volume of sand that fills the hole can be determined from the weight of
sand needed to fill the hole. A schematic diagram of the sand cone is shown in Fig. 2.25.
\Sahd ",
Plastic or
Glass Jar
Mv/
X11
/ v^
/ \
Figure 2.25 - Sand Cone Device
The sand cone is used as follows. First, a template is placed on the ground surface. A
circle is scribed along the inside of the hole in the template. The template is removed and soil is
excavated from within the area marked by the scribed circle. The soil that is excavated is weighed
to determine the total weight (W) of the soil excavated. The excavated soil is oven dried (e.g.,
with a microwave oven) to determine the water content of the soil. The bottle in a sand cone device
is filled with sand and the full bottle is weighed. The template is placed over the hole and the sand
cone device is placed on top of the template. A valve on the sand cone device is opened, which
allows sand to rain down through the inverted funnel of the device and inside the excavated hole.
56
-------
When the hole and funnel are filled with sand, the valve is closed and the bottle containing sand is
weighed. The difference in weight before and after the hole is dug is calculated. Through
calibration, the weight of sand needed to fill the funnel is subtracted, and the volume of the hole is
computed from the weight of sand that filled the hole. The total unit weight is calculated by
dividing the weight of soil excavated by the computed volume of the excavated hole. The dry unit
weight is then calculated from Eq. 2.1.
The sand cone device provides a reliable technique for determining the dry unit weight of
the soil. The primary sources of error are improper calibration of the device, excavation of an
uneven hole that has sharp edges or overhangs that can produce voids in the sand-filled hole,
variations in the sand, excessively infrequent calibrations, contamination of the sand by soil
particles if the sand is reused, and vibration as from equipment operating close to the sand cone.
2.3.2.2 Rubber Balloon (ASTM D-2167^
The rubber balloon is similar to the sand cone except that water is used to fill the excavated
hole rather than sand. A rubber balloon device is sketched in Fig. 2.26. As with the sand cone
test, the test is performed with the device located on the template over the leveled soil. Then a hole
is excavated into the soil and the density measuring device is again placed on top of a template at
the ground surface. Water inside the rubber balloon device is pressurized with air to force the
water into the excavated hole. A thin membrane (balloon) prevents the water from entering the
soil. The pressure in the water forces the balloon to conform to the shape of the excavated hole. A
graduated scale on the rubber balloon device enables one to determine the volume of water required
to fill the hole. The total unit weight is calculated by dividing the known weight of soil excavated
from the hole by the volume of water required to fill the hole with the rubber balloon device. The
dry unit weight is computed from Eq. 2.1.
The primary sources of error with the rubber balloon device are improper excavation of the
hole (leaving small zones that cannot be filled by the pressurized balloon), excessive pressure that
causes local deformation of the adjacent soil, rupture of the balloon, and carelessness in operating
the device (e.g., not applying enough pressure to force the balloon to fill the hole completely).
2.3.2.3 Drive Cylinder (ASTM D-29371
A drive cylinder is sketched in Fig. 2.27. A drop weight is used to drive a thin-walled tube
sampler into the soil. The sampler is removed from the soil and the soil sample is trimmed flush to
the bottom and top of the sampling tube. The soil-filled tube is weighed and the known weight of
the sampling tube itself is subtracted to determine the gross weight of the soil sample. The
dimensions of the sample are measured to enable calculation of volume. The unit weight is
calculated by dividing the known weight by the known volume of the sample. The sample is oven
dried (e.g., in a microwave oven) to determine water content. The dry unit weight is computed
from Eq. 2.1.
The primary problems with the drive cylinder are sampling disturbance caused by rocks or
stones in the soil, densification of the soil caused by compression resulting from driving of the
tube into the soil, and nonuniform driving of the tube into the soil. The drive cylinder method is
not recommended for stony or gravely soils. The drive cylinder method works best for relatively
soft, wet clays that do not tend to densify significantly when the tube is driven into the soil and for
soils that are free of gravel or stones. However, even under favorable circumstances, densification
of the soil caused by driving the ring into the soil can cause an increase in total unit weight of 2 to 5
pcf (0.3 to 0.8 kN/m3).
57
-------
Air Pressure
Fitting
Rubber Balloon
Figure 2.26 - Schematic Diagram of Rubber Balloon Device
2.3.2.4 Nuclear Method (ASTM D-292T)
Unit weight can be measured with a nuclear device operated in two ways as shown in Fig.
2.28. The most common usage is called direct transmission in which a source of gamma radiation
is lowered down a hole made into the soil to be tested (Fig. 2.28a). Detectors located in the
nuclear density device sense the intensity of gamma radiation at the ground surface. The intensity
of gamma radiation detected at the surface is a function of the intensity of gamma radiation at the
source and the total unit weight of the soil material. The second mode of operation of the nuclear
density device is called backscattering. With this technique the source of gamma radiation is
located at the ground surface (Fig. 2.28b). The intensity of gamma radiation detected at the surface
is a function of the density of the soil as well as the radioactivity of the source. With the
backscattering technique, the measurement is heavily dependent upon the density of the soil within
the upper 25 to 50 mm of soil. The direct transmission method is the recommended technique for
soil liners because direct transmission provides a measurement averaged over a greater depth than
backscattering.
58
-------
Guide Rod
Drop Hammer
Drive Head
Sampling Tube
Figure 2.27 - Schematic Diagram of Drive Ring
The operation of a nuclear density device in the direct transmission mode is as follows.
First, the area to be tested is smoothed, and a hole is made into the soil liner material by driving a
rod (called the drive rod) into the soil. The diameter of the hole is approximately 25 mm (1 in.)
and the depth of the hole is typically 50 mm (2 in.) greater than the depth to which the gamma
radiation source will be lowered below the surface. The nuclear device is then positioned with the
source rod directly over the hole in the soil liner material. The source rod is then lowered to a
depth of approximately 50 mm (2 in.) above the base of the hole. The source is then pressed
against the surface of the hole closest to the detector by pulling on the nuclear device and forcing
the source to bear against the side of the hole closest to the detector. The intent is to have good
contact between the source and soil along a direct line from source to detector. The intensity of
radiation at the detector is measured for a fixed period of time, e.g., 30 or 60 s. The operator can
select the period of counting. The longer the counting period, the more accurate the measurement.
However, the counting period cannot be extended too much because productivity will suffer.
59
-------
(A) Direct Transmission
(B) Backscattering
Figure 2.28 - Measurement of Density with Nuclear Device by (a) Direct Transmission and (B)
Backscattering
After total unit weight has been determined, the measured water content is used to compute
dry unit weight (Eq. 2.1). The potential sources of error with the nuclear device are fewer and less
significant in the density-measuring mode compared to the water content measuring mode. The
most serious potential source of error is improper use of the nuclear density device by the operator.
One gross error that is sometimes made is to drive the source rod into the soil rather than inserting
the source rod into a hole that had been made earlier with the drive rod. Improper separation of
the source from the base of the hole, an inadequate period of counting, inadequate warm-up,
spurious sources of gamma radiation, and inadequate calibration are other potential sources of
error.
60
-------
2.4 Inspection of Borrow Sources Prior to Excavation
2.4.1 Sampling for Material Tests
In order to determine the properties of the borrow soil, samples are often obtained from the
potential borrow area for laboratory analysis prior to actual excavation but as part of the
construction contract. Samples may be obtained in several ways. One method of sampling is to
drill soil borings and recover samples of soil from the borings. This procedure can be very
effective in identifying major strata and substrata within the borrow area. Small samples obtained
from the borings are excellent for index property testing but often do not provide a very good
indication of subtle stratigraphic changes in the borrow area. Test pits excavated into the borrow
soil with a backhoe, frontend loader, or other excavation equipment can expose a large cross-
section of the borrow soil. One can obtain a much better idea of the variability of soil in the
potential borrow area by examining exposed cuts rather than viewing small soil samples obtained
from borings.
Large bulk samples of soil are required for compaction testing in the laboratory. Small
samples of soil taken with soil sampling devices do not provide a sufficient volume of soil for
laboratory compaction testing. Some engineers combine samples of soil taken at different depths
or from different borings to produce a composite sample of adequate volume. This technique is
not recommended because a degree of mixing takes place in forming the composite laboratory test
sample that would not take place in the field. Other engineers prefer to collect material from auger
borings for use in performing laboratory compaction tests. This technique is likewise not
recommended without careful borrow pit control because vertical mixing of material takes place
during auguring in a way that would not be expected to occur in the field unless controlled vertical
cuts are made. The best method for obtaining large bulk samples of material for laboratory
compaction testing is to take a large sample of material from one location in the borrow source. A
large, bulk sample can be taken from the wall or floor of a test pit that has been excavated into the
borrow area. Alternatively, a large piece of drilling equipment such as a bucket auger can be used
to obtain a large volume of soil from a discreet point in the ground.
2.4.2. Material Tests
Samples of soil must be taken for laboratory testing to ensure conformance with
specifications for parameters such as percentage fines and plasticity index. The samples are
sometimes taken in the borrow pit, are sometimes taken from the loose lift just prior to compaction,
and are sometimes taken from both. If samples are taken from the borrow area, CQA inspectors
track the approximate volumes of soil excavated and sample at the frequency prescribed in the CQA
plan. Sometimes borrow-source testing is performed prior to issuing of a contract to purchase the
borrow material. A CQA program cannot be implemented for work already completed. The CQA
personnel will have ample opportunity to check the properties of soil materials later during
excavation and placement of the soils. If the CQA personnel for a project did not observe borrow
soil testing, the CQA personnel should review the results of borrow soil testing to ensure that the
required tests have been performed. Additional testing of the borrow material may be required
during excavation of the material.
The material tests that are normally performed on borrow soil are water content, Atterberg
limits, particle size distribution, compaction curve, and hydraulic conductivity (Table 2.2). Each
of these tests is discussed below.
61
-------
Table 2.2 - Materials Tests
Parameter
ASTM Test
Method
Title of ASTM Test
Water Content
Liquid Limit,
Plastic Limit, &
Plasticity Index
Particle Size
Distribution
Compaction
Curve
Hydraulic
Conductivity
D-2216
D-4643
D-4944
D4959
D4318
D-422
D-698
D-1557
D-5084
Laboratory Determination of Water (Moisture)
Content of Soil and Rock
Determination of Water (Moisture) Content of Soil
by the Microwave Oven Method
Field determination of Water (Moisture) Content of
Soil by the Calcium Carbide Gas Pressure Tester
Method
Determination of Water (Moisture) Content by Direct
Heating Method
Liquid Limit, Plastic Limit, and Plasticity Index of
Soils
Particle Size Analysis of Soil
Moisture-Density Relations for Soils and Soil-
Aggregate Mixtures Using 5.5-lb. (2.48-kg)
Rammer and 12-in. (305-mm) Drop
Moisture-Density Relations for Soils and Soil-
Aggregate Mixtures Using 10-lb. (4.54-kg)
Rammer and 18-in. (457-mm) Drop
Measurement of Hydraulic Conductivity of
Saturated Porous Materials Using A Flexible Wall
Permeameter
2.4.2.1 Water Content
It is important to know the water content of the borrow soils so that the need for wetting or
drying the soil prior to compaction can be identified. The water content of the borrow soil is
normally measured following the procedures outlined in ASTM D-2216 if one can wait overnight
for results. If not, other test methods described in Section 2.3.1 and listed in Table 2.2 can be
used to produce results faster.
62
-------
2.4.2.2 Atterberg Limits
Construction specifications for compacted soil liners often require a minimum value for the
liquid limit and/or plasticity index of the soil. These parameters are measured in the laboratory
with the procedures outlined in ASTM D-4318.
2.4.2.3 Particle Size Distribution
Construction specifications for soil liners often place limits on the minimum percentage of
fines, the maximum percentage of gravel, and in some cases the minimum percentage of clay.
Particle size analysis is performed following the procedures in ASTM D-422. Normally the
requirements for the soil material are explicitly stated in the construction specifications. An
experienced inspector can often judge the percentage of fine material and the percentage of sand or
gravel in the soil. However, compliance with specifications is best documented by laboratory
testing. ,
2.4.2.4 Compaction Curve
Compaction curves are developed utilizing the method of laboratory compaction testing
required in the construction specifications. Standard compaction (ASTM D-698) and modified
compaction (ASTM D-1557) are two common methods of laboratory compaction specified for soil
liners. However, other compaction methods (particularly those unique to state highway or
transportation departments) are sometimes specified.
Great care should be taken to follow the procedures for soil preparation outlined in the
relevant test method. In particular, the drying of a cohesive material can change the Atterberg
limits as well as the compaction characteristics of the soil. If the test procedure recommends that
the soil not be dried, the soil should not be dried. Also, care must be taken when sieving the soil
not to remove clods of cohesive material. Rather, clods of soil retained on a sieve should be
broken apart by hand if necessary to cause them to pass through the openings of the sieve. Sieves
should only be used to remove stones or other large pieces of material following ASTM
procedures.
2.4.2.5 Hydraulic Conductivity
The hydraulic conductivity of compacted samples of borrow material may be measured
periodically to verify that the soil liner material can be compacted to achieve the required low
hydraulic conductivity. Several methods of laboratory permeation are available, and others are
under development. ASTM D-5084 is the only ASTM procedure currently available. Care should
be taken not to apply excessive effective confining stress to test specimens. If no value is specified
in the CQA plan, a maximum effective stress of 35 kPa (5 psi) is recommended for both liner and
cover systems.
Care should be taken to prepare specimens for hydraulic conductivity testing properly. In
addition to water content and dry unit weight, the method of compaction and the compactive energy
can have a significant influence on the hydraulic conductivity of laboratory-compacted soils. It is
particularly important not to deliver too much compactive energy to attain a desired dry unit weight.
The purpose of the hydraulic conductivity test is to verify that borrow soils can be compacted to the
desired hydraulic conductivity using a reasonable compactive energy.
No ASTM compaction method exists for preparation of hydraulic conductivity test
specimens. The following procedure is recommended:
63
-------
1.
2.
3.
5.
Obtain a large, bulk sample of representative material with a mass of approximately
20 kg.
Develop a laboratory compaction curve using the procedure specified in the
construction specifications for compaction control, e.g., ASTM D-698 or D-1557.
Determine the target water content (wtarget) and dry unit weight (Yd,target) for the
hydraulic conductivity test specimen. The value of wtarget is normally the lowest
acceptable water content and Yd,target is normally the minimum acceptable dry unit
weight (Fig. 2.29).
Enough soil to make several test specimens is mixed to wtarget. The compaction
procedure used in Step 2 is used to prepare a compacted specimen, except that the
energy of compaction is reduced, e.g., by reducing the number of drops of the ram
per lift. The dry unit weight (yd) is determined. If Yd « Yd, target, the compacted
specimen may be used for hydraulic conductivity testing. If Yd * Yd.target. then
another test specimen is prepared with a larger or smaller (as appropriate)
compactive energy. Trial and error preparation of test specimens is repeated until Yd
* Yd, target- The procedure is illustrated in Fig. 2.29. The actual compactive effort
should be documented along with hydraulic conductivity.
Atterberg limits and percentage fines should be determined for each bulk sample.
Water content and dry density should be reported for each compacted specimen.
I
"c
d.target
Laboratory
Compaction
Curve
Second Trial
i second r
K \
i First TriaN
(i
wtarget
Water Content
Figure 2.29 - Recommended Procedure for Preparation of a Test Specimen Using Variable (But
Documented) Compactive Energy for Each Trial
64
-------
2.4.2.6 Testing Frequency
The CQA plan should stipulate the frequency of testing. Recommended minimum values
are shown in Table 2.3. The tests listed in Table 2.3 are normally performed prior to construction
as part of the characterization of the borrow source. However, if time or circumstances do not
permit characterization of the borrow source prior to construction, the samples for testing are
obtained during excavation or delivery of the soil materials.
Table 2.3 - Recommended Minimum Testing Frequencies for Investigation of Borrow Source
Parameter Frequency
Water Content 1 Test per 2000 m3 or Each Change in Material Type
Atterberg Limits 1 Test per 5000 m3 or Each Change in Material Type
Percentage Fines 1 Test per 5000 m3 or Each Change in Material Type
Percent Gravel 1 Test per 5000 m3 or Each Change in Material Type
Compaction Curve 1 Test per 5000 m3 or Each Change in Material Type
Hydraulic Conductivity 1 Test per 10,000 m3 or Each Change in Material Type
Note: 1 yd3 = 0.76m3
2.5 Inspection during Excavation of Borrow Soil
It is strongly recommended that a qualified inspector who reports directly to the CQA
engineer observe all excavation of borrow soil in the borrow pit. Often the best way to determine
whether deleterious material is present in the borrow soil is to observe the excavation of the soil
directly.
A key factor for inspectors to observe is the plasticity of the soil. Experienced technicians
can often determine whether or not a soil has adequate plasticity by carefully examining the soil in
the field. A useful practice for field identification of soils is ASTM D-2488, "Description and
Identification of Soils (Visual-Manual Procedure)." The following procedure is used for
identifying clayey soils.
65
-------
Dry strength: The technician selects enough soil to mold into a ball about 25 mm (1 in.)
in diameter. Water is added if necessary to form three balls that each have a diameter of
about 12 mm (1/2 in.). The balls are allowed to dry in the sun. The strength of the dry
balls is evaluated by crushing them between the fingers. The dry strength is described
with the criteria shown in Table 2.4. If the dry strength is none or low, inspectors
should be alerted to the possibility that the soil lacks adequate plasticity.
Plasticity: The soil is moistened or dried so that a test specimen can be shaped into an
elongated pat and rolled by hand on a smooth surface or between the palms into a thread
about 3 mm (1/8 in.) in diameter. If the sample is too wet to roll easily it should be
spread into a thin layer and allowed to lose some water by evaporation. The sample
threads are re-rolled repeatedly until the thread crumbles at a diameter of about 3 mm (1/8
in.). The thread will crumble at a diameter of 3 mm when the soil is near the plastic limit.
The plasticity is described from the criteria shown in Table 2.5, based upon observations
made during the toughness test. Non-plastic soils are usually unsuitable for use as soil
liner materials without use of amendments such as bentonite.
Table 2.4 - Criteria for Describing Dry Strength (ASTM D-2488)
Description Criteria
The dry specimen crumbles into powder with mere
pressure of handling
The dry specimen crumbles into powder with some
finger pressure
Medium The dry specimen breaks into pieces or crumbles
with considerable finger pressure
**'Sh The dry specimen cannot be broken with finger
pressure. Specimen will break into pieces between
thumb and a hard surface
Very High The dry specimen cannot be broken between the
thumb and a hard surface
66
-------
Table 2.5 - Criteria for Describing Plasticity (ASTM D-2488)
Description Criteria
Nonplastic A 3 mm (1/8-in.) thread cannot be rolled at any
water content
Low The thread can barely be rolled and the lump cannot
be formed when drier than the plastic limit
Medium A thread is easy to roll and not much time is
required to reach the plastic limit The thread
cannot be rerolled after reaching the plastic limit.
The lump crumbles when drier than the plastic limit
High It takes considerable time rolling and kneading to
reach the plastic limit. The thread can be rerolled
several times after reaching the plastic limit The
lump can be formed without crumbling when drier
than the plastic limit
2.6 Preprocessing of Materials
Some soil liner materials are ready to be used for final construction immediately after they
are excavated from the borrow pit. However, most materials require some degree of processing
prior to placement and compaction of the soil.
2.6.1 Water Content Adjustment
Soils that are too wet must first be dried. If the water content needs to be reduced by no
more than about three percentage points, the soil can be dried after it has been spread in a loose lift
just prior to compaction. If the water content must be reduced by more than about 3 percentage
points, it is recommended that drying take place in a separate processing area. The reason for
drying in a separate processing area is to allow adequate time for the soil to dry uniformly and to
facilitate mixing of the material during drying. The soil to be dried is spread in a lift about 225 to
300 mm (9 to 12 in.) thick and allowed to dry. Water content is periodically measured using one
or more of the methods listed in Table 2.2. The contractor's CQC personnel should check the soil
periodically to determine when the soil has reached the proper water content.
The CQA inspectors should check to be sure that the soil is periodically mixed with a disc
or rototiller to ensure uniform drying. The soil cannot be considered to be ready for placement and
compaction unless the water is uniformly distributed; water content measurements alone do not
ensure that water is uniformly distributed within the soil.
67
-------
If the soil must be moistened prior to compaction, the same principles discussed above for
drying apply; water content adjustment in a separate preprocessing area is recommended if the
water content must be increased by more than about 3 percentage points. Inspectors should be
careful to verify that water is distributed uniformly to the soil (a spreader bar on the back of a water
truck is the recommended device for moistening soil uniformly), that the soil is periodically mixed
with a disc or rototiller, and that adequate time has been allowed for uniform hydration of the soil.
If the water content is increased by more than three percentage points, at least 24 to 48 hours
would normally be required for uniform absorption of water and hydration of soil particles. The
construction specifications may limit the type of water that can be used; in some cases,
contaminated water, brackish water, or sea water is not allowed.
2.6.2 Removal of Oversize Particles
Oversized stones and rocks should be removed from the soil liner material. Stones and
rocks interfere with compaction of the soil and may create undesirable pathways for fluid to flow
through the soil liner. The construction specifications should stipulate the maximum allowable size
of particles in the soil liner material.
Oversized particles can be removed with mechanical equipment (e.g., large screens) or by
hand. Inspectors should examine the loose lift of soil after the contractor has removed oversized
particles to verify that oversized particles are not present. Sieve analyses alone do not provide
adequate assurance that oversized materials have been removed — careful visual inspection for
oversized material should be mandatory.
2.6.3 Pulverization of Clods
Some specifications for soil liners place limitations on the maximum size of chunks or
clods of clay present in the soil liner material. Discs, rototillers, and road recyclers are examples of
mechanical devices that will pulverize clods in a loose lift. Visual inspection of the loose lift of
material is normally performed to ensure that clods of soil have been pulverized to the extent
required in the construction specifications. Inspectors should be able to visually examine the entire
surface of a loose lift to determine whether clods have been adequately processed. No standard
method exists for determining clod size. Inspectors normally measure the dimensions of an
individual clod with a ruler.
2.6.4 Homogenizing Soils
CQC and CQA are very difficult to perform for heterogeneous materials. It may be
necessary to blend and homogenize soils prior to their use in constructing soil liners in order to
maintain proper CQC and CQA. Soils can be blended and homogenized in a pugmill. The best
way to ensure adequate mixing of materials is through visual inspection of the mixing process
itself.
2.6.5 Bentonite
Bentonite is a common additive to soil liner materials that do not contain enough clay to
achieve the desired low hydraulic conductivity. Inspectors must ensure that the bentonite being
used for a project is in conformance with specifications (i.e., is of the proper quality and gradation)
and that the bentonite is uniformly mixed with soil in the required amounts.
The parameters that are specified for the bentonite quality vary considerably from project to
project. The construction specifications should stipulate the criteria to be met by the bentonite and
68
-------
the relevant test methods. The quality of bentonite is usually measured with some type of
measurement of water adsorption ability of the clay. Direct measurement of water adsorption can
be accomplished using the plate water adsorption test (ASTM E-946). This test is used primarily
in the taconite iron ore industry to determine the effectiveness of bentonite, which is used as a
binder during the pelletizing process to soak up excess water in the ore. Brown (1992) reports that
thousands of plate water adsorption tests have been performed on bentonite, but experience has
been that the test is time consuming, cumbersome, and extremely sensitive to variations in the test
equipment and test conditions. The plate water adsorption test is not recommended for CQC/CQA
of soil liners.
Simple, alternative tests that provide an indirect indication of water adsorption are available.
One indirect test for water adsorption is measurement of Atterberg (liquid and plastic) limits via
ASTM D-4318. The higher the quality of the bentonite, the higher the liquid limit and plasticity
index. Although liquid and plastic limits tests are very common for natural soils, they have not
been frequently used as indicators of bentonite quality in the bentonite industry. A commonly-used
test in the bentonite industry is the free swell test. The free swell test is used to determine the
amount of swelling of bentonite when bentonite is exposed to water in a glass beaker.
Unfortunately, there is currently no ASTM test for determining free swell of bentonite, although
one is under development. Until such time as an ASTM standard is developed, the bentonite
supplier may be consulted for a suggested testing procedure.
The liquid limit test and free swell test are recommended as the principal quality control
tests for the quality of bentonite being used on a project. There are no widely accepted cutoff
values for the liquid limit and free swell. However, the following is offered for the information of
CQC and CQA inspectors. The liquid limit of calcium bentonite is frequently in the range of 100 to
150%. Sodium bentonite of medium quality is expected to have a liquid limit of approximately 300
to 500%. High-quality sodium bentonite typically has a liquid limit in the range of about 500 to
700%. According to Brown (1992), calcium bentonites usually have a free swell of less than 6 cc.
Low-grade sodium bentonites typically have a free swell of 8 - 15 cc. High-grade bentonites often
have free swell values in the range of 18 to 28 cc. If high-grade sodium bentonite is to be used on
a project, inspectors should expect that the liquid limit will be > 500% and the free swell will be >
18 cc.
The bentonite must usually also meet gradational requirements. The gradation of the dry
bentonite may be determined by carefully sieving the bentonite following procedures outlined in
ASTM D-422. The CQA inspector should be particularly careful to ensure that the bentonite has
been pulverized to the extent required in the construction specifications. The degree of
pulverization is frequently overlooked. Finely-ground, powdered bentonite will behave differently
when blended into soil than more coarsely ground, granular bentonite. CQC/CQA personnel
should be particularly careful to make sure that the bentonite is sufficiently finely ground and is not
delivered in too coarse a form (per project specifications); sieve tests on the raw bentonite received
at a job site are recommended to verify gradation of the bentonite.
The bentonite supplier is expected to certify that the bentonite meets the specification
requirements. However, CQA inspectors should perform their own tests to ensure compliance
with the specifications. The recommended CQA tests and testing frequencies for bentonite quality
and gradation are summarized in Table 2.6.
69
-------
Table 2.6 - Recommended Tests on Bentonite to Determine Bentonite Quality and Gradation
Parameter Frequency Test Method
Liquid Limit 1 per Truckload ASTM D-4318, "Liquid Limit,
or 2 per Rail Car Plastic Limit, and Plasticity Index
of Soils"
Free Swell 1 per Truckload No Standard Procedure Is Available
or 2 per Rail Car
Grain Size of Dry Bentonite 1 per Truckload ASTM D-422, "Particle Size
or 2 per Rail Car Analysis of Soil"
2.6.5.1 Pugmill Mixing
A pugmill is a device for mixing dry materials. A schematic diagram of a typical pugmill is
shown in Fig. 2.30. A conveyor belt feeds soil into a mixing unit, and bentonite drops downward
into the mixing unit The materials are mixed in a large box that contains rotating rods with mixing
paddles. Water may be added to the mixture in the pugmill, as well.
The degree of automation of pugmills varies considerably. The most sophisticated
pugmills have computer-controlled devices to monitor the amounts of the ingredients being mixed.
CQA personnel should monitor the controls on the mixing equipment.
2.6.5.2 In-Place Mixing
An alternative mixing technique is to spread the soil in a loose lift, distribute bentonite on
the surface, and mix the bentonite and soil using a rototiller or other mixing equipment. There are
several potential problems with in-place mixing. The mixing equipment may not extend to an
adequate depth and may not fully mix the loose lift of soil with bentonite. Alternatively, the mixing
device may dig top deeply into the ground and actually mix the loose lift in with underlying
materials. Bentonite (particularly powdered bentonite) may be blown away by wind when it is
placed on the surface of a loose lift, thus reducing the amount of bentonite that is actually
incorporated into the soil. The mixing equipment may fail to pass over all areas of the loose lift
and may inadequately mix certain portions of the loose lift. Because of these problems many
engineers believe that pugmill mixing provides a more reliable means for mixing bentonite with
soil. CQA personnel should carefully examine the mixing process to ensure that the problems
outlined above, or other problems, do not compromise the quality of the mixing process. Visual
examination of the mixture to verify plasticity (see Section 2.5 and Table 2.5) is recommended.
2.6.5.3 Measuring Bentonite Content
The best way to control the amount of bentonite mixed with soil is to measure the relative
weights of soil and bentonite blended together at the time of mixing. After bentonite has been
70
-------
mixed with soil there are several techniques available to estimate the amount of bentonite in the
soil. None of the techniques are particularly easy to use in all situations.
The recommended technique for measuring the amount of bentonite in soil is the methylene
blue test (Alther, 1983). The methylene blue test is a type of titration test. Methylene blue is
slowly titrated into a material and the amount of methylene blue required to saturate the material is
determined. The more bentonite in the soil the greater the amount of methylene blue that must be
added to achieve saturation. A calibration curve is developed between the amount of methylene
blue needed to saturate the material and the bentonite content of the soil. The methylene blue test
works very well when bentonite is added into a non-clayey soil. However, the amount of
methylene blue that must be added to the soil is a function of the amount of clay present in the soil.
If clay minerals other than bentonite are present, the clay minerals interfere with the determination
of the bentonite content. There is no standard methylene blue test; the procedure outlined in Alther
(1983) is suggested until such time as a standard test method is developed.
aggregate hopper /
.
in
2
belt
encoders
Interference. ,
fit \l
aggregate belt
water tank
water pump/
flow meter
encoder
Figure 2.30 - Schematic Diagram of Pugmill
Another type of test that has been used to estimate bentonite content is the filter press test.
This test is essentially a water absorbency test: the greater the amount of clay in a soil, the greater
the water holding capacity. Like the methylene blue test, the filter press test works well if
bentonite is the only source of clay in the soil. No specific test procedure was available at the time
of this writing.
71
-------
Measurement of hydraulic conductivity provides a means for verifying that enough
bentomte has been added to the soil to achieve the desired low hydraulic conductivity. If
insufficient bentonite has been added, the hydraulic conductivity should be unacceptably large.
However, just because the hydraulic conductivity is acceptably low for a given sample does not
necessarily mean that the required amount of bentonite has been added to the soil at all locations.
Indeed, extra bentonite beyond the minimum amount required is added to soil so that there will be
sufficient bentonite present even at those locations that are "lean" in bentonite.
The recommended tests and testing frequencies to verify proper addition of bentonite are
summarized in Table 2.7. However, the CQA personnel must realize that the amount of testing
depends on the degree of control in the mixing process: the more control during mixing, the less is
the need for testing to verify the proper bentonite content.
Table 2.7 - Recommended Tests to Verify Bentonite Content
Parameter Frequency Test Method
Mcthylene Blue Test 1 per 1,000 m3 A1*er (1983)
Compaction Curve for 1 per 5,000 m3 Per Project Specifications, e.g.,
SoiI-Bentonite Mixture ASTM D-698 or D-1557
(Needed To Prepare Hydraulic
Conductivity Test Specimen)
Hydraulic Conductivity 3/ha/Lift ASTM D-5084, "Hydraulic
of Soil-Bentonite Mixture (I/Acre/Lift) Conductivity of Saturated Porous
Compacted to Appropriate Materials Using a Flexible Wall
Water Content and Dry Permeameter"
Unit Weight
Note: 1 yd3 = 0.76m3
2.6.6 Stockpiling Soils
After the soil has been preprocessed it is usually necessary to ensure that the water content
does not change prior to use. The stockpiles can be of any size or shape. Small stockpiles should
be covered so that the soil cannot dry or wet. For large stockpiles, it may not be necessary to
cover the stockpile, particularly if the stockpile is sloped to promote drainage, moisture is added
occasionally to offset drying at the surface, or other steps are taken to minimize wetting or drying
of the stockpiled soil. &
2.7 Placement of Loose Lift of Soil
After a soil has been fully processed, the soil is hauled to the final placement area. Soil
should not be placed in adverse weather conditions, e.g., heavy rain. Inspectors are usually
responsible for documenting weather conditions during all earthwork operations. The surface on
72
-------
which the soil will be placed must be properly prepared and the material must be inspected after
placement to make sure that the material is suitable. Then the CQA inspectors must also verify that
the lift is not too thick. For side slopes, construction specifications should clearly state whether
lifts are parallel to the slope or horizontal. For slopes inclined at 3(H):1(V) or flatter, lifts are
usually parallel to the slope. For slopes inclined at 2(H):1(V) or steeper, lifts are usually
horizontal. However, horizontal lifts may present problems because the hydraulic conductivity for
flow parallel to lifts is expected to be somewhat greater than for flow perpendicular to lifts. Details
of testing are described in the following subsections.
Transport vehicles can pick up contaminants while hauling material from the borrow source
or preprocessing area. If this occurs, measures should be taken to prevent contaminants from
falling off transport vehicles into the soil liner material. These measures may include restricting
vehicles to contaminant free haul roads or removing contaminants before the vehicle enters the
placement area.
2.7.1 Surface Scarification
Prior to placement of a new lift of soil, the surface of the previously compacted lift of soil
liner should be roughened to promote good contact between the new and old lifts. Inspectors
should observe the condition of the surface of the previously compacted lift to make sure that the
surface has been scarified as required in the construction specifications. When soil is scarified it is
usually roughened to a depth of about 25 mm (1 in.). In some cases the surface may not require
scarification if the surface is already rough after the end of compaction of a lift. It is very important
that CQA inspectors ensure that the soil has been properly scarified if construction specifications
require scarification. If the soil is scarified, the scarified zone becomes part of the loose lift of soil
and should be counted in measuring the loose lift thickness.
2.7.2 Material Tests and Visual Inspection
2.7.2.1 Material Tests
After a loose lift of soil has been placed, samples are periodically taken to confirm the
properties of the soil liner material. These samples are in addition to samples taken from the
borrow area (Table 2.3). The types of tests and frequency of testing are normally specified in the
CQA documents. Table 2.8 summarizes recommended minimum tests and testing frequencies.
Samples of soils can be taken either on a grid pattern or on a random sampling pattern (see Section
2.8.3.2). Statistical tests and criteria can be applied but are not usually applied to soil liners in part
because enough data have to be gathered to apply statistics, and yet decisions have to be made
immediately, before very much data are collected.
2.7.2.2 Visual Observations
Inspectors should position themselves near the working face of soil liner material as it is
being placed. Inspectors should look for deleterious materials such as stones, debris, and organic
matter. Continuous inspection of the placement of soil liner material is recommended to ensure that
the soil liner material is of the proper consistency.
2.7.2.3 Allowable Variations
Tests on soil liner materials may occasionally fail to conform with required specifications.
It is unrealistic to think that 100% of a soil liner material will be in complete conformance with
specifications. For example, if the construction documents require a minimum plasticity index it
73
-------
may be anticipated that a small fraction of the soil (such as pockets of sandy material) will fail to
conform with specifications. It is neither unusual nor unexpected that occasional failing material
will be encountered m soil liners. Occasional imperfections in soil liner materials are expected.
Indeed, one of the reasons why multiple lifts are used in soil liners is to account for the inevitable
variations in the materials of construction employed in building soil liners. Occasional deviations
from construction specifications are not harmful. Recommended maximum allowable variations
(failing tests) are listed in Table 2.9.
Table 2.8 - Recommended Materials Tests for Soil Liner Materials Sampled after Placement in a
Loose Lift (Just Before Compaction)
Parameter Test Method
Minimum Testing Frequency
Percent Fines ASTM D-l 140 1 per 800 m3 (Notes 2 & 5)
(Note 1)
PerieTnt G^vel AS™ D'422 1 Per 800 m3 (Notes 2 & 5)
(Note 3)
Liquid & Plastic Limits ASTMD-4318 1 per 800 m3 (Notes 2 & 5)
Percent Bentonite Alther(1983) 1 per 800 m3 (Notes 2 & 5)
(Note4) '
Compaction Curve As Specified 1 per 4,000 m3 (Note 5)
Construction Oversight Observation Continuous
Notes:
1. Percent fines is defined as percent passing the No. 200 sieve.
2. In addition, at least one test should be performed each day that soil is placed, and additional tests should be
performed on any suspect material observed by CQA personnel.
3. Percent gravel is defined as percent retained on the No. 4 sieve.
4. This test is only applicable to soil-bentonite liners.
5. 1 yd3 = 0.76m3.
74
-------
Table 2.9 - Recommended Maximum Percentage of Failing Material Tests
Parameter Maximum Allowable Percentage of Outliers
Atterberg Limits 5% and Outliers Not Concentrated in One Lift or One Area
Percent Fines 5% and Outliers Not Concentrated in One Lift or One Area
Percent Gravel 10% and Outliers Not Concentrated in One Lift or One Area
Clod Size 10% and Outliers Not Concentrated in One Lift or One Area
Percent Bentonite 5% and Outliers Not Concentrated in One Lift or One Area
Hydraulic Conductivity of 5% and Outliers Not Concentrated in One Lift or One Area
Laboratory Compacted Soil
2.7.2.4 Corrective Action
If it is determined that the materials in an area do not conform with specifications, the first
step is to define the extent of the area requiring repair. A sound procedure is to require the
contractor to repair the lift of soil out to the limits defined by passing CQC/CQA tests. The
contractor should not be allowed to guess at the extent of the area that requires repair. To define
the limits of the area that requires repair, additional tests are often needed. Alternatively, if the
contractor chooses not to request additional tests, the contractor should repair the area that extends
from the failing test out to the boundaries defined by passing tests.
The usual corrective action is to wet or dry the loose lift of soil in place if the water content
is incorrect. The water must be added uniformly, which requires mixing the soil with a disc or
rototiller (see Section 2.6.1). If the soil contains oversized material, oversized particles are
removed from the material (see Section 2.6.2). If clods are too large, clods can be pulverized in
the loose lift (see Section 2.6.3). If the soil lacks adequate plasticity, contains too few fines,
contains too much gravel, or lacks adequate bentonite, the material is normally excavated and
replaced.
2.7.3 Placement and Control of Loose Lift Thickness
Construction specifications normally place limits on the maximum thickness of a loose lift
of soil, e.g., 225 mm (9 in.). The thickness of a loose lift should not exceed this value with
normal equipment. The thickness of a loose lift may be determined in several ways. One
technique is for an inspector standing near the working face of soil being placed to observe the
thickness of the lift. This is probably the most reliable technique for controlling loose lift thickness
for CQA inspectors. If there is a question about loose lift thickness one should dig a pit through
the loose lift of soil and into the underlying layer. A cross-beam is used to measure the depth from
the surface of a loose lift to the top of the previously compacted lift. If the previously compacted
lift was scarified, the zone of scarification should be counted in the loose lift thickness for the new
layer of soil. Continuous observation of loose lift thickness is recommended during placement of
- 75
-------
soil liners.
Some earthwork contractors control lift thickness by driving grade stakes into the subsoil
and marking the grade stake to indicate the proper thickness of the next layer. This practice is very
convenient for equipment operators because they can tell at a glance whether the loose lift thickness
is correct. However, this practice is strongly discouraged for the second and subsequent lifts of a
soil liner because the penetrations into the previously-compacted lift made by the grade stakes must
be repaired. Also, any grade stakes or fragments from grade stakes left in a soil liner could
puncture overlying geosynthetics. Repair of holes left by grade stakes is very difficult because one
must dig through the loose lift of soil to expose the grade stake, remove the grade stake without
breaking the stake and leaving some of the stake in the soil, backfill the hole left by the grade stake
and then replace the loose soil in the freshly-placed lift. For the first lift of soil liner repair of
grade stake holes may not be relevant (depending on the subgrade and what its function is) but
grade stakes are discouraged even for the first lift of soil because the stakes may be often broken
off and incorporated into the soil. Grade stakes resting on a small platform or base do not need to
be driven into the underlying material and are, therefore, much more desirable than ordinary grade
stakes. If grade stakes are used, it is recommended that they be numbered and accounted for at the
end ol each shift; this will provide verification that grade stakes are not being abandoned in the fill
material.
The recommended survey procedure for control of lift thickness involves laser sources and
receivers. A laser beam source is set at a known elevation, and reception devices held by hand on
rods or mounted to grading equipment are used to monitor lift thickness. However, lasers cannot
be used at all sites. For instance, the liner may need to be a minimum distance above rock, and the
grade lines may follow the contours of underlying rock. Further, every site has areas such as
corners, sumps, and boundaries of cells, which preclude the use of lasers.
For those areas where lasers cannot be used, it is recommended that either flexible plastic
grade stakes or metallic grade stakes (numbered and inventoried as part of the QA/QC process) be
used. It is preferable if the stakes are mounded on a base so that the stakes do not have to be
driven into the underlying lift. Repair of grade stake holes should be required; the repairs should
be periodically inspected and the repairs documented. Alternatively (and preferably for small
areas), spot elevations can be obtained on the surface of a loose lift with conventional level and rod
equipment, and adjustments made by the equipment operator based on the levels.
j AJS? is Placed> it: is usually dumped into a heap at the working face and spread with
dozers. QA/QC personnel should stand in front of the working face to observe the soil for
oversized materials or other deleterious material, to visually observe loose lift thickness, and to
make sure that the dozer does not damage an underlying layer.
2.8 Remolding and Compaction of Soil
2.8.1 Compaction Equipment
The important parameters concerning compaction equipment are the type and weight of the
compactor, the characteristics of any feet on the drum, and the weight of the roller per unit length
ot drummed surface. Sometimes construction specifications will stipulate a required type of
compactor or minimum weight of compactor. If this is the case inspectors should confirm that the
compaction equipment is in conformance with specifications. Inspectors should be particularly
cognizant of the weight of compactor and length of feet on drummed rollers. Heavy compactors
with long feet that fully penetrate a loose lift of soil are generally thought to be the best type of
compactor to use for soil liners. Footed rollers may not be necessary or appropriate for some
76
-------
bentonite-soil mixes; smooth-drum rollers or rubber tired rollers may produce best results for soil-
bentonite mixtures that do not require kneading or remolding to achieve low hydraulic conductivity
but only require densification.
Some compactors are self-propelled while other compactors are towed. Towed, footed
rollers are normally ballasted by filling the drum with water to provide weight that will enable
significant compactive effort to be delivered to the soil. Inspectors should be very careful to
determine whether or not all drums on towed rollers have been filled with liquid.
Compacting soil liners on side slopes can present special challenges, particularly for slopes
inclined at 3(H):1(V) or steeper. Inspectors should observe side-slope compaction carefully and
watch for any tendency for the compactor to slip down slope or for slippage or cracking to take
place in the soil. Inspectors should also be watchful to make sure that adequate compactive effort
is delivered to the soil. For soils compacted in lifts parallel to the slope, the first lift of soil should
be "knitted" into existing subgrade to minimize a preferential flow path along the interface and to
minimize development of a potential slip plane.
Footed rollers can become clogged with soil between the feet. Inspectors should examine
the condition of the roller to make sure that the space between feet is not plugged with soil. In
addition, compaction equipment is intended to be operated at a reasonable speed. The maximum
speed of the compactor should be specified in the construction specifications. CQC and CQA
personnel should make sure the speed of the equipment is not too great.
When soils are placed directly on a fragile layer, such as a geosynthetic material, or a
drainage material, great care must be taken in placing and compacting the first lift so as not to
damage the fragile material or mix clay in with the underlying drainage material. Often, the first lift
of soil is considered a sacrificial lift that is placed, spread with dozers, and only nominally
compacted with the dozers or a smooth-drum or rubber-tire roller. QA/QC personnel should be
particularly careful to observe all placement and compaction operations of the first lift of soil for
compacted soil liners placed directly on a geosynthetic material or drainage layer.
It is not uncommon for a contractor to use more than one type of compaction equipment on
a project. For example, initial compaction may be with a heavy roller having long feet that fully
penetrate a loose lift of soil. Later, the upper part of a lift may be compacted with a heavy rubber-
tired roller or other equipment that is particularly effective in compacting near-surface materials.
, E -
2.8.2 Number of Passes
The compactive effort delivered by a roller is a function of the number of passes of the
roller over a given area of soil. A pass may defined as one pass of the.construction equipment or
one pass of a drum over a given point in the soil liner. It does not matter whether a pass is defined
as a pass of the equipment or a pass of a drum, but the construction specifications and/or CQA plan
should define what is meant by a pass. Normally, one pass of the vehicle constitutes a pass for
self-propelled rollers and one pass of a drum constitutes a pass for towed rollers.
Some construction documents require a minimum coverage. Coverage (C) is defined as
follows:
C = [Af/Ad|xNxlOO% (2.4)
where N is the number of passes of the roller, Af is the sum of the area of the feet on the drums of
the roller, and Ad is the area the drum itself. Construction specifications sometimes require 150% -
77
-------
200% coverage of the roller. For a given roller and minimum percent coverage, the minimum
number of passes (N) may be computed.
The number of passes of a compactor over the soil can have an important influence on the
overall hydraulic conductivity of the soil liner. It is recommended that periodic observations be
made of the number of passes of the roller over a given point. Approximately 3 observations per
hectare per lift (one observation per acre per lift) is the recommended frequency of measurement.
The minimum number of passes that is reasonable depends upon many factors and cannot be stated
in general terms. However, experience has been that at least 5 to 15 passes of a compactor over a
given point is usually necessary to remold and compact clay liner materials thoroughly.
2.8.3 Water Content and Drv Unit Weighf
2.8.3.1 Water Content and Unit Weight Tests
One of the most important CQA tests is measurement of water content and dry unit
weight. Methods of measurement were discussed in Section 2.3. Recommended testing
frequencies are listed in Table 2.10. It is stressed that the recommended testing frequencies are the
minimum values. Some judgment should be applied to these numbers, and the testing frequencies
should be increased or kept at the minimum depending on the specific project and other QA/QC
tests and observations. For example, if hydraulic conductivity tests are not performed on
undisturbed samples (see Section 2.8.4.2), more water content/density tests may be required than
the usual minimum.
2.8.3.2 Sampling Patterns
There are several ways in which sample locations may be selected for water content and
unit weight tests. The simplest and least desirable method is for someone in the field to select
locations at the time samples must be taken. This is undesirable because the selector may introduce
a bias into the sampling pattern. For example, perhaps on the previous project soils of one
particular color were troublesome. If the individual were to focus most of the tests on the current
project on soils of that same color a bias might be introduced.
A common method of selecting sample locations is to establish a grid pattern. The grid
pattern is simple and ensures a high probability of locating defective areas so long as the defective
areas are of a size greater than or equal to the spacing between the sampling points. It is important
to stagger the grid patterns in successive lifts so that sampling points are not at the same location in
each lift One would not want to sample at the same location in successive lifts because repaired
sample penetrations would be stacked on top of one another. The grid pattern sampling procedure
is the simplest one to use that avoids the potential for bias described in the previous paragraph.
T. ui A third alternative for selecting sampling points is to locate sampling points randomly.
Tables and examples are given in Richardson (1992). It is recommended that no sampling point be
located within 2 meters of another sampling point. If a major portion of the area to be sampled has
been omitted as a result of the random sampling process, CQA inspectors may add additional
points to make sure the area receives some testing. Random sampling is sometimes preferred on
large projects where statistical procedures will be used to evaluate data. However, it can be
demonstrated that for a given number of sampling points, a grid pattern will be more likely to
detect a problem area provided that the dimensions of the problem area are greater than or equal to
the spacing between sampling points. If the problem area is smaller than the spacing between
sampling points, the probability of locating the problem area is approximately the same with both a
grid pattern and a random pattern of sampling.
78
-------
Table 2.10 - Recommended Tests and Observations on Compacted Soil
Parameter
Test Method
Minimum Testing Frequency
Water Content (Rapid)
(Notel)
Water Content
(Note 3)
Total Density (Rapid)
(Note 4)
Total Density
(Note 5)
Number of Passes
Construction Oversight
ASTM D-3017
ASTM D-4643
ASTM D-4944
ASTM D-4959
ASTM D-2216
ASTM D-2922
ASTM D-2937
ASTM D-1556
ASTM D-1587
ASTM D-2167
Observation
Observation
13/ha/lift(5/acre/lift)
(Notes 2 & 7)
One in every 10 rapid water
content tests
(Notes 3 & 7)
13/ha/lift(5/acre/lift)
(Notes 2, 4 & 7)
One in every 20 rapid density tests
(Notes 5, 6, & 7)
3/ha/lift (I/acre/lift)
(Notes 2 & 7)
Continuous
Notes:
1. ASTM D-3017 is a nuclear method, ASTM D-4643 is microwave oven drying, ASTM D-4944 is a calcium
carbide gas pressure tester method, and ASTM D-4959 is a direct heating method. Direct water content
determination (ASTM D-2216) is the standard against which nuclear, microwave, or other methods of
measurements are calibrated for on-site soils.
2. In addition, at least one test should be performed each day soil is compacted and additional tests should be
performed in areas for which CQA personnel have reason to suspect inadequate compaction.
3. Every tenth sample tested with ASTM D-3017, D-4643, D-4944, or D^959 should be also tested by direct oven
drying (ASTM D-2216) to aid in identifying any significant, systematic calibration errors.
4. ASTM D-2922 is a nuclear method and ASTM D-2937 is the drive cylinder method. These methods, if used,
should be calibrated against the sand cone (ASTM D-1556) or rubber balloon (ASTM D-2167) for on-site soils.
Alternatively, the sand cone or rubber balloon method can be used directly.
5. Every twentieth sample tested with D-2922 should also be tested (as close as possible to the same test location)
with the sand cone (ASTM D-1556) or rubber balloon (ASTM D-2167) to aid in identifying any systematic
calibration errors with D-2922. ,
6. ASTM D-1587 is the method for obtaining an undisturbed sample. The section of undisturbed sample can be
cut or trimmed from the sampling tube to determine bulk density. This method should not be used for soils
containing any particles > 1/6-th the diameter of the sample.
7. 1 acre = 0.4 ha.
79
-------
No matter which method of determining sampling points is selected, it is imperative that
CQA inspectors have the responsibility to perform additional tests on any suspect area. The
number of additional testing locations that are appropriate varies considerably from project to
project.
2.8.3.3 Tests with Different Devices to Minimize Systematic Errors
Some methods of measurement may introduce a systematic error. For example, the nuclear
device for measuring water content may consistently produce a water content measurement that is
too high if there is an extraneous source of hydrogen atoms besides water in the soil. It is
important that devices that may introduce a significant systematic error be periodically correlated
with measurements that do not have such error. Water content measurement tests have the greatest
potential for systematic error. Both the nuclear method as well as microwave oven drying can
produce significant systematic error under certain conditions. Therefore, it is recommended that if
the nuclear method or any of the rapid methods of water content measurement (Table 2.2) are used
to measure water content, periodic correlation tests should be made with conventional overnight
oven drying (ASTM D-2216).
It is suggested that at the beginning of a project, at least 10 measurements of water content
be determined on representative samples of the site-specific soil using any rapid measurement
method to be employed on the project as well as ASTM D-2216. After this initial correlation, it is
suggested (see Tables 2.10) that one in ten rapid water content tests be crossed check with
conventional overnight oven drying. At the completion of a project a graph should be presented
that correlates the measured water content with a rapid technique against the water content from
conventional overnight oven drying. ' .,
Some methods of unit weight measurement may also introduce bias. For example, the
nuclear device may not be properly calibrated and could lead to measurement of a unit weight that
is either too high or too low. It is recommended that unit weight be measured independently on
occasion to provide a check against systematic errors. For example, if the nuclear device is the
primary method of density measurement being employed on a project, periodic measurements of
density with the sand cone or rubber balloon device can be used to check the nuclear device.
Again, a good practice is to perform about 10 comparative tests on representative soil prior to
construction. During construction, one in every 20 density tests (see Table 2.10) should be
checked with the sand cone or rubber balloon. A graph should be made of the unit weight
measured with the nuclear device versus the unit weight measured with the sand cone or rubber
balloon device to show the correlation. One could either plot dry unit weight or total unit weight
for the correlation. Total unit weight in some ways is more sensible because the methods of
measurement are actually total unit weight measurements; dry unit weight is calculated from the
total unit weight and water content (Eq. 2.1.).
2.8.3.4 Allowable Variations and Outliers
There are several reasons why a field water content or density test may produce a failing
result, i.e., value outside of the specified range. Possible causes for a variation include a human
error in measurement of water content or dry unit weight, natural variability of the soil or the
compaction process leading to an anomaly at an isolated location, limitations in the sensitivity and
repeatability of the test methods, or inadequate construction procedures that reflect broader-scale
deficiencies.
Measurement errors are made on every project. From time to time it can be expected that
CQC and CQA personnel will incorrectly measure either the water content or the dry unit weight.
80
-------
Periodic human errors are to be expected and should be addressed in the CQA plan.
If it is suspected that a test result is in error, the proper procedure for rectifying the error
should be as follows. CQC or CQA personnel should return to the point where the questionable
measurement was obtained. Several additional tests should be performed in close proximity to the
location of the questionable test. If all of the repeat tests provide satisfactory results the
questionable test result may be disregarded as an error. Construction quality assurance documents
should specify the number of tests required to negate a blunder. It is recommended that
approximately 3 passing tests be required to negate the results of a questionable test.
One of the main reasons why soil liners are built of multiple lifts is a realization that the
construction process and the materials themselves vary. With multiple lifts no one particular point
in any one lift is especially significant even if that point consists of unsatisfactory material or
improperly compacted material. It should be expected that occasional deviations from construction
specifications will be encountered for any soil liner. In fact, if one were to take enough soil
samples, one can rest assured that a failing point on some scale would be located.
Measurement techniques for compacted soils are imperfect and produce variable results.
Turnbull et al. (1966) discuss statistical quality control for compacted soils. Noorany (1990)
describes 3 sites in the San Diego area for which 9 testing laboratories measured water content and
percent compaction on the same fill materials. The ranges in percent compaction were very large:
81-97% for Site 1,77-99% for Site 2, and 89-103% for Site 3.
Hilf (1991) summarizes statistical data from 72 earth dams; the data show that the standard
deviation in water content is typically 1 to 2%, and the standard deviation in dry density is typically
0.3 to 0.6 kN/m^ (2 to 4 pcf). Because the standard deviations are themselves on the same order
as the allowable range of these parameters in many earthwork specifications, it is statistically
inevitable that there will be some failing tests no matter how well built the soil liner is.
It is unrealistic to expect that 100% of all CQA tests will be in compliance with
specifications. Occasional deviations should be anticipated. If there are only a few randomly-
located failures, the deviations in no way compromise the quality or integrity of a multiple-lift liner.
The CQA documents may provide an allowance for an occasional failing test. The
documents may stipulate that failing tests not be permitted to be concentrated in any one lift or in
any one area. It is recommended that a small percentage of failing tests be allowed rather than
insisting upon the unrealistic requirement that 100% of all tests meet project objectives.
Statistically based requirements provide a convenient yet safe and reliable technique for handling
occasional failing test results.. However, statistically based methods require that enough data be
generated to apply statistics reliably. Sufficient data to apply statistical methods may not be
available, particularly in the early stages of a project.
Another approach is to allow a small percentage of outliers but to require repair of any area
where the water content is far too low or high or the dry unit weight is far too low. This approach
is probably the simplest to implement — recommendations are summarized in Table 2.11.
81
-------
Table 2.11 - Recommended Maximum Percentage of Failing Compaction Tests
Parameter Maximum Allowable Percentage of Outliers
Water Content 3 % and Outliers Not Concentrated in One Lift or One Area,
and No Water Content Less than 2% or More than 3% of
the Allowable Value
Dry Density 3 % and Outliers Not Concentrated in One Lift or One Area,
and No Dry Density Less than 0.8 kN/m^ (5 pcf) Below the
Required Value
Number of Passes 5% and Outliers Not Concentrated in One Lift or One Area
2.8.3.5 Corrective Action
If it is determined that an area does not conform with specifications and that the area needs
to be repaired, the first step is to define the extent of the area requiring repair. The recommended
procedure is to require the contractor to repair the lift of soil out to the limits defined by passing
CQC and CQA tests. The contractor should not be allowed to guess at the extent of the area that
requires repair. To define the limits of the area that requires repair, additional tests are often
needed. Alternatively, if the contractor chooses not to request additional tests, the contractor
should repair the area that extends from the failing test out to the boundaries defined by passing
tests.
The usual problem requiring corrective action at this stage is inadequate compaction of the
soil. The contractor is usually able to rectify the problem with additional passes of the compactor
over the problem area.
