&EPA
United States
Environmental Protection
Agency
EPA-600/R-05/123a
September 2005
GUIDANCE FOR
EVALUATING LANDFILL
GAS EMISSIONS
FROM CLOSED OR
ABANDONED FACILITIES
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EPA-600/R-05/123a
September 2005
GUIDANCE FOR EVALUATING
LANDFILL GAS EMISSIONS FROM
CLOSED OR ABANDONED FACILITIES
by
Thomas Robertson and Josh Dunbar
Environmental Quality Management, Inc.
Cedar Terrace Office Park, Suite 250
3325 Durham-Chapel Hill Boulevard
Durham, North Carolina 27707-2646
EPA Contract No. 68-C-00-186, Task Order 3
EPA Project Officer: Susan A. Thorneloe
U.S. Environmental Protection Agency
Office of Research and Development
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
Research Triangle Park, North Carolina 27711
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
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Abstract
This document provides guidance to superfund remedial project managers, on-scene
coordinators, facility owners, and potentially responsible parties for conducting an air pathway
analysis for landfill gas emissions under the Comprehensive Environmental Response,
Compensation, and Liability Act, Superfund Amendments and Reauthorization Act, and the
Resource Conservation and Recovery Act. The document provides procedures and a set of tools
for evaluating LFG emissions to ambient air, subsurface vapor migration due to landfill gas
pressure gradients, and subsurface vapor intrusion into buildings. The air pathway analysis is
used to evaluate the inhalation risks to offsite receptors as well as the hazards of both onsite and
offsite methane explosions and landfill fires.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting
the Nation's land, air, and water resources. Under a mandate of national environmental laws,
the Agency strives to formulate and implement actions leading to a compatible balance
between human activities and the ability of natural systems to support and nurture life. To meet
this mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage
our ecological resources wisely, understand how pollutants affect our health, and prevent or
reduce environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing risks
from pollution that threaten human health and the environment. The focus of the Laboratory's
research program is on methods and their cost-effectiveness for prevention and control of
pollution to air, land, water, and subsurface resources; protection of water quality in public
water systems; remediation of contaminated sites, sediments and ground water; prevention
and control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with
both public and private sector partners to foster technologies that reduce the cost of
compliance and to anticipate emerging problems. NRMRL's research provides solutions to
environmental problems by: developing and promoting technologies that protect and improve
the environment; advancing scientific and engineering information to support regulatory and
policy decisions; and providing the technical support and information transfer to ensure
implementation of environmental regulations and strategies at the national, state, and
community levels.
This publication has been produced as part of the Laboratory's strategic long-term research
plan. It is published and made available by EPA's Office of Research and Development to
assist the user community and to link researchers with their clients.
Sally Gutierrez, Director
National Risk Management Research Laboratory
in
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EPA Review Notice
This report has been peer and administratively reviewed by the U. S. Environmental Protection
Agency and approved for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Information Service,
Springfield, Virginia 22161.
Disclaimer
This guidance is intended solely for informational purposes. It cannot be relied upon to
create any rights enforceable by any party in litigation with the United States. This guidance
is directed to EPA personnel; it is not a final action, and it does not constitute rule making. EPA
officials may decide to follow the guidance provided herein, or they may act at variance with
the guidance, based on site-specific circumstances. The guidance may be reviewed and/or
changed at any time without public notice.
IV
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Table of Contents
Section Page
Abstract ii
Foreword iii
Notice iv
Disclaimer iv
List of Figures vii
List of Tables ix
List of Acronyms x
Acknowledgment xiii
Executive Summary ES-1
1. Introduction 1-1
1.1 What is Landfill Gas? 1-3
1.2 What are the Routes of Human Exposure? 1-4
1.3 Human Health and Safety Concerns 1-5
1.4 ARARs Specific to Landfill Gas Emissions 1-7
1.5 Potential Landfill Problem Areas 1-9
1.6 Document Organization 1-10
2. Landfill Gas Generation and Transport 2-1
2.1 Landfill Gas Generation 2-1
2.2 Estimation of Ambient Air Impacts 2-5
3. Assessing Subsurface Vapor Migration 3-1
3.1 Screening-Level Vapor Migration Modeling 3-3
3.2 Determining the Extent of Methane Migration 3-7
3.3 Mitigation Strategies for Subsurface Vapor Migration 3-10
3.4 Indoor Vapor Intrusion from Contaminated Groundwater 3-15
4. Air Pathway ARARs 4-1
4.1 Clean Air Act ARARs 4-2
4.2 RCRA Subtitle C Air Pathway ARARs 4-8
4.3 RCRA Subtitle D Air Pathway ARARs 4-10
4.4 State Air Pathway ARARs 4-10
5. Landfill Gas Collection and Control Systems 5-1
5.1 Landfill Gas Collection Systems 5-1
5.2 Evaluating Existing Gas Collection Systems 5-8
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Table of Contents (concluded)
Section Page
5.3 Landfill Gas Control Systems 5-11
5.4 Carbon Adsorption Systems 5-13
5.5 Stack Sampling 5-16
6. Illustrative Case Studies 6-1
6.1 Summary of the Somersworth Sanitary landfill Superfund Site 6-2
6.2 Summary of the Rose Hill Regional landfill Superfund Site 6-10
6.3 Summary of the Bush Valley Landfill Superfund Site 6-24
7. References 7-1
Appendices
A. Monitoring Landfill Gas Chemicals of Potential Concern A-l
B. Wilcoxon Statistical Procedures B-l
C. Generic Quality Assurance Project Plan EPA-600/R-05/123b
VI
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List of Figures
Number Page
ES-1 Simplified Data Gathering and Decision-Making Flow Chart ES-2
2-1 Landfill Gas Evolution 2-2
2-2 Flow Chart for Assessing Air Impacts by Modeling 2-7
2-3 Sample Output from the LandGEM Model 2-13
2-4 Example COPC Emission Estimates Produced by LandGEM 2-14
2-5 Example of Multi-Parcel Area Emission Source 2-18
2-6 Example of SCREENS Model Output File 2-20
3-1 Flow Chart for Assessing Subsurface Vapor Migration by Convection 3-2
3-2 U.S. Soil Conservation Service Classification Chart Showing Centroid
Compositions (Solid Circles) 3-5
3-3 Example of a Multi-Depth Cluster Well 3-6
3-4 Flammability of Methane/Oxygen Mixtures 3-11
3-5 Abandoned Horizontal Barrier Trench System 3-13
3-6 Alternative Migration Barrier System 3-13
3-7 Flow Chart for Assessing Vapor Intrusion from Contaminated Groundwater .. 3-15
3-8 Indoor Vapor Intrusion from Groundwater 3-16
4-1 NSPS Landfill Applicability 4-3
4-2 Flow Chart for Determining Control Requirements 4-5
4-3 Flow Chart of Surface Monitoring Requirements 4-7
5-1 Gas Extraction Well Head Assembly 5-3
5-2 Vertical Trench for Active Collection System 5-4
5-3 Horizontal Trench Collection System 5-4
5-4 Zones of Influence for Gas Extraction Wells 5-6
5-5 Typical Gas Control System 5-7
5-6 Skid-Mounted Open Flare and Blower Station 5-12
5-7 Enclosed Ground Flare and Blower Station 5-12
5-8 Small Skid-Mounted Enclosed Ground Flare 5-13
6-1 Somersworth Sampling Grid 6-4
6-2 Somersworth - Example LandGem Model Run Output 6-6
6-3 Somersworth NMOC Emission Rates versus Time 6-7
6-4 Rose Hill - Screening Sampling Grid Locations 6-12
6-5 Rose Hill - Measured Screening Results for NMOC (ppm) 6-15
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List of Figures (concluded)
Number Page
6-6 Rose Hill - Measured Screening Results for Methane (ppm) 6-15
6-7 Rose Hill - NMOC Concentration (ppmv) Isopleths from Summa Sampling .. 6-18
6-8 Rose Hill - Example LandGEM Model Run Output 6-20
6-9 Rose Hill - NMOC Emission Rates versus Time 6-21
6-10 Rose Hill - Defined Modeling Areas for SCREENS 6-22
6-11 Bush Valley - Screening Sampling Grid 6-27
6-12 Bush Valley - Measured Screening Results for NMOC (ppm) 6-30
6-13 Bush Valley - Measured Screening Results for Methane (ppm) 6-30
6-14 Bush Valley - NMOC Concentration Isopleths (ppmvC) from Summa
Sampling 6-33
6-15 Bush Valley - 1,1-Dichloroethene Concentration Isopleths (ppmv) from Summa
Sampling 6-33
6-16 Bush Valley - Example LandGEM Model Run Output 6-36
6-17 Bush Valley - NMOC Emission Rates versus Time 6-37
6-18 Bush Valley - Defined Modeling Areas for SCREENS 6-38
Vlll
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List of Tables
Number Page
1-1 Idealized Procedures and Methodologies for Evaluating the Significance
of Landfill Gas Emissions 1-1
1-2 Typical Landfill Gases, Their Percent by Volume, and Their Characteristics ... 1-4
1-3 COPCs Commonly Found in LFG 1-5
2-1 Default Concentrations for Landfill Gas COPCs 2-12
2-2 Example of SCREENS Results for Multi-Parcel Emission Source 2-19
2-3 Averaging Time Conversion Factors 2-19
3-1 Class Average Values of Soil Saturated Hydraulic Conductivity 3-4
5-1 Typical Cover Permeability and Thicknesses 5-9
5-2 Stack Sampling Methods for LFG Combustion Equipment 5-16
6-1 Comparison of the Case Studies 6-1
6-2 Somersworth COPCs that were Quantified 6-5
6-3 Somersworth - Emission Rates for COPCs 6-7
6-4 Somersworth - Maximum Annual Concentrations of COPCs 6-8
6-5 Somersworth Risk Analysis 6-9
6-6 Somersworth - Comparison of CH4 Concentrations by Study Method 6-9
6-7 Rose Hill Screening Sample Results (partial) 6-14
6-8 Rose Hill - 90th Percentile Concentrations for Individual COPCs
from the Northern and Southern Homogeneous Parcels 6-18
6-9 Rose Hill - Analytical Results for Individual COPCs 6-19
6-10 Rose Hill - Emission Rates of COPCs by Homogeneous Parcel 6-21
6-11 Rose Hill - Maximum Annual Concentrations 6-23
6-12 Rose Hill - Risk Assessment Analysis 6-24
6-13 Bush Valley Screening Sample Results (partial) 6-28
6-14 Bush Valley - Analytical Results for Individual COPCs 6-34
6-15 Bush Valley - 90th Percentile Concentrations of Individual COPCs 6-35
6-16 Bush Valley - Emission Rates for COPCs by Homogeneous Parcel 6-37
6-17 Bush Valley - Maximum Predicted Ambient Air Annual Concentrations 6-39
6-18 Bush Valley - Risk Assessment Analysis 6-40
IX
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List of Acronyms
Acronym Definition
ARAR applicable or relevant and appropriate requirement
ASTM American Society of Testing and Materials
BDT best demonstrated technology
CAA Clean Air Act
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulations
CH4 methane
CO carbon monoxide
CO2 carbon dioxide
COPCs contaminants of potential concern
DCA dichloroethane
DQO data quality objectives
DRE destruction removal efficiency
ED exposure duration
EG Emission Guidelines
EPA U.S. Environmental Protection Agency
ERTC Environmental Response Team Center
FID flame ionization detector
FML flexible membrane liner
GC/MS gas chromograph/mass spectrometer
GMPs gas monitoring probes
GPS Global Positioning System
H2 hydrogen
HAP hazardous air pollutant
HC1 hydrogen chloride
FIDPE high-density polyethylene
FEAST health effects assessment summary tables
Hg mercury
HI hazard index
HRPM horizontal radial plume mapping
HSWA Hazardous and Solid Waste Act
ICE internal combustion engine
IRIS Integrated Risk Information System
ISC3 Industrial Source Complex, Version 3
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List of Acronyms (continued)
Acronym Definition
ISCLT3 Industrial Source Complex Long Term, Version 3
LandGEM landfill gas emission model
LBL Lawrence Berkeley National Laboratory
LCS laboratory control samples
LEL lower explosive limit
LFG landfill gas
LMOP Landfill Methane Outreach Program
LNAPL light nonaqueous phase liquids
MACT maximum achievable control technology
MDL method detection limit
MS matrix spike
MSD matric spike duplicate
MEK methyl ethyl ketone
MSW municipal solid waste
MSWLFs municipal solid waste landfills
N2 nitrogen
NAPL nonacqueous phase liquids
NCEA National Center for Environmental Assessment
NCP national contingency plan
NESHAP National Emission Standards for Hazardous Air Pollutants
NMOC nonmethane organic compounds
NRCS Natural Resources Conservation Service
NRMRL National Risk Management Research Laboratory
NSCEP National Service Center for Environmental Publications
NSPS New Source Performance Standard
O2 oxygen
OP-FTIR open path fourier transform infrared
OPMs open path monitors
OPS optical remote sensing
OP-TDLAS open-path tunable diode laser absorption spectroscopy
ORS optical remote sensors
OSC on scene coordinator
OSHA Occupational Safety and health Administration
PC personal computer
PCB polychlorinated byphenyl
PID photoionization detector
ppb parts per billion
ppmv parts per million by volume
POTW publically owned treatment works
PRP potential responsible party
PVC polyvinyl chloride
QAPP Quality Assurance Project Plan
XI
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List of Acronyms (concluded)
Acronym Definition
QA/QC quality assurance/quality control
RCRA Resource Conservation and Recovery Act
RfCs reference concentrations
ROD record of decision
RPD relative percent difference
RPM remedial project managers
SARA Superfund Amendments and Reauthorization Act
SCDM superfund chemical data matrix
SCRAM Support Center for Regulatory Air Models
SCS Soil Conservation Service
SFL superfund landfill
SO2 sulfur dioxide
SOPs standard operating procedures
SSL soil screening levels
SSM start-up shutdown malfunction
STAR stability array
SVOCs semi-volatile organic compounds
TEA to be assigned
TCLP toxicity characteristic leaching procedure
TMPs temporary gas monitoring probes
TSDF treatment storage and disposal facilities
UEL upper explosive limit
UV-DOAS ultraviolet differential optical absorption spectroscopy
VOC volatile organic compounds
VRPM vertical radial plume mapping
xn
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ACKNOWLEDGMENT
Acknowledgment is given to the following individuals for their review and thoughtful
suggestions to support the preparation of the Fact Sheet and the Guidance for Evaluating
Landfill Gas Emissions from Closed or Abandoned Facilities:
Susan A. Thorneloe, Project Officer, U.S. EPA Office of Research and Development
External Peer Reviewers
Ram Hashmonay, ARCADIS
David Healy, Maryland Department of Environmental Management
Gary Joblonski, Rhode Island Department of Environmental Management
Mark Modrak, ARCADIS
Dan Pazdersky, Harford County, Maryland Engineering and Utilities Department
Additional Contributors and Reviewers
Eric Adidas, U.S. EPA/Region 6
Foston Curtis, U.S. EPA/OAQPS
Ed Hathaway, U.S. EPA/Region 1
Dave Kirchgessner, U.S. EPA/APPCD
Fred MacMillian, U.S. EPA/Region 3
Ron Mosley, U.S. EPA/ORD
William J. Rhodes, U.S. EPA/ORD
Ken Skahn, U.S. EPA/OSWER
Bob Wright, U.S. EPA/ORD
Robin Anderson, U.S. EPA/OSRTI
Roger Duwart, U.S. EPA/Region 1
K. C. Hustvedt, U.S. EPA/OAQPS
Rebecca Kurowski, U.S. EPA/Region 1
Dave Mickunas, U.S. EPA/ERTC
Dave Newton, U.S. EPA/Region 1
Richard Shores, U.S. EPA/ORD
Jim Topsale, U.S. EPA/Region 3
A special acknowledgment is given to Craig Mann, who was instrumental in advancing the
state of the art dealing with air pathway analysis and soil vapor intrusion. Craig was the original
project manager for the original guidance document. He worked tirelessly and with much
dedication until his untimely death in August 2001 due to a cerebral hemorrhage. Craig devoted
his entire career to the advancement and dissemination of environmental science as an intel-
lectually challenging and broadly relevant discipline. He had an innate ability to cut through
the chaff and convince others that their common ground is more important than their
differences. This guidance document is dedicated to his memory and honor. His contributions
to the environmental field will truly be missed.
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Guidance for Evaluating Landfill Gas
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Emissions from Closed or Abandoned Facilities
EXECUTIVE SUMMARY
Asphyxiation and explosion are the two most commonly recognized health risks associated
with landfill gas (LFG). In addition, there is concern for acute toxicity, chronic hazards, and
risks associated with LFG emissions. LFG is the natural by-product of the anaerobic
decomposition of biodegradable waste in landfills. LFG is a complex mixture of gases,
including methane, carbon dioxide, and trace constituents of volatile organic compounds
(VOC), hazardous air pollutants (HAPs), and hydrogen sulfide. Landfill gas can also contain
persistent bioaccumulative toxic compounds such as mercury. Municipal solid waste (MSW)
landfills are one of the largest sources of anthropogenic methane emissions. Regulations under
the Clean Air Act have targeted large municipal landfills through performance based regulations
for controlling LFG emissions. This guidance addresses the LFG hazards by providing
interested stakeholders and decision makers with information that can be used to evaluate and
mitigate potential landfill gas emissions to ensure protection of human health and the
environment.
The movement of LFG in unsaturated MSW may occur through various mechanisms,
including diffusion, convection, pressure gradient flow, and water-vapor transport. The
characteristics of LFG (generally warmer though slightly more dense than soil air at equivalent
temperatures) also impact the mechanics of the gas transport, as do the molecular weights and
specific gravities of the VOCs in the LFG. Given the varying solubilities, vapor pressures,
molecular weights, and specific gravities of the typical components of LFG, specific transport
mechanisms will affect the migration of the respective components. Thus, migration occurs as
movement of individual gaseous components and an integral excursion front. Through
advective flow, LFG pressure gradients can influence the direction and rate of both LFG
excursion fronts and VOC migration paths. LFG will migrate (encouraged by the natural
development of positive pressures within the landfill) toward the surface and edges of the fill
and into the adjoining soils.
LFG migrates from the subsurface to the atmosphere via diffusion and advection
mechanisms through the soil pores, fractures, gaps and defects in the cover materials, or it is
collected and discharged via vents systems that may or may not be controlled. LFG migrates
underground via natural and manmade pathways. Natural pathways include fracture zones
normally associated with karst topography, significant cavernous structures, dry pockets or
strata of sand and gravel, and soil strata interfaces. Migrating LFG does not generally travel at
a depth lower than the current groundwater table unless a manmade structure is provided. These
structures include the trenches associated with all types of buried utilities (sanitary sewers,
ES-1
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Guidance for Evaluating Landfill Gas
storm sewers, electrical service lines, cable TV lines, telephone lines, and water mains). Usually
the granular or aggregate bedding for these buried utilities is sufficiently porous to allow easy
migration of LFG along the trench line. Ultimately the LFG will travel from the area of highest
pressure via the path of least resistance, until the pressure and concentration gradient reach
equilibrium with the surrounding environment.
When LFG accumulates in a trench, excavation, or other enclosed space, an extremely
dangerous situation is present. Gas infrared analyzers ("sniffers") are used to make sure that the
air in the enclosed space is safe to breathe, and they are used to measure gas accumulations in
monitoring probes. Gas can also accumulate in the foundations, basements, and closed rooms
of nearby buildings. Such places can accumulate LFG until it exceeds the lower explosive limit
(LEL). LFG migrating through soil at shallow depths tends to kill root systems, resulting in
visible vegetative stress along the path of migration. Such dead or dying vegetation is typically
a clear indication of migrating gas, and monitoring probes are usually installed in these areas
to directly measure the amount of escaping LFG.
Emission estimating is an important step in conducting risk evaluations, obtaining permits,
demonstrating compliance with regulatory limits, and designing emission control systems for
solid waste landfills. There are several methods for measuring and analyzing LFG. This
document presents a step-wise procedure using readily available field instruments, sampling
probes placed just below the cover, routine analytical methods, and commonly used fate and
transport modeling procedures. The document also presents the results of an example
application of an open path Fourier transform infrared spectroscopy (OP-FTIR) emission
measurement method. The OP-FTIR was used in conjunction with a radial plume mapping
technique in order to estimate the emission rates and establish ambient air concentrations.
Figure 1 presents a flow chart that illustrates the information gathering and decision-making
process described in the guidance.
Figure ES-1. Simplified Data Gathering and Decision-Making Flow Chart for the Guidance
for Evaluating Landfill Gas Emissions from Closed or Abandoned Facilities.
ES-2
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Emissions from Closed or Abandoned Facilities
This document presents site investigators, risk managers, and design engineers with procedures
and methodologies that may be used to estimate LFG emissions and their resulting ambient air
concentrations. The usefulness of this document was demonstrated at three study sites that are
illustrative of the techniques discussed herein. It is recognized that each technique has advan-
tages and disadvantages that must be taken into account. Decision makers must balance their
need for definitive site-specific information with that derived by generic fate and transport
models. The field screening, sampling, and modeling procedures were used atthree sites—Rose
Hill Regional Landfill in South Kingston, Rhode Island; Bush Valley Landfill in Abingdon,
Maryland; and the Municipal Landfill Superfund Site located in Somersworth, New Hampshire.
At the third site, ground-based optical remote sensing was used in addition to serpentine pattern
sampling.
ES-3
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Guidance for Evaluating Landfill Gas
ES-4
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Emissions from Closed or Abandoned Facilities
1. Introduction
The purpose of this guidance document is to provide the remedial project manager (RPM),
the on-scene coordinator (OSC), and potentially responsible parties (PRPs) with a set of pro-
cedures and tools for evaluating the health and safety impacts of landfill gas (LFG) emissions
from closed or abandoned co-disposal landfills under the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA); the Superfund Amendments and
Reauthorization Act (SARA); and the Resource Conservation of Recovery Act (RCRA). The
procedures and methodologies described in this document are summarized in Table 1-1.
Table 1-1. Idealized Procedures and Methodologies for Evaluating the Significance of Landfill
Gas Emissions
Procedure Methodology
1 Collect historic data to assist in planning sampling and analysis activities.
2 Develop quality assurance project plan. Identify applicable or relevant and appropriate
requirements (ARARs) and determine regulatory requirements. Establish target analyte
(chemical of potential concern) list. Select analytical methods to be used. Determine if
off site sampling and analysis needs to be included in the effort.
3 Develop a sample grid to cover the landfill and adjacent areas of concern. Grid size
varies according to homogeneity of landfill contents and economics associated with
collecting and analyzing LFG. Offsite sampling may be needed to determine if LFG is
migrating below the surface or if vapors from contaminated groundwater is migrating
through the soils and potentially entering into buildings.
4 Choose option A or B: (A) Use field instruments to identify hot spots emitting methane
(CH4) and non-methane organic compounds (NMOCs); or (B) Use remote optical
scanning system to identify hot spots and to generate emission rate information and
resulting ambient air concentration data. The choice is largely determined by econom-
ics, time criticaliry, and availability of equipment and expertise.
5 If following option A: Determine the minimum number of areas (parcels) of nearly
homogeneous emissions required to normalize the emissions from the landfill surface.
Non-parametric statistical procedures (e.g., Wilcoxon, Mann-Whitley) and geograph-
ical isopleth plotting software are used to make this determination.
continued
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Guidance for Evaluating Landfill Gas
If following option A: Use rank order statistics to identify hot spot locations (highest
NMOC/CH4 concentration) for each parcel. Collect subsurface LFG samples from each
parcel hot spot. Samples may need to be collected from active and passive vents and
from the landfill surface. Surface sampling is accomplished by making a hole (e.g.,
slam bar, geoprobe) through the landfill cover and by placing an extraction tube into
the hole and by collecting samples (bag or canister) for laboratory analysis. Sample
extraction ports are used to collect samples from the vents. Exercise care not to cause
ambient air to enter the LFG sample. Repair holes and close ports as appropriate.
If following option A: Use landfill emission estimating model (e.g., LandGEM,
LANDFILL) to estimate emission rate for each parcel;
If following option A: Use dispersion and deposition models (e.g., ISC3, Screen,
AERMOD, etc.) to estimate the ambient air concentration at each receptor location of
concern.
Compare the predicted concentrations with the target air concentration to satisfy both
the prescribed risk level and target hazard index.
A co-disposal landfill is defined as a landfill in which both municipal solid waste (MSW)
and hazardous or toxic wastes have been deposited. The MSW fraction is the most significant
quantity both volumetrically and on a weight basis. Municipal landfills constitute approximately
20 percent of all sites on the Superfund National Priorities List. LFG is produced by the
breakdown of household garbage by bacteria and typically consists of 40 to 60 percent carbon
dioxide (CO2), 45 to 60 percent methane (CH4), and trace constituents which include volatile
organic compounds (VOCs), and hazardous air pollutants (HAPs). Landfill gas can also contain
(1) persistent bioaccumulative toxic compounds such as mercury, (2) ammonia, (3) oxygen (O2)
and nitrogen (N2) from air infiltration, (4) carbon monoxide (CO), and (5) hydrogen sulfide
(H2S). Nonmethane organic compounds (NMOCs) include trichloroethylene, benzene, and vinyl
chloride. Usually, gas production begins within a year of waste placement and may continue
for as long as 50 years after landfill closure. Maximum gas production ranges from less than
0.2 to more than 0.5 m3 per kg of solid waste. The actual rate of gas production is a function of
refuse composition, age (or time since emplacement), climate, moisture content, particle size
and compaction, nutrient availability, and buffering capacity. Reported production rates vary
from 0.0007 to 0.0080 m3 per kg-yr. Generally, for any given cell, these production rates peak
during the first or second year following waste placement and decline thereafter. In an active
landfill, because of the sequential nature of the operations, each cell will be in a different stage
of decomposition and will be generating gas at a different rate. As more waste is added,
however, the total gas production rate increases. In general, it is expected that total gas
production will rise rapidly during the operating years, and then fall off after closure.
Numerous investigations have been conducted to characterize LFG emissions, and
significant variation in LFG composition has been observed. More than fifty different
VOCs—including simple alkanes, olefms, aromatics, and a wide array of chlorinated
compounds—have been identified in LFG. These VOCs include a number of known or
suspected carcinogens (such as benzene and vinyl chloride). The VOC concentrations range
from a few parts per billion (ppb) to tens of thousands of ppb. LFG, including CH4, can easily
move though permeable soils like those present at many closed and uncontrolled landfill sites.
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Emissions from Closed or Abandoned Facilities
These gases usually move from areas of high pressure (at depth within the landfill) to areas of
low pressure (surficial soils and atmosphere), but it is often difficult to predict specific patterns
of gas movement. Under certain conditions, LFG can migrate laterally for long distances from
the landfill. An often used rule of thumb is that it may migrate up to 1000 feet, but there are
documented cases where LFG has traveled in the subsurface for more than 2000 feet. Structures
within this distance may require additional evaluations and precautions to protect them from
LFG accumulation. LFG will migrate along all possible pathways, favoring those that present
the path of least resistance. Utility trenches, sanitary and storm sewers, and building footers are
the most common pathways allowing long distance transport. Knowledge of the landfill's,
geometry, design, and operating characteristics as well as the local geology, hydrology, and
land uses is helpful in evaluating and understanding gas migration and emission phenomena.
High concentrations of LFG occur most commonly in landfills that contain municipal
garbage and have an impermeable or nearly impermeable cover. The cover traps these gases,
prevents them from escaping upward, and causes them to move either into a gas collection and
control system or laterally into adjacent, off-site areas. Highest CH4 concentrations occur in the
warmer summer months, and concentrations are higher during the heat of the day compared to
measurements taken during morning hours. LFG levels in soils tend to be higher during dry
periods and lower after significant rainfall events. Associated with high methane production are
increases in CO2 and hydrogen sulfide and decreased amounts of O2.
Human exposure to LFG is not typically addressed during the remedial investigation phase
because containment of the landfill mass and treatment of the LFG is the presumptive remedy,
although this presumptive remedy does not address exposure pathways outside the source area.
Hence, risk assessment and other exposure pathway analyses, as appropriate, may be used to
address offsite migration of LFG. Historically, control of LFG has been performed either to
minimize the potential for LFG explosive hazards or to avoid negatively impacting the selected
cap (i.e., pressures exerted against the cap) rather than an assessment of human exposure during
baseline conditions (undisturbed) and during remediation. Recent consideration of alternative
caps and subsurface natural attenuation may actually increase the potential to release toxic LFG
constituents to the atmosphere. Permeable caps are designed to allow water to infiltrate and to
allow gases to release to the atmosphere. However, this also minimizes gas capture, resulting
in larger fugitive loss of emissions.
1.1 What Is Landfill Gas?
LFG is generated by the decomposition of organic municipal solid wastes such as garbage,
garden wastes, and paper products. This process may continue for 20 to 50 years after initial
dumping of the MSW. At near steady-state conditions, LFG is typically composed of approx-
imately 55 percent CH4, 40 percent CO2, 5 percent N2, and smaller amounts of NMOCs such
as benzene, vinyl chloride, chloroform, 1,1-dichloroethene, carbon tetrachloride, and other
NMOCs. In addition, non-organic species such as hydrogen sulfide and vapor phase mercury
are often found in LFG. Table 1-2 presents volumetric and characteristic information for a
typical LFG.
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Table 1-2. "Typical" Landfill Gases, Their Percent by Volume, and Their Characteristics
Compo-
nent
Percent by
Volume
Characteristic
CO2
N2
02
Ammonia
NMOCs
40 to 60
2 to 5
0.1 to 1
0.1 to 1
0.01 to 0.6
CH4 45 to 60 CH4 is a naturally occurring, colorless, and odorless gas. Its concentra-
tion in ambient air is 0.0002%. Landfills are the single largest source of
U.S. man-made methane emissions.
CO2 is a colorless and slightly acidic gas that occurs naturally at a small
concentration (0.03%) in the atmosphere.
N2 comprises approximately 79% of the atmosphere. It is odorless,
tasteless, and colorless.
O2 comprises approximately 21% of the atmosphere. It is odorless,
tasteless, and colorless.
Ammonia is a colorless gas with a pungent odor. Atmospheric concen-
trations are less than 0.0001%.
NMOCs are organic compounds (i.e., compounds that contain carbon)
excluding methane. NMOCs may occur naturally or be formed by
synthetic chemical processes.
Sulfides 0 to 1 Sulfides (e.g., hydrogen sulfide, dimethylsulfide, mercaptans) are
naturally occurring gases that gives the landfill gas mixture its rotten
egg smell. Sulfides can cause unpleasant odors even at very low con-
centrations. Ambient air concentrations are less than 0.001%.
Hydrogen 0 to 0.2 Hydrogen is an odorless and colorless gas. Atmospheric concentrations
are less than 0.00005%.
CO 0 to 0.2 CO is an odorless and colorless gas. Atmospheric concentrations are
less than 0.00001%.
Co-disposal LFG typically includes higher NMOC vapor concentrations when compared
to an MSW landfill that has not received any significant quantity of toxic or hazardous
compounds.
1.2 What Are the Routes of Human Exposure?
Human exposure to LFG occurs through three primary pathways: (1) release of LFG to
ambient air, (2) subsurface vapor migration by convection and subsequent indoor vapor
infiltration, and (3) indoor vapor infiltration from contaminated groundwater below buildings.
Release of LFG to ambient air is most prevalent when a permeable cover is used or when the
cover has been breached either intentionally or unintentionally. Under such conditions, the
internal pressure transports the gas to the surface or through passive vents to the outside air.
Human exposure may occur onsite and offsite as a function of the actual emission rate and
atmospheric dispersion. The significance of the human exposure is determined by the
chemical's toxicity and concentration as well as by the duration and frequency of exposure.
Duration and frequency of exposure are functions of the LFG emission rate, the atmospheric
dispersion, and human life style.
When an impermeable or nearly impermeable cover exists or when a permeable cover is
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Emissions from Closed or Abandoned Facilities
either overlain by snow or nearly saturated with moisture, horizontal (lateral) subsurface vapor
migration may be the path of least resistance. The rate and extent of lateral vapor migration is
a function of the landfill's internal pressure and the permeability of the surrounding media. LFG
that has migrated laterally from the landfill may be discharged into ambient air and buildings
when the vertical vapor permeability is greater than the horizontal vapor permeability.
If contaminated landfill leachate is allowed to commingle with groundwater and/or if the
LFG contaminant vapor phase concentration is greater than the aqueous solubility, a plume of
contaminated groundwater may be generated that will move though the subsurface in a direction
that is hydraulically down gradient. The groundwater plume may move in a direction that is
different than the LFG plume. The contaminated groundwater will off gas when the
contaminant soil vapor pressure is lower than that found in the groundwater in accordance with
Henry' s law. The released vapor will migrate towards the surface until equilibrium is achieved
or until an atmospheric release occurs.
1.3 Human Health and Safety Concerns
Human health concerns are a function of the exposure to the toxic constituents of LFG. A
list of toxic compounds often found in the LFG of MSW landfills is given in Table 1-3 (U.S.
EPA, 1997a). These toxic compounds should not be considered the only possible toxic
constituents, but the constituents that are typically target analytes during LFG testing or are
considered hazardous air pollutants (HAPs) under the Clean Air Act (CAA) or are monitored
for under a State program. Additional toxic constituents could be present depending on the
disposal history of the landfill—e.g., other industrial organic compounds, herbicides, pesticides,
polychlorinated byphenyls (PCBs), mercury, etc.
Table 1-3. Contaminants of Potential Concern Commonly Found in LFG a
1,1,1 -Trichloroethane (Methyl Chloroform) 1,1,2,2- Tetrachloroethene
1,1-Dichloroethane (ethylidene dichloride) 1,1-Dichloroethene (vinylidene chloride)
1,2-Dichloroethane (ethylene dichloride) 1,2-Dichloropropane (propylene dichloride)
Acetone Acrylonitrile
Benzene Bromodichloromethane
Carbon disulfide Carbon tetrachloride
Chlorobenzene Chloroethane
Chlorofluorocarbons Chloroform
Chloromethane Dichlorobenzene
Dichloromethane (Methylene Chloride) Hexane
Hydrogen sulfide Methyl ethyl ketone
Methyl isobutyl ketone Methyl mercaptans
Tetrachloroethylene (perchloroethylene) Toluene
Trichloroethylene Vinyl chloride
Xylenes
a Constituents associated with carcinogenic and/or chronic noncarcinogenic health effects that are routinely measured;
Source: SWANA 2000.
