<>EPA     Industrial Waste Air Model
          Technical Background
          Document
United States
Environmental Protection
Agency

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Solid Waste and                     EPA 530-R-02-010
Emergency Response                August 2002
(5306W)                           www.epa.gov/industrialwaste

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                             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

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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

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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

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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

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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

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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

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IWAIR Technical Background Document                                      Table of Contents

                       Acronyms and Abbreviations (continued)
URF         Unit risk factor
WHO        World Health Organization
WMU       Waste management unit
Vlll

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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

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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.
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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

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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

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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.

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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

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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.

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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

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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.

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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IWAIR Technical Background Document
Section 2.0
                         Table 2-2. Input Parameters for Landfills
Input Parameter
Units
Default
Value
Range"
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

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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

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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

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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

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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

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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
nrYs
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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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).

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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/•«*-"	-	
.f'^W
4dT
                                                                                i   *wi»
                                                                               *'   * ,f

                                                                            Jwfeti   «F
 Figure 3-2. Meteorological stations and region boundaries for the contiguous 48 states.

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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

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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

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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.

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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

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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.

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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

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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, 1997a; 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-Nitrosodi-w-butylamine
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

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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

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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 (m3/d)
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 m3/d.
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

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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

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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

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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

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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

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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

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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

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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

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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

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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 IWAIR
TJRF URF CSFi
dig/mS)1 Ref (mg/kg-d)1
2.2E-06 I 7.7E-03



1.3E-03 I 4.6E+00

6.8E-05 I 2.4E-01
6.0E-06 C99a 2.1E-02
1.6E-06 C99a 5.6E-03
7.8E-06 I 2.7E-02
6.7E-02 I 2.3E+02
1.1E-03 C99a 3.9E+00
1.8E-05 AC 6.2E-02
2.8E-04 I 9.8E-01

1.5E-05 I 5.3E-02

2.4E-05 AC 8.4E-02






6.9E-07 H 2.4E-03

2.6E-05 I 9.1E-02
5.0E-05 I 1.8E-01

CSFi
Ref
calc



calc

calc
calc
calc
calc
I
calc
AC
calc

calc

AC






calc

calc
calc
(continued)
5-6

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IWAIR Technical Background Document
Section 5.0
Table 5-1. (continued)
Name
Dichloropropane, 1,2-
Dichloropropylene, cis-1,3-
Dichloropropylene, trans- 1,3-
Dimethylbenz [a] anthracene, 7,12-
Dimethylphenol, 3,4-
Dinitrotoluene, 2,4-
Dioxane, 1,4-
Diphenylhydrazine, 1 ,2-
Epichlorohydrin
Epoxybutane, 1,2-
Ethoxyethanol acetate, 2-
Ethoxyethanol, 2-
Ethylbenzene
Ethylene dibromide
Ethylene glycol
Ethylene oxide
Formaldehyde
Furfural
Hexachloro- 1 ,3-butadiene
Hexachlorobenzene
Hexachlorocyclopentadiene
Hexachloroethane
Isophorone
Mercury (elemental)
Methanol
Methoxyethanol acetate, 2-
Methoxyethanol, 2-
CAS
No.
78-87-5
10061-01-5
10061-02-6
57-97-6
95-65-8
121-14-2
123-91-1
122-66-7
106-89-8
106-88-7
111-15-9
110-80-5
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
110-49-6
109-86-4
RfC
(mg/m3)
4.0E-03
2.0E-02
2.0E-02



3.0E+00

l.OE-03
2.0E-02
3.0E-01
2.0E-01
l.OE+00
2.0E-04
4.0E-01
3.0E-02
9.8E-03
5.0E-02


2.0E-04

2.0E+00
3.0E-04
4.0E+00
9.0E-02
2.0E-02
RfC
Ref
I
SUIT
SUIT



COO

I
I
COO
I
I
H
COO
COO
A
H


I

C99b
I
COO
coo
I
RfC Target Organ
or Critical Effect
Respiratory
Respiratory
Respiratory



Liver, kidney,
hematological

Respiratory
Respiratory
Developmental
Hematological,
reproductive
Developmental
Reproductive
Respiratory,
kidney,
developmental
Neurological
Respiratory
Respiratory


Respiratory

Developmental,
kidney, liver
Neurotoxicity
Developmental
Reproductive
Reproductive
TJRF URF CSFi CSFi
(Hg/mS)1 Ref (mg/kg-d)1 Ref

4.0E-06 SUIT 1.4E-02 calc
4.0E-06 SUIT 1.4E-02 calc
7.1E-02 C99a 2.5E+02 calc

8.9E-05 C99a 3.1E-01 calc
7.7E-06 C99a 2.7E-02 calc
2.2E-04 I 7.7E-01 calc
1.2E-06 I 4.2E-03 calc



1.1E-06 SF 3.9E-03 calc
2.2E-04 I 7.7E-01 calc

l.OE-04 H 3.5E-01 calc
1.3E-05 I 4.6E-02 calc

2.2E-05 I 7.7E-02 calc
4.6E-04 I 1.6E+00 calc

4.0E-06 I 1.4E-02 calc





                                                                                 (continued)
                                                                                        5-7

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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


TJRF URF CSFi CSFi
(Hg/mS)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)
5-8

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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

TJRF
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
 Trichloro fluoromethane
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   =  CaEPA cancer potency factor (CalEPA, 1999a)
   C99b   =  CaEPA chronic RELs (CaEPA, 1999b)
   COO    =  CaEPA chronic RELs (CaEPA, 2000)
   I       =  IRIS (U.S. EPA, 2001a)
   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

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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).