2.8.4 Hydraulic Conductivity Tests on Undisturbed Samples
Hydraulic conductivity tests are often performed on "undisturbed" samples of soil obtained
from a single lift of compacted soil liner. Test specimens are trimmed from the samples and/are
permeated in the laboratory. Compliance with the stated hydraulic conductivity criterion is
checked.
This type of test is given far too much weight in most QA programs. Low hydraulic
conductivity of samples taken from the liner is necessary for a well-constructed liner but is not
sufficient to demonstrate that the large-scale, field hydraulic conductivity is adequately low. For
example, Elsbury et al. (1990) measured hydraulic conductivities on undisturbed samples of a
poorly constructed liner that averaged 1 x lO"9 cm/s, and yet the actual in-field value was 1 x 10'5
cm/s. The cause for the discrepancy was the existence of macro-scale flow paths in the field that
were not simulated in the small-sized (75 mm or 3 in. diameter) laboratory test specimens.
Not only does the flow pattern through a 75-mm-diameter test specimen not necessarily
reflect flow patterns on a larger field scale, but the process of obtaining a sample for testing
inevitably disturbs the soil. Layers are distorted, and gross alterations occur if significant gravel is
82
-------
present in the soil. The process of pushing a sampling tube into the soil densities the soil, which
lowers its hydraulic conductivity. The harder and drier the soil, the greater the disturbance. As a
result of these various factors, the large-scale, field hydraulic conductivity is almost always greater
than or equal to the small-scale, laboratory-measured hydraulic conductivity. The difference
between values from a small laboratory scale and a large field scale depends on the quality of
construction — the better the quality of construction, the less the difference.
Laboratory hydraulic conductivity tests on undisturbed samples of compacted liner can be
valuable in some situations. For instance, for soil-bentonite mixes, the laboratory test provides a
check on whether enough bentonite has been added to the mix to achieve the desired hydraulic
conductivity. For soil liners in which a test pad is not constructed, the laboratory tests provide
some verification that appropriate materials have been used and compaction was reasonable (but
hydraulic conductivity tests by themselves do not prove this fact).
Laboratory hydraulic conductivity tests constitute a major inconvenience because the tests
usually take at least several days, and sometimes a week or two, to complete. Their value as QA
tools is greatly diminished by the long testing time ~ field construction personnel simply cannot
wait for the results of the tests to proceed with construction, nor would the QA personnel
necessarily want them to wait because opportunities exist for damage of the liner as a result of
desiccation. Thus, one should give very careful consideration as to whether the laboratory
hydraulic conductivity tests are truly needed for a given project and will serve a sufficiently useful
purpose to make up for the inconvenience of this type of test.
Research is currently underway to determine if larger-sized samples from field-compacted
soils can give more reliable results than the usual 75-mm (3 in.) diameter samples. Until further
data are developed, the following recommendations are made concerning the approach to utilizing
laboratory hydraulic conductivity tests for QA on field-compacted soils:
. 1. For gravely soils or other soils that cannot be consistently sampled without causing
significant disturbance, laboratory hydraulic conductivity tests should not be a part
of the QA program because representative samples cannot realistically be obtained.
A test pad (Section 2.10) is recommended to verify hydraulic conductivity.
2. If a test pad is constructed and it is demonstrated that the field-scale hydraulic
conductivity is satisfactory on the test pad, the QA program for the actual soil liner
should focus on establishing that the actual liner is built of similar materials and to
equal or better standards compared to the test pad — laboratory hydraulic
conductivity testing is not necessary to establish this.
3. If no test pad is constructed and it is believed that representative samples can be
obtained for hydraulic conductivity testing, then laboratory hydraulic conductivity
tests on undisturbed samples from the field are recommended.
2.8.4.1 Sampling for Hydraulic Conductivity Testing
A thin-walled tube is pushed into the soil to obtain a sample. Samples of soil should be
taken in the manner that minimizes disturbance such as described in ASTM D-1587. Samples
should be sealed and carefully stored to prevent drying and transported to the laboratory in a
manner that minimizes soil disturbance as described in ASTM D-4220.
It is particularly important that the thin-walled sampling tube be pushed into the soil in the
direction perpendicular to the plane of compaction. Many CQA inspectors will push the sampling
83
-------
tube into the soil using the blade of a dozer or compactor. This practice is not recommended
because the sampling tube tends to rotate when it is pushed into the soil. The recommended way of
sampling the soil is to push the sampling tube straight into the soil using a jack to effect a smooth,
straight push.
Sampling of gravely soils for hydraulic conductivity testing is often a futile exercise. The
gravel particles that are encountered by the sampling tube tend to tumble and shear during the push,
which caused major disturbance of the soil sample. Experience has been that QA/QC personnel
may take several samples of gravely soil before a sample that is sufficiently free of gravel to enable
proper sampling is finally obtained; in these cases, the badly disturbed, gravely samples are
discarded. Clearly, the process of discarding samples because they contain too much gravel to
enable proper sampling introduces a bias into the process. Gravely soils are not amenable to
undisturbed sampling.
2.8.4.2 Hydraulic Conductivity Testing
Hydraulic conductivity tests are performed utilizing a flexible wall permeameter and the
procedures described in ASTM D-5084. Inspectors should be careful to make sure that the
effective confining stress utilized in the hydraulic conductivity test is not excessive. Application of
excessive confining stress can produce an artificially low hydraulic conductivity. The CQA plan
should prescribe the maximum effective confining stress that will be used; if none is specified a
value of 35 kPa (5 psi) is recommended for both liner and cover systems.
2.8.4.3 Frequency of Testing
Hydraulic conductivity tests are typically performed at a frequency of 3 tests/ha/lift (1
test/acre/lift) or, for very thick liners (> 1.2 m or 4 ft) per every other lift. This is the
recommended frequency of testing, if hydraulic conductivity testing is required. The CQA plan
should stipulate the frequency of testing.
2.8.4.4 Outliers
The results of the above-described hydraulic conductivity tests are often given far too much
weight. A passing rate of 100% does not necessarily prove that the liner was well built, yet some
inexperienced individuals falsely believe this to be the case. Hydraulic conductivity tests are
performed on small samples; even though small samples may have low hydraulic conductivity,
inadequate construction or CQA can leave remnant macro-scale defects such as fissures and
pockets of poorly compacted soil. The fundamental problem is that laboratory hydraulic
conductivity tests are usually performed on 75-mm (3 in.) diameter samples, and these samples are
too small to contain a representative distribution of macro-scale defects (if any such defects are
present). By the same token, an occasional failing test does not necessarily prove that a problem
exists. An occasional failing test only shows that either: (1) there are occasional zones that fail to
meet performance criteria, or (2) sampling disturbance (e.g., from the sampling tube shearing
stones in the soil) makes confirmation of low hydraulic conductivity difficult or impossible. Soil
liners built of multiple lifts are expected to have occasional, isolated imperfections - this is why the
liners are constructed from multiple lifts. Thus, occasional failing hydraulic conductivity tests by
themselves do not mean very much. Even on the best built liners, occasional failing test results
should be anticipated.
It is recommended that a multiple-lift soil liner be considered acceptable even if a small
percentage (approximately 5%) of the hydraulic conductivity tests fail. However, one should
allow a small percentage of hydraulic conductivity failures only if the overall CQA program is
84
-------
thorough. Further, it is recommended that failing samples have a hydraulic conductivity that is no
greater than one-half to one order of magnitude above the target maximum value. If the hydraulic
conductivity at a particular point is more than one-half to one order of magnitude too high, the zone
should be retested or repaired regardless of how isolated it is.
2.8.5 Repair of Holes from Sampling and Testing
A number of tests, e.g., from nuclear density tests and sampling for hydraulic
conductivity, require that a penetration be made into a lift of compacted soil. It is extremely
important that all penetrations be repaired. The recommended procedure for repair is as follows.
The backfill material should first be selected. Backfill may consist of the soil liner material itself,
granular or pelletized bentonite, or a mixture of bentpnite and soil liner material. The backfill
material should be placed in the hole requiring repair with a loose lift thickness not exceeding about
50 mm (2 in.). The loose lift of soil should be tamped several times with a steel rod or other
suitable device that compacts the backfill and ensures no bridging of material that would leave large
air pockets. Next, a new lift of backfill should be placed and compacted. The process is repeated
until the hole has been filled.
Because it is critical that holes be properly repaired, it is recommended that periodic
inspections and written records made of the repair of holes. It is suggested that approximately
20% of all the repairs be inspected and that the backfill procedures be documented for these
inspections. It is recommended that the inspector of repair of holes not be the same person who
backfilled the hole.
2.8.6 Final Lift Thickness
Construction documents may place restrictions on the maximum allowable final (after-
compaction) lift thickness. Typically, the maximum thickness is 150 mm (6 in.). Final elevation
surveys should be used to establish thicknesses of completed earthwork segments. The specified
maximum lift thickness is a nominal value. The actual value may be determined by surveys on the
surface of each completed lift, but an acceptable practice (provided there is good CQA on loose lift
thickness) is to survey the liner after construction and calculate the average thickness of each lift by
dividing the total thickness by the number of lifts.
Tolerances should be specified on final lift thickness. Occasional outliers from these
tolerances are not detrimental to the performance of a multi-lift liner. It is recommended by
analogy to Table 2.9 that no more than 5% of the final lift thickness determinations be out of
specification and that no out-of-specification thickness be more than 25 mm (1 in.) more than the
maximum allowable lift thickness.
2.8.7 Pass/Fail Decision
After all CQA tests have been performed, a pass/fail decision must be made. Procedures
for dealing with materials problems were discussed in Section 2.7.2.4. Procedures for correcting
deficiencies in compaction of the soil were addressed in Section 2.8.3.5. A final pass/fail decision
is made by the CQA engineer based upon all the data and test results. The hydraulic conductivity
test results may not be available for several days after construction of a lift has been completed.
Sometimes the contractor proceeds at risk with placement of additional lifts before all test results
are available. On occasion, construction of a liner proceeds without final results from a test pad on
the assumption that results will be acceptable. If a "fail" decision is made at this late stage, the
defective soil plus any overlying materials that have been placed should be removed and replaced.
85
-------
2.9 Protection of Compacted Soil
2.9.1 Desiccation
2.9.1.1 Preventive Measures
There are several ways to prevent compacted soil liner materials from desiccating. The soil
may be smooth rolled with a steel drummed roller to produce a thin, dense skin of soil on the
surface. This thin skin of very dense soil helps to minimize transfer of water into or out of the
underlying material. However, the smooth-rolled surface should be scarified prior to placement of
a new lift of soil.
A far better preventive measure is to water the soil periodically. Care must be taken to
deliver water uniformly to the soil and not to create zones of excessively wet soil. Adding water
by hand is not recommended because water is not delivered uniformly to the soil.
An alternative preventive measure is to cover the soil temporarily with a geomembrane,
moist geotextile, or moist soil. The geomembrane or geotextile should be weighted down with
sand bags or other materials to prevent transfer of air between the geosynthetic cover and soil. If a
geomembrane is used, care should be taken to ensure that the underlying soil does not become
heated and desiccate; a light-colored geomembrane may be needed to prevent overheating. If moist
soil is placed over the soil liner, the moist soil is removed using grading equipment.
2.9.1.2 Observations
Visual observation is the best way to ensure that appropriate preventive measures have been
taken to minimize desiccation. Inspectors should realize that soil liner materials can dry out very
quickly (sometimes in a matter of just a few hours). Inspectors should be aware that drying may
occur over weekends and provisions should be made to provide appropriate observations.
2.9.1.3 Tests
If there are questions about degree of desiccation, tests should be performed to determine
the water content of the soil. A decrease in water content of one to two percentage points is not
considered particularly serious and is within the general accuracy of testing. However, larger
reductions in water content provide clear evidence that desiccation has taken place.
2.9.1.4 Corrective Action
If soil has been desiccated to a depth less than or equal to the thickness of a single lift, the
desiccated lift may be disked, moistened, and recompacted. However, disking may produce large,
hard clods of clay that will require pulverization. Also, it should be recognized that if the soil is
wetted, time must be allowed for water to be absorbed into the clods of clay and hydration to take
place uniformly. For this reason it may be necessary to remove the desiccated soil from the
construction area, to process the lift in a separate processing area, and to replace the soil
accordingly.
2.9.2 Freezing Temperatures
2.9.2.1 Compacting Frozen Soil
Frozen soil should never be used to construct soil liners. Frozen soils form hard pieces
86
-------
that cannot be properly remolded and compacted. Inspectors should be on the lookout for frozen
chunks of soil when construction takes place in freezing temperatures.
2.9.2.2 Protection After Freezing
Freezing of soil liner materials can produce significant increases in hydraulic conductivity.
Soil liners must be protected from freezing before and after construction. If superficial freezing
takes place on the surface of a lift of soil, the surface may be scarified and recompacted. If an
entire lift has been frozen, the entire lift should be disked, pulverized, and recompacted. If the soil
is frozen to a depth greater than one lift, it may be necessary to strip away and replace the frozen
material.
2.9.2.3 Investigating Possible Frost Damage
Inspectors usually cannot determine from an examination of the surface the depth to which
freezing took place in a completed or partially completed soil liner that has been exposed to
freezing. In such cases it may be necessary to investigate the soil liner material for possible frost
damage. The extent of damage is difficult to determine. Freezing temperatures cause the
development of tiny microcracks in the soil. Soils that have been damaged due to frost action
develop fine cracks that lead to the formation of chunks of soil when the soil is excavated. The
pushing of a sampling tube into the soil will probably close these cracks and mask the damaging
effects of frost upon hydraulic conductivity. The recommended procedure for evaluating possible
frost damage to soil liners involves three steps:
1... Measure the water content of the soil within and beneath the zone of suspected frost
damage. Density may also be measured, but freeze/thaw has little effect on density
and may actually cause an increase in dry unit weight. Freeze/thaw is often
accompanied by desiccation; water content measurements will help to determine
whether drying has taken place.
2. Investigate the morphology of the soil by digging into the soil and examining its
condition. Soil damaged by freezing usually contains hairline cracks, and the soil
breaks apart in chunks along larger cracks caused by freeze/thaw. Soil that has not
been frozen should not have tiny cracks nor should it break apart in small chunks.
The morphology of the soil should be examined by excavating a small pit into the
soil liner and peeling off sections from the wall of the pit. One should not attempt
to cut pieces from the sidewall; smeared soil will mask cracks. A distinct depth
may be obvious; above this depth the soil breaks into chunks along frost-induced
cracks, and below this depth there is no evidence of cracks produced by freezing.
3. One or more samples of soil should be carefully hand trimmed for hydraulic
conductivity testing. The soil is usually trimmed with the aid of a sharpened section
of tube of the appropriate inside diameter. The tube is set on the soil surface with
the sharpened end facing downward, soil is trimmed away near the sharpened edge
of the trimming ring, the tube is pushed a few millimeters into the soil, and the
trimming is repeated. Samples may be taken at several depths to delineate the depth
to which freeze/thaw damage occurred. The minimum diameter of a cylindrical test
specimen should be 300 mm (12 in.). Small test specimens, e.g., 75 mm (3 in.)
diameter specimens, should not be used because freeze/thaw can create
morphological structure in the soil on a scale too large to permit representative
testing with small samples. Hydraulic conductivity tests should be performed as
described in ASTM D-5084. The effective confining stress should not exceed the
87
-------
smallest vertical effective stress to which the soil will be subjected in the field,
which is usually the stress at the beginning of service for liners. If no compressive
stress is specified, a value of 35 kPa (5 psi) is recommended for both liner and
cover system.
The test pit and all other penetrations should be carefully backfilled by placing soil in lifts
and compacting the lifts. The sides of the test pit should be sloped so that the compactor can
penetrate through to newly placed material without interference from the walls of the pit.
2.9.2.4 Repair
If it is determined that soil has been damaged by freezing, the damaged material is usually
repaired as follows. If damage is restricted to a single lift, the lift may be disked, processed to
adjust water content or to reduce clod size if necessary, and recompacted. If the damage extends
deeper, damaged materials should be excavated and replaced.
2.9.3 Excess Surface Water
In some cases exposed lifts of liner material, or the completed liner, are subjected to heavy
rains that soften the soil. Surface water creates a problem if the surface is uneven (e.g., if a footed
roller has been used and the surface has not been smooth-rolled with a smooth, steel wheeled
roller) — numerous small puddles of water will develop in the depressions low areas. Puddles of
water should be removed before further lifts of material, or other components of the liner or cover
system, are constructed. The material should be disked repeatedly to allow the soil to dry, and
when the soil is at the proper water content, the soil should be compacted. Alternatively, the wet
soil may be removed and replaced.
Even if puddles have not formed, the soils may be too soft to permit construction
equipment to operate on the soil without creating ruts. To deal with this problem, the soil may be
allowed to dry slightly by natural processes (but care must be taken to ensure that it does not dry
too much and does not crack excessively during the drying process). Alternatively, the soil may be
disked, allowed to dry while it is periodically disked, and then compacted.
If soil is reworked and recompacted, QA/QC tests should be performed at the same
frequency as for the rest of the project. However, if the area requiring reworking is very small,
e.g., in a sump, tests should be performed in the confined area to confirm proper compaction even
if this requires sampling at a greater frequency.
2.10 Test Pads
2.10.1 Purpose of Test Pads
The purpose of a test pad is to verify that the materials and methods of construction
proposed for a project will lead to a soil liner with the required large-scale, in-situ, hydraulic
conductivity. Unfortunately, it is impractical to perform large-scale hydraulic conductivity tests on
the actual soil liner for two reasons: (1) the testing would produce significant physical damage to
the liner, and the repair of the damage would be questionable; and (2) die time required to complete
the testing would be too long — the liner could become damaged due to desiccation while one
waited for the test results.
A test pad may also be used to demonstrate that unusual materials or construction
procedures will work. The process of constructing and testing a test pad is usually a good learning
88
-------
experience for the contractor and CQC/CQA personnel; overall quality of a project is usually
elevated as a result of building and testing the test pad.
A test pad is constructed with the soil liner materials proposed for a project utilizing
preprocessing procedures, construction equipment, and construction practices that are proposed for
the actual liner. If the required hydraulic conductivity is demonstrated for the test pad, it is
assumed that the actual liner will have a similar hydraulic conductivity, provided the actual liner is
built of similar materials and to standards that equal or exceed those used in building the test pad.
If a test pad is constructed and hydraulic conductivity is verified on the test pad, a key goal of
CQA/CQC for the actual liner is to verify that the actual liner is built of similar materials and to
standards that equal or exceed those used in building the test pad.
2.10.2 Dimensions
Test pads (Fig. 2.31) normally measure about 10 to 15 m in width by 15 to 30 m in length.
The width of the test pad is typically at least four times the width of the compaction equipment, and
the length must be adequate for the compactor to reach normal operating speed in the test area. The
thickness of a test pad is usually no less than the thickness of the soil liner proposed for a facility
but may be as little as 0.6 to 0.9 m (2 to 3 feet) if thicker liners are to be employed at full scale. A
freely draining material such as sand is often placed beneath the test pad to provide a known
boundary condition in case infiltrating water from a surface hydraulic conductivity test (e.g., sealed
double ring infiltrometer) reaches the base of the liner. The drainage layer may be drained with a
pipe or other means. However, infiltrating water will not reach the drainage layer if the hydraulic
conductivity is very low; the drainage pipe would only convey water if the hydraulic conductivity
turns out to be very large. The sand drainage material may not provide adequate foundation
support for the first lift of soil liner unless the sand is compacted sufficiently. Also, the first lift of
soil liner material on the drainage layer is often viewed as a sacrificial lift and is only compacted
nominally to avoid mixing clayey soil in with the drainage material.
2.10.3 Materials
The test pad is constructed of the same materials that are proposed for the actual project.
Processing equipment and procedures should be identical, too. The same types of CQC/CQA tests
that will be used for the soil liner are performed on the test pad materials. If more than one type of
material will be used, one test pad should be constructed for each type of material.
2.10.4 Construction
It is recommended that test strips be built before constructing the test pad. Test strips allow
for the detection of obvious problems and provide an opportunity to fine-tune soil specifications,
equipment selection, and procedures so that problems are minimized and the probability of the
required hydraulic conductivity being achieved in the test pad is maximized. Test strips are
typically two lifts thick, one and a half to two equipment widths wide, and about 10 m (30 ft) long.
The test pad is built using the same loose lift thickness, type of compactor, weight of
compactor, operating speed, and minimum number of passes that are proposed for the actual soil
liner. It is important that the test pad not be built to standards that will exceed those used in
building the actual liner. For example, if the test pad is subjected to 15 passes of the compactor,
one would want the actual soil liner to be subjected to at least 15 passes as well. It is critical that
CQA personnel document the construction practices that are employed in building the test pad. It is
best if the same contractor builds the test pad and actual liner so that experience gained from the test
pad process is not lost. The same applies to CQC and CQA personnel.
89
-------
Plan View
Compactor
Cross Section
"Drainage Material
W = 3 Compaction Vehicle Widths, Minimum
L = A Value No Smaller than W and Sufficient for Equipment
to Reach Proper Operating Speed in Test Area
Figure 2.31 - Schematic Diagram of Soil Liner Test Pad
2.10.5 Protection
The test pad must be protected from desiccation, freezing, and erosion in the area where in
situ hydraulic conductivity testing is planned. The recommended procedure is to cover the test pad
with a sheet of white or clear plastic and then either spread a thin layer of soil on the plastic if no
rain is anticipated or, if rain may create an undesirably muddy surface, cover the plastic with hay or
straw.
90
-------
2.10.6 Tests and Observations
The same types of CQA tests that are planned for the actual liner are usually performed on
the test pad. However, the frequency of testing is usually somewhat greater for the test pad.
Material tests such as liquid limit, plastic limit, and percent fines are often performed at the rate of
one per lift. Several water content-density tests are usually performed per lift on the compacted
soil. A typical rate of testing would be "one water content-density test for each 40 m2 (400 ft2).
The CQA plan should describe the testing frequency for the test pad.
There is a danger in over testing the test pad — excessive testing could lead to a greater
degree of construction control in the test pad than in the actual liner. The purpose of the test pad is
to verify that the materials and methods of construction proposed for a project can result in
compliance with performance objectives concerning hydraulic conductivity. Too much control
over the construction of the test pad runs counter to this objective.
2.10.7 In Situ Hydraulic Conductivity
2.10.7.1 Sealed Double-Ring Infiltrometer
The most common method of measuring in situ hydraulic conductivity on test pads is the
sealed double-ring infiltrometer (SDRI). A schematic diagram of the SDRI is shown Fig. 2.32.
The test procedure is described in ASTM D-5093.
Tensiometer
Inner Ring
Tubing
Grout
Flexible Bag
Outer Ring
:;Test~PacE
I'Drafnaget^erj
Figure 2.32 - Schematic Diagram of Sealed Double Ring Infiltrometer (SDRI)
With this method, the quantity of water that flows into the test pad over a known period of
time is measured. This flow rate, which is called the infiltration rate (I), is computed as follows:
= Q/At
(2.5)
91
-------
where Q is the quantity of water entering the surface of the soil through a cross-sectional area A
and over a period of time t.
Hydraulic conductivity (K) is computed from the infiltration rate and hydraulic gradient (i)
as follows:
K = Ifi (2.6)
Three procedures have been used to compute the hydraulic gradient. The procedures are
called (1) apparent gradient method; (2) wetting front method; and (3) suction head method. The
equation for computing hydraulic gradient from each method is shown in Fig. 2.33.
Apparent Hydraulic Conductivity Method
H+D
Suction Head Method
H + D
Wetting Front Method
i= H + p
D
Figure 2.33 - Three Procedures for Computing Hydraulic Gradient from Infiltration Test
92
-------
The apparent gradient method is the most conservative of the three methods because this
method yields the lowest estimate of i and, therefore, the highest estimate of hydraulic
conductivity. The apparent gradient method assumes that the test pad is fully soaked with water
over the entire depth of the test pad. For relatively permeable test pads, the assumption of full
soaking is reasonable, but for soil liners with K < 1 x 10'7 cm/s, the assumption of full soaking is
excessively conservative and should not be used unless verified.
The second and most widely used method is the wetting front method. The wetting front is
assumed to partly penetrate the test pad (Fig. 2.33) and the water pressure at the wetting front is
conservatively assumed to equal atmospheric pressure. Tensiometers are used to monitor the depth
of wetting of the soil over time, and the variation of water content with depth is determined at the
end of the test. The wetting front method is conservative but in most cases not excessively so.
The wetting front method is the method that is usually recommended.
The third method, called the suction head method, is the same as the wetting front method
except that the water pressure at the wetting front is not assumed to be atmospheric pressure. The
suction head (which is defined as the negative of the, pressure head) at the wetting front is Hs and is
added to the static head of water in the infiltration ring to calculate hydraulic gradient (Fig. 2.37).
The suction head Hs is identical to the wetting front suction head.employed in analyzing water
infiltration with the Green-Ampt theory. The suction head Hs is not the ambient suction head in the
unsaturated soil and is generally very difficult to determine (Brakensiek, 1977). Two techniques
available for determining Hs are:
1. Integration of the hydraulic conductivity function (Neuman, 1976):
(2.7)
where hsc is the suction head at the initial (presoaked) water content of the soil, Kr
is the relative hydraulic conductivity (K at particular suction divided by the value of
K at full saturation), and hs is suction.
2. Direct measurement with air entry permeameter (Daniel, 1989, and references
therein).
Reimbold (1988) found that Hs was close to zero for two compacted soil liner materials. Because
proper determination of Hs is very difficult, the suction head method cannot be recommended,
unless the testing personnel take the time and make the effort to determine Hs properly and reliably.
Corrections may be made to account for various factors. For example, if the soil swells,
some of the water that infiltrated into the soil was absorbed into the expanded soil. No consensus
exists on various corrections and these should be evaluated case by case.
2.10.7.2 Two-Stage Borehole Test
The two-stage borehole hydraulic conductivity was developed by Boutwell (the test is
sometimes called the Boutwell Test) and was under development as an ASTM standard at the time
of this writing. The device is installed by drilling a hole (which is typically 100 to 150 mm in
diameter), placing a casing in the hole, and sealing the annular space between the casing and
borehole with grout as shown in Fig. 2.34. A series of falling head tests is performed and the
93
-------
hydraulic conductivity from this first stage (ki) is computed. Stage one is complete when ki
ceases to change significantly. The maximum vertical hydraulic conductivity may be computed by
assuming that the vertical hydraulic conductivity is equal to ki. However, the test may be
continued for a second stage by removing the top of the casing and extending the hole below the
casing as shown in Fig. 2.34. The casing is reassembled, the device is again filled with water, and
falling head tests are performed to determine the hydraulic conductivity from stage two fe). Both
horizontal and vertical hydraulic conductivity may be computed from the values of ki and k2
Further details on methods of calculation are provided by Boutwell and Tsai (1992), although the
reader is advised to refer to the ASTM standard when it becomes available
A. Stane I
B. Stage II
Standpipe
Casing
Grout
Figure 2.34 - Schematic Diagram of Two-Stage Borehole Test
The two-stage borehole test permeates a smaller volume of soil than the sealed double-ring
infiltrometer. The required number of two-stage borehole tests for a test pad is a subject of current
research. At the present time, it is recommended that at least 5 two-stage borehole tests be
performed on a test pad if the two-stage test is used. If 5 two-stage borehole tests are performed
then one would expect that all five of the measured vertical hydraulic conductivities would be less
than or equal to the required maximum hydraulic conductivity for the soil liner.
94
-------
2.10.7.3 Other Field Tests
Several other methods of in situ hydraulic conductivity testing are available for soil liners.
These methods include open infiltrometers, borehole tests with a constant water level in the
borehole, porous probes, and air-entry permeameters. The methods are described by Daniel
(1989) but are much less commonly used than the SDRI and two-stage borehole test.
t l- *\L'
2.10.7.4 Laboratory Tests
Laboratory hydraulic conductivity tests may be performed for two reasons:
1. If a very large sample of soil is taken from the field and permeated in the laboratory, the
result may be representative of field-scale hydraulic conductivity. The question of how
large the laboratory test specimen needs to be is currently a matter of research, but
preliminary results indicate that a specimen with a diameter of approximately 300 mm (12
in.) may be sufficiently large (Benson et al., 1993).
2. If laboratory hydraulic conductivity tests are a required component of QA/QC for the
actual liner, the same sampling and testing procedures are used for the test pad.
Normally, undisturbed soil samples are obtained following the procedures outlined in
ASTM D-1587, and soil test specimens with diameters of approximately 75 mm (3 in.)
are permeated in flexible-wall permeameters in accordance with ASTM D-5084.
2.10.8 Documentation
A report should be prepared that describes all of the test results from the test pad. The test
pad documentation provides a basis for comparison between test pad results and the CQA data
developed on an actual construction project.
2.11 Final Approval
Upon completion of the soil liner, the soil liner should be accepted and approved by the
CQA engineer prior to deployment or construction of the next overlying layer.
2.12 References
Albrecht, K .A., and K. Cartwright (1989), "Infiltration and Hydraulic Conductivity of a
Compacted Earthen Liner," Ground Water, Vol. 27, No. 1, pp. 14-19.
Alther, G. R. (1983), "The Methylene Blue Test for Bentonite Liner Quality Control,"
Geotechnical Testing Journal, Vol. 6, No. 3, pp. 133-143.
ASTM D-422, "Particle-Size Analysis of Soils"
ASTM D-698, "Laboratory Compaction Characteristics of Soils Using Modified Effort (12,400 ft-
lbf/ft3(600kN-m/m3))"
ASTM D-1140, "Amount of Material in Soils Finer than the No. 200 (75-|im)Sieve"
95
-------
ASTM D-1556, "Density and Unit Weight of Soil In Place by Sand-Cone Method"
ASTM D-1557, "Laboratory Compaction Characteristics of Soils Using Standard Effort (56 000
ft-lbf/ft3 (2,700 kN-nVm3))"
ASTM D-1587, "Thin-Walled Tube Sampling of Soils"
ASTM D-2167, "Density and Unit Weight of Soil In Place by Rubber Balloon Method"
ASTM D-2216, "Laboratory Determination of Water (Moisture) Content of Soil and Rock"
ASTM D-2487, "Classification of Soils for Engineering Purposes (Unified Soil Classification
System)"
ASTM D-2488, "Description and Identification of Soils (Visual-Manual Procedure)"
ASTM D-2922, "Density of Soil and Soil-Aggregate In Place by Nuclear Methods (Shallow
Depth)
ASTM D-2937, "Density and Unit Weight of Soil In Place by Drive-Cylinder Method"
ASTM D-3017, "Water Content of Soil and Rock In Place by Nuclear Methods (Shallow Depth)"
ASTM D-4220, "Preserving and Transporting Soil Samples"
ASTM D-4318, "Liquid Limit, Plastic Limit, and Plasticity Index of Soils"
ASTM D-4643, "Determination of Water (Moisture) Content of Soil by Microwave Oven Method"
ASTM D-4944, "Field Determination of Water (Moisture) Content of Soil by Calcium Carbide Gas
Pressure Tester Method"
ASTM D-4959, "Determination of Water (Moisture) Content of Soil by Direct Heating Method"
ASTM D-5080, "Rapid Determination of Percent Compaction"
ASTM D-5084, "Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a
Flexible Wall Permeameter"
ASTM D-5093, "Field Measurement of Infiltration Rate Using a Double-Ring Infiltrometer with a
Sealed Inner Ring"
ASTM E-946, "Water Adsorption of Bentonite by the Porous Plate Method"
Benson, C. H., and D.E. Daniel (1990), "Influence of Clods on Hydraulic Conductivity of
Compacted Clay," Journal of Geotechnical Engineering, Vol. 116, No. 8, pp. 1231-1248.
Benson, C. H., and G. P. Boutwell (1992), "Compaction Control and Scale-Dependent Hydraulic
Conductivity of Clay Liners," Proceedings, Fifteenth Annual Madison Waste Conference
Umv. of Wisconsin, Madison, Wisconsin, pp. 62-83..
Benson, C. H., Zhai, H., and Rashad, S. M. (1992), "Assessment of Construction Quality
96
-------
Control Measurements and Sampling Frequencies for Compacted Soil Liners," Environmental
Geotechnics Report No. 92-6, University of Wisconsin, Department of Civil and
Environmental Engineering, Madison, Wisconsin, lOOp.
Benson, C. H., Hardianto, F. S., and Motan, E. S. (1993), "Representative Sample Size for
Hydraulic Conductivity Assessment of Compacted Soil Liners," Hydraulic Conductivity and
Waste Contaminant Transport in Soils, ASTM STP 1142, D. E. Daniel and S. J. Trautwein
(Eds.), American Society for Testing and Materials, Philadelphia, (in review).
Boutwell, G., and Hedges, C. (1989), "Evaluation of Waste-Retention Liners by Multivariate
Statistics," Proceedings of the Twelfth International Conference on Soil Mechanics and
Foundation Engineering, A. A. Balkema, Rotterdam, Vol. 2, pp. 815-818.1
Boutwell, G .P., and Tsai, C. N. (1992), "The Two-Stage Field Permeability Test for Clay
Liners," Geotechnical News, Vol. 10, No. 2, pp. 32-34.
Brakensiek, D.L. (1977), "Estimating the Effective Capillary Pressure in the Green and Ampt
Infiltration Equation," Water Resources Research, Vol. 12, No. 3, pp. 680-681.
Brown, R. K. (1992), Personal Communication.
Daniel, D.E. (1989), "In Situ Hydraulic Conductivity Tests for Compacted Clay," Journal of
Geotechnical Engineering, Vol. 115, No. 9, pp. 1205-1226.
Daniel, D.E. (1990), "Summary Review of Construction Quality Control for Compacted Soil
Liners," in Waste Containment Systems: Construction, Regulation, and Performance, R.
Bonaparte (Ed.), American Society of Civil Engineers, New York, pp. 175-189.
Daniel, D.E., and C. H. Benson (1990), "Water Content - Density Criteria for Compacted Soil
Liners," Journal of Geotechnical Engineering, Vol. 116, No. 12, pp. 1811-1830.
Elsbury, B. R., Daniel, D. E., Sraders, G. A., and Anderson, D. C. (1990), "Lessons Learned
from Compacted Clay Liner," Journal of Geotechnical Engineering, Vol. 116, No. 11, pp.
1641-1660.
Hilf, J. W. (1991), "Compacted Fill," in Foundation Engineering Handbook^ H. Y. Fang (Ed.),
Van Nostrand Reinhold, New York, pp. 249-316.
Lambe, T. W., and Whitman, R. V. (1969), Soil Mechanics, John Wiley & Sons, New York, 533
P-
Mitchell, J. K., Hooper, D. R., and Campanella, R. G. (1965), "Permeability of Compacted
Clay," lournal of the Soil Mechanics and Foundations Division, ASCE, Vol. 91, No. SM4,
pp. 41-65.
Mundell, J. A., and Bailey, B. (1985), "The Design and Testing of a Compacted Clay Barrier
Layer to Limit Percolation through Landfill Covers," Hydraulic Barriers in Soil and Rock,
ASTM STP 874, A. I. Johnson et al. (Eds.), American Society for Testing and Materials,
Philadelphia, pp. 246-262.
Neuman, S.P. (1976), "Wetting Front Pressure Head in the Infiltration Model of Green and
Ampt," Water Resources Research, Vol. 11, No. 3, pp. 564-565.
97
-------
Noorany, I. (1990), "Variability in Compaction Control," Journal of Geotechnical Engineering,
Vol. 116, No. 7, pp. 1132-1136. s
Reimbold, M.W. (1988), "An Evaluation of Models for Predicting Infiltration Rates in
Unsaturated Compacted Clay Soils," M.S. Thesis, The University of Texas at Austin, Austin,
Texas, 128 p.
if.,,
v
Richardson, G. N. (1992), "Construction Quality Management for Remedial Action and Remedial
Design Waste Containment Systems," U.S. Environmental Protection Agency, EPA/540/R-
92/073, Washington, DC.
Schmertmann, J.H. (1989), "Density Tests Above Zero Air Voids Line," Journal of Geotechnical
Engineering, Vol. 115, No. 7, pp. 1003-1018.
Shelley, T. L., and Daniel, D. E. (1993), "Effect of Gravel on Hydraulic Conductivity of
Compacted Soil Liners," Journal of Geotechnical Engineering, Vol. 119, No. 1, pp. 54-68.
Turnbull, W. J., Compton, J. P., and R. G. Ahlvin (1966), "Quality Control of Compacted
Earthwork,' Journal of the Soil Mechanics and Foundations Division^ ASCE, Vol. 92, No.
SMI, pp. 93-103.
U.S. Army Corps of Engineers (1970), "Laboratory Soils Testing," Office of the Chief of
Engineers, Washington, DC, EMI 110-2-1906.
98
-------
Chapter 3
Geomembranes
This chapter focuses upon the manufacturing quality assurance (MQA) aspects of
geomembrane formulation, manufacture and fabrication, and on the construction quality assurance
(CQA) of the complete installation of the geomembranes in the field. Note that in previous
literature these liner materials were catted flexible membrane liners (FML's), but the more generic
name of geomembranes will be used throughout this document.
The geomembrane materials discussed in this document are those used most often at the
time of writing. However, there are other polymer types that are also used. Aspects of quality
assurance of these materials can be inferred from information contained in this document. In the
future, new materials will be developed and the reader is advised to seek the appropriate
information for evaluation of such new or modified materials.
3.1 Types of Geomembranes and Their Formulations
It must be recognized that all geomembranes are actually formulations of a parent resin
(from which they derive their generic name) and several other ingredients. The most commonly
used geomembranes for solid and liquid waste containment are listed below. They are listed
according to their commonly referenced acronyms which will be explained in the text to follow.
Other geomembranes in limited use or under initial field trials will also be mentioned where
appropriate but will be covered in less detail than the types listed below.
Table 3.1 - Types of Commonly Used Geomembranes and Their Approximate Weight Percentage
Formulations*
Geomembrane
Type
HOPE
VLDPE
Other Extruded Types **
PVC
CSPE***
Other Calendered Types**
Resin
95-98
94-96
95-98
50-70
40-60
40-97
Plasticizer
0
0
0
25-35
0
0-30
Filler
0
0
0
0-10
40-50
0-50
Carbon Black
or Pigment
2-3
2-3
2-3
2-5
5-40
2-30
Additives
0.25-1.0
1-4
1-2
2-5
5-15
0-7
* Note that this Table should not be directly used for MQA or CQA Documents, since neither the Agency nor
the Authors of the Report intend to provide prescriptive formulations for manufacturers and their respective
geomembranes.
** Other geomembranes than those listed in this Table will be described in the appropriate Section.
*** CSPE geomembranes are generally fabric (scrim) reinforced.
99
-------
It must be recognized that Table 3.1 and the references to it in the text to follow are meant to
reflect on the cjirrent state-of-the-art. The values mentioned are not meant to be prescriptive and
future research and development may result in substantial changes.
3.1.1 High Density Polyethylene (HDPE1
As noted in Table 3.1, high density polyethylene (HOPE) geomembranes are made from
polyethylene resin, carbon black and additives.
3.1.1.1 Resin
The polyethylene resin used for HOPE geomembranes is prepared by low pressure
|nzatlon of ethylene as t"6 principal monomer and having the characteristics listed in ASTM
8. As seen in Fig. 3.1, the resin is usually supplied to the manufacturer or formulator in an
opaque pellet form.
Polyethylene Pellets
Figure 3.1 - HOPE Resin Pellets
TY^,- the Preparation of a specification or MQA document for the resin component of
an HDPE geomembrane, the following items should be considered:
1. The polyethylene resin, which is covered in ASTM D-1248, is to be made from virgin
uncontaminated ingredients. '
2. The quality control tests performed on the incoming resin will typically be density
(either ASTM D-792 or D1505) and melt flow index which is ASTM D-1238.
100
-------
3 Typical natural densities of the various resins used are between 0.934 and 0.940 g/cc.
Note that according to ASTM D-1248 this is Type II polyethylene and is classified as
medium density polyethylene.
4 Typical melt flow index values are between 0.1 and 1.0 g/10 min as per ASTM D-
1238, Cond. 190/2.16.
5 Other tests which can be considered for quality control of the resin are melt flow ratio
(comparing high-to-low weight melt flow values), notched constant tensile load test as
per ASTM D-5397, and a single point notched constant load test, see Hsuan and
Koerner (1992) for details. The latter tests would require a plaque to be made from the
resin from which test specimens are taken. The single point notched constant load test /
is then performed at 30% yield strength and the test specimens are currently
recommended not to fail within 200 hours.
6. Additional quality control certification procedures by the manufacturer (if any) should
be implemented and followed.
7. The frequency of performing each of the preceding tests should be covered in the
MQC plan and it should be implemented and followed.
8 An HDPE geomembrane formulation should consist of at least 97% of polyethylene
resin. As seen in Table 3.1 the balance is carbon black and additives. No fillers,
extenders, or other materials should be mixed into the formulation.
9 It should be noted that by adding carbon black and additives to the resin, the density of
the final formulation is generally 0.941 to 0.954 g/cc. Since this numeric value is now
in the high density polyethylene category according to ASTM D-1248, geomembranes
of this type are commonly referred to as high density polyethylene (HDPE).
10. Regrind or rework chips (which have been previously processed by the same
manufacturer but never used as a geomembrane, or other) are often added to the
extruder during processing. This topic will be discussed in section 3.2.2.
11 Reclaimed material (which is polymer material that has seen previous service life and is
recycled) should never be allowed in the formulation in any quantity. This topic will
be discussed in section 3.2.2.
3.1.1.2 Carbon Black
Carbon black is added into an HDPE geomembrane formulation for general stabilization
purposes, particularly for ultraviolet light stabilization. It is sometimes added in a powder form at
the geomembrane manufacturing facility during processing, or (generally) it is added as a
preformulated concentrate in pellet form. The latter is the usual case. Figure 3.2 shows
photographs of carbon black powder and of concentrate pellets consisting of approximately 25%
carbon black in a polyethylene resin carrier.
Regarding the preparation of a specification or MQA document for the carbon black
component of HDPE geomembranes, the following items should be considered.
1. The carbon black used in HDPE geomembranes should be a Group 3 category, or
lower, as defined in ASTM D-1765.
101
-------
Carbon Black Powder
Carbon Black Concentrate
Figure 3.2 - C^onBlack in Particulate Form (Upper Photograph) and as a Concentrate (Lower
102
-------
2. Typical amounts of carbon black are from 2.0% to 3.0% by weight per ASTM D-1603.
Values less than 2.0% do not appear to give adequate long-term ultraviolet protection;
values greater than 3.0% begin to adversely effect physical and mechanical properties.
3 Current carbon black dispersion requirements in the final HDPE geomembrane are
usually required to be A-l, A-2 or B-l according to ASTM D-2663. Sample preparation
is via ASTM D-3015. It should be noted, however, that this test method is directed at
polymeric materials containing relatively large amounts of carbon black, e.g., thermoset
elastomers with carbon black contents of approximately 18% by volume. ASTM D-35
Committee on Geosynthetics has a Task Group formulating a new standard focused at
carbon black dispersion for formulations containing less than 5% carbon black. Thus
this standard will be applicable for the 2 to 3% carbon black currently used in
polyethylene formulations.
4. In the event that the carbon black is mixed into the formulation in the form of a
concentrate rather than a powder, the carrier resin of the concentrate should be the same
generic type as the base polyethylene resin.
3.1.1.3 Additives
Additives are introduced into an HDPE geomembrane formulation for the purposes of
oxidation prevention, long-term durability and as a lubricant and/or processing aid during
manufacturing. It is quite difficult to write a specification for HDPE geomembranes around a
particular additive, or group of additives, because they are generally proprietary. Furthermore,
there is research and development ongoing in this area and thus additives are subject to change over
time.
If additives are included in a specification or MQA document, the description must be very
general as to the type and amount. However, the amount can probably be bracketed as to an upper
value.
1. The nature of the additive package used in the HDPE compound may be requested of the
manufacturer.
2. The maximum amount of additives in a particular formulation should not exceed 1.0%
by weight.
3.1.2 Very Low Density Polyethylene CVLDPE^)
As seen in Table 3.1, very low density polyethylene (VLDPE) geomembranes are made
from polyethylene resin, carbon black and additives. It should be noted that there are similarities
between VLDPE and certain types of linear low density polyethylene (LLDPE). The linear
structure and lack of long-chain branching in both LLDPE and VLDPE arise from their similar
polymerization mechanisms although the catalyst technology is different. In the low-pressure
polymerization of LLDPE, the random incorporation of alpha olefin comonomers produces
sufficient short-chain branching to yield densities in the range of 0.915 to 0.930 g/cc. The even
lower densities of VLDPE resins (from 0.890 to 0.912 g/cc) are achieved by adding more
comonomer (which produces more short-chain branching than occurs in LLDPE, and thus a lower
level of crystallinity) and using proprietary catalysts and reactor technology. Since VLDPE is more
commonly used than LLDPE for geomembranes in waste containment applications, this section is
written around VLDPE. It can be used for LLDPE if the density is at the low end of the above
mentioned range. The situation is under discussion by many groups as of the writing of this
103
-------
document.
3.1.2.1 Resin
The polyethylene resin used for VLDPE geomembranes is a linear polymer of ethylene with
other alpha-olefins. As with HDPE, the resin is generally supplied to the manufacturer in the form
of pellets, recall Fig. 3.1.
Some specification or MQA document items for VLDPE resins follow:
1. The very low density polyethylene resin is to be made from completely virgin materials.
The natural density of the resin is less than 0.912 g/cc, however, a unique category is
not yet designated by ASTM.
2. A VLDPE geomembrane formulation should consist of approximately 94-96% polymer
resin. As seen in Table 3.1, the balance is carbon black and additives.
3. Typical quality control tests for VLDPE resin will be density, via ASTM D-792 or
D1505, and melt flow index via ASTM D-1238.
4. Additional quality control certification procedures of the manufacturer (if any) should be
implemented and followed.
5. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
6. Regrind or rework chips (which have been previously processed by the same
manufacturer but never used as a geomembrane, or other) are often added to the
formulation during processing. This topic will be discussed in section 3.2.2.
7. Reclaimed material (which is polymer that has seen previous service life and is recycled)
should never be allowed in any quantity. This topic will be discussed in section 3.2.2.
3.1.2.2 Carbon Black
Carbon black is added to VLDPE geomembrane formulations for general stabilization
purposes, particularly for ultraviolet light stabilization. It is added either in a powder form at the
geomembrane manufacturing facility, or it is added as a preformulated concentrate in pellet form
recall Fig. 3.2. F
Some items to be included in a specification or MQA document follow:
1. The carbon black used in VLDPE geomembranes should be a Group 3 category or
lower, as defined in ASTM D-1765.
2. Typical amounts of carbon black are from 2.0% to 3.0% by weight as per ASTM D-
1603. Values less than 2.0% do not appear to give adequate long-term ultraviolet
protection, while values greater than 3.0% begin to negatively effect physical and
mechanical properties.
3. Current carbon black dispersion requirements in the final HDPE geomembrane are
usually required to be A-l, A-2 or B-l according to ASTM D-2663(8X Sample
104
-------
preparation is via ASTM D-3015. It should be noted, however, that this test method
was directed at polymeric materials containing relatively large amounts of carbon black,
e.g., thermoset elastomers with carbon black contents of approximately 18% by volume.
ASTM D-35 Committee on Geosynthetics has a Task Group formulating a new standard
focused at carbon black dispersion for formulations containing less than 5% carbon
black which is the amount used in formulation of VLDPE geomembranes.
4. In the event that the carbon black is mixed into the formulation in the form of a
concentrate rather than a powder, the carrier resin of the concentrate should be identified.
3.1.2.3 Additives
Additives are introduced into a VLDPE formulation for the purposes of anti-oxidation,
long-term durability and as a lubricant and/or processing aid during manufacturing. It is quite
difficult to write a specification for VLDPE geomembranes around a particular additive, or group
of additives, because they are generally proprietary. Furthermore, there is research and
development ongoing in this area and thus additives are subject to change over time.
If additives were included in a specification or MQA document, the description must be
very general as to the type and amount. However, the amount can probably be bracketed as to an
upper value.
1. The nature of the additive package used in the VLDPE compound may be requested of
the manufacturer.
2. The maximum amount of additives in a particular formulation should not exceed 2.0%
for smooth sheet or 4.0% for textured sheet by weight.
3.1.3 Other Extruded Geomembranes
Recently, there have been developed other variations of extruded geomembranes. Four
have seen commercialization and will be briefly mentioned.
One variation is a coextruded light colored surface layer onto a black base layer for the
purpose of reduced surface temperatures when the geomembrane is exposed for a long period of
time. The usual application for this material is as a liner for surface impoundments which have no
soil covering or sacrificial sheet covering. In the formulation of the light colored surface layer the
carbon black is replaced by a pigment (often metal oxides, such as titanium dioxide) which acts as
an ultraviolet screening agent. This results in a white, or other light colored surface. The
coextruded surface layer is usually relatively thin, e.g., 5 to 10 percent of the total geomembrane's
thickness.
A second coextrusion variation is HDPE/VLDPE/HDPE sheet where the two surface layers
of HOPE are relatively thin with respect to the VLDPE core. Thickness percentages of 20/60/20
are sometimes used. The interface of these coextruded layers cannot be visually distinguished
since the polymers merge into one another while they are in the molten state, i.e., such
geomembranes are not laminated together after processing, but are coextruded during processing.
A third variation of coextrusion is to add a foaming agent, such as nitrogen gas, into the
surface layer extruder(s). This foaming agent expands and bursts at the surface of the sheet as it
cools. The resulting surface is very rough and is generally referred to as textured. This variation
will be described in Sections 3.2.3.4 and 3.2.4.4 for HOPE and VLDPE, respectively.
105
-------
A fourth variation of extruded geomembranes is a generic polymer group under the
.f S??!1 5>£5Uy crosslinked elastomeric alloys (FCEA). This group of polymers is described
in AbTM D-5046. The particular geomembrane type that has been used in waste containment
applications is a thermoplastic elastomeric alloy of polypropylene (PP) and ethylene-propylene
diene monomer (EPDM). The EPDM is fully crosslinked and suspended in a PP matrix in a
process called dynamic vulcanization. The mixed polymer is extruded in a manner similar to the
geomembrane types discussed in this section.
3.1.4 Polwinvl Chloride CPVO
As seen in Table 3.1, polyvinyl chloride (PVC) geomembranes are made from polyvinyl
chloride resin, plasticizer(s), fillers and additives.
3.1.4.1 Resin
j- ui Tjie-polyvinyl chloride resin used for PVC geomembranes is made by cracking ethylene
dichlonde into a vinyl chloride monomer. It is then polymerized to make PVC resin. The PVC
resm (in the form of a white powder) is then compounded with other components to form a PVC
compound.
™ r~ ^ the Preparation of a specification or MQA document, the following items concerning the
PVC resm should be considered.
1 . The polyvinyl chloride resin should be made from completely virgin materials.
2. A PVC compound will generally consist of 50-70% PVC resin, by weight.
3. Typical quality control tests on the resin powder will be contamination, relative
viscosity, resin gels, color and dry time. The specific test procedures will be specified
by the manufacturer. Often they are other than ASTM tests.
4. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
5. Quality control certification procedures used by the manufacturer should be implemented
and followed.
3.1.4.2 Plasticizer
Plasticizers are added to PVC formulations to impart flexibility, improve handling and
modify physical and mechanical properties. When blended with the PVC resin the plasticizer(s)
must be completely mixed into the resin. Since the resin is a powder, and the plasticizers are
liquid, mixing of the two components continues until the liquid is completely absorbed by the
powder. The result is usually a powder which can be readily conveyed. However, it is also
possible to wet blend with acceptable results. There are two general categories of possible
plasticizers; monomeric plasticizers and polymeric plasticizers. There are many specific types
within each category. For example, monomeric plasticizers are sometimes phthalates, epoxides
and phosphates, while polymeric plasticizers are sometimes polyesters, ethylene copolymers and
mtnle rubber. v J
For a specification or MQA document written around PVC plasticizer(s), the following
items should be considered.
106
-------
1. If more than one type of plasticizer is used in a PVC formulation they must be
compatible with one another.
2. The plasticizer(s) in a PVC compound are generally from 25-35% of the total compound
by weight.
3. The exact type of plasticizer(s) used by the manufacturers are rarely identified. This is
industry-wide practice and due to the long history of PVC is generally considered to be
i •»
acceptable.
4. The plasticizer(s) should be certified by the manufacturer as having a successful past
performance or as having been used on a specific number of projects.
3.1.4.3 Filler
The filler used in a PVC formulation is a relatively small component (recall Table 3.1), and
(if used at all) is generally not identified. Calcium carbonate, in powder form, has been used but
other options also exist. Certification as to successful past performance could be requested.
3.1.4.4 Additives
Other additives for the purpose of ease of manufacturing, coloring and stabilization are also
added to the formulation. They are generally not identified. Certification as to successful past
performance may be requested.
3.1.5 Chlorosulfonated Polvethvlene (CSPE-R^)
As seen in Table 3.1, chlorosulfonated polyethylene (CSPE) geomembranes consist of
Chlorosulfonated polyethylene resin,' fillers, carbon black (or colorants) and additives. The
finished geomembrane is usually fabricated with a fabric reinforcement, called a "scrim", between
the individual plys of the material. It is then designated as CSPE-R.
3.1.5.1 Resin
There are two different types of chlorosulfonated polyethylene resin used to make CSPE
geomembranes. One is a completely amorphous polymer while the other is a thermoplastic
material containing a controlled amount of crystallinity to provide useful physical properties in the
uncured state while maintaining flexibility without the need of any plasticizers. The second type is
generally used to manufacture geomembranes. CSPE is made directly from branched polyethylene
by adding chlorine and sulfur dioxide. The chlorosulfonic groups act as preferred cross-linking
sites during the polymer aging process. In the typical commercial polymer there is one
chlorosulfonyl group for each 200 backbone carbon atoms.
CSPE resin pieces usually arrive at the sheet manufacturing facility in large cartons. They
are somewhat pillow shaped (about 1 cm diameter) and 2 cm in length. The resin pieces (see Fig.
3.3) are relatively spongy in their resistance to finger pressure. Alternatively, CSPE can be
premixed with carbon black in slab form which is then referred to as a master batch. The master
batch is usually made by a formulator and shipped to the manufacturing facility in a prepared form.
107
-------
Fig. 3.3 - CSPE Resin Pieces
I-CDT3 In.PreParati°n °^a specification or MQA document, the following items concerning the
CorJb, resin should considered.
1. The CSPE resin should be made from completely virgin materials.
2. The formulation will usually be based on 40 to 60% of resin, by weight.
3. Typical MQC tests on the CSPE resin will be Mooney viscosity, chlorine content sulfur
content and a series of vulcanization properties (e.g., rheometry and high temperature
4' PeSPE,resin can te Premixed with carbon black in slab form (referred to as a "master
batch ) and shipped to the manufacturers facility.
5. Additional quality control certification procedures used by the manufacturer should be
implemented and followed.
6. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
108
-------
3.1.5.2 Carbon Black
The amount of carbon black in CSPE geomembranes varies from 5 to 36%. The carbon
black functions as an ultraviolet light blocking agent, as a filler and aids in processing. The usual
types of carbon black used in CSPE formulations are N 630, N 774, N 762 and N 990 as per
ASTM D-1765. When low percentages of carbon black are used N 110 to N 220 should be used.
When the carbon black is premixed with the resin and produced in the form of a master batch of
pellets, it is fed directly into the mixer with the other components, such as fillers, stabilizers and
processing aids.
A specification on carbon black in CSPE geomembranes, could be framed around the type
and amount of carbon black as just described, but this is rarely the case. Typical MQC certification
procedures should be available and implemented.
3.1.5.3 Fillers
The purposes of blending fillers into the CSPE compound are to provide workability and
processability. The common types of fillers are clay and calcium carbonate. Both are added in
powder form and in quantities ranging from 40 to 50%.
Specifications are rarely written around this aspect of the material, however MQC
certification procedures should be available and implemented.
3.1.5.4 Additives
Additives are used in CSPE compounds for the purpose of stabilization which is used to
distinguish the various grades. The industrial grade of CSPE geomembranes uses lead oxide as a
stabilizer, whereas the potable water grade uses magnesium oxide or magnesium hydroxide.