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Guidance for Evaluating Landfill Gas
Although the source of this information is the U. S. Environmental Protection Agency (EPA)
Compilation of Air Pollutant Emission Factors, AP-42, 5th Edition, Supplement C (AP-42)
section on MSW landfills, the background information for this section contains data from sites
with and without known co-disposal of hazardous wastes. Therefore, although Table 1-3 should
not be considered a complete list of all contaminants of potential concern (COPCs) contained
in LFG, the listed constituents have significant potential to be found at sites where co-disposal
has taken place. If there is historical evidence indicating that other industrial chemicals,
pesticides, herbicides, or other substances have been disposed of at a site, these should be added
to the list of COPCs.
Methane is a flammable, potentially explosive gas that is combustible only under specific
conditions (i.e., the right combination of CH4 and O2 plus a source of ignition). Methane is
explosive at concentrations that range from the lower explosive limit (LEL) of 5 percent to the
upper explosive limit (UEL) of 15 percent CH4 per volume of air. This corresponds to CH4 con-
centrations of 10,000 to 30,000 parts per million by weight (ppmw). There have been at least
30 reported cases of explosions associated with LFG, causing property damage and killing or
injuring nearby residents or workers. At concentrations below the LEL, the CH4/air mixture is
too dilute (CH4 concentrations are too low) to ignite. If a source of ignition is available any
concentration between the LEL and the UEL will allow combustion. Methane concentrations
above the UEL (> 15%/v) are too rich (O2 levels are too low) to support combustion. To sustain
a flame, O2 levels have to be at or above 19 percent.
Landfill fires and the accumulation of explosive levels of CH4 within onsite and offsite
buildings is the primary LFG safety concern. Landfill fires can occur from the excessive influx
of ambient air into the landfill wastes. As ambient air infiltrates the landfill wastes, the CH4
concentration may be locally diluted to levels below the UEL and above the LEL. Typically,
the source of ignition is the establishment of aerobic conditions (composting) in the upper
reaches of the landfill wastes. The aerobic composting can generate enough heat to cause the
CH4 to autogenously ignite. Aerobic conditions are a direct result of ambient air infiltration due
to excessive vacuum applied to LFG extraction wells, landfill cover separations, and natural
diffusion of ambient air through permeable cover materials.
Lateral and subsequent vertical migration of LFG into buildings can also occur. If the
landfill does not incorporate impermeable liners on the sides and bottom, and the wastes are still
generating CH4, subsurface vapor migration can occur beyond the property boundaries. This
may be especially problematic where native soils are relatively permeable (e.g., sands) and offer
little resistance to vapor flow. Favorable conditions for subsurface migration also include an
impermeable surface boundary such as pavement or when surface soils are frozen. Under these
conditions, the horizontal vapor permeability of the soil is greater than the vertical permeability,
and LFG may migrate a considerable distance and at different depths until the gas reaches
equilibrium or until it discharges to the atmosphere. As with landfill fires, if the CH4
concentration in the building is between the LEL and the UEL, all that is required for an
explosion is a source of ignition (e.g., pilot light, electrical motor spark, static electricity,
stoves, and ranges, etc.).
This guidance document provides both modeling approaches and measurement procedures
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Emissions from Closed or Abandoned Facilities
for estimating the extent of subsurface vapor migration of LFG. The modeling approaches cover
theoretical vapor transport as a function of pressure-driven flow in soils. The measurement
procedures cover sampling methods for measuring LFG concentrations above the landfill, at
the property boundaries, and towards potentially affected buildings. In addition, monitoring
methods are provided for determining the concentrations of CH4 and COPCs in soil gas under
affected buildings and in building air.
1.4 ARARs Specific to Landfill Gas Emissions
Applicable or relevant and appropriate requirements (ARARs) as defined in the National
Contingency Plan (NCP) may include: (1) chemical-specific, (2) location-specific, and (3)
action-specific statutory requirements. These requirements include those established by the U. S.
EPA and other Federal agencies and those established by the state in which any release occurs,
if the State's standards are promulgated, more stringent than the Federal standards, and are
identified in a timely manner. Applicable requirements are Federal or state requirements that
"specifically address a hazardous substance, pollutant, contaminant, remedial action, location,
or other circumstance found at a CERCLA site" (NCP Sec. 300.5). Relevant and appropriate
require-ments are Federal or State laws that, while not applicable, "address problems or
situations sufficiently similar to those encountered at the CERCLA site that their use is well
suited to the particular site." (NCP Sec. 300.5). For the air pathway, ARARs are typically
classified as either chemical-specific or action-specific and can be divided further into either
Federal or State ARARs.
1.4.1 Federal Air Pathway ARARs
Federal air pathway action-specific ARARs include the New Source Performance Standards
(NSPS) and the Emission Guidelines (EG) for MSW Landfills under the Clean Air Act (CAA);
process and remedial technology emission limits under Subtitle D of RCRA; and RCRA
Subtitle C requirements for explosive gases control.
The NSPS for MSW landfills is applicable only for "new" landfills that began construction,
modification, or reconstruction on or after May 30, 1991. Modifications can include lateral and
vertical expansions of the landfill. The EG for MSW landfills is applicable for "existing"
landfills that accepted waste on or after November 8, 1987. In addition, both the NSPS and the
EG are applicable only for relatively large landfills with NMOC annual emissions above 50
megagrams per year. The NSPS may be an ARAR if the Superfund landfill (SFL) is a
subsection of a "new" landfill still accepting waste. In most cases, however, the EG—Section
111 (d) Plan—is more likely to constitute the maj or action-specific ARAR for landfills no longer
accepting waste. EPA has determined that although the EG may not be applicable for a given
site because it does not meet the waste acceptance cutoff date, the EG may still be relevant and
appropriate if the landfill design capacity cutoff value (2.5 million Mg or 2.5 million m3) and
NMOC annual emission cutoff value (50 Mg/yr) are met or exceeded. The substantive
requirements of the NSPS and EG include installation of a LFG capture system and emission
control requirements as well as monitoring requirements.
Promulgated EG under 40 CFR Part 60 are not enforceable by either EPA or the States. To
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Guidance for Evaluating Landfill Gas
be enforceable, Section 11 l(d) of the CAA requires that the EG requirements be stipulated in
either a Federal or an approved State implementation plan, codified in 40 CFR Part 62. The
Federal plan acts as an enforceable place holder until EPA approves the State plan. There
should be no fundamental difference in the requirements of the Federal plan and an EPA
approved State plan. This is discussed further in Chapter 4, Section 4.1.
Air pathway rules for the treatment or disposal of hazardous wastes may be applicable or
relevant and appropriate requirements under specific circumstances. LFG is not a hazardous
waste. If, however, solid wastes are excavated and/or treated, or if a liquid waste stream is
treated, the air emission standards for process vents, equipment leaks, containers, tanks, and
surface impoundments may apply. Liquid waste streams such as leachate may be considered
hazardous waste if precipitation has percolated through land disposal wastes comprised of more
than one restricted waste classified under RCRA Part 261. Even if landfill records are lacking
that determine if specific restricted waste streams have been deposited in a landfill, the leachate
would have to undergo the toxicity characteristic leaching procedure (TCLP) and other RCRA
characteristic waste tests as specified in 40 CFR §261.20 through §261.24. If the leachate fails
one or more of these tests, it is considered a RCRA characteristic hazardous waste. The
characteristic waste tests would also apply to any collected LFG condensate. If the leachate or
condensate is considered a listed or characteristic hazardous waste and is treated (e.g., by air
stripping) or disposed of (e.g., by burning in an enclosed flare), the RCRA rules governing
treatment and/or incineration of hazardous waste may apply.
Finally, RCRA Part 258 specifies the control requirements for explosive gases at new MSW
landfills, existing MSW landfills, and lateral expansions of existing MSW landfills. These
requirements are considered ARARs and include the establishment of a routine CH4 monitoring
program to detect whether the LFG CH4 concentrations within facility structures exceed 25
percent of the LEL or exceed the LEL at the property boundary. At 25 °C, the LEL of CH4 in
air is approximately 5 percent. If one or both of these levels are exceeded, the rules require the
owner or operator of the landfill to immediately take steps to protect human health and to
implement a remediation plan. The Federal ARARs mentioned above are discussed in greater
detail in Chapter 4 of this document. There is no national engineering or building code for the
design or construction for LFG control systems.
1.4.2 State Air Pathway ARARs
State air pathway ARARs may include a variety of action-specific and chemical-specific
regulatory requirements. State air pathway ARARs may include emission limits based on an
emission rate (e.g., pounds per hour) or based on a stack concentration (e.g., parts per billion
by volume). These limits may be pollutant-specific or apply to a specified chemical class (e.g.,
NMOC). State ARARs may also include ambient air standards for the traditional "criteria"
pollutants such as particulate matter and sulfur dioxide (SO2) or may be risk-based ambient air
standards for specific carcinogenic and noncarcinogenic pollutants. State rules may also dictate
the type and frequency of CH4 monitoring programs at MSW landfills and may include nuisance
or odor regulations designed to prevent the excessive release of malodorous compounds.
Finally, landfill monitoring or sampling requirements may be more stringent than those of the
Federal EG Part 258 rules.
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Emissions from Closed or Abandoned Facilities
1.5 Potential Landfill Problem Areas
The following are potential air pathway problem areas particular to both MSW and co-
disposal landfills that should be carefully considered. Other potential areas of concern for the
air pathway may be present at a given site due to site-specific factors.
1.5.1 Landfill Cover Emissions
In some cases, the landfill may be capped with a simple soil cover. In addition, a passive
vent system may also be employed to vent LFG to the atmosphere. Under this scenario, the
majority of the landfill gas may be emitted through cracks and gaps in the cover or directly
through the soil and not necessarily through the passive vents. In this type of situation, the
radius of influence of a passive vent is relatively small whhereas the transport of landfill gas
is multi-dimensional and will take the path of least resistance. In such cases, exposure to
emissions of LFG into ambient air are likely to be the greatest at the landfill perimeter. This
may be especially problematic if relatively high concentrations of toxic NMOCs in the LFG are
located in perimeter sections of the landfill near potential receptors.
1.5.2 Risks Due To Indoor Vapor Intrusion
Subsurface lateral migration of LFG is a potential exposure pathway. Lateral migration may
be especially problematic when surface soils are frozen or when surrounding areas are paved.
These situations result in a higher subsurface pressure gradient and, thus, longer transport
distances. If indoor air concentrations are found to be below the LEL of CH4, this pathway
cannot be dismissed simply because an explosive detonation or fire cannot occur. Although the
risk of a CH4 explosion does not exist below the LEL, the vapor concentrations of the toxic
LFG constituents may still be unacceptable. For example, the 1-in-1,000,000 risk-based
residential air concentration of vinyl chloride is approximately 0.072 mg/m3. Given a typical
residential building air exchange rate and a relatively small subsurface vapor intrusion rate, an
indoor air concentration of vinyl chloride greater than 0.072 mg/m3 is possible even if the
methane concentration of the LFG entering the house is less than the LEL.
1.5.3 Landfill Fires and Explosions
Landfill fires and explosions occur when ambient air infiltrates the landfill wastes providing
enough oxygen to support combustion and locally diluting the CH4 concentration below the
UEL. Air infiltration can occur by various means. Landfill subsidence can cause cap or cover
slippage leaving air infiltration gaps or can actually expose the waste to ambient air. In addition,
active gas collection systems purge LFG from the landfill by drawing a vacuum at each
collection well. If the landfill cover leaks at the point of penetration of one or more collection
wells, ambient air can be drawn down the annulus of the well and into the wastes.
1.5.4 Emissions of Toxic LFG Constituents
Co-disposal landfills are typically remediated under the Superfund program because of the
hazardous or toxic wastes that have been deposited in the landfill. These wastes may contain
constituents that become part of the LFG but at levels which are below the detection limit of
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Guidance for Evaluating Landfill Gas
the field instruments commonly used to detect VOC. For example, PCBs or other extremely
toxic compounds may have been dumped within a given landfill. In such cases, LFG sampling
and analytical procedures capable of detecting these types of compounds should be employed.
1.6 Document Organization
The remainder of this document is divided into five chapters and appendices. Chapter 2
covers the generation of LFG as well as techniques for assessing the ambient air impacts from
LFG emissions under baseline or uncontrolled conditions. Chapters discusses sub surf ace vapor
migration of LFG. Techniques are provided for assessing the extent of pressure-driven sub-
surface vapor migration beyond the site boundary and possible vapor intrusion into buildings.
In addition, procedures are discussed for assessing possible subsurface vapor intrusion into
buildings as a result of contaminated groundwater. Chapter 4 provides a more detailed
description of Federal and State air pathway ARARs including the CAA NSPS and EG for
MSW landfills. This chapter also discusses the individual rules under RCRA and general State
rules that may be ARARs. Chapter 5 covers LFG capture and control systems commonly in use
at both Superfund and MSW landfills under RCRA Subtitle D. Appendix A provides sampling
and analytical methods for determining: (1) the composition of LFG, (2) the concentrations of
LFG constituents in ambient air, and (3) the concentrations of LFG constituents in indoor air
as a result of indoor vapor intrusion. Appendix B contains a Generic Quality Assurance Proj ect
Plan (QAPP). Appendix C includes a discussion of the methodology and statistical procedures
used to determine if the landfill emission can be characterized as homogeneous.
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Emissions from Closed or Abandoned Facilities
2. Landfill Gas Generation and Transport
This chapter covers the generation of LFG within MSW and co-disposal landfills as well
as the emissions of toxic constituents in landfill gas. Modeling concepts and procedures are also
introduced for estimating the emissions of LFG and the individual emissions of hazardous or
toxic LFG constituents. Modeling procedures are also provided for dispersing LFG COPCs in
ambient air and for estimating exposure point air concentrations. Finally, ambient air sampling
is discussed for measuring air concentrations at potential exposure points.
2.1 Landfill Gas Generation
CH4 and CO2 are the primary constituents of LFG and are produced by microorganisms
within the landfill under anaerobic conditions. Carbohydrates from paper, cardboard, and other
waste material, which form the major components of refuse, are decomposed initially to sugars,
then mainly to acetic acid, and finally to CH4 and CO2 (U.S. EPA, 1997a).
LFG generation, including rate and composition, proceeds through four characteristic
phases throughout the lifetime of a landfill. Figure 2-1, from the Emission Factor Documenta-
tion for AP-4 2, Section 2-4, Municipal Solid Waste Landfills (U.S EPA, 1997a), is a graphical
representation of typical LFG evolution. Bacteria decompose landfill waste in four phases. The
composition of the gas produced changes with each of the four phases of decomposition. Land-
fills often accept waste over a 20- to 30-year period, so waste in a landfill may be undergoing
several phases of decomposition at once. This means that older waste in one area might be in
a different phase of decomposition than more recently buried waste in another area.
During the first phase of decomposition, aerobic bacteria—bacteria that live only in the
presence of oxygen—consume O2 while breaking down the long molecular chains of complex
carbohydrates, proteins, and lipids that comprise organic waste. The primary byproduct of this
process is carbon dioxide. Nitrogen content is high at the beginning of this phase but declines
as the landfill moves through the four phases. Phase I continues until available O2 is depleted.
Phase I decomposition can last for days or months, depending on how much O2 is present when
the waste is disposed of in the landfill. Oxygen levels will vary according to factors such as how
loose or compressed the waste was when it was buried.
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Guidance for Evaluating Landfill Gas
Gas Composition, % by volume
_i|oto.b.^
III
IV
1 Aerobic
II Anaerobic, non-methanogenic
III Anaerobic, methanogenic, unsteady
IV Anaerobic, methanogenic, steady
* " *»^
\ ^
"/...
CHy/
^ /
* S ^\^
* ^^ ^^^X.
^C ^^-^
. 55%
— '—
40%
5%
Time After Placement
Note: Time scale (total time and phase duration) of gas generation varies
with landfill conditions (i.e., waste composition and anaerobic state).
Figure 2-1. Landfill Gas Evolution (Tchobanoglous et al., 1993)
Phase II decomposition starts after the O2 in the landfill has been used up. Using an
anaerobic process (a process that does not require oxygen), bacteria convert compounds created
by aerobic bacteria into acetic, lactic, and formic acids and alcohols such as methanol and
ethanol. The landfill becomes highly acidic. As the acids mix with the moisture present in the
land-fill, they cause certain nutrients to dissolve, making nitrogen and phosphorus available to
the increasingly diverse species of bacteria in the landfill. The gaseous byproducts of these
processes are carbon dioxide and hydrogen. If the landfill is disturbed or if O2 is somehow
introduced into the landfill, microbial processes will return to Phase I.
Phase III decomposition starts when certain kinds of anaerobic bacteria consume the organic
acids produced in Phase II and form acetate, an organic acid. This process causes the landfill
to become a more neutral environment in which methane-producing bacteria begin to establish
themselves. Methane- and acid-producing bacteria have a symbiotic, or mutually beneficial,
relationship. Acid-producing bacteria create compounds for the methanogenic bacteria to
consume. Methanogenic bacteria consume the carbon dioxide and acetate, too much of which
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Emissions from Closed or Abandoned Facilities
would be toxic to the acid-producing bacteria.
Phase IV decomposition begins when both the composition and production rates of landfill
gas remain relatively constant. Phase IV landfill gas usually contains approximately 45 to 60
percent CH4 by volume, 40 to 60 percent CO2, and 2 to 9 percent other gases, such as sulfides.
Gas is produced at a stable rate in Phase IV, typically for about 20 years; however, gas will
continue to be emitted for 50 or more years after the waste is placed in the landfill. Gas
production might last longer, for example, if greater amounts of organics are present in the
waste, such as at a landfill receiving higher than average amounts of domestic animal waste.
The first phase is aerobic (i.e., while O2 is available), and the primary gas produced is CO2.
The second phase is characterized by O2 depletion, resulting in an anaerobic environment where
large amounts of CO2 and some hydrogen (H2) are produced. In the anaerobic third phase, CH4
production begins, with an accompanying reduction in the amount of CO2 produced. Nitrogen
content is initially high in LFG in the aerobic first phase and declines sharply as the landfill
proceeds through the anaerobic second and third phases. In the fourth phase, gas production of
CH4, CO2, and N2 becomes fairly steady. The phase, duration, and timing of gas generation vary
with landfill conditions (i.e., waste composition, cover materials, moisture content, temperature,
pH, etc.) and may also vary with climatic conditions such as precipitation rates and tempera-
tures.
Emissions of NMOCs, including COPCs, result from NMOCs originally contained in the
land filled waste and from their creation from biological processes and chemical reactions
within the landfill. For example, benzene may be a component of petroleum-derived solvents,
whereas vinyl chloride is typically formed from the breakdown of chlorinated solvents, such
as trichloroethylene, trichloroethane, and perchloroethylene.
The rate of LFG emissions is governed by gas production and transport mechanisms.
Production mechanisms involve the production of the emission constituent in its vapor phase
through vaporization, biological decomposition, or chemical reaction. Production mechanisms
are affected by a variety of factors.
Vaporization is affected by the concentration of the individual compounds in the landfill,
the physical properties of the individual compounds, and the specific landfill conditions (i.e.,
temperature and confining pressure). Biological decomposition of liquid and solid compounds
into other chemical species depends on:
• Nutrient availability for micro-organisms,
• Waste composition,
• The age of the landfill,
• Moisture content,
• pH,
• Temperature,
• O2 availability,
• Exposure to certain biological activity-inhibiting industrial wastes.
Accurate quantification of the impacts of any of these factors on LFG production is not
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Guidance for Evaluating Landfill Gas
possible with the current state of knowledge. Chemical reactions are dictated by the
composition of the waste, temperature, and moisture content in the landfill.
Temperature, age of the refuse, and pH also affect landfill gas production. A pH of 6.6 to
7.4 is thought to be optimal for CH4-generating microorganisms (methanogens). Temperature
affects microbial activity within the landfill, which in turn affects the temperature of the landfill.
The internal temperature of the landfill tends to be self-regulating because anaerobic
decomposition can typically heat the landfill interior to approximately 90 to 120 °F. Warm
landfill temperatures favor CH4 production, which may be affected by seasonal temperature
fluctuations in cold climates where the landfill is shallow and sensitive to ambient temperatures.
Transport mechanisms involve the transportation of volatile constituents in the vapor phase
to the surface of the landfill, through the air boundary layer above the landfill, and into the
atmosphere. There are two major mechanisms that enable transport of a volatile constituent in
its vapor phase: molecular diffusion and LFG convection (U.S. EPA, 1997a).
As with production mechanisms, transport mechanisms are affected by a variety of factors.
Molecular diffusion through a soil cover is influenced by the soil porosity, soil moisture
content, the existing concentration gradient, the diffusivity of the constituent, and the thickness
of the soil. Molecular diffusion through the air boundary layer is affected by the wind speed,
concentration gradient, and diffusivity of the constituent.
LFG convection occurs due to pressure changes within the landfill that are influenced by
nutrient availability for bacteria, waste composition, moisture content, landfill age, temperature,
pH, O2 availability, presence of a gas collection system, and biological activity-inhibiting
wastes (i.e., industrial wastes). Displacement of LFG due to compaction and settlement depends
on the degree of compaction, waste compatibility, and overburden weight (settlement).
Displacement can also occur through other mechanisms. Displacement can be influenced by
changes in atmospheric pressure. Displacement due to water table fluctuations is affected by
the presence of a liner, rate of evaporation, rate of precipitation, and the horizontal versus the
vertical permeability (U.S. EPA, 1997a).
Spatial and temporal variability are considered to be important relative to sampling.
Landfills are known to exhibit large variations in gas production from one area to the next. The
focus of the recommended sample design is to maximize the spatial coverage by collecting LFG
information from all vents and on-site structures and from locations that are established by
using a systematic 30-m by 30-m sampling grid that is defined by the landfill cover and extends
to 30 meters beyond the landfill boundary. This systematic screening technique is designed to
identify "hot spot" locations for both methane and NMOC. The screening results will be used
to identify locations that will be sampled for the COPCs. Depending on the landfill cover
material, it is assumed that the landfill vents will have higher LFG concentrations, and their
impact on the ambient air will be greater than the impacts derived from the surface emissions.
The sample design assumes that the emissions from the locations with the highest NMOC
concentration within each homogeneous area will adequately characterize the total landfill
emissions.
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Emissions from Closed or Abandoned Facilities
The sample design assumes that the proximity of off-site structures to the landfill boundary
is the dominant risk driver for subsurface vapor intrusion into off-site buildings via pressure
gradients. This assumption may be invalid if there are interceptors, diversion structures,
barriers, geologic faults, or preferential vapor pathways between the landfill and the building.
2.2 Estimation of Ambient Air Impacts
One of the primary routes of human exposure to LFG is inhalation of COPCs in ambient air.
In addition, compliance with Federal and State air pathway ARARs, as appropriate, must also
be assessed.
An assessment of ambient air impacts necessarily begins with an estimate of the LFG
emissions of NMOCs and COPCs. Under baseline conditions, LFG emissions typically occur
at or near ground-level through any existing cover or landfill vents. Atmospheric dispersion of
these types of emission sources results in maximum offsite impacts at the perimeter of the
landfill. It is therefore necessary to estimate the spatial variability of emissions across the areal
extent of the landfill.
If the landfill employs uncontrolled vents, each vent will be sampled separately. If vents are
not employed or if the area of influence for the vents is not adequate, LFG concentrations will
be delineated using a superimposed grid system. The number of sampling points will be
determined as a function of the landfill size, homogeneity of its contents, and the amount of
resources available for sampling and analysis activities. As long as there is no flexible mem-
brane liner (FML) soil gas sampling will be conducted approximately one meter below any
landfill cover using either a slam-bar or a Geo-probe depending on equipment availability and
soil properties. If there is an FML, arrangements must be made to make repairs or to use an
alternative sampling technique, such as open path Fourier transform infrared spectroscopy (OP-
FTIR), to estimate the emission rates.
The number of samples that must be obtained to estimate the mean concentration of an area
depends strongly on the heterogeneity of the chemical distribution. Thus, for an area with
uniform distribution, few samples are needed to provide good characterization. Conversely, an
area with widely variable distribution would require a great number of samples. For landfills
with nonuniform distribution, the total number of samples can be reduced by subdividing the
area into zones with similar levels of contamination and variability, age, volume, and surface
area . The objective of the screening effort is to identify the areas with near homogeneous
NMOC concentration. The Wilcoxon rank sum test (also known as Mann-Whitney test) will be
used to determine if there is an area with a higher mean concentration when compared to the
entire landfill. A grid density of 1 per 900 square meters (30^30 meter grid) is recommended
as point of departure. A higher density may be warranted if portions of the landfill are known
to differ significantly from one area to the next over a short lateral distance. On the other hand,
if the landfill is very large or the operating history indicates that what is buried in one area is
similar to that buried in another, a large grid may be needed in order to reduce the costs and
expenses associated with the characterization effort.
Emission estimating is an important step in conducting risk evaluations, obtaining permits,
2-5
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Guidance for Evaluating Landfill Gas
demonstrating compliance with regulatory limits, and in designing emission control systems for
solid waste landfills. There are several methods for measuring and analyzing LFG. The
chemical concentration may be determined via: (1) sampling at active and passive vents; (2)
using probes placed just below the cover; (3) OP-FTIR; (4) open path tunable diode laser
methods; (5) flux chamber methods; and (6) passive adsorption concentration gradient methods.
This document presents a step-wise procedure using readily available field instruments,
sampling probes placed just below the cover, routine analytical methods, and commonly used
fate and transport modeling procedures. The document also presents the results of an example
application of an open path OP-FTIR emission measurement method. The OP-FTIR was used
in conjunction with a radial plume mapping technique to estimate the emission rates and to
establish ambient air concentrations.
This document provides site investigators, risk managers, and design engineers with
procedures and methodologies that may be used to estimate LFG emissions and resulting
ambient air concentrations. The usefulness of this document was demonstrated at three study
sites that are illustrative of the techniques discussed herein. It is recognized that both tech-
niques—screening/sampling/modeling and optical remote scanning—have advantages and
disadvantages that must be taken into account. Decision makers must balance their need for
definitive site-specific information with that derived by generic fate and transport models. The
technique using field screening, sampling, and modeling procedures were used at two sites:
Rose Hill Regional Landfill, South Kingston, Rhode Island, and Bush Valley landfill in
Abingdon, Maryland. Both techniques were implemented at the Municipal Landfill Superfund
Site located in Somersworth, New Hampshire. Both techniques that are illustrated in the
guidance have been shown to be viable.
2.2.1 The Technique Using Probes Placed Just Below the Surface
This process is initiated with a first round of air sampling (screening) across the face of the
landfill using portable instruments as discussed in Appendix A. This is typically accomplished
using either biased (based on foreknowledge) or unbiased (randomly selected) grid sampling
depending on any previous knowledge of emission patterns or the spatial distribution of wastes.
If the landfill is covered by an impermeable membrane, this type of sampling is still appropriate
because the cover's integrity may have been compromised by differential settling, improper
installation, or unexpected surface activities such as rolling heavy equipment across it or
construction of structures and buildings. Screening level sampling uses portable instruments
that can detect total organic compounds (including CH4) and instruments that detect total
organics but are insensitive to CH4. From these data, the surface of the landfill and any passive
vents can be analyzed for emissions of both CH4 and NMOCs. These screening data also
provide information necessary to partition the surface of the landfill into areas of lesser
emission variability using the Wilcoxon statistical procedures. Hot spots are identified by using
the Wilcoxon statistical procedures (described elsewhere). Below the cover, LFG samples are
collected at hot spots for each nearly homogeneous areas of the landfill. The NMOC emissions
are used to estimate average or upper bound (e.g., 90th percentile) emissions of individual
COPCs for each area. It is important to understand that the extent of CH4 and NMOC emissions
may not correlate at a given location. That is, NMOC emissions may be higher or lower in
relation to CH4 emissions as a function of where the hazardous or toxics wastes were dumped.
2-6
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Emissions from Closed or Abandoned Facilities
Therefore, second-round sampling locations should be based on the screening data for NMOCs.
Second-round sampling involves methods for determining the LFG concentrations of individual
COPCs. These con-centrations can then be used to estimate landfill emissions based on
modeling. Appendix A provides information on sampling and analytical techniques that may
be used.
With data on the spatial distribution of LFG concentrations of COPCs, the analyst can use
these data as input values for emissions modeling. Estimated COPC emissions are then
dispersed in ambient air using either screening-level or refined atmospheric dispersion models
to estimate exposure point air concentrations for both onsite and offsite receptors as applicable.
These estimates of ambient air concentrations are then used to estimate human health risks and
to determine compliance with any air pathway ARARs for baseline conditions.
Figure 2-2 provides a general flow chart for estimating through modeling the ambient air
impacts from baseline emissions of LFG. Details of the flow chart are discussed in the
subsequent sections of this Chapter. As an alternative, air impacts can also be assessed using
ambient air sampling techniques. Section 2.2.5 provides guidance on estimating air impacts
from emissions of LFG COPCs. Appendix A provides information on sampling and analytical
procedures for ambient air sampling.
Start
Clnd Ambient Air
Analysis
Use LandGem Model
and 90th Percentile
Cones, to Estimate
Emissions by Stratum
and/or Vent
^
^
y-
Setup Periodic
Methane
Sampling
Program
Determine COPC
90th Percentile Cones.
for Each Stratum
and/or Vent
Use ISC3 Dispersion
Model to Estimate
Normalized Air Cones.
by Stratum and/or
Vent at Receptor(s)
ES —
1
|
j
L...
•
•
•
j
..is...
Determine
Relative NMOC
and Methane
Cones, from LF
Cover
Determine
Relative NMOC
and Methane
Cones, from
Vents
Perform Max.
Cone.
Screening-Level
Analysis
Subdivide Site into
Strata of Similar
COPC Cone.
Variability
j
Perform Risk
Calculations
Construct
— ^ Detailed LFG
Sampling Plan
Option 1 Perform
4 : Detailed LFG u
Sampling 'n
'
4
se Options
Appendix
/End Ambient Air A
°Ption2 (^ Analysis J
« t
NO
^Ts Target Risk^v
^ — Exceeded? '
YES
Mediate
STOP Ambient A
Impacts
ir
Figure 2-2. Flow Chart for Assessing Air Impacts by Modeling.
2-7
-------
Guidance for Evaluating Landfill Gas
2.2.1.1 Estimating Uncontrolled Landfill Gas Emissions
The recommended methods for estimating emissions of LFG constituents at Superfund
landfills (SFLs) are the same as those developed for MSW landfills and published in AP-42
(U.S. EPA, 1997'a, 1997b). Alternative methods using OP- FTIR and optical remote sensing
radial plume mapping techniques are discussed in Appendix A. To estimate uncontrolled
emissions of the various constituents present in LFG, total LFG emissions must first be
estimated. Uncon-trolled CH4 emissions are estimated with a theoretical first-order kinetic
model of CH4 production. This model is known as the Landfill Gas Emissions Model
(LandGEM). A version of LandGEM for the personal computer (PC) can be downloaded from
EPA's website at http://www.epa.gov/ttn/catc/products.html#rblcsoftware (accessed September
2005). A user's manual is also available on this website. It should be noted that the LandGEM
model described in this document has been modified. The Beta version is PC-based software
for estimating emissions of CH4, CO2,NMOCs, and HAPs from municipal solid waste landfills.
There are two sets of default values in LandGEM. One, the CAA set, is based either on the
NSPS requirements for emissions to the atmosphere from new municipal solid waste landfills
or on the Federal EG for emissions from existing landfills. These regulations and guidelines are
contained in the Code of Federal Regulations, Title 40, Part 60, (40CFR60) Subparts WWW
and Cc, respectively. This set of default values produce conservative emission estimates that
can be used to determine the applicability of Federal regulations or guidelines to the landfill
being evaluated. For more information on the assumptions used in the model and the CAA
default set, see the background information document (U. S. EPA, 1991) or public docket (A-88-
09) for the landfill NSPS and guidelines.
The other set of values, the AP-42 set, is based on emissions factors in EPA's guidance
document, Compilation of Emission Factors, Fifth Edition, AP-42 (U.S. EPA, 1997b). This set
of default values is less conservative than the CAA set and can be used to produce typical
emission estimates in the absence of site-specific test data. The AP-42 values used in this Beta
version of LandGEM have been revised and are available for public comment. Once AP-42
revisions have been published as final, the AP-42 default set in LandGEM will be revised
accordingly, and the final version of the model will be issued. Although this is a Beta version
and subject to additional testing, all software components of LandGEM are fully functional.
LandGEM can be used to estimate mass emissions of NMOCs to assess applicability of a
site with regards to the NSPS and EG. The model can also be used to estimate mass emissions
of the COPCs by using either default or user-specified LFG concentration data. The following
discussion provides details on the equations and underlying data used in LandGEM (and
documented in AP-42) to estimate LFG emissions.
The equation used to estimate the generation rate of CH4 within LandGEM is
« i ( M \
Z^~^ 1V1 i -Irt
£^°~fifr 2-1
i=\ j=o.i \ iv ;
where:
QCH = annual CH4 generation during the year of the calculation in cubic meters per year,
2-8
-------
Emissions from Closed or Abandoned Facilities
/' = 1 year time increment,
n = (year of the calculation) - (initial year of waste acceptance),
7 = 0.1 year time increment,
k = methane generation rate in reciprocal years,
L0 = potential methane generation capacity in cubic meters per megagram,
Mt = mass of waste accepted in the /'th year in megagrams,
tv = age of the/h section of waste mass Mt accepted in the /'th year (decimal years, e.g.,
3.2 years).
LandGEM provides a mass emission rate that is used in a dispersion model to provide
ambient concentrations. Other fates may exist for the gas generated in a landfill, including
capture and microbial degradation within the landfill's surface layer. Currently, there are no
data that adequately address this fate. It is generally accepted that the bulk of the gas generated
will be emitted through the cover materials or cracks and other openings in the landfill surface,
taking the path of least resistance. Some oxidation will occur as gas diffuses through the soil
cover, but this is typically thought to be less than 10%.
Site-specific landfill information is generally available for the variables Mh c, and t. When
refuse acceptance rate information is scant or unknown, Mt can be determined by dividing the
mass of refuse in-place by the age of the landfill. The average annual acceptance rate should
only be estimated by this method when there is inadequate information available on the actual
average acceptance rate.
To determine the amount of waste in place, an estimate of the volume of the landfill must
be made. Often information on the area of the landfill can be obtained from topographic maps,
aerial maps, or previous surveys of the waste boundaries. The depth of the landfill can be
determined from surveys (e.g., borings) of the waste depth. In some cases, topographic maps
may be useful in estimating waste depth. Because the density of the waste is difficult to
establish, a recommended value of 625 kg/m3 (1,800 lb/yd3) should be used (NSWMA, 1985).
This value is based on MSW that has undergone compaction and some degree of degradation
and settling.