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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

InhURF
(^g/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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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             Appendix A




Considering Risks from Indirect Pathways

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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

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IWAIR Technical Background Document
                              Appendix A
                        Dispersion     (.
                         ——^ /7'   Vap°rs

                               •'•&* 4-
                                  "$ ^ Fruit and
                           t -^r>JK\f ^3'.,''  Vegetable
                           ^^%frv (ngestion
A
-%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

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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

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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

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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

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IWAIR Technical Background Document
                                                 Appendix A
                Table A-l. Oral Health Benchmarks for IWAIR Chemicals
 IWAIR Constituent Name
            RfD     RfD  CSFo (per  CSFo
CASRN    (mg/kg-d) Source  mg/kg-d)  Source Comment
1,1, 1 ,2-Tetrachloroethane
1,1,1 -Trichloroethane
1 , 1 ,2,2-Tetrachloroethane
1 , 1 ,2-Trichloro-l ,2,2-trifluoroethane
1 , 1 ,2-Trichloroethane
1 , 1 -Dichloroethylene
1 ,2,4-Trichlorobenzene
1 ,2-Dibromo-3 -chloropropane
630-20-6
71-55-6
79-34-5
76-13-1
79-00-5
75-35-4
120-82-1
96-12-8
3.0E-02
2.8E-01
6.0E-02
3.0E+01
4.0E-03
9.0E-03
l.OE-02

IRIS
SF
SF
IRIS
IRIS
IRIS
IRIS

2.6E-02

2.0E-01

5.7E-02
6.0E-01

1.4E+00
IRIS

IRIS

IRIS
IRIS

HEAST intermediate MRL
 1,2-Dichloroethane
107-06-2
                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
HO-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

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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

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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

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          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

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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

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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

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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

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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

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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-l
g/cm3
sec-l
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-l
g/cm3
g/mol
mg/L
mmHg
sec-l
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-l
g/cm3
mmHg
sec-l
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-l
g/cm3
mg/L
mmHg
sec-l
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-l
g/cm3
mmHg
sec-l
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-l
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

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-------
          Appendix C

Sensitivity Analysis of ISCST3 Air
       Dispersion Model

-------

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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
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-------
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

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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

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IWAIR Technical Background Document
Appendix C
                          -400     -300
                                                                 200     300    400
                                                                              -300







                                                                              -200







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                                                  (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-|           +                       +





















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                             -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(

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                           Figure C-5b.  Polar receptor grid (10 degree).
C-20

-------
IWAIR Technical Background Document
Appendix C
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                                                                                 C-21

-------
IWAIR Technical Background Document
                                                                   Appendix C
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    0           50          100         150
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                 Figure C-6c. Maximum concentrations, Cartesian grid
               (95th percentile area, land application unit, Los Angeles, CA).
10
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0 50 100 150 200
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                 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
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                 Figure C-6f.  Maximum concentrations, Cartesian grid
               (95th percentile area, land application unit, Little Rock, AR).
                                                                                 C-23

-------
IWAIR Technical Background Document
Appendix C
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™™™™™™™m™s' 1 u Intel \ ai






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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 -,

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                   Figure C-7b. Maximum concentrations, polar grid
              (50th percentile area, land application unit, Los Angeles, CA).
C-24

-------
IWAIR Technical Background Document
      Appendix C

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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).
      ^ 0.3
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             0       2000     4000    6000     8000     10000
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                   Figure C-7d.  Maximum concentrations, polar grid
               (5th percentile area, land application unit, Little Rock, AR).
                                                                                C-25

-------
IWAIR Technical Background Document
                                                                      Appendix C
                                                                   •22.5 "Interval

                                                                   •10° Interval
             0      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
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                                                                   •22.5 "Interval

                                                                   -10° Interval
           0       2000     4000     6000     8000

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                                                     10000
                   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

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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

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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

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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

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                                                                                                             b

-------
IWAIR Technical Background Document
Appendix D
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Figure D-4. Meteorological stations and region boundaries for the southeastern United States with TRI facilities.
                                                                                                                       b

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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

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                                        100 0 100 200 300 380 Kilometei
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
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CZHCOLORADO PLATEAUS      j	1 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
 f	] Urban
    Cropland and Pasture
    Grassland and Shrubland
    Forest
    Water Bodies
    Wetland
    B a rr e n
    Tundra
 ^EEj Snova or Ice
 BBJ N 0 D 3t3
                                         200    0   200  400   600  Kilometers
                                                                                                                                    £5
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Figure D-8. Meteorological stations and region boundaries for the continental United States with land
              cover (USGS, 1999).
                                                                                                                                    1

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                                                    27502
                                                                      27401
                                                                   v*-x^.
                                                                                      Legend
                                                                                       *  NOT SELECTED
                                                                                     •HHHHW BOUNDARY

                                                                                          Mods rats [$ H i gh R u gge d Mtre
                                                                                     |    | Oeneral^FIat
                                                                                     |    J Plateaus and Highlands of Rolling Topography
                                                                                          Lc«y Mourftairs &enera%' Rolling
                                                                                     [^^J Extreme^High Rugged Mtns
Figure D-9.  Meteorological stations and region boundaries for Alaska with physiography (Wahrhaftig, 1965).

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                                                                                                                     £5
                                                                                                                     r
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                                                                                                                     •
       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
                                                      Lanai

                           0  25  50     100     150    200
                            • • •       ^^^m        ' r
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I
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Figure D-10. Meteorological stations for Hawaii with physiography (State of Hawaii, 1997).
                                                                                                                     1

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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              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
Binb
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
Binb
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
Binb
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

-------