These stabilizers function as acid acceptors during the polymer aging process. During aging,
hydrogen chloride or sulfur dioxide releases from the polymer and the metal oxides react with these
substances inducing cross linking over time.
Specifications are rarely written around the type and quantity of additives used in CSPE,
however MQC certification procedures should be written around each additive, be available and be
implemented.
3.1.5.5 Reinforcing Scrim
CSPE geomembranes are usually fabricated with a reinforcing "scrim" between two plys of
polymer sheets. This results in a three-ply laminated geomembrane consisting of geomembrane,
scrim, geomembrane which is sealed together, under pressure, to form a unitized system. The
geomembrane is said to be reinforced and then carries the designation CSPE-R. Other options of
multiple plys are also available. The scrim imparts dimensional stability to the material which is
important during storage, placement and seaming. It also imparts a major increase in mechanical
properties over the unreinforced type, particularly in the tensile strength, modulus of elasticity and
tear resistance of the final geomembrane. , ,
The reinforcing scrim for CSPE geomembranes is a woven fabric made from polyester
yarns in a standard "basket" weave. Note that there are usually many fine fibers (of very fine
diameter) per individual yarn, e.g., 100 to 200 fibers per yarn depending on the desired strength.
The yarns, or "strands" as they are referenced in the industry, are spaced close enough to one
another to achieve the desired properties, but far apart enough to allow open space between them
109
-------
so that the opposing geomembrane sheet surfaces can adhere together. This is sometimes referred
to as stoke-through and is measured by a ply-adhesion test. The designation of reinforcing
scnm is based on the number of yarns, or strands, per inch of woven fabric. The general ranee is
from 6x6 to 20 x 20, with 10 x 10 being the most common. A 10 x 10 scrim refers to 10 strands
per inch in the machine (or warp) direction and an equal number of 10 strands per inch in the cross
machine (or weft) direction.
It must also be mentioned that the polyester scrim yarns must be coated for them to have
good bonding to the upper and lower CSPE sheets. Various coatings, including latex, polyvinyl
chloride and others, have been used. The exact formulation of the coating material (or "olv
enhancer ) is usually proprietary. ' '
^ f Regarding a specification or MQA document for the fabric scrim in CSPE-R geomembranes
the following applies.
1 . The type of polymer used for the scrim is usually specified as polyester, although nylon
has been used in the past. It should be identified accordingly.
2. The strength of the fabric scrim can be specified and, when done, is best accomplished
in tensile strength units of pounds per individual yarn rather than individual fiber
strength.
3. The strike-through is indirectly quantified in specifications on the basis of ply adhesion
requirements. This will be discussed later.
3.1.6 Other Calendered Genmembranes
Within the category of calendered geomembranes there are other types that have not been
described thus far They will be briefly noted here along with similarities and/or differences to
those just described.
Chlorinated polyethylene (CPE) has been used as a polymer resin in the past for either non-
nefn0r S??m. reinforced geomembranes. Its production and ingredients are similar to CSPE
or Li>.FJi-R, with the obvious exception of the nature of the resin itself. In contrast to CSPE CPE
contains no sulfur in its formulation.
f Ethylene interpolymer alloy (EIA) is always used as a reinforced geomembrane thus EIA-R
is its proper designation. The resin, is a blend of ethylene vinyl acetate and polyvinyl chloride
resulting in a thermoplastic elastomer. The fabric reinforcement is a tightly woven polyester which
requires the polymer to be individually spread coated on both sides of the fabric. Note however
that there are other related products being developed under different trademarks in this general
category. °
Among the newer geomembranes is polypropylene (PP) which is a very flexible olefmic
polymer based on new polypropylene resin technology. This polymer has been converted into
sheet by calendering, with and without scrim reinforcement, and by flat die and blown film
extrusion processes. Factory fabrication of large panels is possible. The initial field trials of this
type of geomembrane are currently ongoing.
3.2 Manufacturing
Once the specific type of geomembrane formulation that is specified has been thoroughly
110
-------
mixed it is then manufactured into a continuous sheet. The two major processes used for
manufacturing of the various types of sheets of geomembranes are variations of either extrusion
(e.g., for HOPE, VLDPE, and LLDPE) or calendering (e.g., for PVC, CSPE and PP). Spread
coating (the least used process) will be briefly mentioned in section 3.2.8.
3.2.1 Blending. Compounding. Mixing and/or Masticating
Blending, compounding, mixing and/or masticating of the various components described in
Section 31 is conventionally done on a weight percentage basis. However, each geomembrane's
processing is somewhat unique in its equipment and procedures. Even for a particular type of
geomembrane, manufacturers will use different procedures, e.g., batch methods versus continuous
feed systems, for blending or mixing.
Nevertheless, a few general considerations are important to follow in the preparation of a
specification or MQA document.
1. The blending, compounding, mixing and/or masticating equipment must be clean and
completely purged from previously mixed materials of a different formulation. This
might require sending a complete cycle of purging material through the system,
sometimes referred to as a "blank".
2. The various components of the formulation are added on a weight percentage basis to an
accuracy set by industry standards. Different components are often added to the mixture
at different locations in the processing, i.e., the entire batch is not necessarily added at
the outset.
3. By the time the complete formulation is ready for extrusion or calendering it must be
completely homogenized. No traces of segregation, agglomeration, streaking or
discoloration should be visually apparent jn the finished product.
3.2.2 Regrind. Reworked or Trim Reprocessed Material
,'' "Regrind", "reworked" or "trim" are all terms which can be defined as finished
geomembrane sheet material which has been cut from edges or ends of rolls, or is off-specification
from a surface blemish, thickness or other property point of view. Figure 3.4(a) shows a
photograph of HOPE regrind chips. VLDPE chips appear similar to HOPE. Figure 3.4(b) shows
a photograph of PVC edge strips i.e., edge of sheet material cut off to meet specific roll width
requirements. Excess edge trimmings of PVC sheet is fed back into the, production system.
CSPE-R trim can be added similarly, however without any reinforcing scrim.
These materials are reintroduced during the blending, compounding and/or mixing stage in
controlled amounts as a matter of cost efficiency on the part of the manufacturer. Note that
regrind, rework and trim material must be clearly distinguished from "recycled", or "reclaimed',
material which is finished sheet material that has actually seen some type of service performance
and has subsequently been returned to the manufacturing facility for reuse into new sheet material.
In preparing a specification or MQA document on the use of reprocessed material, the
following items should bs considered:
1. Regrind, reworked or trim materials in the form of chips or edge strips may be added if
the material is from the same manufacturer and is exactly the same formulation as the
geomembrane being produced.
ill
-------
Polyethylene "Regrind" Chips
y(Sk MfcttK, . . fc/uJ .JO JU3
=%) 33SVH9(K»- '
i.l.i lo.l.i.l.i l.i.l.i.l.i,l,i,!,i,l°i.[,irl,i.l.i,,,i.!.i.i.(.!.r.l.i.l,i...ij
Figure 3.4(a) - HOPE Regrind Chips
Figure 3.4(b) - PVC Edge Strips
Figure 3.4 - Photographs of Materials to be Reprocessed
112
-------
2. Generally HOPE and VLDPE will be added in chip form as "regrind" in controlled
amounts into the hopper of the extruder.
3. Generally PVC, CSPE and PP will be added in the form of a continuous strip of edge
trimmings into the roll mill which precedes calendering. For scrim reinforced
geomembranes it is important that the edge trim does not contain any portion of the
fabric scrim.
4. The maximum amount of regrind, reworked or trim material to be added is a topic of
considerable debate. Its occurrence in the completed sheet is extremely difficult, if not
impossible, to identify much less to quantify by current chemical fingerprinting
methods. Thus its maximum amount is not suggested in this manual. It should be
mentioned that if regrind is not permitted to be used, the manufacturer may charge a
premium over current practice.
5. It is generally accepted that no amount of "recycled", or "reclaimed" sheet material (in
any form whatsoever) should be added to the formulation.
3.2.3 High Density Polyethylene CHOPS)
High density polyethylene (HDPE) geomembranes are manufactured by taking the mixed
components described earlier and feeding them into a hopper which leads to a horizontal extruder,
see Fig. 3.5. In the manufacturing of HDPE geomembranes many extruders are 200 mm (8.0
inch) diameter systems which are quite large, e.g., up to 9 m (30 ft. long). In an extruder, the
components enter a feed hopper and are transported via a continuous screw through a feed section,
compression stage, metering stage, filtering screen and are then pressure fed into a die. The die
options currently used for HDPE geomembrane production are either flat horizontal dies or
circular vertical dies, the latter production technique often being referred to as "blown film"
extrusion. The length of flat dies and the circumference of circular dies determine the width of the
finished sheet and vary greatly from manufacturer to manufacturer. Some detail is given below.
Feed
Hopper
Continuous
Screw
Drive
Mechanism
vvvvvvvx\\\
* ^—JL—__^__«^^««^_a««J»w-^_««Hi^B»w^—••
Breaker Plate and
Rlter Screen
Feed
Section
Compression Metering
Section
Section
Figure 3.5 - Cross-Section Diagram of a Horizontal Single-Screw Extruder for Polyethylene
113
-------
3.2.3.1 Flat Die - Wide Sheaf
A conventional HDPE geomembrane sheet extruder can feed enough polymer to produce
sheet up to approximately 4.5 m (15 ft.) wide in typical HDPE thicknesses of 0.75 to 3.0 mm (30
to 120 mils), see Fig. 3.6. Recently, one manufacturer has used two such extruders in parallel to
produce sheet approximately 9.0 m (30 ft.) wide.
Figure 3.6 - Photograph of a Polyethylene Geomembrane Exiting from a Relatively Narrow Flat
Horizontal Die
Insofar as a specification or MQA document for finished HDPE geomembranes made bv
flat die extrusion, the following items should be considered.
1. The finished geomembrane sheet must be free from pinholes, surface blemishes,
scratches or other defects (e.g., nonuniform color, streaking, roughness, carbon black
agglomerates, visually discernible regrind, etc.).
2. The nominal and minimum thicknesses of the sheet should be specified. The minimum
value is usually related to the nominal thickness as a percentage. Values range from 5%
to 10% less than nominal.
114
-------
3. The maximum thickness of the sheet is rarely, if ever, specified. This is for the obvious
reason that if a manufacturer wishes to supply sheet thicker than specified it is generally
acceptable. It is also done, however, to allow for those manufacturers with unique
variations of flat die extrusion (such as horizontal ribs or factory fabricated seams) to not
be excluded from the market.
4. The finished sheet width should be controlled to be within a set tolerance. This is
usually done by creating a sheet larger than called for, and trimming the edges
immediately before final rolling onto the wind-up core. (The edge trim is subsequently
ground into chips and used as regrind as previously described). Flat die extrusion of
HDPE sheet should meet a ± 2.0% width specification.
5. Other MQC tests such as strength, puncture, tear, etc. should be part of a certification
program which should be available and implemented.
6. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
7. The trimmed and finished sheet is wound onto a hollow wind-up core which is usually
heavy cardboard or (sometimes) plastic pipe. The outside diameter of the core should be
at least 150 mm (6.0 in). It obviously must be stable enough to support the roll without
buckling or otherwise failing during handling, storage and transportation.
8. Partial rolls for site specific project details may be cut and prepared for shipment per the
contract drawings.
3.2.3.2 Flat Die - Factory Seamed
Since there are commercial extruders which produce sheets less than 6 m (20 ft) wide, the
resulting sheet widths can be factory seamed into wider panels before shipment to the field. All of
the specification details just described apply to narrow sheets as well as to wide sheets.
The method of factory seaming should be left to the discretion of the manufacturer. The
factory seams, however, must meet the same specifications as the field seams (to be described
later).
3.2.3.3 Blown Film
By using a vertically oriented circular die the extruder can feed molten polymer in an
upward orientation creating a large cylinder of polyethylene sheet, see Fig. 3.7. Since the cylinder
of polymer is closed at the top where it passes over a set of nip rollers which advances the
cylinder, air is generally blown within it to maintain its dimensional stability. Note that upward
moving air is also outside of the cylinder to further aid inrstability. After passing through the nip
rollers, the collapsed cylinder is cut longitudinally, opened to its full width, brought down to floor
level and rolled onto a wind-up core. Note that collapsing the cylinder and passing it through the
nip rollers results in two creases. After slitting the collapsed cylinder and opening it to full width,
remnants of the two creases remain.
115
-------
Figure 3.7 (a) - Photograph of Blown Film Manufacturing of Polyethylene Geomembranes
Nip Rollers
Feed
\ Hopper
Cut Here and
Unfolded
2-Station Wind
up for Continuous
Operation
Fig. 3.7(b) - Sketch of Blown Film Manufacturing of Polyethylene Geomembranes
116
-------
Regarding a specification or MQA document for blown film produced HDPE
geomembranes, the following applies:
1. The finished geomembrane sheet shall be free from pinholes, surface blemishes,
scratches or other defects (e.g., nonuniform color, streaking, roughness, carbon black
agglomerates, visually discernible regrind, etc.). Note that two machine direction
creases from nip rollers are automatically induced into the finished sheet at the 1/4
distances from each edge.
2. The nominal and minimum thickness of the sheet should be specified. The minimum
value is usually related to the nominal thickness as a percentage. Values referenced
range from 5% to 10% less than nominal.
3. The maximum thickness of the sheet is rarely, if ever, specified. This is for the obvious
reason that if a manufacturer wishes to supply sheet thicker than specified it is generally
acceptable.
4. The finished sheet width should be controlled to be within a set tolerance. HDPE
geomembrane made from the blown film extrusion method should meet a ± 2.0% width
specification.
5. Other MQC tests such as tensile strength, puncture, tear, etc., should be part of a
certification program which should be available and implemented.
6. The finished sheet is wound onto a hollow wind-up core which is usually heavy
cardboard or sometimes plastic pipe. The outside diameter of the core should be at least
150 mm (6.0 in.). It must be stable enough to support the roll without buckling or
otherwise failing during handling, storage and transportation.
7. It is important that the two creases located at the 1/4-points from the edges of the sheet
are wound on the core such that they will face upward when deployed in the field. The
reason for this is so that scratches will not occur on the creases if the sheets are shifted
on the soil subgrade when in an open and flat position.
8. Partial rolls for site specific project details may be cut and prepared for shipment as per
the contract drawings.
3.2.3.4 Textured Sheet
By creating a roughened surface on a smooth HDPE sheet, a process called "texturing" in
this document, a high friction surface can be created. There are currently three methods used to
texturize smooth HDPE geomembranes: coextrusion, impingement and lamination, see Fig. 3.8.
The coextrusion method utilizes a blowing agent in the molten extrudate and delivers it
from a small extruder immediately adjacent to the main extruder. When both sides of the sheet are
to be textured, two small extruders (one internal and one external to the main extruder) are
necessary. As the extrudate from these smaller extruders meets the cool air the blowing agent
expands, opens to the atmosphere and creates the textured surface(s).
117
-------
(a) Coextrusion with Nitrogen Gas
Mixer
Spray
Equip.
Finished
Textured
Sheet
Die
Main Core Extruder
Internal Extruder (N2 Gas)
External Extruder (N2 Gas)
/^Smooth
•H
Spray
Equip.
' N Finished
Of) Textured
(b) Impingement of Hot Polyethylene Particles
Hot PE Foam
Spreader Bar
Smooth Roll Finished Textured Roll
(Repeat Opposite Side for Double Sided Texture)
(c) Lamination with Polyethylene Foam
Figure 3.8 - Various Methods Currently Used to Create Textured Surfaces on HDPE
Geomembranes
118
-------
Impingement of hot HOPE particles against the finished HDPE sheet is a second method of
texturing. In this case, hot particles are actually projected onto the previously prepared sheet on
one or both of its surfaces in a secondary operation. The adhesion of the hot particles to the cold
surface(s) should be as great, or greater, than the shear strength of the adjacent soil or other
abutting material. The lengthwise edges of the sheets can be left non-textured for up to 300 mm
(12 in.) so that thickness measurements and field seaming can be readily accomplished.
The third method for texturizing HDPE sheet is by lamination of an HDPE foam on the
previously manufactured smooth sheet in a secondary operation. In this method a foaming agent
contained within molten HDPE provides a froth which produces a rough textured laminate adhered
to the previously prepared smooth sheet. The degree of adhesion is important with respect to the
shear strength of the adjacent soil or other abutting material. If texturing on both sides of the
geomembrane is necessary, the roll must go through another cycle but now on its opposite side.
The lengthwise edges of the sheets can be left non-textured for up to 300 mm (12 in.) so that
thickness measurements and field seaming can be readily accomplished.
Regarding the writing of a specification or MQA document on textured HDPE
geomembranes the following points should be considered.
1. The surface texturing material should be of the same type of polymer and formulation as
the base sheet polymer and its formulation. If other chemicals are added to the texturing
material they must be identified in case of subsequent seaming difficulties.
2. The degree of texturing should be sufficient to develop the amount of friction as needed
per the manufacturers specification and/or the project specifications.
3. The quality control of the texturing process can be assessed for uniformity using an
inclined plane test method, e.g., GRIGS-7*.
4. The actual friction angle for design purposes should come from a large scale direct shear
test simulating site specific conditions as closely as possible, e.g., ASTM D-5321.
5. The thickness of the base geomembrane should be micrometer measured (according to
ASTM D-751) along the smooth edge strips of textured geomembranes made by
impingement or lamination. For those textured geomembranes with no smooth edge
strips, i.e., for blown film coextruded materials, an overall average thickness can be
estimated on the basis of the roll weight divided by total area with suitable incorporation
of the density of the material. Alternatively, a tapered point micrometer for measuring
screw threads has also been used for point-to-point measurements.
6. Other MQC tests such as tensile strength, puncture, tear, etc., should be part of a
certification program which should be available and implemented.
7. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
* The Geosynthetic Research Institute (GRI) provides interim test methods for a variety of geosynthetic related
topics until such time as consensus organizations (like ASTM) adopt a standard on the same topic. At that time the
GRI standard is abandoned.
119
-------
3.2.4 Very Low Density Polyethylene (VLDPE')
Very low density polyethylene (VLDPE) geomembranes are manufactured by taking the
mixed components described earlier and feeding them into a hopper which leads to a horizontal
extruder, recall Fig. 3.5. In the extruder, the blended components enter via a feed hopper and are
transported via a continuous screw, through a feed section, compression stage, metering stage,
filtering screen and are then pressure fed into a die. The die options currently used for VLDPE
geomembrane production are either flat horizontal dies or circular vertical dies, the latter often
being referred to as "blown film" extrusion. The width of flat dies and the circumference of
circular dies vary greatly from manufacturer to manufacturer. The techniques are the same as were
described in the manufacture of HDPE geomembranes.
3.2.4.1 Flat Die - Wide Sheet
A conventional VLDPE sheet extruder can feed enough polymer to produce sheet up to
approximately 4.5 m (15 ft.) wide in typical VLDPE thicknesses of 0.75 to 3.0 mm (30 to 120
mils), recall Fig. 3.6. In developing a specification or MQA document for the manufacture of
VLDPE geomembranes the following should be considered:
1. The finished geomembrane sheet must be free from pinholes, surface blemishes,
scratches or other defects (e.g, carbon black agglomerates, visually discernible regrind,
etc.).
2. The minimum thickness of the sheet should be specified. It is usually related to the
nominal thickness as a percentage. Values range from 5% to^!0% less than nominal.
3. The maximum thickness of the sheet is rarely, if ever, specified. This is for the obvious
reason that if a manufacturer wishes to supply sheet thicker than specified it is generally
acceptable. It is also done, however, to allow for those manufacturers with unique
variations of flat die extrusion (such as horizontal ribs or factory fabricated seams) to not
be excluded from the market.
4. The finished sheet width should be controlled to be within a set tolerance. This is
usually done by creating a sheet larger than called for, and trimming the edges
immediately before final rolling onto the wind-up core. (The edge trim is subsequently
ground into chips and used as regrind as previously described). Flat die extrusion of
VLDPE sheet can readily meet a ± 0.25% width specification.
5. Other MQC tests such as tensile strength, puncture, tear, etc. should be part of a
certification program which should be available and implemented.
6. The trimmed and finished sheet is wound onto a hollow wind-up core which is usually
heavy cardboard or sometimes plastic pipe. The outside diameter of the core should be
at least 150 mm (6.0 in), ft obviously must be stable enough to support the roll without
buckling or otherwise failing.
7. Partial rolls for site specific project details may be cut and prepared for shipment as per
contract drawings.
3.2.4.2 Flat Die - Factory Seamed
Since there are commercial extruders which produce significantly narrower sheet than just
120
-------
discussed, the resulting narrow sheet widths can be factory seamed into wider panels before
shipment to the field. All of the specification details just described apply to narrow sheets as well
as to wide sheets.
The method of factory seaming should be left to the discretion of the manufacturer. The
factory seams, however, must be held to the same destructive and nondestructive testing
procedures as with field seams (to be described later).
3.2.4.3 Blown Film
By using a circular die oriented vertically the extruder can feed molten polymer in an
upward orientation creating a large cylinder of polymer, recall Fig. 3.7. Since the cylinder is
closed at the top where it passes over a set of nip rollers which advances the cylinder, air is
generally contained within it maintaining its dimensional stability. Note that upward moving air is
also outside of the cylinder to further aid in stability. After passing beyond the nip rollers the
cylinder is cut longitudinally, opened to its full width, brought down to floor level and rolled onto
a stable core.
The following items should be considered in preparing a specification or MQA document
for blown film VLDPE geomembranes.
1. The finished geomembrane sheet shall be free from pinholes, surface blemishes,
scratches or other defects (carbon black agglomerates, visually discernible regrind, etc.).
Note that two machine direction creases from nip rollers are automatically induced into
the finished sheet at the 1/4 distances from each edge.
2. The minimum thickness of the sheet should be specified. It is usually related to the
nominal thickness as a percentage. Values referenced range from 5% to 10% less than
nominal.
3. The maximum thickness of the sheet is rarely, if ever, specified. This is for the obvious
reason that if a manufacturer wishes to supply sheet thicker than specified it is generally
acceptable.
4. The finished sheet width should be controlled to be within a set tolerance. VLDPE
geomembrane made from the blown film extrusion method should meet a ± 2.0% width
specification.
5. Other MQC tests such as tensile strength, puncture, tear, etc. should be part of a
certification program which should be available and implemented.
6. The finished sheet is wound onto a hollow wind-up core which is usually heavy
cardboard or sometimes plastic pipe. The outside diameter of the core should be at least
150 mm (6.0 in.). It obviously must be stable enough to support the roll without
buckling or otherwise failing.
7. Partial rolls for site specific project details may be cut and prepared for shipment as per
contract drawings.
3.2.4.4 Textured Sheet
By creating a roughened surface on a smooth VLDPE sheet, a process called "texturing" in
121
-------
this document, a high friction surface can be created. There are currently three methods used to
texturize smooth VLDPE geomembranes: coextrusion, impingement and lamination, recall Fig.
3.8.
The coextrusion method utilizes a blowing agent in the molten extrudate and delivers it
from a small extruder immediately adjacent to the main extruder. When both sides of the sheet are
to be textured, two small extruders, one internal and one external to the main extruder, are
necessary. As the extrudate from these smaller extruders meets the cool air the blowing agent
expands, opens to the atmosphere and creates the textured surface(s).
Impingement of hot polyethylene particles against the finished VLDPE sheet is a second
method of texturing. In this case, hot particles are actually projected onto the previously prepared
sheet on one or both of its surfaces in a secondary operation. The adhesion of the hot particles to
the cold surface(s) should be as great, or greater, than the shear strength of the adjacent soil or
other abutting material. The lengthwise edges of the sheets can be left non-textured for up to 30
cm (12 in.) so that thickness measurements and field seaming can be readily accomplished.
The third method for texturizing VLDPE sheet is by lamination of a hot polyethylene foam
on the previously manufactured smooth sheet in a secondary operation. In this method a foaming
agent contained in molten polyethylene provides a froth which produces a rough textured laminate
adhered to the previously prepared smooth sheet. The degree of adhesion is important with respect
to the shear strength of the adjacent soil or other abutting material. If texturing of both sides of the
geomembrane is necessary the roll must go through another cycle but now on its opposite side.
The lengthwise edges of the sheets can be left non-textured for up to 300 mm (12 in.) so that
thickness measurements and field seaming can be readily accomplished.
Regarding the writing of a specification or MQA document on textured VLDPE
geomembranes the following points should be considered.
1. The surface texturing material should be polyethylene of density equal to the VLDPE, or
greater. The latter is often the case. If other chemicals are added to the texturing
material they must be identified in case of subsequent seaming difficulties.
2. The degree of texturing should be sufficient to develop the amount of friction as needed
per the manufacturers specification and/or the project specifications.
3. The quality control of the texturing process can be assessed for uniformity using an
inclined plane test method, e.g., GRIGS-7.
4. The actual friction angle for design purposes should come from a large scale direct shear
test simulating site specific conditions as closely as possible, e.g., ASTM D-5321.
5. The thickness of the base geomembrane should be micrometer measured (according to
ASTM D-751) along the smooth edge strips of textured geomembranes made by
impingement or lamination. For those textured VLDPE geomembranes with no smooth
edge strips, i.e., for blown film coextruded materials, an overall average thickness can
be estimated on the basis of the roll weight divided by total area with suitable
incorporation of the density of the material. Alternatively, a tapered point micrometer for
measuring screw threads has also been used for point-to-point measurements. Care
must be exercised, however, because VLDPE thickness measurements with a point
micrometer are very sensitive to pressure.
122
-------
6. Other MQC tests such as tensile strength, puncture, tear, etc., should be part of a
certification program which should be available and implemented.
7. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
3.2.5 Coextrusion Processes
As mentioned previously in Section 3.1.3, there are other variations of manufacturing
polyethylene geomembranes. The basic manufacturing principle of adding the desired components
to an extruder and having the molten polymer exit a flat horizontal die or a circular vertical die is
always the same. What is different between these variations and the single component HDPE or
VLDPE just described is the coextrusion process along with the idiosyncrasies of the particular
materials utilized.
In coextrusion, two or three extruders simultaneously introduce molten polymer into the
same die. As the different materials exit the die and are cooled they commingle with one another
such that local blending and molecular entanglement occur and no discrete separation layer exists.
Thus coextrusion is fundamentally different from the lamination of different surfaces together or of
preformed sheets together under heat and pressure. Different variations of coextrusion of
polyethylene geomembranes are described as follows.
Since polyethylene resin is supplied as a opaque pellet, the addition of colorants (rather than
carbon black) can produce white, blue, green, etc., colored geomembranes. The benefit for
geomembranes having these light colors is to reduce the surface temperature of the geomembrane
when it is required to be exposed, e.g., as liners for surface impoundments or floating covers for
reservoirs. Figure 3.9 shows how the temperature differences between white and black can be
very significant. The white (or light) colors generally utilize titanium dioxide (or other metal
oxides) in amounts not exceeding 1.0% by weight. Note that only a thin surface layer
(approximately 10-20% of the total thickness) is treated in this manner. The balance of the
geomembrane contains carbon black and is treated in the same manner as described previously.
70
O
2
I
I
60-
50 -
40-
30-
20 4
Black Geomembrane
White Geomembrane
60
120
180
240
300
Time (mins.)
Figure 3.9 - Geomembrane Surface Temperature Differences Between Black and White Colors
A second variation of polyethylene is to coextrude a "sandwich" of HDPE on each side of
VLDPE in the center. The purpose of such a combination is to provide high chemical resistance on
the top and bottom of the sheet (via the HDPE) and to have high flexibility and out-of-plane
123
-------
elongation properties within the core (via the VLDPE). The thickness percentages of these
components are approximately 20%, 60% and 20% of the total thickness of the sheet, respectively.
Third, it is possible to coextrude a surface layer to conventional HDPE or VLDPE which
contains a gas that expands when cooled. Thus the molten polymer moves through the die in a
regular manner only to have the expanding gas rapidly exit on its surface(s). This forms a
roughened, or textured, surface which depends on the amount of gas and thickness of the
coextruded surface layer. Similar extruders can be used on both sides of the parent sheet. The
purpose of such texturing is to increase the interface friction between the textured geomembrane
and the material above and/or below it, refer to Sections 3.2.3.4 and 3.2.4.4.
Lastly, it is possible to coextrude other polymers than polyethylene. As noted in Section
3.1.3, fully crosslinked elastomeric alloys (FCEA) can be extruded or could be coextruded with
other polymers.
3.2.6 Polvvinvl Chloride (PVO
Polyvinyl chloride (PVC) geomembranes are manufactured by taking proportional weight
amounts of PVC resin (a dry powder) and plasticizer (a liquid) and premixing them until the
plasticizer is absorbed into the resin. Filler (in the form of a dry powder) and other additives (also
usually dry powders) are then added to the plasticized resin and the total formulation is mixed in a
blender. Various types of high intensity or low intensity blenders can be used. Note that PVC
rework in the form of chips, rather than edge trim, can be introduced at this point.
The resulting free-flowing powder compound is fed into a mixer which has heat introduced
thereby initiating a reaction between the various components. These mixers can be either batch
type (e.g., Banbury) or continuous types (e.g., Parrel), see Figs. 3.10(a) and (b), respectively. In
these mixers, the temperature is approximately 180°C (350°F) which melts the mixture into a
viscous mass. The mixed material is then removed from the discharge door or port onto a
conveyor belt. From the conveyor belt the viscous material is further worked (called
"masticating") in a rolling mill (or mills) into a smooth, consistent, uniform color, continuous mass
of 100-150 mm (4-6 in.) in diameter. Finished product edge trim can also be introduced into the
rolling mill at this point. The fully mixed formulation is then fed by conveyor directly into the
sizing calender.
3.2.6.1 Calendering
PVC formulations, irrespective of the pre-processing procedures, are manufactured into
continuous geomembrane sheets by a calendering process. The viscous feed of polymer coming
from the rolling mill(s) is worked and flattened between counter-rotating rollers into a
geomembrane sheet. Most calenders are "inverted-L" configurations, see Fig. 3.11, but other
options also exist. The rollers are usually smooth surfaced (they can be slightly textured) stainless
steel cylinders and are up to 200 cm (80 in.) in width. The opening distance between adjacent
cylinders is set for the desired thickness of the final sheet. A rolling bank of molten material is
formed between adjacent rolls. In an inverted four roll "L" calender, 3 such banks are formed.
They act as reservoirs for the molten material, and help to fill the sheet to full thickness as it passes
between the rolls. As the geomembrane exits from the calender, it enters an additional series of
rollers for the purposes of pickoff, embossing, stripping, cooling and cutting. At least one, and
perhaps two, rollers in PVC manufacturing are embossed so as to impart a surface texture on the
geomembrane. The purpose of this embossing is to prevent the rolled geomembrane from sticking
together, i.e., "blocking", during wind-up, storage and transportation.
124
-------
Sliding
Discharge
Door
Feed Hopper
Rotors
Cooling/
Heating
Channels
(a) Batch Process Mixer
Feed
Dischargp
Orifice
Gate
Discharge
(b) Continuous Type Mixer
Figure 3.10 - Sketches of Various Process Mixers
125
-------
Feed
Feed
Rolling Bank
(b) INVERTED L
(a) VERTICAL
Rolling Bank
(c) INCLINED Z
Figure 3.11 - Various Types of Four-Roll Calenders
In developing a specification or MQA document for the manufacturing of PVC
geomembranes the following considerations are important:
1. The finished geomembrane sheet should be free from pinholes, surface blemishes,
scratches or other defects (agglomerates of various additives or fillers, visually
discernible rework, etc.)
2. The finished geomembrane sheet surfaces should be of a uniform color.
3. The addition of a dusting powder, such as talc, to eliminate blocking is not an
acceptable practice. The powder will invariably attach to the sheet or be trapped within
126
-------
the embossed irregularities and eventually be contained in the seamed area as a
potential contaminant which could effect the adequacy of the seam.
4. The nominal and minimum thickness of the sheet should be specified. The minimum
thickness of the finished geomembrane sheet is usually limited to the nominal
thickness minus 5%.
5. The maximum thickness of the finished geomembrane sheet is generally not specified.
6. The width of the finished PVC geomembrane is dependent on the type of calender
used by the manufacturer.
7. The geomembrane sheet should be edge trimmed to result in a specified width. This
should be controlled to within ± 0.25%.
8. Various MQC tests such as tensile strength, puncture, tear, etc. should be part of a
certification program which should be available and implemented.
9. The frequency of performing each of the preceding tests should be covered in the
MQC plan and it should be implemented and followed.
10. The finished geomembrane sheet should be rolled onto stable wind-up cores of at least
75 mm (3.0 in.) in diameter.
3.2.6.2 Panel Fabrication
PVC geomembranes as just described are typically 100 to 200 cm (40 to 80 in.) wide and
are transported in rolls weighing up to 6.7 kN (1500 pounds) to a panel fabrication facility, see
Fig. 3.12 (upper photo). When a specific job order is placed, the rolls are unwound and placed
directly on top of one another for factory seaming into a panel, see Fig. 3.12 (lower photo). A
panel will typically consist of 5 to 10 rolls which are accordion seamed to one another, i.e., the left
side of a particular roll is seamed to the underlying roll while the right side is seamed to the
overlying roll. After seaming, the completed panel is again accordion folded (now in a lengthwise
direction) and placed on a wooden pallet. It is then covered with a protective wrapper and shipped
to the job site for deployment. To be noted is that some fabricators use other procedures for panel
preparation.
Regarding a specification or MQA document for factory fabrication of PVC geomembrane
panels, the following items should be considered.
1. The factory seaming of PVC rolls into panels should be performed by thermal or
chemical seaming methods, see ASTM D-4545. It should be noted that dielectric
seaming is a factory seaming method for joining PVC rolls. This is a thermal (or heat
fusion) method that is acceptable and is unique to factory seaming of flexible
thermoplastic geomembranes. It is currently not a field seaming method.
2. Factory seams should be subjected to the same type of destructive and nondestructive
tests as field seams (to be described later).
3. When factory seams are made by chemical methods they are generally protected against
blocking by covering them with a 100 mm (4 in.) wide strip of thin polyethylene film.
When the panels are unfolded in the field these strips are discarded.
127
-------
Figure 3.12 - Photographs of Calendered Rolls of Geomembranes After Manufacturing (Upper)
and Factory Fabrication of Rolls into Large Panels for Field Deployment (Lower)
128
-------
4. The finished and folded panels must be protected against accidental damage and
excessive exposure during handling, transportation and storage. Usually they are
protected by covering them in a heavy cardboard enclosure and placed on a wooden
pallet for shipping.
5. The cardboard enclosures should be labeled and coded according to the specific job
specifications.
3.2.7 Chlorosulfonated Polyethylene-Scrim Reinforced (CSPE-R)
Chlorosulfonated polyethylene geomembranes are made by mixing CSPE resin with .carbon
black (or their colorants) thereby making a "master batch" of these two components. Added to this
master batch are fillers, additives and lubricants in a batch type mixer, e.g., a Banbury mixer,
recall Fig. 3.10(a). Within the mixer the shearing action of the rotors against the ingredients
generates enough heat to cause melting and subsequent chemical reactions to occur. After the
mixing cycle is complete, the batch is dropped from the Banbury onto a two-roll mill, then to a
conveyor leading to a second two-roll mill. In moving through the roll mill it is further mixed into
a completely homogenized material having a uniform color and texture. It should be noted that
edge trim is often taken from finished sheet and routed back to the roll mill for mixing and reuse.
A conveyor now transports the material directly to the calender, as shown in Fig. 3.11, and
feeds it between the appropriate calender rolls.
3.2.7.1 Calendering
All CSPE formulations are manufactured into gepmembrane sheets by a calendering
process. Here the viscous ribbon of polymer is worked and flattened into a geomembrane sheet.
Most calenders are "inverted-L" configurations, recall Fig. 3.11, but other options also exist. As
the geomembrane exits the calender, it enters a series of rollers for the purposes of pickoff,
stripping, cooling and cutting.
The inverted-L type calender provides an opportunity to introduce two simultaneous
ribbons of the mixed and masticated polymeric compound thereby making two individual sheets of
geomembranes. While this section of the manual is written around CSPE, it should be recognized
that many other geomembrane types which are calendered can be made in multiple ply form as
well. Since they are separately formed geomembrane sheets, they are brought together
immediately upon exiting the calender to provide a laminated geomembrane consisting of two plys.
Additional plys can also be added as desired, but this is not usually done in the manufacture of
CSPE geomembranes.
While producing the two separate plys in an inverted-L calender as mentioned above, a
woven fabric, called a reinforcing scrim, can be introduced between the two plys, see Fig. 3.13.
The CSPE geomembrane is then said to be reinforced and is designed CSPE-R. It is common
practice, however, to just use the acronym CSPE when referring to either the nonreinforced or
reinforced variety of CSPE. The scrim is usually a woven polyester yarn with 6 x 6,10 x 10 or 20
x 20 count. These numbers refer to the number of yarns per inch in the machine and cross machine
directions, respectively. Other scrim counts are also possible.
129
-------
Figure 3.13 - Multiple-Ply Scrim Reinforced Geomembrane
• f Preparation of a specification or MQA document for multiple-ply scrim
reinforced CSPE-R geomembranes the following should be considered.
1. pe finished geomembrane should be free from surface blemishes, scratches and other
detects (additive agglomerates, visually discernible rework, etc.).
2. The finished geomembrane sheet should be of a uniform color (which may be black or
by the addition of colorants, be white, tan, gray, blue, etc.), gloss and surface texture.
3. A uniform reinforcing scrim pattern should be reflected on both sides of the
geomembrane and should be free from such anomalies as knots, gathering of yarns
delammations or nonuniform and deformed scrim.
4. The sheet should not be embossed since the surface irregularities caused by the scrim
are adequate to prohibit blocking.
5. The.thickness of the sheet should be measured over the scrim and at a minimum should
be the nominal thickness minus 10%.
6. The geomembrane sheet should have a salvage, i.e., geomembrane ply directly on
geomembrane ply with no fabric scrim, on both edges. This salvage shall be
approximately 6 mm (0.25 in.).
7. Various MQC tests such as strength, puncture, tear, ply adhesion, etc., should be part
ot a certification program which should be available and implemented.
130
-------
8. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
9. The finished geomembrane sheet should be rolled onto stable wind-up cores of at least
75 mm (3.0 in.) in diameter.
3.2.7.2 Panel Fabrication
CSPE-R geomembranes as just described are typically 100 to 200 cm (40 to 80 in.) wide
and are transported in rolls weighing up to 6.7 kN (1500 pounds) to a panel fabrication facility.
When a specific job order is placed, the rolls are unwound and placed on top of one another for
factory seaming into a panel, recall Fig. 3.12. A panel will typically consist of 5 to 10 rolls
accordion seamed to one another. After seaming, the panel is accordion folded in its length
direction and placed onto a wooden pallet. It is then appropriately covered and shipped to the job
site for deployment. To be noted is that some fabricators use other procedures for panel
preparation.
In preparing a specification or MQA document for CSPE-R geomembrane panels, the
following items should be considered.
1. Factory seaming of CSPE-R rolls should use thermal, chemical or bodied chemical
fusion methods, see ASTM D-4545. It should be noted that dielectric seaming is a
factory seaming method for joining CSPE-R rolls. This is a thermal, or heat fusion,
method that is acceptable and is currently unique to factory seaming of flexible
thermoplastic geomembranes. It is not a field seaming method.
2. Factory seams should be subjected to the same type of nondestructive tests as field
seams (to be described later). A start-up seam is made prior to making panel production
seams from which destructive tests are taken (to be described later).
3. When factory seams are made by chemical fusion methods they are generally protected
against sticking to the adjacent sheet (i.e., blocking) by covering them with 100 mm (4
in.) wide thin strip of polyethylene film. When the panels are unfolded in the field these
strips are discarded. Other systems may not require this film.
4. The folded panels must be protected against accidental damage and excessive exposure
during handling, transportation and storage. Usually they are protected by containing
them in a heavy cardboard enclosure and placed on a wooden pallet for shipping.
5. The cardboard enclosures are labeled and coded according to the specific job
specifications.
3.2.8 Spread Coated Geomembranes
As mentioned previously, an exception to the calendering method of producing flexible
geomembranes, is the spread coating process. This process is currently unique to a geomembrane
type called ethylene interpolymer alloy (EIA-R), but has been used to produce other specialty
geomembranes in the past. The process utilizes a dense fabric substrate, commonly either a woven
or nonwoven textile, and spreads the molten polymer on its surface. Due to the dense structure of
the fabric, penetration of the viscous polymer to the opposite side is usually not complete. When
131
-------
"d the process repeated on the opposite side- Adherence of
mote • Geomembranes PJoduced by the sPread coating method are indeed multiple-ply reinforced
materials, but produced by a method other than calendering. MQC and MQA plans and
specifications should be framed in a similar manner as described previously for CSPE-R
geomembranes.
3.3 Handling
While there should be great concern and care focused on the manufacturers and installers of
S H 1S ?i° incum-b.ent *« they «« Packaged, handled, stored, transported, re-
3~th * e deployed in a manner so as not to cause any damage. This section is
withthesemanyancillaryconsiderationsinmind.
3.3.1 Packaging
Different types of geomembranes require different types of packaging after thev are
S* GeneraJ-ly IP,?E,and *"** ** PackaSed "oSd a core in roll form whilePVC
-R are accordion folded in two directions and packaged onto pallets.
3.3.1.1 Rolls
™ * - f i* ViDPE geomembranes are manufactured and fed directly to a wind-up
Th«l «S L-^ -\ N° ^o1?? wraPPiflg or covering is generally needed, nor provided.
These rolls which weigh up to 22 kN (5000 pounds), are either moved by fork-lifts using a long
rod inserted into the core (called a "stinger") or they are picked up by fabric slings with a Srane o?
•f? J.; i ? i at S JJIS ^^n dedicated to each particular roll and follow along with it until
its actual deployment. The rolls are usually stored in an outdoor area. They are stacked such that
one roll is nested into the valley of the two underlying rolls, see Fig. 3. 14.
following3*!"! a Specification or MQA document for finished rolls of HOPE geomembranes the
L 72% C°f S on. which the rolls of geomembranes are wound should be at least 150 mm
(6.0 in.) outside diameter.
2' fOTliir168 ShdUld ^^ a Sufficient inside diameter such that fork lift stingers can be used
3. The cores should be sufficiently strong that the roll can be lifted by a stinger or with
slings without excessively deflecting, nor structurally buckling the roll.
4. The stacking of rolls at the manufacturing facility should not cause buckling of the cores
nor flattening of the rolls. In general, the maximum stacking limit is 5 rolls high.
5. If storage at the manufacturer's facility is for longer than 6 months, the rolls should be
covered by a sacrificial covering, or placed within a temporary or permanent enclosure.
6. The manufacturer should identify all rolls with the manufacturer's name, product
identification, thickness, roller number, roll dimensions and date manufactured.
132
-------
Figure 3.14 - Rolls of Polyethylene Awaiting Shipment to a Job Site
3.3.1.2 Accordion Folded
PVC and CSPE-R geomembranes are initially manufactured in rolls and are then sent to a
fabricator for factory seaming into panels. At the fabrication facility they are unrolled directly on
top of one another, factory seamed along alternate edges of the rolls and are then accordion folded
both width-wise and length-wise and placed onto wooden pallets for packaging and shipment.
PVC and CSPE-R geomembranes are generally not stored longer than a few weeks at the
fabrication facility.
Regarding items for a specification or MQA document, the following applies.
1. The wooden pallets on which the accordion folded geomembranes are placed should be
structurally sound and of good workmanship so that fork lifts or cranes can transport
and maneuver them without structurally failing or causing damage to the geomembrane.
2. The wooden pallets should extend at least 75 mm (3 in.) beyond the edge of the folded
geomembrane panel on all four sides.
3. The folded geomembrane panel should be packaged in treated cardboard or plastic
wrapping for protection from precipitation and direct ultraviolet exposure.
4. Banding straps around the geomembrane and pallet should be properly cushioned so as
not to cause damage to any part of the geomembrane panel.
133
-------
5. Palleted geomembranes should be stored only on level surfaces since the folded material
is susceptible to shifting and possible damage.
6. The stacking of palleted geomembrane panels on top of one another should not be
permitted.
7' I£St(£afe at the fabricator's facility is for longer than 6 months, the palleted panels
should be covered with a sacrificial covering, temporary shelter or placed within a
permanent enclosure.
8. The fabricator should identify all panels with the manufacturers name, product
information, thickness, panel number, panel dimensions and date manufactured.
3.3-2 Shipment. Handling and Site Storage
The geomembrane rolls or pallets are shipped to the job site, offloaded, and temporarily
stored at a remote location on the job site, see Fig. 3.15.
Regarding items for a specification or CQA document*, the following applies:
1. Unloading of rolls or pallets at the job site's temporary storage location should be such
that no damage to the geomembrane occurs.
2. Pushing, sliding or dragging of rolls or pallets of geomembranes should not be
permitted.
3. Offloading at the job site should be performed with cranes or fork lifts in a workmanlike
manner such that damage does not occur to any part of the geomembrane.
4. Temporary storage at the job site should be in an area where standing water cannot
accumulate at any time.
5. The ground surface should be suitably prepared such that no stones or other rough
objects which could damage the geomembranes are present.
6. Temporary storage of rolls of HDPE or VLDPE geomembranes in the field should not
be so high that crushing of the core or flattening of the rolls occur. This limit is typically
5 rolls high. 3V 3
7. Temporary storage of pallets of PVC or CSPE-R geomembranes by stacking should not
be permitted.
8. Suitable means of securing the rolls or pallets should be used such that shifting, abrasion
or other adverse movement does not occur.
9. If storage of rolls or pallets of geomembranes at the job site is longer than 6 months, a
sacrificial covering or temporary shelter should be provided for protection against
precipitation, ultraviolet exposure and accidental damage.
* Note that the designations of MQC and MQA will now shift to CQC and CQA since field construction personnel
are involved. These designations will carry forward throughout the remainder of this Chapter.
134
-------
;
»•*—m \
Figure 3.15- Photograph of Truck Shipment of Geomembranes
3.3.3 Acceptance and Conformance Testing
It is the primary duty of the installation contractor, via the CQC personnel, to see that the
geomembrane supplied to the job site is the proper material that was called for in the contract, as
specified by the Plans and Specifications. It is also the duty of the GQA Engineer to verify this
material to be appropriate. Clear marking should identify all rolls or pallets with the information
described in Section 3.3.1. A complete list of roll numbers should be prepared for each material
type.
Upon delivery of the rolls or pallets of geomembrane, the CQA Engineer should ensure that
conformance test samples are obtained and sent to the proper laboratory for testing. This will
generally be the laboratory of the CQA firm, but may be that of the CQC firm if so designated in
the CQA documents. Alternatively, conformance testing could be performed at the manufacturers
facility and when completed the particular lot should be marked for the particular site under
investigation.
The following items should be considered for a specification or CQA document with regard
to acceptance and conformance testing.
•*•? - -
1 The particular tests selected for acceptance and conformance testing can be all of those
listed previously, but this is rarely the case since MQC and MQA testing should have
preceded the field operations. However, at a minimum, the following tests are
recommended for field acceptance and conformance testing for the particular
135
-------
geomembrane type.
(a) HOPE: thickness (ASTMD-5199), tensile strength and elongation (ASTMD-638)
and possibly puncture (FTM Std 101C) and tear resistance (ASTM D-1004, Die C)
S£PE:, *«*?«» (AS™ D-5199), tensile strength and elongation (ASTM D-
638) and possibly puncture (FTM Std 101C) and tear resistance (ASTM D-1004,
J_xlC V-» )
(b)
J_xlC V-» )
(ASTMD-
2. The method of geomembrane sampling should be prescribed. For geomembranes on
rolls, 1 m (3 ft.) from the entire width of the roll on the outermost wrap is usually cut
and removed. For geomembranes folded on pallets, the protective covering must be
removed, the uppermost accordion folded section opened and an appropriate size sample
taken. Alternatively factory seam retains can be shipped on top of fabricated panels for
easy access and use in conformance testing.
direcdon must te indicated with an ^ow on all samples using a permanent
4. Samples are usually taken on the basis of a stipulated area of geomembrane, e e one
sample per 10,000 m2 (100,000 ft*). Alternatively, one could take samples aUherat?of
one per lot, however, a lot must be clearly defined. One possible definition could be that
a lot is a group of consecutively numbered rolls or panels from the same manufacturing
5. All conformance test results should be reviewed, accepted and reported by the COA
Engineer before deployment of the geomembrane.
6. Any nonconformance of test results should be reported to the Owner/Operator The
method of a resolution of such differences should be clearly stated in the COA
2SmSn 47?onri^S«Sle ^idance document for failing conformance tests could be
ASTM D-4759 titled Determining the Specification Conformance of Geosynthetics".
3.3.4 Placement
When the subgrade or subbase (either soil or some other geosynthetic) is approved as beine
acceptable, therolls or pallets of the temporarily stored geomembLies are broughTto S inteS
location, unrolled or unfolded, and accurately spotted for field seaming, see Fig. 3. 16 mtenaea
3-3Al Subgrade fSubbasel Conditions
i^r BS!°!if b.eSini?inS ^> move the geomembrane rolls or pallets from their temporary storage
preparedness *** ^^ (°r °ther subbase materiaD should be checked for S
136
-------
Figure 3.16 - Photographs Showing the Unrolling (Upper) and Unfolding (Lower) of
Geomembranes
137
-------
Some items recommended for a specification or CQA document include the following:
1. The soil subgrade shall be of the specified grading, moisture content and density as
required by the installer and as approved by the CQA engineer for placement of the
geomembrane. See Chapter 2 for these details for compacted clay liner subgrades.
2. Construction equipment deploying the rolls or pallets shall not deform or rut the soil
subgrade excessively. Tire or track deformations beneath the geomembrane should not
be greater than 25 mm (1.0 in.) in depth.
3. The geomembrane shall not be deployed on frozen subgrade where ruts are greater than
12 mm (0.5 in.) in depth.
4. When placing the geomembrane on another geosynthetic material (geotextile, geonet,
etc.), construction equipment should not be permitted to ride directly on the lower
geosynthetic material. In cases where rolls must be moved over previously placed
geosynthetics it is necessary to move materials by hand or by using small pneumatic
tired lifting units. Tire inflation pressures should be limited to a maximum value of 40
kPa (6 lb/in2).
5. Underlying geosynthetic materials (such as geotextiles or geonets) should have all folds
wrinkles and other undulations removed before placement of the geomembrane.
6. Care, and planning, should be taken to unroll or unfold the geomembrane close to its
intended, and final, position.
3.3.4.2 Temperature Effects - Sticking/Cracking
High temperatures can cause geomembrane surfaces on rolls, or accordion folded on
pallets, to stick together, a process commonly called "blocking". At the other extreme low
temperatures can cause geomembrane sheets to crack when unrolled or unfolded. Comments on
unrolling, or unfolding of geomembranes at each of these temperature extremes follow.
For example, a specification or CQA document should have included in it the following
items.
1. Geomembranes when unrolled or unfolded should not stick together to the extent where
tearing, or visually observed straining of the geomembrane, occurs. The upper
temperature limit is very specific to the particular type of geomembrane. A sheet
temperature of 50°C (122°F) is the upper limit that a geomembrane should be unrolled or
unfolded unless it is shown otherwise to the satisfaction of the CQA engineer.
2. Geomembranes which have torn or have been excessively deformed should be rejected
or shall be repaired per the CQA Document.
3. Geomembranes when unrolled or unfolded in cold weather should not crack craze or
distort in texture. A sheet temperature of 0°C (32°F) is the lower limit that a
geomembrane should be unrolled or unfolded unless it is shown otherwise to the
satisfaction of the CQA engineer.
138
-------
3.3.4.3 Temperature Effects - Expansion/Contraction
Polyethylene geomembranes expand when they are heated and contract when they are
cooled. Other types of geomembranes may slightly contract when heated. This expansion and
contraction must be considered when placing, seaming and backfilling geomembranes in the field.
Fig. 3.17 shows a wrinkled polyethylene liner which has expanded due to thermal warming from
the sun.
Figure 3.17 - HOPE Geomembrane Showing Sun Induced Wrinkles
Either the contract plans and specifications, or the CQA documents should cover the
expansion/contraction situation on the basis of site specific and geomembrane specific conditions.
Some items to consider include the following:
1. Sufficient slack shall be placed in the geomembrane to compensate for the coldest
temperatures envisioned so that no tensile stresses are generated in the geomembrane or
in its seams either during installation or subsequently after the geomembrane is covered.
2. The geomembrane shall have adequate slack such that it does not lift up off of the
subgrade or substrate material at any location within the facility, i.e., no "trampolining"
of the geomembrane shall be allowed to occur at any time.
139
-------
3. The geomembrane shall not have excessive slack to the point where creases fold over
upon themselves either during placement and seaming, or when the protective soil or
drainage materials are placed on the geomembrane.
4. Permanent (fold-over type) creases in the covered geomembrane should not be permitted
at any time.
5. The amount of slack to be added to the deployed and seamed geomembrane should be
carefully considered and calculated, taking into account the type of geomembrane and the
geomembrane s temperature during installation versus its final temperature in the
completed facility.
3.3.4.4 Spotting
™ii fv>!2en a ge,omem^ane roll or panel is deployed it is generally required that some shifting
will be necessary before field seaming begins. This is called "spotting" by many installers.
Some items for a specification or CQA document should include the following:
1. Spotting of deployed geomembranes should be done with no disturbance to the soil
subgrade or geosynthetic materials upon which they are placed.
2' soil 'sot? ShdeUSld be d°ne Wkh a minimum amount of dragging of the geomembrane on
3. Temporary tack welding (usually with a hand held hot air gun) of all types of
thermoplastic geomembranes should be allowed at the installers discretion.
4. When temporary tack welds of geomembranes are utilized, the welds should not
deprive?' e pnmary seaming method, or with the ability to perform subsequent
3.3.4.5 Wind Considerations
q 1 a i51ind dama§e ,to geomembranes, unfortunately, is not an uncommon occurrence, see Fig
cA™L j^^y Deployed geomembranes have been uplifted by wind and have been damaged. In
refen-ed S ?? ^nT^f havf/Ven bcen1tom out of anchor «™ch™- ™* « sometimes
referred to as blow-out by field personnel. Generally, but not always the unseamed
geomembrane rolls or panels acting individually are most vulnerable to wind uplift and damage
'"f Contract P1^8 and specification, or at least the CQA documents, must be very specific
S ?"!? reSardmg geomembranes that have been damaged due to shifting by wind Some
estions roiiow*
1 . Geomembrane rolls or panels which have been displaced by wind should be inspected
and approved by the CQA engineer before any further field operations commence.
2. Geomembrane rolls or panels which have been damaged (torn, punctured, or deformed
excessively and permanently) shall be rejected and/or repaired as directed in the contract
plans, specifications or CQA documents.
3. Permanent crease marks, or severely folded (crimped) locations, in geomembranes
140
-------
should not be permitted unless it can be shown that such distortions have no adverse
effect on the properties of the geomembrane. If this cannot be done, these areas should
be cut out and properly patched as per the contract documents and approved by the CQA
Engineer.
4. If patching of wind damaged geomembranes becomes excessive (to the limit set forth in
the specifications or CQA plan), the entire roll or panel should be rejected.
Figure 3.18 - Wind Damage to Deployed Geomembrane
3.4 Seaming and Joining
The field seaming of the deployed geomembrane rolls or panels is a critical aspect of their
successful functioning as a barrier to liquid (and sometimes vapor) flow. This section describes
the various seaming methods in current use, references a recently published EPA Technical
Guidance Document on seam fabrication techniques (EPA, 1991), and describes the concept and
importance of test strips (or trial seams).