If there are data on the fraction of nondegradable wastes for a site, this waste mass can be
excluded from the calculation of Mt. This issue is significant for SFLs, because the potential
exists for disposal of large portions of nondegradable waste. Nondegradable waste includes
concrete, brick, stone, glass, piping, plastics, and metal objects. The time variable, t, includes
the total number of years that the waste has been in-place including the number of years that
the landfill has accepted waste and, if applicable, has been closed.
Values for L0 and k must be estimated. Estimation of the potential CH4 generation capacity
of refuse (L0) is generally treated as a function of the moisture and organic content of the refuse.
Estimation of the CH4 generation constant (K) is a function of a variety of factors, including
moisture, pH, temperature, other environmental factors, and landfill operating conditions.
Specific CH4 generation constants can be estimated by the use of EPA Reference Method 2E
(40 CFR Part 60 Appendix A); however, default values are often used.
2-9
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Guidance for Evaluating Landfill Gas
LandGEM includes both regulatory default values and recommended AP-42 default values
for L0 and k. The regulatory defaults were developed for the purposes of determining the
applicability of the NSPS/EG. As a result, LandGEM contains conservative L0 and k default
values in order to protect human health, to encompass a wide range of landfills, and to
encourage the use of site-specific data.
LandGEM also contains the AP-42 defaults that are recommended for use in assessing SFL
emissions. A default lvalue of 0.04/yr should be used for areas receiving 25 in (63.5 cm) or
more of rain per year, but a default k value of 0.02/yr should be used in drier areas (less that 25
in/yr). An L0 value of 100 m3/Mg-refuse (3,530 ft3/ton) is appropriate for most landfills.
Although the recommended default k and L0 values are based on the best fit to 21 different
landfills, the predicted CH4 emissions ranged from 38 to 492 percent of the actual emissions and
exhibited a relative standard deviation of 0.85.
It should be emphasized that in order to comply with the NSPS or EG, the regulatory default
values for k and L0 must be applied as specified in the final rule. The regulatory default values
of k andL0 are 0.05/yr and 170 m3/Mg, respectively.
When gas generation reaches steady-state conditions, LFG consists of approximately
40 percent by volume CO2, 55 percent CH4, 5 percent N2 (and other gases), and trace amounts
of NMOCs. Therefore, the estimate derived for CH4 generation using LandGEM can also be
used to represent CO2 generation. The sum of the CH4 and CO2 emissions is a reasonable
estimate of total LFG emissions. If site-specific information is available to suggest that the CH4
content of LFG is not 55 percent, then the site-specific information should be used, and the CO2
emissions estimate should be adjusted accordingly.
Most of the NMOC emissions result from the volatilization of organic compounds contained
in the landfilled waste and subsequent transport in the LFG. The current version of the
LandGEM model contains a regulatory default concentration value for total NMOC of
4,000 part per million by volume (ppmv), expressed as hexane. Available data, however, show
that there is a considerable range for total NMOC values from landfills. The regulatory default
value for NMOC concentration was developed for regulatory compliance purposes. For
emissions inventory purposes, site-specific information should be taken into account when
determining the total NMOC concentration (i.e., using EPA Reference Methods 25C or 18
found in 40 CFR 60, Appendix A).
If a site-specific NMOC concentration is available, it must be corrected for air infiltration
which can occur by two different mechanisms: LFG sample dilution and air intrusion into the
landfill. These corrections require site-specific data for the LFG CH4, CO2, N2, and O2 content
(i.e., from EPA Reference Method 3C found in 40 CFR 60, Appendix A). If the ratio of N2 to
O2 is less than or equal to 4.0 (as found in ambient air), then the total pollutant concentration
is adjusted for sample dilution by assuming that CO2 and CH4 are the primary (100 percent)
constituents of LFG, and the following equation is used:
Cp(corrected) =
2-10
-------
Emissions from Closed or Abandoned Facilities
where:
CP = COPC Concentration in LFG in parts per million by volume,
CCQ = CO2 concentration in LFG in parts per million by volume,
CCH = CH4 concentration in LFG in parts per million by volume.
If the ratio of N2 to O2 concentrations is greater than 4.0, the total pollutant concentration
should be adjusted for air intrusion into the landfill by using Equation 2-2 and adding the
concentration of N2 (i.e., CN^) to the denominator. Values for CCQ2, CCH4, CNs, and CO2 can be
obtained using EPA Reference Method 3C.
To estimate emissions of NMOCs or other COPCs, the equation that should be used is
QP = 1.
x
2-3
where:
QP = Emission rate of COPC in cubic meters per year,
QcH4 = CH4 generation rate in cubic meters per year (e.g., from LandGEM),
CP = COPC Concentration in LFG in parts per million by volume,
1.82 = Multiplication factor (assumes that 55% of LFG is CH4 and 45% is CO2, N2,
and other constituents),
106 = Constant to correct units as parts per million by volume.
Uncontrolled mass emissions per year of NMOC (as hexane), CO2, CH4, and COPCs can
be estimated by
UMP = g
MWP x latm
R x 1,000 x (273+ T)
2-4
where:
UMP = Uncontrolled mass emissions of COPC in kilograms per year,
MWD = Molecular weight of COPC in grams per gram-mole,
NMOC emission rate of COPC in cubic meters per year,
Temperature of landfill gas in degrees Celsius,
Gas constant (8.205 x 10'5 m3-atm/gmol-K),
Constant to convert grams to kilograms.
QP
T
R
1,000
This equation assumes that the operating pressure of the system is approximately
1 atmosphere. If the temperature of the LFG is unknown, a temperature of 25 °C (77 °F) is
recommended.
Table 2-1 lists the AP-42 default LFG concentrations for several common COPCs. It is
important to note that the COPCs listed in Table 2-1 are not the only compounds likely to be
present in LFG. The listed COPCs are those that were identified through a review of the
available literature. The reader should be aware that additional compounds are likely to be
present, such as those associated with consumer or industrial products.
2-11
-------
Guidance for Evaluating Landfill Gas
Table 2-1. Default Concentrations for Landfill Gas Copes'
COPC
1,1,1-Trichloroethane (methyl chloroform)
1,1-Dichloroethene (vinylidene chloride)
1,2-Dichloroethane (ethylene dichloride)
Acrylonitrile
Benzene
Carbon tetrachloride
Chlorobenzene
Chlorofluorocarbons ° (as
dichlorodifluoromethane)
Chloroform
Dichlorobenzene e
Dichloromethane (methylene chloride)
Ethyl chloride
Ethylene dibromide
Hydrogen sulfide
Mercury (total) f
Perchloroethylene (tetrachloroethylene)
Toluene
Trichloroethylene (trichloroethene)
Vinyl chloride
Xylenes (all isomers)
*^fij iviuicLuiai •
Number Weight
71-55-6
120-82-1
107-06-2
107-13-1
71-43-2
56-23-5
108-90-7
nad
67-66-3
106-46-7
75-09-2
75-00-3
106-93-4
7783-06-4
7439-98-7
127-18-4
108-88-3
79-01-6
75-01-4
133-20-7
133.42
96.94
98.96
53.06
78.11
153.84
112.56
120.91
119.39
147.00
84.94
64.52
187.88
34.08
200.61
165.83
92.13
131.38
62.50
106.16
AP-42
Default
0.48
0.20
0.41
6.33
11.1
0.004
0.25
19.7
0.02
0.21
14.3
1.25
0.001
35.5
2.92 x IQ-4
3.73
165
2.82
7.34
12.1
90th
Percentile
3.82
15.1
32.0
28.3
92.6
0.22
9.92
56.0
2.11
0.33
45.6
6.51
0.001
81.3
0.001
15.1
380
7.88
18.6
77.9
a Source: EPA, 1997a.
b Constituents associated with carcinogenic or chronic non-carcinogenic health effects which are routinely measured.
c Concentrations derived from four Chlorofluorocarbons commonly found in LFG.
d na = not applicable
e Source tests did not indicate whether this compound was the para- or ortho- isomer. The para isomer is a Title Ill-listed
HAP.
f No data were available to speciate total Hg into the elemental and organic forms.
Warning: AP-42 undergoes periodic review and updates are published after the peer review
process is completed. A work group has been established to review Section 2.4 - Municipal
Landfill. Readers are cautioned to check for updates.
As shown from the equations presented above, developing uncontrolled emission rates for
one or more COPCs can be a time-consuming process. Hence, it is recommended that the
LandGEM program be used to quickly develop these estimates. Figure 2-3 is an example of
output from LandGEM. This example is for vinyl chloride emissions; however, estimates for
total NMOCs and for other COPCs can also be generated by LandGEM. The example shown
in Figure 2-3 is for a landfill that began accepting wastes in 1969 and closed in 1980. The vapor
concentration of vinyl chloride in the LFG was measured for site-specific conditions. CH4
2-12
-------
Emissions from Closed or Abandoned Facilities
generation (and thus vinyl chloride emissions) is estimated to peak in 1980 and continue well
beyond the year 2268 (as stated above, all of the CH4 generated and associated COPCs are
assumed to be emitted). Figure 2-4 is a graphical example of the data shown in Figure 2-3.
Figure 2-3. Sample Output from the LandGEM Model
Model Parameters
Lo: 100.00 mA3/Mg
k: 0.0400 1/yr
NMOC : 595.00 ppmv
Methane : 50.0000 % volume
Carbon Dioxide : 50.0000 % volume
Air Pollutant: Vinyl Chloride (HAP/VOC)
Molecular Wt= 62.50 Concentration = 7.340000 ppmV
Landfill Parameters
Landfill type : Co-Disposal
Year Opened : 1969 Current Year : 1999 Closure Year: 1980
Capacity : 792000 Mg
Average Acceptance Rate Required from
Current Year to Closure Year : 0.00 Mg/year
Model Results
Year
Vinyl Chloride (HAP/VOC) Emission Rate
Refuse In Place (Mg) (Mg/yr) (Cubic m/yr)
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
7.200E+04
1.440E+05
2.160E+05
2.880E+05
3.600E+05
4.320E+05
5.040E+05
5.760E+05
6.480E+05
7.200E+05
7.920E+05
7.920E+05
7.920E+05
1.099E-02
2.155E-02
3.170E-02
4.144E-02
5.081E-02
5.981E-02
6.845E-02
7.676E-02
8.474E-02
9.241E-02
9.977E-02
9.586E-02
9.210E-02
4.228E+00
8.290E+00
1.219E+01
1.594E+01
1.955E+01
2.301E+01
2.633E+01
2.953E+01
3.260E+01
3.555E+01
3.838E+01
3.688E+01
3.543E+01
1998
1999
2000
7.920E+05
7.920E+05
7.920E+05
4.857E-02
4.666E-02
4.483E-02
1.868E+01
1.795E+01
1.725E+01
2266
2267
2268
7.920E+05
7.920E+05
7.920E+05
1.073E-06
1.031E-06
9.907E-07
4.128E-04
3.967E-04
3.811E-04
2-13
-------
Guidance for Evaluating Landfill Gas
120
100
5 80 }
Q>
60
40
> 20
1969 1979 1989 1999 2009 2019 2029 2039
Year
Figure 2-4. Example COPC Emission Estimates Produced by LandGEM.
2.2.1.2 Measuring LFG Constituent Concentrations
The constituents of LFG include CH4, CO2, N2, O2, NMOCs, and individual COPCs. These
LFG constituents may need to be measured for a variety of purposes. To establish whether the
CAA NSPS or EG controls are applicable to a specific landfill, the NMOC maximum annual
emissions must be greater than or equal to 50 Mg/yr. In a Tier I analysis, the LandGEM model
is used to estimate these emissions with a landfill gas NMOC concentration set equal to the
regulatory default value of 4,000 ppmv, expressed as hexane. A Tier I analysis further specifies
that the CH4 generation rate constant (k) and the CH4 generation potential (Lg) be set equal to
the regulatory default values of 0.05 /yr and 170 m3/Mg, respectively. If the maximum annual
NMOC emission rate is greater than or equal to 50 Mg/yr and the design capacity and
applicability cutoff dates are triggered, the landfill may be subject to the NSPS or EG. A Tier
II analysis allows for a site-specific determination of the landfill gas NMOC concentration. This
value is determined using EPA Reference Methods 25C or 18. The NMOC concentration (as
well as the concentrations of COPCs), however, must then be corrected for any air infiltration
using Equation 2-2. This equation requires the site-specific LFG concentrations of CH4, CO2,
N2, and O2 as determined by EPA Reference Method 3C.
To determine the LFG concentrations of three reduced sulfur species on the CAA HAP list
(carbonyl sulfide, captan, and carbon disulfide), EPA Reference Method 15 can be used. The
LFG concentrations of mercury (Hg) can be determined using EPA Method IO-5. EPA
Reference Methods 3C, 25C, and 15 can be found in Appendix A of 40 CFR 60; EPA Method
IO-5 can be found in the Compendium of Methods for the Determination of inorganic
Compounds in Ambient Air, EPA/625/R-96-010a, June 1999.
2-14
-------
Emissions from Closed or Abandoned Facilities
The LFG concentrations of the volatile constituents found in Table 1-1, as well as of other
volatiles, can be determined using EPA Compendium Method TO-15 as found in the
Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air,
Second Edition, EPA/625/R-96-010b, January 1999. These analytical methods are associated
with whole air sampling methods such as the use of specially treated canisters. Appendix A
details several sampling and analytical methods pertinent to the determination of LFG
constituent concentrations sampled within the landfill wastes, at the landfill property boundary,
and within a LFG collection system. Appendix A also provides sampling and analytical
methods for determining ambient air concentrations and indoor air concentrations of LFG
COPCs.
With a determination of site-specific LFG concentrations of COPCs and NMOCs, the
LandGEM model may be used to estimate more accurate annual emissions of these pollutants.
This allows for a more confident determination as to the maximum annual NMOC emissions
for NSPS/EG applicability. It also allows for a site-specific estimate of COPC emissions and
thus an evaluation of the resulting risks, as well as an evaluation of compliance with State or
local air pathway ARARs specific to baseline or uncontrolled conditions.
2.2.1.3 Estimating Time-Aver aged Emission Rates
The LandGEM model will not only produce an estimate of the annual CH4 emission rate
from a given landfill, but will also produce a similar annual emissions profile for specified
COPCs as depicted in Figure 2-4. For risk evaluation purposes, however, what is usually
required is a time-averaged emission rate. An estimation of the time-averaged emission rate can
be accomplished by using a trapezoidal approximation of
where:
< E > = Time-averaged emission rate in megagrams per year,
ED = Exposure duration in years,
E(t) = Emission rate at time t from LandGEM in megagrams per year,
t = Time in years.
The trapezoidal approximation of the integral in Equation 2-5 is calculated by
1
< E>=
*- -- -- -- -•
ED
where:
h = Time-step interval in years (h = 1 yr),
E0,i,2...n = Emission rate at the end of the first year (E0) and each succeeding year from
LandGEM in megagrams per year,
n = Number of time-steps (n = ED).
2-15
-------
Guidance for Evaluating Landfill Gas
Equation 2-6 may be entered into a spreadsheet program such as Microsoft Excel by
< E > (]/££>)* (/»/2> (E0 + 2* SUM(El:E^)+En) 2-7
For example, if the exposure duration (ED) were 30 years and the annual emissions of vinyl
chloride were used from Figure 2-3 for the years 1999 through 2028, the time-averaged
emissions calculated by Equation 2-6 over this 30 year period would be 2.670* 10"2 Mg/yr. This
time-averaged emission rate may then be entered into an atmospheric dispersion model to
estimate the average exposure point air concentration of vinyl chloride at a specified onsite or
offsite receptor. With an estimate of the average ambient air exposure point concentration, the
incremental cancer risk for exposure to vinyl chloride in ambient air can be calculated.
If we assume that the areal extent of the landfill is approximately 16 acres configured as a
square and that the LFG emissions are homogeneously distributed, a screening-level dispersion
modeling analysis yields an estimate of the offsite maximum annual average air concentration
equal to 0.17 mg/m3. For carcinogenic contaminants and residential exposure assumptions, the
incremental risk is calculated by
URF xEFxEDxCA
Risk = 2-8
ATC x 365 days / yr
where:
URF = Unit risk factor for vinyl chloride [4.4x 10'6 (mg/m3)'1],
EF = Exposure frequency (350 days/yr),
ED = Exposure duration (30 yr),
CA = Annual average ambient air concentration (0.17 mg/m3)
ATC = Averaging time for carcinogens (70 yr).
Therefore, the incremental cancer risk associated with 30 years of residential exposure to vinyl
chloride is
4.4 xlO"6x 350x30x0.17 7
Risk = = 3.1 x 10"7
70x365
The result of the preceding risk evaluation example indicates that the incremental cancer
risk from offsite residential exposure to vinyl chloride might be acceptable (i.e., less than 1 in
1,000,000).
2.2.1.4 Atmospheric Dispersion Modeling
With an estimate of the time-averaged emission rate of each COPC, atmospheric dispersion
models may be used to estimate the exposure point ambient air concentrations at actual
receptors or at theoretical receptors when evaluating future land-use scenarios. Atmospheric
dispersion models may be generally divided into screening-level and refined models. Screening-
level models require a minimum of site-specific input data. The results of screening-level
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Emissions from Closed or Abandoned Facilities
models, however, exhibit a relatively high degree of uncertainty. These types of models
evaluate transport and dispersion of pollutants in a conservative manner relying on "worst-case"
estimates of air concentrations. Refined dispersion models, however, are constructed to better
represent simulations of actual air dispersion events for site-specific conditions.
2.2.1.4.1 Screening-Level Dispersion Modeling
Screening-level dispersion models can be used in a first-tier evaluation of risk or for an
evaluation of compliance with air pathway ARARs. In such evaluations, exposure point
concentrations are generated that represent worst-case dispersion conditions producing the
highest air concentrations and thus the most health protective exposure assessments. Tier I
exposure assessment dispersion modeling consists of simplified calculation procedures designed
with sufficient health protective to allow a determination of whether an emission source (1) is
clearly not an air quality threat or (2) poses a potential threat that should be examined with more
sophisticated estimation techniques. Screening-level models provide short-term maximum air
concentration estimates. These short-term estimates can be converted to long-term (e.g., annual)
maximum air concentration estimates that can be used to characterize lifetime cancer and
chronic noncancer health risks. In addition, the screening-level estimates can be converted to
the averaging time appropriate to most air pathway air concentration ARARs (e.g., 8 h, 24 h,
etc.) using EPA recommended conversion factors.
The EPA SCREENS computer program is a commonly used screening-level dispersion
model. The program is a PC-based software application that uses a steady-state Gaussian plume
model and is distributed through the EPA's Support Center for Regulatory Air Models
(SCRAM) website at http://www.epa.gov/scram001/dispersion_screening.htm (accessed August
2005). As of this writing, the version of the program dated (96043) is the current version of
SCREENS and is available as a stand-alone program. A user's guide for SCREENS can also
be downloaded from the SCRAM website.
The SCREENS model is written as an interactive program that can be executed by typing
"SCREENS" at the command prompt from any directory that contains the SCREEN3.EXE
executable file or by clicking on the SCREEN3.EXE icon in Windows. The program then
prompts the user for input data on the site or emission source to be modeled. Once all required
data are input, the model will estimate the maximum 1-h average air concentration at the user-
specified receptors. SCREENS can estimate air concentrations for four different types of
emission sources: (1) "point sources," or stacks; (2) "area sources," or emission sources that
consist of homogeneously distributed emissions at the surface of a two-dimensional area; (3)
"volume sources," or fugitive emissions from buildings or roof monitors; and (4) "flares" such
as open, candlestick flares. SCREENS can estimate air concentrations from only one emission
source for each modeling run. If multiple sources must be modeled, a separate run must be
made for each source and the air concentrations added together to determine the combined air
concentration at the receptor of interest.
The SCREENS model estimates the maximum 1-h average air concentration based on
worst-case meteorology. That is to say, the program will search through a predefined number
of wind directions and atmospheric stability classes to find the combination that generates the
maximum air concentration at the specified distance from the source. For area sources,
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Guidance for Evaluating Landfill Gas
SCREENS also provides an option for specifying the wind direction with respect to the long
axis of a rectangular emission source. This option may be used to estimate the air concentration
at a particular receptor location relative to the area. Descriptions of the atmospheric stability
classes and meteorological data used for screening estimates can be found in U.S. EPA, 1992a.
The emission rate and other site-specific data, must be entered into the model. Two options
are available. The first is to enter the actual emission rate in units of mass rate per unit area
(grams per square meter second) for area sources, and mass rate (grams per second) for point
sources and flares. This means that a separate modeling run will be necessary for each pollutant
of interest. The second emission input option is to enter a unity emission rate (i.e., 1 g/m2-s or
1 g/s). SCREENS will generate a normalized air concentration (e.g., milligram per cubic meter
for each gram per second, or milligram per cubic meter for each gram per square meter second)
at the receptor. The normalized air concentration is also referred to as a "dispersion coefficient".
The advantage to this approach is that only one modeling run is required for a given emission
source. The actual air concentration of each pollutant of interest is then obtained as the product
of the dispersion coefficient and the actual emission rate.
Dispersing Area Emission Sources
LFG emissions from the surface of a landfill can be considered "area" emission sources. If
the emission rate of the pollutant of interest is homogeneously distributed across the areal extent
of the landfill, only one modeling run is required. If surface emissions are significantly hetero-
geneous, however, multiple model runs may be necessary. Appendix C presents the statistical
procedures that may be used to determine if the landfill areas are homogeneously distributed.
Figure 2-5 illustrates the surface of a generic landfill where the variability in the estimated
emissions of benzene is considerable. This spatial distribution may be due to the distribution
of benzene in the LFG, the varying ages of different landfill cells, or both. The areal extent of
the landfill has, therefore, been divided into three different parcels of land based on the dif-
ferent estimated emission rates. In this case, the emission rate of benzene from each parcel must
be dispersed using a separate SCREENS run. Inputs for each model run include the dimensions
Receptor
Figure 2-5. Example of Milti-Parcel Area
Emission Source.
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Emissions from Closed or Abandoned Facilities
of the parcel, the distance from the center of the parcel to the receptor, and a unity emission rate
of 1 g/m2-s. This results in three dispersion coefficients (normalized air concentrations) as can
be seen in Table 2-2. Each dispersion coefficient is multiplied by the actual parcel-specific
emission rate of benzene to yield the actual 1-h average air concentration at the receptor. The
combined 1-h average air concentration is then the sum of the values from all three parcels.
Table 2-2. Example of SCREENS Results for Multi-Parcel Emission Source.
_. . „ ff. . , Benzene Actual Air
„ , Dispersion Coefficient „ . . „ , „ , , .
Parcel , , 3 / 2 \ Emission Rate Concentration
(mg/m per g/m -s) , , 2 ^ /• / ^
v s F s ' (g/m2-s) (mg/m3)
A 1.626xl06 1.950xlO-6
B 3.317xl07 1.065xlQ-7
C 3.404xl07 1.320xlO-8
Total
Total x 0.08
3.17
3.53
4.49
11.19
0.90
It should be understood that adding the air concentrations from the emission sources
depicted in Figure 2-5 does not necessarily represent actual dispersion conditions. This is
because the concentration from each source is computed assuming the worst-case wind
direction for that source, and this worst-case wind direction may not be the same for all sources;
there cannot be three different simultaneous wind directions. Useing the technique, however,
is considered to be health protective and can be applied to screening-level situations where the
estimated combined concentration at the receptor is used to rule-out the possibility of excessive
risks or to demonstrate that a particular air pathway ARAR can not be exceeded. For risk
evaluation purposes, the combined 1 h average air concentration must be converted to an annual
average. This is done by multiplying the combined 1-h average air concentration by the annual
conversion factor of 0.08 from Table 2-3. If, in addition, a State air toxics regulation specifies
that an acceptable air concentration of benzene at the receptor must be based on a 24-h
averaging time, compliance with the ARAR can be determined by multiplying the combined
1-h average air concentration by the 24-h conversion factor of 0.4 from Table 2-3.
Table 2-3. Averaging Time Conversion Factors.3
Averaging Time Multiplying Factor
3 hours 0.9 (±0.1)
8 hours 0.7 (± 0.2)
24 hours 0.4 (± 0.2)
Annual 0.08 (± 0.2)
a Source U.S. EPA, 1992a
In addition to the specified receptor location given in the example above, the SCREENS
model can also automatically generate the location of and the associated air concentration at the
point of maximum plume impact. For area sources, this location may be on or offsite. Further,
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Guidance for Evaluating Landfill Gas
SCREENS can generate air concentrations based not only on user-specified distances, but also
on an automated distance array between a user-specified minimum and maximum distance. For
example, Figure 2-6 shows a sample SCREENS model output for a square area emission source
with equal side lengths of 284.49 meters. In this case, the automated distance array generated
air concentrations at 142 through 1,000 m. In addition, the model searched for the distance from
the center of the square source to the point of maximum air concentration. For this example, the
point of maximum concentration is at 202 m from the center of the source, and the concentra-
tion is 62.72 mg/m3.
Figure 2-6. Example of SCREENS Model Output File
*** SCREENS MODEL RUN ***
*** VERSION DATED 96043 ***
Small Typical Superfund Landfill
SIMPLE TERRAIN INPUTS:
SOURCE TYPE = AREA
EMISSION RATE (G/(S-M**2)) = .391800E-06
SOURCE HEIGHT (M) = .0000
LENGTH OF LARGER SIDE (M) = 284.4900
LENGTH OF SMALLER SIDE (M) = 284.4900
RECEPTOR HEIGHT (M) = .0000
URBAN/RURAL OPTION = RURAL
THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED.
THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED.
MODEL ESTIMATES DIRECTION TO MAX CONCENTRATION
BUOY. FLUX = .000 M**4/S**3; MOM. FLUX = .000 M**4/S**2.
*** FULL METEOROLOGY ***
*** SCREEN AUTOMATED DISTANCES ***
*** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES ***
DIST
(M)
142.
200.
300.
400.
500.
600.
700.
800.
900.
1000.
CONC
(UG/M**3)
60.22
62.64
24.65
18.05
14.54
12.27
10.68
9.505
8.608
7.893
U10M
STAB (M/S)
6
6
6
6
6
6
6
6
6
6
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
USTK
(M/S)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
MIXHT PLUME MAXDIR
(M) HT (M) (DEC)
10000.0
10000.0
10000.0
10000.0
10000.0
10000.0
10000.0
10000.0
10000.0
10000.0
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
45.
45.
45.
45.
45.
45.
45.
45.
45.
45.
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Emissions from Closed or Abandoned Facilities
MAXIMUM 1-HR CONCENTRATION AT OR BEYOND 142. M:
202. 62.72 6 1.0 1.0 10000.0 .00 45.
*** SUMMARY OF SCREEN MODEL RESULTS ***
CALCULATION MAXCONC DISTTO TERRAIN
PROCEDURE (UG/M**3) MAX(M) HT (M)
SIMPLE TERRAIN 62.72 202.
Dispersing Point Emission Sources and Flares
"Point" sources are those that emit pollutants through a stack or vent. Examples of point
sources include passive LFG vents and gas treatment systems such as enclosed flares and
leachate air strippers. Flares, on the other hand, emit pollutants directly to ambient air and not
through a stack. The user should note that there are several differences in SCREENS input data
requirements between point sources (e.g., enclosed flares) and flare sources (e.g., open flares).
Input requirements include:
(1) Point or flare source release height in meters.
(2) Stack inside diameter in meters for point sources. For flare sources, an effective inside
diameter is calculated by the program from other parameters.
(3) For point sources, stack gas exit velocity in meters per second or stack flow rate in
either cubic meters per second or cubic feet per minute. The program defaults to
accepting a gas exit velocity, but a flow rate can be entered by preceding the value with
either "VM=" (for cubic meters per second) or "VF=" (for cubic feet per minute). For
flare sources, SCREENS assumes an effective gas exit velocity of 20 m/s.
(4) Ambient temperature in Kelvin (K = °C + 273). If the ambient temperature is unknown,
enter 293 K, which corresponds to 20 °C. No ambient temperature input is required for
flare sources; the model assumes an ambient temperature of 293 K.
(5) Total heat release in calories per second (cal/s) for flare sources. The heat release is
calculated as shown in Equation 2-9. Total heat release is not a point source input.
1 8.57 x 106 cal
HR = MF X — X = 2-9
31,536,000 s/yr m3
where:
HR = Heat release rate in calories per second and
MF = CH4 flow rate from LandGEM or source test in cubic meters per year.
Two input options (complex terrain and building downwash) are also provided in the
SCREENS program for both point and flare sources but are not available for area sources. The
complex terrain option is used to estimate impacts for cases where terrain elevations exceed
stack height. The building downwash option accounts for the effect of structures near a source
or upon which a point or flare source stands. In most cases, neither of these options will be
needed for landfill dispersion modeling.
As with area sources, one SCREENS model run can be performed for each point source or
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Guidance for Evaluating Landfill Gas
flare with a unity emission rate of 1 g/s to generate a series of dispersion coefficients at the
receptors of interest. The actual 1-h average air concentration is calculated as the product of the
dispersion coefficient and the actual stack emission rate determined by stack sampling. In the
case of open flares, the combustion gases are not enclosed, thereby making stack sampling
impossible. Controlled emissions of individual LFG constituents are typically estimated based
on a theoretical destruction removal efficiency (e.g., 98%). Additional information on control
efficiency can be found in AP-42 Table 2.4-3. For a more complete discussion of the input
requirements to the SCREENS program or guidance on use of the options mentioned here, users
should consult U.S. EPA, 1995a.
2.2.1.4.2 Refined Atmospheric Dispersion Models
A Tier II exposure assessment of landfill emissions may be desired if the results of a Tier
I analysis have been used to characterize health risks that are found to exceed a level of con-
cern such as the maximum predicted lifetime cancer risk or the maximum predicted chronic
noncancer hazard index. A Tier II assessment involves the use of site-specific source and
facility layouts as well as meteorological information. Tier II analysis of a landfill is performed
to provide the most scientifically-refined indication of the impacts of emissions. Dispersion
modeling for the Tier II analysis procedure is based on EPA's Industrial Source Complex,
Version 3 (ISC3) model. The ISC3 model and user's guide can be found on the EPA SCRAM
website.
The ISC3 model consists of two parts, a long-term version (ISCLT3) and a short-term
version (ISCST3). The long-term version is used for annual concentration estimates, such as
the dispersion coefficients required for risk characterization. The ISC3ST version can also be
used for annual concentration estimates and is considered to be the ISC3 version-of-choice for
most dispersion modelers. Unlike SCREENS, which has worst-case meteorological data built-
in, ISC3 requires the user to provide local-specific meteorological data. ISCLT3 uses annual
meteorological data based on joint frequency distributions of wind speed, wind direction, and
atmospheric stability category, known as STAR (Stability Array) summaries. The ISC3ST
model uses sequential hourly meteorological data. Both types of meteorological data are
available from the National Climatic Data Center in Asheville, North Carolina. Sequential
hourly data that have been quality assured are available for many National Weather Service
stations across the United States from the SCRAM website.
ISC3 Input Requirements
There are two basic types of inputs that are needed to run the ISC3 models. They are (1) the
input run stream file, and (2) the meteorological data file. The run stream setup file contains the
selected modeling options as well as source location and parameter data, receptor locations,
meteorological data file specifications, and output options. As with Tier I exposure assessments,
the emission rate can be the actual emission rate or a unity emission rate used to generate
dispersion coefficients (normalized air concentrations).
Unlike SCREENS, ISC3 can model multiple sources and source types simultaneously,
allowing area and point sources (there is no flare option in ISC3) to be combined in the same
model run. The allowance for multiple sources in the model provides for more realistic
representations of non-rectangular landfills than does SCREENS. By division into smaller
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Emissions from Closed or Abandoned Facilities
rectangular parts, each of which appears as a separate source in the run stream file, a landfill
that is not adequately represented by a simple rectangle can be more realistically modeled. The
screening technique described in Section 2.2.1.4.1 of this document uses the SCREENS model
to estimate combined air concentrations from more than one emission source. The combined
air concentration, however, does not accurately represent actual dispersion conditions but,
rather, represents a worst-case scenario. Use of the ISC3 model more accurately describes the
combined-source type of source-receptor geometry. In addition, the screening technique
estimates long-term (e.g., annual) averages based on a theoretical correction factor applied to
a worst-case 1-h average concentration. The ISC3 model uses actual site-specific meteorologi-
cal data to disperse contaminants over the user-specified averaging time.
Rather than using an assumed automated distance array as in SCREENS, ISC3 provides
several options for positioning receptors. Individual receptors can be located at discrete
locations, or grids of receptors can be generated by the model in the user's choice of either
rectangular or polar coordinates. Multiple discrete receptors and receptor grids can all be
combined as desired by the user. Users should be aware that large numbers of receptors can lead
to long model run times.
ISC3 Input Data
Input source parameters for area and point sources in the ISC3 run stream file are similar
to those required by SCREENS but also include the physical location. Area source parameters
are (U.S. EPA, 1995b)
(1) Area emission rate in g/m2-s; this can be calculated from a unit emission rate, such as
1 Mg/year divided by the area;
(2) Release height above ground in meters; usually zero (0.0 m) is used to model ground-
level releases from a landfill;
(3) Area source geometry and orientation (see the ISC3 user's guide).
Input parameters required for point sources are
(1) Point emission rate in g/s. This can be a unit emission rate such as 1 g/s;
(2) Release height above ground in meters (i.e., the stack height);
(3) Point source orientation (see the ISC3 user's guide);
(4) Stack gas exit temperature in Kelvins;
(5) Stack gas exit velocity in meters per second;
(6) Stack inside diameter in meters;
Both the run stream and meteorological input files are described in detail in U.S. EPA,
1995b. All run stream file options and formats are fully described in the user's guide, which
should be consulted before attempting to develop a run stream file to model a landfill.
A third type of input may also be used by the models when implementing the dry deposition
and depletion algorithm feature. Use of this feature may be necessary if an analysis of multi-
media risks or ecological impacts of landfill emissions is desired. A complete description of this
option and its use is available in the user's guide.
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Guidance for Evaluating Landfill Gas
ISC3 Output Data
Output from the ISC3 model is placed in a text file, the name of which is specified by the
user on the command line when starting a modeling run. The output file contains a copy of the
input run stream file, model setup messages (including any errors or warnings detected by the
model), a summary of the inputs, the model results, and the model execution messages.
Model results can be presented as a tabular summary of the overall maximum modeled air
concentrations (or dispersion coefficients for a unit emission rate input) as well as by receptor.
The user can also choose from tables of results for individual sources, for groups of sources, and
for the contribution of each source within a user-defined group. Selecting the optional source
contribution table for inclusion in the output file is recommended for determining the exposure
from each source in cases where there are multiple emission sources. As described in Section
2.2.1.4.1 and illustrated in Table 2-2, the contribution table for each area, or parcel, of the
landfill can be generated using a unit emission rate of 1 g/m2-s for each parcel. The contri-
bution table will give the dispersion coefficient for each parcel at the receptor of interest based
on the unity emission rate. The actual air concentration at the receptor as contributed by each
parcel is then the product of the actual emission rate and the dispersion coefficient. The total
air concentration from all parcels is then the sum of the parcel-specific actual air con-
centrations.
In addition to the tabular result options that produce tables in the output file, there is an
option to create a separate output file that can be used to plot the results. The resulting file
contains the x and y coordinates for each receptor location as well as the long-term (usually
annual) average dispersion coefficient value at each receptor. This file can be used with a
graphics package (e.g., SURFER, GNUPLOT) to generate contour plots. Many such programs
are available, although the file may need to be edited (e.g., removing the header information)
in order to produce plots. These output options are also discussed more completely in the ISC3
user's guide.
2.2.2 Determining Ambient Air Impacts by Air Monitoring/Sampling
A major concern at SFL sites is the potential exposure via the air pathway of residents and
workers in the areas surrounding the landfill. The degree of concern varies from site-to-site
depending on the emissions of LFG COPCs. The exposure of offsite receptors typically is
evaluated at several steps in the Superfund process, and both modeling and monitoring
approaches may be employed as part of an exposure assessment.
2.2.2.1 Field Monitoring and Whole air Sampling
Within this section, the term "monitoring" refers to real- or near real-time assessment of air
concentrations using portable instruments. The term "sampling" refers to whole air sampling
techniques requiring laboratory analytical methods. This section deals exclusively with
monitoring and sampling methods designed to estimate air concentrations for offsite receptors.
Air monitoring for remedial site workers is covered under the site health and safety plan and
is subject to the air standards of the Occupational Safety and Health Administration (OSHA).
This type of air monitoring is not included in this document. Appendix A of this document
contains detailed information on monitoring, sampling, and analytical methods for determining
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Emissions from Closed or Abandoned Facilities
the ambient air concentrations of target analytes including LFG COPCs.
The evaluation of inhalation exposure using a monitoring or sampling approach generally
involves measuring the concentrations of target analytes at the point of exposure or facility
boundary of the site for ground-level emission sources such as LFG emissions from the landfill
cover or passive LFG vents. In the case of elevated emission sources (e.g., stacks), sampling
is typically conducted at the areas of maximum expected impacts as determined by preliminary
dispersion modeling. The screening-level dispersion modeling techniques given in Section
2.2.1.4.1 of this document can be used to first determine whether emissions of individual
COPCs represent a possible threat to human health. If so, refined dispersion modeling de-
scribed in Section 2.2.1.4.2 can assist in determining the locations of the areas of expected
maximum air concentrations as an aide in placing air sampling stations.
For ground-level emission sources, a fixed network of samplers is typically located around
the perimeter of the site. The number of sampling locations will depend on the size of the site,
among other factors. For large sites surrounded by nearby residences or businesses, a 12-station
network may be used to provide nearly complete coverage of the fence line (i.e., a station every
30 degrees as illustrated in Appendix A). In some cases, only samples from stations located
directly upwind or downwind of the site for a given sampling period will be analyzed to save
time and money; samples collected perpendicular to the emission plume are not analyzed.
Alternatively, a smaller number of movable stations may be used that may be placed daily
according to predicted wind patterns. If the predictions are wrong, however, the sampling
stations may not be within the emission plume as needed.
In general, compliance with long-term action levels (ARARs and/or risk-based air
concentrations) is based on daily samples collected at each location. In lieu of daily sampling,
every sixth-day sampling is often employed. Broad-based collection methods such as specially
treated canisters (EPAMethod TO-15), or solid sorbent sampling (i.e., Carbotrap 300, charcoal,
Tenax, etc.), are usually selected for VOCs so that all the target analytes can be measured using
only one or two sampling and analysis approaches. Alternatively, dedicated gas chromatographs
(GCs) or gas chromatographs/mass spectrometers (GC/MSs) can be used as point samplers, or
open path monitors (OPMs) may be used in some cases to provide near real-time data and to
minimize unit analytical costs. Fewer options exist for particulate matter, metals, and some
semi-volatiles (SVOCs), although standard methods are available (see Appendix A).
2.2.2.2 Radial Plume Mapping
One of these alternative methods involves a technique developed through research funded
by EPA's National Risk Management Research Laboratory (NRMRL), which uses ground-
based optical remote sensing technology, known as radial plume mapping. The radial plume
mapping technique is performed with an optical remote sensing sensor such as an open path
Fourier transform infrared (OP-FTIR) spectrometer, open-path tunable diode laser absorption
spectroscopy (OP-TDLAS), or ultraviolet differential optical absorption spectroscopy
(UV-DOAS). The light energy is transmitted from an optical remote sensors (ORS) to a
retroreflector (mirror) target, which is usually set up at a range of 100 to 500 meters. The
returned light signal is received by the single telescope and directed to a detector. The light is
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Guidance for Evaluating Landfill Gas
absorbed by the molecules in the beam path as the light propagates to the mirror and again as
the light is reflected back to the analyzer.
A promising monitoring approach is the use of OP-FTIR. These monitors are spectrographic
instruments configured to monitor the open air over extended paths of hundreds of meters or
more. They rely on the interaction of light with matter to obtain data on the species present and
their associated air concentrations. The potential advantages of OP-FTIR include near real-
time air concentrations, no requirement for sample collection, no additional analytical costs
(i.e., laboratory costs), and concentrations that are path-averaged values instead of concentra-
tions at specific sampling points. Disadvantages include the lack of standard operating
procedures (SOPs), spectral interferences (e.g., water vapor), the lack of reference spectra for
some compounds of interest, and detection limits for some compounds that are higher than
those of conventional sampling methods (EPA, 1993a). However, recent advances, including
the development of standard operating procedures, facility manual, and EPA test methods for
use of ORS, has resulted in wider usage and acceptance of this technology.
Recent innovations include the development of ORS method to obtain path-configured
optical paths. The multipollutant concentration data along with wind vector information are
processed using an integrating algorithm to yield a mass emission flux for the source. The
acquisition of path integrated concentration data can be accomplished with several types of
optical remote sensing instruments. The differences between instruments is the spectral range
used, the type of detector, and the algorithm used to interpret the data. The OP-FTIR method-
ology is capable of identifying approximately 100 of 189 hazardous air pollutants regulated
under the Clean Air Act.
The horizontal radial plume mapping (HRPM) approach provides spatial information to
path-integrated measurements acquired in a horizontal plane by an ORS system. This technique
yields information on the two-dimensional distribution of the concentrations in the form of
chemical-concentration contour maps. This form of output readily identifies chemical "hot
spots," the location of high emissions. This method can be of great benefit for performing site
surveys before, during, and after site remediation activities.
HRPM surveys are usually performed with the ORS beams located as close to the ground
as is practical. This enhances the ability to detect minor constituents emitted from the ground,
since the emitted plumes dilute significantly at higher elevations. The survey area is typically
divided into a Cartesian grid of n times m rectangular cells. In some unique cases, the survey
area may not be rectangular due to obstructions, and the shape of the cells may be slightly
altered accordingly. A mirror is located in each of these cells, and the ORS sensor scans to each
of these mirrors, dwelling on each for a set measurement time (usually 30 seconds). The system
scans to the mirrors in the order of either increasing or decreasing azimuth angle. The path-
integrated concentrations measured at each mirror are averaged over several scanning cycles
to produce time-averaged concentration maps. Meteorological measurements are made
concurrent to the scanning measurements.
The vertical radial plume mapping (VRPM) method maps the concentrations in the vertical
plane by scanning the ORS system in a vertical plane downwind from an area source. One can
2-26
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Emissions from Closed or Abandoned Facilities
obtain the plane-integrated concentration from the reconstructed concentration maps. The flux
is calculated by multiplying the plane-integrated concentration by the wind speed component
perpendicular to the vertical plane. Thus, the VRPM method leads to a direct measurement-
based determination of the upwind source emission rate.
The ORS combined with the radial plume mapping method can be used for both fence-line
monitoring applications, and real-time, on-site, remediation monitoring and source characteriza-
tion. An infrared light beam, modulated by a Michelson interferometer is transmitted from a
single telescope to a retroreflector (mirror) target, which is usually set up at a range of 100 to
500 meters. The returned light signal is received by the single telescope and directed to a
detector. The light is absorbed by the molecules in the beam path as the light propagates to the
retroreflector and again as the light is reflected back to the analyzer. Thus, the round-trip path
of the light doubles the chemical absorption signal. One advantage of ORS monitoring is that
the concentrations of a multitude of infrared absorbing gaseous chemicals can be detected and
measured simultaneously with high temporal resolution.
The chemical vapor, emitted from an emission source, forms a plume that is carried by the
wind across the multiple infrared beams. The ORS concentration measurements can be used
with wind data to calculate the emission rate applying the RPM method for vertical planes. The
beam measurements avoid the uncertainties that are inherent in the traditional point
measurements. Meteorological and survey measurements are also made. A theodolite is used
to make the survey measurement of the azimuth and elevation angles and the radial distances
to the retroreflectors, relative to the ORS.
2.2.2.3 Analytical Detection Limits
One of the most important issues relative to ambient monitoring is analytical detection
limits. As pointed out in U.S EPA 1992a, however, current measurement techniques, in some
cases, do not achieve detection limits low enough to ensure that no significant health risks
exist. For example, the following list provides ambient concentrations (at 25 °C) associated
with a 1-in-l,000,000 cancer risk for several LFG constituents using EPA standard residential
exposure assumptions and toxicity factors from Integrated Risk Information System (IRIS),
National Center for Environmental Assessment (NCEA), or Health Effects Assessment
Summary Tables (HEAST) as applicable.
LFG Constituent
Benzene
Carbon tetrachloride
Chloroform
Perchloroethylene
Trichloroethylene
Vinyl chloride
1 , 1 -Dichloroethylene
Concentration (ppbv)
at ID'6 Risk
0.10
0.03
0.02
0.62
0.27
0.22
0.01
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Guidance for Evaluating Landfill Gas
Because modern analytical methods (e.g., TO-15) can achieve detection limits down to 2.0
to 0.5 ppbv, nearly all of the carcinogens listed above would not be detected at levels associated
with a 1-in-l,000,000 cancer risk. Risk management decisions for compounds that may exist
below the analytical detector limits are not discussed in this guidance.
In addition to the issue of analytical detection limits, methods used to collect samples can
also provide a false sense of security. Careful attention is needed during the development of an
ambient air monitoring or sampling plan to ensure proper placement of equipment (e.g., upwind
and downwind sample collection) and appropriate timing of sample collection. U.S. EPA
(1993a) provides guidance on many aspects of ambient air monitoring and sampling at
Superfund sites.
As mentioned previously, the COPCs in LFG emissions are typically associated with
chronic (long-term) exposure risks. Exceptions arise during active remediation (e.g., drum
removal, contaminated soil excavation), when high short-term exposures can occur. In most
cases, however, an ambient air sampling program should be designed to characterize long-term
concentrations downwind of the site. The frequency of sample collection depends on (U.S.
EPA, 1993 a)
• The temporal variability in emission rates (for LFG emissions there can be significant
temporal variability in emission rates of individual constituents),
• The variability of meteorological and other factors that affect pollutant dispersion,
• The level of confidence needed for determining mean or maximum downwind
concentrations, and
• The level of available funding.
EPA Method TO-15 is the method most commonly employed to assess the presence and
concentrations of toxic volatile constituents in LFG emissions. This method, along with a great
deal of information on other ambient air sampling and analytical methods, can be found at
http://www.epa.gov/ttn/amtic/airtox.html (accessed August 2005), which is EPA's Ambient
Monitoring Technology Information Center Web site. Appendix A of this document provides
information on ambient air monitoring, sampling, and analytical methods for site-specific
conditions. Appendix B of this document includes a generic QAPP that may be used to develop
the site-specific QAPP. Appendix C presents the Wilcoxon Statistical Procedures used to
identify the number of near homogeneous areas within the study area.
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Emissions from Closed or Abandoned Facilities
3. Assessing Subsurface Vapor Migration
Subsurface vapor migration of LFG is a function of several site-specific factors including
pressure and diffusion gradients, subsurface lithology and soil stratigraphy, and the presence
or absence of high permanent groundwater that tends to block subsurface vapor flow. Offsite
subsurface vapor migration is directly proportional to the pressure and diffusion gradients that
exist between the waste perimeter and the location of interest. Vapor transport follows Darcy' s
law for vapor flow through a porous medium as a function of the pressure gradients. In addition,
molecular diffusion through the air-filled soil pores must also be considered, especially for
older landfills that have limited methane generation potentials. If LFG migration occurs, CH4
and landfill gas COPCs can enter into buildings due to pressure-driven flow and diffusion.
Intrusion of subsurface vapors into indoor air can also occur from contaminated ground-
water that has migrated offsite. In addition to the generation of leachate, LFG can contaminate
the underlying aquifer by dissolution. Due to the multi-directional flow of LFG, groundwater
up gradient of the landfill may be contaminated. If contaminated groundwater migrates offsite
and under buildings, a combination of diffusion and convection can cause vapor-phase con-
taminants to enter buildings through cracks, gaps, and openings in the building foundation.
Subsurface geology is extremely important in assessing vapor migration. Soil strata that
exhibit relatively high vapor permeability (e.g., sands) may act as advection conduits offering
relatively low resistance to LFG flow. In addition, preferential vapor pathways such as karst
lithology, subsurface utility conduits, and even subterranean animal burrows and vegetative root
pathways offer very little resistance to vapor flow in the soil vadose (unsaturated) zone. At
several sites, methane has been found at different depths below ground surface under offsite
structures, suggesting that the LFG is moving laterally within several different soil strata. Once
the vertical soil permeability is greater than the lateral permeability, the LFG may surface to
ambient air or be drawn into buildings by a combination of diffusion and advection as a result
of a pressure gradient between the soil column and an under pressurized building interior. Soil
surface conditions also play an important role in subsurface vapor transport. Lateral vapor
migration is often at a maximum when the soil surface is frozen or paved. Under such
conditions, the lateral permeability of the soil is considerably higher than the vertical
permeability at the soil surface.
Subsurface vapor migration of LFG may result in two outcomes that must be addressed: (1)
high concentrations of methane pose safety hazards due to the possibility of explosions within
offsite or onsite structures, and (2) elevated concentrations of the toxic constituents of the LFG
3-1
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Guidance for Evaluating Landfill Gas
may constitute health hazards within structures.
Methane is combustible in air when enough oxygen is present to support combustion, and
the CH4 vapor concentration is between the LEL of approximately 5 percent by volume and the
UEL of approximately 15 percent by volume. Subsurface vapor migration of LFG can result in
these conditions within structures resulting in explosions. Even if the methane concentration
within the building is not explosive, the COPCs within the LFG can be present at concentrations
that exceed the target risk level and/or the target hazard index.
Figure 3-1 shows a general flow diagram for assessing the potential impacts from sub-
surface vapor migration of landfill gas. These procedures begin with a determination of whether
subsurface CH4 exists at the landfill property boundary. The presence of CH4 acts as a predictor
of whether other toxic LFG constituents may be present in offsite and onsite structures. If
methane is detected in perimeter subsurface soils or in onsite buildings, regulatory requirements
may be triggered pursuant to 40 CFR §258. In addition, indoor air sampling may be required
to establish indoor concentrations of CH4 and toxic COPCs. Soil gas sampling may also be used
along with modeling to estimate the indoor concentrations of LFG COPCs. Appendix A
contains sampling and analytical procedures for estimating indoor, outdoor, and soil gas
concentrations.
End Subsurface
AdVection Analysis
-'
Determine
Methane Cones, to
Depth cf Waste at
Landfill FYoperty
Boun dary and
Within Onsite
Structures
. .
{ Start J
Intercept Methane
Migration and/or
Perform Indoor
Air Remediation
v Setup Periodic
j Methane
I Monitoring
* Program
NO
..^MethanexYES ^
Detected / Xv
Setup Periodic Methane
Receptor Site
[wo
^ YES /Tarad Kisk\ ^
^v Exceed ed ? ^^
4 NO
f ~~~ :'• HC
S\ IvUhWV Determine Location .-'''' Meth
Cone. >2SK of \, NQ d Methane Vapor •"' Plume R
LEL In Shmrfurai or > J-^=» P|ume Leading Otfsite Bu
LELtfPrupertf/ E(Jge '"xFutureLc
>, Boundary S •., r
\. jf ' ' Xs*
_fc i
s X%it
one "^x
cached ^^
dings or ^*
nd-use^X'
s? X'
ffS
Comply With Op^^\ \0p^2
Requ irements ^ 1 -^ ^ ™ ^
d4QCff. ( Perforrn }
Sect. 258.23 IndoorAir
End Subsurface
AaVection Analysis 1
V J
\
T
Perf'jrm Risk
Calculations
f Perform Soil ^
Gas Sampling at
Building(s) and/or
Future Land-use
^ ^ J
i
i
i
i
i
Estimate Indoor 1
Air Cones. Using 1
EFA Soil Vapor
Intrusion Model 1
$TOP
Figure 3-1. Flow Chart for Assessing Subsurface Vapor Migration by Convection.
3-2
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Emissions from Closed or Abandoned Facilities
3.1 Screening-Level Vapor Migration Modeling
Both screening-level and simulation models exist for estimating the subsurface vapor
migration of LFG to offsite receptors. The simulation models, however, are academic algo-
rithms with limited availability and require a great deal of input data. The screening -level
model of Little et al. (1992) is a steady-state model for estimating the indoor air concentration
of volatile species within a structure located a given distance from the perimeter of the landfill
wastes. It should be noted that this model does not account for preferential vapor pathways but
operates under the assumption of Darcian steady-state vapor flow through a porous medium
(i.e., soils). Themodel also operates under the assumption that advective vapor transport occurs
only in the lateral direction and that the soil surface acts as an impenetrable layer. This tends
to overestimate the vapor concentration reaching the building of interest. Nonetheless, this
model may be used to make an order-of-magnitude estimate of the indoor air concentration. The
effects of possible preferential pathways must also be considered using monitoring techniques
described in later sections of this document.
From Little et al. (1992), the attenuation coefficient (a) that expresses the ratio of the indoor
air concentration to the vapor concentration at the landfill perimeter is calculated by
where:
a = Attenuation coefficient (unitless);
kv = Soil vapor permeability in centimeters squared;
ju!fg = LFG dynamic viscosity in grams per centimeter-second (1.15* 10"04);
P source = Subsurface LFG pressure at the boundary in grams per centimeter-second
squared;
P0 = Subsurface pressure at the building in grams per centimeter-second squared
(0);
AB = Area of building below grade in square centimeters;
Qbldg = Building ventilation rate in cubic centimeters per second; and
L = Depth to contamination below building in centimeters.
The soil vapor permeability (kv) can be estimated as the soil intrinsic permeability. The
intrinsic permeability is a property of the soil alone that varies with the size and shape of
connected soil pores; it does not consider the reduced permeability due to soil moisture. The
soil vapor permeability or intrinsic permeability can be estimated by
Ir K^
kv = - 3-2
where:
kv = Soil vapor (intrinsic) permeability in centimeters squared;
Ks = Soil saturated hydraulic conductivity in centimeters per second;
juw = Dynamic viscosity of water (0.01307 g/cm-s at 10 °C);
3-3
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Guidance for Evaluating Landfill Gas
pw = Density of water in grams per cubic centimeter (0.999 g/cm3)
g = Acceleration due to gravity (980.665 cm/s2).
The value of Ks can be measured for the soil between the landfill perimeter and the building
using in situ techniques. The value of Ks can also be approximated from the class average
values of the Soil Conservation Service (SCS) soil textural classifications shown in Table 3-1
from Schaap and Leij (1998). Please note that the units of the saturated hydraulic conductivities
in Table 3-1 are cm/h.
Table 3-1. Class Average Values of Soil Saturated Hydraulic Conductivity.
Soil Textural
Classification, USDA
Sand
Loamy sand
Sandy loam
Sandy clay loam
Sandy clay
Loam
Clay loam
Silt loam
Clay
Silty clay loam
Silt
Silty clay
Class Average Satu-
rated Hydraulic
Conductivity
(cm/h)
26.78
4.38
1.60
0.55
0.47
0.50
0.34
0.76
0.61
0.46
1.82
0.40
The soil textural classifications in Table 3-1 can be determined from the SCS classification
chart shown in Figure 3-2. The percent sand, silt, and clay can be estimated from site-specific
boring logs or can be determined with more confidence using either the American Society for
Testing and Materials (ASTM) Standard Test Method for Particle-Size Analysis of Soils (D422-
63) or by using the analytical procedures found in the U.S. Natural Resources Conservation
Service (NRCS) Soil Survey Laboratory Methods Manual, Soil Survey Laboratory Investiga-
tions Report No. 42. If Equation 3-1 is used to estimate indoor air concentrations, the soil vapor
permeability (kv) is a key parameter for convective vapor transport. Therefore, if the soil
saturated hydraulic conductivity is estimated using the SCS soil textural classification, use of
the correct classification is important. Multiple soil borings should be taken between the landfill
property boundary and the building of interest to establish the soil classifications for each
stratum from the soil surface to the depth of the landfill.
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Emissions from Closed or Abandoned Facilities
100
Sandy Cloy Loam
Figure 3-2. U.S. Soil Conservation Service Classification Chart Showing
Composition Centroids (solid circles).
For buildings with basements, the value of AB includes the floor area and wall area below
grade. For residential structures with basements, the default value ofAB is 1,000,000 cm2 from
EQ (2004). This value can be used or site-specific values can be substituted. From EQ (2004),
the average building ventilation rate (Qbldg) for a single-family detached residence in the United
States is 56,335 cm3/s. The average building ventilation rate for commercial or industrial
buildings is typically higher than that of residential structures. The building ventilation rate is
the product of the building volume and the air exchange rate. For commercial/industrial
buildings, the air exchange rate may range from approximately 0.25 to 2.0 exchanges per hour.
ASTM E 1739-95 indicates that commercial/industrial enclosed-space air exchange rate of
0.00023 s"1 (0.929 hr"1) is typical. A default value of 1.0 air exchange rate per hour is the value
listed in the California Environmental Protection Agency's "Guidance for the Evaluation and
Mitigation of Subsurface Vapor Intrusion to Indoor Air" for commercial buildings.
The value of the subsurface landfill gas pressure at the landfill boundary (Psource) should be
measured at the property boundary in native soils to avoid the possibility of penetrating
drummed wastes with the probe. This is usually accomplished using a cluster well of soil vapor
probes at different depths (see Figure 3-3). These wells are normally used for subsurface
methane monitoring. Each probe should be positioned in a different subsurface soil stratum.
Special attention should be given to pressures measured in high permeability strata such as
sands. Installation specifications for pressure probes can be found in EPA Reference Method
2E in Appendix A of 40 CFR 60.
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Guidance for Evaluating Landfill Gas
SAMPLING PORT
1C--O- DEPTH
WELL HEAD (FLUSH UTILITY VAULT)
PROBE TAG
a. PROBE NO
b. DEPTH
c. SCREEN LENGTH
BAGKFILL MATERIAL
(3/8' PEA GRAVEL)
1/3 DEPTH
2/3 DEPTH*
FULL DEPTH
BOTTOM OF LANDFILL
WELL BORE SEAL
(1-2 FT OF HYDRATED
BENTOMITE)
SLOT PERFORATIONS
(1/BP MACHINE S-OT
OR .25 INCHHOLE'i
CASING MATERIAL
CPVC TYPICAL)
CASING DIAMET=R{O.S"-2- TYP.)
Figure 3-3. Example of a Multi-Depth Cluster Well.
With an estimate of the attenuation coefficient (a), the indoor air concentration at the
building of interest is calculated by
where:
Ch,, = a x C,
Cbld = Steady-state indoor air concentration in micrograms per cubic meter,
3-3
•-bldg
a = Attenuation coefficient (unitless)
C source = Vapor concentration measured at landfill boundary in micrograms per cubic
meter.
It should be stressed that use of the Little et al. (1992) model does not account for
preferential vapor pathways and that the model operates under the assumptions that the LFG
vapor front has reached the building and that steady-state conditions have been achieved.
Preferential vapor pathways can be assessed by performing methane sampling using portable
detectors under or within structures and within any suspected vapor transport conduits (e.g.,
underground utilities, sewers, etc.). However, direct measurements indoors and under the slab
may be preferred.
3-6
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Emissions from Closed or Abandoned Facilities
3.2 Determining the Extent of Methane Migration
RCRA Subpart C of Part 258 requires monitoring of subsurface CH4 concentrations at the
landfill property boundary and within onsite structures. If CH4 concentrations are greater than
25 percent of the LEL (1.25% by volume) within onsite buildings, or subsurface concentrations
are greater than the LEL (5 percent by volume) at the property boundaries, installation of a gas
migration control system is required.
Perimeter subsurface monitoring wells are the most commonly used method for monitoring
subsurface CH4 concentrations. Although the number of wells is not specified in the Part 258
rules, the number of wells and well spacing is determined on a site-specific basis. Please note
that State or local rules may specify a minimum number of wells and well spacing. Probes
should be placed at the landfill property line within native soils and should be placed between
and not immediately opposite any LFG extraction wells. LFG monitoring systems should be
designed by professional engineers and certified geologists. Migration monitoring probes may
be of single or multi-depth design. Single depth probes can be used with prior knowledge of the
depth at which methane is migrating. Without such knowledge, multi-depth probes are used and
typically grouped together in a cluster well design. Figure 3-3 shows a typical cluster well. Gas
samples can be taken from each sampling port at the top of each probe to provide methane as
well as NMOC and COPC concentrations at depth. If whole air samples are taken for COPC
concentrations, extreme care must be taken to avoid sample dilution from ambient air
infiltration. This includes use of a leak-tight seal at the sampling port and leak-tight fittings in
the sampling equipment.
The deepest multi-depth sampling probes are typically installed to the depth of the refuse
around the perimeter of the landfill. A separate probe should be installed to the center of each
permeable geologic layer. CH4 concentrations can be determined using portable instruments
such as a flame ionization detector (FID) as discussed in Appendix A. Although the FID will
ionize and detect most NMOCs as well as CH4, the relatively small NMOC concentration can
be included in the CH4 concentration without unacceptable errors (i.e., CH4 concentrations are
in the percent range while NMOC concentrations are in the parts-per-million range). A photo
ionization detector (PID) can not be used to measure CH4 concentrations because the detector
is insensitive to CH4.
If the CH4 concentrations are greater than the LEL within any onsite structure or if the
subsurface methane concentrations at any depth are greater than 25 percent of the LEL at the
property boundary, the mitigation requirements of 40 CFRPart 258 are applicable. If subsurface
CH4 is detected at the property boundary, further analysis is required regardless of the con-
centration. Once CH4 is discovered in native soils at the landfill property line, an analysis
should be performed to discover the location of the subsurface CH4 vapor front. This can be
performed by drilling additional vapor monitoring wells between the landfill property line and
any offsite structures (including any hypothetical future land use sites). In addition, monitoring
for CH4 can be performed using portable instruments for any suspected preferential vapor
pathways. These might include sewers, utility conduits (e.g., water lines and meters), or any
other subterranean pathways. If CH4 is discovered near or beneath any offsite buildings, the
two options discussed below are available for estimating possible indoor air concentrations.
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Guidance for Evaluating Landfill Gas
3.2.1 Indoor Air Sampling
Indoor air sampling within a structure can be performed for both CH4 and COPCs. Great
care must be exercised whenever entry to a confined space is needed to complete the subslab
or indoor air sampling exercise. Unfortunately, ventilation to reduce gas concentrations to levels
below the LEL contradict the effort to determine the indoor and subslab concentrations. CH4
sampling can be performed using portable instruments. If CH4 is discovered in indoor air,
sampling for COPCs should be considered even if the CH4 concentrations are below the LEL.
Indoor air sampling for COPCs may be performed using several methods including whole air
sampling (e.g., specially treated canisters) and passive sampling using solid sorbents. The
reader is referred to U.S. EPA, 1992b) for a more detailed discussion of indoor air sampling.
In addition, Appendix A of this document discusses the various sampling and analytical
techniques used for indoor air sampling.
Special Note:
The objective of indoor air sampling is to determine the incremental risks only from LFG
contaminants caused by subsurface vapor intrusion. This can be complicated by interferences
from contaminated or ambient air, and from offgasing of household chemicals and building
products. For example, plywood can offgas formaldehyde and carpets can offgas a series of
chemicals. The objective of indoor sampling is to determine only the incremental risks from the
LFG contaminants. Indoor air sampling can be combined with outdoor air sampling and limited
soil gas sampling to reduce the uncertainty in the indoor sampling results. For example, if a
particular contaminant is found in indoor air, in soil gas beneath the building, but not in outdoor
air, more confidence can be placed in an assumption that all or part of the indoor concentration
is due to vapor intrusion. When performing indoor air sampling, a well formulated sampling plan
is critical. Finally, 10"6 risk-based indoor air concentrations for some COPCs are in the low parts-
per-billion range. These concentrations can approach the analytical method detection limits for
some compounds such as vinyl chloride, and 1,1-dichloroethylene. Analytical results for these
types of contaminants may be flagged by the laboratory as estimated values. The analyst must
therefore keep in mind the inherent uncertainty in these values.
3.2.2 Soil Gas Sampling Under Buildings
The second option for determining indoor air concentrations of LFG COPCs is to perform
soil gas sampling beneath buildings. Once an average soil gas concentration of each COPC has
been determined, the subsurface vapor intrusion model of Johnson and Ettinger (1991) may be
used to estimate indoor air concentrations. This technique has the advantage of avoiding the
complicating factors inherent in indoor air sampling but exhibits a higher degree of uncertainty
in the results.
Soil gas sampling can be performed using either whole air sampling techniques or solid
sorbent sampling. Whole air sampling typically involves collecting the soil gas sample in
specially treated canisters for subsequent analysis of volatile species by EPA Method TO-15.
Passive sorbent sampling involves the burial of sorbent cartridges at a known depth below grade
for an extended time period (typically 72 to 120 hours). Once the sorbent cartridges are
retrieved, they are sent to the laboratory for thermal desorption and analysis (e.g., a modified
TO-1 analysis for volatiles).
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Emissions from Closed or Abandoned Facilities
Whole air sampling typically employs the use of an evacuated specially treated canister
connected to a flow controller and subsequently connected to the sampling probe. The sampling
probe is first purged of at least two volumes of air using a special fitting and a purge pump.
Flow is then stopped to allow the soil pore air to re-equilibrate over a given time period. This
allows time for the vapor concentration in the soil pores to re-establish equilibrium conditions.
Actual sampling then begins at a sampling rate low enough to prevent ambient air from
infiltrating the sample. For shallow soil gas sampling, air may flow down the annulus of the
probe if the sampling rate is too high and the seal at the ground surface is not air-tight. An
airtight seal may be achieved if one uses modeling clay or expansive alcohol laced foam. Air
infiltration will act to dilute the sample. Once a sufficient sample volume has been extracted,
the canister is shipped to the laboratory for analysis. It should be stressed that soil gas
concentrations may vary considerably over relatively small distances given the heterogeneity
of the soil. If sampling is used to estimate soil gas concentrations beneath a building floor, the
sampling probes should be inserted through holes drilled in the basement slab. Alternatively,
angle borings can be made to insert the probe under the building from outside the footprint of
the building floor in contact with the soil.
Passive sampling using solid sorbents can also be used to estimate average soil gas
concentrations. The concentration term is normally a calculated value based on the cross-
sectional area of the sorbent cartridge, the molecular diffusion rate of the contaminant in air,
the total mass of each contaminant collected, the sampling duration, and an empirical adsorption
rate constant for the sorbent. Recent EPA technology verification reports produced by the EPA
National Exposure Research Laboratory (U.S. EPA 1998a, 1998b) concluded, at least for one
proprietary sorbent cartridge, that the comparability of the reported vapor-phase concentrations
between whole air sampling techniques and solid sorbent sampling is not linear. That is to say
that comparability was favorable at low parts per billion by volume ranges, but solid sorbent
cartridge concentrations increased by only marginal amounts as the whole air sampling
concentrations increased by up to two orders-of-magnitude. Nonetheless, the use of passive
solid sorbent sampling offers a relatively uncomplicated method for detecting at least which
contaminants are present is soil gas.
Whether the average soil gas concentration directly beneath the building floor in contact
with the soil is determined by whole air or solid sorbent sampling, a rough approximation of
the steady-state indoor air concentration in the building (Cbldg) can be estimated by
L-in = 7 A
bids 100Q 3-4
where Csource is the soil gas concentration measured directly below the building floor and 1,000
is the attenuation coefficient for a source adj acent to the building (API, 1998). A more rigorous
estimate of the indoor air concentration can also be made from the procedures of Johnson and
Ettinger (EQ, 2004) by
/
r< _ r< "s°" I 3.5
^-bldg ~ ^source} /n '
3-9
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Guidance for Evaluating Landfill Gas
where:
Cbidg = Steady-state indoor air concentration in micrograms per cubic meter,
Csource = Soil gas concentration measured directly beneath the building floor in contact
with the soil in micrograms per cubic meter,
Qsoii = Volumetric flow rate of soil gas entering the building in cubic centimeters per
second,
Qhldg = Building ventilation rate in cubic centimeters per second,
and
(2soil ~
where:
AP = Pressure differential between soil surface and the enclosed space in grams
per centimeter-second squared,
Xcrack = Floor-wall seam perimeter in centimeters,
// = Viscosity of air in grams per centimeter-second,
^crack = Crack depth below grade in centimeters, and
rcrack = Equivalent crack radius in centimeters.
For single-family detached residences, the default value of AP is 40 g/cm-s2 from EQ
(2004). The value of kv is calculated from Equation 3-2. The value of Xcrack is calculated as two
times the floor length plus two times the width of the floor in contact with the soil. The default
value of Xcrack for residential construction is 3,844 cm from EQ (2004). The value of// is
1.75xlO~04 g/cm-s, and the value of Zcrack is the depth below grade to the top of the floor in
contact with the soil. The default value of Zcrack for basement construction is 200 cm from EQ
(2000). The value of the equivalent crack radius (rcrack) is calculated by
rcrack
B I X crack)
where:
rcrack = Equivalent crack radius (cm)
77 = Acracl/AB, (0< 77*1)
AB = Area of floor and walls below grade (cm2)
Xcrack = Floor-wall seam perimeter (cm).