3.4.1 Overview of Field Seaming Methods
The fundamental mechanism of seaming polymeric geomembrane sheets together is to
temporarily reorganize, i.e., melt, the polymer structure of the two surfaces to be joined in a
141
-------
controlled manner that, after the application of pressure and after the passage of a certain amount of
e^^S^lSheet^Q1^ b°n^ t0ugether' ™S reorganizationresults from £inpu tof
a'dS^^^
Qr>mCc Seaily> sffminS two gepmembrane sheets would result in no net loss of tensile strength
However6 X? S*? ** ±& 3°™^ SheetS T°uld perform as one sinSle geomembrane sheet
However, due to stress concentrations resulting from the seam geometry, current seaming
Sm?gth J°SS rf lative t0 ^ P"™' geomembrane she* Thl
8 a funCtl°n- ? ±Q type Of geomembrane and the seaming
, such as residual strength, geomembrane type, and seaminl
^ ^Signfr, W-hen applying the aPPr°Priate design fectors-of-safetf
function and facility performance.
lr be n^ted ***** ^^^ cafl be the location of the lowest tensile strength in a
r!f ' Designuers ^ Mspectora should be aware of the importance of seeking only
£ geomembrane seams The minimum seam tensile strengths (as determined by
fi r ° S g601"6^1168 mu<" be predetermined by laboratory testing, knowledge of past
nrin, p,a^ tff' manPfacturers. literature, various trade journals or othlr standards setting
orgamzattons that maintain current information on seaming techniques and technologies.
are rivSfn T?H?? ? T?ng &t ?e tim.e <£ ^e printing of this docu^nt and discussed herein
are given in Table 3.2 and shown schematically in Fig. 3.19.
Table 3.2. Fundamental Methods Of Joining Polymeric Geomembranes
Thermal Processes Chemical Processes
EaniStao; Chemical:
"Flllet • Chemical Fusion
"Flat • Bodied Chemical Fusion
Elision: Adhesive:
*Hot WedSe • Chemical Adhesive
•Hot Air -Contact Adhesive
H ^P ° th.erm°Plastlc geomembranes that will be discussed in this
rhnn I ™ gfTral °ateg,0nff °^ Seaming methodS extrusion welding thermal fusion or
melt bonding, chemical fiision and adhesive seaming. Each will be explained along with their
specific variations so as to give an overview of field seaming technology.
142
-------
Fillet - Type
Flat - Type
(a) Extrusion Seams
T
Dual Hot Wedge
(Single Track is Also Possible)
Single Hot Air
(Dual Track is Also Possible)
(b) Fusion Seams
Chemical
Bodied Chemical
(c) Chemical Seams
Chemical Adhesive
Contact Adhesive
(d) Adhesive Seams
Figure 3.19 - Various Methods Available to Fabricate Geomembrane Seams
143
-------
Extrusion welding is presently used exclusively on geomembranes made from
polyethylene. A ribbon of molten polymer is extruded over the edge of, or in between, the two
surfaces to be joined. The molten extrudate causes the surfaces of the sheets to become hot and
melt, after which the entire mass cools and bonds together. The technique is called extrusion fillet
seaming when the extrudate is placed over the leading edge of the seam, and is called extrusion flat
seaming when the extrudate is placed between the two sheets to be joined. It should be noted that
extrusion fillet seaming is essentially the only practical method for seaming polyethylene
geomembrane patches, for seaming in poorly accessible areas such as sump bottoms and around
pipes and for seaming of extremely short seam lengths. Temperature and seaming rate both play
important roles in obtaining an acceptable bond; excessive melting weakens the geomembrane and
inadequate melting results in poor extrudate flow across the seam interface and low seam strength
Ine polymer used for the extrudate is also very important and should generally be the same
polyethylene compound used to make the geomembrane. The designer should specify acceptable
extrusion compounds and how to evaluate them in the specifications and CQA documents.
There are two thermal fusion or melt-bonding methods that can be used on all thermoplastic
geomembranes. In both of them, portions of the opposing surfaces are truly melted This being
the case, temperature, pressure, and seaming rate all play important roles in that excessive melting
weakens the geomembrane and inadequate melting results in low seam strength. The hot wedge
or hot shoe, method consists of an electrically heated resistance element in the shape of a wedge
that travels between the two sheets to be seamed. As it melts the surface of the two sheets being
seamed, a shear flow occurs across the upper and lower surfaces of the wedge. Roller pressure is
applied as the two sheets converge at the tip of the wedge to form the final seam. Hot wedge units
are controllable as far as temperature, amount of pressure applied and travel rate A standard hot
wedge creates a single uniform width seam, while a dual hot wedge (or "split" wedge) forms two
parallel seams with a uniform unbonded space between them. This space can be used to evaluate
seam quality and continuity of the seam by pressurizing the unbonded space with air and
monitoring any drop in pressure that may signify a leak in the seam.
The hot air method makes use of a device consisting of a resistance heater, a blower, and
temperature controls to force hot air between two sheets to melt the opposing surfaces
Immediately following the melting of the surfaces, pressure is applied to the seamed area to bond
the two sheets. As with the hot wedge method, both single and dual seams can be produced In
selected situations, this technique may also be used to temporarily "tack" weld two sheets together
until the final seam or weld is made and accepted.
Regarding the chemical fusion seam types; chemical fusion seams make use of a liquid
chemical applied between the two geomembrane sheets to be joined. After a few seconds required
to solten the surface, pressure is applied to make complete contact and bond the sheets together
As with any of the chemical seaming processes to be described, the two adjacent materials to be
bonded are transformed into a viscous phase. Care must be used to see that the proper amount of
chemical is applied m order to achieve the desired results. Bodied chemical fusion seams are
similar to chemical fusion seams except that 1% to 20% of the parent lining resin or compound is
dissolved m the chemical and then is used to make the seam. The purpose of adding the resin or
compound is to increase the viscosity of the liquid for slope work and/or adjust the evaporation rate
or the chemical. This viscous liquid is applied between the two opposing surfaces to be bonded
Alter a few seconds, pressure is applied to make complete contact. Chemical adhesive seams make
use ol a dissolved bonding agent (an adherent) in the chemical or bodied chemical which is left
alter the seamhas been completed and cured. The adherent thus becomes an additional element in
me system. Contact adhesive* are applied to both mating surfaces. After reaching the proper
degree of tackiness, the two sheets are placed on top of one another, followed by application of
roller pressure. The adhesive forms the bond and is an additional element in the system.
144
-------
Other emerging seaming methods use ultrasonic, electrical conduction and magnetic
induction energy sources. Since these methods are in the developmental stage, they will not be
described further in this document. See EPA (1991) for further details.
In order to gain an overview as to which seaming methods are used for the various
thermoplastic geomembranes described in this document, Table 3.3 is offered. It is generalized,
but it is used to introduce the primary seaming methods versus the type of geomembrane that is
customarily seamed by that method.
Table 3.3 Possible Field Seaming Methods for Various Geomembranes Listed in this Manual
Type of Seaming Type of Geomembrane
Method
HOPE VLDPE Other PE PVC CSPE-R Other Flexible
extrusion
(fillet and flat)
thermal fusion
(hot wedge and
hot air)
chemical
(chemical and
bodied chemical)
adhesive
(chemical and
contact)
A
A
n/a
n/a
A
A
n/a
n/a
A n/a n/a
A A A
n/a A A
n/a A A
A
A
A
A
Note: A = method is applicable
n/a = method is "not applicable"
3.4.2 Details of Field Seaming Methods
Full details of field seaming methods for the edges and ends of geomembrane rolls or
panels has recently been described in EPA Technical Guidance Document, EPA/530/SW-91/051,
entitled: "Inspection Techniques for the Fabrication of Geomembrane Seams". In this document
(EPA, 1991) are separate chapters devoted to the following field seaming methods.
• extrusion fillet seams
145
-------
• extrusion flat seams
• hot wedge seams
• hot air seams
• chemical and bodied chemical fused seams
• chemical adhesive seams
There is also a section on emerging technologies for geomembrane seaming. The interested reader
should consult this document for details regarding all of these seaming methods.
Whenever the plans and specifications are not written around a particular seaming method
the actual method which is used becomes a matter of choice for the installation contractor. As seen
in Table 3.3, there are a number of available choices for each geomembrane type Furthermore
even when the installation contractor selects the particular seaming method to be used, its specific
details are rarely stipulated even in the specification or CQA documents. This is to give the
installation contractor complete latitude in selecting seaming temperatures, travel rates, mechanical
roller pressures, chemical type, tack time, hand rolling pressure, etc. The role of the plans
specifications and CQA documents is to adequately provide for destructive tests (on test strips and
on production seams) and nondestructive tests (on production seams) to assure that the seams are
fabricated to the highest quality and uniformity and are in compliance with the project's documents.
This is not to say that the specification never influences the type of seaming method. For
example if the specifications call for a nondestructive constant air pressure test to be conducted
the installation contractor must use a thermal fusion technique like the dual hot wedge or dual hot
air methods since they are the only methods that can produce such a seam.
3.4.3 Test Strips and Trial Seams
T^^te£nd ^ seams> also called qualifying seams, are considered to be an important
aspect of CQC/CQA procedures. They are meant to serve as a prequalifying experience for
personnel, equipment and procedures for making seams on the identical geomembrane material
under the same climatic conditions as the actual field production seams will be made The test
strips are usually made on two narrow pieces of excess geomembrane varying in length between
1.0 to 3.0 m (3 to 10 ft.), see Fig. 3.20. The test strips should be made in sufficient lengths
preferably as a single continuous seam, for all required testing purposes.
The goal of these test strips is to reproduce aJl aspects of the actual production field seaming
activities intended to be performed in the immediately upcoming work session so as to determine
equipment and operator proficiency. Ideally, test strips can be used to estimate the quality of the
production seams while minimizing damage to the installed geomembrane through destructive
mechanical testing. Test strips are typically made every 4 hours (for example, at the beginning of
the work shift and after the lunch break). They are also made whenever personnel or equipment
are changed and when climatic conditions reflect wide changes in geomembrane temperature or
when other conditions occur that could affect seam quality. These details should be stipulated in
the contract specifications or CQA documents.
f i uTheudestructive testinS of the test strips should be done as soon as the installation contractor
leels that the strength requirements of the contract specification or CQA documents can be met
inus it behooves the contractor to have all aspects of the test strip seam fabrication in complete
146
-------
working order just as would be done in the case of fabricating production field seams. For
extrusion and thermal fusion seams, destructive testing can be done as soon as the seam cools. For
chemical fusion and adhesive seams this could take several days and the use of a field oven to
accelerate the curing of the seam is advisable.
Figure 3.20 - Fabrication of a Geomembrane Test Strip
From two to six test specimens are cut from the test strip using a 25 mm (1.0 in. wide die).
They are selected at random by the CQA inspector. The specimens are then tested in both peel and
shear using a field tensiometer, see Fig. 3.21. (Generally peel tests are more informative in
assessing the quality of the seam). If any of the test specimens fail, a new test strip is fabricated.
If additional specimens fail, the seaming apparatus and seamer should not be accepted and should
not be used for seaming until the deficiencies are corrected and successful trial welds are achieved.
The CQA inspector should observe all trial seam procedures and tests. If the specimens pass,
seaming operations can move directly to production seams in the field. Pass/fail criteria for
destructive seam tests will be described in Section 3.5.
147
-------
Figure 3.21 - Photograph of a Field Tensiometer Performing a Geomembrane Seam Test
The flow chart illustrated in Fig. 3.22 gives an idea of the various decisions that can be
reached depending upon the outcome of destructive tests on test strip specimens. Here it is seen
that failed test strips are linked to an increased frequency of destructive tests to be taken on
production field seams made during the time interval between making the test strip and its testing.
Furthermore, it is seen that there are only two chances at making adequate test strips before
production field seaming is stopped and repairs are initiated. These details should be covered in
either the project specification or the CQA documents.
Some specification or CQA document items regarding the fabrication of geomembrane seam
test strips include the following:
1. The frequency of making test strips should be clearly stated. Typically this is at the
beginning of the day, after the noon break and whenever changed conditions are
encountered, e.g., changes in weather, equipment, personnel.
2. The CQA Engineer should have the option of requesting test strips of any field seaming
crew or device at any time.
148
-------
Make Test Strip 1
Make Production
Field Seams
Yes
No
Make Test Strip 2
Take Destructive Samples
From Production Field
Seams
Increase Frequency of
Destructive Sampling
L
Continue Production
Field Seaming
Halt Production Field
Seaming and Repair per
CQA/CQC Documents to
Point of Previous
Acceptance with
Approved Seaming
Crew and/or Equipment*
* Note: Seaming Crew Failing to
Prepare Acceptable Test Strips
May Require Retraining in
Accordance with CQC/CQA
Documents
Figure 3.22 - Test Strip Process Flow Chart
3. The procedure for sampling and evaluating the field test strip samples should be clearly
outlined, i.e., the number of peel and shear test specimens to be cut and tested from the
test strip sample, the rate of testing and what the required strength values are in these
two different modes of testing.
4. The fabrication of the field test strip and testing of test specimens should be observed by
the CQA personnel.
149
-------
5. The time for testing after the test strip is fabricated varies between seam types. For
extrusion and fusion fabricated seams, the testing can commence immediately after the
polymer cools to ambient temperature. For chemical fusion and adhesive fabricated
seams, the testing must wait until adequate curing of the seam occurs. This can take as
long as 1 to 7 days. During this time all production seaming must be tracked and
documented.
6. Accelerated oven curing of chemical and adhesive fabricated seams is acceptable so as to
hasten the curing process and obtain test results as soon as possible. GRI Test Method
GM-7 can be used for this purpose.
7. The required inspection protocol and implications of failed test specimens from the test
strips must be clearly stated. The protocol outlined in Fig. 3.22 is suggested.
8. Field test strips are usually discarded after the destructive test specimens are removed
and tested. If this is not the case, it should be clearly indicated who receives the test
strip samples and what should be the utilization (if any) of these samples.
3.5 Destructive Test Methods for Seams
The major reason that plans and specifications do not have to be specific about the type of
seaming methods and their particular details is that geomembrane seams can be readily evaluated
for their quality by taking samples and destructively testing them either at the job site or in a timely
manner at a testing laboratory thereafter.
3.5.1 Overview
By destructively testing geomembrane seams it is meant to actually cut out (i.e., to sample)
and remove a portion of the completed production seam, and then to further cut the sample into
appropriately sized test specimens. These specimens are then tested according to a specified
procedure to failure or to yield depending upon the type of geomembrane.
A possible procedure is to select the sampling location and cut two closely spaced 25 mm
(1.0 in.) wide test specimens from the seam. The distance between these two test specimens is
defined later. The individual specimens are then tested in a peel mode using a field tensiometer
(recall Fig. 3.21). If the results are acceptable, the complete seam between the two field test
specimens is removed and properly identified and distributed. If either test specimen fails, two
new locations on either side of the failed specimen(s) are selected until acceptable seams are
located. The seam distance between acceptable seams is usually repaired by cap-stripping but other
techniques are also possible. The exact procedure must be stipulated in the specifications or CQA
document.
The length dimension of the field seam sample between the two test specimens just
described varies according to whatever is stipulated in the plans and specifications, or in
accordance with the CQA documents. Some common options are to sample the seam for a distance
of either 36 cm (14 in.), 71 cm (28 in.) or 106 cm (42 in.) along its length. Since the usual
destructive seam tests are either shear or peel tests and both types are 25 mm (1.0 in.) wide test
specimens, this allows for approximately 10, 20 or 30 tests (half shear and half peel) to be
conducted on the respective lengths cited above. The sample width perpendicular to the seam is
usually 30 cm (12 in.) with the seam being centrally located within this dimension.
150
-------
The options of seam sample length between the two peel test specimens mentioned above
that are seen in various plans, specifications, and CQA documents, are as follows:
• A 36 cm (14 in.) sample is taken from the seam and cut into 5 shear and 5 peel
specimens. The tests are conducted in the field or at a remote laboratory by, or under the
direction of, the responsible CQA organization.
• A 71 cm (28 in.) long sample is taken from the seam and cut in half. One half is further
cut into 5 shear and 5 peel test specimens which are tested in the field or at a remote
laboratory by the CQC organization (usually the installation contractor). The other half is
sent to a remote laboratory for testing by the CQA organization who also does 5 shear
and 5 peel tests. Alternatively, sometimes only the CQA organization does the testing
and the second half of the sample is left intact and archived by the owner/operator.
• A 106 cm (42 in.) long sample is taken from the seam and cut into three individual 36
cm (14 in.) samples. Individual samples go to the CQC organization, the CQA
organization and the owner/operator. The CQC and CQA organizations each cut their
respective samples into 5 shear and 5 peel test specimens and conduct the appropriate
tests immediately. The remaining sample is archived by the owner/operator.
Whatever is the strategy for taking samples from the production seams for destructive
testing it must be clearly outlined in the contract plans and specifications and further defined and/or
corroborated in the CQA documents.
Obviously, the hole created in the production seam from which the test sample was
originally taken must be patched in an appropriate manner. See Fig. 3.23 for such a patched
sampling location. Recognize that the seams of such patches are themselves candidates for field
sampling and testing. If this is done, one would have the end result of patch on a patch, which is a
rather unsightly and undesirable condition.
3.5.2 Sampling Strategies
The sampling of production seams of installed geomembranes represents a dilemma of
major proportions. Too few samples results in a poor statistical representation of the strength of
the seam, and too many samples requires an additional cost and a risk of having the necessary
repair patches being problems in themselves. Unfortunately, there is no clear strategy for all cases,
but the following are some of the choices that one has in formulating a specification or CQA plan.
Note also that in selecting a sampling strategy the sampling frequency is tied directly into
the performance of the test strips described in Section 3.4.3. If the test strips fail during the time
that production seaming is ongoing, the frequency of destructive sampling and testing must be
increased. The following strategies, however, are for situations where geomembrane seam test
strips are being made in an acceptable manner.
3.5.2.1 Fixed Increment Sampling
By far the most commonly used sampling strategy is the "fixed increment sampling"
method. In this method, a seam sample is taken at fixed increments along the total length of the
seams. Increments usually range from 75 to 225 m (250 to 750 ft) with a commonly specified
value being one destructive test sample every 150 m (500 ft). Note that this value can be applied
either directly to the record drawings during layout of the seams, to each seaming crew as they
progress during the work period, or to each individual seaming device. Once the increment is
151
-------
decided upon, it should be held regardless of the location upon' which it falls, e.g., along side
slopes, in sumps, etc. Of course, if the CQA documents allow otherwise, exceptions such as
avoiding sumps, connections, protrusions, etc. can be made.
Figure 3.23 - Completed Patch on a Geomembrane Seam Which had Previously Been Sampled
for Destructive Tests
3.5.2.2 Randomly Selected Sampling
In random selection of destructive seam sample locations it is first necessary to preselect a
preliminary estimate of the total number of samples to be taken. This is done by taking the total
seam length of the facility and dividing it by an arbitrary interval, e.g., 150 m (500 ft), to obtain
the total number of samples that are required. Two choices to define the actual sampling locations
152
-------
are now available: "stratified" random sampling, or "strict" random sampling. The stratified
method takes each pre-selected interval (e.g., a 150 m (500 ft) length) and randomly selects a
single sample location within this interval. Thus with stratified random sampling one has location
variability within a fixed increment (unlike fixed frequency sampling which is always at the exact
end of the increment). The strict method uses the total seam length of the facility (or cell) and
randomly selects sample locations throughout the facility up to the desired number of samples.
Thus with strict random sampling a group of samples may be taken in close proximity to one
another, which necessarily leaves other areas with sparse sampling.
There are various ways of randomly selecting the specific location within an interval, e.g.,
in a specific region of great concern, or within the total project seam length. These are as follows:
• Use a random number generator from statistical tables to predetermine the sampling
locations within each interval or for the entire project.
• Use a programmable pocket calculator with a random number generator program to
select the sampling location in the field for each interval or for the entire project.
• Use a random number obtained by simply multiplying two large numbers together to
form an 8-digit result. A pocket calculator with an adequate register will be necessary.
The center two digits in such a procedure are quite randomly distributed and can be used
to obtain the sampling location. For example, multiplication of the following two
numbers "4567" by 4567" gives 20857489 where the central two digits, i.e., the "57",
are used to select the location within the designated sampling interval. If this interval
were 500 ft., the sampling location within it would be at 0.57 x 500 = 285 ft. from the
beginning of the interval. The next location of the sample would require a new
calculation resulting in a different central two-digit number somewhere within the next
500 ft. sampling interval and would be located in a similar fashion.
3.5.2.3 Other Sampling Strategies
There are two other sampling strategies which might be selected in determining how many
destructive seam samples should be taken. Both are variable strategies in that repeated acceptable
seam tests are rewarded by requiring fewer samples and repeated failures are penalized by
requiring more frequent samples. These two strategies are called the "method of attributes" and the
use of "control charts". Both set upper and lower bounds which require either fewer or more
frequent testing than the initially prescribed sampling frequency. Each of these methods are
described fully in Richardson (1992).
Whatever the sampling strategy used, it should never limit or prohibit the ability to select a
destructive seam sample from a suspect area. This should ultimately be an option left to the CQA
engineer.
3.5.3 Shear Testing of Geomembrane Seams
Shear testing of specimens taken from field fabricated geomembrane seams represents a
reasonably simulated performance test. The possible exception is that a normal stress is not
applied to the surfaces of the test specimen thus it is an "unconfined" tension test. A slight rotation
may be induced during tensioning of the specimen, making the actual test results tend toward
conservative values. The configuration of a shear test in a tension testing machine is shown in Fig.
3.24.
153
-------
Figure 3.24 - Shear Test of a Geomembrane Seam Evaluated in a CQC/CQA Laboratory
Environment
Commonly recommended shear tests for HOPE, PVC, CSPE-R and EIA-R seams, along
with the methods of testing the unseamed sheet material in tension, are given in Table 3.4. The
VLDPE data presented was included in a way so as to parallel the HDPE testing protocol except for
the strain rate values which are faster since breaking values, rather than yield values are required.
There is no pronounced yield value when tensile testing VLDPE geomembranes.
154
-------
Table 3.4 Recommended Test Method Details for Geomembrane Seams in Shear and in Peel and for Unseamed Sheet
Type of Test
Shear Test on Seams
ASTM Test Method
Specimen Shape
Specimen Width (in.)
Specimen Length (in.)
Gage Length (in.)
Strain Rate (ipm)
Strength (psi) or (ppi)
Peel Test on Seams
ASTM Test Method
Specimen Shape
Specimen Width (in.)
Specimen Length (in.)
Gage Length (in.)
Strain Rate (ipm)
Strength (psi) or (ppi)
Tensile Test on Sheet
ASTM Test Method
Specimen Shape
Specimen Width (in.)
Specimen Length (in.)
Gage Length (in.)
Strain Rate (ipm)
Strength (psi) or (Ib)
Strain (in./in.)
Modulus (psi)
where n/a = not applicable
t = geomembrane thickness
HDPE
D4437
Strip
1.00
6.00 + seam
4.00 + seam
2.0
Force/(1.00xt)
D4437
Strip
1.00
4.00
n/a
2.0
Force/(1.00xt)
D638
Dumbbell
0.25
4.50
1.30
2.0
Force/(0.25xt)
Elong./1.30
From Graph
VLDPE
D4437
Strip
1.00
6.00 + seam
4.00 + seam
20
Force/(1.00xt)
D4437
Strip
1.00
4.00
n/a
20
Force/(1.00xt)
D638
Dumbbell
0.25
4.50
1.30
20
Force/(0.25xt)
Elong./1.30
From Graph
PVC
D3083
Strip
1.00
6.00 + seam
4.00 + seam
20
Force/(1.00xt)
•
D413
Strip
1.00
4.00
n/a
2.0
Force/1.00
D882
Strip
1.00
6.00
2.00
20
Force/(1.00xt)
Elong./2.00
From Graph
CSPE-R
D751
Grab
4.00 (1.00 grab)
9.00 + seam
6.00 + seam
12
Force
D413
Strip
1.00
4.00
n/a
2.0
Force/1.00
D751
Grab
4.00 (1.00 Grab)
6.00
3.00
12
Force
Elong./3.00
n/a
psi = pounds/square inch of specimen cross section
ppi = pounds/linear inch width of specimen
ipm = inches/minute
Force = maximum force attained at specimen failure (yield or break)
-------
Insofar as the shear testing of nonreinforced geomembrane seams (HDPE, VLDPE and
PVC), all use a 25 mm (1.0 in.) wide test specimen with the seam being centrally located within
the testing grips. For the reinforced geomembranes (CSPE-R and EIA-R) a "grab" test specimen
is used. In a grab tension test the specimen is 200 mm (4.0 in.) wide but is only gripped in the
central 25 mm (1.0 in.). The test specimen is tensipned, at its appropriate strain rate, until failure
occurs. If the seam delaminates (i.e., pulls apart in a seam separation mode), the seam fails in
what is called a "non-film tear bond", or non-FTB. In this case, it is rejected as a failed seam.
Details on various types of seam failures and on the interpretation of FTB are found in Haxo
(1988). Conversely, if the seam does not delaminate, but fails in the adjacent sheet material on
either side of the seam, it is an acceptable failure mode, i.e., called a "film tear bond", or FTB, and
the seam strength is then calculated.
The seam strength (for HDPE, VLDPE and PVC) is the maximum force attained divided by
either the original specimen width (resulting in units of force per unit width), or the original
specimen cross sectional area (resulting in units of stress). It is general procedure to use force per
unit width as it is an absolute strength value which can be readily compared to other test results. If
stress units are desired, one can use the nominal thickness of the geomembrane, or continuously
measure the actual thickness of each test specimen. This latter alternative requires considerable
time and effort and is generally not recommended. The procedure is slightly different for the
reinforced geomembranes (CSPE-R and EIA-R) which use a grab test method. Here the strength
is based on the maximum tensile force that can be mobilized and a stress value is not calculated.
The resulting value of seam shear strength is then compared to the required seam strength
(which is the usual case) or to the strength of the unseamed geomembrane sheet. If the latter, the
procedures for obtaining this value are listed in Table 3.4. In each case the test protocol for seam
and sheet are the same, except for HDPE and VLDPE. The sheet strength value for these
polyethylene geomembranes are based on a ASTM D-638 "dumbbell-shaped" specimens, although
the strength is calculated on the reduced section width. With all of these sheet tension tests, the
nominal thickness of the unseamed geomembrane sheet is used for the comparison value. If actual
thickness of the sheet is considered, the results will be reflected accordingly. Note, however, that
this will require a large amount of additional testing (to get average strength values) and is not a
recommended approach.
Knowing the seam shear strength and the unseamed sheet strength (ether by a specified
value or by testing), allows for a seam shear efficiency calculation to be made as follows:
T . .
•rj seam in shear ,ir»A\
Eshear = T (1°0)
unseamed sheet (11}
where
^shear = seam efficiency in shear (%)
Tseam = seam shear strength (force or stress units)
Tsneet = sheet tensile strength (force or stress units)
The contract plans, specifications or CQA documents should give the minimum allowable
seam shear strength efficiency. As a minimum, the guidance listed below can be used whereby
156
-------
percentages of seam shear efficiencies (or values) are listed:
HOPE = 95% of specified minimum yield strength
VLDPE = typically 12001b/in2
PVC = 80%
CSPE-R = 80% (for 3-ply reinforced)
EIA-R = 80%
Generally an additional requirement of a film tear bond, or FTB, will also be required in
addition to a minimum strength value. This means that the failure must be located in the sheet
material on either side of the seam and not within the seam itself. Thus the seam cannot
delaminate.
Lastly, the number of failures allowed per number of tests conducted should be addressed.
If sets of 5 test specimens are performed for each field sample, many specifications allow for one
failure out of the five tested. If the failure number is larger, then the plans, specifications or CQA
documents must be clear on the implications.
When a destructive seam test sample fails, many specifications and CQA documents require
two additional samples to be taken, one on each side of the original sample each spaced 3 m (10 ft)
from it. If either one of these samples fail, the iterative process of sampling every 3 m (10 ft) is
repeated until passing test results are observed. In this case the entire seam between the two
successful test samples must be questioned. For example, remedies for polyethylene
geomembranes are to cap strip the entire seam or if the seam is made with a thermal fusion method
(hot air or hot wedge) to extrude a fillet weld over the outer seam edge. When such repairs are
concluded the seams on the cap strip or extrusion fillet weld should be sampled and tested as just
described.
Note that elongation of the specimens during shear testing is usually not monitored
(although current testing trends are in this direction), the only value under consideration is the
maximum force that the seam can sustain. It should also be mentioned that the test is difficult to
perform on the inside of the tracks facing the air channel of a dual channel thermal fusion seam.
For small air channels the tab available for gripping will be considerably less than that required in
test methods as given in Table 3.4. Regarding the testing of the inside or outside tracks (away
from the air channel) of a dual channel thermal fusion seam, or even both tracks, the specification
or CQA document should be very specific.
3.5.4 Peel Testing of Geomembrane Seams
Peel testing of specimens taken from field fabricated geomembrane seams represent a
quality control type of index test. Such tests are not meant to simulate in-situ performance but are
very important indicators of the overall quality of the seam. The configuration of a peel test in a
tension testing machine is shown in Fig. 3.25.
The recommended peel tests for HDPE, PVC, CSPE-R and EIA-R seams, along with the
unseamed sheet material in tension are given in Table 3.4. The VLDPE data was included in a way
so as to parallel the HDPE testing protocol.
Insofar as the peel testing of geomembrane seams is concerned, it is seen that all of the
geomembranes listed have a 25 mm (1.0 in.) width test specimen. Furthermore, the specimen
.lengths and strain rate are also equal for all geomembrane types. The only difference is that HDPE
and VLDPE use the thickness of the geomembrane to calculate a tensile strength value in stress
157
-------
units, whereas PVC, CSPE-R and EIA-R calculate the tensile strength value in units of force per
unit width, i.e., in units of pounds per linear inch of seam.
Fig. 3.25 - Peel Test of a Geomembrane Seam Evaluated in a CQC/CQA Laboratory Environment
In a peel test the test specimen is tensioned, at its appropriate strain rate, until failure occurs.
If the seam delaminates (i.e., pulls apart in a seam separation mode), it is called a "non-film tear
bond or non-FTB", and is recorded accordingly. Conversely, if the seam does not delaminate, but
fails in the adjacent sheet material on either side of the seam it is called a "film tear bond or FTB"
and the seam strength is calculated. Details on various types of seam failures and on the
interpretation of FTB are found in Haxo (1988). The seam strength is the maximum force attained
divided by the specimen width (resulting in units of force per unit width), or by the specimen cross
sectional area (resulting in units of stress). The former procedure is the most common, i.e., peel
strengths are measured in force per unit width units. If stress units are desired the thickness of the
158
-------
geomembrane sheet must be included. The nominal sheet thickness is usually used. If the actual
sheet thickness is used, a large amount of thickness measurements will be required to obtain a
statistically reliable value. It is not a recommended procedure.
The resulting value of seam peel strength is then compared to a specified value (the usual
case) or to the strength of the unseamed geomembrane sheet. The testing procedures for obtaining
these values are listed in Table 3.4. It can be seen, however, that only with PVC is the same width
test specimen used for peel and sheet testing. For HOPE and VLDPE one is comparing a 1.0 in.
uniform width peel test with a dumbbell shaped specimen, while for CSPE-R and EIA-R one is
comparing a uniform width peel test with the strength from a grab shaped test specimen. If,
however, one does have a specified sheet strength value or a measured value, a seam peel strength
efficiency calculation can be made as follows:
unseamed sheet
where
= seam efficiency in peel (%)
= seam peel strength (force or stress units)
Tsheet = sheet tensile strength (force or stress units)
The contract plans, specifications or CQA documents should give the minimum allowable
seam peel strength efficiency. As a minimum, the guidance listed below can be used whereby
percentage peel efficiencies (or values) are listed as follows:
HDPE = 62% of specified minimum yield strength and FTB
VLDPE = typically 1000 Ib/in^
PVC = 10 Ib/in.
CSPE-R = 10 Ib/in. or FTB
EIA-R = 10 Ib/in.
Lastly, the number of failures allowed per number of tests conducted should be addressed. If sets
of 5 test specimens are performed for each field sample, many specifications allow for one failure
out of the five tested. If the failure number is larger, then the plans, specifications or CQA
documents must be clear on the implications.
When a destructive seam test sample fails, many specifications require an additional two
samples to be taken, one on each side of the original spaced 3 m (10 ft) from it. If either one of
these samples fail the iterative process of sampling every 3 m (10 ft) is repeated until successful
samples result. In this case, the entire seam between the last successful test samples must be
questioned. Remedies are to cap strip the entire seam or if the seam is HDPE or VLDPE made
with a thermal fusion method (hot air or hot wedge) to extrude a fillet weld over the outer seam
edge. When this is done the seams on the cap strip or extrusion fillet weld may be sampled and
tested as just described.
Note that neither elongation of the specimen nor peel separation, during the test is usually
monitored (although current testing trends are in this direction), the only value under consideration
is the maximum tensile force that the seam can sustain. It should also be mentioned that both
frontward and backward peel tests can be performed thereby challenging both sides of a seam. For
159
-------
dual channel seams, both insides of the tracks facing the air channel can be tested, but due to the
narrow width of most air channels the tab available for gripping will be considerably less than that
given in Table 3.4. Regarding the testing of the inside or outside tracks (away from the air
channel) of a dual channel seam, or even both tracks, the specification or CQA document should be
very specific.
3.5.5 General Specification Items
Regarding field sampling of geomembrane seams and their subsequent destructive testing, a
specification or CQA document should consider the following items.
1. CQA personnel should observe all production seam sample cutting.
2. All samples should be adequately numbered and marked with permanent identification.
3. All sample locations should be indicated on the geomembrane layout (and record)
drawings.
4. The reason for taking the sample should be indicated, e.g., statistical routine,
suspicious feature, change in sheet temperature, etc.
5. The sample dimensions should be given insofar as the length of sample and its width.
The seam will generally be located along the center of the length of the sample.
6. The distribution of various portions of the sample (if more than one) should be
specified.
7. The number of shear and peel tests to be conducted on each sample (field tests and
laboratory tests) should be specified.
8. The specifics of conducting the shear and peel tests should be specified, e.g., use of
actual sheet thickness, or of nominal sheet thickness. The following are suggested
ASTM test methods for each geomembrane type:
Geomembrane Seam Shear Test Seam Peel Test Sheet Test
HDPE D-4437 D-4437 D-638
VLDPE D-4437 D-4437 D-638
PVC D-3083 D-413 D-882
CSPE-R D-751 D-413 D-751
EIA-R D-751 D-751 D-751
9. The CQA personnel should witness all field tests and see that proper identification and
details accompany the test results. Details should be provided in the CQA documents.
Such details as follows are often required.
160
-------
• date and time
• ambient temperature
• identification of seaming unit, group or machine
• name of master seamer
• welding apparatus temperature and pressure, or chemical type and mixture
• pass or fail description
• a copy of the report should be attached to the remaining portion of the sample
10. The CQA personnel should verify that samples sent to the testing laboratory are
properly marked, packaged and shipped so as not to cause damage.
11. Results of the laboratory tests should come to the CQA Engineer in a stipulated time.
For extrusion and thermally bonded seams, verbal test results are sometimes required
with 24 to 72 hours after the laboratory receives the samples. For chemically bonded
seams, the time frame is longer and depends on whether or not accelerated heat curing
of the seams is required. In all cases, the CQA Engineer must inform the Owner's
representative of the results and make appropriate recommendations.
12. The procedures for seam remediation in the event of failed destructive tests should be
clear and unequivocal. Options usually are (a) to repair the entire seam between
acceptable sampling locations, or (b) to retest the seam on both sides in the vicinity of
the failed sample. If they are acceptable only this section of the seam is repaired. If
they are not, a wider spaced set of samples are taken and tested.
13. Repairs to locations where destructive samples were removed should be stipulated.
These repairs are specific to the type of geomembrane and to the seaming method.
Guidance in this regard is available in EPA (1991).
14. Each repair of a patched seam where a test sample had been removed should be
verified. This is usually done by an appropriate nondestructive test. If, however, the
sampling strategy selected calls for a destructive test to be made at the exact location of
a patch it should be accommodated. Thus the final situation will require a patch to be
placed on an earlier patch. If this (unsightly) detail is to be avoided, it should be stated
outright in the specifications or CQA document.
15. The time required to retain and store destructive test samples on the part of the CQC
and CQA organizations should be stipulated.
3.6 Nondestructive Test Methods for Seams
3.6.1 Overview
Although it is obviously important to conduct destructive tests on the fabricated seams, such
tests do not give adequate information on the continuity and completeness of the entire seam
between sampling locations. It does little good if one section of a seam meets the specification
requirements, only to have the section next to it missed completely by the field-seaming crew.
161
-------
Thus continuous methods of a nondestructive testing (NOT) nature will be discussed here. In each
of these methods the goal is to validate 100% of the seams or, at minimum, a major percentage of
them.
3.6.2 Currently Available Methods
The currently available NDT methods for evaluating the adequacy of geomembrane field
seams are listed in Table 3.5 in the order that they will be discussed.
The air lance method uses a jet of air at approximately 350 kPa (50 lb/in.2) pressure
coming through an orifice of 5 mm (3/16 in.) diameter. It is directed beneath the upper edge of the
overlapped seam and is held within 100 mm (4.0 in.) from the edge of the seamed area in order to
detect unbonded areas. When such an area is located, the air passes through the opening in the
seam causing an inflation and fluttering in the localized area. A distinct change in sound Imitted
can generally be heard. The method works best on relatively thin, less than 1.1 mm (45 mils)
flexible geomembranes, but works only if the defect is open at the front edge of the seam, where
the air jet is directed. It is essentially a geomembrane installer's method to be used in a
construction quality control (CQC) manner.
pe mechanical point stress or "pick" test uses a dull tool, such as a blunt screw-driver
under the top edge of a seam. With care, an individual can detect an unbonded area, which would
be easier to separate than a properly bonded area. It is a rapid test that obviously depends
completely on die care and sensitivity of the person doing it. Detectability is similar to that of using
the air lance, but both are very operator-dependent. This test is to be performed only by the
geomembrane installer as a CQC method. Design or inspection engineers should not use the pick
test but rather one or more of the techniques to be discussed later.
The pressurized dual seam method was mentioned earlier in connection with the dual hot
wedge or dual hot air thermal seaming methods. The air channel that results between the dual
bonded tracks is inflated using a hypodermic needle and pressurized to approximately 200 kPa (30
lb/in/ ). There is no limit as to the length of the seam that is tested. If the pressure drop is within
an allowable amount in the designated time period (usually 5 minutes), the seam is acceptable- if a
unacceptable drop occurs, a number of actions can be taken:
• The distance can be systematically halved until the leak is located.
• The section can be tested by some other leak detection method.
• An extrusion fillet weld can be placed over the entire edge.
• A cap strip can be seamed over the entire edge.
Details of the test can be found in GRI Test Method GM6. The test is an excellent one for long
straight-seam lengths. It is generally performed by the installation contractor, but usually with
CQA personnel viewing the procedure and documenting the results.
162
-------
Table 3.5 - Nondestructive Geomembrane Seam Testing Methods, Modified from Richardson and Koerner (1988)
Nondestructive
Test Method
1. air lance
2. mechanical
point (pick)
stress
3. dual seam
(positive
pressure)
4. vacuum
chamber
(negative
pressure)
5. electric wire
6. electric field
7. ultrasonic
pulse echo
8. ultrasonic
impedance
9. ultrasonic
shadow
Primary User
CQC CQA
yes
yes
yes
yes yes
yes yes
yes yes
yes
yes
yes
Cost of
Equipment
$200
nil
$200
$1000
$500
$20,000 ,
$5000
$7000
$5000
Speed of
Tests
fast
fast
fast
slow
fast
slow
moderate
moderate
moderate
General
Cost of Tests
low
nil
moderate
very high
nil
high
high
high
high
Comments
Type of
Result
yes-no
yes-no
yes-no
yes-no
yes-no
yes-no
yes-no
qualitative
qualitative
Recording
Method
manual
manual
manual
manual
manual
manual and
automatic
automatic
automatic
automatic
Operator
Dependency
high
very high
low
moderate
high
low
moderate
unknown
moderate
CT\
-------
The vacuum chamber (box) method uses a box up to 1.0 m (3 ft) long with a transparent
top that is placed over the seam; a vacuum of approximately 20 kPa (3 lb/in.2) is applied. When a
leak is encountered the soapy solution originally placed over the seam shows bubbles thereby
reducing the vacuum. This is due to air entering from beneath the geomembrane and passing
through the unbonded zone. The test is slow to perform (a 10 sec dwell time is currently
recommended) and is often difficult to make a vacuum-tight joint at the bottom of the box where it
passes over the seam edges. Due to upward deformations of the liner into the vacuum box, only
geomembrane thickness greater than 1.0 mm (40 mils) should be tested in this manner. For
thinner, more flexible geomembranes an open grid wire mesh can be used along the bottom of the
box to prevent uplift. It should also be noted that vacuum boxes are the most common form of
nondestructive test currently used by design engineers and CQA inspectors for polyethylene
geomembranes. It should be recognized that 100% of the field seams cannot be inspected by this
method. The test cannot cover portions of sumps, anchor trenches, and pipe penetrations with any
degree of assurance. The method is also very awkward to use on side slopes. The adequate
downward pressure required to make a good seal is difficult to mobilize since it is usually done by
standing on top of the box.
Electric sparking (not mentioned in Table 3.5) is a technique used to detect pinholes in
thermoplastic liners. The method uses a high-voltage (15 to 30 kV) current, and any leakage to
ground (through an opening or hole) results in sparking. The method is being investigated for
possible field use. The electric wire method places a copper or stainless steel wire between the
overlapped geomembrane region and actually embeds it into the completed seam. After seaming, a
charged probe of about 20,000 volts is connected to one end of the wire and slowly moved over
the length of the seam. A seam defect between the probe and the embedded wire results in an
audible alarm from the unit.
The electric field test utilizes a potential which is applied across the geomembrane by
placing a positive electrode in water within the geomembrane and a ground electrode in the
subgrade or in the sump of the leak detection system. A current will only flow between the
electrodes through a hole (leak) in the geomembrane. The potential gradients in the ponded water
are measured by "walking" the area with a previously calibrated probe. The operator walks along a
calibration grid layout and identifies where anomalies exist. Holes less than 1 mm diameter can be
identified. These locations can be rechecked after the survey is completed by other methods, such
as the vacuum box. In deep water, or for hazardous liquids, a remote probe can be dragged from
one side of the impoundment to the other across the surface of the geomembrane. On side slopes
that are not covered by water, a positively charged stream of water can be directed onto the surface
of the geomembrane. When the water stream encounters and penetrates a hole, contact with the
subgrade is made. At this point current flow is indicated, thus locating the hole. Pipe penetrations
through the geomembrane and soil cover that goes up the side slope and contacts the subgrade
reduce the sensitivity of the method.
The last group of nondestructive test methods noted in Table 3.5 can collectively be called
ultrasonic methods. A number of ultrasonic methods are available for seam testing and evaluation.
The ultrasonic pulse echo technique is basically a thickness measurement technique and is only for
use with nonreinforced geomembranes. Here a high-frequency pulse is sent into the upper
geomembrane and (in the case of good acoustic coupling and good contact between the upper and
lower sheets) reflects off of the bottom of the lower one. If, however, an unbonded area is
present, the reflection will occur at the unbonded interface. The use of two transducers, a pulse
generator, and a CRT monitor are required. It cannot be used for extrusion fillet seams, because of
their npnuniform thickness. The ultrasonic impedance plane method works on the principle of
acoustic impedance. A continuous wave of 160 to 185 kHz is sent through the seamed
geomembrane, and a characteristic dot pattern is displayed on a CRT screen. Calibration of the dot
164
-------
pattern is required to signify a good seam; otherwise, it is not. The method has potential for all
types of geomembranes but still needs additional developmental work. The ultrasonic shadow
method uses two roller transducers: one sends a signal into the upper geomembrane and the other
receives the signal from the lower geomembrane on the other side of the seam (Richardson and
Koerner, 1988). The technique can be used for all types of seams, even those in difficult
locations, such as around manholes, sumps, appurtenances, etc. It is best suited for
semicrystalline geomembranes, including HOPE, and will not work for scrim-reinforced liners.
3.6.3 Recommendations for Various Seam Types
The various NDT methods listed in Table 3.5 have certain uniqueness and applicability to
specific seam and geomembrane types. Thus a specification should only be framed around the
particular seam type and geomembrane type for which it has been developed. Table 3.6 gives
guidance in this regard. Even within Table 3.6, there are certain historical developments. For
example, the air lance method is used routinely on the flexible geomembranes seamed by chemical
methods, whereas the vacuum chamber method is used routinely on the relatively stiff HDPE
geomembranes. Also to be noted is that the dual seam can technically be used on all
geomembranes, but only when they are seamed by a dual track thermal fusion method, i.e., by hot
wedge or hot air seaming methods. Thus by requiring such a dual seam pressure test method one
mandates the type of seam which is to be used by the installation contractor.
Lastly, it should be mentioned that only three of the nine methods listed in Table 3.5 are
used routinely at this point in time. They are the air lance, dual seam and vacuum chamber
methods. The others are either uniquely used by the installation contractor (pick test and electric
wire), or are in the research and development stage (electric current and the various ultrasonic test
methods).
3.6.4 General Specification Items
Regarding field evaluation of geomembrane seams and their nondestructive testing, a
specification or CQA document should consider the following items:
1. The purpose of nondestructive testing should be clearly stated. For example,
nondestructive testing is meant to verify the continuity of field seams and not to
quantify seam strength.
2. Generally nondestructive testing is conducted as the seaming work progresses or as
soon as a suitable length of seam is available.
3. Generally nondestructive testing of some type is required for 100% of the field seams.
For geomembranes supplied in factory fabricated panels, the factory seams may, or
may not, be specified to be nondestructively tested in the field. This decision depends
on the degree of MQC (and MQA) required on factory fabricated seams.
4. The specification should recognize that the same type of nondestructive test cannot be
used in every location. For example, in sumps and at pipe penetrations the dual air
channel and vacuum box methods may not be usable.
5. It must be recognized that there are no current ASTM Standards on any of the NDT
methods presented in Table 3.5 although many are in progress. Thus referencing to
such consensus documents is not possible. For temporary guidance, there is a GRI
Standard available for dual seam air pressure test method, GRI GM-6.
165
-------
6. CQA personnel should observe all nondestructive testing procedures.
7. The location, data, test number, name of test person and outcome of tests must be
recorded.
8. The Owner's representative should be informed of any deficiencies.
9. The method of repair of deficiencies found by nondestructive testing should be clearly
outlined in the specifications or CQA documents, as should the retesting procedure.
Table 3.6 Applicability Of Various Nondestructive Test Methods To Different Seam Tvoes
And Geomembrane Types
NDT Method
Seam Types*
Geomembrane Types
1. air lance
2. mechanical point stress
3. dual seam
4. vacuum chamber
5. electric wire
6. electric current
7. ultrasonic pulse echo
8. ultrasonic impedance
9. ultrasonic shadow
C, BC, Chem A, Cont. A
all
HW,HA
all
all
all
HW.HA
C, BC,
Chem. A, Cont. A
HW.HA
C, BC,
Chem. A, Cont. A
E Fil.. E Fit.. HW. HA
all except HDPE
all
all
all
all
all
HDPE, VLDPE, PVC
HDPE, VLDPE, PVC
HDPE, VLDPE
*E Fil.
EFlt.
HW
HA
C
BC
Chem. A
Cont. A
= extrusion fillet
= extrusion flat
= hot wedge
= hot air
= chemical
= bodied chemical
= chemical adhesive
= contact adhesive
166
-------
3.7 Protection and Backfilling
The field deployed and seamed geomembrane must be backfilled with soil or covered with a
subsequent layer of geosynthetics in a timely manner after its acceptance by the CQA personnel. If
the covering layer is soil, it will generally be a drainage material like sand or gravel depending
upon the required permeability of the overlying layer. Depending upon the particle size, hardness
and angularity of this soil, a geotextile or other type of protection layer may be necessary. If the
covering layer is a geosynthetic, it will generally be a geonet or geocomposite drain, which is
usually placed directly upon the geomembrane. This is obviously a critical step since
geomembranes are relatively thin materials with puncture and tear strengths of finite proportions.
Specifications should be very clear and unequivocal regarding this final step in the installation
survivability of geomembranes.
3.7.1 Soil Backfilling of Geomembranes
There are at least three important considerations concerning soil backfilling of
geomembranes: type of soil backfill material, type of placement equipment and considerations of
slack in the geomembrane.
Concerning the type of soil backfilling material; its particle size characteristics, hardness and
angularity are important with regard to the puncture and tear resistance of the geomembrane. In
general, the maximum soil particle size is very important, with additional concerns over poorly
graded soils, increased angularity and increased hardness being of significance. Past research on
puncture resistance of geomembranes has shown that HDPE and CSPE-R geomembranes are more
sensitive to puncture than are VLDPE and PVC geomembranes for conventional thicknesses of the
respective types of geomembranes. Using truncated cones in laboratory tests to simulate the
puncturing phenomenon (Hullings and Koerner, 1991), the critical cone height values which were
obtained are listed in Table 3.7. It should be cautioned, however, that these values are not based
on actual soil subgrades, nor on geostatic type stresses. The values are meant to give relative
performance between the different geomembrane types.
Table 3.7. Critical Cone Heights For Selected Geomembranes In Simulated Laboratory
Puncture Studies (Richardson and Koerner, 1988)
Geomembrane Type Geomembrane Thickness Critical Cone Height
mm mil mm inch
HDPE
VLDPE
PVC
CSPE-R
1.5
1.0
0.5
0.9
60
40
20
36
12
89
70
15
0.50
3.50
2.75
0.60
Although the truncated cone hydrostatic test is an extremely challenging index-type test, the data of
Table 3.7 does not reflect creep and/or stress relaxation of the geomembrane. In reviewing
numerous CQA documents it appears that the maximum backfill particle size for use with HDPE
and CSPE-R geomembranes should not exceed 12-25 mm (0.5-1.0 in.). VLDPE and PVC
geomembranes appear to be able to accommodate larger soil backfill particle sizes. If the soil
167
-------
particle size must exceed the approximate limits given (e.g., for reasons of providing high
permeability in a drainage layer), then a protection material must be placed on top of the
geomembrane and beneath the soil. Geotextiles, as well as other protection materials, have been
used in this regard. New materials, e.g., recycled fiber geotextiles and rubber matting, are being
evaluated. 6 5
Concerning the type of placement equipment, the initial lift height of the backfill soil is very
important. (Note that construction equipment should never be allowed to move directly on any
deployed geomembrane. This includes rubber tired vehicles such as automobiles and pickup
trucks but does not include light weight equipment like all-terrain vehicles (ATV's). The minimum
initial lift height should be determined for the type of placement equipment and soil under
consideration, however, 150 mm (6 in.) is usually considered to be a minimum. Between this
value and approximately 300 mm (12.0 in.), low ground pressure placement equipment should be
specified. Ground contact pressure equipment of less than 35 kPa (5.0 lb/in2) is recommended
For lift heights of greater than 300 mm (12.0 in.), proportionately heavier placement equipment
can be used.
Placement of soil backfilling should proceed from a stable working area adjacent to the
deployed geomembrane and gradually progress outward. Soil is never to be dropped from dump
trucks or front end loaders directly onto the geomembrane. The soil should be pushed forward in
an upward tumbling action so as not to impact directly on the geomembrane. It should be placed
by a bulldozer or front end loader, never by a motor grader which would necessarily have its front
wheels nding directly on the geomembrane. Sometimes "fingers" of backfill are pushed out over
the geomembrane with controlled amounts of slack between them. Figure 3.26 shows a sketch
aun «£?ot°graph of this type of soil covering placement. Backfill is then widened so as to connect
the fingers , with the controlled slack being induced into the geomembrane. This procedure is at
the discretion of the design engineer and depends on site specific materials and conditions.
If a predetermined amount of slack is to be placed in the geomembrane, the temperature of
the geomembrane itself during backfilling is important and should be contrasted against the
minimum service temperature that the geomembrane will eventually experience. This difference in
temperature, assuming the geomembrane temperature at the time of backfilling is higher than the
minimum service temperature, is multiplied by the distance between backfilling "fingers" and by
the coefficient of thermal expansion/ contraction of the particular geomembrane. Coefficients of
thermal expansion/contraction found in the literature are given in Table 3.8. Note, however that
the coefficient of expansion/contraction of the site specific geomembrane should be available for
such calculations.
While many geomembrane polymers fall in the same general range of coefficient of thermal
expansion/contraction (as seen in Table 3.8), it is the stiff and relatively thick geomembranes,
which are troublesome during backfilling. Here the slack accumulates in a wave which should not
be allowed to crest over on itself, lest a fold is trapped beneath the backfill. In such cases, the
fingers of backfilling must be relatively close together. If the situation becomes unwieldy due to
very high geomembrane temperature, the backfilling should temporarily cease until the ambient
temperature decreases. This will have the effect of requiring less slack to be placed in the
geomembrane.
168
-------
Advancing Cover
Soil over
Exposed Geomembrane
Note: Arrows Indicate Advancement of
Cover Soil Over Geomembrane
Figure 3.26 - Advancing Primary Leachate Collection Gravel in "Fingers" Over the Deployed
Geomembrane
169
-------
Table 3.8 - Coefficients Of Thermal Expansion/Contraction Of Various Nonreinforced
Geomembrane Polymers (Various References)*
Thermal linear expansivity x 10~5
Polymer Type perl°F
Polyethylene
high density 7_12 12-22
medium density 6_g 11-15
low density 5.7 9113
very low density 1M6 20-30
Polypropylene 3.5 5.9
Polyvinyl chloride
unplasticized 3_10 5_lg
plasticized 4.^4 -i_2e
* Values are approximate and change somewhat with the particular formulation and with the actual temperature range
over which the values are measured.
3.7.2 Geosynthetic Covering of Geomembranes
Various geosynthetic materials may be called upon to cover the deployed and seamed
geomembrane. Often a geotextile or a geonet will be the covering material. Sometimes, however,
it will be a geogrid (for cover soil reinforcement on slopes) or even a drainage geocomposite (again
on slopes to avoid instability of natural drainage soils). As with the previous discussion on soil
covering, no construction vehicles of any type should be allowed to move directly on the
geomembrane (or any other geosynthetic for that matter). Generators, low tire inflation ATV'S
and other seaming related equipment are allowed as long as they do not damage the geomembrane!
As a result, the movement of large rolls of geotextile or geonet becomes very labor intensive
Proper planning and sequencing of the operations is important for logistical control. The
geosynthetic materials are laid directly on the geomembrane with no bonding of any type to the
geomembrane being allowed. For example, thermally fusing of a geonet to a geomembrane should
not be permitted. Temperature compensation (as described earlier) should be added based on
material characteristics.
The geosynthetics placed above the geomembrane will either be overlapped (as with some
geotextiles), sewn (as with other geotextiles), connected with plastic ties (as with geonets)
mechanically joined with rods or bars (as with geogrids), or male/female joined (as with drainage
composites). These details will be described in Chapter 6 on geosynthetic materials other than
geomembranes.
170
-------
3.7.3 General Specification Items
The specification or CQA document for backfilling should be written around the concept
that the geomembrane must be protected against damage by the overlying material. Since soil,
usually sand or gravel, is the most common backfilling material, the items that follow should be
considered.
1. The temperature during soil backfilling should be considered. Expansion, contraction,
puncture, tear and other properties vary in accordance with the geomembrane
temperature.
2. In general, backfilling in warm climates or during summer months should be
performed at the coolest part of the day.
3. In extreme cases of excessively high temperatures, backfilling may be required during
non-typical work hours, e.g., sunrise to 10:00 AM or 5:00 PM to sunset.
4. If soil backfilling is to be done between sunset and sunrise, i.e., at night, the work
area should be suitably lit for safety, constructability and inspection considerations.
5. If soil backfilling is to be done at night, excessive equipment noise may not be
tolerated by people in the local neighborhood. This is an important and obviously site
specific condition which should be properly addressed.
6. When a geotextile or other protection layer is to be placed above the geomembrane it
should be done so according to the plans and specifications.
7. Soil placement equipment should never move, or drive, directly on the geomembrane.
8. Personnel or materials vehicles (automobiles, pickup trucks, etc.) should never drive
directly on the geomembrane.
9. The soil particle size characteristics should be stipulated as part of the design
requirements.
10. The minimum soil lift thickness should be stipulated in the design requirements.
Furthermore, the thickness should be clear as to whether it is loose or compacted
thickness.