The term Acrack is the total area of a 0. 1cm crack that runs the perimeter of the basement
floor, and^4B is the area of the floor and walls below grade. The default values ofAcrack and^4B
for a single-family detached residence with a basement are 384 cm2 and 1,692,321 cm2,
respectively from EQ (2004).
3.3 Mitigation Strategies for Subsurface Vapor Migration
Whether an indoor air concentration of each LFG COPC is determined by indoor air
sampling or by a combination of soil gas sampling and modeling, a risk evaluation is performed
5-10
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Emissions from Closed or Abandoned Facilities
to determine the aggregate cancer risk and the hazard index for chronic exposure to non-
carcinogens. If the target cancer risk or the target hazard index is exceeded, mitigation of the
LFG vapor migration should be undertaken. Methods for managing subsurface migration
involve collecting the LFG to an extent that minimizes the lateral pressures driving the gas
through the subsurface. Section 5.1 discusses both passive and active collection systems.
Two objectives exist for reducing LFG migration: (1) minimizing safety hazards associated
with high methane concentrations, and (2) reducing health hazards associated with LFG toxics.
Different approaches to collecting LFG can be taken depending on whether one or both of these
objectives is to be met. If reducing CH4 concentrations in offsite soils is the only objective,
either passive or active collection systems have merit. Passive systems such as horizontal
trenches or a series of vertical wells have been employed at many sites to reduce offsite soil
CH4 concentrations to acceptable levels (e.g., less than 25 percent of the LEL).
If the objective is to reduce concentrations of LFG toxics, active collection systems are
recommended using the design criteria specified in the CAANSPS/EG. During the research for
this guidance, several instances were found where passive systems were used to prevent
subsurface migration and had failed to reduce toxics concentrations to below levels of concern.
Active systems were subsequently used to reduce the concentrations of toxics in the offsite
soils.
The LEL for CH4 is 5 percent by volume, and the UEL is 15 percent by volume. This means
that within the 5 to 15 percent range, potential exists for landfill fires or explosions. Whether
or not a fire or explosion will occur depends on the availability of oxygen and an ignition
source. Figure 3-4 is a graph showing the relationship between CH4 and O2 where flammable
mixtures can occur.
0 5 10 15 20
Oxygen (%)
Figure 3-4. Flammability of Methane/Oxygen Mixtures (adapted
from U.S. EPA, 1999b, Appendix E).
25
5-11
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Guidance for Evaluating Landfill Gas
As shown in Figure 3-4, flammable mixtures of CH4 and O2 exist when methane is within
its explosive limits (5 to!5 percent) andO2is at approximately 12 to 13 percent or more. There
is also the potential for an explosion when CH4 builds up above its LEL in confined spaces. At
landfills, these confined spaces can be buildings, well head vaults, or other structures.
Underground landfill fires generally occur when ambient air is drawn into the landfill. Air
can infiltrate the landfill by two mechanisms: advection and diffusion. Some of the ways
advection can cause air infiltration include excessive vacuum at active gas collection wells,
separations at cover seams caused by deterioration or settlement, gas well and trench lateral
separations, well seal failures, earthen cover cracks due to dessication and general cover
permeation, and by atmospheric (barometric) pressure cycling, which can pump air into the
upper portions of the landfill during low atmospheric pressure events. Most of these infiltration
mechanisms can be overcome with proper operation and maintenance. Excessive vacuum at
active gas collection wells, however, may be more difficult to correct. Gas control systems such
as an enclosed flare operate most effectively when the methane concentration is greater than 25
percent. Aggressive collection minimizes emissions to ambient air but may encourage air
infiltration, especially at active gas collection system well seals, and thus dilute the LFG
methane concentration. Typical well seals are made of hydrated bentonite, but dessication of
the bentonite from prolonged periods of little or no precipitation can cause seal failures such
that ambient air is drawn into the upper most regions of the landfill wastes. Prolonged seal
failures can result in oxygen contents increasing within deep sections of the landfill. In addition,
general diffusion of ambient air through permeable cover materials can introduce oxygen into
the wastes, especially for older landfills with minimal methane generation potentials. Diffusion
through the cover material may be most apparent for arid regions of the country where the air-
filled porosity of the cover is higher.
Oxygen content of a landfill increases as air enters it, inhibiting anaerobic decomposition.
This can result in an aerobic decomposition zone that is usually near the landfill surface. This
aerobic zone promotes composting that can generate a considerable amount of heat. This heat,
in combination with enough O2 to support combustion and a local dilution of the CH4 con-
centration below the UEL, can cause spontaneous combustion and a resulting CH4 explosion
or fire.
Where subsurface migration is found to be a problem, horizontal barrier trenches or vertical
extraction wells should be installed at the site perimeter. Horizontal barrier trenches are often
installed to intercept LFG migrating offsite in the subsurface. These are typically constructed
by excavating a perimeter trench to at least the depth of the waste (deepest waste within a
certain distance from the trench). A barrier material (e.g., heavy thickness plastic sheeting) is
placed on the outer wall of the trench. A horizontal collector pipe is laid between gas con-
ducting materials within the trench (e.g., 1 to 7 cm gravel). Vertical risers are installed at
various lengths of the horizontal collector pipe to convey the gas to vents at the surface or to
a control device. Collection may be passive or supplemented by gas moving equipment.
These trench barrier systems have generally been reliable at reducing CH4 migration (e.g.,
to levels below 25 percent of the LEL). Their record, however, in reducing the migration of
LFG toxics to below the levels of concern is spotty. Instances have been noted where toxics
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Emissions from Closed or Abandoned Facilities
(e.g., vinyl chloride) have continued to migrate at significant levels following installation of
barrier trenches. Presumably, the migration pathway was either under or around the trench.
Hence, a soil gas monitoring program should be used to verify the performance of the barrier
trench (or perimeter wells, if these were the selected approach).
Figure 3-5 is a photograph of an abandoned horizontal trench system. The vertical risers are
connected to a horizontal pipe that, at one time, directed the gas to a vent at the top of the
landfill. Figure 3-6 shows an alternative migration barrier system. In this system, a series of
vertical wells are connected and routed to a series of carbon drums and an elevated vent stack.
It should be noted that activated carbon is not effective in removing many of the important toxic
LFG constituents such as vinyl chloride (see Section 5.3).
Figure 3-5. Abandoned Horizontal Barrier Trench System.
Figure 3-6. Alternative Migration Barrier System.
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Guidance for Evaluating Landfill Gas
Air infiltration is caused when too much vacuum is applied to the system or when wells are
poorly sealed, causing ambient air to be pulled into the landfill and potentially explosive or
flammable conditions. The operational standards for the NSPS/EG call for maintaining a LFG
temperature less than 55 °C (130 °F) and either a N2 level less than 20 percent by volume or an
O2 level less than 5 percent by volume. The owner or operator may establish a higher temp-
erature, N2, or O2 value at a particular well; however, there must be data demonstrating that the
elevated parameter(s) does not cause fires or significantly inhibit anaerobic decomposition of
the waste (40 CFR §60.753).
The collection system must be operated to maintain surface concentrations below 500
ppmv methane. The NSPS/EG do not specify how to measure compliance with the requirement
to minimize subsurface migration. The upper limit for CH4 concentration in offsite soils is
generally set at less than 25 percent of the LEL (1.25 percent by volume). For safety reasons,
the CH4 content in onsite soils should be kept below the LEL (5% by volume).
For collection systems constructed to achieve compliance with theNSPS/EG, the collection
and control system must be operated until the following conditions have been met (§60.752):
• The landfill is no longer accepting wastes, is permanently closed as per the requirements
of §258.60, and has submitted a closure report as required in §60.757(d);
• The collection and control system has been operated for a minimum of 15 years;
• As specified in §60.754(b), the calculated NMOC emission rate is less than 50 Mg/yr
on three successive test dates (test dates no less than 90 days and no more than 180 days
apart).
Alternatively, an active collection and control system may be installed to achieve
compliance with another ARAR (e.g., ambient air limits or health risk standards). Similar
criteria can be applied for removal of the equipment as specified in the NSPS/EG. After at least
15 years of operation, a risk evaluation and an evaluation of compliance with ARARs can be
performed with LFG test data to determine compliance with the ARAR and to determine that
the target cancer risk and/or hazard index is not exceeded.
If CH4 migration interception methods are not successful, a supplemental strategy of indoor
air remediation can be implemented to reduce CH4 and COPC concentrations within affected
buildings. Site experience has shown that the building remediation techniques typically used
for radon intrusion can be successfully applied to landfill gas intrusion. The EPA document
titled Options for Developing and Evaluating Mitigation Strategies for Indoor Air Impacts at
CERCLA Sites (U.S. EPA, 1993b) contains a complete review of indoor air mitigation
techniques. Additionally, several excellent documents on this subject are available from the
U. S. Department of Energy Lawrence Berkeley National Laboratory (LBL). These documents
may be downloaded to a PC from the Indoor Environment Department of the LBL at
http://eetd.lbl.gov/ied/ied.html (accessed August 2005). The Indoor Air Quality Division of the
EPA Office of Air and Radiation also publishes documents concerning indoor air remediation.
In particular, EPA 1993c, titled Radon Mitigation Standards (EPA-402/R-93/078, revised April
1994). is available at http://www.epa.gov/iaq/radon/pubs/mitstds.html (accessed August 2005).
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Emissions from Closed or Abandoned Facilities
3.4 Indoor Vapor Intrusion from Contaminated Groundwater
As mentioned at the beginning of this chapter, the production of leachate and the migration
of LFG can contaminate the underlying aquifer. If contaminated groundwater migrates offsite,
vapor volatilizing from the top of the water table can migrate up and into buildings. In this
situation, vapor transport is a function of both diffusion and advection. Figure 3-7 shows a flow
chart for assessment of human exposure to this pathway. The assessment begins with a deter-
mination as to whether contaminated groundwater has migrated underneath offsite buildings.
If so, modeling is first performed to estimate the indoor air concentrations originating from each
groundwater contaminant. The estimated indoor air concentrations are then used in a risk
evaluation to determine whether the aggregate target cancer risk or the target hazard index is
exceeded. If this first-tier analysis indicates unacceptable risks, either soil gas measurements
and modeling, or indoor air sampling is undertaken to refine the indoor air concentration
estimates.
Contaminate
Groundwater Below
Building(s) or Future
nd-use Sites?
End Vapor Intrusion
from Groundwater
Analysis
Perform Risk
Calculations
Estimate Indoor
Air Cones. Using
EPA Soil Vapor
Intrusion Model
Perform Soil
Gas
Sampling at
Receptor Sile(s)
Use Existing Data
to Determine Soil
Stratigraphy and
Properties at
Receptor Site(s)
Use Soil Boringsto
Determine Soil
Stratigraphy and
Properties at
Receptor Site (si
- SCS soil classes
- Soil dry bulk densities
- Soil water-filled porosities
- Soil organic carbon contents
YES-
T /\
( Perform 1 /TsTargef\
W Indoor Air \"^< Risk "^>
^ Sampling J ^foce e d e
-------
Guidance for Evaluating Landfill Gas
where:
Csource = Vapor concentration at the air-water interface in micrograms per cubic
meter,
H xra = Henry' s law constant at the groundwater temperature (dimensionless), and
Cw = concentration of the VOC of interest in groundwater in micrograms per
cubic meter.
These vapors will then diffuse upward toward the soil surface until they enter into a pressure
field created within the soil column surrounding the building. This pressure field is created by
a pressure gradient between the atmospheric pressure and the under-pressurized building
interior. The under-pressurization is caused by wind effects on the building and by stack effects
from building heating and mechanical ventilation. Under most circumstances, the pressure field
extends perhaps one to two meters below the building floor in contact with the soil depending
on the interior dynamic pressure and the soil vapor permeability. Once the diffusing vapors
reach the subsurface pressure field, they are drawn into the building by advection through
cracks or openings in the building foundation. Figure 3-8 illustrates the diffusion and advection
processes that result in indoor vapor intrusion from contaminated groundwater.
Stack Effect
Figure 3-8. Indoor Vapor Intrusion from Groundwater.
Recent experience at a site in Denver, Colorado, has shown that this pathway of inhalation
exposure is credible and can account for incremental cancer risks as high as approximately 1
in 10,000 even when the depth to the water table is significant (10 to 15 feet). In addition, the
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Emissions from Closed or Abandoned Facilities
2001 Supplemental Guidance of Superfund Soil Screening Levels includes this exposure
pathway when estimating risk-based soil screening levels (SSLs).
Johnson and Ettinger (1991) developed a screening-level model for estimating the indoor
air concentrations of vapor-phase contaminants emanating from contamination in underlying
soils or below the top of the water table. The EPA Superfund program has developed a series
of spreadsheet models based on the work of Johnson and Ettinger. These spreadsheets and an
accompanying user's guide are available from the Superfund risk assessment web site at
http://www.epa.gov/oswer/riskassessment/airmodel/iohnson_ettinger.htm (accessed August
2005).
Two of these spreadsheet models deal directly with vapor intrusion from contaminated
groundwater. Both models theoretically partition the groundwater contaminants into aqueous
and vapor-phases based on Henry's law. That is to say that the models assume that the ground-
water concentration is less than the solubility limit in water—i.e., Nonaqueous Phase Liquids
(NAPL) is not considered. The GW-SCREEN model provides a first-tier estimate of indoor air
concentrations and risks based on steady-state conditions. Within this model, only the most
sensitive model parameters can be user-defined, all other input parameters are set to default
values for detached single-family residences. The GW-ADV model provides a more refined
estimate of the indoor air concentration and associated risks based on user-specified data for
all input parameters. The user's guide to these models should be consulted for specific model
features, assumptions, and limitations.
In addition, the SG-SCREEN and SG-ADV models are also available for estimating indoor
air concentrations and associated risks from measured soil gas concentrations below or adj acent
to buildings.
In the case of groundwater contamination due to NAPL, the GW-SCREEN or GW-ADV
models can be used by assuming that the groundwater concentrations at the first air-
groundwater interface are at the aqueous solubility limit. This approach will produce source
vapor concentration values (Csource) approaching the single component saturated vapor concen-
tration based on Raoult's law for residual-phase contaminants (NAPL). If sampling data are
available for component concentrations of light nonaqueous-phase liquids (LNAPL) that tend
to float on the top of the water table, the mole fraction of each component can be determined.
In such cases, a better estimate of the source vapor concentration can be made by multiplying
the calculated mole fraction of each component by its aqueous solubility limit and using the
resulting product as the initial groundwater concentration in either of the groundwater vapor
intrusion models.
The models referred to above require soil properties data from the soil surface to the depth
of the water table or to the soil gas sampling depth, as appropriate. These properties include soil
dry bulk densities, soil moisture contents, and the SCS soil textural classifications. With these
data, the models will estimate the steady-state indoor air concentration directly above the
contaminated groundwater as well as the associated incremental risks.
If this first-tier evaluation results in an exceedence of the target risk level, two options are
3-17
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Guidance for Evaluating Landfill Gas
available for making a more refined estimate of the indoor air concentrations. As described in
Sections 3.2.1 and 3.2.2, indoor air sampling or a combination of soil gas sampling beneath the
building(s) of interest and modeling can be used to estimate indoor air concentrations for a
second-tier estimate of the associated risks. If the second-tier evaluation results in unacceptable
risks from indoor inhalation of vapor-phase groundwater contaminants, indoor remediation
techniques referred to in the previous section of this document should be considered.
5-18
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Emissions from Closed or Abandoned Facilities
4. Air Pathway ARARs
Under CERCLA Section 121, remedies selected at Superfund sites must protect human
health and the environment and must comply with ARARs. Remedial actions taken under
CERCLA Sections 104, 106, or 122 that are conducted entirely on site do not require Federal,
State, or local permits, whether conducted by EPA, another Federal agency, a State, or a
responsible party. On-site remedies must comply with substantive requirements of ARARs but
need not comply with the administrative and procedural requirements. On-site remedial
activities covered by the permit exemption include any activity occurring on site prior to the
response action itself (e.g., activities during the remedial investigation/feasibility study). "On-
site" is defined as the areal extent of contamination and all suitable areas in close proximity to
the contamination necessary for implementation of the response action. Although CERCLA
Section 121(e) exempts facility owners/operators from having to obtain permits for on-site
remedial activities, the substantive requirements and conditions that would otherwise be
included in the permit must be met. The reason for the permit exemption is to preserve
flexibility and avoid lengthy, time-consuming procedures when developing and implementing
remedial alternatives (U.S. EPA, 1989).
Air pollution problems at Superfund co-disposal landfills are usually the result of emissions
of gas or particulate matter (e.g., dusts). Such emissions may be released through a stack, vent,
or some other functionally equivalent opening. Emissions that could not reasonably pass
through such openings are considered to be "fugitive" emissions. Gaseous emissions may be
due to the venting of LFG, vaporization of liquids, thermal destruction of LFG, or chemical and
biological reactions with solid and liquid wastes. Emissions of particulate matter are likely to
be caused by construction, maintenance and inspection traffic, and wind blown surface
materials.
The following activities and events, commonly performed during CERCLA remediation of
SFLs, may be sources of air emissions:
• LFG emissions through permeable cover materials,
• LFG emissions through passive vents,
• Emissions from LFG control systems (e.g., flares, internal combustion engines, and
turbines),
• Leachate processing equipment (e.g., air strippers and evaporators),
• Waste excavation and handling,
• Construction activities and traffic on unpaved roads, and
• Wind erosion of soils.
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Guidance for Evaluating Landfill Gas
4.1 CAAARARs
Except for extraordinary circumstances, Federal air pathway ARARs under the CAA for
SFLs are limited to the EG for municipal solid waste landfills. In specific cases where the SFL
is part of an active MSW landfill, the NSPS and other Federal air pathway requirements may
constitute ARARs. In such cases, the RPM/OSC should work closely with the EPA Regional
Air Programs Office to determine which additional Federal requirements may be ARARs.
The NSPS and EG promulgated under „,-... f ,,„„„ ,,,-„ , .,
_ . ,,, ,, . „ , ^. . . , Definition of an MSWLandfill under the
Section 111 (b) of the CAA are in place to mps mdEG_ m ^ disposalfacility in
control emissions of NMOCs from MSW a contiguous geographical space where
landfills (see the text box to the right for the
definition of an MSW landfill under the
NSPS/EG). Under the NSPS and EG, NMOC
is used as a surrogate measure of VOCs, a
tropospheric ozone precursor. Promulgated
EG under Part 60 are not enforceable; the EG
only stipulate the requirements for an approv-
.. A A . . A . , , „ . roads. An MSW landfill may be publicly or
able state implementation plan under Section . ', , . ,reT/I-,, ,f;; ,
r r privately owned. An MS W landfill may be a
household waste is placed in or on land. An
MSW landfill may also receive other types of
RCRA Subtitle D wastes such as commercial
solid waste, nonhazardous sludge,
conditionally exempt small quantity generator
waste, and industrial solid waste. Portions of
an MSW landfill may be separated by access
new MSW landfill, an existing MSW landfill,
or a lateral expansion (40CFR §60.30c).
11 l(d) of the CAA. To be enforceable, the EG
requirements must be contained in either a
Federal or approved State plan codified under
40 CFR Part 62. For States without an EPA
approved 111 (d) landfill plan, the promulgated November 8,1999 Federal plan (64 FR 60689),
40 CFR Part 62, Subpart GGG, is applicable and stipulates enforceable requirements for
affected landfills. The reader should consult the Federal Register for the latest versions of the
NSPS (40 CFR Part 60 Subpart WWW) and the EG (40 CFR Part 60, Subpart Cc) and the Code
of Federal Regulation, 40 CFR Part 62.
For most new landfills, the EPA has delegated the NSPS regulatory authority to the States.
For existing landfills, the States are required to implement the EG requirements through a State
Section lll(d) plan approved by EPA. As an alternative, States may request and receive
delegation of the Federal plan. Approved State Section lll(d) landfill plans, including EPA
Federal plan delegations, are listed in 40 CFR Part 62. An exception could be a State or Federal
plan that was promulgated after the last July 1 publication date of the Code of Federal
Regulations.
As shown in the definition, SFLs are potentially subject to the NSPS/EG because they often
contain household wastes. Whether the NSPS or EG apply to an MSW landfill is determined
by two factors: age and size of the landfill. The NSPS apply to new landfill sites, while the EG
apply to existing landfills. "New" landfills are considered to be those sites that began
construction, modification, or reconstruction on or after May 30, 1991. "Existing" landfills are
those that accepted waste on or after November 8, 1987, but have not been constructed,
modified, or reconstructed since May 30, 1991.
Landfills that are new or have been modified or reconstructed must comply with the NSPS.
A modified landfill is one that is permitted to increase volumetric capacity typically by
4-2
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Emissions from Closed or Abandoned Facilities
horizontal expansion. Remedial actions such as those performed under CERCLA, RCRA, or
State actions are not considered to be construction, modification, or reconstruction and do not,
in and of themselves, subject a landfill to the NSPS (EPA, 1999b). Hence, for SFLs, EG appli-
cability is more likely to be the issue requiring assessment. However, if a portion of the site is
a SFL and there is also a newer and active portion of the site that is subject to the NSPS, the
whole landfill including the SFL is subject to the NSPS.
The NSPS and EG include provisions for a size exemption. Landfills with a design capacity
under 2.5 million Mg or 2.5 million m3 are exempt from the rules. The landfill capacity must
be measured in megagrams or cubic meters, but the owner may request a change in measure-
ment. The landfill design capacity can be taken from the most recent Federal, State, local, or
other official permit used to licence the facility, or it can be calculated. The owner has a choice
of how to report the design capacity. Landfills with a maximum NMOC emission rate under 50
Mg/yr are also exempt from many parts of the rules. Figure 4-1 is a diagram that outlines
applicability issues as they relate to landfill size and construction/ modification history.
Landfill's Size and Construction/Modification History
Outcome
Scenario
Number
May 30,1991
(Proposal Date)
March 12, 1996
(Promulgation Date)
Subject to NSPS or EG?
2 (s^ii^) —
4
5
6
8 (La^?> —
10
11
Modified to
Become Large
Modified to
Become Larger
Modified to
Become Large
Modified to
Become Large
Subject Modified to
toc EGb Become Larger
—
k.
EGb Design Capacity Report Only|
Subject toc NSPSd |
-H Subject toc NSPSf |
-^
-»•
-»>
NSPSd Design Capacity Report Only|
Subject toc NSPS" |
NSPSa Design Capacity Report Only|
Subject toc EGb |
Subject toc NSPS" |
Subject toc NSPS" |
Subject toc NSPSd |
Subject tocNSPSd |
" Small means design capacity less than 2.5 million Mg or 2.5 million m3.
b Landfills that began construction, modification, or reconstruction before May 30,1991, are subject to the EG.
'- "Subject to" means the landfill must submit annual emission reports and must install controls if emissions are
equal to or greater than 50 Mg/yr.
'' Landfills that began construction, modification, or reconstruction on or after May 30,1991, are subject to the NSPS.
* Large means a design capacity equal to or greater than 2.5 million Mg or 2.5 million m3.
Figure 4-1. NSPS Landfill Applicability.
Due to the age of SFLs, they are not likely to be subject to the NSPS (i.e., constructed,
modified, or reconstructed after May 30, 1991). Some sites may be subject to the EG if wastes
were accepted on or after November 8, 1987. Still, most SFLs operated only until the early to
mid-1980's. Regardless of when the site last received wastes, EPA considers the EG to be a
relevant and appropriate requirement if the design capacity cutoff and the NMOC emissions
cutoff have been exceeded. Therefore, the remainder of this discussion will focus on the Section
4-3
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Guidance for Evaluating Landfill Gas
lll(d) plan and requirements for those sites meeting or exceeding the size and NMOC
emissions thresholds described above.
4.1.1 Requirements for the CAA Section 111 (d) Plans and NESHAPS
If the landfill exceeds the size thresholds (greater than 2.5 million Mg or 2.5 million m3),
the owner must quantify NMOC emissions to determine if there is a need to install emission
control equipment. NMOC emissions are calculated using a theoretical first-order CH4 gen-
eration model. This model and methods to estimate emissions are described in detail in Chapter
2. A computerized version of the LFG emissions model (LandGEM) is also available (see
Chapter 2). To a large degree, the LandGEM model is dependent on three variables: a CH4
generation rate constant (&); the refuse CH4 generation potential (Z0); and the NMOC
concentration in the LFG
A flow chart is presented as Figure 4-2
that summarizes the steps to be taken under
the NSPS or EG to determine the need for
LFG collection and control (along with the
CFR citations, where appropriate). There are
three method tiers for estimating NMOC
emissions using the LFG model (40 CFR
§60.754). These methods must be used to
determine whether a landfill is subject to the
collection and control requirements of the
EG. If a SFL is not subject to the EG based
on its closure date (prior to November 8,
1987), the collection and control require-
ments are still considered to be relevant and
appropriate, if the site meets or exceeds the
NMOC emissions threshold of 50 Mg/yr and
the design capacity threshold of 2.5 million
Mg or 2.5 million m3.
Tier I methods rely on the use of default values for all three variables. The NSPS Tier I
default value for & is 0.05 for all parts of the country but can vary depending on annual average
precipitation. Hence a Tier II or III procedure may be beneficial for any facility that triggers
applicability as a result of the default value in the Tier I analysis. Facilities located in dry areas
(average annual rainfall less than or equal to 25 inches) use a rate of 0.02. Facilities located in
wetter areas (average annual rainfall greater than 25 inches) use a value of 0.04. Those facilities
that are predicted by the model to emit 50 Mg/yr of NMOC or more are required to install
emission control equipment (within 30 months of determining the emission rate for the site) or
to recalculate the NMOC emission rate using Tier II or Tier III procedures. If emission rates are
below 50 Mg/yr, the facility is required to periodically recalculate NMOC emissions until such
time that the estimated NMOC emission rate meets or exceeds 50 Mg/yr (EPA, 1999b).
Determining design capacity at Superfund
landfills - Records, such as waste receipts and
solid waste permits needed to estimate design
capacity are often not available for SFLs.
Surveys can provide information on waste depth
and lateral extent to estimate waste volume. For
typical SFLs (i.e., those having closed prior to
the mid-1980's which will have waste that has
undergone settling and degradation), a
reasonable waste density to assume is 1,800
pounds per cubic yard (NSWMA, 1985).
Densities achieved in landfills actively
accepting MSW are reported to vary between
700 and 1,600 pounds per cubic yard (EPA,
1998c). If at all possible, a design capacity
(waste in place) estimate should be confirmed if
any waste acceptance records are available.
4-4
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Emissions from Closed or Abandoned Facilities
Initial Design
Capacity Report
60.757(a)(l)-(2)
Submit Collection
and Control System
Design Plan per
60.752(b)(2) and 60.759
Design Plan Approved
by Implementing Agency
Yes
^^ Is the \^
Design Capacity
>2,5uO,000 Mg
and
\>2.500,000nv-
No Further Action
Necessary Unless
There is an Increase
In Design Capacity
of Landfill
Yes
Recalculate NMOC
Emission Rate
Using TIER 2 NMOC
Concentration
6u.754[a)(3)
Redetenmine NMOC
Concentration per TIER 2
Every 5 Years
Submit TIER 2 Revised
Emission Rate Report
60.757[c)(1)
Recalculate at
Specified Intervals
^-"^ TIER 2
Is the NMOC Emission
-\Rate
No
TIER 3
Determine Site-Specific
Methane Generation Rate
Recalculate NMOC Emission
Rate Using TIER 2 NMOC
Concentration and TIER 3
Methane Generation Rate
6u.754(a)(4)
Redetermlne NMOC
Concentration per TIER 2
Every 5 Years
Submit TIER 3 Revised
Emission Rate Report
60.757(c)(2)
Yes
Recalculate at
Specified Intervals
No
Figure 4-2. Flow Chart for Determining Control Requirements.
4-5
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Guidance for Evaluating Landfill Gas
MSW landfill owners have a second option if NMOC emission rates are greater than or
equal to 50 Mg/yr after using Tier I calculations. The EG provide for a Tier II assessment that
is more accurate and based upon site-specific information using EPA Reference Methods 25C
or 18 to establish the LFGNMOC concentration. These data are then used in the LFG emission
model to calculate the annual NMOC emission rate.
If Tier II procedures show NMOC emissions still greater than or equal to 50 Mg/yr, the
owner may opt for Tier III testing. Using EPA Reference Method 2E (40 CFR 60, Appendix
A), a site-specific CH4 generation rate constant is determined to yield more accurate results. If
Tier III results are greater than or equal to 50 Mg/yr, the owner must install control equipment.
Tier III testing is expensive and, to date, few MSW landfill owners have opted to use this
testing procedure to avoid control requirements.
MSW landfill owners must install equipment that is the best demonstrated technology
(BDT). A passive or active LFG collection system can be used. For compliance with the EG,
a Collection and Control System Design Plan must be prepared and submitted to the respon-
sible agency for review. The Collection and Control Design Plan must show that: (1) the
control equipment will collect LFG at a maximum flow rate for the life of the equipment; (2)
LFG must be collected from all areas of the landfill that have had waste in them for more than
2 years and the area is closed or for more than 5 years if the area is open and still active; (3) the
control equipment can collect gas (for active systems only) at a rate sufficient to keep wellheads
at a negative pressure; and (4) the system must be able to contain subsurface gas migration. The
control equipment (e.g., flare) must achieve an NMOC emission rate of 20 ppmv dry as hexane
at 3 percent O2 or reduce NMOC emissions by 98 percent by weight (U.S. EPA, 1999b). For
open flares, the control device must comply with the design and operating requirements of 40
CFR 60, §60.18.
In order to remove control equipment, the owner must demonstrate compliance with three
conditions: (1) the landfill must be permanently closed as defined under 40 CFR §258.60; (2)
the controls must have been in operation for at least 15 years; and (3) the annual NMOC
emissions rate must be less than the emission rate cutoff taken on three successive dates
between 90 and 180 days apart (U.S. EPA, 1999b).
The requirements for monitoring collection systems include monitoring the landfill surface
to verify that CH4 concentrations are being kept below 500 ppmv. Figure 4-3 is a flow chart of
the surface monitoring requirements under the EG (U.S. EPA, 1999b).
Under Section 112(d) of the CAA, EPA was required to regulate major sources of 188 HAP
listed in Section 112(b) of the CAA. On July 16, 1992 (57 FR 31576), EPA published a list of
industrial source categories, which included MSW landfills, that emit one or more of these
HAP.
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Emissions from Closed or Abandoned Facilities
Visually monitor cover integrity
and repair as needed on a
monthly basis
[§60.755(c)(5)]
Monitor surface methane concentrations along
perimeter and along a pattern that traverses the
landfill at 30-meter intervals (or an approved
site-specific pattern), on a quarterly basis.
[§60.755(c)(l)]
this the third
consecutive auarte
monitoring period with
no exceedance.?
[§60.756(f)]
annual monitoring
Any readings
>. 500 ppm above
background?
In annual
monitoring
cycle?
Mark location(s) and record as monitored
exceedance(s) and perform cover maintenance
or adjust vacuum of adjacent wells and remonltor
locatlon(s) of exceedance(s) within JO days.
[§60.755(c)(4)]
Any readings
>. 500 ppm above
background?
Take additional corrective
action and remonltor locatlon(s)
of exceedance(s) within JO days.
[§60.755(c)(4)]
Any readings
>. 500 ppm above
background?
Remonltor locatlon(s)
of exceedance(s)
one month from
initial exceedance.
[§60.755(c)(4)]
Any readings
>. 500 ppm above
background?
Remonrtor location(s)
of exceedance(s)
one month from
Initial exceedance.
[§60.755(c)(4)]
Any readings
>. 500 ppm above
background?
Install new well or other control
device within 120 davs of
initial exceedance.. An alternative
remedy and timeframe may be
submitted to the Administrator
for approval.
[§60.755(c)(4)]
Figure 4-3. Flow Chart of Surface Monitoring Requirements.
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Guidance for Evaluating Landfill Gas
Under Section 112(k) of the CAA, EPA developed a strategy to control emissions of HAPs
from area sources in urban areas, identifying 33 HAPs that present the greatest threat to public
health in the largest number of urban areas as the result of emissions from area sources.
Municipal solid waste landfills were listed on July 19, 1999, as an area source category to be
regulated pursuant to Section 112(k) because 13 of the listed HAPs are emitted from MSW
landfills (64 FR 3 8706).
On January 16, 2003 EPA published the National Emission Standards for Hazardous Air
Pollutants (NESHAP) for MSW landfills (40 CFR Part 63 Subpart AAAA). The final rule is
applicable to both major and area sources and contains the same requirements as the EG and
NSPS. The final rule adds startup, shutdown, and malfunction (SSM) requirements; adds
operating condition deviations for out-of-bounds monitoring parameters; requires timely control
of bioreactor landfills; and changes the reporting frequency for one type of report.
The final NESHAP rule contains the same requirements as the EG/NSPS (40 CFR Part 60,
Subparts Cc and WWW), plus SSM definition and reporting of deviations for out-of-range
monitoring parameters. Also, the final rule requires compliance reporting every 6 months
whereas the EG/NSPS requires annual reporting. Forbioreactors at large landfills, the NESHAP
rule also requires timely installation of controls, and allows timely removal of controls. The
final NESHAP rule applies to area source landfills if they have a design capacity equal to or
greater than 2.5 million Mg or 2.5 million m3 and have estimated uncontrolled emissions of 50
Mg/yr NMOC or more or if they are operated as a bioreactor. The final rule does not apply to
area source landfills (including bioreactors) with a design capacity less than 2.5 million Mg or
2.5 million m3. It also does not apply to conventional area source landfills that have estimated
uncontrolled emissions of less than 50 Mg/yr NMOC. The EG/NSPS require landfills that meet
the design capacity criteria to periodically calculate uncontrolled annual NMOC emissions. If
an area source landfill that currently has estimated uncontrolled emissions less than 50 Mg/yr
increases to 50 Mg/yr in the future, it will become subject to the NESHAP at that time.
4.2 RCRA Subtitle C Air Pathway ARARs
The RCRA rules that apply to air emissions from hazardous waste treatment, storage, and
disposal facilities (TSDFs) may be ARARs for certain remedial activities. These rules may be
ARARs for circumstances where a liquid hazardous waste stream generated at the point of
origin (such as landfill leachate and LFG condensate) are treated or combusted on-site.
Under the RCRA rules, 40 CFR §261.2(b) states that "Materials are solid waste if they are
abandoned by being: (1) disposed of; or (2) burned or incinerated; or (3) accumulated, stored,
or treated (but not recycled) before or in lieu of being abandoned by being disposed of, burned
or incinerated". Further, a solid waste is defined as a hazardous waste pursuant to §261.4(b) if
it meets the criteria of a "characteristic hazardous waste" described in Subpart C of §261, or a
"listed hazardous waste" described in Subpart D of §261. The EPA Hazardous Waste Number
F039 (listed hazardous waste) is defined as follows:
Leachate (liquids that have percolated through land disposal wastes) resulting/Torn the
disposal of more than one restricted waste classified as hazardous under subpartD of
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Emissions from Closed or Abandoned Facilities
this part. (Leachate resulting from the disposal of one or more of the following EPA
Hazardous Wastes and no other Hazardous Wastes retains its EPA Hazardous Waste
Number(s): F020, F021, F022, F026, F027, and/or F028).
Therefore, if historical records at a specific landfill indicate that more than one EPA listed
hazardous waste was deposited in the landfill, the leachate is considered a listed hazardous
waste under EPA Hazardous Waste Number F039. If it cannot be determined that listed
hazardous wastes were ever deposited in the landfill, a determination must still be made as to
whether the leachate is a "characteristic hazardous waste" as defined in Subpart C of §261. In
addition, it must also be determined whether any landfill gas condensate retrieved from a gas
collection system, although not leachate, is also a characteristic waste under Subpart C of §261.
Subpart C of §261 specifies four tests to be conducted on a solid waste (leachate or
condensate) to determine whether it is a characteristic hazardous waste. These tests are for: (1)
ignitability, (2) corrosivity, (3) reactivity, and (4) toxicity. The corrosivity and toxicity criteria
are the two most likely tests that would decide whether the leachate or condensate is a
characteristic hazardous waste. The test for the toxicity criteria uses the TCLP referenced in
§261.24. Associated with this test is a list of chemical constituents and their associated
threshold maximum concentrations. If an aliquot of the leachate or condensate exhibits one
constituent concentration greater than its associated threshold value, the leachate or condensate
is considered to be a characteristic hazardous waste.
Assuming that the leachate, condensate, or both are characteristic hazardous wastes, treat-
ment of the wastes would be subject to the RCRA air pathway rules. For example, if the LFG
condensate is burned in an enclosed flare, controlled flame combustion of the condensate would
mean that the enclosed flare constitutes an "incinerator" by definition (§260.10). This would
then require that the enclosed flare meet all of the requirements for an incinerator found in 40
CRF Part 264 Subpart O. In addition, this would trigger the requirement to perform an indirect
risk assessment for combustor emissions pursuant to the Omnibus Authority granted under the
Hazardous and Solid Waste Act (HSWA) of 1986.
Pretreatment of landfill leachate considered to be hazardous waste before delivery to any
publicly owned treatment works (POTW) using air strippers or leachate evaporators would be
considered initiation of a new hazardous waste treatment facility. If the treatment units
consisted of air strippers and/or evaporators, as well as storage tanks and associated plumbing,
this would subject the emissions of the system to the requirements of 40 CFR Part 264 Subpart
X for miscellaneous units, Subpart AA for air emission standards for process vents, Subpart BB
for air emission standards for equipment leaks, and Subpart CC for air emission standards for
tanks, surface impoundments, and containers.
If the leachate or condensate is determined to be a characteristic hazardous waste only
because of failing the TCLP, a separate pretreatment system could be installed (e.g., liquid-
phase activated carbon adsorption) to reduce the constituent concentrations below the TCLP
threshold values. If the leachate or condensate then passes the TCLP, further treatment (e.g.,
burning in an enclosed flare) would not be subj ect to the RCRA air emission or treatment rules.
The pretreatment system, however, would still be subject to the applicable TSDF treatment
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Guidance for Evaluating Landfill Gas
standards.
4.3 RCRA Subtitle D Air Pathway ARARs
Pursuant to the requirements of Subpart C of 40 CFR Part 258 (§258.23), owners or
operators of all new and existing municipal solid waste landfills (MSWLFs) must monitor and
control for the possible explosive buildup of CH4 gas within buildings. This is accomplished
by ensuring the following:
(1) The concentration of CH4 gas generated by the facility does not exceed 25 percent of
the lower explosive limit for CH4 in facility structures (excluding gas control or
recovery system components); and
(2) The concentration of CH4 gas does not exceed the LEL for CH4 at the facility property
boundary.
The owners or operators of all MSWLF units must also implement a routine CH4 monitoring
program to ensure that the standards set above are met. The frequency and type of CH4
monitoring system must be based on site-specific soil conditions, hydrogeologic conditions, and
the location of facility structures and the property boundaries.
If CH4 is detected exceeding the levels stated above, immediate action is required to ensure
protection of human health. In addition, the State Director must be notified. Within seven days
of a detection exceeding either of these levels, a record of the CH4 levels detected and a de-
scription of the steps taken to protect human health are to be placed in the landfill operating
records. Within 60 days of such a detection, a remediation plan must be implemented and
placed in the operating records. Further, the State Director must be notified that the plan has
been implemented. The remediation plan must describe the nature and extent of the problem
and the proposed remedy.
The requirements of §258.23 are considered ARARs for all Superfund co-disposal landfills.
Compliance with these ARARs constitutes the impetus behind establishing a methane
monitoring program regardless of whether the Clean Air Act NSPS or EG are also ARARs.
4.4 State Air Pathway ARARs
In order for a State requirement to be considered an ARAR, they must:
• Be promulgated (be legally enforceable and of general applicability),
• Be identified to EPA in a timely manner,
• Not result in an in-state ban on land disposal of hazardous waste,
• Be more stringent than Federal requirements.
Even if the State standard meets these conditions, it may be waived if it is found not to have
been applied uniformly and consistently throughout the State.
State or local program requirements may apply as ARARs for LFG emissions. These
requirements are generally of four types:
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Emissions from Closed or Abandoned Facilities Guidance for Evaluating Landfill Gas
• Landfill emissions control,
• Ambient air quality standards,
• Acceptable health risk levels, and
• Nuisance rules.
Landfill surface emissions control programs are designed to monitor and reduce emissions
of methane from the landfill surface. These programs were originally designed to reduce the
safety hazards associated with high methane concentrations near the landfill surface. Later,
these programs were often designed or revised to limit emissions of NMOCs or toxic LFG
constituents.
These control programs typically involve routine sampling for methane over the surface of
the landfill. Where these local rules exist to reduce methane hazards, a typical trigger level for
excess methane is typically 500 ppmv. In areas where the rule is designed to reduce emissions
of NMOCs or toxics, a lower threshold is specified (often approximately 50 ppmv).
It should be noted that the CAA NSPS and EG also have requirements for surface moni-
toring of emissions to verify adequate operation of a required collection and control system (40
CFR §60.753). The surface monitoring program requires monitoring over the entire surface of
the landfill at 30 meter intervals and at discrete locations where high methane concentrations
may exist (e.g., surface cracks, stressed vegetation).
Another common type of State or local regulatory program that might be considered an
ARAR for LFG is an ambient air quality standard. These standards may exist for one or more
of the substances listed in Table 1-1 and are usually expressed as a concentration at the facility
fence line. For example, the States of California, New Hampshire, Michigan, New Jersey, Ohio,
Virginia, North Carolina, South Carolina, and others have ambient standards for many haz-
ardous or toxic compounds that are common LFG constituents.
Other States have lists of toxics with a threshold ambient air concentration for each
(typically derived from acute and chronic acceptable exposure levels). Multiple standards may
exist for varying averaging times (e.g., maximum one hour, 24-hour, or annual average). The
methods for estimating LFG emissions and exposures in Chapter 2 can assist in the determina-
tion of compliance with ARARs of this type.
Health risk standards are the last type of State or local ARAR relative to LFG. Some States
have programs in place to limit health risks from air pollution sources below a certain level of
significance (e.g., a 1-in-1,000,000 carcinogenic risk). Generally, these standards are associated
with permitting new or modified sources. If collection and control of LFG is required, however,
the control equipment may be considered a new source and is often subject to permitting
requirements. In these instances, the permit applicant is often required to show that the risk
posed by the new equipment is below a specified threshold.
Many State or local air quality agencies may also have one or more nuisance rules aimed
at controlling air emissions from any source construed as a public nuisance. These rules were
generally developed to cover odor and visibility issues; however, they may also cover emissions
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Guidance for Evaluating Landfill Gas
of toxic substances.
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Emissions from Closed or Abandoned Facilities
5. Landfill Gas Collection and Control Systems
Control of co-disposal landfill air emissions requires both effective collection of the LFG
and effective destruction of organics in the collected gas. Due to the variability of site-specific
factors that affect LFG generation and collection, a wide variety of collection systems are
possible. These systems may include active collection wells (both vertical and horizontal),
passive collection wells, and gas interception trenches. Control systems typically used include
open flares and enclosed flares. Other control systems such as internal combustion engines
(ICEs) and gas turbines are used for energy recovery in the production of electric power for
resale. These types of energy recovery control systems are typically used at active MSW
landfills where a portion of the landfill is subject to a CERCLA remedial action. This chapter
covers the general concepts of collection and control systems used at the majority of closed or
abandoned landfill sites.
5.1 Landfill Gas Collection Systems
The following discussion from U.S. EPA (1991) provides an overview of gas collection
techniques. In addition, Appendix E of U.S. EPA (1999b) provides a summary of the design
plan requirements for all collection systems subject to the CAA NSPS or EG.
Landfill collection systems can be categorized into two basic types: active systems and
passive systems. Active collection systems employ mechanical blowers or compressors to
provide a pressure gradient in order to extract the LFG. Passive collection systems rely on the
natural pressure gradient (i.e., internal landfill pressure created due to LFG generation) or
concentration gradients to convey the LFG to the atmosphere or to a control system.
An active landfill gas collection system consists of vertically or horizontally installed
landfill gas collection wells. The well is designed and constructed so as to prevent air
infiltration into the well intake screen area to minimize surface atmospheric air infiltration into
the landfill. At the wellhead, each well is connected to the next wellhead by a well header pipe
and so on until all headers gathering pipe has been connected to all wells. If there is more than
one header pipe they are finally connected to a one main large diameter pipe. This one large
diameter main pipe is then connected to a knock out receiver (pot) that removes liquid water
condensate. The pipe coming out of the knock out receiver is then connected to the intake pipe
of the landfill gas blower or compressor. The out going pipe from the blower is then finally
connected to the flare stack or candle stick burner intake.
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Guidance for Evaluating Landfill Gas
If the collected gas is to be released directly to the atmosphere without combustion, then
vertical pipes with gooseneck top are normally installed at a regular intervals along each header
pipe to vent landfill gas to the atmosphere. This type of landfill gas collection is known as a
passive gas collection system.
Based on theoretical evaluations, well-designed active collection systems are considered the
most effective means of gas collection. Generally, passive collection systems have much lower
collection efficiency since they rely on natural pressure or concentration gradients as a driving
force for gas flow rather than a stronger, mechanically-induced pressure gradient. A passive
system, however, can be nearly equivalent in collection efficiency to an active system if the
landfill design includes synthetic liners on the top, bottom, and sides of the landfill.
Active collection systems can be further categorized into two types: vertical well systems
and horizontal trench systems. Both types of systems are discussed in Section 5.1.1. Passive
systems are discussed in Section 5.1.2. The type of collection system employed often depends
on the landfill characteristics and landfill operating practices. For example, if a landfill employs
a layer-by-layer landfilling method (as compared to cell-by-cell methods), an active horizontal
trench collection system may be preferred over an active vertical well collection system due to
the ease of collection system installation.
5.1.1 Active Collection Systems
Active collection systems employ mechanical blowers or compressors to create a pressure
gradient and extract the LFG. Active collection systems consist of two major components:
• Gas extraction wells and/or trenches and
• Gas moving equipment (e.g., piping and blowers).
Gas extraction wells may be installed in the landfill refuse or along the landfill perimeter.
For a landfill that is actively accepting waste, wells are generally installed in the capped
sections. Additional wells are installed as more refuse is accumulated.
The wells consist of a drilled excavation 12 to 36 in. in diameter. A 2 to 6 in. diameter
pipe—polyvinyl chloride (PVC), high-density polyethylene (HDPE), stainless steel, or gal-
vanized iron—is placed in the well, and the well is filled with 1-in. diameter or larger, crushed
stone. The pipe is perforated in the area where gas is to be collected but solid near the surface
to prevent air infiltration. A typical extraction well is shown in Figure 5-1.
In unlined landfills, gas extraction wells are usually drilled to the depth of the groundwater
table or to the base of the landfill, whichever is less. In lined landfills, wells are typically drilled
to only 75 percent of the landfill depth to avoid damaging the liner system. Typical well depths
range from 20 to 50 feet but may exceed 100 feet. The spacing between gas extraction wells
depends on the landfill characteristics (e.g., type of waste, degree of waste compaction, LFG
generation rate, etc.) and the magnitude of pressure gradient applied by the blower or
compressor. Typical well spacing ranges from 50 to 300 feet.
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Emissions from Closed or Abandoned Facilities
Valve Box and Cover
Compacted Soil
or Refuse
Gas
Collection
Header to Blower
Gravel
0.02m to 0.075m Dia.
0.075m PVC
Perforated Pipe
Figure 5-1. Gas Extraction Well Head Assembly.
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Guidance for Evaluating Landfill Gas
Trenches may be installed instead of or in combination with wells to collect the LFG. The
trenches can be vertical or horizontal at or near the base of the landfill. A vertical trench is
illustrated in Figure 5-2. A vertical trench is constructed in much the same manner as a vertical
well, except that it extends to the surface along one dimension of the landfill. Horizontal
trenches are installed within a landfill cell as each layer of waste is applied. This allows for gas
collection as soon as possible after gas generation begins and avoids the need for above-ground
piping which can interfere with landfill maintenance equipment. A horizontal trench is
illustrated in Figure 5-3.
FRONT \flBW
Figure 5-2. Vertical Trench for Active Collection System.
QM Collection
Figure 5-3. Horizontal Trench Collection System.
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Emissions from Closed or Abandoned Facilities
A gas collection header system conveys the flow of collected LFG from the well or trench
to the facility housing the blower or compressor. A typical header pipe is made of PVC or
polyethylene and is 6 to 24 inches in diameter.
At SFL sites, the collected LFG is conveyed through the header system by a blower. The
size and type of blower depends on total gas flow rate, total system pressure drop, and vacuum
requirements. For systems requiring only a small vacuum (up to 40 inches of water), sites often
use centrifugal blowers, which offer the advantage of easy throttling throughout their operating
range. These blowers can accommodate total system pressure drops of up to 50 inches of water
and can transport high flow rates (100 to 100,000 cfm). For lower flow rates and higher
pressures, regenerative (combination of axial and centrifugal) blowers are often used.
5.1.2 Passive Collection Systems
As indicated above, passive collection systems rely solely on natural pressure or con-
centration gradients in the landfill to capture LFG. Like active systems, passive collection
systems use extraction wells to collect LFG. The construction of passive collection wells is
similar to that of active wells which is illustrated in Figure 5-1.
The well construction for passive systems is much less critical than for active systems
primarily because the collection well is under positive pressure and air infiltration is not a
concern. Additionally, elaborate well head assemblies are not required because monitoring and
adjustment is not necessary. However, it is important that a good seal be provided around the
passive well when synthetic cover liners are used. Either a boot type seal, flange type seal,
concrete mooring, or other sealing technique is typically used at each well location to maintain
the integrity of the synthetic liner.
5.1.3 Effectiveness of Landfill Gas Collection
The effectiveness of an active landfill gas collection system depends greatly on the design
and operation of the system. From the perspective of air emission control, an effective active
collection system design would include the following attributes:
• Gas moving equipment capable of handling the maximum landfill gas generation rate,
Collection wells and trenches configured such that landfill gas is effectively collected
from all areas of the landfill, and
• Design provisions for monitoring and adjusting the operation of individual extraction
wells and trenches.
An effective passive landfill gas collection system would also include a collection well or
trench configuration that effectively collects LFG from all areas of the landfill. The efficiency
of a passive collection system would also greatly depend on good containment of the LFG. An
example of good containment would be synthetic liners on the top, sides, and bottom of the
landfill.
The first criteria that should be satisfied for an active system is gas moving equipment
capable of handling the maximum LFG generation rate; blowers and header pipes need to be
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Guidance for Evaluating Landfill Gas
sized to handle the maximum LFG generation rate. In addition, collection header pipes should
also be sized to minimize pressure drop.
Each extraction well or trench has a zone of influence within which LFG can be effectively
collected. The zone of influence of an extraction well or trench is defined as the distance from
the well center to a point in the landfill where the pressure gradient applied by the blower
approaches zero. The zone of influence determines the spacing between extraction wells or
location of trenches since an effective collection system covers the entire area of the landfill.
The zones (or radii) of influence for gas extraction wells are illustrated in Figure 5-4.
Extraction Well
R Radius of influence
S Optimal well spacing = 1.732 R
Figure 5-4. Zones of Influence for Gas Extraction Wells.
The spacing between extraction wells depends on the depth of the landfill, the magnitude
of the pressure gradient applied by the blower, type of waste, degree of compaction of waste,
and moisture content of gas. For perimeter extraction wells, additional variables such as the
outside soil type, permeability of the soil, moisture content of the soil, and stratigraphy should
be considered.
The desired method for determining effective well spacing at a specific landfill is the use
of field measurement data. EPA Reference Method 2E can be used to determine the average
stabilized radius of influence for both perimeter wells and interior wells, and this measured
radius of influence can then be used to site wells. A good practice is to place wells along the
perimeter of the landfill (but still in the refuse) no more than the perimeter radius of influence
from the perimeter, and no more than two times the perimeter radius of influence apart. As
shown in Figure 5-5, a helpful technique is to site the location of each well and draw a circle
with radius equal to the radius of influence (perimeter radius of influence for perimeter wells
and interior radius of influence for interior wells). Once the perimeter wells are sited on the
landfill plot plan, the interior wells are sited at no more than two times the interior radius of
influence in an orientation such that essentially all areas of the landfill are covered by the radii
of influence.
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Emissions from Closed or Abandoned Facilities
Active Gas Collection ,_ Branch
Field Extraction
Gas Extraction Well
(Typical)
Header
Flaring/Cogeneration
Station
Waste Management
Unit
Figure 5-5. Typical Gas Control System.
In situations where field testing is not performed, the well spacing can be determined based
on theoretical concepts. Understanding the behavior of LFG through the municipal landfill
refuse and cover material is important in order to design the LFG collection system properly.
The flow of LFG can be described by Darcy's Law, which correlates the flow of gas through
porous media as a function of the gas properties (e.g., density and viscosity), the properties of
the porous media (e.g., permeability of refuse and cover), and pressure gradient.
When active collection systems (both vertical and horizontal) are designed, it is also
important to understand the relationship between the magnitude of vacuum applied and the
degree of air infiltration into the landfill. Excessive air infiltration can kill the methanogens,
which produce LFG from the municipal refuse. If excessive air infiltration continues,
decomposition becomes aerobic and the internal landfill temperature can increase and possibly
lead to a landfill fire. If the landfill conditions are such that air infiltration is significant (e.g.,
highly permeable cover and/or shallow landfill), the magnitude of vacuum applied may need
to be reduced to minimize the amount of air infiltration. A direct consequence of the reduced
vacuum is an increased number of wells or trenches required to achieve the same collection
efficiency. Therefore, consideration of air infiltration is required in designing the active col-
lection systems for shallow landfills. The problem of air infiltration does not exist for passive
systems since passive systems rely on the natural pressure gradient (i.e., difference between
atmospheric pressure and internal landfill pressure) rather than applying vacuum.
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Appendix G of U.S. EPA (1991) contains detailed information useful in designing active
or passive gas collection systems. U.S. EPA (1999b) provides an overview of the design plan
requirements for landfills subject to the NSPS or EG. All of the EPA documents concerning
MSW landfill regulatory requirements and design criteria are available for download from the
EPA website at http://www.epa.gov/ttn/atw/landfill/landflpg.html (accessed August 2005).
5.1.4 LFG to Energy Considerations
Although it may not be required by rule or by hazard and risk assessment, decision makers
may want to consider the technical and economic feasibility of using the LFG as an energy
source. Using LFG as an energy source helps to reduce odors and other hazards associated with
LFG emissions, and it helps prevent methane from migrating into the atmosphere and
contributing to local smog and global climate change. MSW landfills are one of the largest
sources of human-related CH4 emissions. At the same time, CH4 emissions from landfills may
represent a lost opportunity to capture and use it as a significant energy resource. The LFG to
energy proj ects are economically driven and are sensitive to customer needs, the volume of gas,
and the rate at which it is generated. Once the gas is collected, it may be simply burned or flared
(wasted); or be used as an alternative fuel supply for vehicles; or be used to generate electricity;
or replace fossil fuels in industrial and manufacturing operations such as cement manufacturing,
steel making, and greenhouse operations; or be upgraded to pipeline quality gas. The EPA's
Landfill Methane Outreach Program (LMOP) is a voluntary assistance and partnership program
that promotes the use of landfill gas as a renewable, green energy source. LMOP helps
businesses, States, energy providers, and communities protect the environment and build a
sustainable future by preventing emissions of methane through the development of landfill gas
energy proj ects. The Web page for this program is http://www.epa.gov/lmop/ (accessed August
2005).
5.2 Evaluating Existing Gas Collection Systems
In some cases, an active or passive gas collection system will already be in-place at a
facility at the time of site discovery. For these types of situations, the existing system should
be analyzed to determine if it is adequate for the purposes of collecting the maj ority of landfill
gas and whether an active system is operated in such a way as to minimize the infiltration of
ambient air and thus reduce the possibility of landfill fires. The following sections present
theoretical procedures that can be used to make a screening-level determination of the adequacy
of existing collection systems.
5.2.1 Assessment of Existing Active Gas Collection Systems
To determine if the operating practices for an existing active gas collection system are
adequate for reducing air infiltration at the well head, the actual measured vacuum at each well
can be compared with a theoretical maximum value that minimizes air infiltration. The
following equations from Appendix G of U.S. EPA (1991) can be used to calculate the
theoretical maximum vacuum pressure at each well. The theoretical vacuum pressure is then
compared with the measured vacuum pressure. If the actual vacuum pressure for a specific well
-------
Emissions from Closed or Abandoned Facilities
is greater than the theoretical value, consideration should be given to reducing the actual draft
at affected wells by re-balancing the active collection system. The theoretical maximum
vacuum pressure that minimizes air infiltration (Pv) is calculated by
~ [(0.25L)(
£COV
refuse ,
where:
Pv = Theoretical vacuum pressure in Newtons per square meter or pascals,
Patm = Atmospheric pressure (101,325 N/m2),
0.25 = Assumes well depth is 75% of landfill depth,
L = Landfill depth in meters,
kcover = Intrinsic cover permeability in square meters,
Refuse = Intrinsic refuse permeability in square meters,
^ cover = Cover thickness in meters,
Qgen = Peak landfill gas generation rate in cubic meters per second,
A = Landfill area in square meters,
0.0244 = Fraction of air in landfill gas assuming an allowable O2 of 0.5%, and
fJLalr = Viscosity of air in Newton-seconds per square meter.
The value of Pv can be converted to units of inches water gauge (w. g.) at 60 °F by dividing Pv
by 248.84. The value of the peak landfill gas generation rate (Qgen) is normally determined
using the LandGEM model (see Chapter 2). A typical value for the intrinsic refuse permea-
bility (krefuse) is 3.7 x lO'3 m2; and the viscosity of air (jUair) is 1.8 x 10'5 N-s/m2. Table 5-1
provides typical values for the permeability (kcover) and thickness (Dcover) of three cover ma-
terials from U.S. EPA (1991).
Table 5-1. Typical Cover Permeability and Thicknesses.
Cover type Permeability (m2) Thickness (m)
Synthetic 1.0 x 10'18 7.6 x 10'4
Clay 5.0 x 10'15 0.61
Soil 1.0 x IQ-14 0.61
The area of the landfill (^4) in Equation 5-1 can be estimated from the design capacity by
DC
A =
r refuse
'efiiSi
where:
A = Area of landfill in square meters,
DC = Landfill design capacity in kilograms,
(J mfune = In s^u refuse bulk density in kilograms per cubic meters,
5-9
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Guidance for Evaluating Landfill Gas
L = Landfill depth in meters.
Once the theoretical vacuum pressure is calculated using Equation 5-1 for each well, the
radius of influence (Ra) of the well can be estimated from U.S. EPA (1991) by
gen
— 5-3
P" ~ DCkrefuse(WD/L)
where:
Pj = Internal landfill pressure in Newtons per square meter,
Pv = Well head vacuum pressure in Newtons per square meter,
Ra = Radius of influence of well in meters,
r = Radius of outer well (casing) in meters,
fJLyg = Landfill gas viscosity in Newton-seconds per square meter,
P refuse = Refuse density in kilograms per cubic meters,
Qgen = Peak landfill gas generation rate in cubic meters per second,
DC = Landfill design capacity in kilograms,
^refuse = Intrinsic refuse permeability in square meters,
WD = Well depth in meters,
L = Landfill depth in meters.
The internal landfill pressure (P7) should be measured at or near the well of interest. The
value of the well vacuum pressure (Pv) is calculated by Equation 5-1. The landfill gas viscosity
(julfg) is 1.15 x 10"5 N-s/m2, and a typical value for the refuse density (prefuse) is 625 kg/m3.
Equation 5-3 can be solved interactively for the radius of influence (Ra) using an
optimization algorithm such as Goal Seek found in the Microsoft Excel spreadsheet program.
This is done by entering the equations for the left and right sides of Equation 5-1 within
separate cells of the spreadsheet. The Goal Seek algorithm is then invoked such that the value
of Ra is changed until both sides of Equation 5-1 are equal.
With a value of the radius of influence for each well, a circle representing the zone of
influence of each well can be drawn to scale on a site plot plan. With these data, dead areas
between zones of influence can be detected. Dead areas are treated by installing new collection
wells. This may be especially important for landfills without side and bottom liners where the
surrounding native soils offer relatively low resistance to pressure-driven subsurface vapor
flow.
The same type of analysis as that performed above can also be done for horizontal active
collection systems as well as for passive collection systems. The reader is referred to Appendix
G of U.S. EPA (1991) for the appropriate equations.
The screening-level procedures detailed above are designed to provide a rough estimate of
the maximum well head vacuum pressure that minimizes air infiltration and the adequacy of
the existing system with regards to LFG collection. It should be noted that the value of the well
vacuum pressure calculated using Equation 5-1 assumes that the depth of the well pipe is 75
5-10
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Emissions from Closed or Abandoned Facilities
percent of the depth of the landfill. This assumption is based on a depth at which any possible
damage to a landfill bottom liner (if applicable) is avoided. In addition, Equation 5-1 operates
under the assumption that 0.5 percent O2 in the LFG, based on an air concentration of 2.44
percent, is the optimal value. A higher O2 content may be acceptable (i.e., greater air
infiltration) if aerobic decomposition in the upper reaches of the landfill is kept to a minimum
and the increased infiltration does not dilute the CH4 concentration below the UEL of 15 percent
by volume. Excessive aerobic conditions are usually detected by an increase in the gas
temperature at the well head. Gas temperatures greater than approximately 130 °F indicate that
composting is occurring, which increases the possibility of landfill fires.
5.3 Landfill Gas Control Systems
There are two types of LFG control options for SFLs. The first involves destruction of the
LFG constituents by combustion, and the second involves energy recovery from the combustion
of the gas for the purposes of generating electricity for resale. Energy recovery techniques are
used at active MSW landfills and include the use of ICEs, gas turbines, or boiler-to-steam
turbine systems. Because SFLs are closed landfills in most cases, information on energy
recovery systems is not included in this document.
5.3.1 Open Flares
LFG combustion devices that destroy the gas include open flares and enclosed flares. Open
flares can be located at ground level or can be elevated. Although some of these flares operate
without external assist (to prevent smoking), most are air-assisted or use the velocity of the gas
itself to mix the gas and combustion air. Flares shall be designed for and operated with no
visible emissions except for periods not to exceed a total of 5 minutes during any 2 consecutive
hours. Flares shall be operated with a flame present at all times and an owner/operator has the
choice of adhering to either: (A) meet the heat content specifications (greater than 300 Btu/scf
if steam assisted, greater than 200 Btu/scf if unassisted) and meet the maximum tip velocity
specifications (less than 60 ft/sec or up to 400 ft/sec if the LFG heat content is greater than
1,000 Btu/scf) or (B) the flare must have a diameter of 3 inches or greater, be operated without
assistance, the LFG must have a hydrogen content of 8.0 percent (by volume) or greater, and
the flare must not have an exit velocity less than 37.2 m/sec (122 ft/sec). 40 CFR Part 60.18
provides the control device requirements specific to the NSPS applicable to landfill owners
using open flares to meet the regulatory requirements.
LFG is conveyed to the open flare through the collection header and transfer lines by one
or more blowers. A knock-out drum is normally used to remove gas condensate. The LFG is
usually passed through a water seal before going to the flare. This prevents possible flame
flashbacks, caused when the gas flow rate to the flare is too low and the flame front pulls down
into the stack. Purge gas (N2, CO2, or natural gas) also helps to prevent flashback in the flare
stack caused by low gas flow rates. The total volumetric flow rate to the flame must be carefully
controlled to prevent low flow flashback problems and to avoid flame instability. Figure 5-6
shows a small skid-mounted open flare next to a blower station.
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Guidance for Evaluating Landfill Gas
Figure 5-6. Skid-Mounted Open Flare and Blower Station.
5.3.2 Enclosed Flares
Enclosed flares are located at ground level and are enclosed with fire resistant walls (shell)
which extend above the top of the flame. Air is admitted in a controlled manner at the bottom
of the shell. The temperature above the flame can be monitored and the offgas sampled. This
type of flare is in general use at many SFLs because the inlet and combustion gases can be
sampled for a determination of the percent NMOC reduction achieved. Figure 5-7 shows an
enclosed ground flare and blower station, while Figure 5-8 shows a skid-mounted enclosed
ground flare.
Figure 5-7. Enclosed Ground Flare and Blower Station.
5-12
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Emissions from Closed or Abandoned Facilities
Figure 5-8. Small Skid-Mounted Enclosed Ground Flare.
LFG is conveyed to the flare station through the collection header and transfer lines by one
or more blowers. Purge gas is usually needed only for initial purging of the system upon start-
up or during a restart after a flameout. LFG condensate is removed by a knockout drum. In
some cases, LFG condensate is burned in the flare as a liquid stream injected above the burners
(see Section 4.2). A water seal or flame barrier is located between the knockout drum and the
flare to prevent flashbacks. The number of burner heads and their arrangement into groups for
staged operation depends on the LFG flow rate and composition.
To ensure reliable ignition, pilot burners with igniter are provided. The burner heads are
enclosed in an internally insulated shell that can be of several shapes, such as cylindrical,
hexagonal, or rectangular. The height of the flare must be adequate for creating enough draft
to supply sufficient air for smokeless combustion and for dispersion of the thermal plume.
Some enclosed flares are equipped with automatic damper controls. The damper controls
adjust the intake of air by opening and closing the damper near the base of the stack depending
on the combustion temperature. A thermocouple located about 3 feet below the stack outlet is
typically used to monitor combustion temperature. Stable combustion and efficient operation
can be obtained with landfill gases that have heat contents as low as 100 to 120 Btu/scf. It
should be noted that the NSPS standards prohibit the use of flares if the heat content is below
200 Btu/scf; hence supplemental fuel must be provided for flares subject to these regulations.
5.4 Carbon Adsorption Systems
Activated carbon systems are sometimes used to control NMOC emissions from ancillary
treatment systems such as leachate air strippers. Activated carbon acts to adsorb the NMOC
constituents on the surface area of the carbon granules; for the most part, methane passes
through the carbon bed and is not adsorbed. Carbon is activated by a process that greatly
5-13
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Guidance for Evaluating Landfill Gas
increases the surface area of the granules, thus increasing the number of adsorption sites.
Two problems exist with the use of activated carbon. First, water vapor acts as an inter-
ferent to adsorption by competing for adsorption sites. Second, the adsorption of certain
organic species on activated carbon is minimal. Compounds with one or more of the following
physical/chemical properties do not readily adsorb or remain adsorbed to activated carbon,
especially at low vapor concentrations and high relative humidities:
• Molecular weight less than 50 g/gmol (approximate),
• Boiling point less than 20 °C,
• Index of refraction at 20 °C less than 1.40.
In addition, other compounds in the gas stream with a higher affinity for carbon adsorption
will often dislodge (desorb) these compounds. These factors in combination may result in these
types of compounds passing through the carbon bed quickly and, consequently, in unacceptable
inhalation risks.
The following equation developed by the activated carbon manufacturer Calgon Corp-
oration, and presented by Yaws et al. (1995), can be used to estimate the activated carbon
adsorption capacity of individual organic species:
where:
A
A
B
C
D
E
F
log
lo
Cjuf
F juf
5-4
Adsorption capacity of compound /' at equilibrium in cubic centimeters of liquid
per 100 g of carbon,
Adsorption potential of/' (unitless),
1.71
-1.46xlO~2
-1.65xlO~3
-4.11X1Q-4
3.14xlO~5
-6.75xlO~7
and
where:
T
P,
A =
T
5-5
Adsorption potential of compound /' (unitless),
Temperature in Kelvins,
Liquid molar volume of /' in cubic meters per gram-mol, (= I/density x
molecular weight),
Relative polarizability of compound /' (unitless),
Vapor pressure of compound /' in atmospheres,
Partial pressure of compound /' in atmospheres,
5-14
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Emissions from Closed or Abandoned Facilities
and,
^ = [(«2 - l)(«2 + 1)] /
L v ' v ' ->n-heptane
where:
F; = Relative polarizability of compound /' (unitless), and
n = Index of refraction (unitless).
The index of refraction of the compound of interest can be found in the literature. The
following sources list refractive indexes for a wide variety of substances:
• The CRC Handbook of Chemistry and Physics,
• Lange' s Handbook of Chemistry,
• The Merck Index,
• Chemical catalogs (e.g., the one from Aldrich Chemical Co.), and
• MSDS datasheets (many are available on the web).
The index of refraction of n-heptane is 1.3876.
The partial pressure of a given constituent (p,) in Equation 5-5 can be determined from its
vapor concentration and the ideal gas law by
_ Cv,, X R X T 5.7
where:
CVii = Vapor concentration of compound /' in grams per cubic centimeter,
R = Ideal gas constant ( 82.05 atm-cm3/mol-K),
T = Temperature in Kelvins, and
MWt = Molecular weight of compound /' in grams per mol.
An example of using the above procedures is the determination of the adsorption capacity
of vinyl chloride on activated carbon at a temperature of 25 °C and an inlet concentration of 100
ppmv. Under these conditions, the adsorption capacity is calculated to be approximately 2.3
grams of vinyl chloride liquid adsorbed for every 100 grams of carbon. As can be seen, the
carbon adsorption capacity of vinyl chloride is very small. For this reason, a subsequent risk
evaluation would be done assuming that the vinyl chloride emissions are essentially uncon-
trolled.