11. The maximum ground contact pressure of the placement equipment should be
stipulated in the design requirements.
4
12. For areas regularly traversed by heavy equipment, e.g., the access route for loaded
dump trucks, a larger than usual fill height should be required.
13. The CQA personnel should be available at all times during backfilling of the
geomembrane. It is the last time when anyone will see the completely installed
material.
14. Documentation should include the soil type, lift thickness, total thickness, density and
moisture conditions (as appropriate).
171
-------
3.8 References
ASTM D-413, "Rubber Property-Adhesion to Flexible Substrate"
ASTM D-638, "Tensile Properties of Plastics"
ASTM D-751, "Test Methods for Coated Fabrics"
ASTM D-792, "Specific Gravity and Density of Plastics by Displacement"
ASTM D-882, 'Test Methods for Tensile Properties of Thin Plastic Sheeting"
ASTM D-1004, "Initial Tear Resistance of Plastic Film and Sheeting"
ASTM D-1238, "Flow Rates of Thermoplastics by Extrusion Plastometer"
ASTM D-1248, "Polyethylene Plastics and Extrusion Materials"
ASTM D-1505, "Density of Plastics by the Density-Gradient Technique"
ASTM D-1603, "Carbon Black in Olefin Plastics"
ASTM D-1765, "Classification System for Carbon Black Used in Rubber Products"
ASTM D-2663, "Rubber Compounds - Dispersion of Carbon Black"
ASTM D-3015, "Recommended Practice for Microscopical Examination of Pigment Dispersion in
Plastic Compounds"
ASTM D-3083, "Specification for Flexible Poly (Vinyl Chloride) Plastic Sheeting for Pond
Canal, and Reservoir Lining"
ASTM D-4437, "Practice for Determining the Integrity of Field Seams Used in Joining Flexible
Polymeric Sheet Geomembranes"
ASTM D-4545, "Practice for Determining the Integrity of Factory Seams Used in Joining
Manufactured Flexible Sheet Geomembranes"
ASTM D-4759, "Determining the Specification Conformance of Geosynthetics"
ASTM D-5046, "Specification for Fully Crosslinked Elastomeric Alloys"
ASTM D-5199, "Measuring Nominal Thickness of Geotextiles and Geomembranes"
ASTM D-5321 "Determining the Coefficient of Soil and Geosynthetic or Geosynthetic and
Geosynthetic Friction by the Direct Shear Method"
ASTM D-5397, "Notched Constant Tensile Load Test for Polyolefm Geomembranes"
172
-------
FTM Std. 101C, "Puncture Resistance and Elongation Test," Federal Test Method 2065," March
13, 1980.
GRIGM-6, "Pressurized Air Channel Test for Dual Seamed Geomembranes"
GRI GM-7, "Accelerated Curing of Geomembrane Test Strips Made by Chemical Fusion
Methods" ,
GRI GS-7, "Determining the Index Friction Properties of Geosynthetics"
Haxo, H. E., (1988), "Lining of Waste Containment and Other Impoundment Facilities,"
EPA/600/2-88/052, Washington, DC. ,
Hsuan, Y. and Koerner, R. M. (1992), "Stress Cracking Potential and Behavior of HOPE
Geomembranes," Final Report to U.S. EPA, Contract No. CR-815692.
Hullings, D. E. and Koerner, R. M. (1991), "Puncture Resistance of Geomembranes Using a
Truncated Cone Test," Proceedings, Geosynthetics '91, IFAI, pp. 273-286.
Richardson, G. N. and Koerner, R. M. (1988), "Geosynthetic Design Guidance for Hazardous
Waste Landfill Cells and Surface Impoundments," EPA/600/S 2-87/097.
Richardson, G. N. (1992), "Construction Quality Management for Remedial Action and Remedial
Design Waste Containment Systems," U.S. EPA, EPA/540/R-92/073, Washington, DC.
U. S. Environmental Protection Agency (1991) "Inspection Techniques for the Fabrication of
Geomembrane Field Seams," EPA Technical Guidance Document, EPA/530/SW-91/051.
173
-------
Chapter 4
Geosynthetic Clay Liners
4-1 Types and Composition of Geosvnthetic Clav Liners
..,.- As wi* most tvPes of manufactured products within a given category, there are sufficient
differences such that no two products are truly equal to one another. Geosynthetic clay liners
(GCLs) are no exception. Yet, there are a sufficient number of common characteristics such that
the current commercially available products deserve a separate category and a separate treatment in
this manual. GCLs can be defined as follows:
"Geosynthetic clay liners (GCLs) are factory manufactured, hydraulic barriers
typically consisting of bentonite clay or other very low permeability clay
materials, supported by geotextiles and/or geomembranes which are held
together by needling, stitching and/or chemical adhesives"
Other names that GCLs have been listed under, are "clay blankets", "clay mats", "bentonite
blankets , bentonite mats", "prefabricated bentonite clay blankets", etc. GCLs are hydraulic
barriers to water, leachate or other liquids. As such, they are used to augment or replace
compacted clay liners or geomembranes, or they are used in a composite manner to augment the
more traditional clay liner or geomembrane materials.
c- * P^88 section sketches of the currently available GCLs at the time of writing are shown in
Fig. 4.1. General comments regarding each type follow:
• Figure 4.1 (a) illustrates a bentonite clay mixed with a water soluble adhesive which is
supported by individual geotextiles on both its upper and lower surfaces.
• Figure 4.1(b) illustrates a stitchbonded variation of the above type of product whereby
the upper and lower geotextiles are joined by continuous sewing in discrete rows
throughout the machine direction of the product as well as a recent product which
consists of bentonite powder alone with no admixed adhesive.
• Figure 4.1(c) illustrates a bentonite clay powder or granules, containing no adhesive
which is supported by individual geotextiles on its upper and lower surfaces and is
needle punched throughout to provide for its stability. Several variations of this type of
GCL are available including styles with clay infilled in the voids of the upper geotextile.
• Figure 4.1(d) illustrates a bentonite clay which is admixed with an adhesive and is
supported by a geomembrane on its lower surface, as shown, or it can be used in an
inverted manner with the geomembrane side facing upward. Variations of this product
are also available with textured or raised geomembrane surfaces.
All of the GCL products available in North America use sodium bentonite clay (predominately
smectite) powder or granules at as-manufactured mass per unit areas in the range of 3.2 to 6.0
A%m £ n t0 £ / )' The clay thickness in the various products vary between the range of
4.0 to 0.0 mm (160 to 320 mils). GCLs are delivered to the job site at moisture contents which
174
-------
Upper Geotextile
Lower Geotextile
(a) Adhesive Bound Clay to Upper and Lower Geotextiles
~5mm
Upper Geotextile
Stitch Bonded
in Rows
Lower Geotextile
(b) Stitch Bonded Clay Between Upper and Lower Geotextiles
~ 4-6 mm
Upper Geotextile
Needle Punched
Fibers Throughout
Lower Geotextile
(c) Needle Punched Clay Through Upper and Lower Geotextiles
~ 4.5 mm
(d) Adhesive Bound Clay to a Geomembrane
Lower or Upper
Geomembrane
Figure 4.1 - Cross Section Sketches of Currently Available Geosynthetic Clay Liners (GCLs)
175
-------
vary from 5 to 23%, depending upon the local humidity. Note that this is sometimes referred to in
the technical literature as the '"dry" state. The types of geotextiles used with the different products
vary widely in their manufacturing style (e.g., woven slit film, needle punched nonwoven,
spunlaced, heat bonded nonwovens, etc.) and in their mass per unit area [e.g., varying from 85
g/m2 (2.5 oz/yd2) to 1000 g/m2 (30 oz/yd2). The particular product with a geomembrane backing
can also vary in its type, thickness and surface texture.
GCLs are factory made in widths of 2.2 to 5.2 m (7 to 17 ft) and lengths of 30 to 61 m
(100 to 200 ft). Upon manufacturing GCLs are rolled onto a core and are covered with a plastic
film to prevent additional moisture gain during storage, transportation ,and placement prior to their
final covering with an overlying layer.
4.2 Manufacturing
This section on manufacturing of GCLs will discuss the various raw materials,
manufacturing of the rolls, and covering of the rolls.
4.2.1 Raw Materials
The bentonite clay materials currently used in the manufacture of GCLs are all of the
sodium montmorillonite variety which is a naturally occurring mineral in the Wyoming and North
Dakota regions of the USA. After the clay is mined, it is dried, pulverized, sieved and stored in
silos until it is transported to a GCL manufacturing facility.
The other raw material ingredient used in the manufacture of certain GCLs (recall Section
4.1) is an adhesive which is a proprietary product among the two manufacturers that produce this
type of GCL. Additionally, geotextiles and/or geomembranes are used as substrate (below the
clay) or superstrate (above the clay) layers which are product specific as was mentioned in the
previous section.
Regarding a specification or MQA document for the various raw materials used in the
manufacture of GCLs, the following items should be considered.
1. The clay should meet the GCL manufacturer's specification for quality control
purposes. This is often 70% to 90% sodium montmorillonite clay from the
Wyoming/North Dakota "Black Hills" region of bentonite deposits. A certificate of
analysis should be submitted by the vendor for each lot of clay supplied. While the
situation is far from established, the certificate may include the various compounds of
the clay, per X-Ray diffraction or methylene-blue absorption, particle size per ASTM
D-422or C-136, moisture content per ASTM D-2216or D-4643, bulk density per
ASTM B-417, and free swell.
2. The GCL manufacturer should have a MQC plan which describes the procedures for
accomplishing quality in the final product, various tests to be conducted and their
frequency. This MQC document should be fully implemented and followed.
3. The MQC test methods that the GCL manufacturer performs on the clay component
may include the following; free swell per USP-NF-XVIII or ASTM draft standard,
"Determination of Volumetric Free Swell of Powdered Bentonite Clay," plate water
absorption per ASTM E-946, moisture content per ASTM D-2216or D-4643 and
(sometimes) particle size per ASTM D-422, fluid loss per API 13B, pH per ASTM D-
4972, and liquid/plastic limit per ASTM D-4318.
176
-------
4. For those products which use adhesives, the composition of the proprietary adhesive is
rarely specified. If a statement is required, it should signify that the adhesive selected
has been successfully used in the past and to what extent.
5. The geotextiles used as the substrate or the superstrate, or the geomembrane vary
according to the particular style of product. Manufacturers current literature should be
used in this regard. If a statement is required it should signify that the products selected
have been successfully used in the past and to what extent.
6. If further detail is needed as to a specification for the geotextiles, see Chapter 6.
Similarly, specifications for geomembranes are found in Chapter 3.
7. The type of sewing thread (or yarn) which is used in joining the products is rarely
specified. If a statement is required it should signify that the materials selected have
been successfully used in the past and to what extent.
4.2.2 Manufacturing
The raw materials just described are used to make the final GCL product. The production
facilities are all relatively large operations where the products are made in a continuous manner.
Process quality control is obviously necessary and is practiced by all GCL manufacturers. Figure
4.2 illustrates, in schematic form, the various processing methods used for those GCLs which
have adhesives mixed with the clay and those which are stitch bonded and needle punched. Figure
4.2(a) illustrates an adhesively bonded clay product which has an adhesive sprayed in a number of
layers with intermittent additions of bentonite. The clay is placed either between geotextiles or on a
geomembrane. Figure 4.2(b) illustrates the needle punching or stitch bonding of a bentonite clay
powder after it is placed between the covering geotextiles. Windup around a core and placement of
the protective covering is common among all GCLs.
There are numerous items which should be included in a specification or MQA document
focused on the manufactured GCL product.
1. There should be verification that the actual geotextiles or geomembrane used meet the
manufacturer's specification for that particular type and style.
2. A statement should be included that the geotextile property values are based on the
minimum average roll value (MARV) concept. The geomembrane's properties are
generally based on average values.
3. Verification that needle punched nonwoven geotextiles have been inspected
continuously for the presence of broken needles using an in-line metal detector. There
should also be a magnet, or other device, for removal of broken needles.
4. Verification that the proper mass per unit area of bentonite clay has been added to the
product should be provided. At a minimum, this should consist of providing a
calculated value based on the net weight of the final roll divided by its area (with
deduction for the mass per unit area of the geosynthetics and the adhesive, if any).
5. Thickness measurements are product dependent, i.e., some GCLs can be quality
controlled via thickness while others cannot.
177
-------
Lower Geotextile
or Gcomembrane
Bentonite
Bentonite
Upper
[•;.••,•}.] Geotextile
Bentonite tv-vJAdhesive
Calender
Staion
or Oven
(a) Adhesive Mixed with Clay
Lower
Geotextile
Q
Bentonite
Hopper "A"
Bentonite
Hopper "B" (opt.)
Upper
Geotextie
a
Q
Needling or Stith
Bonding Station
- •~i"Jir"rJir"""""^^^ii^'^^IB>^^^TnnT-a^
**^tt*?#tt:tt3^WJ&^^
Tb
Windup
(b) Needle Punched or Stitch Bonded Through Cla y
Figure 4.2 - Schematic Diagrams of the Manufacture of Different Types of Geosynthetic Clay
Liners (GCLs)
178
-------
6. It is recommended that the overlap distance on both sides of the GCL be marked with
two continuous waterproof lines guiding the minimum overlap distances.
7. The product should be wrapped around a core which is structurally sound such that it
can support the weight of the roll without excessive bending or buckling under normal
handling conditions as recommended by the manufacturer.
8. The GCL manufacturer should have a MQC plan for the finished product, which
includes sampling frequency, and it should be implemented and followed.
9. The manufacturer's quality control tests on the finished product should be stipulated
and followed. Typical tests include thickness per ASTM D-1777 or ASTM D-5199,
total product mass per unit area per ASTM D-5261, clay content mass per unit area per
ASTM D-5261, hydraulic conductivity (permeability) per ASTM D-5084 or GRIGCL2
and sometimes shear strength at various locations such as top, mid-plane and bottom
per ASTM D-5321. Other tests as recommended by the manufacturer are also
acceptable.
4.2.3 Covering of the Rolls
The final step in the manufacturing of GCLs is their covering with a waterproof, tightly-fit,
plastic covering. This covering is sometimes a spirally wound polyethylene film approximately
0.05 to 0.08 mm (2 to 5 mils) thick and is the final step in production. The covering can also be a
plastic bag, or sheet, pulled over the product as a secondary operation. Figure 4.3 shows the
factory storage of GCLs, with their protective covering, before shipment to the field.
Some items for a specification or MQA document with regard to the covering of GCLs are
the following:
1. The manufacturer should clearly stipulate the type of protective covering and the
manner of cover placement. The covering should be verified as to its capability for safe
storage and proper transportation of the product.
2. The covering should be placed around the GCL in a workmanlike manner so as to
effectively protect the product on all of its exposed surfaces and edges.
3. The central core should be accessible for handling by fork lift vehicles fitted with a long
pole (i.e., a "stinger") attached. For wide GCLs, e.g., wider than approximately 3.5 m
(11.5 ft), handling should be by overhead cranes utilizing two dedicated slings
provided on each roll at approximately the one-third points.
4. Clearly visible labels should identify the name and address of the manufacturer,
trademark, date of manufacture, location of manufacture, style, roll number, lot
number, serial number, dimensions, weight and other important items for proper
identification. Refer to ASTM D-4873 for proper labeling in this regard. In some
cases, the roll number itself is adequate to trace the entire MQC record and
documentation.
179
-------
Figure 4.3 - Indoor Factory Storage of Geosynthetic Clay Liners (GCLs) Waiting for Shipment to
a Job Site
4.3 Handling
A number of activities occur between the manufacture of a GCL, its final positioning in the
field and subsequent backfilling. Topics such as storage at the factory, transportation, storage at
the site and acceptance/conformance testing will be described in this section.
4.3.1 Storage at the Manufacturing Facility
Storage of GCLs at the manufacturers facility is common. Storage times typically range
from days to six months. Figure 4.3 illustrated typical GCL storage at a fabrication facility.
Some specifications or MQA items to consider for storage and handling of GCLs are the
following:
1. GCLs should always be stored indoors until they are ready to be transported to the field
site.
2. Handling of the GCLs should be such that the protective wrapping is not damaged. If
it is, it must be immediately rewrapped by machine or by hand. In the case of minor
tears it may be taped.
180
-------
3. Placement and stacking of rolls should be done in a manner so as to prevent thinning of
the product at the points of contact with the storage frame or with one another. Storage
in individually supported racks is common so as to more efficiently use floor space.
4.3.2 Shipment
Rolls of GCLs are shipped from the manufacturers storage facility to the job site via
common carrier. Ships, railroads and trucks have all been used depending upon the locations of
the origin and final destination. The usual carrier within the USA is truck, which should be with
the GCLs contained in an enclosed trailer as shown in Fig. 4.4(a), or on an open flat-bed trailer
which is tarpaulin covered as shown in Fig. 4.4(b). Some manufacturers have their own dedicated
fleet of trucks. The rolls are sometimes handled by fork lift with a stinger attached. The "stinger"
is a long tapered rod which fits inside the core upon which the GCL is wrapped, see Fig. 4.4(a).
Alternatively, rolls can be handled using the two captive slings provided on each roll.
Insofar as a specification or MQA document is concerned, a few items should be considered.
1. The GCLs should be shipped by themselves with no other cargo which could damage
them in transit, during stops, or while offloading other materials.
2. The method of loading the GCL rolls, transporting them and offloading them at the job
site should not cause any damage to the GCL, its core, nor its protective wrapping.
3. Any protective wrapping that is damaged or stripped off of the rolls should be repaired
immediately or the roll should be moved to a enclosed facility until its repair can be
made to the approval of the quality assurance personnel.
4. If any of the clay has been lost during transportation or from damage of any type, the
outer layers of GCL should be discarded until undamaged product is evidenced. The
remaining roll must be rewrapped in accordance with the manufacturer's original
method to prevent hydration or further damage to the remaining roll.
4.3.3 Storage at the Site
Storage of GCLs at the field site is cautioned due to the potential for moisture pickup (even
through the plastic covering) or accidental damage. The concept of "just-in-time-delivery" can be
used for GCLs transported from the factory to the field. When storage is required for a short
period of time i.e., days or a few weeks, and the product is delivered in trailers, the trailers can be
unhitched from their tractors and used as temporary storage. See the photograph of Fig. 4.5(a).
Alternatively, storage at the job site can also be acceptable if the GCLs are properly positioned,
protected and maintained, see Fig. 4.5(b).
If storage of GCLs is permitted on the job site, offloading of the rolls should be done in an
acceptable manner. Some specification or CQA* document items to consider are the following.
1. Handling of rolls of GCLs should be done in a competent manner such that damage
does not occur to the product nor to its protective wrapping. In this regard ASTM D-
4873, "Identification, Storage and Handling of Geotextiles", should be referenced and
followed.
* Note that the designations of MQC and MQA will now shift to CQC and CQA since field construction personnel
are involved.
181
-------
Figure 4.4(a) - Fork Lift Equipped with a "Stinger"
i
tSlalM
Figure 4.4(b) - GCL Rolls on a Flat-Bed Trailer
182
-------
Figure 4.5(a) - Photograph of Temporary Storage of GCLs in their Shipping Trailers
Figure 4.5(b) - Photograph of Temporary Storage of GCLs at Project Site
183
-------
2. The location of temporary field storage should not be in areas where water can
accumulate. The rolls should be stored on high flat ground or elevated off of the
ground so as not to form a dam creating the ponding of water. It is recommended to
construct a platform so that GCL rolls are continuously supported along their length.
3. The rolls should not be stacked so high as to cause thinning of the product at points of
contact. Furthermore, they should be stacked in such a way that access for
conformance testing is possible.
4. If outdoor storage of rolls is to be longer than a few weeks particular care, e.g., using
tarpaulins, should be taken to minimize moisture pickup or accidental damage. For
storage periods longer than one season a temporary enclosure should be placed over the
rolls, or they should be moved within an enclosed facility.
4.3.4 Acceptance and Conformance Testing
Upon delivery of the GCLs to the field site, the CQA officer should see that conformance
test samples are obtained. These samples are then sent to the CQA Laboratory for testing to ensure
that the GCL conforms to the project plans and specifications. The samples are taken from selected
rolls by removing the protective wrapping and cutting full-width, 1 m (3 ft.) long samples from the
outer wrap of the selected roll(s). Sometimes one complete outer revolution of GCL is discarded
before the test sample is taken. The rolls are immediately re-wrapped and replaced in the shipping
trailers or in the temporary field storage area. Alternatively, conformance testing could be
performed at the manufacturer's facility and when completed the particular lot should be identified
for the particular project under investigation..
Items to consider for a specification or CQA document in this regard are the following:
1. The samples should be identified by type, style, lot and roll numbers. The machine
direction should be noted on the sample(s) with a waterproof marker.
2. A lot is usually defined as a group of consecutively numbered rolls from the same
manufacturing line. Other definitions are also possible and should be clearly stated in
the CQA documents.
3. Sampling should be done according to the project specification and/or CQA documents.
Unless otherwise stated, sampling should be based on a lot basis. Different
interpretations of sampling frequency within a lot are based on total area or on number
of rolls. For example, sampling could be based on 10,000 m2 (100,000 ft2) of area or
on use of ASTM D-4354 which is based on rolls.
4. Testing at the CQA laboratory may include mass per unit area per ASTM D-5261, and
free swell of the clay component per GRI-GCL1. The sampling frequency for these
index tests should be based on ASTM D-4354. Other conformance tests, which are
more performance oriented, could be required by the project specifications but at a
reduced frequency compared to the above mentioned index tests. Examples are
hydraulic conductivity (permeability) ASTM D-5084 (mod.) or GRIGCL2 and direct
shear testing per ASTM D-5321. The sampling frequency for these performance tests
might be based on area, e.g., one test per 10,000 m2^(100,000 ft2).
184
-------
5. If testing of the geotextiles, or geomembrane, covering the GCLs is desired it should be
done on the original rolls of the geotextiles, or geomembrane, before they are fabricated
into the GCL product. Once fabricated their properties will change considerably due to
the needling, stitching and/or gluing during manufacturing.
6. Peel testing of needle punched or stitch bonded GCLs should be done in accordance
with ASTM D-413 (mod.). The sampling frequency is recommended to be one test per
2000 m2 (20,000 ft2).
7. Conformance test results should be sent to the CQA engineer prior to installation of any
GCL from the lot under review.
8. The CQA engineer should review the results and should report any nonconformance to
the Owner/Operator's Project Manager.
9. The resolution of failing conformance tests must be clearly stipulated in the
specifications or CQA documents. Statements should be based upon ASTM D-4759
entitled "Determining the Specification Conformance of Geosynthetics."
4.4 Installation
This section will cover the placement, joining, repairing and covering of GCLs.
4.4.1 Placement
The installation contractor should remove the protective wrapping from the rolls to be
deployed only after the substrate layer (soil or other geosynthetic) in the field has been approved by
CQA personnel. The specification and CQA documents should be written in such a manner as to
ensure that the GCLs are not damaged in any way. A CQA inspector should be present at all times
during the handling, placement and covering of GCLs. Figure 4.6(a) shows the typical placement
of a GCL in the field on soil subgrade and Fig. 4.6(b) shows placement (without heavy
equipment) on an underlying geosynthetic.
The following items should be considered for inclusion in a specification or CQA
document.
1. The installer should take the necessary precautions to protect materials underlying the
GCL. If the substrate is soil, construction equipment can be used to deploy the GCL
providing excessive rutting is not created. Excessive rutting should be clearly defined
and quantified. In some cases 25 mm (1.0 in.) is the maximum rut depth allowed. If
the ground freezes, the depth of ruts should be further reduced to a specified value. If
the substrate is a geosynthetic material, GCL deployment should be by hand, or by use
of small jack lifts or light weight equipment on pneumatic tires having low ground
contact pressure.
2. The minimum overlap distance which is specified should be verified. This is typically
150 to 300 mm (6 to 12 in.) depending upon the particular product and site conditions.
185
-------
Figure 4.6(a) - Field Deployment of a GCL on a Soil Subgrade
B^^
; ' -•:•- ; r: •-!' !"' l"i:ri™«WT'lS»!CT«>^^fc;-;;;!;::-l:i;::S;1;1;'
i
Figure 4.6(b) - Field Deployment of a GCL on an Underlying Geosynthetic
186
-------
3. Additional bentonite clay should be introduced into the overlap region with certain types
of GCLs. There are typically those with needle punched nonwoven geotextiles on their
surfaces. The clay is usually added by using a line spreader or line' chalker with the
bentonite clay in a dry state. Alternatively, a bentonite clay paste, in the mixture range
of 4 to 6 parts water to 1 part of clay, can be extruded in the overlap region.
Manufacturer's recommendations on type and quantity of clay to be added should be
followed.
4. During placement, care must be taken not to entrap in or beneath the GCL, fugitive
clay, stones, or sand that could damage a geomembrane, cause clogging of drains or
filters, or hamper subsequent seaming of materials either beneath or above the GCL.
5. On side slopes, the GCL should be anchored at the top and then unrolled so as to keep
the material free of wrinkles and folds.
6. Trimming of the GCL should be done with great care so that fugitive clay particles do
not come in Contact with drainage materials such as geonets, geocomposites or natural
drainage materials.
7'. The deployed GCL should be visually inspected to ensure that no potentially harmful
objects are present, e.g., stones, cutting blades, small tools, sandbags, etc.
4.4.2 Joining
Joining of GCLs is generally accomplished by overlapping without sewing or other
mechanical connections. The overlap distance requirements should be clearly stated. For all GCLs
the required overlap distance should be marked on the underlying layer by a pair of continuous
guidelines. The overlap distance is typically 150 to 300 mm (6 to 12 in.). For those GCLs, with
needle punched nonwoven geotextiles on their surfaces, dry bentonite is generally placed in the
overlapped region. If this is the case, utmost care should be given to avoid fugitive bentonite
particles from coming into contact with leachate collection systems. Another variation, however,
has been to extrude a moistened tube of bentonite into the overlapped region.
Items to consider for a specification or CQA document follow:
1. The amount of overlap for adjacent GCLs should be stated and adhered to in field
placement of the materials.
2. The overlap distance is sometimes different for the roll ends versus the roll edges. The
values should be stated and followed.
3. If dry or moistened bentonite clay (or other material) is to be placed in the overlapped
region, the type and amount should be stated in accordance with the manufacturer's
recommendations and/or design considerations. Index testing requirements for proper
verification of the clay should be specified accordingly. Furthermore, the placement
procedure should be clearly outlined so as to have enough material to make an
adequately tight joint and yet not an excessive amount which could result in fugitive
clay particles.
4.4.3 Repairs
For the geotextile-related GCLs, holes, tears or rips in the covering geotextiles made during
187
-------
transportation, handling, placement or anytime before backfilling should be repaired by patching
using a geotextile. If the bentonite component of the GCL is disturbed either by loss of material or
by shifting, it should be covered using a full GCL patch of the same type of product.
Some relevant specification or CQA document items follow.
1. Any patch, used for repair of a tear or rip in the geotextile, should be done using the
same type as the damaged geotextile or other approved geotextile by the CQA engineer.
2. The size of the geotextile patch must extend at least 30 cm (12 in.) beyond any portion
of the damaged geotextile and be adhesive or heat bonded to the product to avoid
shifting during backfilling with soil or covering with another geosynthetic.
3. If bentonite particles are lost from within the GCL or if the clay has shifted, the patch
should consist of the full GCL product. It should extend at least 30 cm (12 in.) beyond
the extent of the damage at all locations. For those GCLs requiring additional bentonite
clay in overlap seaming, the similar procedure should be use for patching.
4. Particular care should be exercised in using a GCL patch since fugitive clay can be lost
which can find its way into drainage materials or onto geomembranes in areas which
eventually are to be seamed together.
4.5 Backfilling or Covering
The layer of material placed above the deployed GCL will be either soil or another
geosynthetic. Soils will vary from compacted clay layers to coarse aggregate drainage layers.
Geosynthetics will generally be geomembranes although other geosynthetics may also be used
depending on the site specific design. The GCL should generally be covered before a rainfall or
snow event occurs. The reason for covering with the adhesive bonded GCLs is that hydration
before covering can cause changes in thickness as a result of uneven swelling or whenever
compressive or shear loads are encountered. Hydration before covering may be less of a concern
for the needled and stitch bonded types of GCLs, but migration of the fully hydrated clay in these
products might also be possible under sustained compressive or shear loading. Figure 4.7 shows
the premature hydration of a GCL being gathered up by hand to be discarded in the adjacent
landfill.
Some recommended specifications or CQA document items are as follows:
1. The GCL should be covered with its subsequent layer before a rainfall or snowfall
occurs.
2. The GCL should not be covered before observation and approval by the CQA
personnel. This requires close coordination between the installation crew and the CQA
personnel.
3. If soil is to cover the GCL it should be done such that the GCL or underlying materials
are not damaged. Unless otherwise specified, the direction of backfilling should
proceed in the direction of downgradient shingling of the GCL overlaps. Continuous
observation of the soil placement is recommended.
4. If a geosynthetic is to cover a GCL, both underlying and the newly deployed material
should not be damaged.
188
-------
5. The overlying material should not be deployed such that excess tensile stress is
mobilized in the GCL. On side slopes, this requires soil backfill to proceed from the
bottom of the slope upward. Other conditions are site specific and material specific.
Figure 4.7 - Premature Hydration of a Geosynthetic Clay Liner Being Gathered and Discarded due
to its Exposure to Rainfall Before Covering
4.6 References
API 13B, "Fluid Loss of Bentonite Clays"
ASTM B-417, "Apparent Density of Non Free-Flowing Metal Powders"
ASTM C-136, "Sieve Analysis of Fine and Coarse Aggregates"
189
-------
ASTM D-413, "Rubber Property - Adhesion to Flexible Substrate"
ASTM D-422, "Particle Size Analysis of Soils"
ASTM D-1777, "Measuring Thickness of Textile Materials"
ASTM D-2216, "Laboratory Determination of Water (Moisture) Content of Soil and Rock"
ASTM D-4318, "Liquid Limit, Plastic Limit, and Plasticity Index of Soils"
ASTM D-4354, "Sampling of Geosynthetics for Testing"
ASTMD-4643, "Determination of Water (Moisture Content) of Soil by Microwave Oven Method"
ASTM D-4759, "Determining the Specification Conformance of Geosynthetics"
ASTM D-4873, "Identification, Storage and Handling of Geotextiles"
ASTM D-4972, "Method for pH of Soils"
ASTM D-5084, "Hydraulic Conductivity of Saturated Porous Material Using A Flexible Wall
Permeameter"
ASTM D-5199, "Nominal Thickness of Geotextiles and Geomembranes"
ASTM D-5261, "Measuring Mass per Unit Area of Geotextiles"
ASTM D-5321, "Determining the Coefficient of Soil and Geosynthetic or Geosynthetic and
Geosynthetic Friction by the Direct Shear Method"
ASTME-946, "Water Absorption of Bentonite of Porous Plate Method"
GRIGCL1, "Free Swell Conformance Test of Clay Component of a GCL"
GRIGCL2, "Permeability of Geosynthetic Clay Liners (GCLs)"
USP-NF-XVII, "Swell Index Test"
190
-------
Chapter 5
Soil Drainage Systems
5.1 Introduction and Background
Natural soil drainage materials are used extensively in waste containment units. The most
common uses are:
1. Drainage layer in final cover system to reduce the hydraulic head on the underlying
barrier layer and to enhance slope stability by reducing seepage forces in the cover
system.
2. Gas collection layer in final cover systems to channel gas to vents for controlled
removal of potentially dangerous gases.
3. Leachate collection layer in liner systems to remove leachate for treatment and to
remove precipitation from the disposal unit in areas where waste has not yet been
placed.
4. Leak detection layer in double liner systems to monitor performance of the primary
liner and, if necessary, to serve as a secondary leachate collection layer.
5. Drainage trenches to collect horizontally-flowing fluids, e.g., ground water and
gas.
Drainage layers are also used in miscellaneous ways, such as to drain liquids from backfill behind
retaining walls or to relieve excess water pressure in critical areas such as the toe of slopes.
5.2 Materials
Soil drainage systems are constructed of materials that have high hydraulic conductivity.
High hydraulic conductivity is not only required initially, but the drainage material must also
maintain a high hydraulic conductivity over time and resist plugging or clogging. The hydraulic
conductivity of drainage materials depends primarily on the grain size of the finest particles present
in the soil. An equation that is occasionally used to estimate hydraulic conductivity of granular
materials is Hazen's formula:
k=(Dio)2 (5.1)
where k is the hydraulic conductivity (cm/s) and Dip is the equivalent grain diameter (mm) at
which 10% of the soil is finer by weight. To determine the value of DIQ, a plot is made of the
grain-size distribution of the soil (measured following ASTM D-422) as shown in Fig. 5.1. The
equivalent grain diameter (Dio) is determined from the grain size distribution curve as shown in
Fig. 5.1.
Experimental data verify that the percentage of fine material in the soil dominates hydraulic
conductivity. For example, the data in Table 5.1 illustrate the influence of a small amount of fines
191
-------
upon the hydraulic conductivity of a filter sand. The addition of just a few percent of fine material
to a drainage material can reduce the hydraulic conductivity of the drainage material bv 100 fold or
more.
100
I
.Q
b
i!
•g
-------
Table 5.1 Effect of Fines on Hydraulic Conductivity of a Washed Filter Aggregate (from
Cedergren, 1989)
Percent Passing
No. 100* Sieve
0
2
4
6
7
Hydraulic Conductivity (cm/s)
0.03 to 0.11
0.004 to 0.04
0.0007 to 0.02
0.0002 to 0.007
0.00007 to 0.001
""Opening size is 0.15 mm.
Drainage materials may also be required to serve as filters. For instance, as shown in Fig.
5.2, a filter layer may be needed to protect a drainage layer from plugging. The filter layer must
serve three functions:
1 . The filter must prevent passage of significant amounts of soil through the filter,
. i.e., the filter must retain soil.
2. The filter must have a relatively high hydraulic conductivity, e.g., the filter should
be more permeable than the adjacent soil layer.
3. The soil particles within the filter must not migrate significantly into the adjacent
drainage layer.
Filter specifications vary somewhat, but the design procedures are similar. The
determination of requirements for a filter material proceeds as follows:
1 . The grain size distribution curve of the soil to be retained (protected) is determined
following procedures outlined in ASTM D-422. The size of the protected soil at
which 15% is finer (Dis, soii) and 85% is finer (Dgs, soil) is determined.
2. Experience shows that the particles of the protected soil will not significantly
penetrate into the filter if the size of the filter at which 15% is finer (Pis, filter) is
less than 4 to 5 times Dgs of the protected soil:
, filter < (4 to 5) D85, soil (5.2)
193
-------
4.
5.
Experience shows that the hydraulic conductivity of the filter will be significantly
greater than that of the protected soil if the following criterion is satisfied:
, filter > 4 Di5)SOi!
(5.3)
To ensure that the particles within the filter do not tend to migrate excessively into
the drainage layer, the following criterion may be applied:
Dl5, drain^ (4 to 5) D15, filter
(5.4)
Experience shows that the hydraulic conductivity of the drain will be significantly
greater than that of the filter if the following criterion is satisfied:
Dl5, drain > 4 Di5> filter
(5.5)
Filter design is complicated significantly by the presence of biodegradable waste materials,
e.g., municipal solid waste, directly on top of the filter. In such circumstances, the usual filter
criteria may be modified to satisfy site-specific requirements. Some degree of reduction in
hydraulic conductivity of the filter layer may be acceptable, so long as the reduction does not
impair the ability of the drainage system to serve its intended function. A laboratory test method to
quantify the hydraulic properties of both soil and geotextile filters that are exposed to leachate is
ASTM D-1987. However, regardless of specific design criteria, the gradational characteristics of
the filter material control the behavior of the filter. CQC/CQA personnel should focus their
attention on ensuring that the drainage material and filter material meet the grain-size-distribution
requirements set forth in the construction specifications, as well as other specified requirements
such as mineralogy of the materials.
Soil Layer Whose Particles Must Not
Migrate into Underlying Drainage Layer
Filter Layer to Prevent Migration
of Soil Particles into Drainage Layer
Figure 5.2 - Filter Layer Used to Protect Drainage Layer from Plugging
194
-------
5.3 Control of Materials
The recommended procedure for verifying the hydraulic conductivity for a proposed
drainage material is as follows. Samples of the proposed material should be obtained and shipped
to a laboratory for testing. Samples should be compacted in the laboratory to a density that will be
representative of the density to be used in the field. Hydraulic conductivity should be measured
following procedures in ASTM D-2434 and compared with the required minimum values stated in
the construction specifications. If the hydraulic conductivity exceeds the minimum value, the
material is tentatively considered to be acceptable. However, it should be realized that the process
of excavating and placing the drainage material will cause some degree of crushing of the drainage
material and will produce additional fines. Thus, the construction process itself tends to increase
the amount of fines in the drainage material and to decrease the hydraulic conductivity of the
material. If the drainage material just barely meets the hydraulic conductivity requirements stated in
the construction specifications from initial tests, there is a good possibility that the material will fail
to meet the required hydraulic conductivity standard after the material has been placed. As a rule of
thumb, approximately one-half to one percent of additional fines by weight will be generated every
time a drainage material is handled, e.g., one-half to one percent additional fines would be
generated when the drainage layer material is excavated and an additional one-half to one percent of
fines would be generated when the material is placed. Also, the reproducibility of hydraulic
conductivity tests is not well established; a material may just barely meet the hydraulic conductivity
standard in one test but fail to meet minimum requirements in another test. Finally, if the drainage
materials are found to be suitable prior to placement but unsuitable after placement, an extremely
difficult situation arises — it is virtually impossible to remove and replace the drainage material
without risking damage to underlying geosynthetic components, e.g., a geomembrane. Therefore,
some margin of safety should be factored into the selection of drainage material.
Because it is extremely difficult to remove and replace a drainage material without
damaging an underlying geosynthetic component, testing of the drainage material should occur
prior to placement of the material. The CQC personnel should have a high degree of confidence
that the drainage material is suitable prior to placement of the material. Because the construction
process may alter the characteristics of the drainage material, it is important that CQA tests also be
performed on the material after it has been placed and compacted (if it is compacted).
The usual tests involve determination of the grain size distribution of the soil (ASTM D-
422) and hydraulic conductivity of the soil (ASTM D-2434). Hydraulic conductivity tests tend to
be time consuming and relatively difficult to reproduce precisely; the test apparatus that is
employed, the compaction conditions for the drainage material, and other details of testing may
significantly influence test results. Grain-size distribution analyses are simpler. Therefore, it is
recommended that the CQA testing program emphasize grain-size distribution analyses, with
particular attention paid to the amount of fines present in the drainage material, rather than
hydraulic conductivity testing. The percent of fines is normally defined as the percent on a dry
weight basis passing through a No. 200 sieve (openings of 0.075 mm). Again, it is emphasized
that close testing and inspection of the borrow source or the supplier prior to placement of the
material is critical, particularly if the drainage material is underlain by a geosynthetic material.
The recommended tests and frequency of testing are shown in Table 5.2. The same
principles for sampling strategies discussed in Chapter 2 may be applied to location of tests or
location of samples for drainage layer materials. Also, occasional failing tests may be allowed, but
it is recommended that no more than 5% of the CQA tests be allowed to deviate from
specifications, and the deviations should be relatively minor, i.e., no more than about 2% fines
beyond the maximum value allowed and no less than about one-fifth the minimum allowable
hydraulic conductivity.
195
-------
Table 5.2 - Recommended Tests and Testing Frequencies for Drainage Material
<>f Sample Type of Test Minimum Frequency
Potential Borrow Source Grain Size 1 per 2 000 m3
(ASTMD-422) '
Hydraulic Conductivity 1 per 2,000 m3
(ASTMD-2434)
Carbonate Content* 1 per 2,000 m3
(ASTMD-4373)
On Site; After Placement Grain Size 1 per Hectare for Drainage
and Compaction (ASTM D-422) Layers; 1 per 500 m3 for
Other Uses
Hydraulic Conductivity 1 per 3 Hectares for Drainage
(ASTM D-2434) Layers; 1 per 1,500 m3 for
Other Uses
Carbonate Content* 1 per 2,000 m3
(ASTMD-4373)
"The frequency of carbonate content testing should be greatly reduced to 1 per 20,000 m3 for those drainage materials
that obviously do not and cannot contain significant carbonates (e.g., crushed basalt).
5.4 Location of Borrow Sources
The construction specifications usually establish criteria that must be met by the drainage
material. Earthwork contractors are normally given latitude in locating a suitable source of material
that meets construction specifications. On occasion the materials may be available on site or from a
nearby piece of property, but most frequently the materials are supplied by a commercial materials
company. If the materials are supplied by an existing materials processor, stockpiles of materials
are usually readily available for testing and no geotechnical investigations are required other than
to test the proposed borrowed material.
5.5 Processing of Materials
Materials may be processed in several ways. Oversized stones or rocks are typically
removed by sieving. Fine material may also be removed by sieving. Washing the fines out of a
sand or gravel can be particularly effective in removing silt and clay sized particles from granular
196
-------
material. For drainage layer materials that are supplied from a commercial processing facility, the
facility owner is usually experienced in processing the material to remove fines.
For the CQA inspector the main processing issues are removal of oversized material,
removal of angular material (if required to minimize potential to puncture a geomembrane), and
assurance that excessive fines will not be present in the material.
On occasion the amount of limestone, dolostone, dolomite, calcite, or other carbonates in
the drainage material may be an issue. Carbonate materials are slightly soluble in water. If the
drainage material contains excessive carbonate, the carbonate may dissolve at one location and
precipitate at another, plugging the material. CQA inspectors should also be cognizant of the need
to make sure that carbonate components are not present in excessive amounts. If the specifications
place a limit on carbonate content, tests should be performed to confirm compliance (Table 5.2).
5.6 Placement
Drainage materials may be placed in layers (e.g., as leachate collection layers) or they may
be placed in drainage trenches (e.g., to provide drainage near the toe of a slope). Placement
considerations differ depending on the application.
5.6.1 Drainage Layers
Granular drainage materials are usually hauled to the placement area in dump trucks,
loosely dumped from the truck, and spread with bulldozers. The contractor should dump and
spread the drainage material in a manner that minimizes generation of fine material. For instance,
light-contact-pressure dozers can be used to spread the drainage material and minimize the stress on
the granular material. Granular materials placed on top of geosynthetic components on side slopes
should be placed from the bottom of the slope up.
When granular drainage material is placed on a previously-placed geomembrane or
geotextile and spread with a dozer, the sand or gravel should be lifted and tumbled forward so as to
minimize shear forces on the underlying geosynthetic. The dozer should not be allowed to
"crowd" the blade into the granular material and drag it over the surface of the underlying
geosynthetic material.
Granular materials are often placed with a backhoe in small, isolated areas such as sumps.
Some drainage materials may even be placed by hand, e.g., in sumps and around drainage pipes.
CQA personnel should position themselves in front of the working face of the placement
operation to be able to observe the materials as they are spread and to ensure that there is no
puncture of underlying materials. CQA personnel should observe placement of drainage layers to
ensure that fine-grained soil is not accidentally mixed with drainage material.
5.6.2 Drainage Trenches
Drainage materials are often placed in trenches to provide for subsurface drainage of water.
A typical trench configuration is shown in Fig. 5.3. Often, a perforated pipe will be placed in the
bottom of the trench. Geotextile filters are often required along the side walls to prevent migration
of fine particles into the drainage material. CQA personnel should carefully review the plans and
specifications to ensure that the drainage and filter components have been properly located in the
trench prior to backfill.
197
-------
Geotextile Filter
Figure 5.3 - Typical Design of a Drainage Trench
CQC/CQA personnel should be aware of all applicable safety requirements for inspection
of trenches. Unsupported trenches can pose a hazard to personnel working in the trench or
inspecting the trench. For trenches that are supported by shoring, CQA personnel should review
with the contractor the plan for pulling the shoring in terms of the timing for placement of materials
and ensure that the procedures are in accord with the specifications for the project.
. G.ranular backfill is usually placed in a trench by a backhoe. For narrow trenches, a
rremie" is commonly used to direct the material into the trench without allowing the material to
come into contact with soil on the sidewalls of the trench. Sometimes drainage materials are placed
by hand for very small trenches.
A special type of trench involves support of the trench wall with a biodegradable
("biopolymer") slurry. The trench is excavated into soil using a biodegradable, viscous fluid to
maintain the stability of the trench. The backfill is placed into the fluid-filled trench. An agent is
introduced to promote degradation of the viscous drilling fluid, which quickly loses much of its
viscosity and allows the granular backfill to attain a high hydraulic conductivity without any
plugging effect from the slurry. This technology allows construction of deep, continuous drainage
trenches but is used much more often for remediation of contaminated sites than in new waste
containment facilities. Further details are given by Day (1990).
5.7 Compaction
Many construction specifications stipulate a minimum percentage compaction for granular
drainage layers. There is rarely a need to compact drainage materials. However, on occasion,
there may be a need to compact a drainage material for one of the following reasons:
198
-------
1. If a settlement-sensitive structure is to be placed on top of the drainage layer, the
drainage layer may need to be compacted to minimize settlement.
2. If dynamic loads might cause loose drainage material to liquefy or settle
excessively, the material may need to be compacted.
3. If the drainage material must have exceptionally high strength, the material may
need to be compacted.
Only in rare instances will the problems listed above be significant. Settlement-sensitive
structures are rarely built on top of liner or cover systems. Liquefaction is rarely an issue because
the hydraulic conductivity of the drainage material is normally sufficiently large to preclude the
possibility of liquefaction. Strength is rarely a problem with granular materials. Reasons not to
compact the drainage layer are as follows:
1. Compacting the drainage material increases the amount of fines in the drainage
material, which decreases hydraulic conductivity.
2. Compacting the drainage layer reduces the porosity of the material, which decreases
hydraulic conductivity.
3. Dynamic compaction stresses may damage underlying geosynthetics.
Unless there is a sound reason why the drainage material should be compacted, it is
recommended that the drainage material not be compacted. The main goal of the drainage layer is
to remove liquids, and this can only be accomplished if the drainage layer has high hydraulic
conductivity. The uncompacted drainage layer may be slightly compressible, but the amount of
compression is expected to be small.
There is a potential problem with drainage layer materials placed on side slopes. In some
situations the friction between the drainage layer and underlying geosynthetic component may not
be adequate to maintain stability of the side slope. CQA personnel should assume that the designer
has analyzed slope stability and designed stable slide slopes for assumed materials and conditions.
However, CQA personnel should be vigilant for evidence of slippage at the interface between the
drainage layer and an underlying geosynthetic component. If problems are noted, the design
engineer should be notified immediately.
5.8 Protection
The main protection required for the drainage layer is to ensure that large pieces of waste
material do not penetrate excessively into the layer and that fines do not contaminate the layer.
Many designs call for placement of protective soil or select waste on top of the leachate collection
layer. As shown in Fig. 5.4, CQA personnel should stand near the working face of the first lift of
solid waste placed on top of a leachate collection layer in a solid waste landfill to observe placement
of select material.
Wind-borne fines may contaminate drainage materials. Soil erosion from adjacent slopes
may also lead to accumulation of fines in the drainage material. The CQA personnel cannot
complete their job until the drainage material is fully covered and protected.
Residual fines may be washed by rain from other soils, or the drainage material itself,
during rain storms and accumulate in low areas. The accumulation of fines in sumps or other low
199
-------
points can reduce the effectiveness of the drainage system. CQC/CQA personnel should be aware
° \Pr°Slem ai£ WftC51°r (1) areas where fmes may be washed into the drainage
* 6y C ^ °i ^ dramage in ^-^g ^ («*. development of ponds
the drainage material in low-lying areas). If excessive fines are washed into a portion
of the drainage matenal, the design engineer should be contacted for further evaluation prior to
covering the drainage matenal by the next successive layer in the system.
Figure 5.4 - CQC and CQA Personnel Observing Placement of Select Waste on Drainage Layer.
200
-------
5.9 References
ASTM D-422, "Particle Size Analysis of Soils"
ASTM D-1987, "Biological Clogging of Geotextile or Soil/Geotextile Filters"
ASTM D-2434, "Permeability of Granular Soils"
ASTM D-4373, "Calcium Carbonate Content of Soils"
Cedergren, H.R. (1989), Seepage, Drainage, and Flow Nets, Third Edition, John Wiley & Sons,
New York, 465 p.
Day, S. R. (1990), "Excavation/Interception Trenches by the Bio-Polymer Slurry Drainage Trench
Technique," Superfund '90, Hazardous Materials Control Research Institute, Silver Spring,
Maryland, pp. 382-385.
201
-------
Chapter 6
Geosynthetic Drainage Systems
6.1 Overview
The collection of liquids in waste containment systems, their drainage and eventual removal
represents an important element in the successful functioning of these facilities. Focus in this
chapter is on the primary and secondary leachate collection systems beneath solid waste and on
surface water and gas removal systems in the cover above the waste. This chapter parallels
Chapter 5 on natural soil drainage materials but now using geosynthetics. Combined systems such
as geocomposites and geospacers are often used; however we will generally focus on the
individual geosynthetic components. The individual materials to be described are the following:
• geotextiles used as filters over various drainage systems (geonets, geocomposites, sands
and gravels)
• geotextiles used for gas collection
• geonets used as primary and/or secondary leachate collection systems, and gas collection
• other geosynthetic drainage systems used as surface water collection systems and
possibly as primary and/or secondary leachate collection systems
The locations of the various geosynthetic materials listed above are illustrated in the sketch of Fig.
6.1.
6.2 Geotexriles
Geotextiles, which some refer to as filter fabrics or construction fabrics, consist of
polymeric yarns (fibers) made into woven or nonwoven textile sheets and supplied to the job site in
large rolls. When ready for placement, the rolls are removed from their protective covering,
properly positioned and unrolled over the substrate material. The substrate upon which the
geotextile is placed is usually a geonet, geocomposite, drainage soil or other soil material. The roll
edges and ends are either overlapped for a specified distance, or are sewn together. After approval
by the CQA personnel, the geotextile is covered with the overlying material. Depending on site
specific conditions, this overlying material can be a geomembrane, geosynthetic clay liner,
compacted clay liner, geonet, or drainage soil.
This section presents the MQA aspects of geotextiles insofar as their manufacturing is
concerned and the CQA aspects as far as handling, seaming and backfilling is concerned.
6.2.1 Manufacturing of Geotexriles
The manufacturing of geotextiles made from polymeric fibers follows traditional textile
manufacturing methods and uses similar equipment. It should be recognized at the outset that most
manufacturing facilities have developed their respective geotextile products to the point where
product quality control procedures and programs are routine and fully developed.
Three discrete stages in the manufacture of geotextiles should be recognized from an MQA
perspective: (1) the polymeric materials; (2) yarn or fiber type; and (3) fabric type (IFAI, 1990).
202
-------
Perforated
Pipe
LEGEND
GT = Geotextile
GN = Geonet
GM = Geomembrane
GCL = Geosynthetic Clay Liner
GC = Geocomposite
CCL = Compacted Clay Liner
Figure 6.1 - Cross Section of a Landfill Illustrating the Use of Different Geosynthetics Involved
in Waste Containment Drainage Systems
-------
6.2.1.1 Resins and Their
AA- • APProximately 75% of geotextiles used today are based on polypropylene resin An
additional 20% are polyester and the remaining 5% is a range of polymers including polyethylene
nylon and others used for specialty purposes. As with all geosynthetics, however; the base resin
has various additives formulated with it resulting in the final compound. Additives for ultraviolet
light protection and as processing aids are common, see Table 6.1.
Table 6.1 - Compounds Used in The Manufacture of Geotextiles (Values Are Percentages Based
on Weight)
Generic Name
Polypropylene
Polyester
Others
Resin
95
97
95
-98
-98
-98
0-3
0-1
1-3
Others
0
0
1
\dditives
-2
-2
-2
• u - t r*Sm 1S *isually suPPlied in the form of pellets which is then blended with carbon black
either m the form of concentrate pellets or chips, or as a powder, and the additive package The
additive package is usually a powder and is proprietary with each particular manufacturer For
some manufacturers, the pellets are precompounded with carbon black and/or the entire additive
package. Figure 6.2 shows polyester chips and carbon black concentrate pellets used in the
manufacturer of polyester geotextiles. Polypropylene pellets and carbon black are similar to those
shown in the manufacture of polyethylene geomembranes. Refer to Chapter 3 for details and in
particular to Section 3.2.2 for use of recycled and/or reclaimed material.
The following items should be considered for a specification or MQA document for resins
and additives used in the manufacture of geotextiles for waste containment applications.
1. The resin should meet MQC requirements. This usually requires a certificate of analysis
to be submitted by the resin vendor for each lot supplied. Included will be various
properties, their specification limits and the appropriate test methods. For
polypropylene resin, the usual requirements are melt flow index, and other properties
telt to be relevant by the manufacturer. For polyester resin, the usual requirements are
intrinsic viscosity, solution viscosity, color, moisture content and other properties felt
to be relevant by the manufacturer.
2. The internal quality control of the manufacturer should be reported to verify that the
geotexnle manufactured for the project meets the proper specifications.
3. The frequency of performing each of the preceding tests should be covered in the MQC
plan and should be implemented and followed.
204
-------
Carbon Black Chips
Figure 6.2 - Polyester Resin Chips (Upper) and Carbon Black Concentrate Pellets (Lower) Used
for Geotextile Fiber Manufacturing
205
-------
4.
The percentage, according to ASTM D-1603, and type of carbon black should be
specified for the particular formulation being used, although it is low in comparison to
geomembranes.
5. The type and amount of stabilizers are rarely specified. If a statement is required it
should signify that the stabilizer package has been successfully used in the past and to
what extent
6.2.1.2 Fiber Types
_ The resin, carbon black and stabilizers are introduced to an extruder which supplies heat,
mixing action and filtering. It then forces the molten material to exit through a die containing many
small orifices called a "spinnerette". Here the fibers, called "yarns", are usually drawn (work
hardened) by mechanical tension, or impinged by air, as they are stretched and cooled. The
resulting yarns, called "filaments", can be wound onto a bobbin, or can be used directly to form
the finished product. Other yarn manufacturing variations include those made from staple fibers
and flat, tape-like, yarns called "slit-film". Each type (filament, staple or slit-film) can be twisted
together with others as shown in Fig. 6.3. Note that "yarn" is a generic term for any continuous
strand (fiber, filament or tape) used to form a textile fabric. Thus all of the examples in Fig. 6.3
are yarns, except for staple, and can be used to manufacture geotextiles.
Slit-film
Monofilament
Yarn
Monofilament
Yam
Multifilament
Yarn
Staple
Yarn
Slit-film
Fibrillated
Yam
Figure 6.3 - Types of Polymeric Fibers Used in the Construction of Different Types of Geotextiles
206
-------
6.2.1.3 Geotextile Types
The yarns just described are joined together to make a fabric, or geotextile. Generic
classifications are woven, nonwoven and knit. Knit geotextiles, however, are rarely used in waste
containment systems and will not be described further in this document.
The manufacturer of a woven geotextile uses the desired type of yarn from a bobbin and
constructs the fabric on a weaving loom. Fabric weaving technology is well established over
literally centuries of development. Most woven fabrics used for geotextiles are "simple", or
"basket-type" weaves consisting of each yarn going over and under an intersecting yarn on an
alternate basis. Figure 6.4(a) shows a micrograph of a typical woven geotextile pattern.
In contrast to this type of, uniformly woven pattern are nonwoven fabrics as shown in Figs.
6.4(b) and (c). Here the yarns are utilized directly from the extruding spinnerette and laid down on
a moving belt in a random fashion. The speed of the moving belt dictates the mass per unit area of
the final product. While positioned on the belt the material is "lofty", and the yarns are not
structurally bound in any way. Two variations of structural bonding can be used, which gives rise
to two unique types of nonwoven geotextiles.
• Nonwoven, needlepunched geotextiles go through a needling process wherein barbed
needles penetrate the fabric and entangle numerous fibers transverse to the plane of the
fabric. Note the fiber entanglement pattern in Fig. 6.4(b). As a post-processing step,
the fabric can be passed over a heated roller resulting in a singed or burnished surface of
the yarns on one or both sides of the fabric.