In addition to the procedures cited above for estimating the adsorption capacity, adsorption
isotherms relating the adsorption capacity as a function of the partial pressure and temperature
can often be acquired from the manufacturer of the activated carbon. These isotherms and the
equations given above assume a single contaminant in the vapor stream. Actual adsorption of
individual contaminants in a multi-component vapor stream will be somewhat less.
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Guidance for Evaluating Landfill Gas
5.5 Stack Sampling
Methods for assessing combustion equipment emissions (e.g., enclosed flares, boilers, ICEs,
etc.) are given in Table 5-2. These include methods for such pollutants as NOX, SO2, CO, and
NMOCs and for toxic LFG COPCs. Table 5-2 contains a column for EPA Reference Test
Methods found in 40 CFR Part 60, Appendix A and a column for RCRA SW-846 Test
Methods. SW-846 is a compendium of RCRA test methods titled Test Methods for Evaluating
Solid Waste, Physical/Chemical Methods and is available from the EPA Office of Solid Waste
website at: http://www.epa.gov/sw-846/ (accessed August 2005).
Table 5-2. Stack Sampling Methods for LFG Combustion Equipment.
Pollutant
Oxides of nitrogen (NOX)
Sulfur dioxide (SO2)
Carbon monoxide (CO)
Nonmethane organic compounds (NMOCs)
Volatile organic compounds (VOCs)
Chlorinated dioxins/furans
Hydrogen chloride (HC1)
Mercury (Hg)
EPA Reference
Methods
7or7E
6
10or3C
25/25 A/25B or 18
18
23
26
101A
EPA SW-846
Methods
NAa
NA
NA
NA
0030 or 0031
0023A
0050 or 0051
0060
a NA = Not applicable.
In some respects, the SW-846 test methods may be more suitable for high temperature
combustion sources such as enclosed flares. EPA Reference Methods 25 or 18, however, must
be used to determine compliance with the 98 percent by weight NMOC reduction requirements
or the 20 ppmv NMOC concentration requirements of the NSPS or EG.
Mercury-bearing material has been placed in municipal landfills from a wide array of
sources including fluorescent lights, batteries, electrical switches, thermometers, and general
waste. Despite its known volatility, persistence, and toxicity in the environment, the fate of
mercury (Hg) in landfills has not been widely studied. Landfills are designed to reduce waste
through generation of methane by anaerobic bacteria. This suggests the possibility that these
degradation systems might also serve as bioreactors capable of generating methylated Hg
compounds. The toxicity of these Hg compounds indicates the need to determine if they are
emitted in municipal landfill gas (LFG).
Mercury is a highly toxic heavy metal that exists primarily in three forms: elemental Hg,
inorganic Hg compounds (e.g., mercuric chloride), and organic Hg compounds (e.g., methyl and
dimethyl mercury). People are most likely to be exposed to Hg through the consumption offish
or seafood. Mercury is most likely to be present in fish tissue as methyl mercury, which happens
to be the most toxic form of Hg to humans. However, concern over air emissions is not limited
to methyl mercury because other forms of Hg can be converted to methyl mercury in the
5-16
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Emissions from Closed or Abandoned Facilities
environment through methylation.
In the initial development of emissions factors for constituents of LFG, the U.S. EPA
published a default total Hg concentration in AP-42 equivalent to 292 parts per trillion (ppt),
with no data on individual Hg species. At this concentration, Hg emissions from landfills are
extremely low, if not negligible. However, in the late 1990s, a study conducted by Lindberg et
al. at a landfill in Florida suggested that levels of total Hg in LFG might be several times higher
than EPA default values, though still much lower than other common landfill trace constituents.
This study was also perhaps the first to positively identify the more toxic organic mercury
compounds methyl and dimethyl mercury in LFG.
EPA researchers measured Hg inside the landfill gas vents at concentrations ranging from
a few hundred to several thousand nanograms per cubis meter. Although the higher end is
equivalent to levels emitted by a coal-fired utility plant, the volume of gas emitted at a landfill
is considerably lower. Consequently, the overall contribution of Hg to the atmosphere from
municipal landfill gas is small in comparison to coal-fired power plants. However, there may
be important contributions of Hg to the atmosphere in the immediate local area near the landfill.
During the NESHAP rule making, EPA found insufficient data to adequately characterize
the concentrations of Hg in landfill gas or determine their significance. Based on the available
information, it was concluded that the Maximum Achievable Control Technology (MACT)
floor for Hg is no emissions reductions because there are no alternatives above that floor. The
NESHAP standard does not require a reduction in Hg emissions. Although the NESHAP does
not require Hg emissions reductions, the risks and hazards associated with mercury continues
to be a sensitive subject with the ecological community.
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Guidance for Evaluating Landfill Gas
5-18
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Emissions from Closed or Abandoned Facilities
6. Illustrative Case Studies
The procedures and methodologies described within this guidance were implemented at
three separate sites, and a summary of each case study is presented herein. These case studies
were not intended to provide a comprehensive site analysis or complete risk assessment. Case
studies were developed for:
Somersworth Sanitary Landfill Superfund Site, City of Somersworth in Strafford
County, New Hampshire. EPA-600/R-05/142.
• Rose Hill Regional Landfill Superfund Site is located within the town of South
Kingstown, Rhode Island in the Village of Peace Dale. EPA-600/R-05/141.
• Bush Valley Landfill Superfund Site is located in Harford County, Maryland, one mile
from the town of Abingdon. EPA-600/R-05/143.
The parameters of the three case studies are summarized in Table 6-1.
Table 6-1. Comparisons of the Case Studies.
Parameter
Somersworth
Rosehill
Bush Valley
Capacity, Mg
Size, acres
Year open
Size of grid, m2
Number of grids
Number of COPCs
Number of parcel per Wilcoxon analysis
COPC with highest LFG concentration
COPC with largest facility boundary am-
bient air concentration
COPC exceeding R=106, HI = 1
300,000
26
1958
900
179
11
1
Toluene
Xylene
None
199,692
28
1967
900
190
10
2
Toluene
Xylene
None
303,128
16
1974
900
108
9
4
Vinyl chloride
Xylene
Trichloroethylene
The example case studies are published as standalone documents for reference by the
practitioner. They are available for viewing or downloading from EPA's Hazardous Waste
Cleanup Information (CLU-IN) web site athttp://cluin.org (accessed August 2005). Hard copies
are available from:
National Technical Information Service
5285 Port Royal Road
6-1
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Guidance for Evaluating Landfill Gas
Springfield, VA 22161
Telephone: (703) 605-6000, (800) 553-6847 (U.S. only)
6.1 Summary of the Somersworth Sanitary Landfill Superfund Site
Two independent studies were conducted to characterize the landfill emissions being
generated by the Somersworth Sanitary landfill.
The two studies used inherently different methods for determining LFG emissions. Study
1 utilized both above and below grade LFG analyses, whereas, Study 2 exclusively used above
grade ambient analyses. Study 1 utilized whole air broad spectrum ambient sampling and below
grade LFG sampling (i.e., Summa sampling). The below grade sample locations were chosen
after an extensive surface survey, using field instrumentation, was completed. In comparison,
Study 2 used ground-based optical remote sensing to quantify the LFG emissions and to
calculate emission fluxes. Radial plume mapping was used to detect potential hot spots. Vertical
scans were conducted to determine mass flux emissions for speciated organic compounds using
OP-FTIR. Study 1 relied on fate and transport models for derivation of the LFG emission
fluxes. Study 2 used an algorithm that integrated the measured COPC concentrations using real
time wind speed to estimate the gas emission fluxes.
The Somersworth Sanitary Landfill Superfund Site (the "Site") is located 1 mi southwest
of the center of the City of Somersworth in Strafford County, New Hampshire. The Site
includes an approximately 26 acre waste disposal area. The City owns the entire landfill area
and much of the adjacent wetlands northwest of the former landfill. The landfill was operated
by the City from the mid 1930's until 1981 when the City began taking wastes to a regional
incinerator. With the cessation of land fill operations, the City installed four ground water
monitoring wells near the Site's northern and western boundaries. Samples taken from these
wells indicated the presence of VOC contamination. As a result of this and subsequent
investigations, the landfill was placed on the NPL on September 8, 1983. Approximately ten
acres of the eastern portion of the landfill have been reclaimed by the City for recreational
facilities; tennis and basketball courts, ball fields, and a playground. Numerous soil gas
monitoring wells have been installed and are routinely monitored around the extent of the
landfill. The majority of these wells are located along the borders immediately adjacent to
residential development. From previous studies there is an indication that the groundwater flows
northwesterly towards the Peter's Marsh Brook, and it surfaces to the brook and adjacent
wetlands.
Based upon the results of the Remedial Investigation and the alternatives presented in the
feasibility study, EPA issued a Record of Decision (ROD) on June 24, 1991 documenting the
selection of an innovative technology to remediate groundwater at the site. This technology uses
elemental iron in a permeable reactive "wall" which treats contaminated groundwater as it
flows through it. A key element of this remedy is the use of a permeable landfill cover to allow
precipitation to flush contamination through the waste. The contaminants are treated as the
groundwater passes through the wall. Existing records indicated that LFG was being generated,
so it was decided to use this site to illustrate this document.
6-2
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Emissions from Closed or Abandoned Facilities
6.1.1 Somersworth - Study One
Field activities for the Somersworth site were conducted in July 2002. Site activities
included debriefing interested parties and stake holders, screening landfill surface, reducing
screening data, determining "hot spots" and homogeneity, sampling landfill soil gas, sampling
passive vent gas, sampling perimeter well gas, and sampling ambient air.
To assist with the field activities aSOmbySOm sampling grid was developed across the
extent of the landfill area prior to the field activities. This sampling grid was developed to
include the entire landfill boundary area and to extend 30m beyond that boundary area. Each
node (the intersection of the grid lines shown in Figure 6-1) of this grid was then numbered,
forming a serpentine sampling pathway across the grid, and 179 monitoring and potential
sampling locations were identified. The grid was superimposed on an aerial photograph (see
Figure 6-1) in order to visualize the node locations and to establish where the monitoring and
sampling efforts would begin.
The screening analysis procedures included taking measurements for NMOCs using a PID
and for CH4 using a FID. The PID and FID were calibrated to using certifiable zero air and 5
and 20 ppm gases. Both detectors were held no more than one inch above the ground while
measurements were being made. Readings were taken for approximately one minute and the
average value, excluding the extreme highs and lows, was recorded. In conducting the
serpentine walk across the site, an effort was made to identify areas containing cracks and gaps
in the landfill cover; and, to the extent possible, measurements were also made at these
locations. Ninety seven percent of the targeted data was collected and validated. All
predetermined sampling locations were not accessible due to a variety of reasons, ranging from
being located on private property to being inaccessible because of extreme overgrowth or being
in a waterway or roadway.
The screening data were used for two analyses. The first was for a hot spot analysis. This
was done by importing the measured NMOC and CH4 screening data set into a graphical
contouring software package (Surfer) to produce concentration contours, which were layered
over an aerial photograph of the site. This allowed for a visual determination of where the
higher concentrations were recorded during the screening analysis. This method also allowed
data to be divided into two data sets based on the contours derived from these data. This
population division was used as part of the homogeneity determinations, which was the second
analysis. This was done through statistical means by using the Wilcoxon Rank Sum statistical
method. This method determines whether two data sets are statistically similar (i.e., homo-
geneous). If the two sets are determined to be similar, then the two populations are determined
to be one nearly homogeneous area. If the two data sets are determined not to be statistically
similar, then the two sets are said to be two non-homogeneous areas.
Based on the data analysis conducted, it was determined that the site is one nearly
homogeneous area. It was determined that six LFG samples would be collected for demonstra-
tion purposes. The LFG samples were collected at the locations that had the highest recorded
readings for CH4 gas. It should be noted that due to the absence of detectable NMOC
concentrations during the screening analysis it was determined that CH4 gas concentrations
would be used to determine further sampling strategies.
6-3
-------
Somersworth Landfill
Somersworth, NH
Sampling grid is
30 m by 30 m
ENVIRONMENTAL QUAUTY MANAGEMENT, INC.
3JM DUBVW-CHWEt. HIU WU.tV«D, SUITE 5*1
SUCH**. MnBTH CN^LIM 27797
<««} 499-5299 r»* t«9J 489-5593
SDMERSWORTH LANDFILL
Fig 2. Sampling Location Map
Sonersworth, Ne» Hampshire
B 030177.0003
Figure 6-1. Somersworth Sampling Grid.
o
D)
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Emissions from Closed or Abandoned Facilities
Sampling was conducted using a slam-bar to drive a sampling hole through the landfill
cover to approximately 5 feet below grade. A sampling probe was inserted into the landfill
area, and the hole was sealed around the probe to minimize ambient air in-leakage. Additional
field instrumentation was used to measure fixed gases (CO2, N2, and O2) at each of the
designated sampling locations. The fixed gas concentration values were used to verify that LFG
was being collected. As part of this demonstration, LFG samples were collected for the COPC
via evacuated Summa Canister, which were sent to an off-site commercial laboratory for
analysis using EPA Method TO-15. The concentration results were validated, and the 90th
percentile concentrations were determined for 11 COPCs. Table 6-2 presents the COPCs that
were quantified.
Table 6-2. Somersworth COPCs that were Quantified.
COPCs
NMOC
1 , 1 -Dichloroethene
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Methylene Chloride
Toluene
Trichloroethene
Vinyl Chloride
m, p-Xylene
o-Xylene
Landfill Gas Concentration
90th Percentile
(ppmv)
2380
0.00152
0.244
0.0208
0.408
0.4288
0.236
1.348
0.01428
1.22
2.14
0.72
(Rg/m3)
1.19xl06
6.07
7.93xl02
9.78xl02
1.09xl03
2.62xl03
8.33xl02
5.16xl02
77.8
3.17xl03
9.44xl03
3.17xl03
LFG emission rates for each COPC were estimated using the LandGEM model. Figure 6-2
shows an example output file for NMOC emissions from the LandGEM model. Figure 6-3
shows the emission rate data for NMOC versus time. Table 6-3 provides the emission rates
estimated for each COPC.
The next step in characterizing the emissions of LFG was to evaluate the ambient impact
of each of the COPs. For this analysis, it is necessary to use an atmospheric dispersion model.
For demonstration purposes SCREENS was used to provide a screening level assessment, and
the model was configured as if the landfill was a rectangular area source. The landfill was
modeled by using a unit emission rate of 1 g/s to provide a maximum 1-h concentration.
Because the landfill was modeled on a unity basis, the emission rates generated from the
LandGEM model were multiplied by the unity-derived concentration factor to determine the
1-h maximum concentrations for each COPC. To convert these maximum hourly concentra-
6-5
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Guidance for Evaluating Landfill Gas
Lo : 170.00 mA3 / Mg ***** User Mode Selection *****
k: 0.0500 1/yr ***** User Mode Selection *****
NMOC : 2380.00 ppmv ***** User Mode Selection *****
Methane : 58.0000 % volume
:arbon Dioxide : 42.0000 % volume
Landfill type : Co-Disposal
Year Opened : 1958 Current Year : 2003 Closure Year: 2003
Capacity : 300000 Mg
Average Acceptance Rate Required from
Current Year to Closure Year : 0.00 Mg/year
NMOC Emission Rate
Year Refuse In Place (Mg) (Mg/yr) (Cubic m/yr)
Model Parameters
Landfill Parameters
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
2001
2002
2003
2200
2201
2202
Model Results
1.304E+04
2.609E+04
3.913E+04
5.217E+04
6.522E+04
7.826E+04
9.130E+04
1.043E+05
1.174E+05
1.304E+05
1.435E+05
1.565E+05
1.696E+05
1.826E+05
1.957E+05
2.087E+05
2.217E+05
2.348E+05
2.478E+05
2.609E+05
2.739E+05
2.870E+05
3.000E+05
3.000E+05
3.000E+05
3.000E+05
3.000E+05
3.000E+05
3.000E+05
3.000E+05
3.000E+05
1.631E+00
3.182E+00
4.658E+00
6.061E+00
7.396E+00
8.666E+00
9.874E+00
1.102E+01
1.212E+01
1.316E+01
1.415E+01
1.509E+01
1.598E+01
1.683E+01
1.764E+01
1.841E+01
1.915E+01
1.984E+01
2.051E+01
2.114E+01
2.174E+01
2.231E+01
2.285E+01
2.174E+01
2.068E+01
4.549E+02
8.877E+02
1.299E+03
1.691E+03
2.063E+03
2.418E+03
2.755E+03
3.075E+03
3.380E+03
3.670E+03
3.946E+03
4.209E+03
4.459E+03
4.696E+03
4.922E+03
5.137E+03
5.341E+03
5.536E+03
5.721E+03
5.897E+03
6.064E+03
6.223E+03
6.375E+03
6.064E+03
5.768E+03
8.406E+00 2.345E+03
7.996E+00 2.231E+03
7.606E+00 2.122E+03
4.012E-04
3.816E-04
3.630E-04
1.119E-01
1.065E-01
1.013E-01
Figure 6-2. Somersworth - Example LandGEM Model Run Output.
-------
Emissions from Closed or Abandoned Facilities
LU
1950 1970 1990 2010 2030 2050 2070 2090 2110 2130 2150 2170 2190
Time (yr)
Figure 6-3. Somersworth NMOC Emission Rates versus Time.
Table 6-3. Somersworth - Emission Rates for COPCs.
COPCs
NMOC
1 , 1 -Dichloroethene
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Methylene Chloride
Toluene
Trichloroethene
Vinyl Chloride
m, p -Xylene
o-Xylene
2002 Emission
Rates
(Mg/yr)
7.996
5.744xlO-6
7.43 IxlO'4
9.127xlO-5
1.026xlO-3
2.457xlO-3
7.814xlO-4
4.842xlO-3
7.314xlO-5
2.973 xlO'3
8.857xlQ-3
2.980xlO-3
tions to a representative annual concentration all derived 1-h concentrations were multiplied
by the appropriate correction factor of 0.08. Table 6-4 provides the maximum annual concen-
trations for each COPC.
6-7
-------
Guidance for Evaluating Landfill Gas
Table 6-4. Somersworth - Maximum Annual Concentrations of COPCs.
Maximum Annual Fence Line
COPC Concentration
(ppmv) (|ig/m3)
NMOC
1 , 1 -Dichloroethene
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Methylene Chloride
Toluene
Trichloroethene
Vinyl Chloride
m, p -Xylene
o-Xylene
4.14x
3.72x;
5.92x;
5.02x;
9.89x
1.04x
5.72x;
3.27x;
3.47x;
2.96x;
5.20x;
1.75x;
io-2
io-2
io-7
io-8
io-7
i r\-6
IO-7
i r\-6
IO"8
i r\-6
1 A-6
i r\-6
20.
1.486
1.922
2.361
2.654
6.356
2.021
1.253
1.892
7.691
2.291
7.709
69
xlO-5
xlO-3
xlO-4
xlO-3
xlO-3
xlO-3
xlO-2
xlO-4
xlO-3
xlO-2
xlO-3
These predicted ambient air concentrations were then compared to the target concentrations
presented in Table 6-5, which also identifies target media concentrations corresponding to
risk/hazard based concentrations for ambient air in residential settings. The target concentra-
tions were derived using Equation 2-8 and the appropriate toxicity factors. The New Hamp-
shire ambient air toxic standards are also displayed for comparative purposes. Only air
concentrations that satisfy the prescribed cancer risk level and the target hazard index are
included in Table 6-5. It would appear that the emissions from this site are below those that
would be considered a health hazard.
6.1.2 Somersworth Study Two
The second study (Study 2) was conducted in September and October 2002 in which the
emissions from the landfill were measured using an OP-FTIR spectrometer (U.S. EPA, 2004).
This study involved a technique which uses ORS radial plume mapping techniques to eval-
uate emissions. The focus of this study was to characterize the emissions of CH4 and hazardous
air pollutants. Concentrations were measured for each compound and fluxes were calculated
for each compound detected.
In reviewing the two studies it appears that the relative concentration contours generated
via the field survey in Study 1 and OP-FTIR in Study 2, produce very similar concentration
gradients and relative CH4 hot spot locations. Table 6-6 shows a comparison of the hot spot
locations identified from each study and gives their relative range of values within these areas.
The measurement techniques do not differentiate between background levels and those emitted
by the landfill. The CH4 is presumed to be emitted by the landfill. The studies were completed
independently and meteorological conditions are known to have been different. Study 1 was
-------
Emissions from Closed or Abandoned Facilities
more windy than Study 2. Rainfall occurred two days prior to Study 1 and six days prior to
Study 2. The significance of the differences is unknown.
Table 6-5. Somersworth Risk Analysis.
CAS
No.
75354
71432
108907
75003
106467
75092
108883
79016
75014
108383
95476
Chemical
1,1-Dichloro-
ethylene
Benzene
Chlorobenzene
Chloroethane
(ethyl chloride)
1,4-Dichloro-
benzene
Methylene
chloride
Toluene
Trichloro-
ethylene
Vinyl chloride
(chloroethene)
m, p-Xylene
o-Xylene
Basis of
Target
Concen-
tration
NCa
Cb
NC
C
C
c
NC
C
c
NC
NC
Target Ambient Air
Concentration to Satisfy
Both the Prescribed
Risk Level and the Tar-
get Hazard Index
(R=10 6, HI=1) Ctarget
Cancer Noncancer
2.1xlO+2
0.25 0.31
62.
2.3 1.0xlO+4
31. 8.4xlO+2
4.1 3.1xlO+3
4.0xlO+2
1.7xlO-2 37.
0.11 1.0xlO+2
l.lxlO+2
l.lxlO+2
NH Regulated
Toxic Air Pol-
lutant Annual
Ambient
Limits
67
3.80
154
10,000
800
414
400
640
100
1033
1033
Total
Ambient
Air
Concen-
trations
1.5x
1.9x
2.4x
2.7x
6.4x
2. Ox
1.3x
1.9x
7.7x
2.3x
7.7x
aO-
:10'3
10"4
ao-3
aOJ
ao-3
ao-2
10"4
' i n~^
ao-2
ao-3
a NC = noncancer risk.
b C=cancer risk.
Table 6-6. Somersworth - Comparison of CH4 Concentrations by Study Method.
Location
Southeast Corner Baseball Field
Tennis Court Area
Open Field North of Infiltration Gallery
Passive Vents (Light Pole Borings)
Field Instrument
ppmv
0.5 to 1.5
0.5 to 8.0
0.5 to 3.0
84 to 5 15
OP-FTIR
ppmv
0.5 to 6.5
l.Oto 1.5
0.5 to 2.5
NA
6-9
-------
Guidance for Evaluating Landfill Gas
No NMOC was detected by the FTIR unit at or above instrument detection limits, and
Study 1 confirmed this finding via several methods. Study 1 found no detectable concentrations
of NMOC above the landfill cover during the grid survey. Additionally, the ambient whole air
samples collected at or near the CH4 hot spots were below the analytical detection limits for all
compounds except acetone and methylene chloride (two common laboratory contaminants).
Lastly, Study 1 collected LFG data from below the landfill cover as part of the study tech-
nique, and the analysis of these data and subsequent modeling runs with LandGEM and
SCREENS produced emission results that were well below the allowable detection of the
OP-FTIR method and PID instrumentation.
6.2 Summary of the Rose Hill Regional Landfill Superfund Site
The Rose Hill Regional Landfill (Regional Landfill) is located within the town of South
Kingstown, Rhode Island in the village of Peace Dale. The facility is composed of three
separate, inactive, disposal areas, including the solid waste landfill, a bulky waste disposal area,
and a sewage sludge landfill. These areas have been covered with soil and graded, and currently
support vegetative cover. An active transfer station is located on site where municipal refuse
is unloaded from the refuse collection trucks and transferred to trucks that haul the refuse
offsite to a separate landfill facility owned and operated by the State of Rhode Island.
Residential development has occurred along Broad Rock Road, 1200 feet east of the site. There
has also been considerable development along Rose Hill Road to the north of the site. A golf
course and clubhouse have been constructed on the west side of Rose Hill Road, immediately
opposite the facility and to the north of an active sand and gravel operation.
The Rose Hill Regional Landfill, which began operation in 1967, is located in an abandoned
gravel quarry. The Regional Landfill operated as a municipal disposal facility for the towns of
South Kingstown and Narragansett. Industrial waste, however, was also accepted at the facility
during its years of operation. In October 1983, the Regional Landfill reached its State permitted
maximum capacity and ceased active land filling operations. The solid waste landfill located
in the western portion of the site covers approximately 28 acres, and it operated from 1967 until
1982. The depth of the solid waste landfill varied, but it reportedly extended to bedrock in some
places. Refuse was reportedly deposited in areas at, above, and below the water table. From
1977 to 1982, between 10 and 14 feet of solid waste was deposited. Boring logs indicate that
bedrock was encountered at 31.3 feet on the west side of the site along Rose Hill Road. From
a seismic survey it appears that the depth to bedrock along the south of the solid waste landfill
is between 29 to 32 feet below ground surface. Upon closure, the solid waste landfill was
covered with 0.5 to 2 feet of sandy soil and subsoil and seeded.
On-site groundwater monitoring wells contain several VOCs including dichloroethane,
chloroethane, vinyl chloride, benzene, and xylenes, as well as some heavy metals. Visual
observations indicate that Mitchell Brook, an unnamed brook, and the Saugatucket River are
impacted by contaminated run-off from the site. Early investigations determined that landfill
gases were migrating laterally off-site in the vicinity of some residential properties. Three
private wells adj acent to the site are contaminated with low levels of organic compounds, as are
on-site soils. The site is not completely fenced, making it possible for people to come into direct
contact with the landfill materials on-site. EPA investigations during the winter and spring of
6-10
-------
Emissions from Closed or Abandoned Facilities
1993 indicated gas migration from the landfill to nearby residences. In response to this
information, the Town of South Kingstown installed gas alarms in the residences and relocated
one residence.
The first operable unit remedy consists of the following components: (1) consolidate the
bulky waste area landfill onto the solid waste area landfill; (2) collect and manage leachate and
waters collected from run-off and de-watering operations during the excavation and
consolidation of the bulky waste area; (3) apply a protective cover (hazardous waste cap) to the
solid waste area landfill; (4) assess, collect and treat landfill gases via an enclosed flare; (5)
inspect and monitor the integrity and performance of the cap over time; (6) monitor
groundwater, surface water, leachate emergence, and LFG emissions over the duration of the
remedial action; (7) implement deed restrictions (in the form of easements and covenants) on
groundwater and land use to prevent access onto portions of the site where remediation
activities warrant this restriction; (8) provide data to assess the need for taking any further
response actions after the cap is in place and functional; (9) perform appropriate operation and
maintenance of the remedy; and (10) plan for and conduct statutory 5-year reviews to ensure
protectiveness. The State, with assistance from EPA and the two towns, will prepare and expect
to release the bid package(s) and associated contract document(s) during the winter of
2004-2005. Actual construction of the remedy is planned to start during the early summer of
2005 and may take upwards of two years to complete.
6.2.1 Rose Hill - Using the Procedure of Screening with Probes Placed Just
Below the Cover
For the reasons described above, it was determined that this site could be used to illustrate
the screening and just-below-the-cover methods and procedures described earlier in this
document. Field activities were conducted at the Landfill from July 22, 2002, through July 25,
2002. Field activities included landfill surface screening analysis, screening data reduction, hot
spot and homogeneity determinations, landfill soil gas sampling, passive vent gas sampling,
perimeter well gas sampling, and ambient air sampling.
Prior to arrival at the site, the U.S. EPA JAPM notified the immediate surrounding resi-
dences and businesses that an assessment was to be conducted on and around the landfill area.
This was performed as part of a public relation effort to notify the public and address any
concerns prior to the activities taking place.
To assist with the field activities, a 30 m by 30 m sampling grid was developed across the
extent of the landfill area prior to the field activities. This sampling grid was developed to
include the entire extent of the landfill boundary area and to extend 30m beyond it. The nodes
of this grid were then numbered, forming a serpentine sampling pathway across the grid. Thus,
a total of 190 predetermined sampling nodes comprised the sampling grid layout developed for
this site. A reference point was identified using an identifiable landmark on the site to locate
the starting point. Figure 6-4 shows the grid and pathway used for the screening analysis.
6-11
-------
Rose Hill Landfill
Kingstown, Rl
Sampling grid is
30 m by 30 m
ENVIRONMENTAL QUALITY MANAGEMENT, IMC.
ROSE HILL LANDFILL
Figure 2, Sampling Locations
South Kingstown, Rhode Island
B 030177.0003
Figure 6-4. Rose Hill - Screening Sampling Grid.
o
fi)
-------
Emissions from Closed or Abandoned Facilities
6.2.2 Landfill Surface Screening Analysis
Once on site, the reference point was visually located, and using a handheld global
positioning system (GPS), the starting point (node No. 1) was located to begin the screening
analysis. The screening analysis included measurements forNMOCs, using aPID and for CH4
using a FID. Both detectors were held no more than 1 in. above the ground while measure-
ments were being made. It should be noted that the field instrumentation was very sensitive and
drifted quite significantly due to gusts of wind across the landfill cover. Readings were taken
for approximately 1 min, and the average values, excluding the extreme highs and lows, were
recorded.
While conducting the serpentine walk across the site, an effort was made to identify areas
containing cracks and gaps in the landfill cover, and measurements were made at these locations
to the extent possible. All predetermined sampling nodes were not accessible due to a variety
of reasons, ranging from being located on private property to inaccessible because of extreme
overgrowth or being in a roadway or streambed. An attempt was made to collect a reading at
each node, with measurements being collected not more than 10m from it. If access within an
acceptable range was not possible, a replicate reading was made at the next accessible node.
These replicate readings were intended to provide additional information for Quality Assurance
and Quality Control (QA/QC) purposes and were not intended to back fill missing data due
inaccessible areas. Duplicate readings were also taken at predefined locations as part of QA/QC
efforts. These predetermined locations were selected based on a random number generator. All
screening data were recorded on field log data collection forms along with any field notes
relevant to this specific location. There was 89 percent data collection efficiency. Table 6-7
illustrates the screening sample results for the first 29 grid locations.
The screening data collected were used for two analyses. The first was for a hot spot
analysis. This was accomplished by importing the screening data set into a graphical con-
touring software package (Surfer) to produce concentration contours, which were layered over
an aerial photograph of the site. This allowed a visual determination of where the higher con-
centrations were recorded during the screening analysis. This also allowed the data to be
divided into two sets based on the contours derived from these data. This population division
was used as part of the homogeneity determinations. Figures 6-5 and 6-6 show the concentra-
tion contours for both NMOC and CH4, respectively.
The second analysis provided a determination of the homogeneity of the site, which was
done using the Wilcoxon Rank Sum statistical method. This method determines whether two
data sets are statistically similar (i.e., homogeneous). If the two sets are determined to be
similar, then the two populations are determined to be one nearly homogeneous area. If the two
data sets are determined not to be statistically similar, then the two sets are said to be two
non-homogeneous areas. To accomplish this task, the hot spot analysis was used to determine
if there appeared to be two distinct population sets. For this site it was shown that there existed
two nearly homogeneous areas.
Sampling activities included sampling landfill soil gas, passive vent gas, perimeter well
gas, and ambient air. Each of these sampling methods will be discussed further in the following
sections.
6-13
-------
Guidance for Evaluating Landfill Gas
Table 6-7. Rose Hill Screening Sample Results (Partial)
N0(je Actual UTM Coordinates
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Sample ID No.
LFSG-02-072202- R- 001
LFSG-02-072202- R- 002
LFSG-02-072202- R- 003
LFSG-02-072202- R- 004
LFSG-02-072202- R- 005
LFSG-02-072202- R- 006
LFSG-02-072202- R- 007
LFSG-02-072202- R- 008
LFSG-02-072202- R- 009
LFSG-02-072202- R- 010
LFSG-02-072202- R- Oil
LFSG-02-072202- D- 001
LFSG-02-072202- D- 002
LFSG-02-072202- R- 012
LFSG-02-072202- R- 013
LFSG-02-072202- R- 014
LFSG-02-072202- R- 015
LFSG-02-072202- R- 016
LFSG-02-072202- R- 017
LFSG-02-072202- R- 018
LFSG-02-072202- R- 019
LFSG-02-072202- R- 020
LFSG-02-072202- R- 021
LFSG-02-072202- R- 022
LFSG-02-072202- R- 023
LFSG-02-072202- R- 024
LFSG-02-072202- R- 025
LFSG-02-072202- D- 003
LFSG-02-072202- D- 004
Easting
291648
291659
291686
291719
291742
291773
291744
291714
291683
291656
291645
NAb
NA
291634
291657
291684
291712
291745
291778
291803
291808
291782
291742
291710
291681
291654
291628
NA
NA
Northing
4593806
4593806
4593802
4593807
4593813
4593838
4593836
4593835
4593833
4593829
4593834
NA
NA
4593867
4593862
4593866
4593865
4593865
4593862
4593861
4593862
4593896
4593902
4593903
4593899
4593897
4593896
NA
NA
NMOC
Cone.
(ppm)
0.20
0.43
0.20
0.20
0.20
ND
0.20
0.20
1.80
0.40
ND
NA
NA
ND
0.30
0.60
ND
ND
0.26
ND
ND
ND
ND
ND
0.20
ND
ND
NA
NA
CH4
Cone.
(ppm)
NDa
ND
ND
ND
ND
ND
ND
1.00
ND
ND
ND
NA
NA
ND
25.00
ND
ND
300.00
350.00
ND
ND
ND
ND
ND
ND
2.10
ND
NA
NA
aND = not detected.
b NA = not available.
6-14
-------
Emissions from Closed or Abandoned Facilities
4593800
291200 291250 291300 291350 291400 291450 291500 291550 291600 291650 291700 291750 291800 291850 291900 291950 292000
Figure 6-5. Rose Hill - Measured Screening Results for NMOC (ppm).
4693800
291200 291250 291300 291350 291400 291450 291500 291550 291600 291650 291700 291750 291800 291850 291900 291950 292000
Figure 6-6. Rose Hill - Measured Screening Results for Methane (ppm).
6-15
-------
Guidance for Evaluating Landfill Gas
As part of this demonstration, landfill soil gas samples were collected for COPC analysis
by two methods. The first set of samples was collected using a Summa canister and sent to an
off-site commercial laboratory for analysis. The second set of samples was collected with
Tedlar bags and analyzed at the on-site laboratory provided by EPA's Environmental Response
Team Center (ERTC). Field instrumentation was used to measure fixed gases (CO2, N2, and O2)
at each of the designated sampling locations to verify that LFG was being collected. Sampling
was conducted using a slam-bar to drive a sampling hole through the landfill cover; a sampling
probe was inserted into the landfill area; and the hole was sealed around the probe to minimize
ambient air in-leakage.