• Nonwoven, heat bonded geotextiles are formed by passing the unbonded fiber mat
through a source of heat, usually steam or hot air, thereby melting some of the fibers at
various points. Note the fiber bonding pattern in Fig. 6.4(c). This compresses the mat
and simultaneously joins the fibers at their intersections by melt bonding.
6.2.1.4 General Specification Items
There are numerous items recommended for inclusion in a specification or MQA document
for geotextiles used in waste containment facilities.
1. There should be verification arid certification that the actual geotextile properties meet
the manufacturers specification for that particular type and style.
2. Quality control certifications should include, at a minimum, mass per unit area per
ASTM D-5261, grab tensile strength per ASTM D-4632, trapezoidal tear strength per
ASTM D-4533, burst strength per ASTM D-3786, puncture strength per ASTM D-
4833, thickness per ASTM D-5199, apparent opening size per ASTM D-4751, and
permittivity per ASTM D-4491.
3. Values for each property should meet, or exceed, the project specification values, (note
in some cases the property listed is a maximum value in which case lower values are
acceptable).
4. A statement should be included that the property values listed are based upon the
minimum average roll value (MARV) concept.
207
-------
I I LI I 1,1 HI I I| |
111 I LI III III ILI 111 III III I LI III III II
IlIIIIIIIftllLIIIIILIIMIftli&llliil&l
tILIIMILIIlllLIILIifLIILIILIILIILII
111 I 11 I LI I ft I I LI III | LI III | M 11|• | u I *
tl HI lillll III ILIILI Ml I LI ILI I III LI
11 LI 1 II I LI IIIIII 1111 Li 1 II I §1 HI | L| |
IIII il 11»| III I fcl | M 11| I LI I LI | II I LI 11
ill IIIIII & HI II 11II I LI 111 I LI I LI I LI
I I LI I LI I LI i| 111 1I1 I L| l I* § LI I LI I LI I (
I L! I II I LI • LI I LI I Ml LI I LI I LI I LI ILIIL
It III I LI I ft I I I I L I 111 I LI I 1.1 I LI I LI I LI
il Ml LI I LI 1IIMILI ILIILI ILIIUILII
I L I I »I I LI • I I 1.1 I M I M I L I I LI I LI I LI t L
tilII I LI I ft III III I LI I LI III I LI I LI I LI
11 LII LI I LI IIILIILIILIIIIILIILI I LI I
ILIIMILIILIILIIMILIMIIIIIIIILIIL
»IILII»||ft||LIILIILIIL||»| ILIIL9ILI
(a) Woven Geotextile at 4X Magnification
(b) Nonwoven Needlepunched Geotextile at 24X Magnification
Figure 6.4 - Three Major Types of Geotextiles (Continued on Next Page).
208
-------
(c) Nonwoven Heatbonded Geotextile at 24X Magnification
Figure 6.4 - Three Major Types of Geotextiles (Continued from Previous Page)
5. The ultraviolet light resistance should be specified which is usually a certain percentage
of strength or elongation retained after exposure in a laboratory weathering device.
Usually ASTM D-4355 is specified and retention after 500 hours is typically 50% to
90%.
6. The frequency of performing each of the preceding tests should be covered in the
manufacturer's MQC plan and it should be implemented and followed.
7. Verification that needle-punched, nonwoven geotextiles have been inspected
continuously for the presence of broken needles using an in-line metal detector with an
adequate sweep rate should be provided. Furthermore, a needle removal system, e.g.,
magnets, should be implemented.
8. A statement indicating if, and to what extent, reworked polymer, or fibers, was added
during manufacturing. If used, the statement should note that the rework polymer, or
fibers, was of the same composition as the intended product.
9. Reclaimed or recycled, i.e., fibers or polymer that has been previously used, should
not be added to the formulation unless specifically allowed for in the project
209
-------
specifications. Note, however, that reclaimed fibers may be used in geotextiles in
certain waste containment applications. The gas collection layer above the waste and
the geotextile protection layer between drainage stone and a geomembrane are likely
locations. These should be design decisions and should be made accordingly.
6.2.2 Handling: of Geotextiles
A number of activities occur between the manufacture of geotextiles and their final
positioning at the waste facility. These activities involve protective wrapping, storage at the
manufacturing facility, shipment, storage at the site, product acceptance, conformance testing and
final placement at the facility. Each of these topics will be described in this section.
6.2.2.1 Protective Wrapping
All rolls of geotextiles, irrespective of their type, must be enclosed in a protective wrapping
that is opaque and waterproof. The object is to prevent any degradation from atmospheric
exposure (ultraviolet light, ozone, etc.), moisture uptake (rain, snow) and to a limited extent,
accidental damage. It must be recognized that geotextiles are the most sensitive of all geosynthetics
to degradation induced by ultraviolet light exposure. Geotextile manufacturers use tightly wound
plastic wraps or loosely fit plastic bags for this purpose. Quite often the plastic is polyethylene in
the thickness range of 0.05 to 0.13 mm (2 to 5 mil). Several important issues should be
considered in a specification or MQA document.
1. The protective wrapping should be wrapped around (or placed around) the geotextile in
the manufacturing facility and should be included as the final step in the manufacturing
process.
2. The packaging should not interfere with the handling of the rolls either by slings or by
the utilization of the central core upon which the geotextile is wound.
3. The protective wrapping should prevent exposure of the geotextile to ultraviolet light,
prevent it from moisture uptake and limit minor damage to the roll.
4. Every roll must be labeled with the manufacturers name, geotextile style and type, lot
and roll numbers, and roll dimensions (length, width and gross weight). Details
should conform to ASTM D-4873.
6.2.2.2 Storage at Manufacturing Facility
The manufacturing of geotextiles is such that temporary storage of rolls at the
manufacturing facility is necessary. Storage times range from a few days to a year, or longer.
Figure 6.5(a) shows geotextile storage at a manufacturer's facility.
Regarding specification and MQA document items, the following should be considered.
1. Handling of rolls of geotextiles should be done in a competent manner such that
damage does not occur to the geotextile nor to its protective wrapping. In this regard
ASTM D-4873 should be referenced and followed.
2. Rolls of geotextiles should not be stacked upon one another to the extent that
deformation of the core occurs or to the point where accessibility can cause damage in
handling.
210
-------
(a) Storage at Manufacturing Facility
(b) Storage at Field Site
Figure 6.5 - Photographs of Temporary Storage of Geotextiles
211
-------
3. Outdoor storage of rolls at the manufacturer's facility should not be longer than six
months. For storage periods longer than six months a temporary enclosure should be
put over the rolls, or they should be moved to within a enclosed facility.
6.2.2.3 Shipment
Geotextile rolls are shipped from the manufacturer's (or their representatives) storage
facility to the job site via common carrier. Ships, railroads and trucks have all been used
depending upon the locations of the origin and final destination. The usual carrier from within the
USA, is truck. When using flat-bed trucks the rolls are usually loaded by means of a crane with
slings wrapped around the individual rolls. When the truck bed is closed, i.e., an enclosed trailer,
the rolls are usually loaded by fork lift with a "stinger" attached. The "stinger" is a long tapered
rod which fits inside the core upon which the geotextile is wrapped.
Insofar as specification and MQA/CQA documents are concerned the following items
should be considered.
1. The method of loading the geotextile rolls, transporting them and off-loading them at
the job site should not cause any damage to the geotextile, its core, nor its protective
wrapping
2. Any protective wrapping that is accidentally damaged or stripped off of the rolls should
be repaired immediately or the roll should be moved to a enclosed facility until its repair
can be made to the approval of the CQA personnel.
6.2.2.4 Storage at Field Site
Off-loading of geotextile rolls at the site and temporary storage which must be done in an
acceptable manner. Figure 6.5(b) shows typical storage at the field site. Some specification and
CQA document items to consider are the following.
1. Handling of rolls of geotextiles should be done in a competent manner such that
damage does not occur to the geotextile nor to its protective wrapping. In this regard
ASTM D-4873 should be referenced and followed.
2. The location of field storage should not be in areas where water can accumulate. The
rolls should be elevated off of the ground so as not to form a dam creating the ponding
of water.
3. The rolls should be stacked in such a way that cores are not crushed nor is the
geotextile damaged. Furthermore, they should be stacked in such a way that access for
conformance testing is possible.
4. Outdoor storage of rolls should not exceed manufacturers recommendations or longer
than six months, whichever is less. For storage periods longer than six months a
temporary enclosure should be placed over the rolls, or they should be moved within an
enclosed facility.
6.2.2.5 Acceptance and Conformance Testing
Upon delivery of the rolls of geotextiles to the project site, and temporary storage thereof,
the CQA engineer should see that conformance test samples are obtained. These samples are then
212
-------
sent to the CQA laboratory for testing to ensure that the supplied geotextile conforms to the project
plans and specifications. The samples are taken from selected rolls by removing the protective
wrapping and cutting full-width, 1 m (3 ft) long samples off of the outer wrap of the selected
roll(s). Sometimes the outer revolution of geotextile is discarded before the test sample is taken.
The rolls are immediately re-wrapped and replaced in temporary field storage. The samples rolls
must be relabeled for future identification. Alternatively, conformance testing could be performed
at the manufacturer's facility and when completed the particular lot should be marked for the
particular site under investigation. Items to be considered in a specification and CQA documents in
this regard are the following:
1. The samples should be identified by type, style or, lot and roll numbers. The machine
direction should be noted on the sample(s) with a waterproof marker.
2. A lot is defined as a unit of production, or a group of other units or packages having
one or more common properties and being readily separable from other similar units.
Other definitions are also possible and should be clearly stated in the CQA documents,
seeASTMD-4354.
3. Sampling should be done according to the job specification and/or CQA documents.
Unless otherwise stated, sampling should be based on one per lot. Note that a lot is
sometimes defined as 10,000 m2 (100,000 ft2) of geotextile. Utilization of ASTM D-
4354 may be referenced and followed in this regard but it might result in a different
value for sampling than stated above.
4. Testing at the CQA laboratory may include mass per unit area per ASTM D-5261, grab
tensile strength per ASTM D-4632, trapezoidal tear strength per ASTM D-4533, burst
strength per ASTM D-3786, puncture strength per ASTM D-4833, and possibly
apparent opening size per ASTM D-4751, and permittivity per ASTM D-4491. Other
conformance tests may be required by the project specifications.
5. Conformance test results should be sent to the CQA engineer prior to deployment of
any geotextile from the lot under review.
6. The CQA engineer should review the results and should report any nonconformance to
the Owner/Operator's Project Manager.
7. The resolution of failing conformance tests must be clearly stipulated in the
specifications or CQA documents. Statements should be based upon ASTM D-4759
entitled "Determining the Specification Conformance of Geosynthetics".
8. The geotextile rolls which are sampled should be immediately rewrapped in their
protective covering to the satisfaction of the CQA personnel.
6.2.2.6 Elacement
The geosynthetic installation contractor should remove the protective wrappings from the
geotextile rolls to be deployed only after the substrate layer, soil or other geosynthetic, has been
documented and approved by the CQA personnel. The specification and CQA documents should
be written in such a manner as to ensure that the geotextiles are not damaged nor excessively
exposed to ultraviolet degradation. The following items should be considered for inclusion in a
specification or CQA document
213
-------
1. The installer should take the necessary precautions to protect the underlying layers upon
which the geotextile will be placed. If the substrate is soil, construction equipment can
be used provided that excess rutting is not created. Excess rutting should be clearly
defined and quantified by the design engineer. In some cases 25 mm (1.0 in.) is the
maximum rut depth allowed. If the ground freezes, the depth of ruts should be further
reduced to a specified value. If the substrate is a geosynthetic material, deployment
must be by hand, by use of small jack lifts on pneumatic tires having low ground
contact pressure, or by use of all-terrain vehicles, ATV's, having low ground contact
pressure.
2. During placement, care must be taken not to entrap (either within or beneath the
geotextile) stones, excessive dust or moisture that could damage a geomembrane,
cause clogging of drains or filters, or hamper subsequent seaming.
3. On side slopes, the geotextiles should be anchored at the top and then unrolled so as to
keep the geotextile free of wrinkles and folds.
4. Trimming of the geotextiles should be performed using only an upward cutting hook
blade.
5. Npnwoven geotextiles placed on textured geomembranes can be troublesome due to
sticking and are difficult to align or even separate after they are placed on one another.
A thin sheet of plastic on the geomembrane during deployment of the geotextile can be
very helpful in this regard. Of course, it is removed after correct positioning of the
geotextile.
6. The geotextile should be weighted with sandbags, or the equivalent, to provide
resistance against wind uplift. This is a site-specific procedure and completely the
installer's decision. Uplifted and moved geotextiles can generally be reused but only
after approval by the owner and observation by the CQA personnel.
7. A visual examination of the deployed geotextile should be carried out to ensure that no
potentially harmful objects are present, e.g., stones, sharp objects, small tools,
sandbags, etc.
6.2.3 Seaming
Seaming of geotextiles, by sewing, is sometimes required (versus overlapping with no
sewn seams) of all geotextiles placed in waste facilities. This generally should be the case for
geotextiles used in filtration, but may be waived for geotextiles used in separation (e.g., as gas
collection layers above the waste or as protective layers for geomembranes) as per the plans and
specifications. In such cases, heat bonding is also an acceptable alternate method of joining
separation geotextiles. In cases where overlapping is permitted, the overlapped distance
requirements should be clearly stated in the specification and CQA documents. Geotextile seam
types and procedures, seam tests and geotextile repairs are covered in this section.
6.2.3.1 Seam Types and Procedures
The three types of sewn geotextile seams are shown in Fig. 6.6. They are the "flat" or
"prayer" seam, the "J" seam and the "butterfly" seam. While each can be made by a single thread,
or by a two-thread chain stitch, as illustrated, the latter stitch is recommended. Furthermore, a
single, double, or even triple, row of stitches can be made as illustrated by the dashed lines in the
214
-------
figures. Figure 6.7 shows a photograph of the fabrication of a flat seam and see Diaz (1990) fat
further details regarding geotextile seaming.
SSa-l
SSn-1
SSd-1
SSa-2 SSa-3
"Hat" or "Prayer" Seam
SSn-2 SSn-3
"J" Seam
SSd-2
"Butterfly" Seam
"101" Single Thread Chainstitch
'401" Two-Thread Chainstitch
Figure 6.6 - Various Types of Sewn Seams for Joining Geotextiles (after Diaz, 1990)
215
-------
Figure 6.7 - Fabrication of a Geotextile Field Seam in a "Flat" or "Prayer" Seam Type
The project specification or CQA documents should address the following considerations.
1. The type of seam, type of stitch, stitch count or number of stitches per inch and number
of rows should be specified based on the tendency of the fabric to fray, strength need
and toughness of the fabric. For filtration and separation geotextiles a flat seam using a
two-thread chain stitch and one row is usually specified. For reinforcement geotextiles,
stronger and more complex seams are utilized. Alternatively, a minimum seam
strength, per ASTM D-4884, could be specified.
2. The seams should be continuous, i.e., spot sewing is generally not allowed.
3. On slopes greater than approximately 5 (horiz.) to 1 (vert.), seams should be
constructed parallel to the slope gradient. Exceptions are permitted for small patches
and repairs.
4. The thread type must be polymeric with chemical and ultraviolet light resistant
properties equal or greater than that of the geotextile itself.
216
-------
5. The color of the sewing thread should contrast that of the color of the geotextile for
ease in visual inspection. This may not be possible due to polymer composition in
some cases.
6. Heat seaming of geotextiles may be permitted for certain seams. A number of methods
are available such as hot plate, hot knife and ultrasonic devices.
7. Overlapped seams of geotextiles may be permitted for certain seams. The overlap
distance should be stated depending on the site specific conditions.
6.2.3.2 Seam Tests
For geotextiles used in filtration and separation, seam samples and subsequent strength
testing are not generally required. If they are, however, they should be stipulated in the
specifications or CQA documents. Also, the sampling and testing frequency should be noted
accordingly. The test method to evaluate sewn seam test specimens is ASTM D-4884.
6.2.3.3 Repairs
Holes, or tears, in geotextiles made during placement or anytime before backfilling should
be repaired by patching. Some relevant specifications and CQA document items follow.
1. The patch material used for repair of a hole or tear should be the same type of polymeric
material as the damaged geotextile, or as approved by the CQA engineer.
2. The patch should extend at least 30 cm (12 in.) beyond any portion of the damaged
geotextile.
3. The patch should be sewn in place by hand or machine so as not to accidentally shift
out of position or be moved during backfilling or covering operations.
4. The machine direction of the patch should be aligned with the machine direction of the
geotextile being repaired.
5. The thread should be of contrasting color to the geotextile and of chemical and
ultraviolet light resistance properties equal or greater than that of the geotextile itself.
6. The repair should be made to the satisfaction of the specification and CQA documents.
6.2.4 Backfilling or Covering
The layer of material placed above the deployed geotextile will be either soil, waste or
another geosynthetic. Soils will vary from compacted clay layers to coarse aggregate drainage
layers. Waste should be what is referred to as "select" waste, i.e., carefully separated and placed
so as not to cause damage. Geosynthetics will vary from geomembranes to geosynthetic clay
liners. Some considerations for a specification and CQA document to follow:
1. If soil is to cover the geotextile it should be done such that the geotextile is not shifted
from its intended position and underlying materials are not exposed or damaged.
2. If a geosynthetic is to cover the geotextile, both the underlying geotextile and the newly
deployed material should not be damaged during the process.
217
-------
3. If solid waste is to cover the geotextile, the type of waste should be specified and visual
observation by CQA personnel should be required.
4. The overlying material should not be deployed such that excess tensile stress is
mobilized in the geotextile. On side slopes, this requires soil backfill to proceed from
the bottom of the slope upward.
5. Soil backfilling or covering by another geosynthetic, should be done within the time
frame stipulated for the particular type of geotextile. Typical time frames for geotextiles
are within 14 days for polypropylene and 28 days for polyester geotextiles.
6.3 Geonets and Geonet/Geotextile Geocomposites
Geonets are unitized sets of parallel ribs positioned in layers such that liquid can be
transmitted within their open spaces. Thus their primary function is drainage; recall Fig. 6.1.
Figure 6.8(a) shows a photograph of rolls of geonets, while Fig. 6.8(b) shows a closeup of the
intersection of a typical set of geonet ribs. Note that open space exists both in the plane of the
geonet (above or under the parallel sets of ribs) and cross plane to the geonet (within the apertures
between adjacent^sets of ribs). In all cases, the apertures must be protected against migration and
clogging by adjafcen$.soil materials. Thus geonets always function with either geomembranes
and/or geotextiles on their two planar surfaces. Whenever the geonet conies supplied with a
geotextile on one or both of its surfaces, it is called a geocomposite. The geotextile(s) is usually
bonded on the surface by heat fusing or by using an adhesive.
This section will describe the manufacturing and handling of geonets for waste containment
facilities. Since continuity of liquid flow is necessary at the sides and ends of the rolls, joining
methods will also be addressed, as will the placement of the covering layer. Also covered will be
the bonding of geotextiles to geonets in the form of drainage geocomposites.
6.3.1 Manufacturing of Geonets
Geonets currently used in waste containment applications are formed using an extruder
which accepts the intended polymer formulation and then melts, mixes, filters and feeds the molten
material directly into a counter-rotating die. This die imparts parallel sets of ribs into the preform.
Upon exiting the die, the ribs of the preform are opened by being forced over a steel spreading
mandrel. Figure 6.9 shows a small laboratory size geonet as it is formed and expands into its final
shape. The fully formed geonet is then water quenched, longitudinally cut in the machine
direction, spread open as it exits the quench tank and rolled onto a handling core. The width of the
rolls are determined by the maximum circumference of the spreading mandrel. Since the process is
continuous in its operation, the roll length is determined on the basis of the manageable weight of a
roll. The thickness of the geonet is based on the slot dimensions of the opposing halves of the
counter-rotating mold. Thicknesses of commercially available geonets vary between 4.0 and 6.9
mm (160 - 270 mils).
Most of the commercially available resins used for geonets are polyethylene in the natural
density range of 0.934 to 0.940 g/cc. Thus they are classified as medium density polyethylene
according to ASTM D-1248. The final compound is approximately 97% polyethylene. An
additional 2 to 3% is carbon black, added as a powder or as a concentrate, and the remaining 0.5 to
1.0% are additives. The additives are added as a powder as are antioxidants and processing aids,
both of which are proprietary to the various geonet manufacturers. Formulations are often the
same as for HDPE geomembranes (recall Chapter 3), or slight variations thereof.
218
-------
(a) Rolls of Drainage Geonets
Geonets
(b) Closeup of Rib Intersection
Figure 6.8 - Typical Geonets Used in Waste Containment Facilities
219
-------
Polymer Feed
to
Spreading Mandrel
and
Quench Tank •
Figure 6.9 - Counter Rotating Die Technique (Left Sketch) for Manufacturing Drainage Geonets
and Example of Laboratory Prototype (Right Photograph)
-------
Regarding the preparation of a specification or MQA document for the resin component of
HDPE geonets, the following items should be considered:
1. Specifications may call for the polyethylene resin to be made from virgin,
uncontaminated ingredients. Alternatively, geonets can be made with off-spec
geomembrane material as a large, or even major part, of their total composition provided
this material is of the same formulation as the intended geonet and does not consist of
recycled and/or reclaimed material. Recycled and/or reclaimed material is generally not
allowed. It is acceptable, and is almost always the case, that the density of the resin is in
the medium density range for polyethylene, i.e., that its density is equal to or less than
0.940 g/cc.
2. Typical quality control tests on the resin are density, via ASTM D-1505 or D-792 and
melt flow index via ASTM D-1238.
3. An HDPE geonet formulation should consist of at least 97% of polyethylene resin, with
the balance being carbon black and additives. No fillers, extenders, or other materials
should be mixed into the formulation.
4. It should be noted that by adding carbon black and additives to the resin, the density of
the final formulation is generally over 0.941 g/cc. Since this value is in the high density
polyethylene category, according to ASTM D-1248, geonets of this type are customarily
referred to as high density polyethylene (HDPE).
5. Regrind or reworked polymer which is previously processed HDPE geonet in chip
form, is often added to the extruder during processing. It is acceptable if it is the same
formulation as the geonet being produced.
6. No amount of "recycled" or "reclaimed" material, which has seen prior use in another
product should be added to the formulation.
7. An acceptable variation of the process just described is to add a foaming agent into the
extruder which then is processed in the standard manner. As the geonet is formed and is
subsequently quenched, the foaming agent expands within the ribs creating innumerable
small spherical voids. The voids are approximately 0.01 mm (0.5 mil) in diameter.
This type of geonet is called a "foamed rib" geonet, in contrast to the standard type
which is a "solid rib" geonet. Foamed rib geonets are currently seen less frequently in
drainage systems than previously.
8. Quality control certificates from the manufacturer should include proper identification of
the product and style and results of quality control tests.
9. The frequency of performing each of the preceding tests should be covered in the MQC
plan and it should be implemented and followed.
6.3.2 Handling of Geonets
A number of activities occur between the manufacture of geonets and their final positioning
where intended at the waste facility. These activities involve packaging, storage at the
manufacturing facility, shipment, storage at the site, acceptance and conformance testing and final
placement at the facility. Each of these topics will be described in this section.
221
-------
6.3.2.1 Packaging
As geonets come from the quenching tank they are wound on a core until the desired length
is reached. The geonet is then cut along its width and the entire roll contained by polymer straps so
as not to unwind during subsequent handling. There is generally no protective wrapping placed
around geonets, however, a plastic wrapping can be provided if necessary.
Specifications or a MQA document should be formed around a few important points.
1. The core must be stable enough to support the geonet roll while it is handled by either
slings around it, or from a fork lift "stinger" inserted in it.
2. The core should have a minimum 100 mm (4.0 in.) inside diameter.
3. The banding straps around the outside of the roll should be made from materials with
adequate strength yet should not damage the outer wrap(s) of the roll.
6.3.2.2 Storage at Manufacturing Facility
Tw The storage of geonet rolls at the manufacturer's facility is similar to that described for
HDPE geomembranes. Refer to Section 3.3.1 for a complete description.
6.3.2.3 Shipment
The shipment of geonet rolls from the manufacturer's facility to the project site is similar to
that described for HDPE geomembranes. Refer to Section 3.3.2 for a complete description.
6.3.2.4 Storage at the Site
The storage of geonet rolls at the project site is similar to that described with HDPE
geomembranes. Refer to section 3.3.2 for a complete description, see Fig. 6.10. An important
exception is that a ground cloth should be placed under the geonets if they are stored on soil for
any time longer than one month. This is to prevent weeds from growing into the lower rolls of the
geonet. If weeds do grow in the geonet during storage, the broken pieces must be removed by
hand on the job when the geonet is deployed.
6.3.2.5 Acceptance and Confnrmance Testing
The acceptance and conformance testing of geonets is similar to that described for HDPE
geomembranes. Refer to Section 3.3.3 for a complete description. For geonets, the usual
conformance tests are the following:
• density, per ASTM D-1505 or D-792
• mass per unit area, per ASTM D-5261
• thickness, per ASTM D-5199
Additional conformance tests such as compression per ASTM D-1621 and transmissivitv per
ASTM D-4716 may also be stipulated.
222
-------
Figure 6.10 - Geonets Being Temporarily Stored at the Job Site
6.3.2.6 Placement
The placement of geonets in the field is similar to that described for geotextiles. Refer to
Section 6.2.2.6 for a complete description.
6.3.3 Joining of Geonets
Geonets are generally joined together by providing a stipulated overlap and using plastic
fasteners or polymer braid to tie adjacent ribs together at minimum intervals, see Fig. 6.11.
Recommended items for a specification or CQA document on the joining of geonets include
the following:
1. Adjacent roll edges of geonets should be overlapped a minimum distance. This is
typically 75-100 mm (3-4 in.).
2. The roll ends of geonets should be overlapped 150-200 mm (6-8 in.) since flow is
usually in the machine direction.
223
-------
Figure 6.11 - Photograph of Geonet Joining by Using Plastic Fasteners
3. All overlaps should be joined by tying with plastic fasteners or polymeric braid.
Metallic ties or fasteners are not allowed.
4. The tying devices should be white or yellow, as contrasted to the black geonet, for ease
of visual inspection.
5. The tying interval should be specified. Typically tie intervals are every 1.5 m (5.0 ft)
along the edges and every 0.15 m (6.0 in.) along the ends and in anchor trenches.
6. Horizontal seams should not be allowed on side slopes. This requires that the length of
the geonet should be at least as long as the side slope, anchor trench and a minimum run
out at the bottom of the facility. If horizontal seams are allowed, they should be
staggered from one roll to the adjacent roll.
7. In difficult areas, such as corners of side slopes, double layers of geonets are
sometimes used. This should be stipulated in the plans and specifications.
8. If double geonets are used, they should be layered on top of one another such that
interlocking does not occur.
224
-------
9. If double geonets are used, roll edges and ends should be staggered so that the joints
do not lie above one another.
10. Holes or tears in the geonet should be repaired by placing a geonet patch extending a
minimum of 0.3 m (12 in.) beyond the edges of the hole or tear. The patch should be
tied to the underlying geonet at 0.15 m (6.0 in.) spacings.
11. Holes or tears along more than 50% of the width of the geonet on side slopes should
require the entire length of geonet to be removed and replaced.
6.3.4 Geonet/Geotextile Geocomposites
Geonets are always covered with either a geomembrane or a geotextile, i.e., they are never
directly soil covered since the soil particles would fill the apertures of the geonet rendering it
useless. Many geonets have a geotextile bonded to one, or both, surfaces. These are then referred
to as geocomposites in the geonet manufacturer's literature. In this document, however,
geocomposites will refer to many different types of drainage core structures. Clearly, covered
geonets are included in this group. However, geocomposites also consist of fluted, nubbed and
cuspated cores, covered with geotextiles and/or geomembranes and will be described separately in
section 6.4. Still further, some manufacturers refer to the entire group of geosynthetic drainage
materials as "geospacers".
Regarding a specification or CQA document for geonet/geotextile drainage geocomposites,
a few comments are offered:
1. The geotextile(s) covering a geonet should be bonded together in such a way that
neither component is compromised to the point where proper functioning is impeded.
Thus adequate, but not excessive, bonding of the geotextile(s) to the geonet is
necessary.
2. If bonding is by heating, the geotextile(s) strength cannot be compromised to the point
where failure could occur. The transmissivity under load test, ASTM D-4716, should
be performed on the intended geocomposite product.
3. If bonding is by adhesives, the type of adhesive must be identified, including its water
solubility and organic content. Excessive adhesive cannot be used since it could fill up
some of the geonet's void space. The transmissivity under load test, ASTM D-4716,
should be performed on the intended geocomposite product. The geotextile's
permittivity could be evaluated using ASTM D-4491.
4. If the shear strength of the geotextile(s) to the geonet is of concern an adapted form of
an interface shear test, e.g., ASTM D-5321, can be performed with the geotextile firmly
attached to a wooden substrate, or other satisfactory arrangement. Alternatively, a ply
adhesion test may be adequate, see ASTM D-413 which might be suitably modified for
geotextile-to-geonet adhesion.
5. For factory fabricated geocomposites with geotextiles placed on both sides of a geonet,
the geonet must be free from all dirt, dust and accumulated debris before covering.
225
-------
6. For field placed geotextiles, the'geonet should be free of all soil, dust and accumulated
debris before covering with a geomembrane or geotextile. In extreme cases this may
require washing of the geonet to accumulate the paniculate material at the low end
(sump) area where it is subsequently removed by hand.
7. When placing geosynthetic clay liners (GCLs) above geocomposites, cleanliness is
particularly important in assuring that fugitive bentonite clay particles do not find their
way into the geonet
8. Placement of a covering geomembrane should not shift the geotextile or geocomposite
out of position nor damage the underlying geonet.
9. An overlying geomembrane or geotextile should not be deployed such that excess
tensile stress is mobilized in the geocomposite.
6.4 Other Types of Geocompnsites
Geocomposite drainage systems consist of a polymer drainage core protected by a geotextile
acting as both a filter and a separator to the adjacent material. Thus a geonet, with a geotextile
attached to one surface or to both surfaces as described in section 6.3.4, is indeed a drainage
geocomposite. However, for the drainage geocomposites discussed in this section the geotextile
filter is always attached to the drainage core and the core can take a wide variety of non-geonet
shapes and configurations. In some cases, the geotextile is only on one side of the core (the side
oriented toward the inflowing liquid), in other cases it is wrapped completely around the drainage
i?m*A **
core.
< There are three different types of drainage geocomposites referred to in this document; sheet
drains, edge drains and strip (or wick) drains. Typical variations are shown in Fig. 6.12. For
drainage systems associated with waste containment facilities, sheet drains, Fig. 6.12a, are
sometimes used as surface water collectors and drains in cover systems of closed landfills and
waste piles, refer to Fig. 6.1. Infiltration water that moves within the cover soil enters the sheet
drain and flows gravitationally to the edge of the site (or cell) where it is generally collected by a
perforated pipe, or edge drain. Pipes will be discussed separately in Chapter 8. The other
possible use for sheet drains is for primary leachate collection systems in landfills. The required
flow rate in some landfills is too great for a geonet, hence the greater drainage capacity of a
geocomposite is sometimes required. Of course, when used in this application the drainage
geocomposite must resist the compressive and shear stresses imposed by the waste and it must be
chemically resistant to the leachate, but these are design considerations. The use of strip (wick)
drains, Fig. 6.12b, in waste containment has been as vertical drains within a solid waste landfill to
promote leachate communication between individual lifts. The edge drains, shown in Fig. 6.12(c)
have potential applicability around the perimeter of a closed landfill facility to accumulate the
surface water coming from a cap/closure system. A variety of perimeter drains could utilize such
geocomposite edge drains.
Of the different types of drainage geocomposites shown in Fig. 6.12, only sheet drains will
be described since they have the greatest applicability in waste containment systems.
226
-------
(a) Geocomposite Sheet Drains
I i i . t . i . t.. j I« . < I i . 11 i i ...t« • i t i i i I t i i l.j-i i I i
...,......
0 1-2 9 "4' .5 " • '6 '• - •"> - Ji 9. ' 10- ' 11 12 I? • 1*" If
(b) Geocomposite Strip (Wick) Drains
Figure 6.12 - Various Types of Drainage Geocomposites (Continued on Next Page)
227
-------
(c) Geocomposite Edge Drains
Figure 6.12 - Various Types of Drainage Geocomposites (Continued from Previous Page)
6A1 Manufacturing of Drainage Composites
The manufacture of the drainage core of a geocomposite sheet drain is generally
accomplished by taking the desired type of polymer sheet and then vacuum forming dimples,
protrusions or cuspations which give rise to the protrusions. The polymer sheets of drainage
geocomposites have been made from a wide variety of polymers. Commercial products that are
currently available consist of the following polymer formulations:
• polystyrene
• nylon
• polypropylene
• polyvinyl chloride
• polyethylene
• polyethylene/polystyrene/polyethylene (coextrusion)
228
-------
With coextrasion there exists a variety of possibilities in addition to those listed above. Recognize,
however, that coarse fibers, entangled webs, filament mattings, and many other variations are also
possible.
Upon deciding on the proper type and thickness of polymer sheet, a geocomposite core
usually goes through a vacuum forming step. In this step a vacuum draws portions of the polymer
sheet into cusps at prescribed locations. Depending on the particular product, the protrusions are at
12 to 25 mm (0.5 to 1.0 in.) centers and are of a controlled depth and shape. Figure 6.13 shows a
sketch of a vacuum forming system. In many of the systems the protrusions are tapered for ease in
manufacturing during release of the vacuum and for a convenient male-to-female coupling of the
edges and/or ends of the product in the field. The different types of drainage geocomposites are
made in either continuous rolls or in discrete panels.
Infrared Heaters
-------
used and the site specific design will dictate the actual selection. As far as the MQA/CQA of the
geotextile it is the same as was described in Section 6.2. v~/v,v
* speciflcation or MQA document f°r
1. There should be verification and certification that the actual geocomposite core
properties meet the manufacturers specification for that particular type and style.
2. Quality control certificates should include at a minimum, polymer composition,
thickness of sheet per ASTM D-5199, height of raised cusps, spacing of cusps
?S2^(!o?enS?1 behavior (both strength and deformation values at core failure) per
Ab 1M D-1621, and transmissivity using site specific conditions per ASTM D-4716.
3. For drainage systems consisting of coarse fibers, entangled webs and/or filament
TlS!rg^^ftlckne^s under load Per AS™ D-5199 and transmissivity under load per
ASTM D-47 16 are the main tests for QC purposes.
4. Values for each property should meet, or exceed, the manufacturers listed values or the
project specification values, whichever are higher.
5. A statement indicating if, and to what extent, regrind polymer was added during
manufacturing. No amount of reclaimed polymer should be allowed.
6 . The frequency of performing each of the preceding tests should be covered in the MQC
plans and it should be implemented and followed.
dnC»m™?fn!Tally' t*^? ffseveral items which should be included in a specification or MQA
document for the geotexnle(s)/dramage core geocomposite.
1 . The type of geotextile(s) should be identified and properly evaluated. See section 6 2
for these details.
2. For strip (wick) drains and edge drains, see Figs. 6.12(b) and (c) respectively the
geotextile complete surrounds the drainage core and generally no fixity is required For
sheet drains, Fig. 6.12(a), this is not the case.
3. The geotextile(s) covering of a drainage core should be bonded in such a way that
neither component is compromised to the point where proper functioning is impeded
Ihus adequate, but not excessive, bonding of the geotextile(s) to the drainage core is
necessary. °
4. If bonding is by heating, the geotextile(s) strength cannot be compromised to the point
where failure could occur. The transmissivity under load test, ASTM D-4716, should
be performed on the intended geocomposite product.
5. If bonding is by adhesives, the type of adhesive must be identified, including its water
solubility and organic content. Excessive adhesive cannot be used since it could fill up
^Tl °*th® drainage core's void space. The transmissivity under load test, ASTM D-
4/lo, should be performed on the intended geocomposite product. The eeotextile's
permittivity could be evaluated using ASTM D-449 1 .
230
-------
6. If the shear strength of the geotextile(s) to the core is of concern an adapted form of an
interface shear test, e.g., ASTM D-5321, can be performed with a wooden substrate, or
other satisfactory arrangement. Alternatively, a ply adhesion test may be adequate, see
ASTM D-413 which might be suitably modified for geotextile-to-core adhesion.
7. For factory fabricated geocomposites with geotextiles placed on both sides of the
drainage core, the core must be free from all dirt, dust and accumulated debris before
covering.
6.4.2 Handling of Drainage Geocomposites
A number of activities occur between the manufacture of drainage geocomposites and their
final positioning where intended at the waste facility. These activities involve packaging, storage at
the manufacturing facility, shipment, storage at the site, acceptance and conformance testing, and
final placement at the facility. Each of these topics will be described although most will be by
reference to the appropriate geotextile section.
6.4.2.1 Packaging
Usually a manufacturer will not attach the geotextile to the core until an order is received
and shipment is imminent. Thus warehousing is not a major issue. The cores are either rolled
onto themselves or are laid flat if they are in panel form. When an order is received, the geotextile
is bonded to the core, the rolls are banded together with polymer straps and, if panels, they are
banded in a similar manner.
6.4.2.2 Storage at Manufacturing Facility
Storage of the drainage cores at the manufacturing facility is usually not a major issue. The
cores are generally stored indoors and are thus protected from atmospheric conditions.
6.4.2.3 Shipment
Shipment of drainage geocomposites (with the geotextile attached) is quite simple due to the
light weight of these geosynthetics compared to other types. The text in Section 6.2.2.3 should be
utilized, however, since accidental damage can always occur.
6.4.2.4 Storage at Field Site
The storage of drainage geocomposites at the project site is similar to that described for
geotextiles, recall Section 6.2.2.4.
6.4.2.5 Acceptance and Conformance Testing
The acceptance and conformance testing of the geotextile portion of a drainage
geocomposite is the same as described in Section 6.2.2.5. The acceptance and conformance
testing of the core portion of a drainage geocomposite is project specific with the exception of the
conformance tests themselves which are different. The recommended conformance tests for
geocomposite drainage cores are the following:
• thickness of sheet per ASTM D-5199 or thickness of the geocomposite per ASTM D-
5199
231
-------
• thickness of raised cusps per ASTMD-1621
• spacing of raised cusps per ASTM D-1621
Optional conformance tests such as compression per ASTM D-1621 and transmissivity per ASTM
S™ , f ? ma? stipulated. The frequency of conformance tests of the drainage core must be
stipulated. In general, one test per 5,000 m^ (50,000 ft2) should be the minimum test frequency.
6.4.2.6 Placement
6-4.3 Joining of Drainage Geocomposite^
Drainage geocomposites are usuaUy joined together by folding back the geotextile from the
lower core and inserting it into the bottom void space of the upper core, see Fig 6. 14 Where this
is not possible a tab should be available at the edges of the core material for the purpose of
overlapping The geotextile must be refolded over the connection area assuring a complete
covering of the core surface. v
Figure 6.14 - Photograph of Drainage Core Joining via Male-to-Female Interlock
232
-------
Recommended items for a specification or CQA document on the joining of drainage
geocomposites include the following:
1. Adjacent edges of drainage cores should be overlapped for at least two rows of cusps.
2. The ends of drainage cores (in the direction of flow) should be overlapped for at least
four rows of cusps.
3. The geotextiles covering the joined cores must provide a complete seal against backfill
soil entering into the core.
4. Horizontal seams should not be allowed on sideslopes. This requires that the drainage
geocomposite be provided in rolls which are at least as long as the side slope.
5. Holes or tears in drainage cores are repaired by placing a patch of the same type of
material over the damaged area. The patch should extend at least four cusps beyond the
edges of the hole or tear.
6. Holes or tears of more than 50% of the width of the drainage core on side slopes should
require the entire length of the drainage core to be removed and replaced.
7. Holes or tears in the geotextile covering the drainage core should be repaired as
described in Section 6.2.3.3.
6.4.4 Covering
Drainage geocomposites, with an attached geotextile, are covered with either soil, waste or
in some cases a geomembrane. Regarding a specification or CQA document some comments
should be included.
1. The core of the drainage geocomposite should be free of soil, dust and accumulated
debris before backfilling or covering with a geomembrane. In extreme cases this may
require washing of the core to accumulate the paniculate material to the low end (sump)
area for removal.
2. Placement of the backfilling soil, waste or geomembrane should not shift the position of
the drainage geocomposite nor damage the underlying drainage geocomposite,
geotextile or core.
3. When using soil or waste as backfill on side slopes, the work progress should begin at
the toe of the slope and work upward.
6.5 References
ASTM D-413, "Rubber Property-Adhesion to Flexible Substrate" . .
ASTM D-792, "Specific Gravity and Density of Plastics by Displacement"
ASTM D-1238, "Flow Rates of Thermoplastics by Extrusion Plastometer"
ASTM D-1248, "Polyethylene Plastics and Extrusion Materials"
233
-------
ASTM D-1505, "Density of Plastics by the Density-Gradient Technique"
ASTM D-1603, "Carbon Black in Olefin Plastics"
ASTM D-1621, "Compressive Properties of Rapid Cellular Plastics"
ASTM D-3786, "Hydraulic Bursting Strength of Knitted Goods and Nonwoven Fabrics:
Diaphragm Bursting Strength Tester Method"
ASTM D-4354, "Sampling of Geosynthetics for Testing"
ASTM D-4355, "Deterioration of Geotextiles from Exposure to Ultraviolet Light and Water
(Xenon-Arc Type Apparatus)"
ASTM D-4491, "Water Permeability of Geotextiles by Permittivity"
ASTM D-4533, "Trapezoidal Tearing Strength of Geotextiles"
ASTM D-4632, "Breaking Load and Elongation of Geotextiles (Grab Method)"
ASTM D-4716, "Constant Head Hydraulic Transmissivity (In-Plane Flow) of Geotextiles and
Geotextile Related Products"
ASTM D-4751, "Determining the Apparent Opening Size of a Geotextile"
ASTM D-4759, "Determining the Specification Conformance of Geosynthetics"
ASTM D-4833, "Index Puncture Resistance of Geotextiles, Geomembranes and Related Products"
ASTM D-4873, "Identification, Storage and Handling of Geosynthetics"
ASTM D-4884, "Seam Strength of Sewn Geotextiles"
ASTM D-5199, "Measuring Nominal Thickness of Geotextiles and Geomembranes"
ASTM D-5261, "Measuring Mass Per Unit Area of Geotextiles"
ASTM D-5321, "Determining the Coefficient of Soil and Geosynthetic or Geosynthetic and
Geosynthetic Friction by the Direct Shear Method"
Diaz, V. A. (1990), "The Seaming of Geosynthetics," IFAI Publ., St. Paul, MN, 1990.
IFAI (1990), "A Design Primer: Geotextiles and Related Materials," Industrial Fabrics Association
International, St. Paul, MN.
234
-------
Chapter 7
Vertical Cutoff Walls
7.1 Introduction
Situations occasionally arise in which it is necessary or desirable to restrict horizontal
movement of liquids with vertical cutoff walls. Examples of the use of vertical cutoff walls include
the following:
1. Control of ground water seepage into an excavated disposal cell to maintain stable side
slopes or to limit the amount of water that must be pumped from the excavation during
construction (Fig. 7.1).
2. Control of horizontal ground water flow into buried wastes at older waste disposal sites
that do not contain a liner (Fig. 7.2).
3. Provide a "seal" into an aquitard (low-permeability stratum), thus "encapsulating" the
waste to limit inward movement of clean ground water in areas where ground water is
being pumped out and treated (Fig. 7.3). -
4. Long-term barrier to impede contaminant transport (Fig. 7.4).
Vertical walls are also sometimes used to provide drainage. Drainage applications are
discussed in Chapters 5 and 6.
Pumps Lower Ground
Water Level Beneath
Excavated Cell
Slurry Wai Restricts Water
Flow into the Cell
Figure 7.1- Example of Vertical Cutoff Wall to Limit Flow of Ground Water into Excavation.
235
-------
Figure 7.2 - Example of Vertical Cutoff Wall to Limit Flow of Ground Water through Buried
Waste.
fc.;j^v''£'w:^
•VA/A:Vv'.-vX^-vGrourid Water Lowered from &&&••#£••£&&
MtititiJtitiFump and Treat Remediation WW&y&y*
Figure 7.3 - Example of Vertical Cutoff Wall to Restrict Inward Migration of Ground Water.
Figure 7.4 - Example of Vertical Cutoff Wall to Limit Long-Term Contaminant Transport.
236
-------
7.2 Types of Vertical Cutoff Walls
The principal types of vertical cutoff walls are sheet pile walls, geomembrane walls, and
slurry trench cutoff walls. Other techniques, such as grouting and deep soil mixing, are also
possible, but have rarely been used for waste containment applications.
7.2.1 Sheet Pile Walls
Sheet pile walls are interlocking sections of steel or plastic materials (Fig. 7.5). Steel sheet
piles are used for a variety of excavation shoring applications; the same type of steel sheet piles are
used for vertical cutoff walls. Plastic sheet piles are a relatively recent development and are used
on a limited basis for vertical cutoff walls. Sheet piles measure approximately 0.5 m (18 in.) in
width, and interlocks join individual sheets together (Fig. 7.5). Lengths are essentially unlimited,
but sheet piles are rarely longer than about 10 to 15 m (30 to 45 ft).
Interlock
Figure 7.5 - Interlocking Steel Sheet Piles.
Plastic sheet piles are different from geomembrane panels, which are discussed
later. Plastic sheet piles tend to be relatively thick-walled (wall thickness > 3 mm or 1/8 in.) and
rigid; geomembrane panels tend to have a smaller thickness (< 2.5 mm or 0.1 in.), greater width,
and lower rigidity.
Sheet pile walls are installed by driving or vibrating interlocking steel sheet piles into the
ground. Alternatively, plastic sheet piles can be used, but special installation devices may be
needed, e.g., a steel driving plate to which the plastic sheet piles are attached. To promote a seal, a
cord of material that expands when hydrated and attains a very low permeability may be inserted in
the interlock. Other schemes have been devised and will continue to be developed for attaining a
water-tight seal in the interlock.
Sheet pile walls have a long history of use for dewatering applications, particularly where
the sheet pile wall is also used as a structural wall. Sheet pile walls also have been used on several
occasions to cutoff horizontal seepage through permeable strata that underlie dams (Sherard et al.,
1963).
Sheet pile walls have historically suffered from problems with leakage through interlocks,
although much of the older experience may not be applicable to modern sheet piles with expanding
material located in the interlock (the expandable material is a relatively recent development).
237
-------
Leakage through sheet pile interlocks depends primarily on the average width of openings in the
interlocking connections, the percentage of the interlocks that leak, and the quality and integrity of
any sealant placed in the interlock. The sheet piles may be damaged during installation, which can
create ruptures in the sheet pile material or separation of sheet piles at interlocks. Because of these
problems, sheet pile cutoffs have not been used for waste containment facilities as extensively as
some other types of vertical cutoff walls. Sheet pile walls are not discussed further in this report
7.2.2 Geomembrane Walls
Geomembrane walls represent a relatively new type of vertical barrier that is rapidly gaining
m popularity. The geomembrane wall consists of a series of geomembrane panels joined with
special interlocks (examples of interlocks are sketched in Fig. 7.6) or installed as a single unit If
the geomembrane panels contain interlocks, a water-expanding cord is used to seal the interlock
Figure 7.6 - Examples of Interlocks for Geomembrane Walls (Modified from Manassero and
Pasquahm, 1992)
• u technology has its roots in Europe, where slurry trench cutoff walls that are backfilled
with cement-bentonite have been commonly used for several decades. One of the problems with
cement-bentonite backfill, as discussed later, is that it is difficult to make the hydraulic conductivity
of the cement-bentonite backfill less than or equal to 1 x 10-7 crrj/s, which is often required of
regulatory agencies in the U.S. To overcome this limitation in hydraulic conductivity and to
improve the overall containment provided by the vertical cutoff wall, a geomembrane mav be
inserted into the cement-bentonite backfill. The geomembrane may actually be installed either in a
slurry-filled trench or it may be installed directly into the ground using a special insertion plate
238
-------
7.2.3 Walls Constructed with Slurry Techniques
Walls constructed by slurry techniques (sometimes called "slurry trench cutoff walls") are
described by Xanthakos (1979), D'Appolonia (1980), EPA (1984), Ryan (1987), and Evans
(1993). With this technique, an excavation is made to the desired depth using a backhoe or
clamshell. The trench is filled with a clay-water suspension ("mud" or "slurry"), which maintains
stability of sidewalls via hydrostatic pressure. As the trench is advanced, the slurry tends to flow
into the surrounding soil. Clay particles are filtered out, forming a thin skin of relatively
impermeable material along the wall of the trench called a "filter cake." The filter cake has a very
low hydraulic conductivity and allows the pressure from the slurry to maintain stable walls on the
trench (Fig. 7.7). However, the level of slurry must generally be higher than the surrounding
ground water table in order to maintain stability. If the water table is at or above the surface, a dike
may be constructed to raise the surface elevation along the alignment of the slurry trench cutoff
wall.
Weight of Slurry
Creates Pressure
Acting on Filter Cake
Figure 7.7 - Hydrostatic Pressure from Slurry Maintains Stable Walls of Trench.
In most cases, sodium bentonite is the clay used in the slurry. A problem with bentonite is
that it does not gel properly in highly saline water or in some heavily contaminated ground waters.
In such cases, an alternative clay mineral such as attapulgite may be used, or other special materials
may be used to maintain a viscous slurry.
The slurry trench must either be backfilled or the slurry itself must harden into a stable
material - otherwise clay will settle out of suspension, the slurry will cease to support the walls of
the trench, and the walls may eventually collapse. If the slurry is allowed to harden in place, the
slurry is usually a cement-bentonite (CB) mixture. If the slurry trench is backfilled, the backfill is
usually a soil-bentonite (SB) mixture, although plastic concrete may also be used (Evans, 1993).
239
-------
In the U.S., slurry trenches backfilled with SB have been the most commonly used vertical
cutoff trenches for waste containment applications. In Europe, the CB method of construction has
been used more commonly. The reason for the different practices in the U.S. and Europe stems at
least in part upon the fact that abundant supplies of high-quality sodium bentonite are readily
available in the U.S. but not in Europe. Also, in most situations, SB backfill will have a
somewhat lower hydraulic conductivity than cured CB slurry, and in the U.S. regulations have
tended to drive the requirements for hydraulic conductivity to lower values than in Europe.
The construction sequence for a soil-bentonite backfilled trench is shown schematically in
Fig. 7.8. *
Backfill
Mixing Area
Trench Spoils
Area of Active
Excavation
V}^ Em placed
Backfill
Figure 7.8 - Diagram of Construction Process for Soil-Bentonite-Backfilled Slurry Trench
Cutoff Wall.
The main reasons why slurry trench cutoff walls are so commonly used for vertical cutoff
walls are:
1. The depth of the trench may be checked to confirm penetration to the desired depth,
and excavated materials may be examined to confirm penetration into a particular
stratum;
2. The backfill can be checked prior to placement to make sure that its properties are as
desired and specified;
240
-------
, 3. The wall is relatively thick (compared to a sheet pile wall or a geomembrane wall);
4. There are no joints between panels or construction segments with the most common
type of slurry trench cutoff wall construction.',.
In general, in comparison to sheet-pile walls, deep-soil-mixed walls, and grouted walls,
there is more opportunity with a slurry trench cutoff wall to check the condition of the wall and
confirm that the wall has been constructed as designed. In contrast, it is much more difficult to
confirm that a sheet pile wall has been installed without damage, that grout has fully penetrated all
of the desired pore spaces in the soil, or that deep mixing as taken place as desired.
7.3 Construction of Slurry Trench Cutoff Walls
The major construction activities involved in building a slurry cutoff wall are
preconstruction planning and mobilization, preparation of the site, slurry mixing and hydration,
excavation of soil, backfill preparation, placement of backfill, clean-up of the site, and
demobilization. These activities are described briefly in the paragraphs that follow.
7.3.1 Mobilization
The first major construction activity is to make an assessment of the site and to mobilize for
construction. The contractor locates the slurry trench cutoff wall in the field with appropriate
surveys. The contractor determines the equipment that will be needed, amounts of materials, and
facilities that may be required. Plans are made for mobilizing personnel and moving equipment to
the site.
A preconstruction meeting between the designer, contractor, and CQA engineer is
recommended. In this meeting, materials, construction procedures, procedures for MQA of the
bentonite and CQA of all aspects of the project, and corrective actions are discussed (see Chapter
D- , •.-..•'."•-"''..'.
7.3.2 Site Preparation
Construction begins with preparation of the site. Obstacles are removed, necessary
relocations of utilities are made, and the surface is prepared. One of the requirements of slurry
trench construction is that the level of slurry in the trench be greater than the level of ground water.
If the ground water table is high, it may be necessary to construct a dike to ensure that the level of
slurry in the trench is above the ground water level (Fig. 7.9). There may be grade restrictions in
the construction specifications which will require some regrading of the surface or construction of
dikes in low-lying areas. The site preparation work will typically also include preparation of
working surfaces for mixing materials. Special techniques may be required for exacavation around
utility lines. ,
7.3.3 Slurry Preparation and Properties
Before excavation begins, as well as during excavation, the slurry must be prepared. The
slurry usually consists of a mixture of bentonitic clay with water, but sometimes other clays such
as attapulgite are used. If the clay is bentonite, the specifications should stipulate the criteria to be
met, e.g., filtrate loss, and the testing technique by which the parameter is to be determined. The
criteria can vary considerably from project to project.
241
-------
High Water
Table
Dike
Figure 7.9 - Construction of Dike to Raise Ground Surface for Construction of Slurry Trench.
The clay may be mixed with water in either a batch or flash mixing operation. In the batch
system specified quantities of water and bentonite are added in a tank and mixed at high speeds
with a pump, paddle mixer, or other device that provides adequate high-speed colloidal shear
mixing. Water and clay are mixed until hydration is complete and the desired properties of the
slurry have been achieved. Complete mixing is usually achieved in a few minutes. The size of
batch mixers varies, but typically a batch mixer will produce several cubic meters of mixed slurry
at a time. J
Flash mixing is achieved with a venturi mixer. With this system, bentonite is fed at a
predetermined rate into a metered water stream that is forced through a nozzle at a constant rate.
The slurry is subjected to high shear mixing for only a fraction of a second. The problem with this
technique is that complete hydration does not take place in the short period of mixing. After the
clay is mixed with water, the resulting slurry is tested to make sure the density and viscosity are
Within the requirements set forth in the CQA plan.
The mixed slurry may be pumped directly to the trench or to a holding pond or tank. If the
slurry is stored in a tank or pond, CQA personnel should check the properties of the slurry
periodically to make sure that the properties have not changed due to thixotropic processes or
sedimentation of material from the slurry. The specifications for the project should stipulate
mixing or circulation requirements for slurry that is stored after mixing.
_ The properties of the slurry used to maintain the stability of the trench are important. The
foUowmg pertains to a bentonite slurry that will ultimately be displaced by soil-bentonite or other
backfill; requirements for cement-bentonite slurry are discussed later in section 7.3.6. The slurry
must be sufficiently dense and viscous to maintain stability of the trench. However, the slurry
must not be too dense or viscous: otherwise, it will be difficult to displace the slurry when backfill
is placed. Construction specifications normally set limits on the properties of the slurry. Typically
about 4-8% bentonite by weight is added to fresh water to form a slurry that has a specific gravity
of about 1.05 to 1.15. During excavation of the trench additional fines may become suspended in
242
-------
the slurry, and the specific gravity is likely to be greater than the value of the freshly mixed slurry.
The specific gravity of the slurry during excavation is typically on the order of 1.10 -1.25.
The density of the slurry is measured with the procedures outlined in ASTM D-4380. A
known volume of slurry is poured into a special "mud balance," which contains a cup on one end
of a balance. The weight is determined and density calculated from the known volume of the cup.
The viscosity of the slurry is usually measured with a Marsh funnel. To determine the
Marsh viscosity, fluid is poured into the funnel to a prescribed level. The number of seconds
required to discharge 946 mL (1 quart) of slurry into a cup is measured. Water has a Marsh
viscosity of about 26 seconds at 23°C. Freshly hydrated bentonite slurry should have a Marsh
viscosity in the range of about 40 - 50 seconds. During excavation, the viscosity typically
increases to as high as about 65 Marsh seconds. If the viscosity becomes too large the thick slurry
must be replaced, treated (e.g., to remove sand), or diluted with additional fresh slurry.
The sand content of a slurry may also be specified. Although sand is not added to fresh
slurry, the slurry may pick up sand in the trench during the construction process. The sand content
by volume is measured with ASTM D-4381. A special glass measuring tube is used for the test.
The slurry is poured onto a No. 200 sieve (0.075 mm openings), which is repeatedly washed until
the water running through the sieve is clear. The sand is washed into the special glass measuring
tube, and the sand content (volumetric) is read directly from graduation marks.
Other criteria may be established for the slurry. However, filtrate loss and density, coupled
with viscosity, are the primary control variables. The specifications should set limits on these
parameters as well as specify the test method. Standards of the American Petroleum Institute
(1990) are often cited for slurry test methods. Limits may also be set on pH, gel strength, and
other parameters, depending on the specific application.
The primarily responsibility for monitoring the properties of the slurry rests with the
construction quality control (CQC) team. The properties of the slurry directly affect construction
operations but may also impact the final quality of the slurry trench cutoff wall. For example, if
the slurry is too dense or viscous, the slurry may not be properly displaced by backfill. On the
other hand, if the slurry is too thin and lacks adequate bentonite, the soil-bentonite backfill (formed
by mixing soil with the bentonite slurry) may also lack adequate bentonite. The CQA inspectors
may periodically perform tests on the slurry, but these tests are usually conducted primarily to
verify test results from the CQC team. CQA personnel should be especially watchful to make sure
that: (1) the slurry has a sufficiently high viscosity and density (if not, the trench walls may
collapse); (2) the level of the slurry is maintained near the top of the trench and above the water
table (usually the level must be at least 1 m above the ground water table to maintain a stable
trench); and (3) the slurry does not become too viscous or dense (otherwise backfill will not
properly displace the slurry).
7.3.4 Excavation of Slurry Trench
The slurry trench is excavated with a backhoe (Fig. 7.10) or a clam shell (Fig. 7.11).
Long-stick backhoes can dig to depths of approximately 20 to 25 m (60 to 80 ft). For slurry
trenches that can be excavated with a backhoe, the backhoe is almost always the most economical
means of excavation. For trenches that are too deep to be excavated with a backhoe, a clam shell is
normally used. The trench may be excavated first with a backhoe to the maximum depth of
excavation that is achievable with the backhoe and to further depths with a clam shell. Special
chopping, chiseling, or other equipment may be used as necessary. The width of the excavation
tool is usually equal to the width of the trench and is typically 0.6 to 1.2 m (2 to 4 ft).
243
-------
Figure 7.10 - Backhoe for Excavating Slurry Trench.
In most instances, the slurry trench cutoff wall is keyed into a stratum of relatively low
hydraulic conductivity. In some instances, the vertical cutoff wall may be relatively shallow For
example, if a floating non-aqueous phase liquid such as gasoline is to be contained, the slurry
drench cutoff wall may need to extend only a short distance below the water table surface
depending upon the site-specific circumstances. CQC/CQA personnel monitor the depth of
excavation of the slurry trench and should log excavated materials to verify the types of materials
present and to ensure specified penetration into a low-permeability layer. Monitoring normally
involves examining soils that are excavated and direct measurement of the depth of trench by
lowering a weight on a measuring tape down through the slurry. Additional equipment such as air
Hits may be needed to remove sandy materials from the bottom of the trench prior to backfill.
7.3.5 Soil-Bentonite (SB) Backfill
Soil is mixed with the bentonite-water slurry to form soil-bentonite (SB) backfill If the
soil is too coarse additional fines can be added. Dry, powdered bentonite may also be added
although it is difficult to ensure that the dry bentonite is uniformly distributed. In special
applications in which the properties of the bentonite are degraded by the ground water, other types
of clay may be used, e.g., attapulgite, to form a mineral-soil backfill. If possible, soil excavated
from the trench is used for the soil component of SB backfill. However, if excavated soil is
excessively contaminated or does not have the proper gradation, excavated soil may be hauled off
lor treatment and disposal.
244
-------
Figure 7.11. Clamshell for Excavating Slurry Trench.
Two parameters concerning the backfill are very important: (1) the presence of extremely
coarse material (i.e., coarse gravel and cobbles), and (2) the presence of fine material. Coarse
gravel is defined as material with particle sizes between 19 and 75 mm (ASTM D-2487). Cobbles
are materials with particle sizes greater than 75 mm. Fine material is material passing the No. 200
sieve, which has openings of 0.075 mm. Cobbles will tend to settle and segregate in the backfill;
coarse gravel may also segregate, but the degree of segregation depends on site-specific
conditions. In some cases, the backfill may have to be screened to remove pieces that exceed the
maximum size allowed in the specifications. The hydraulic conductivity of the backfill is affected
by the percentage of fines present (D'Appolonia, 1980; Ryan, 1987; and Evans, 1993). Often, a
minimum percentage of fines is specified. Ideally, the backfill material should contain at least 10 to
30% fines to achieve low hydraulic conductivity (< 10'7 cm/s).
245
-------
The bentonite may be added in two ways: (1) soil is mixed with the bentonite slurry
(usually with a dozer, as shown in Fig. 7.12) to form a viscous SB material; and (2) additional dry
powdered bentonite may be added to the soil-bentonite slurry mixture. Dry, powdered bentonite
may or may not be needed. D'Appolonia (1980) and Ryan (1987) discuss many of the details of
SB backfill design.
Figure 7.12 - Mixing Backfill with Bentonite Slurry.
When SB backfill is used, a more-or-less continuous process of excavation, preparation of
backfill, and backfilling is used. To initiate the process, backfill is placed by lowering it to the
bottom of the trench, e.g., with a clamshell bucket, or placing it below the slurry surface with a
tremie pipe (similar to a very long funnel) until the backfill rises above the surface of the slurry
trench at the starting point of the trench. Additional SB backfill is then typically pushed into the
trench with a dozer (Fig. 7.13). The viscous backfill sloughs downward and displaces the slurry
in the trench. As an alternative method to initiate backfilling, a separate trench that is not part of the
final slurry trench cutoff wall, called a lead-in trench, may be excavated outside at a point outside
of the limits of the final slurry trench and backfilled with the process just described, to achieve full
backfill at the point of initiation of the desired slurry trench.
246
-------
Figure 7.13 - Pushing Soil-Bentonite Backfill Into Slurry Trench with Dozer.
After the trench has been backfilled, low hydraulic conductivity is achieved via two
mechanisms: (1) the SB backfill itself has low hydraulic conductivity (typical design value is < 10-
7 cm/s), and (2) the filter cake enhances the overall function of the wall as a barrier. Designers do
not normally count on the filter cake as a component of the barrier, it is viewed as a possible source
of added impermeability that enhances the reliability of the wall. ;
The compatibility of the backfill material with the ground water at a site should be assessed
prior to construction. However, CQA personnel should be watchful for ground water conditions
that may differ from those assumed in the compatibility testing program. CQA personnel should
familiarize themselves with the compatibility testing program. Substances that are particularly
aggressive to clay backfills include non-water-soluble organic chemicals, high and low pH liquids,
and highly saline water. If there is any question about ground water conditions in relationship to
the conditions covered in the compatibility testing program, the CQA engineer and/or design
engineer should be consulted.
Improper backfilling of slurry trench cutoff walls can produce defects (Fig. 7.14). More
details are given by Evans (1993). CQA personnel should watch out for accumulation of sandy
materials during pauses in construction, e.g., during shutdowns or overnight; an airlift can be used
to remove or resuspend the sand, if necessary.
247
-------
?:< Soil-Bentonite
' ^Backfill
'
Collapse of Trench c; \' ,,>>/
• 4f* fv&&,f*ttA.
-------
and the slurry is left in place to harden. A much-less-common technique is to construct the slurry
trench with»,a bentonite-water slurry in discrete diaphragm cells (Fig. 7.15), and to displace the
bentonite-water slurry with CB in each cell.
The CB mixture cures with time and hardens to the consistency of a medium to stiff clay
(CB backfill is not nearly as strong as structural concrete). A typical CB slurry consists on a
weight basis of 75 to 80% water, 15 to 20% cement, 5% bentonite, and a small amount of
viscosity reducing material. . Unfortunately, CB backfill is usually more permeable than SB
backfill. Hydraulic conductivity of CB backfill is often in the range of 10'6 to 10"5 cm/s, which is
about an order of magnitude or more greater than typical SB cutoff walls.
(A) Excavate Panels
Excavated Panels
Panel Being
Excavated
(B) Excavate Between Panels
Excavation Between
Previously-Excavated
Panels
Figure 7.15 - Diaphragm-Wall Construction.
249
-------
The CB cutoff wall is constructed using procedures almost identical to those employed in
building structural diaphragm walls. In Europe, CB backfilled slurry trench cutoff walls are much
more common than in the U.S., at least partly because the diaphragm-wall construction capability
is more broadly available in Europe and because high-grade sodium bentonite (which is critical for
soil-bentonite backfilled walls) is not readily available in Europe. In Europe, the CB often contains
other ingredients besides cement, bentonite, and water, e.g., slag and fly ash.
7.3.7 Geomembrane in Slurry Trench Cutoff Walls
Geomembranes may be used to form a vertical cutoff wall. The geomembrane may be
installed in one of at least two ways:
1. The geomembrane may be inserted in a trench filled with CB slurry to provide a
composite CB-geomembrane barrier (Manassero and Pasqualini, 1992). The
geomembrane is typically mounted to a frame, and the frame is lowered into the
slurry. The base of the geomembrane contains a weight such that when the
geomembrane is released from the frame, the frame can be removed without the
geomembrane floating to the top. CQA personnel should be particularly watchful to
ensure that the geomembrane is properly weighted and does not float out of
position. Interlocks between geomembrane panels (Fig. 7.6) provide a seal
between panels. The panels are typically relatively wide (of the order of 3 to 7 m)
to minimize the number of interlocks and to speed installation. The width of a panel
may be controlled by the width of excavated sections of CB-filled panels (Fig.
7.15).
2. The geomembrane may be driven directly into the CB backfill or into the native
ground. Panels of geomembrane with widths of the order of 0.5 to 1 m (18 to 36
in.) are attached to a guide or insertion plate, which is driven or vibrated into the
subsurface. If the panels are driven into a CB backfill material, the panels should
be driven before the backfill sets up. Interlocks between geomembrane panels (Fig.
7.6) provide a seal between panels. This methodology is essentially the same as
that of a sheet pile wall.
Although use of geomembranes in slurry trench cutoff walls is relatively new, the
technology is gaining popularity. The promise of a practically impermeable vertical barrier, plus
excellent chemical resistance of HOPE geomembranes, are compelling advantages. Development
of more efficient construction procedures will make this type of cutoff wall increasingly attractive.
7.3.8 Other Backfills
Structural concrete could be used as a backfill, but if concrete is used, the material normally
contains bentonite and is termed plastic concrete (Evans, 1993). Plastic concrete is a mixture of
cement, bentonite, water, and aggregate. Plastic concrete is different from structural concrete
because it contains bentonite and is different from SB backfill because plastic concrete contains
aggregate. Other ingredients, e.g., fly ash, may be incorporated into the plastic concrete.
Construction is typically with the panel method (Fig. 7.15). Hydraulic conductivity of the backfill
can be < 10-8 cm/s. High cost of plastic concrete limits its use.
A relatively new type of backfill is termed soil-cement-bentonite (SCB). The SCB wall
uses native soils (not aggregates, as with plastic concrete). Placement is in a continuous trench
rather than panel method.
250
-------
7.3.9 Caps
A cutoff wall cap represent? the final surface cap on top of the slurry trench cutoff wall.
The cap may be designed to minimize infiltration, withstand traffic loadings, or serve other
purposes. CQA personnel should also inspect the cap as well as the wall itself to ensure that the
cap conforms with specification.
7.4 Other Types of Cutoff Walls
Evans (1993) discusses other types of cutoff walls. These include vibrating beam cutoff
walls, deep soil mixed walls, and other types of cutoff walls. These are not discussed in detail
here because these types of walls have been used much less frequently than the other types.
7.5 Specific COA Requirements
No standard types of tests or frequencies of testing have evolved in the industry for
construction of vertical cutoff walls. Among the reasons for this is the fact that construction
materials and technology are continually improving. Recommendations from this section were
taken largely from recommendations provided by Evans (personal communication).
For slurry trench cutoff walls, the following comments are applicable. The raw bentonite
(or other clay) that is used to make the slurry may have specific requirements that must be met. If
so, tests should be performed to verify those properties. There are no standard tests or frequency
of tests for the bentonite. The reader may wish to consult Section 2.6.5 for a general discussion of
tests and testing frequencies for bentonite-soil liners. For the slurry itself, common tests include
viscosity, unit weight, and filtrate loss, and other tests often include pH and sand content. The
properties of the slurry are normally measured on a regular basis by the contractor's CQC
personnel; CQA personnel may perform occasional independent checks.
The soil that is excavated from the.trench should be continuously logged by CQA personnel
to verify that subsurface conditions are similar to those that were anticipated. The CQA personnel
should look for evidence of instability in the walls of the trench (e.g., sloughing at the surface next
to the trench or development of tension cracks). If the trench is to extend into a particular stratum
(e.g., an aquitard), CQA personnel should verify that adequate penetration has occurred. The
recommended procedure is to measure the depth of the trench once the excavator has encountered
the aquitard and to measure the depth again, after adequate penetration is thought to have been
made into the aquitard.
After the slurry has been prepared, and CQC tests indicate that the properties are adequate,
additional samples are often taken of the slurry from the trench. The samples are often taken from
near the base of the trench using a special sampler that is capable of trapping slurry from the
bottom of the trench. The unit weight is particularly important because sediment may collect near
the bottom of the trench. For SB backfill, the slurry must not be heavier than the backfill. The
depth of the trench should also be confirmed by CQA personnel just prior to backfilling. Often,
sediments can accumulate near the base of the trench - the best time to check for accumulation is
just prior to backfilling. CQA personnel should be particularly careful to check for sedimentation
after periods when the slurry has not been agitated, e.g., after an overnight work stoppage.
Testing of SB backfill usually includes unit weight, slump, gradation, and hydraulic
conductivity. Bentonite content may also be measured, e.g., using the methylene blue test (Alther,
1983). Slump testing is the same as for concrete (ASTM C-143). Hydraulic conductivity testing
is often performed using the API (1990) fixed-ring device for the filter press test. Occasional
251
-------
comparative tests with ASTM D-5084 should be conducted. There is no widely-applied frequency
of testing backfill materials.
7.6 Post Construction Tests for Continuity
At the present time, no testing procedures are available to determine the continuity of a
completed vertical cutoff wall.
7.7 References
Alther, G. R. (1983), "The Methylene Blue Test for Bentonite Liner Quality Control,"
Geotechnical Testing Journal, Vol. 6, No. 3, pp. 133-143.
American Petroleum Institute (1990), Recommended Practice for Standard Procedure for Field
Testing Drilling Fluids, API Recommended Practice 13-B-l, Dallas, Texas.
ASTM C-143, "Slump of Hydraulic Cement Concrete."
ASTM D-2487, "Classification of Soils for Engineering Purposes (Unified Soil Classification
System)."
ASTM D-4380, "Density of Bentonitic Slurries." .
ASTM D-4381, "Sand Content by Volume of Bentonite Slurries."
ASTM D-5084, "Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a
Flexible Wall Permeameter."
D'Appolonia, D. J. (1980), "Soil-Bentonite Slurry Trench Cutoffs," Journal of Geotechnical
Engineering, Vol. 106, No. 4, pp. 399-417.
Evans, J. C. (1993), "Vertical Cutoff Walls," in Geotechnical Practice for Waste Disposal, D. E.
Daniel (Ed.), Chapman and Hall, London, pp. 430-454.
Manassero, M., and E. Pasqualini (1992), "Ground Pollutant Containment Barriers," in
Environmental Geotechnology, M.A. Usmen and Y.B. Acar (Eds.), A.A. Balkema,
Rotterdam, pp. 195-204.
Ryan, C. R. (1987), "Soil-Bentonite Cutoff Walls," in Geotechnical Practice for Waste Disposal
'87, R. D. Woods (Ed.), American Society of Civil Engineers, New York, pp. 182-204.
Sherard, J. L., Woodward, R. J., Gizienski, S. F., and W. A. Clevenger (1963), Earth and
Earth-Rock Dams, John Wiley and Sons, Inc., New York, 725 p.
U.S. Environmental Protection Agency (1984), "Slurry Trench Construction for Pollution
Migration Control," Office of Emergency and Remedial Response, Washington, DC, EPA-
540/2-84-001.
Xanthakos, P. P. (1979), Slurry Walls, McGraw-Hill Book Company, New York, 822 p.
252
-------
Chapter 8
Ancillary Materials, Appurtenances and Other Details
This chapter is devoted toward ancillary materials used within a waste containment facility,
various appurtenances which are necessary for proper functioning of the system and other
important details. Ancillary materials such as plastic pipe for leachate transmission, sumps for
collection of leachate, manholes and pipe risers for removal of leachate will be covered in this
chapter. Appurtenances, such as penetrations made through various barrier materials, will be
covered. Lastly, other important details requiring careful inspection, such as anchor trenches,
internal dikes and berms, and access ramps, will also be addressed.
8.1 Plastic Pipe (aka "Geopipe1")
Whenever the primary or secondary leachate collection system at the bottom of a waste
containment facility is a natural soil material, such as sand or gravel, a perforated piping system
should be located within it to rapidly transmit the leachate to a sump and removal system. Figure
8.1 illustrates the cross section of such a pipe system which is generally located directly on top of
the geomembrane or geotextile to 225 mm (9.0 in.) above the primary liner material. This is a
design issue and the plans and specifications must be clear and detailed regarding these
dimensions.
^•^•^•^•^•^•^•^•^•^•^•^^^•^•^•J1*!?1" Psrf. [T^Vj«^Vj"»^B^«^VjVj"jj'j^«^«^B^V^Vj"Vj'>jiV^
J*J*J>mSmJ
S??S?fS
Geotextile
Filters
Drainage
Stone
Geotextile
Protection
Layer
Geomembrane
Figure 8.1 - Cross Section of a Possible Removal Pipe Scheme in a Primary Leachate Collection
and Removal System (for illustration purposes only).
The pipes are sometimes placed in a manifold configuration with feeder lines framing into a
larger main trunk line thus covering the entire footprint of the landfill unit or cell, see Fig. 8.2.
The entire pipe network flows gravitationally to a low point where the sump and removal system
253
-------
Access for
Cleanout
Vertical
Removal
Sump and
Manhole or
Sideslope
Riser
Figure 8.2 - Plan View of a Possible Removal Pipe Scheme in a Primary Leachate Collection and
Removal System (for illustration purposes only).
consisting of either a manhole or pipe riser is located. The diagonal feeder pipes, if included, are
always perforated to allow the leachate to enter into them. The central trunk lines may or may not
be perforated depending on the site specific design. It must be recognized, however, that there is a
large variety of schemes that are possible and it is clearly a design issue which must be
unequivocally presented in the plans and specifications.
Leachate collection and transmission lines in most waste containment facilities are plastic
pipe, with polyvinyl chloride (PVC) and high density polyethylene (HOPE) being the two major
material types in current use. Furthermore, there are two types of HDPE pipe in current use, solid
wall and corrugated types. Each of these types of plastic pipes will be described.
8.1.1 Polwinvl Chloride fPVO Pipe.
Polyvinyl chloride (PVC) pipe has been used in waste containment systems for leachate
collection and removal in a number of different locations and configurations. The pipes can be
perforated or not depending on the site specific design. The pipes are often supplied in 6.1 m (20
ft) lengths which are joined by couplings or utilize bell and spigot ends. The PVC material
typically consists of resin, fillers, carbon black/pigment and additives. PVC pipe does not contain
any liquid plasticizers, see Fig. 8.3.
Regarding a specification or a MQA document for PVC pipe and fittings the following items
should be considered.
254
-------
Figure 8.3 - Photograph of PVC Pipe to be Used in a Landfill Leachate Collection System.
1. The basic resin should be made from PVC as defined in ASTM D-1755. Details are
contained therein.
2. Other materials in the formulation, such as fillers, carbon black/pigment and additives
should be stipulated and certified as to the extent of their prior use in plastic pipe.
3. Clean rework material, generated from the manufacturer's own pipe or fitting production
may be used by the same manufacturer providing that the rework material meets the
above requirements. See section 3.2.2 for a description of possible use of reworked
and/or recycled material.
4. Pipe tolerances and properties must meet the applicable standards for the particular grade
required by the plans and specifications. For PVC pipe specified as Schedule 40, 80
and 120, the appropriate specification is ASTM D-1785. For PVC pipe in the standard
dimension ratio (SDR) series, the applicable specification is ASTM D-2241.
255
-------
5. Both of the above referenced ASTM Standards have sections on product marking and
identification which should be followed as well as requiring the manufacturer to provide
a certification statement stating that the applicable standard has been followed.
6. PVC pipe fittings should be in accordance with ASTM D-3034. This standard includes
comments on solvent cement and elastomeric gasket joints as well as a section on
product marking and certification.
8.1.2 High Density Polyethylene (HDPE^ Smooth Wall Pipe
High density polyethylene (HOPE) smooth wall pipe has been used in waste containment
systems for leachate collection and removal in a number of different locations and configurations.
The pipe can be perforated or not depending on the site specific design. The pipes are often
supplied in 6.1 m (20 ft) lengths which are generally joined together using butt-end fusion using a
hot plate as per the gas pipe construction industry. Other joining variations such as bell and spigot,
male-to-female and threading are also available. The HDPE material itself consists of 97-98%
resin, approximately 2% carbon black and up to 1% additives. Figure 8.4 illustrates the use of
HDPE smooth pipe.
Figure 8.4 - Photograph of HDPE Smooth Wall Pipe Risers Used as Primary and Secondary
Removal Systems from Sump Area to Pump and Monitoring Station.
256
-------
The following items should be considered regarding the contract specification or MQA
document on HDPE solid wall pipe and fittings:
1. The basic material should be made of HDPE resin and should conform to the
requirements of ASTM D-1248. Details are contained therein.
2. Quality control tests on the resin are typically density and melt flow index. The
appropriate designations are ASTM D-1505 or D-792 and D-1238, respectively. Other
in-house quality control tests should be encouraged and followed by the manufacturer.
3. Typical densities for HDPE pipe resins are 0.950 to 0.960 g/cc. This is a Type HI
HDPE resin according to ASTM D-1248 and is higher than the density of the resin used
in HDPE geomembranes and geonets.
4. Carbon black can be added as a concentrate, as it customarily is, or as a powder. The
type and amount of carbon black, as well as the type of carrier resin if concentrated
pellets are used, should be stated and certified by the manufacturer.
5. The amount of additives used should be stated by the manufacturer. If certification is
required it would typically not state the type of additive, since they are usually
proprietary, but should state that the additive package has successfully been used in the
past and to what extent.
8.1.3 High Density Polyethylene (HOPEI Corrugated Pipe
Corrugated high density polyethylene (HDPE), also called "profiled" pipe, has been used in
waste containment systems for leachate collection and removal in a number of different locations
and configurations. The pipe can be perforated or slotted depending on the site specific design.
The inside can be smooth lined or not depending on the site specific design. The pipes are often
supplied in 6.1 m (20 ft) lengths which are joined together by couplings made by the same
manufacturer as the pipe itself. This is important since the couplings are generally not
interchangeable among different pipe manufacturer's products. The HDPE material itself consists
of 97-98% resin, approximately 2% carbon black and up to 1% additives. Figure 8.5 illustrates
HDPE corrugated pipe.
Regarding the contract specification or MQA document on HDPE corrugated pipe and
fittings, the following items should be considered:
1. The basic material should be made of HDPE resin and should conform to the
requirements of ASTM D-1248. Details are contained therein.
2. Quality control tests are typically density and melt flow index. Their designations are
ASTM D-1505 or D-792 and D-1238, respectively. Other in-house quality control tests
are to be encouraged and followed by the manufacturer.
3. Typical densities for HDPE pipe resins are 0.950 to 0.960 g/cc. This is a Type III
HDPE resin according to ASTM D-1248 and is higher than the resin density used in
HDPE geomembranes.
4. Carbon black can be added as a concentrate as it customarily is, or as a powder. The
type and amount of carbon black, as well as the type of carrier resin if concentrated
pellets are used, should be stated and certified by the manufacturer.
257
-------
5. The amount of additives used should be stated by the manufacturer. If certification is
required it would typically not state the type of additive, since they are usually
proprietary, but should state that the additive package has successfully been used in the
past.
TfoS^o ^ documents for HOPE corrugated pipe should be noted. There is an
AAt>mu Specification available for corrugated polyethylene pipe in the 300 to 900 mm
(12 to 36 in.) diameter range under the designation M294-90 and another for 75 to 250
mm (3 to 10 in.) diameter pipe under the designation of M252-90.
Figure 8.5 - Photograph of HDPE Corrugated Pipe Being Coupled and After Installed.
8.1.4 Handling of Plastic Pipe
As with all other geosynthetic materials a number of activities occur between the
manufacturing of the pipe and its final positioning in the waste facility. These activities include
packaging, storage at the manufacturers facility, shipment, storage at the field site, conformance
testing and the actual placement
258
-------
8.1.4.1 Packaging
Both PVC pipe and HDPE pipe are manufactured in long lengths of approximately 6.1 m
(20 ft) with varying wall thicknesses and configurations. They are placed on wooden pallets and
bundled together with plastic straps for bulk handling and shipment. The packaging is such that
either fork lifts or cranes using slings can be used for handling and movement. As the diameter
and wall thickness increases, however, this may not be the case and above 610 mm (24 in.)
diameter the pipes are generally handled individually.
8.1.4.2 Storage at Manufacturing Facility
Bundles of plastic pipe can be stored at the manufacturing facility for relatively long periods
of time with respect to other geosynthetics. However, if stored outdoors for over 12 months
duration, a temporary enclosure should be used to cover the pipe from ultraviolet exposure and
high temperatures. Indoors, there is no defined storage time limitation. Pipe fittings are usually
stored in a container or plastic net.
8.1.4.3 Shipment
Bundled pallets of plastic pipe are shipped from the manufacturer's or their representative's
storage facility to the job site via common carrier. Ships, railroads and trucks have all been used
depending upon the locations of the origin and final destination. The usual carrier from within the
USA, is truck. When using flatbed trucks, the pallated pipe is usually loaded by means of a fork
lift or a crane with slings wrapped around the entire unit. When the truck bed is closed, i.e., an
enclosed trailer, the units are usually loaded by fork lift. Large size pipes above 610 mm (24 in.)
in diameter are handled individually.
8.1.4.4 Storage at Field Site
Offloading of palleted plastic pipe at the site and temporary storage is a necessary follow-up
task which must be done in an acceptable manner.
Items to be considered for the contract specification or CQA document are the following:
1. Handling of pallets of plastic pipe should be done in a competent manner such that
damage does not occur to the pipe.
2. The location of field storage should not be in areas where water can accumulate. The
pallets should be on level ground and oriented so as not to form a dam creating the
ponding of water.
3. The pallets should not be stacked more than three high. Furthermore, they should be
stacked in such a way that access for conformance testing is possible.
4. Outdoor storage of plastic pipe should not be longer than 12 months. For storage
periods longer than 12 months a temporary covering should be placed over the pipes,
or they should be moved to within an enclosed facility.
8.1.5 Conformance Testing and Acceptance
Upon delivery of the plastic pipe to the project site, and temporary storage thereof, the CQA
engineer should see that conformance test samples are obtained. These samples are then sent to the
259
-------
CQA laboratory for testing to ensure that the pipe supplied conforms to the project plans and
specifications.
Items to consider for the contract specification or CQA document in this regard are the
following:
1. The pipe should be identified according to its proper ASTM standard:
(a) for PVC Schedule 40,80 and 120: see ASTM D-1785
(b) for PVC SDR Series: see ASTM D-2241
(c) for PVC pipe fittings: see ASTM D-3034
(d) for HOPE SDR Series: see ASTM D-1248 and ASTM F-714
(e) for HOPE corrugated pipe and fittings: see AASHTO M294-90 and M252-90.
2. The conformance test samples should make use of the same identification system as the
•-, appropriate ASTM standard, if one is available.
3. A lot should be defined as a group of consecutively numbered pipe sections from the
same manufacturing line. Other definitions are also possible and should be clearly
stated in the CQA documents.
4. Sampling should be done according to the contract specification and/or CQA
documents. Unless otherwise stated, sampling should be based on one sample per lot
not to exceed one sample per 300 m (1000 ft) of pipe.
5. Conformance tests at the CQA Laboratory should include the following:
(a) for PVC pipe and fitting: physical dimensions according to ASTM D-2122,
density according to ASTM D-792, plate bearing test according to ASTM D-2412,
and impact resistance according to ASTM D-2444.
(b) for HDPE solid-wall and corrugated pipe: physical dimensions according to
ASTM D-2122, density according to ASTM D-1505, plate bearing test according
to ASTM D-2412 and impact resistance according to ASTM D-2444.
(c) for HDPE corrugated pipe in the 300 to 900 mm (12 to 36 in.) range see AASHTO
M294-90 and in the 75 to 250 mm (3 to 10 in.) range see AASHTO M252-90.
6. Conformance test results should be sent to the CQA engineer prior to deployment of
any pipe from the lot under review.
7. The CQA engineer should review the results and should report any non-conformance to
the Project Manager.
8. The resolution of failing conformance tests should be clearly stipulated in the
specifications or CQA documents.
260
-------
8.1.6 Placement
Plastic pipe is usually placed in a prepared trench or within other prepared subgrade
materials. If the pipe is to be placed on or near to a geomembrane, as in the leachate collection
system shown in Fig. 8.1, the drainage sand or stone should be placed first. There may be a
requirement to lightly compact sand to 90% relative density according to ASTM D-4254. Small
excavations of slightly greater than the diameter of the pipe are then made, and the pipe is placed in
these shallow excavations. Thus a trench, albeit a shallow one, is constructed in all cases of pipe
placement in leachate collection sand or stone.
Where plastic pipe is placed at other locations adjacent to the containment facility and the soil
is cohesive, compaction is critical if high stresses are to be encountered. Compaction control is
necessary, e.g., 95% of standard Proctor compaction ASTM D-698 is recommended so as to
prevent subsidence of the pipe while in service.
The importance of the density of the material beneath, adjacent and immediately above a
plastic pipe insofar as its load-carrying capability is concerned cannot be overstated. Figure 8.6
shows the usual configuration and soil backfill terminology related to the various materials and
their locations.
Regarding a specification or CQA document for plastic pipe placement, ASTM D-2321
should be referenced. For waste containment facilities the following should be considered:
1. The soil beneath, around and above the pipe shall be Class IA, IB or II according to
ASTM D-2321.
2. The backfill soil should extend a minimum of one pipe diameter above the pipe, or 300
mm (12 in.) which ever is smaller.
3. Other conditions should be taken directly according to ASTM D-2321.
4. Pipe fittings should be in accordance with the specific pipe manufacturer's
recommendations.
8.2 Sumps. Manholes and Risers
Leachate which migrates along the bottom of landfills and waste piles flows gravitationally
to a low point in the facility or cell where it is collected in a sump. Two general variations exist;
one is a prefabricated sump, made either in-situ or off-site, with a manhole extension rising
vertically through the waste and final cover, the other is a low area formed in the liner itself with a
solid wall pipe riser coming up the side slope where it eventually penetrates the final cover.
Both variations are shown schematically in the sketches of Fig. 8.7. In addition, the sump and
sidewall riser of a secondary leachate collection system typically used in double lined facilities is
shown in the right sketch of Fig. 8.7(b), i.e., a leak detection system. Each type of system will be
briefly described.
Many existing landfills have been constructed with primary leachate collection and removal
sumps and manholes constructed to the site specific plans and specifications as shown in the left
hand sketch of Fig. 8.7(a). The vertical riser is either a concrete or plastic standpipe placed in 3 m
(10 ft) sections. It is extended as the waste is placed in the facility and eventually it must penetrate
the final cover. Leachate is removed from this manhole, on an as demanded basis, by a
submersible pump which is permanently located in the sump.
261
-------
100-150 mm
Secondary Backfill
Primary Backfill
Pipe Haunch Area
Bedding Soil
Figure 8.6 - A Possible Buried Pipe Trench Cross Section Scheme Showing Soil Backfill
Terminology and Approximate Dimensions (for illustration purposes only).
A more recent variation of the above removal system is an off-site factory fabricated sump
and manhole system wherein the leachate collection pipe network frames directly into the sump
see the right hand sketch of Fig. 8.7(a). Various standardized sump capacities are available This
type of system requires the least amount of field fabrication. The riser is extended in sections as
the waste is placed in the facility and eventually it must penetrate the final cover. Leachate is
removed from the manhole by a submersible pump which is permanently located in the sump.
Quite a different variation for primary leachate removal is a well defined low area in the
primary geomembrane into which the leachate collection pipe network flows. This low area creates
a sump which is then filled with crushed stone and from which a pipe riser extends up the side
slope. The pipe riser is usually a solid wall pipe with no perforations. When the facility is
T?? iytf o T^? S4Sld waste' ±e ri?er must Penetrate we cover as shown in the left hand
Sketch ot big. 8.7(b). The leachate is withdrawn using a submersible pump which is lowered
down the pipe riser on a sled and left in place except for maintenance and/or replacement, recall
^
262
-------
Leachate
Removal
Geomembrane
Cover
/XvX
Vs/*xx/VN
Solid
Waste
•&;&
';%
f S S
' S f
:>x
^
1
Leachate
Removal
/xxxxxxx
^^"xxxxxxx
'"••^•••>
Footing
In-Situ Fabrication
^^w^^JSE^^SEsS^—^rf5S3S2
Header Pipe Geomembrane
Factory Fabrication
(a) Types of Primary Leachate Collection Sumps and Manholes with
Vertical Standpipe Going through the Waste and Cover
Cover
Leachate
Removal
Cover
Leachate
Removal
Stone
Geomembranes
, Stone
(b) Types of Primary (Left) and Secondary (Right) Leachate Collection Sumps
and Pipe Risers Going Up the Side Slopes
Figure 8.7 - Various Possible Schemes for Leachate Removal
263
-------
In a similar manner as above, but now for secondary leachate removal, a sump can be
f°J%- l^^A0"^ hn£r s^stem which is flUed with g^61 as sh°wn ™ the right hand sketch
or fig. 8.7(b). A solid wall pipe riser, perforated in its lower section, extends up the sidewall
between the primary and secondary liner where it must penetrate both the primary liner and
eventually the coyer system liner, see the right hand sketch of Fig. 8.7(b). This pipe riser is often
a solid wall pipe in the 100-200 (4 to 8 in.) diameter range with no perforations The leachate is
withdrawn and/or monitored using a small diameter sampling pump which is lowered down the
riser and left in place except for maintenance and/or replacement, recall Fig. 8.4.
Some specification and CQA document considerations for the various sump, manhole and
riser schemes just described are as follows. Note, however, that there are other possible design
schemes that are available in addition to those mentioned above.
1. In-situ fabrication of sumps requires a considerable amount of hand labor in the field.
e^.cr^ JP and VLDPE geomembranes are extrusion fillet welded, while PVC
and CSPE-R geomembranes are usually bodied chemical seams (EPA, 1991) Careful
visual inspection is necessary.
2. The soil support beneath the sumps and around the manhole risers of plastic pipes is
critically important. The specification should reference ASTM D-2321 with only
backfill types IA, IB and II being considered.
3. Riser pipes for primary and secondary leachate removal are generally not perforated
except for the lowest section of pipe which accepts the leachate.
4. Riser pipe joints for primary and secondary leachate removal require special visual
attention since neither destructive nor nondestructive tests can usually be accommodated.
5. The sump, manholes and risers must be documented by the CQA engineer before
acceptance and placement of solid waste.
8.3 Liner System Penetrafinns
Although the intention of most designers of waste containment facilities is to avoid liner
peneti-ations, leachate removal is inevitably required at some location(s) of the barrier system.
Recall Fig. 8.7 where the cover is necessarily penetrated for primary leachate removal. For leak
detection both the primary liner and the cover liner must be penetrated. It should also be
recognized that the penetrations will include geomembranes, compacted clay liners and/or
geosynthetic clay liners. Figure 8.8 illustrates some details of pipe penetrations through all three
types of barrier materials. . rr e e
The following recommendations are made for a specification or CQA document:
1. Geomembrane pipe boots are usually factory fabricated to a size which tightly fits the
outside diameter of the penetrating pipe. Unique situations, however, will require field
laoncanon, e.g., when pipe penetration angles are unknown until final installation.
2- The skjrt of the pipe boot which flares away from the pipe penetration should have at
least 500 mm (12 in.) of geomembrane on all sides of the pipe.
3. The skirt of the pipe boot should be seamed to the base geomembrane by extrusion fillet
or bodied chemical seaming depending on the type of geomembrane (EPA, 1991).
264
-------
Cushioning Layer
Stainless Steel Clamp
Geomembrane
Field Seam
Pipe
(a) Geomembrane Penetration
Dry Bentonite
Pipe
(b) Compacted Clay Liner (CCL) Penetration
GCL
Pipe
Dry Bentonite
Dry Bentonite
(c) Geosynthetic Clay Liner (GCL) Penetration
Figure 8.8 - Pipe Penetrations through Various Types of Barrier Materials
265
-------
4. The nondestructive testing of the skirt of the pipe boot should be by vacuum box or air
lance depending on the type of geomembrane. Refer to Section 3.6.2.
5. The pipe boot should be of the same type of geomembrane as that of the liner through
wmcn the penetration is being made.
6. Pipe penetrations should be positioned with sufficient clearance to allow for proper
welding and inspection. F F
7. Stainless steel pipe clamps used to attach pipe boots to the penetrating pipes should be
of an adequate size to allow for a cushion of compressible material to be placed between
the inside surface of the clamp and that of the geomembrane portion of the pipe boot
8. Location of pipe clamps should be as directed on the plans and specifications.
9. Pipe penetrations through compacted clay liners and geosynthetic clay liners should use
an excess of hand placed dry bentonite clay as directed in the plans and specifications.
8.4 Anchor Trenches
s&sssssStoS? cover a waste faduty end in an
8.4.1 Geomembrane
*nt- , a geomembrane at the perimeter of landfill cells or at the perimeter of the
entire facility generally ends in an anchor trench. As shown in Fig. 8.9, the variations are
speStions Sh°Uld bC Specifically addressed in theconslructioTpS a^d
Some general items that should be addressed in the specification or CQA documents
regarding geomembrane termination in anchor trenches are as follows:
1 . The seams of adjacent sheets of geomembranes should be continuous into the anchor
trench to the full extent indicated in the plans and specifications.
2. Seaming of geomembranes within the anchor trench can be accomplished by temporarily
supporting the adjacent sheets to be seamed on a wooden support platform in order that
horizontal seaming can be accomplished continuously to the end of the geomembrane
sheets. The temporary support is removed after the seam is complete and the
geomembrane is then allowed to drop into the anchor trench.
3. Destructive seam samples can be taken while the seamed geomembrane is temporarily
supported in the horizontal position. y
4. Nondestructive tests can also be performed while the seamed geomembrane is
temporarily supported in the horizontal position.
5. The anchor trench is generally backfilled after the geomembrane has been documented
by the CQA engineer, but may be at a later date depending upon the site specific plans
and. specifications.
266
-------
600 - 900 mm
Typical Anchor Trench
1 - 2m
s s s s s
Horizontal Runout Anchor
300 - 400 mm
Shallow "V" Anchor Trench
Top of Slope
Bolted Anchor System
Polymer Batten Strip
200
mm
150 - 300 mm -*
Concrete Anchor Block
Figure 8.9 - Various Types of Geomembrane Anchors Trenches (Dimensions are Typical and for
Example Only).
267
-------
6. The anchor trench itself should be made with slightly rounded corners so as to avoid
sharp bends in the geomembrane. Loose soil should not be allowed to underlie the
geomembrane in the anchor trench.
7. The anchor trench should be adequately drained to prevent ponding of water or softening
of the adjacent soils while the trench is open.
8. Backfilling in the anchor trench should be accomplished with approved backfill soils
placed at their required moisture content and compacted to the required density.
9. The plans and specifications should provide detailed construction requirements for
anchor trenches regardless if soils or other backfill materials are used.
8.4.2 Other Geosvnthetics
Since all geosynthetics, not only geomembranes, need adequate termination, some
additional comments are offered for plans, specifications or CQA documents.
1. Geotextiles, either beneath or above geomembranes, usually follow their associated
geomembrane into the same type of anchor trenches as shown in Fig. 8.9.
2. Geonets may or may not terminate in the anchor trench. Water transmission from
beyond the waste containment may be a concern when requiring termination of the
geonet within the geomembrane's anchor trench or in a separate trench by itself. Thus
termination of a geonet may be short of the associated geomembrane's anchor trench.
This is obviously a design issue and must be clearly detailed in the contract plans and
specifications.
3. When used by themselves, geosynthetic clay liners (GCLs) will generally terminate in a
anchor trench in soil of the type shown in Fig. 8.9. When GCLs are with an associated
geomembrane, as in a composite liner, each component will sometimes end in a separate
anchor trench. These are design decisions.
4. Double liner systems will generally have separate anchor trenches for primary and
secondary liner systems. This is a design decision.
5. In all of the above cases, the plans and specifications should provide detailed dimensions
and construction requirements for anchor trenches of all geosynthetic components.
6. The plans and specifications should also show details of how natural soil components,
e.g., compacted clay liners and sand or gravel drainage layers, terminate with respect to
one another and with respect to the geosynthetic components.
8.5 Access Ramps
Heavily loaded vehicles must enter the landfill facility during construction activities and
during placement of the solid waste. Typical access ramps will be up to 5.5 m (18 ft.) in width
and have grades up to 12%. The general geometry of an access ramp is shown in Fig. 8.10(a).
268
-------
(a) Geometry of a Typical Ramp
Roadway
Leachate
CoEection
Geomembrane
Leak
Detection
Geomembrane
(b) Cross Section of Ramp Roadway
Figure 8.10 - Typical Access Ramp Geometry and Cross Section
269
-------
nf A ? e \ S °i? Such a ramp can ** extremely large and generally involve some degree
of dynamic force due to the constant breaking action which drivers use when descending the steep
grades. Note that the entire liner cross section must extend uninterrupted from the upplr slope to
JSS^S^^tri^Jf s° m^.naoessarily Pass beneath the roadway base course. When
P,?Sg id°Ukle kfdj^ty th« can involve numerous geosynthetic and natural soil layers.
™±?L?°?Pl!Ca £ lue desJlgn "I8"68 is that drainage from the upper side slopes must
communicate beneath the roadway base course layer or travel parallel to it and be contained
accordingly. A reinforcing element (geotextile or geogrid) can be incorporated in the roadway base
course material. This can serve several purposes; i.e., to protect long-term integrity of underlying
systems, to minimize potential sliding failures, and to minimize potential rStting and bearinf
"68' ** °ntlCal de8ign iSSU6S and must ** Wel1 defined in *he plans and
ite Re,gardinS recommendations for the contract specifications or CQA document, the following
1. Many facilities will limit the number of vehicles on the access ramp at a given time
Such stipulations should be strictly enforced.
2. Vehicle speeds on access ramps should be strictly enforced.
3 . Regular inspection should be required to observe if tension cracks open in the roadway
base coarse soils. This may indicate some degree of slippage of the soil and possible
damage to the liner system. ,
4. Ponding of upper slope runoff water against the roadway profile should be observed for
possible erosion effects and loss of base course material. If a drainage ditch or pipe
system is indicated on the plans, it should be constructed as soon as possible after
completion of the roadway subbase soils.
5' °adWay baSC °OUrSe Pr°flle Sh°Uld ** fully maintained for the active lifetime of the
Geosvntheric Reinforcement Materials
and waste pile covers with slopes greater than 3 horizontal to 1 vertical
etatfiV " r~:—v "Sues regarding downgradient sliding begin to be important. Additionally, the
stability of primary leachate collection systems for landfill and waste pile liners with slopes greater
than 3H: IV is suspect at least until the solid waste material within the unit raises to a stabilizing
level, buch issues, of course, must be considered during the design phase and the contract plans
and specifications must be very clear on the method of reinforcement, if any. If reinforcement is
necessary it can be accomplished by using geotextiles or geogrids within the layer contributing to
me instability to offset some, or even all, of the gravitational stresses. Refer to Fig. 8.11 (a) and
(b) for the general orientation of such reinforcement, which is sometimes called "veneer
Wh.n « Be f*$R Pfuswg geognd or geotextile reinforcement to support a liner or liner system
when a new landfill is built above, or adjacent to, an existing landfill has recently been developed
The technique has been referred to as "piggybacking" when vertical expansions are involved, see
wg. 8.1 l(c) The mam focus of the reinforcement is to provide stability against differential
Settlement which can nrenr in thp pvicHncT landfill J & wv-iiuai
settlement which can occur in the existing landfill.
270
-------
Reinforcement
(Geogrid or
Geotextile)
Cover Soil
Geomembrane
Separate
Anchor
Trenches
(a) Cover Soil Veneer Stability
^^* Proposed
*- Waste
Leachate Collection Soil
Reinforcement
(Geogrid or
Geotextile)
(b) Leachate Collection Soil Veneer Stability
Geomembrane
Reinforcement
(Geogrid or
Geotextile)
(c) Liner System Reinforcement for "Piggy backing"
Figure 8.11 - Geogrid or Geotextile Reinforcement of (a) Cover Soil above Waste, (b) Leachate
Collection Layer beneath Waste, and (c) Liner System Placed above Existing Waste
("Piggybacking")
271
-------
Since geotextiles were described previously from a manufacturing standpoint and for
separation and filtration applications, they will be discussed here only from their reinforcement
perspective. Geogrids will be described from both their manufacturing and reinforcement
perspectives.
8.6.1 Geotextiles for Reinforcement'
f > >r/^?e manufacturing °f geotextiles was described in section 6.2 along with recommendations
for MQC and MQA documents. Regarding CQC and CQA, the focus was on separation and
filtration applications. Some specific recommendations regarding reinforcement geotextiles for a
specification or CQA document are as follows:
1 . A manufacturer's certification should be provided that the geotextile meets the property
criteria specified for the geotextile that was approved for use on the project via the
plans and specifications.
2 . CQA personnel should check that the geotextile delivered to the job site is the proper
and intended material. This is done by verifying the identification label and its coding
and by visual identification of the product, its construction and other visual details.
3 . Conformance samples of the geotextile supplied to the job site should be obtained as
per ASTM D-4759. Typically, the outer wrap of the rolls are used for such sampling.
4 . Conformance tests should be the following. Wide width tensile strength per ASTM D-
Too?' frapezoidal tear strength per ASTM D-4533 and puncture strength per ASTM D-
4833. Additional conformance tests which may be considered are polymer
identification via thermogravimetric analysis (TGA) and grab tensile strength, via
ASTMD-4632.
5 . Field placement of geotextiles should be at the locations indicated on the contract plans
and in the specifications. Details of overlapping or seaming should be included.
6. Geotextile deployment is usually from the top of slope downward, so that the
geotextile is taut before soil backfilling proceeds.
7. If the upper end of the geotextile should be anchored in an anchor trench, the details
shown in the contract plans should be fulfilled.
8 . Soil backfilling should proceed from the bottom of the slope upward, with a minimum
backfill thickness of 220 mm (9 in.) of cover using light ground contact construction
equipment of 40 kPa (6 lb/m2) contact pressure or less.
9. Seams in geotextiles on side slopes are generally not allowed. If permitted, they
should be located as close to the bottom of the slope as possible. Seams should be as
approved by the CQA engineer. Test strips of seams should be requested for
conformance tests in the CQA laboratory following ASTM D-4884
272
-------
8.6.2 Geogrids
Geogrids are reinforcement geosynthetics formed by intersecting and joining sets of
longitudinal and transverse ribs with resulting open spaces called "apertures". Two different
classes of geogrids are currently available, see Fig. 8.12(a). They are the following: (a) stiff,
unitized, geogrids made from polyethylene or polypropylene sheet material which is cold worked
into a post-yield state, and (b) flexible, textile-like geogrids made from high tenacity polyester
yarns which are joined at their intersections and coated with a polymer or bitumen. Figure 8.12 (b)
shows geogrids being used as veneer reinforcement.
Some recommended contract specification or CQA document items that should be
addressed when using geogrids as reinforcement materials are as follows:
1. A manufacturer's certification should be provided that the geogrid meets the property
criteria specified for the geogrid that was approved for use on the project per the plans
and specifications.
2. CQA personnel should check that the geogrid delivered to the job site is the proper and
intended material. This is done by verifying the identification label and its coding and
by visual identification of the product, its rib joining, thickness and aperture size. If
the geogrid has a primary strength direction it must be so indicated.
3. Conformance samples of the geogrid supplied to the job site should be obtained as per
ASTM D-4759. Typically, the outer wrap of the rolls are used for such sampling.
• 4. Conformance tests should be the following. Aperture size by micrometer or caliper
measurement, rib thickness and junction thickness by ASTM D-1777, and wide width
tensile strength by ASTM D-4595 suitably modified for geogrids. Additional
Conformance tests which may be considered are polymer identification via thermal
analysis methods and single rib tensile strength, via GRI GO 1.
5. Field placement of geogrids should be at the locations indicated on the contract plans
and in the specifications. Details of overlapping or seaming should be included.
6. Geogrid deployment is usually from the top of slope downward, so that the geogrid is
taut before soil backfilling proceeds.
7. If the upper end of the geogrids are to be anchored in an anchor trench, the details
shown in the contract plans should be fulfilled.
8. Soil backfilling should proceed from the bottom of the slope upward, with a minimum
backfill thickness of 22 cm (9.0 in.) of cover using light ground contact construction
equipment of 40 kPa (6 lb/in2) contact pressure or less.
: 9. Connections of geogrid rolls on side slopes should generally be avoided. If permitted,
they should be located as close to the bottom of the slope as possible. Connections
should be as approved by the CQA engineer. Test strips of connections should be
requested for conformance tests in the CQA laboratory following ASTM D-4884
(mod.) test method.
273
-------
(a) Various Types of Geogrids
(b) Geogrids Used as Veneer Reinforcement
Figure 8.12 - Photographs of Geogrids Used as Soil (or Waste) Reinforcement Materials
274
-------
8.7 Geosynthetic Erosion Control Materials
Often on sloping solid waste landfill covers soil loss in the form of rill, gully or sheet
erosion occurs in the topsoil and sometimes extends down into the cover soil. This requires
continuous maintenance until the phenomenon is halted and the long-term vegetative growth is
established. Alternatively, the design may call for a temporary, or permanent, erosion control
system to be deployed within or on top of the topsoil layer. Additional concerns regarding erosion
control are on perimeter trenches, drainage ditches, and other surface water control structures
associated with waste containment facilities. Listed below are a number of alternative erosion
control systems ranging from the traditional hand distributed mulching to fully paved cover
systems. They fall into two major groups; temporary degradable and permanent nondegradable.
Temporary Erosion Control and Revegetation Mats (TERMs)
• Mulches (hand or machine applied straw or hay)
• Mulches (hydraulically applied wood fibers or recycled paper)
• Jute Meshes
• Fiber Filled Containment Meshes
• Woven Geotextile Erosion Control Meshes
• Fiber Roving systems (continuous fiber systems)
Permanent Erosion Control and Revegetation Mats (PERMs)
• Geosynthetic Systems
• turf reinforcement and revegetation mats (TRMs)
• erosion control and revegetation mats (ECRMs)
• geomatting systems
• geocellular containment systems
• Hard Armor Systems
• cobbles, with or without geotextiles
• rip-rap, with or without geotextiles
• articulated concrete blocks, with or without geotextiles
• grout injected between geotextiles
• partially or fully paved systems
Temporary degradable systems are used to enhance the establishment of vegetation and
then degrade leaving the vegetation to provide the erosion protection required. Challenging sites
275
-------
that require protection above and beyond what vegetation can provide need to use a permanent
nondegradatipn system, i.e., high flow channels, over steepened slopes etc. Of these various
alternatives, jute meshes, containment meshes and geosynthetic systems are used regularly on
landfill and waste pile cover systems, see Fig. 8.13.
Some items which are recommended for contract specifications or CQA document for these
particular systems are as follows:
1. The CQA personnel should check the erosion control material upon delivery to see
that the proper materials have been received.
2. Water and ultraviolet sensitive materials should be stored in dry conditions and
protected from sunlight.
3. If the erosion control material has defects, tears, punctures, flaws, deterioration or
damage incurred during manufacture, transportation or storage it should be rejected or
suitably repaired to the satisfaction of the CQA personnel.
4. If the material is to be repaired, torn or punctured sections should be removed by
cutting a cross section of the material out and replacing it with a section of undamaged
material. The ends of the new section should overlap the damaged section by 30 cm
(12 in.) and should be secured with ground anchors.
5. All ground surfaces should be prepared so that the material lies in complete contact
with the underlying soil.
6. Ground anchors, called "pins", should be at least 30 cm (12 in.) long with an
attached oversized washer 50 mm (2.0 in.) in diameter, or "staples" number 8 gauge
"U" shaped wire at least 20 cm (8.0 in.) long. For less severe temporary applications
e.g., TERMS's, one may consider 15 cm (6 in.) number 11 gauge "U" shaped wire
staples.
7. Adjacent rolls of erosion control material shall be overlapped a minimum of 75 mm
(3.0 in.). Staples should secure the overlaps at 75 cm (2.5 ft) intervals. The roll
ends should overlap a minimum of 45 cm (18 in.) and be shingled downgradient.
The end overlaps should be stapled at 45 cm (1.5 ft) intervals, or closer, or as
recommended by the manufacturer.
8. If required on the plans and specifications, the erosion control material should be
filled with topsoil, lightly raked or brushed into the mat to either fill it completely or
to a maximum depth of 25 mm (1.0 in.).
9. For geosynthetic materials used in drainage ditches, their overlaps should always be
shingled downgradient with overlaps as recommended by the manufacturer or plans
and specifications whichever is the greatest.
10. If required by the plans and specifications, the manufacturer of the erosion control or
drainage ditch material should provide a qualified and experienced representative on
site to assist the installation contractor at the start of construction. After an acceptable
routine is established, the representative should be available on an as-needed basis, at
the CQA engineer's request.
276
-------
Figure 8.13 - Examples of Geosynthetic Erosion Control Systems
277
-------
I
Figure 8.13 - Continued
8.8 Floating Geomembrane Covers for Surface Impoundments
In concluding this Chapter, it was felt that a short section on geomembrane floating covers
for liquid wastes contained in surface impoundments is appropriate. These floating covers are
geomembranes of the types discussed in Chapter 3. Hence all details such as polymer type,
production, conformance testing, etc., are applicable here as well. The uniqueness of the
application is that the geomembrane is always exposed to the atmosphere, thus subject to sunlight,
heat, damage, etc., and furthermore it must be rigidly anchored to a concrete anchor trench or other
similar structure, surrounding the perimeter of the facility, see Fig. 8.14.
Some items in addition to those mentioned in Chapter 3 on geomembranes that are
recommended for a contract specification or a CQA document are as follows:
1. Acceptance of the geomembrane should have some verification as to its weatherability
characteristics. The tests most frequently referenced are ASTM D-4355 and ASTM G-
26. There is also a growing body of data being developed under the ASTM G-53 test
method.
2. Other conformance tests, e.g., physical and mechanical property tests, are product
specific and have been described in Chapter 3.
278
-------
Figure 8.14 - Surface Impoundments with Geomembrane Floating Covers along with Typical
Details of the Support System and/or Anchor Trench and Batten Strips
279
-------
3. The anchorage detail for floating covers is critically important. Construction plans and
specifications must be followed explicitly. To be noted is that there are very different
anchorage schemes that are currently available. Some use concrete anchor blocks with
embedded bolts which attach the geomembrane under a batten strip. Other anchorages
are patented systems consisting of tensioned geomembranes attached to movable dead
weights riding inside of stationary columns. Additional schemes are also possible. In
each case the manufacturer's recommendations should be cited in the contract
documents and must be followed completely.
4. The manufacturer/fabricator of the floating cover should provide a qualified and
experienced representative on site to assist the installation contractor at the start of
construction. After an initial start-up point, the representative should be available on an
as needed basis, at the CQA engineer's request.
8.9 References
AASHTO M252-90, "Corrugated Polyethylene Drainage Tubing"
AASHTO M294-90, "Corrugated Polyethylene Pipe, 12- to 36-in. Diameter"
ASTM D-698, "Moisture Density Relations of Soils and Soil/Aggregate Mixtures"
ASTM D-792, "Specific Gravity and Density of Plastics by Displacement"
ASTM D-1238, "Flow Rates of Thermoplastics by Extrusion Plastomer"
ASTM D-1248, "Polyethylene Plastics and Extrusion Materials"
ASTM D-1505, "Density of Plastics by the Density-Gradient Technique"
ASTM D-1755, "Poly (Vinyl Chloride) (PVC) Resins"
ASTMD-1777, "Measuring Thickness of Textile Materials"
ASTMD-1785, "Poly (Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80 and 120"
ASTM D-2122, "Determining Dimensions of Thermoplastic Pipe and Fittings"
ASTM D-2241, "Poly (Vinyl Chloride) (PVC) Pressure Rated Pipe (SDR-Series)"
ASTM D-2321, "Underground Installation of Thermoplastic Pipe for Sewers and Other Gravity -
Flow Applications"
ASTM D-2412, "External Loading Properties of Plastic Pipe by Parallel Plate Loading"
ASTM D-2444, "Impact Resistance of Thermoplastic Pipe and Fittings by Means of a Tup (Falling
Weight)"
ASTM D-3034, "Type PSM Poly (Vinyl Chloride) (PVC) Sewer Pipe and Fittings"
ASTM D-4254, "Maximum Index Density of Soils and Calculation of Relative Density"
280
-------
ASTM D-4355, "Deterioration of Geotextiles from Exposure to Ultraviolet Light and Water
(Xenon-Arc Type Apparatus)
ASTM D-4533, "Trapezoidal Tearing Strength of Geotextiles"
ASTM D-4595, "Tensile Properties of Geotextiles by Wide Width Strip Method"
ASTM D-4632, "Breaking Load and Elongation of Geotextiles (Grab Method)"
ASTM D-4759, "Determining the Specification Conformance of Geosynthetics"
ASTM D-4833, "Index Puncture Resistance of Geotextiles, Geomembranes and Related Products"
ASTM D-4884, "Seam Strength of Sewn Geotextiles"
ASTM F-714, "Polyethylene (PE) Plastic Pipe (SDR-PR) Based on Outside Diameter"
ASTM G-26, "Operating Light-Exposure Apparatus (Xenon-Arc Type) With and Without Water
for Exposure of Nonmetallic Materials"
ASTM G-53, "Operating Light- and Water-Exposure Apparatus (Fluorescent UV - Condensation
Type) for Exposure of Nonmetallic Materials"
GRIGG1, "Geogrid Rib Tensile Strength"
U.S. Environmental Protection Agency (1991), "Inspection Techniques for the Fabrication of
Geomembrane Field Seams," Technical Resource Document, U.S. EPA, EPA/530/SW-
91/051.
281
-------
Appendix A
List of Acronyms
AASHTO American Association of State Highway and Transportation Officials
API American Petroleum Institute
ASTM American Society for Testing and Materials
ATV All-Terrain Vehicle
CB Cement-Bentonite
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CH Fat Clay (ASTM D-2487)
CL Lean Clay (ASTM D-2487)
CPE Chlorinated Polyethylene
CQA Construction Quality Assurance
CQC Construction Quality Control
CSPE Chlorosulfonated Polyethylene
CSPE-R Chlorosulfonated Polyethylene (Scrim Reinforced)
ECRM Erosion Control and Revegetation Mat
EIA Ethylene Interpolymer Alloy
EIA-R Ethylene Interpolymer Alloy - Reinforced
EPA Environmental Protection Agency
EPDM Ethylene Propylene Diene Monomer
FCEA Fully Crosslinked Elastomeric Alloy
FML Flexible Membrane Liner
FTB Film Tear Bond
FTM Federal Test Method
GCL Geosynthetic Clay Liner
GRI Geosynthetic Research Institute
282
-------
HDPE High Density Polyethylene
IFAI Industrial Fabrics Association International
LL Liquid Limit
LLDPE Linear Low Density Polyethylene
MARV Mimimum Average Roll Value
MQA Manufacturing Quality Assurance
MQC Manufacturing Quality Control
NDT Nondestructive Testing
NICET National Institute for Certification in Engineering Technologies
PE Professional Engineer or Polyethylene
PERM Permanent Erosion Control and Revegetation Mat
PI Plasticity Index
PL Plastic Limit
PP Polypropylene
PVC Polyvinyl Chloride
QA Quality Assurance
QC Quality Control
RCRA Resource Conservation and Recovery Act
SB Soil-Bentonite
SC Clayey Sand (ASTM D-2487)
SCB Soil-Cement-Bentonite
SDR Standard Dimension Ratio
TERM Temporary Erosion Control and Revegetation Mats
TGA Thermogravimetric Analysis
TRM Turf Reinforcement and Revegetation Mat
USCS Unified Soil Classification System
283
-------
USP U.S. Pharmaceutical
VLDPE Very Low Density Polyethylene
284
-------
Appendix B
Glossary
Activity—Plasticity index (expressed as a percentage) divided by the clay content (expressed as a
percentage and defined as material finer than 0.002 mm).
Adhesion—The state in which two surfaces are held together by interfacial forces which may
consist of molecular forces or interlocking action or both: (a) measured in shear and peel
modes for geomembranes, (b) measured by direct shear testing for geosynthetics-to-soil.
Adhesive—A chemical system used in the bonding of geomembranes. The adhesive residue
results in an additional element in the seamed area. (Manufacturers and installers should be
consulted for the various types of adhesives used with specific geomembranes).
Aeolian Deposit—Soil deposited by wind.
Air Lance—A commonly used nondestructive geomembrane test method performed with a
stream of air forced through a nozzle at the end of a hollow metal tube to determine seam
continuity and tightness of relatively thin, flexible geomembranes.
All-Terrain Vehicles (ATVs)—Mobile 3-, or 4-wheeled vehicles with low pressure balloon
tires which are used to move small equipment and materials around project sites.
Anchor Trench—The terminus of most geosynthetic materials as they exit a waste containment
facility usually consisting of a small trench where the geosynthetic is embedded and suitably
backfilled.
Antioxidants—Primary types include phenols and amines that scavenge extraneous free radicals
which cause degradation of geosynthetics. Secondary types include decomposed peroxides
as a source of free radicals.
Anvil—In hot wedge seaming of geomembranes, the anvil is the wedge of metal above and below
which the sheets to be joined must pass. The temperature controllers and thermocouples of
most hot wedge devices are located within the anvil.
Apertures—The openings between adjacent sets of longitudinal and transverse ribs of geogrids
and geonets.
Appurtenances—Detailed items related to the proper functioning of a waste containment facility,
such as pipes, sumps, risers, manholes, vents, penetrations and related items.
Atterberg Limits—Liquid limit and plastic limit of a soil.
Basis Weight—A deprecated term for mass per unit area.
Bedding Soil—Compacted layer of soil immediately beneath a leachate collection pipe.
Bentonite—Any commercially processed clay material consisting primarily of the mineral group
smectite.
285
-------
Berm—The upper edge of an excavation which isolates one cell in a containment system from
another. The ends of a geosynthetic are buried to hold them in place or to anchor the
geosynthetics.
Blocking—Unintentional adhesion between geomembrane sheets or between a geomembrane and
another surface usually occurring during storage or shipping.
Blown Film—An extrusion method for producing geomembranes whereby the molten polymer
vertically exits a circular die in the form of a huge cylinder which is subsequently cut
longitudinally, unfolded and rolled into cores.
Blow-Out—Geomembrane rolls or panels which have been unintentionally displaced from their
correct position by wind.
Bodied Chemical Fusion Agent—A chemical fluid containing a portion of the parent
geomembrane that, after the application of pressure and after the passage of a certain amount
of time, results in the chemical fusion of two essentially similar geomembrane sheets, leaving
behind only that portion of the parent material. (Manufacturers and installers should be
consulted for the various types of chemical fluids used with specific geomembranes in order
to inform workers and inspectors.)
Bodied Solvent Adhesive—An adhesive consisting of a solution of the liner compound used
in the seaming of geomembranes.
Boot—A bellows-type covering of a penetration through a geomembrane to exclude dust, dirt,
moisture, etc.
Borrow Material—Excavated material used to construct a component of a waste containment
facility.
Borrow Pit—Excavation area adjacent to, or off-site, the waste containment facility from which
soil will be taken for construction purposes.
Buffing—An inaccurate term often used to describe the grinding of polyethylene geomembranes
to remove surface oxides and waxes in preparation of extrusion seaming.
Calender—A machine equipped with three or more heavy internally heated or cooled rolls,
revolving in opposite direction. Used for preparation of continuous sheeting or plying up of
rubber compounds and frictioning or coating of fabric with rubber or plastic compounds.
[B. F. Goodrich Co. Akron, OH].
Chemical-Adhesive Fusion Agent—A chemical fluid that may or may not contain a portion
of the parent geomembrane and an adhesive that, after the application of pressure and after
passage of a certain amount of time, results in the chemical fusion of two geomembrane
sheets, leaving behind an adhesive layer that is dissimilar from the parent liner material.
(Manufacturers and installers should be consulted for the various types of chemical fluids
used with specific geomembrane to inform workers and inspectors.)
Chemical Fusion—The chemically-induced reorganization in the polymeric structure of the
surface of a polymer geomembrane that, after the application of pressure and the passage of a
certain amount of time, results in the chemical fusion of two essentially similar geomembrane
sheets being permanently joined together.
286
-------
Chemical Fusion Agent—A chemical fluid that, after the application of the passage of a certain
amount of time, results in the chemical fusion of two essentially similar geomemhrane sheets
without any other polymeric or adhesive additives. (Manufacturers and installers should be
consulted for the various types of chemical fusion agents used with specific geomembranes
to inform workers and inspectors.)
Chlorinated Polyethylene (CPE)—Family of polymers produced by the chemical reaction of
chlorine with polyethylene. The resultant polymers presently contain 25-45% chlorine by
weight and 0-25% crystallinity.
Chlorinated Polyethylene-Reinforced (CPE-R)—Sheets of CPE with an encapsulated
fabric reinforcement layer, called a "scrim".
Chlorosulfonated Polyethylene (CSPE)—Family of polymers produced by the reaction of
polyethylene with chlorine and sulphur dioxide. Present polymers contain 23 to 43%
chlorine and 1.0 to 1.4% sulphur. A "low water absorption" grade is identified as
significantly different from standard grades.
Chlorosulfonated Polyethylene-Reinforced (CSPE-R)—Sheets of CSPE with an
encapsulated fabric reinforcement layer, called a "scrim".
Clay Content—The percentage of a material (dry weight basis) with an mean equivalent grain
diameter smaller than a specified size (usually 0.002 or 0.005 mm).
Clod—Term referring to "chunks" of cohesive soil when used for compacted clay liners.
Coated Fabric—Fabric that has been impregnated and/or coated with a rubbery or plastic
material in the form of a solution, dispersion, hot melt, or powder. The term also applies to
materials resulting from the application of a pre-formed film to a fabric by means of
calendering.
Coextrusion—A manufacturing process whereby multiple extruders eject molten polymer into a
die for the purpose of distinguishing properties or materials across the thickness of the
geosynthetic material, as in coextruded HDPE/VLDPE/HDPE geomembranes.
Compaction Curve—An experimentally obtained curve obtained by plotting dry unit weight
versus molding water content, typically used with soil liners.
Composite Liner—A geomembrane placed directly on the surface of a compacted soil liner or
geosynthetic clay liner.
Concentrate—Term commonly used for carbon black premixed with a carrier resin resulting in
pellets which are added to the extruder in the manufacturing of geosynthetic materials.
Construction Quality Control (CQC)—A planned system of inspections that are used to
directly monitor and control the quality of a construction project (EPA, 1986). Construction
quality control is normally performed by the geosynthetics manufacturer or installer, or for
natural soil materials by the earthwork contractor, and is necessary to achieve quality in the
constructed or installed system. Construction quality control (CQC) refers to measures taken
by the installer or contractor to determine compliance with the requirements for materials and
workmanship as stated in the plans and specifications for the project.
287
-------
Construction Quality Assurance (CQA)—A planned system of activities that provide
assurance that the facility was constructed as specified in the design (EPA, 1986).
Construction quality assurance includes inspections, verifications, audits, and evaluations of
materials and workmanship necessary to determine and document the quality of the
constructed facility. Construction quality assurance (CQA) refers to measures taken by the
CQA organization to assess if the installer or contractor is in compliance with the plans and
specifications for a project
Corrugated Pipe—Built-up sections of HDPE drainage pipe manufactured by methods of
corrugation, profiling or spirally wrapping small pipe around an internal core.
CQC Personnel—Individuals who work for contractor whose job it is to ensure that
construction is taking place in accord with the plans and specifications approved by the
permitting agency.
Crystal Structure—The geometrical arrangement of the molecules that occupy the space lattice
of the crystalline portion of a polymer.
Curing—The strength gain over time of a chemically fused, bodied chemically fused, or chemical
adhesive geomembrane seam due primarily to evaporation of solvents or crosslinking of the
organic phase of the mixture.
Curing Time—The time required for full curing as indicated by no further increase in strength
over time.
Deltaic Deposit—Soil deposited in a river delta.
Denier—A unit used in the textile industry to indicate the fineness of continuous filaments as
applies to geotextiles. Fineness in deniers equals the mass in grams of 9000-m length of the
filament.
Density—(a) For geosynthetics, the mass per unit volume of a polymeric material (since there is
no void space, per se); and (b) for soils, the mass per total unit volume, including void space
(note: if the mass is the total mass, i.e., solids plus water, the density is the total density or
bulk density; if the mass is just the dry mass of solids, the density is the dry density of the
soil). * *
Desiccation—Drying that is sufficient to change the properties, such as hydraulic conductivity
of the material.
Design Engineer—An organization or person who designs a waste containment facility that
fulfills the operational requirements of the owner/operator, complies with accepted design
practices for waste containment facilities and meets or exceeds the minimum requirements of
the permitting agency.
Destructive Tests—Tests performed on geomembrane seam samples cut out of a field
installation or test strip to verify specification performance requirements, e.g., shear and peel
tests of geomembrane seams during which the specimens are tested to failure.
Direction, Cross-Machine—The direction perpendicular to the long, machine or manufactured
direction.
288
-------
Direction, Machine—The direction parallel to the long, machine or manufactured direction
(synonyms, lengthwise, or long direction). ,
Dispersion—A qualitative term used to identify the degree of mixing of one component of a
formulation within the total mass, e.g., carbon black dispersion. ,
Drive Rollers—Knurled or rubber rollers which grip two geomembrane sheets to be joined via
applied pressure and propel the seaming device at a controlled rate of travel.
Dumbbell Shaped—-Geomembrane test specimens in the shape of a dumbbell or dogbone, for
subsequent tensile testing. ; '
Dwell Time-^-The time required for a chemical fusion, bodied chemical fusion or adhesive seam
to take its initial "tack", enabling the two opposing geomembranes to be joined together.
Earthwork Contractor—The organization mat is awarded the subcontract from the general
contractor, or contract from the owner/operator, to construct the earthen components of the
waste containment facility. ....... .
Embossing—A method of providing a textured, a roughened, surface to calendered
geomembranes for the purpose of increasing its friction to adjacent materials.
Ethylene Interpolymer Alloy (EIA)—A blend of ethylerie vinyl acetate and polyvinyl
chloride resulting in a thermoplastic elastomer.
Ethylene Interpolymer Alloy-Reinforced (EIA-R)—Sheets of EIA with an encapsulated
fabric reinforcement layer.
Extrudate—The molten polymer which is emitted from an extruder during seaming using either
extrusion fillet or extrusion flat methods. The polymer is initially in the form of a ribbon,
rod, bead or pellets.
Extruder—A machine with a driver screw for continuous forming of polymeric compounds by
forcing through a die; two types are used in the manufacturing of geomembranes, flat die and
blown film.
Extrusion Seams—A seam of two geomembrane sheets achieved by heat-extruding a polymer
material between or over the overlap areas followed by the application of pressure.
Fabricator—The organization that factory assembles, rolls of geosynthetic materials into large
panels for subsequent field deployment.
Fabric, Composite—A textile structure produced by combining nonwoven, woven, or knit
manufacturing methods.
Fabric, Knit—A textile structure produced by interloping one or more ends of yarn or
comparable material.
Fabric, Nonwoven—For geotextiles, a planar and essentially random textile structure produced
by bonding, interlocking of fibers, or both, accomplished by mechanical, chemical, thermal,
or solvent means, and combinations thereof.
289
-------
Fabric, Reinforcement—A fabric, scrim, and so on, used to add structural strength to a two-or
more ply polymeric sheet. Such geomembranes are referred to as being supported.
Fabric, Woven—A planar textile structure produced by interlacing two or more sets of elements
such as yarns, fibers, roving, or filaments, where the elements pass each other, usually at
right angles and one set of elements are parallel to the fabric axis.
Factory Seams—The seaming of geomembrane rolls together in a factory to make large panels
to reduce the number of field seams.
Field Seams—The seaming of geomembrane rolls or panels together in the field thereby making
a continuous liner system.
Filament Yarn—The yarn made from continuous filament fibers.
Fill—As used in textile technology refers to the threads or yarns in a fabric running at right angles
to the warp. Also called filler threads.
Filling Direction—See Direction, cross-machine. Note: For use with woven geotextiles only.
Film Tear Bond (FTB)—Description of a destructive geomembrane seam test (shear or peel)
wherein the sheet on either side of the seam fails rather than delamination of the seam itself.
Filter Cloth—A deprecated term for geotextile.
Fines—Material passing through the No. 200 sieve (opennings of 0.075 mm)
Fishmouth—The uneven mating of two geomembranes to be joined wherein the upper sheet has
excessive length that prevents it from being bonded flat to the lower sheet. The resultant
opening is often referred to as a "fishmouth".
Flashing—The molten extrudate or sheet material which is extruded beyond the die edge or
molten edge of a thermally bonded geomembrane seam, also called "squeeze-out".
Flat Die—An extrusion method for producing geomembranes whereby the molten polymer
horizontally exists a flat die in the form of a wide sheet which is subsequently rolled onto
/*rt1*O O T. •/
cores.
Flexible Membrane Liner (FML)—Name previously given in EPA literature for the more
generic term of geomembrane. The latter is used exclusively in this manual.
Flood Coating—The generous application of a bodied chemical compound, or chemical
adhesive compound to protect exposed yarns in scrim reinforced geomembranes.
Formulation—The blending of several components (resin plus additives) to make a mixture for
subsequent processing into a geosynthetic material.
Fully Crosslinked Elastomeric Alloy (FCEA)—A thermoplastic elastomeric alloy of
polypropylene (PP) and ethylene-propylene diene monomer (EPDM).
Gage—Deprecated term for the-thickness of a geosynthetic material.
290
-------
General Contractor—The organization that is awarded a contract from the owner/operator to
construct a waste containment facility.
Geocell—A three-dimensional structure filled with soil, thereby forming a mattress for increased
bearing capacity and maneuverability on loose or compressible subsoils.
Geocomposite—A manufactured material using geotextiles, geogrids, geonets, and/or
geomembranes in laminated or composite form.
Geogrid—A geosynthetic used for reinforcement which is formed by a regular network of tensile
elements with apertures of sufficient size to allow strike-through of surrounding soil, rock,
or other geotechnical materials..
Geomembrane—An essentially impermeable geosynthetic composed of one or more synthetic
sheets.
Geonet—A geosynthetic consisting of integrally connected parallel sets of ribs overlying similar
sets at various angles for planar drainage of liquids and gases.
Geosynthetic Clay Liner (GCL)—Factory manufactured, hydraulic barrier typically
consisting of bentonite clay or other very low permeability material, supported by geotextiles
and/or geomembranes which are held together by needling, stitching and/or chemical
adhesives.
Geosynthetics—The generic term for all synthetic materials used in geotechnical engineering
applications; the term includes geotextiles, geogrids, geonets, geomembranes, geosynthetic
clay liners and geocomposites.
Geotechnical Engineering—The engineering application of geotechnics.
Geotechnics—The application of scientific methods and engineering principles to the acquisition,
interpretation, and use of knowledge of materials of the earth's crust to the solution of
engineering problems; it embraces the field of soil mechanics, rock mechanics, and many of
the engineering aspects of geology, geophysics, hydrology, and related sciences.
Geotextile—A permeable geosynthetic comprised solely of textiles. Current manufacturing
techniques produce nonwoven fabrics, knitted (non-tubular) fabrics, and woven fabrics.
Glacial Till—A soil of varied grain sizes deposited by glacial action.
Gravel—Material that will not pass through the openings of a No. 4 sieve (4.76 mm openings)
Grinding—The removal of oxide layers and waxes from the surface of a polyethylene sheet in
preparation of extrusion fillet or extrusion flat seaming.
Gun—Synonymous term for hand held extrusion fillet device or hand held hot air device.
Haunch Area—The location of a buried pipe which extends for the lower 180° around the bottom
outside of the pipe.
Heat Bonded—See Melt-bonded.
291
-------
Heat-Seaming—The process of joining two or more thermoplastic geomembranes by heating
areas in contract with each other to the temperature at which fusion occurs. The process is
usually aided by a controlled pressure. In dielectric seaming the heat is induced by means of
radio-frequency waves.
High Density Polyethylene (HOPE)—A polymer prepared by low-pressure polymerization
of ethylene as the principal monomer and having the characteristics of ASTM D-1348 Type
HI and IV polyethylene. Such polymer resins have density greater than or equal to 0.941
g/cc as noted in ASTM D-1248.
Hook Blade—A shielded knife blade confined in such a way that the blade cuts upward or is
drawn toward the person doing the cutting to avoid damage to underlying sheets.
Hydraulic Conductivity—The rate of discharge of water under laminar flow conditions
through a unit cross-sectional area of a porous medium under a unit hydraulic gradient and
standard temperature conditions (20°C).
Initial Reaction Time—(See dwell time).
Installation Contractor—The organization that is awarded a subcontract from the general
contractor or owner/operator, to install geosynthetic materials in the waste containment
facility.
Kneading Compaction—Compaction of a soil liner whereby a foot or prong is repeatedly
passed into and through a lift of soil.
Lacustrine Deposit—A soil deposited in a stagnent body of water, e.g., lake.
Lapped Seam—A seam made by placing one surface to be joined partly over another surface and
bonding the overlapping portions.
Leachate—Liquid that has percolated through or drained from solid waste or other man-emplaced
materials and contains soluble, partially soluble, or miscible components removed from such
ti/oof^
waste.
Let-Down—Term used for the addition of carbon black powder or concentrated pellets into an
extruder in the manufacturejof geosynthetic materials.
Lift—Term applied to the construction of a discrete layer of a soil liner, usually 150 to 225 mm (6
to 9 in.) in thickness.
Liner—A layer of emplaced materials beneath a surface impoundment or landfill which serves to
restrict the escape of waste or its constituents from the impoundment or landfill. The term
can apply to soil liners, geomembranes or geosynthetic clay liners.
Linear Low Density Polyethylene (LLDPE)—A polyethylene material produced by a low
pressure polymerization process with random incorporation of comonomers to produce a
Liquid Limit (LL)—The water content corresponding to the arbitrary limit between the liquid
292
-------
and plastic states of consistency of a soil.
Manhole—A vertical pipe rising from a sump area through the waste mass and eventually
penetrating the cover for the purpose of leachate removal.
Manufacturer—The organization that manufactures geosynthetic materials used at a waste
containment facility.
Manufacturing Quality Assurance (MQA)—A planned system of activities that provide
assurance that the materials were constructed as specified in the certification documents and
contract plans. MQA includes manufacturing facility inspections, verifications, audits and
evaluation of raw materials and geosynthetic products to assess the quality of the
manufactured materials. MQA refers to measures taken by the MQA organization to
determine if the manufacturer is in compliance with the product certification and contract
plans for a project.
Manufacturing Quality Control (MQC)—A planned system of inspections that is used to
directly monitor and control the manufacture of a material which is factor originated. MQC is
normally performed by the manufacturer of geosynthetic materials and is necessary to ensure
minimum (or maximum) specified values in the manufactured product. MQC refers to
measures taken by the manufacturer to determine compliance with the requirements for
materials and workmanship as stated in certification documents and contract plans.
Mass Per Unit Area—The proper term to represent and compare the amount of material per unit
area (units are oz./yd.2 or g/m2). Often called "weight" or "basis weight".
Medium Density Polyethylene (MDPE)—A polymer prepared by low-pressure
polymerization of ethylene as the principal monomer and having the characteristics of ASTM
D-1348 Type II polyethylene. Such polymer resins have density less than 0.941 g/cc as
noted in ASTM D-1248.
Melt-Bonded—Thermally bonded by melting the fibers to form weld points.
Membrane—A continuous sheet of material, whether prefabricated as a geomembrane or sprayed
or coated in the field, as a sprayed-on asphalt/polymer mixture.
Minimum Average Roll Value (MARV)—A statistical value of a particular test property
which embraces the 95% confidence level of all possible values of that property. For a
normally distributed set of data it is approximately the mean value plus and minus two
standard deviations.
Modified Compaction—A laboratory technique that produces maximum dry unit weights
approximately equal to field dry units weights for soils that are well compacted using the
heaviest compaction equipment available (ASTMD-1557).
Mouse—Synonymous term for hot wedge, or hot shoe, seaming device.
MQA/CQA Certifying Engineer—The individual who is responsible for certifying to the
owner/operator and permitting agency that, in his or her opinion, the facility has been
constructed in accord with the plans and specifications and MQA/CQA document approved
by the permitting agency.
293
-------
MQA/CQA Engineer—The individual who has overall responsibility for manufacturing quality
assurance and construction quality assurance.
MQA/CQA Personnel—Those individuals responsible for making observations and performing
field tests to ensure that the facility is constructed in accord with the plans and specifications
approved by the permitting agency.
MQA/CQA Plan—A written plan, or document, prepared on behalf of the owner/operator which
includes a detailed description of all MQA/CQA activities that will be used during materials
manufacturing and construction to manage the installed quality of the facility.
Needle-Punched—A nonwoven geotextile which is mechanically bonded by needling with
barbed needles.
NICET—An acronym for the National Institute for Certification in Engineering Technologies, an
. organization who administers examinations for geosynthetic and earthen materials for waste
containment facilities. [NICET, 1420 King Street, Alexandria, VA 22314]
Nondestructive Test—A test method which does not require the removal of samples from, nor
damage to, the installed liner system. The evaluation is done in an in-situ manner. The
results do not indicate the seam's mechanical strength but are performed for examination for
the seam's continuity.
Nonwoven—See Fabric, nonwoven.
Normal Direction—For geotextiles, the direction perpendicular to the plane of a geotextile.
Outliers—Experimental data points which do not fit into the anticipated and/or required maxima,
or minima, specified values.
Owner/Operator—The organization that will own and operate the disposal unit.
Owner's Representative—The official representative who is responsible for coordinating
schedules, meetings and field activities.
Oxide Layer—The reacting of atmospheric oxygen with the surface of a polymer geomembrane.
Padfoot Roller—Footed, or padded, roller typically consisting of 4.0 in. long pads used to
compact soil liners.
Panels—The factory fabrication of geomembrane rolls into relatively large sections, or panels, so
as to reduce the number of field seams.
Peel Test—A geomembrane seam test wherein the seam is placed in a tension state as the
geomembrane ends are pulled apart.
Permeability—(1) The capacity of a porous medium to conduct or transmit fluid; (2) the amount
of liquid moving through a barrier in a unit time, unit area, and unit gradient not normalized
for, but directly related to, thickness. See Hydraulic Conductivity.
Permitting Agency—Often a state regulatory agency but may include local or regional agencies
and/or other federal agencies.
294
-------
Permittivity—For a geotextile, the volumetric flow rate of water per unit cross-section area, per
unit head, under laminar flow conditions, in the normal direction through the fabric.
pH—A measure of the acidity or alkalinity of a solution; numerically equal to the logarithm of the
reciprocal of the hydrogen ion concentration in gram equivalents per liter of solution. pH is
represented on a scale of 0 to 14; 7 represents a neutral state; 0 represents the most acid, and
14 the most alkaline. ; : , . .
Pinholes—Very small imperfections in geomembranes which may allow for escape of the
contained liquid.
Piping—The phenomenon of soil fines migrating out of a soil mass by flow of liquid leaving a
small channel, or pipe, in the upstream soil mass.
Plastic—A material that contains as an essential ingredient one or mpre organic polymeric
substances of large molecular .weight which is solid in its finished state, and at some stage in
its manufacture or processing into finished articles can be shaped by flow [ASTM].
Plastic Index (PI)-^-The numerical difference between liquid and plastic limits, i.e., LL-PL.
Plastic Limit (PL)—The water content corresponding to the arbitrary limit between the plastic
and solid states of consistency of a soil.
Plasticizer—A plasticizer is a material, frequently "solventlike," incorporated in a plastic or a
rubber to increase its ease of workability, its flexibility, or distensibility. Adding the
plasticizer may lower the melt viscosity, the temperature of the second-order transition, or the
elastic modulus of the polymer. Plasticizers may be mpnomeric liquids (phthalate esters),
low-molecular-weight liquid polymers (polyesters), or rubbery high polymers (EVA).. The
most important use of plasticizers in geosynthetics is with PVC geomembranes, where the
choice of plasticizer will dictate under what conditions the liner may be used.
Plugging—The phenomenon of soil fines migrating into and clogging the voids of larger particle
sized soils within a soil mass or geotextile filter. Y
Ply—individual layer of material, usually sheet of geomembrane, which is; laminated to another,
or several, layers to form the complete geomembrane.
Ply Adhesion—The bonding force required to bre~ak the adhesive bond of one layer, or material,
to another. It is usually evaluated by some type of tension peel test.
Polyester Fiber—Generic name for a manufactured fiber in which the;fiber-forming substance
is any long-chain synthetic polymer composed of an ester of a dihydric alcohol and
terephthalic acid. r
Polyethylene (PE)—A polyolefin formed by bulk polymerization (for low density) or solution
polymerization (for high density) where the ethylene monomer is placed in a reactor under
high pressure and temperature. The oxygen produces free radicals which initiate the chain
polymerization. For solution polymerization the monomer is first dissolved in an inert
solvent. Catalysts are sometimes required to initiate the reaction.
Polymer—A macromolecular material formed by the chemical combination of monomers having
295
-------
either the same or different chemical composition. Plastics, rubbers, and textile fibers are all
high-molecular-weight polymers.
Polymeric Liner—Plastic or rubber sheeting used to line disposal sites, pits, ponds, lagoons,
Canals, and so on.
Polyolefin—A family of polymeric materials that includes polypropylene and polyethylene the
former being very common in geotextiles, the latter in geomembranes. Many variations of
C3.cn exist.
Polypropylene—A polyolefin formed by solution polymerization as was described for high
density polyethylene. • 6
Polyvinyl Chloride (PVC)—A synthetic thermoplastic polymer prepared from vinylchloride
PVC can be compounded into flexible and rigid forms through the use of plasticizers,
stabilizers, fillers, and other modifiers; rigid forms used in pipes and well screens: flexible
forms used in manufacture of geomembranes.
Pressure Rollers—Rollers accompanying a seaming technique which apply pressure to the
opposing geomembrane sheets to be joined. They closely follow the actual melting process
and are self-contained within the seaming device.
Pressurized Dual Seam—A thermal fusion method of making a geomembrane whereby a
unbonded space is left between two parallel bonded tracks. The unbonded space is
subsequently used for a nondestructive air pressure test.
Proctor Test—The tests utilized to obtain a laboratory compaction curve. Synonymous to
comnacfinn tp.sf J J
compaction test.
Puckering— A heat related sign of localized strain caused by improper seaming using extrusion
1'" n ^^ ™ ** bOtt°m °f *e 1OWCr Seomembrane and "» the shape
Pugmill— A mechanical device used for mixing of dry soil materials.
Quality Assurance (QA)— A planned system of activities that provide assurance that the facility
was constructed as specified in the design.
Quality Control (QC)— A planned system of inspections that are used to directly monitor and
control the quality of a construction project.
Reclaim— Small pieces, or chips, of previously used polymer materials which are entered into the
processing of a geosynthetic material,. Synonymous with "reprocess" and "recycle".
Record Drawings— Drawings which document the actual lines and grades and conditions of
eacn component of the disposal unit. Synonymous with "as-built" drawings.
Regrind— Small pieces, or chips, of previously fabricated geosynthetic material which are re-
"Swork" Processmg of the same type of geosynthetic material, synonymous with
Residual Soil— Soil formed in place from weathering of parent rock.
296
-------
Risers—Pipelines extending from primary or secondary leachate collection sumps up the
sideslope of the facility and exiting to a shed or manhole.
Rolling Bank—A charge of molten polymer used in the calendering production method of
geomembranes for the purpose of directing the flow of polymer in the desired roll direction.
Scrim Designation—The weight of number of yarns of fabric reinforcement per inch of length
and width, e.g., a 10 x 10 scrim has 10 yarns per inch in both the machine and cross
machine directions.
Scrim (or Fabric) Reinforcement—The fabric reinforcement layer used with some
geomembranes for the purpose of increased strength and dimensional stability.
Sealant—A viscous chemical used to seal the exposed edges of scrim reinforced geomembranes.
(Manufacturers and installers should be consulted for the various types of sealant used with
specific geomembranes). , / ,-
Sealed Double Ring Infiltrometer (SDRI)—A device used for measuring in-situ hydraulic
conductivity of a test pad for a soil liner.
Seam Strength—Strength of a seam of liner material measured either in shear or peel modes.
Strength of the seams is reported either in absolute units (e.g., pounds per inch of width) or
as a percent of the strength of the geomembrane. . ..< .
Seaming Boards—Smooth wooden planks placed beneath the area to be seamed to provide a
uniform resistance to applied roller pressure in the fabrication of geomembrane seams.
Selvage—The longitudinal edges of woven geotextile in which the weft yarns fold back upon
themselves. In fabric reinforced geomembranes selvage refers to edge of the rolls where no
scrim is present. • >
Shear Test—A geomembrane seam test wherein the seam is placed in a shear state as the
geomembrane ends are pulled apart.
Sheepsfoot Roller—Footed, or pronged, roller typically consisting of,8.0 in. long feet used to
compact soil liners.
Sheeting—A form of plastic or rubber in which the thickness is very small in proportion to length
and width and in which the polymer compound is present as a continuous phase throughout,
with or without fabric, synonymous with geomembrane."
Shielded Blade—A knife within a housing which protects the blade from being used in an open
fashion, i.e., a protected knife.
Slope—Deviation of a surface from the horizontal expressed as a percentage, by a ratio, or in
degrees. In engineering, usually expressed as a percentage of vertical to horizontal change
[EPA].
Slurry Wall—A construction technique whereby a vertical sided trench is supported by means of
the hydrostatic pressure of a clay-water suspension ("slurry") placed within it.
297
-------
Smectite—A group of expandable clay minerals with a very large ratio of surface area to mass a
large negative surface charge, a high cation exchange capacity, and a high shrink-swell
potential.
Soil Liners—Low-hydraulic-conductivity materials constructed of earthen materials that usually
contain a significant amount of clay.
Solvent, Bodied Solvent and Solvent Adhesive—See Chemical Fusion, Bodied Chemical
Fusion and Chemical Adhesive.
Spotting—The final placement, or positioning, of a geomembrane roll or panel prior to field
seaming.
Spread-Coating—A manufactured process whereby a polymeric material is spread in a
continuous fashion on a geotextile substrate thereby forming a reinforced geomembrane
composite.
Squeeze-Out—See "flashing".
Standard Compaction—A laboratory technique which produces maximum dry unit weights
approximately equal to field dry unit weights for soil that are well compacted using modest-
sized compaction equipment.
Staple—Short fibers in the range 0.5 to 3.0 in. (1 cm to 8 cm) long.
Staple Yarn—Yarn made from staple fibers.
Stinger—A long steel rod on the end of a front end loader or fork lift which is inserted into the
core of a roll of geosynthetic material for the purpose of lifting and maneuvering.
Stress Crack— An external or internal crack in a plastic caused by tensile stresses less than its
short-time mechanical strength. Note: The development of such cracks is frequently
accelerated by the environment to which the plastic is exposed. The stresses which cause
cracking may be present internally or externally or may be combinations of these stresses.
Strike-through—The penetration of one material into and/or through the openings of an adjacent
planar material. J
Substrate—The layer, or unit, that is immediately beneath the layer under consideration.
Sumps—A low area in a waste facility which gravitationally collects leachate from either the
primary or secondary leachate collection system.
Superstate—The layer, or unit, that is immediately above the layer under consideration.
Support Sheeting—See Fabric reinforcement.
Tack—Stickiness of a geomembrane or the temporarily welding of geomembranes together.
Tenacity—The fiber strength on a grams per denier basis.
Tensiometer—A field measuring device containing a set of opposing grips used to place a
298
-------
geomembrane sheet or seam in tension for evaluating its strength.
Testing Laboratory—The testing laboratory(s) providing testing services to verify physical,
mechanical, hydraulic or endurance properties of the materials used to construct the waste
containment facility. . ,
Test Pads—Prototype layer or layers of soil materials constructed for the purpose of simulating
construction conditions and/or measuring performance characteristics. Test pads are most
frequently used to verify that the materials and methods of construction proposed for a soil
liner will lead to development of the desired low hydraulic conductivity.
Test Strips—Trial sections of seamed geomembranes used (1) to establish machine settings of
temperature, pressure and travel rate for a specific geomembrane under a specific set of
atmospheric conditions for machine-assisted .seaming and (2) to establish methods and
materials for chemical and chemical adhesive seams under a specific set of atmospheric
conditions.
Test Welds—See "test strips".
Tex—Denier multiplied by 9 and is the weight in grams of 1000 m of yarn.
Textured Sheet—Polyethylene geomembranes which are produced with a roughened surface via
coextrusion, impingement or lamination so as to create a high friction surface(s).
Thermal Fusion—The temporary, thermally-induced reorganization in the polymeric make-up of
the surface of a polymeric geomembrane that, after the application of pressure and the
passage of a certain amount of time, results in the two geomembranes being permanently
joined together.
Thermoplastic Polymer—A polymer that can be heated to a softening point, shaped by
pressure, and cooled to retain that shape. The process can be done repeatedly.
Thermqset Polymer—A polymer that can be heated to a softening point, shaped by pressure,
and, if desired, removed from the hot mold without cooling. The process cannot be repeated
since the polymer cannot be resoftened by the application of heat.
Trampolining—The lifting of a geomembrane off of its subbase material due to thermal
contraction and inadequate slack which can occur at the toe of slope or in corners of a facility.
Transmissivity—For a geotextile, the volumetric flow rate per unit thickness under laminar flow
conditions, within the in-plane direction of the fabric. •
Transverse Direction—A deprecated term for cross-machine direction.
Tremie—A method of hydraulic placement of soil, or other material, under a head of water.
Ultraviolet Degradation—The breakdown of polymeric structure when exposed to natural
light.
Unsupported Geomembrane—A polymeric geomembrane consisting of one or more piles
without a reinforcing-fabric layer or scrim.
299
-------
Vacuum Box—A commonly used type of nondestructive test method which develops a vacuum
in a localized region of a geomembrane seam in order to evaluate the seam's tightness and
suitability.
Veneer Reinforcement—Geogrid or geotextile reinforcement layer(s) which placed in the soil
covering a geomembrane for the purpose of side slope stabilization.
Very Low Density Polyethylene (VLDPE)—A linear polymer of ethylene with other alpha-
olefins with a density of 0.890 to 0.912 g/cc.
Virgin Ingredients—Components of a geosynthetic formulation which have never been used in
a prior formulation or product.
Warp—In textiles, the lengthwise yarns in a woven fabric.
Waxes—The low molecular weight components of some polyethylene compounds which migrate
to the surface over time and must be removed by grinding (for polyethylene) or be mixed into
the melt zone using thermal seaming methods.
Weft—A deprecated term for cross-machine direction.
Wick ing—The phenomenon of liquid transmission within the fabric yarns of reinforced
geomembranes via capillary action.
Width—For a geotextile, the cross-direction edge-to-edge measurement of a fabric in a relaxed
condition on a flat surface.
Woof—A deprecated term for cross-machine direction.
Woven—See Fabric, woven.
Woven, Monofilament—The woven geotextile produced with monofilament yarns.
Woven, Multifilament—The woven geotextile produced with multifilament yarns.
Woven, Slit-Film—The woven fabric produced with yarns produced from slit film.
Woven, Split-Film—See Woven, slit-film.
Yarn—A generic term for continuous strands of textile fibers or filaments in a form suitable for
knitting, weaving, or otherwise intertwining to form a textile fabric. Yarn may refer to (1) a
number of fibers twisted together, (2) a number of filaments laid together without twist (a
zero-twist yarn), (3) a number of filaments laid together with more or less twist, or (4) a
single filament with or without twist (a monofilament).
Zero Air Voids Curve—A curve that relates dry unit weight to water content for a saturated soil
that contains no air.
300
-------
Appendix C
Index
Acceptable Zone 30-34
Access Ramps 268-270
Air Lance 162, 163, 166
Anchor Trenches 266-268
As-Built Drawings 13-14
Backhoe 244
Backscattering 59-60
Bentonite 19,40-42, 68-72
Bentonite 176-177
Bentonite Blankets 174
Bentonite Mats 174
Bentonite Slurry . 241-243
Boutwell Test- see Two Stage Borehole Test
Butterfly Seam 214,215
Calcium Carbide Gas Pressure Tester 54
Certification 14
Chlorosulfonated Polyethylene 107-110, 129-131
Additives 109
Calendering 129-131
Carbon Black 109
Fillers 109
Master Batch 129
Panel Fabrication 131
Reinforcing Scrim 109-110
Reinforcing Scrim 129
Resin 107-108
Scrim 129
Clamshell 245
Clay Blankets 174
Clay Mats 174
Compacted Soil Liners
Activity 39
Atterberg Limits 62-63, 65,73-75
Bentonite-Soil Blends 19
Borrow Sources Inspection 61-67
Clay Content 39-41, 63
Clod Pulverization 68
Clod Size 39-40, 75
Compaction Equipment 76-78
Compaction Principles 46-51
Compaction Requirements and Curve
24-33,49-51, 62-63, 65, 73-74
Compactive Energy 48-51
Construction Requirements 21-24
Corrective Action 75, 82
Coverage (Compactor) 77
Critical CQC and CQA Issues 21
Density (Measurement) 57-60, 65,
78-82
Desiccation 53,86
Freezing 53,86-88
Homogenizing Soils 68
Compacted Soil Liners (continued)
Hydraulic Conductivity (In Situ)
91-95
Hydraulic Conductivity Testing
63-65, 75, 82-85, 91-95
Lift Bonding 52
Lift Thickness 75-76,85
Liquid Limit 62-63,65, 73-75
Materials 23, 35-45, 61-67, 73-75
Maximum Particle Size 39, 62-63,
65, 73-75
Natural Mineral Materials 19
Outliers 80-82
Oversight (Construction) 74, 79
Oversized Particle Removal 68
Pass/Fail Decision 85
Passes of Compaction 77-79
Penetrations- Repair 85
Percent Fines 37,62-63,65, 73-75
Percent Gravel 38,62-63,65, 73-75
Placement of Soil 72-73,75-76
Plasticity Index 62-63,65, 73-75
Plastic Limit 62-63, 65, 73-75
Plasticity 35-37, 41, 62-63, 65, 73-75
Preprocessing 23,67-72
Protection 24, 53, 86-88
Sampling Pattern 78, 80
Scarification 73
Stockpiling Soils 72
Subgrade Preparation 22
Test Pads 34-35,88-95
Types 19
Water (Excess Surface) 88
Water Content (Adjustment) 67-68
Water Content (Measurement) 53-55,
62,65, 78-82
Water Content (Molding) 42-45
Water Content-Density Specification
30-34,49-51, 63-64
Compaction Curve 24-26, 63
Compaction Tests 26-29
Construction Fabrics 202
Construction Quality Assurance 1,2-3
Construction Quality Control 1, 2
CQC Personnel 7
Design Engineer 5
Diaphragm-Wall Construction 249,250
Direct Heat Drying of Soil 54
Document Control 14
Documentation 11
Drainage Geocomposites 226-228
301
-------
Drainage Materials 191-200
Borrow Sources 196
Compaction 198-199
Placement 197-198
Processing 196-197
Protection 199-200
Drainage Trenches 197
Drawings of Record 13-14
Drive Cylinder 57,59
Earthwork Contractor 7
Edge Drains 226,228
Electric Field 163,164
Electric Sparking 164
Electric Wire 163,164,166
Fabricator 6
Filter Cake 239
Filter Fabrics 202 ,
Filters (Soil) 193-194
Filtrate Loss 243
Flash Operation 242
Flat Seam 214,215,216
Flexible Membrane Liners- see Geomembranes
Floating Geomembrane Covers 278-280
Footed Roller 47-48
Free Swell of Bentonite 69-70
General Contractor 6
Geocomposites 225-233
Acceptance and Conformance Testing
231-232
Covering 233
Handling 231-232
Joining 232-233
Manufacturing 228-231
Packaging 231
Placement 232
Shipment 231
Storage at Field Site 231
Storage at Manufacturing Facility
Types 225-227
Geogrid 271,273-274
Geomembrane Walls 238
Geomembranes
Acceptance and Conformance Testing
135-136
Adhesive Seaming 142-146
Anchor Trenches 266-268
Blocking 138
Bodied Chemical 143,144
Chemical 143
Chemical Adhesive 143,144
Chemical Fusion 142-146
Chemical Processes 142
Chlorinated Polyethylene 110
Coextruded 105
Coextrusion 123-124
Geomembranes (continued)
Contact Adhesive 143,144
Control Charts 153
Crack 138
Craze 138
Critical Cone Heights 167
Destructive Test Methods 150-161
Distort 138
Dual Hot Wedge 143
Ethylene Interpolymer Alloy 110
Ethylene-Propylehe Diene Monomer
105-106
Expansion/Contraction 139-140, 168,
170
Extrusion Fillet 144
Extrusion Flat 144
Extrusion Welding 142-146
Field Seaming Methods 141-146
Field Tensiometer 147-148
Fillet-Type 143
Film Tear Bond 156,158
Fixed Increment Sampling 151-152
Flat-Type 143
Foaming Agent 105
Formulations 99
Fully Crosslinked Elastomeric Alloys
106
Geosynthetic Covering 170
Hot Air 144
Hot Shoe 144
Hot Wedge 144
Joining 141-150
Melt Bonding 142-146
Method of Attributes 153
Non-Film Tear Bond 156, 158
Nondestructive Test Methods
161-166
Peel Strength Efficiency 159
Peel Testing 157-160
Placement 136
Polypropylene 105
Polypropylene 110
Randomly Selected Sampling
152-153
Reclaimed 113
Recycled 113
Regrind 111-113
Rework 111-113
Sampling Strategies 151 -153
Seam Shear Efficiency 156-157
Seaming 141-150
Shear Testing 153-157
Single Hot Air 143
Slack 139
Soil Backfilling of Geomembranes
167-170
302
-------
Geomembranes (continued)
Spotting 140
Spread Coated Geomembranes ,
131-132
Sticking/Cracking 138
Subgrade (Subbase) 136-138
Test Strips 146-150
Textured 105
Textured Sheet 117-119,121-123
Thermal Fusion 142-146 «
Thermal Processes 142
Trampolining 139
Trial Seams 146-150
Trim Reprocessing 111-113
Types 99
Wind 140-141
Geonets 218-226
Acceptance and Conformance Testing
222
Extruder 218
Foamed Rib Geonet 221
Handling 221-223
Joining 223-225
Manufacturing 218,220-221
Packaging 222
Placement 223
Reclaimed 221
Recycled 221
Regrind 221
Resins 218,221
Rework 221
Shipment 222
Solid Rib Geonet 221
Storage at Manufacturing Facility
222
Storage at the Site 222
Geopipe 253-261
Conformance Testing and Acceptance
259-260
High Density Polyethylene 254
High Density Polyethylene Corrugated
257-258
High Density Polyethylene Smooth
Wall 256-257
Packaging 259
Placement 261
Polyvinyl Chloride 254-256
Profiled 257
Rework 255
Shipment 259
Storage at Field Site 259
Storage at Manufacturing Facility
259
Geospacers 225
Geosynthetic Clay Liners
Acceptance and Conformance Testing
184-185
Adhesive Bound 174,175
Backfilling 188-189
Bentonite 176-177
Covering 188-189
Handling 180-185
Installation 185-188
Joining 187
Manufacturing 176-179
Needle Punched 174,175
Placement 185-187
Repairs 187-188
Shipment 181, 182
Stitch Bonded 174,175
Storage at the Manufacturing Facility
180-181
Storage at the Site 181,183-184
Types 174-176
Geosynthetic Erosion Control Materials
275-278
Geotextile Reinforcement 271-273
Geotextiles 202-218 ,,
Acceptance and Conformance Testing
212-213
Additives 204-206
Backfilling 217-218
Covering 217-218
Fiber Types 206
Handling 210-214
Heat Bonded 207,209
Knit 207
Manufacturing 202-210
Needlepunched 207,208
Nonwoven 207,208-209
Placement 213-214
Polyester 204-205
Polypropylene 204
Protective Wrapping 210
Reclaimed 209-210
Recycled 209-210
Repairs 217
Resins 204-206
Seam Tests 217
Seaming 214-217
Shipment 212
Storage at Field Site 211,212
Storage at Manufacturing Facility
210-212
Types 207
Woven 207,208
Hazen's Formula 191
High Density Polyethylene 99-103,113-119,
254, 256-258
Additives 103
303
-------
High Density Polyethylene (continued)
Blown Film 113,115-117
Carbon Black 101-103
Coextrusion 117,118
Corrugated Pipe 257-258
Extruder 113
Flat Horizontal Die 113,114-115
Impingement 118,119
Lamination 118,119
Reclaimed Material 101
Regrind Chips 101
Resin 100-101
Rework Chips 101
Smooth Wall Pipe 256-257
Impact Compaction 46
Installation Contractor 6-7
J Seam 214,215
Kneading Compaction 46
Line of Optimums 51
Manholes 261-264
Manufacturer 5
Manufacturing Quality Assurance 1,2
Manufacturing Quality Control 1,2
Mechanical Point Stress 162,163,166
Meetings 15-17
Pre-Bid 15
Preconstruction 16-17
Progress 17
Resolution 15-16
Methylene Blue Test 71
Microwave Oven Drying of Soil 53
Minimum Average Roll Value 207
MQA/CQA Certifying Engineer 9
MQA/CQA Engineer 7-8
MQA/CQA Personnel 8
MQA/CQA Plan 11
Nuclear Moisture-Density Tests 54-55,58-60
Owner's Representative 5
Owner/Operator 3
Penetrations 264-266
Percent Compaction 27
Permitting Agency 3
Personnel Qualifications 10
Pick Test 162, 163
Piggybacking 270
Pipe Boot 264
Pipe Penetrations 265
Pipe- see Geopipe
Plastic Concrete 250-251
Plastic Pipe- see Geopipe
Polyvinyl Chloride 106-107, 124-129
254-256
Additives 107
Blocking 124
Calendering 124,126-127
Filler 107
Polyvinyl Chloride (continued)
Manufacturing 124-129
Panel Fabrication 127-129
Pipe 254-256
Plasticizer 106-107
Resin 106
Prayer Seam 214,215, 216
Prefabricated Bentonite Clay Blankets 174
Pressurized Dual Seam 162, 163,166
Pugmill Mixing of Bentonite 70-71
Records- Storage 14
Reinforcement Materials 270-274
Reports 11-13
Corrective Measures 13 '
Daily Inspection 11
Daily Summary 11-12
Inspection 12-13
Problem Identification 13
Testing 12-13
Risers 261-264
Rubber Balloon Density Test 57-58
Sample Custody 17
Sand Cone 56-57
Sealed Double Ring Infiltrometer 91-93
Sheet Drains 226,227
Sheet Pile Walls 237-238
Slurry Trench Cutoff Walls 239-250
Slurry Trench- see Vertical Cutoff Walls
Slurry Wall- see Vertical Cutoff Walls
Static Compaction 46-47
Stinger 181, 212, 222
Strip Drains 226, 227
Sumps 261-264
Test Pads 34-35, 88-95
Testing Laboratory 9
Two Stage Borehole Test 93-94
Ultrasonic Impedance Plane 163,164-165,
166
Ultrasonic Methods 163, 164-165, 166
Ultrasonic Pulse Echo 163,164, 166
Ultrasonic Shadow Method 163,165,166
Vacuum Chamber (Box) 163,164,166
Veneer Reinforcement 270
Venturi Mixer 242
Vertical Cutoff Walls 235-252
Caps 251
Cement-Bentonite Cutoff Walls
248-250
Construction 241-251
CQA Requirements 251-252
Examples 235-236
Excavation of Slurry Trench 243-244
Geomembrane in Slurry Trench Cutoff
Walls 250
Mobilization 241
Site Preparation 241
304
-------
Vertical Cutoff Walls (continued)
Slurry Density 242-243
Slurry Preparation and Properties
241-243
Slurry Viscosity 243
Soil-Bentonite Backfill 244-248 "
Types 237-241
Very Low Density Polyethylene 103-105,
120-123
Additives 105
Blown Film 121
Carbon Black 104-105
Coextrusion 122
Flat Horizontal Die 120-121
Impingement 122
Lamination 122
Regrind Chips 104
Resin 103-104
Rework Chips 104
Vibratory Compaction 46-47
Water Content Measurement for Soil 53-55
Weather 17
Wick Drains 226,227
Work Stoppages 17-18
305
•U.S GOVERNMENTPWWT1NGOFFICE 1993 .750 .002/80296
-------
-------
Available Companion Document of Standards
To
Quality Control and Quality Assurance for Waste Containment Facilities,
EPA/600/R-93/182
A compilation of standards referenced in this document (Quality Control and Quality Assurance for
Waste Containment Facilities, EPA/600/R-93/182) is available from The American Society for Testing
and Materials (ASTM). It is intended as a companion for this document and.for engineers and
researchers who are involved with quality assurance and quality control practices concerning all
components of waste containment.
The ASTM document is entitled ASTM and other Specifications and Test Methods on the Quality
Assurance of Landfill Liner Systems, and is identified by the following numbers:
Publication Code Number (PCN): 03-435193-38
International Standard Book Number (ISBN): 0-8031-1784-1
It contains 79 ASTM standards and 10 non-ASTM references that are cited in the EPA guidance
document, consists of approximately 500 pages, and has a soft cover. The first printing in late 1993 is
available at the following prices:
ASTM-member price: $69.00, non-member price: $77.00
Quantity discounts of the same publication are available.
ASTM Document Ordering Instructions:
Contact:
ASTM Publications Telephone: (215)299-5585
1916 Race Street Facsimile: (215)977-9679
Philadelphia, Pennsylvania, 19103
USA
1) List each publication by quantity, Publication Code Number (PCN as listed above), title and
price.
2) Add any additional handling charges to subtotal of order:
USA and Canada All other countries
Prepaid No charge 10% ($1.50 minimum)
Bill/Ship 7% ($1.50 minimum) 15% ($1.50 minimum)
3) Residents of Canada, and Pennsylvania and Maryland in the USA, please add applicable sales
tax to your order.
4) Unless indicated otherwise, all orders will be shipped fourth class.
Please note: This companion document is offered by ASTM entirely independent of U.S. EPA, hence
no credit for its development or responsibility can be assumed for the use of its contents. This page
is for information only and does not constitute endorsement.
Prices are subject to change without notice.
R2070, October, 1993
-------
------- |