Three Tedlar bag and three Summa canister samples were collected at grid locations with
the highest NMOC concentrations in each homogeneous area, yielding a total of six matched
pair samples. While conducting the field measurements for fixed gases at grid No. 2, it was
observed that the O2 content was greater than 18 percent and the N2 concentration was greater
than 20 percent, indicating the absence of LFG in the sample. It was determined that high
NMOC instrument reading at grid No. 2 could have been attributed to vehicle exhaust and not
to LFG due to the close proximity of this location to the roadside. It was, therefore, determined
that this sampling location shouldbe abandoned to prevent sampling interference. The sampling
location was moved to the node with the next highest screening concentration.
During the screening analysis of the site, it was observed that gas monitoring wells were
installed within the interior of the landfill boundary area. These wells were not properly capped
or sealed and were, therefore, assumed to be acting as passive vents through the landfill cover.
Sampling was conducted using a slam-bar to drive a sampling hole through the landfill cover
near these passive vents. A sampling probe was then inserted into the landfill, and the hole was
sealed around the probe to minimize ambient air in-leakage. Summa canister samples were
collected for COPC and fixed gas analysis, and Tedlar bag samples were collected for COPC
analysis. Fixed gases were also analyzed at these locations using field instrumentation. These
passive vents and sampling locations were identified at grid Nos. 80, 131, and 140.
This guidance, recommends that sampling be conducted along the perimeter at wells located
nearest to the hot spots and the closest off-site receptor. For this site demonstration, sampling
was conducted at three of the perimeter wells, which were all located in close proximity to
off-site receptors (i.e., residential houses). At each of these locations, Summa canisters and
Tedlar bags were used to collect the samples analyzed for COPC and fixed gases. The Summa
canister sampling rate was set to approximately 0.1 L/min in order to minimize the potential for
ambient air leakage. The Tedlar bag sample was collected at approximately 1.0 L/min.
This guidance recommends that ambient air sampling be conducted at the locations where
the highest NMOC concentrations are measured for each nearly homogenous area. For the
purpose of this demonstration, two samples were collected at nodes 9 and 137 using a Summa
canister. It should be noted that the sample taken at node 9 was located directly next to a storm
drain that appeared from field observations to be acting as a passive vent. An ambient air
sample was also collected at the perimeter well that was determined to be closest to the highest
concentration observed on-site during the screening analysis.
6-16
-------
Emissions from Closed or Abandoned Facilities
The laboratory did not detect any of the analytes in any sample blanks. The minimum and
maximum percent recovery for the entire set of laboratory control samples was greater than 70
and less than 122, indicating that the laboratory was capable of accurately quantifying the
results. The 4-bromofluorobenzene surrogate spike recovery was outside of the upper range for
10 out of 20 field samples; the maximum recovery was 363 percent. The high surrogate re-
covery for 4-bromofluorobenzene is indicative of matrix interference, and the results may be
biased on the high side. All other spike surrogate recovery values were within the target range
of 70 to 130 percent.
The analytical results between matrix spike and matrix spike duplicate (MS/MSD) analyses
for each COPC have been assessed. Except for methylene chloride and acetone in the duplicate
ambient air samples, the relative percent difference (RPD) for each of the matched sample pairs
ranged from 2.15 to -13.33. The laboratory reported concentrations of methylene chloride and
acetone in one of the duplicate ambient air samples but not the other. The RPD for methylene
chloride and acetone in the ambient air samples was calculated to be 40 and -129.67,
respectively. The RPD for the blind reference standard ranged from 0 to 148. The laboratory
reported concentrations for methylene chloride, acetone, and toluene in the blind reference
standard though they were not expected to be there. The reported values for the blind reference
standard are less than five times the method detection limit (MDL) for each of the contaminants.
The RPD for the laboratory control samples (LCS) ranged from 0 to 18. Except for 1,2,4-tri-
chlorobenzene and hexachlorobutadiene, the calculated RPD for each LCS analyte was less than
5. Although neither methylene chloride nor acetone was found in the associated laboratory
blanks, both of these contaminants are considered to be common laboratory contaminants. This
narrow range indicates that the laboratory was capable of reproducing the analytical results.
Completeness is a measure of the amount of valid data obtained from a measurement
system compared to the amount that was expected under normal conditions. The sampling and
analytical goal for completeness for all samples tested was 80 percent or more. Ninety-three
percent of the targeted data was collected and validated. Figure 6-7 shows the concentration
isopleth for the NMOC that was quantified by the laboratory. Figures for all ten of the COPCs
that were detected by the laboratory were generated as part of the site report. These figures
provided a visual presentation of the laboratory results and were used to help understand the
dynamics of this landfill and to further quantify the division of this landfill into two distinct
parcels. The data for individual COPCs were analyzed, and the 90th percentile concentrations
of each, shown in Table 6-8, were determined for the northern and southern homogeneous
parcels. Table 6-9 provides the analytical results for individual COPCs from the northern and
southern landfill homogeneous parcels.
The 90th percentile concentration values were used as input parameters for the LandGEM
model to estimate the emission rates for each of the COPCs. Because there were two distinct
parcels, it was necessary to model each parcel individually for NMOC emissions. With all
values input for each nearly homogeneous area, LFG emission rates for each COPC were
estimated using the LandGEM model. Figure 6-8 shows an example output file for NMOC
emissions from the LandGEM model, and Figure 6-9 shows the emission rate data for NMOC
as a function of time. Table 6-10 provides the emission rates estimated for each COPC within
each parcel of the landfill.
6-17
-------
Guidance for Evaluating Landfill Gas
4594400
4594350
4594300
4594250 it
4594200
4594150
45941
4594050
4594000
4593950
4593900
4593850
459:
291200 291250 291300 291350 291400 291450 291500 291550 291600 291650 291700 291750 291800 291850 291900 291950 292000
Figure 6-7. Rose Hill - NMOC Concentration (ppmv) Isopleths from Summa Sampling.
Table 6-8. Rose Hill - 90th Percentile Concentrations for Individual COPCs from the Northern
and Southern Homogeneous Parcels.
Northern Parcel
Southern Parcel
cures
Jlg/m3
NMOC
1,1,1 -Trichloroethane
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Toluene
Trichloroethene
Vinyl Chloride
m, p -Xylene
o-Xylene
2
3
5
1
7
6
4
3
1
2
4
.25 >
,21>
,33>
,04>
,94>
,16>
,28>
,41>
,61>
,97>
,85>
<10+6
<10+3
<10+3
<10+3
<10+3
<10+2
<10+3
<10+2
<10+3
<10+4
<10+3
ppmv
4500
0.58
1.64
0.222
2.96
0.1008
1.118
0.0625
0.62
6.73
1.1
Jlg/m3
1
7
3
8
1
9
1
7
1
.27>
,86>
,38>
.59>
,14>
.76>
,49>
.78>
.65 >
608 x
<10+6
<10+2
<10+3
<10+2
<10+3
<10+3
<10+2
<10+2
<10+4
:10+3
ppmv
2550
0.242
0.719
0.3202
0.1864
2.5473
0.02741
0.2992
3.75
1.542
6-18
-------
6'9- Rose Hill - Analytical Results
QM
—
Parcel ± >?
o ^
h^- ^1
No. (%)
Northern 137 0.19
148 4.1
139 ND
140 1.8
131 ND
Southern 15A 1.6
9 0.97
16 ND
80 0.38
^ C
0 £
Z §
(%) (%)
1.2 56
67 7.8
0.31 56
44 23
5.2 53
79 ND
66 11
1.4 63
19 43
for Individual COPCs.
7s
*^j
o
5
o
42
i«
u
(%)
42
21
43
31
43
21
24
38
38
a
42
(_; "8
O *"
2 °
z 3
^
H
i-H
Cv
i-H
(ppmv) (ppmv)
3300 NDa
3600 ND
2400 ND
2200 ND
5100 0.58
560 ND
1100 ND
2700 ND
2200 ND
qj
a
o>
N
it
PQ
(ppmv)
1.40
0.19
1.80
0.14
0.58
ND
0.17
0.094
0.26
o>
qj
N
o
_o
42
u
H
(ppmv)
ND
ND
0.07
ND
0.02
0.0041
ND
ND
0.03
it
T3
*c
Q
42
s^
e
^
(ppmv)
ND
0.80
0.12
0.20
0.17
ND
0.022
ND
0.33
s
—
^
o.
Cv
c
(ppmv)
7.90
ND
3.50
0.50
4.00
0.0042
0.63
1.3
4.8
m
3
o'
D
o ®
Q.
0
D-
(ppmv) =
0.46 °
(D
0.09 Q.
1.10 ?
0.30 §;
1.10 w
ND
0.11
0.051
1.9
3 ND = Not detected
-------
Guidance for Evaluating Landfill Gas
Model Parameters
Lo : 170.00 mA3/Mg***** User Mode Selection*****
k : 0.0500 1/yr ***** User Mode Selection *****
NMOC : 4500.00 ppmv ***** User Mode Selection *****
Methane : 56.0000 % volume
Carbon Dioxide : 44.0000 % volume
Landfill Parameters
Landfill type : Co-Disposal
Year Opened : 1967 Current Year : 2003 Closure Year: 1982
Capacity : 197692 Mg
Average Acceptance Rate Required from
Current Year to Closure Year : 13179.47 Mg/year
Model Results
NMOC Emission Rate
Year Refuse In Place (Mg) (Mg/yr) (Cubic m/yr)
1968 1.318E+04 3.227E+00 9.002E+02
1969 2.636E+04 6.296E+00 1.757E+03
1970 3.954E+04 9.216E+00 2.571E+03
1971 5.272E+04 1.199E+01 3.346E+03
1972 6.590E+04 1.463E+01 4.083E+03
1973 7.908E+04 1.715E+01 4.784E+03
1974 9.226E+04 1.954E+01 5.451E+03
1975 1.054E+05 2.181E+01 6.085E+03
1976 1.186E+05 2.398E+01 6.689E+03
1977 1.318E+05 2.603E+01 7.263E+03
1978 1.450E+05 2.799E+01 7.809E+03
1979 1.582E+05 2.985E+01 8.328E+03
1980 1.713E+05 3.162E+01 8.822E+03
1981 1.845E+05 3.331E+01 9.292E+03
1982 1.977E+05 3.491E+01 9.739E+03
1983 1.977E+05 3.321E+01 9.264E+03
2001
2002
2003
2201
2202
2203
1.977E+05
1.977E+05
1.977E+05
1.977E+05
1.977E+05
1.977E+05
1.350E+01
1.284E+01
1.222E+01
6.129E-04
5.830E-04
5.546E-04
3.766E+03
3.583E+03
3.408E+03
1.710E-01
1.627E-01
1.547E-01
Figure 6-8. Rose Hill - Example LandGEM Model Run Output.
6-20
-------
Emissions from Closed or Abandoned Facilities
o
1965 1985 2005 2025 2045 2065 2085 2105 2125 2145 2165 2185 2205
Time (yr)
Figure 6-9. Rose Hill - NMOC Emission Rates versus Time.
Table 6-10. Rose Hill - Emission Rates of COPCs by Homogeneous Parcel.
COPC
NMOC
1,1,1 -Trichloroethane
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Toluene
Trichloroethene
Vinyl Chloride
m, p-Xylene
o-Xylene
Northern Parcel
2002 Emission Rates,
Mg/yr
12.84
2.562xlQ-3
4.243 xlO'3
8.200xlQ-4
6.324xlQ-3
4.868xlQ-4
3.417xlQ-3
2.610xlQ-4
1.283xlQ-3
2.366xlQ-2
3.867xlQ-3
Southern Parcel
2002 Emission Rates,
Mg/yr
6.907
5.893xlQ-4
2.547xlQ-3
6.489xlQ-4
8.779xlQ-4
7.385xlQ-3
1.239xlQ-4
5.893xlQ-4
1.251xlQ-2
5.139xlO-3
6-21
-------
Guidance for Evaluating Landfill Gas
The next step in characterizing the LFG emissions is to evaluate the ambient impact of each
of the COPCs. For this, it is necessary to use an atmospheric dispersion model. For demonstra-
tion purposes, SCREENS was used to provide a screening level assessment. In order to
properly screen the landfill each parcel was again evaluated separately by treating each as an
"area" source within the model. In order to accomplish this, each parcel was broken into its own
rectangular area as shown in Figure 6-10. From these areas, each parcel was modeled at a unity
emission rate of 1 g/s to provide maximum 1-h concentration for each parcel. Because each
parcel was modeled on a unity basis, the emission rates generated by the LandGEM model
could, in turn, be multiplied by this unity-derived concentration to determine the 1-h max-
imum concentrations for each COPC. To convert these concentrations to a representative annual
concentration, all derived 1-h concentrations were multiplied by the appropriate multiplying
factor of 0.08.
4594400
4594350
4594300
4594250
4594200
4594150
4594100
4594050
4594000
4593950
4593900
4593850
4593800
291200 291250 291300 291350 291400 291450 291500 291550 291600 291650 291700 291750 291800 291850 291900 291950 292000
Figure 6-10. Rose Hill - Defined Modeling Areas for SCREENS .
Table 6-11 provides the maximum predicted annual concentrations for each COPC. For
illustrative purposes, it was decided to use only the 2002 emission rates for calculating the
ambient air concentrations because the LandGEM model runs for the Rose Hill Landfill
predicted very low emission rates and the emission rate for every COPC was declining from
2002 forward. Hence. These predicted ambient air concentrations were then compared to the
target concentrations presented in Table 6-12, which identifies target media concentrations
o inner]
Strata
6-22
-------
Emissions from Closed or Abandoned Facilities
corresponding to risk/hazard based concentrations for ambient air in residential settings. The
target concentrations were derived using Equation 2-8 and the appropriate toxicity factor. Only
air concentrations that satisfy both the prescribed cancer risk level and the target hazard index
are included in the risk table. The approach described here also can be used to evaluate
chemicals not listed in the tables. The reader is cautioned to recognize that the concentrations
presented in the risk table are screening levels. They are not clean-up levels, preliminary
remediation goals, nor are they intended to supercede existing criteria of the lead regulatory
authority. The lead regulatory authority for a site may determine that criteria other than those
provided herein are appropriate for their specific site or area.
Table 6-11. Rose Hill - Maximum Annual Concentrations.
Predicted Maximum Annual Concentrations
COPC Northern Parcel Southern Parcel Total
(ppmv) (|ig/m3)
NMOC
1,1,1 -Trichloroethane
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Toluene
Trichloroethene
Vinyl Chloride
m, p-Xylene
o-Xylene
2
8
1
1
5
5
3
3
3
5
0.162
.92x10
.23x10
.10x10
.48x10
.01x10
.62x10
.02x10
.11x10
.38x10
.52x10
-6
-6
-6
-5
-7
-6
-7
-6
80.
1.61x
2.67x
5.16x
3.98x
3.06x
2.15x
1.64x
8.08x
8
io-2
io-2
io-3
io-2
io-3
io-2
io-3
io-3
-5 0.149
-6
2.43x
io-2
(ppmv) (|ig/m3) (|ig/m3)
7.69>
1.01>
3.02>
1.35>
7.98>
1.07>
1.26>
1.26>
1.58>
6.49>
<10'2
3.00>
1.93>
4.34>
7.95>
6.26>
2.33>
1.14>
<10'2
The sources of chemical data used in the calculations necessary to create Table 6-11 were
EPA's Superfund Chemical Data Matrix (SCDM) database and EPA's Water 9 database
whenever a chemical was not included in the SCDM database. EPA's IRIS is the preferred
source of carcinogenic unit risks and non-carcinogenic reference concentrations (RfCs) for
inhalation exposure. The following two sources were consulted, in order of preference, when
IRIS values were not available: provisional toxicity values recommended by EPA's NCEA and
EPA's HEAST. If no inhalation toxicity data could be obtained from IRIS, NCEA, or HEAST,
extrapolated unit risks and/or RfCs were derived by using toxicity data for oral exposure
(cancer slope factors and/or reference doses, respectively) from these reference sources using
the same preference order. It is recognized that toxicity databases such as IRIS are constantly
being updated; this table is current as of August 2002. Users of this guidance are strongly
encouraged to research the latest toxicity values for contaminants of interest from the sources
noted above.
6-23
-------
Guidance for Evaluating Landfill Gas
Table 6-12. Rose Hill - Risk Assessment Analysis.
COPC
1,1,1 -Trichloroethane
Benzene
Chlorobenzene
Chloroethane (ethyl chloride)
1 ,4-Dichlorobenzene
Toluene
Trichloroethylene
Vinyl chloride (chloroethene)
m, p-Xylene
o-Xylene
Basis of
Target
Concen-
tration
risk
NCa
Cb
NC
C
c
NC
C
c
NC
NC
Target Ambient Air Concentration
to Satisfy Both the Prescribed Risk
Level and the Target Hazard Index
[R=106,HI=l)Ctarget
Cancer
(Hg/m3)
0.25
2.3
31.
i.vxio-2
0.11
Non-cancer
(^Ig/m3)
2.3xlO+3
0.31
62.
1.0xlO+4
8.4xlO+2
4.0xlO+2
37.
1.0xlO+2
l.lxlO+2
l.lxlO+2
Total Predicted
Ambient Air
Concentrations
(^Ig/m3)
1.6xlO-2
3.0xlO-2
1.9xlQ-2
4.3xlQ-2
7.9xlQ-3
6.3xlO-2
2.3xlQ-3
l.lxlO'2
0.22
5.3xlO-2
a NC = non-cancer
b C = cancer risk
The predicted ambient air concentrations in the table are risk-based screening levels
calculated following an approach consistent with that presented in EPA 2001. Separate
carcinogenic and non-carcinogenic target concentrations were calculated for each compound
when both unit risks and reference concentrations were available. When inhalation toxicity
values were not available, unit risks and/or reference concentrations were extrapolated from oral
slope factors and/or reference doses, respectively. For both carcinogens and non-carcinogens,
target air concentrations were based on an adult exposure scenario and assume maximum
exposure of an individual (i.e., exposure to contaminants 24 hours per day, 7 days per week, 50
weeks per year over 30 years). An inhalation rate of 20 nrVday and a body weight of 70 kg are
assumed and have been factored into the inhalation unit risk and reference concentration
toxicity values. For comparative purposes, approximately 12 COPCs were identified in one or
more of the ambient air samples that were collected approximately 3 feet above ground level
at a location that was known or suspected of having LFG escaping either through a vent or
through the cover material. The maximum concentration of the ambient air samples was always
below 20 ppbv (0.3 |lg/m3).
6.3 Summary of the Bush Valley Landfill Superfund Site
The Bush Valley Landfill (landfill) Site is located in Harford County, Maryland, one mile
from the Town of Abingdon. The landfill occupies approximately 16 acres of a 29-acre parcel
of land. The Bush Declaration Natural Resources Management Area, which is a 120-acre tidal
cattail marsh, borders the site to the north, and the planned community of east Harford Town
6-24
-------
Emissions from Closed or Abandoned Facilities
lies west of the site across Bush Road. Three single-family homes are located within 300 feet
of the landfill's southern border.
The Bush Valley Superfund Landfill began operations in 1974 and took in household and
industrial wastes. The operator abandoned the site in 1983 when the landfill reached capacity.
During site investigations, several VOCs were detected, including benzene, vinyl chloride, and
tetrachloroethene. Metals including beryllium, arsenic and manganese have shown up in
samples of ground water, surface water, soil, and leachate. The VOCs have appeared in air
samples.
EPA's 1993 Human Health Risk Assessment indicates that ground water is the only
potential source of elevated risk if people are exposed to it. However, no residents currently use
ground water in the area for their drinking or cooking. This assessment was not able to rule out
air as potentially significant pathway, but additional air testing during the cleanup showed that
the air is safe to breathe.
The site was added to the NPL in 1989. The final ROD was issued in 1995, and the final
design for the remedial action was completed in 1999. The landfill was closed in 2001 with the
installation of a flexible membrane single barrier cover system. As a part of the landfill closure,
a passive LFG control system was installed. This passive system consists of 14 subsurface gas
collection points that terminate below the landfill cap into a gas transmission layer. This layer
is connected to five passive gas vent wells aligned along the ridge of the landfill. In December
2002, eight temporary gas monitoring probes (TMPs) were installed in the sand and gravel
layer that exists approximately 15 feet below ground surface. These probes confirmed that a
15-foot thick layer of clayey soil is overlaying the sand. This study effort also demonstrated
that CH4 at concentrations between 62 and 65.4 percent exists in the sand layer, and the gas
pressure within the sand layer is approximately 0.4 inches of Hg. Prior to this demonstration
project, samples from the temporary probes had not been analyzed for speciated volatile
organics. Monitoring has shown that the cap's passive gas venting system is not enough, by
itself, to reduce the levels of underground LFG to acceptable levels. For this reason, the PRPs
planned to modify the gas management system to include active gas venting. EPA approved the
design for the active venting system in April 2004, and the vents were installed in June 2005.
The landfill itself consists of a mound of covered material sloping up from the southern site
boundary. The mound peaks 25 feet above natural grade approximately in the center of the site,
and then slope downward to the north at a somewhat steeper slope than on the south side of the
site. The graded site also slopes gently to the east and west towards the marsh area and Bush
Road, respectively. The landfill is capped with a geo-synthetic capping system. The cap is
multilayered and includes:
• 2 ft of soil bedding material on top of the solid waste,
Gas transmission layer (6 oz/yd2 geotextile),
• Hydraulic barrier (40 mil low density polyethylene),
• Drainage layer (6 oz/yd2 geotextile),
• Anchor trench (3 ft run out and 2 ft deep),
• Soil cover (2 ft thick) with shallow root vegetation,
• Five LFG vents (4 in. schedule 80 PVC) along ridge line,
6-25
-------
Guidance for Evaluating Landfill Gas
Nine permanent gas monitoring probes (2-in. diameter with 3/8-in. valves), and
Five active LFG units along the eastern perimeter.
6.3.1 Bush Valley Landfill- Using the Procedure of Screening with Probes Placed
Just Below the Cover
For reasons discussed above, this site was selected in order to compare the historical
decisions concerning the number and location of the perimeter monitoring probes and the need
to control LFG with the conclusions one would reach if the guidance document procedures
were followed.
Field activities as described in the approved site activity plan for the Bush Valley Landfill
located in Abingdon, Maryland were conducted on August 25 and August 26, 2003. Field
activities included landfill surface screening analysis and data reduction, hot spot and
homogeneity determinations, and sampling landfill soil gas, passive vent gas, perimeter well
gas, and ambient air. To assist with the field activities a 30 m by 30 m sampling grid was
developed across the extent of the landfill area prior to the field activities. This sampling grid
was developed to include the entire extent of the landfill boundary area and to extend 30 m
beyond it. This grid was then numbered for each node location forming a serpentine sampling
pathway across the grid. A total of 108 sampling locations comprised the sampling grid layout
developed for this site. A reference point was identified using an identifiable landmark on the
site to locate the starting point. Figure 6-11 shows the sampling grid for the screening analysis.
Once on site, the reference point was visually located, and using a handheld GPS, the
starting point (grid node No.l) was located to begin the screening analysis. This screening
analysis encompassed measurements forNMOC using aPID and for CH4 by using a FID. Both
detectors were held no more than 1 in. above the ground while measurements were being made.
It should be noted that the field instruments are very sensitive, and fluctuation due to gusts of
wind across the landfill cover could have been significant. Readings were taken for
approximately 1 min, and the average value, excluding the extreme highs and lows, was
recorded.
In conducting the serpentine walk across the site, an effort was made to identify areas
containing cracks and gaps in the landfill cover and to the extent possible measurements were
made at those locations. As this site had previously installed passive vents, these passive vents
were including in the screening analysis as a breach in the cover. The permanent and temporary
installed gas monitoring probes were also included in these screening activities. Not all
predetermined sampling locations were accessible due to a variety of reasons, ranging from
being located on private property to extreme overgrowth. An attempt was made to collect a
reading at each node, with measurements being collected not greater than 10 m from the
predetermined locations. Duplicate readings were also taken at predefined nodes, selected
based on a random number generator, as part of the QA/QC efforts. All screening data were
recorded on field log data collection forms along with any field notes relevant to this specific
location. There was 90 percent data collection efficiency. Table 6-13 provides the screening
sample results for the first 29 nodes.
6-26
-------
to
Figure 6-11. Bush Valley - Screening Sampling Grid.
-------
Guidance for Evaluating Landfill Gas
Table 6-13. Bush Valley Screening Sample Results
Node Actual UTM
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Sample ID No.
LSFG-02-082703- R- 001
LSFG-02-082703- R- 002
LSFG-02-082703- R- 003
LSFG-02-082703- R- 004
LSFG-02-082703- R- 005
LSFG-02-082703- R- 006
LSFG-02-082703- R- 007
LSFG-02-082703- R- 008
LSFG-02-082703- R- 009
LSFG-02-082703- R- 010
LSFG-02-082703- R- Oil
LSFG-02-082703- R- 012
LSFG-02-082703- R- 013
LSFG-02-082703- R- 014
LSFG-02-082703- R- 015
LSFG-02-082703- R- 016
LSFG-02-082703- R- 017
LSFG-02-082703- R- 018
LSFG-02-082703- R- 097
LSFG-02-082703- R- 019
LSFG-02-082703- R- 020
LSFG-02-082703- R- 021
LSFG-02-082703- R- 022
LSFG-02-082703- R- 023
Easting
18391264
18391275
18391270
18391258
NAb
18391296
18391311
18391314
18391313
18391327
18391330
18391329
18391325
NA
NA
18391353
18391357
18391355
18391359
18391354
18391357
18391384
18391385
18391391
18391386
18391386
18391383
NA
NA
(partial).
Coordinates
Northing
4369160
4369193
4369221
4369252
NA
4369251
4369216
4369185
4369140
4369141
4369191
4369221
4369248
NA
NA
4369267
4369250
4369220
4369189
4369160
4369141
4369133
4369154
4369189
4369214
4369252
4369280
NA
NA
NMOC
Cone.
(ppm)
NDa
ND
ND
ND
NA
ND
ND
ND
ND
ND
ND
ND
ND
NA
NA
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
NA
NA
CH4
Cone.
(ppm)
1.29
1.29
1.05
1.58
NA
1.22
3.33
1.4
1.32
1.37
1.31
1.65
3.11
NA
NA
20.2
2.08
1.44
1.7
0.85
0.9
2.08
5.5
1.66
1.39
1.71
34
NA
NA
aND = not detected.
b NA = not available.
The screening data collected were used for two analyses. The first was for a hot spot
analysis. This was done by importing the screening data set into a graphical contouring soft-
ware package (Surfer) to produce concentration contours, which were layered over an aerial
photograph of the site. This method enabled a visual determination of where the higher
concentrations were recorded during the screening analysis. This method also allowed the data
6-28
-------
Emissions from Closed or Abandoned Facilities
to be divided into two sets based on the contours derived from these data. This population
division was used as part of the homogeneity determinations. NMOCs were only detected
within the passive vents and gas monitoring probes. Therefore, CH4 measurements were used
to identify hot spots and to determine the number of near homogeneous subdivisions required
to characterize the landfill surface. Figures 6-12 and 6-13 show the concentration contours for
both NMOC and CH4 data that were recorded during the screening analysis.
The second analysis provided a determination of the homogeneity of the site, which was
done by the Wilcoxon Rank Sum statistical method. This method determines whether two data
sets are statistically similar. If the two sets are determined to be similar, then the two
populations are determined to be one nearly homogeneous area. If the two data sets are
determined not to be statistically similar, then the two sets are said to be two non-homogeneous
areas. For this task, the hot spot analysis was used to determine if there appeared to be two
distinct population sets. For this site it was shown that there existed four nearly homogeneous
areas. All non-detect and duplicate measurements were excluded from the statistical analysis.
As part of this demonstration, landfill soil gas samples were collected for COPCs. The
samples were collected using a Summa canister and were sent to an off-site commercial
laboratory for analysis. At each of the designated sampling locations, field instruments were
used to measure fixed gases (CO2, N2, and O2). The fixed gas concentration values were used
to verify that LFG was being collected. As per the guidance, three landfill soil gas samples
should be collected in each of the four homogeneous areas, yielding a total of 12 landfill soil
gas samples required. However, a decision was made against using a slam-bar on this site in
order to prevent damage to the flexible membrane cover that was already in place and to avoid
the complexities of ensuring proper repair of damage to this cover that using a slam-bar would
cause. Instead, it was determined that LFG samples would only be collected at the installed
passive gas vents (GVW). For all GVW locations, a brass sampling valve was installed on each
vent, and the vent exit was sealed to minimize leakage during sampling activities. The duplicate
sample needed to satisfy QAPP requirements was collected at GVW 1.
As a further demonstration, sampling was conducted at all the site's 17 perimeter wells,
which were designated as gas monitoring probes (GMPs) and TMPs. Sampling was conducted
using sampling valves previously installed at each location. All 17 wells are located in close
proximity to off-site receptors (i.e., residential dwellings). At each location, Summa canisters
were used to collect the samples to be analyzed for COPCs, fixed gases, and methane. The
Summa canister sampling rate was set to approximately 0.1 L/min to minimize the potential
for ambient air leakage. Based on the fixed gas concentration data, it would appear that there
is significant ambient air leakage associated with GMP-1, GMP-5,TMP-2, TMP-3, and TMP-5.
The data from these probes was excluded from additional data analysis. It was observed that
several of these excluded locations have elevated NMOC concentration even with the ambient
air dilution. All probes had been installed for more than 7 months and some for as many as 3
years. It would appear that the grout and soils surrounding these probes had dried out and
shrunk, allowing ambient air to leak into the annulus. Field instrumentation readings taken at
each of the sampling locations prior to initiating sampling confirms this. These results
demonstrated the presence of LFG via oxygen readings at levels of 0.4 percent. This theory is
further supported in viewing the laboratory results of samples GMP-6 and TMPS and
6-29
-------
Guidance for Evaluating Landfill Gas
4369500
43694OO
4369300
4369200
43691OO
4369000
4368900
183912OO 1S3913OO 1S3914OO 1S3915OO 183916OO 183917OO 18391SOO
Figure 6-12. Bush Valley - Measured Screening Results for NMOC (ppm).
4369500
436940O
43693OO
436920O
43691OO
4369OOO
4368900
183912OO 183913OO 183914OO 183915OO 183916OO 18391TOO 183918OO
Figure 6-13. Bush Valley - Measured Screening Results for Methane (ppm).
6-30
-------
Emissions from Closed or Abandoned Facilities
comparing them to the duplicate samples collected there. In both instances these laboratory
results were nearly identical. For these reasons and because all of the existing probes were
sampled, there was sufficient data to continue with the illustration of the guidance. One Q A/QC
sample was collected at each of the GMP and TMP sampling sets. These QA/QC samples were
collected at GMP-6 and TMP-5.
Sampling was conducted of the ambient air at each of the passive vent locations (GVW).
Five samples were collected using a Summa canister. The QAPP and field activity plan required
the team to collect one duplicate ambient air Summa canister sample as a QA/QC validation.
Data quality objectives (DQOs) are a starting point of an interactive process, but they do
not necessarily constitute definitive rules for accepting or rej ecting results. Measurement quality
objectives have been defined in terms of standard methods with accuracy, precision, and
completeness goals. Uncertainty associated with the measurement data is expressed as accuracy
and precision. The accuracy of a single value contains both a random error in a measurement
and a systematic error, or bias. Accuracy thus reflects the total error for a given measurement.
Precision values represent a measure of only the random variability for replicate measurements.
In general, the purpose of calibration is to eliminate bias, although inefficient analyte recovery
or matrix interferences can contribute to sample bias, which is typically assessed by analyzing
matrix spike samples. At very low levels, blank effects (contamination or other artifacts) can
also contribute to low-level bias. The potential for bias is evaluated by the use of method
blanks. Instrument bias is evaluated by the use of control samples.
Accuracy of laboratory results has been assessed for compliance with the established QC
criteria using the analytical results of method blanks, reagent/preparation blank, matrix spike
and matrix spike duplicate samples, and field blanks. The laboratory detected 9.4 ppbv of
acetone in a trip blank. This value is less than five times the value found in the sample results.
The minimum and maximum percent recovery for the entire set of laboratory control samples
was greater than 94 and less than 152. Out of 159 values, 154 were within the QC limits, and
the data are deemed acceptable. The 4-bromofluorobenzene surrogate spike recovery was
outside of the upper range for 56 field samples. The maximum 4-bromofluorobenzene sur-
rogate spike recovery was 152 percent. The high 4-bromofluorobenzene surrogate recovery is
indicative of matrix interference, and the results may be biased on the high side. All other spike
surrogate recovery values were within the target range of 70 to 130 percent. The concentration
of hexane in one sample exceeded the linear calibration range, and the value is assumed to be
a lower end estimate.
The analytical results between MS/MSD analyses for each COPC have been assessed. The
RPD was calculated for each pair of duplicate analysis. Methyl ethyl ketone (MEK) was
reported in one of the duplicate ambient air samples, but not both. Chloroethane was reported
in one of the duplicate GMP-6 samples, but not both. MEK, xylene, and dichloroethane (DCA)
were reported for one of the duplicate TMP-5 samples, but not the other. The RPD for the
duplicate samples ranged from -0.6 to 28.5, indicating that the laboratory was capable of
reproducing the analytical results. Acetone was reported in the trip blank at 9.4 ppbv. Acetone
in the LFG samples ranged from non-detect to 750 ppbv. Acetone is a common laboratory
contaminant, and samples with concentrations less than five times that in the method/trip blank
6-31
-------
Guidance for Evaluating Landfill Gas
should be considered to be estimates.
The sampling and analytical goal for completeness is 80 percent or more for all samples
tested. Seventy-three percent of the targeted data was collection and validated. This is less than
the DQO of more than 80 percent. The DQO was not achieved because of the air leakage
problem discussed above.
From previous site activities and visual inspection of concentration isopleths generated from
the laboratory results, the data were divided into the appropriate homogenous groups (corres-
ponding to a parcel of land) for analysis. Figures 6-14 and 6-15 show the concentration
isopleths of selected COPCs. These figures are a visual presentation of the laboratory results
and were used to further understand the dynamics of this landfill and to quantify the division
of this landfill into four distinct parcels. Table 6-14 provides the analytical results for GVW,
GMP, and TMP sampling in the four homogeneous landfill parcels. For each parcel, the
analytical results for each COPC were analyzed, and the 90th percentile concentrations shown
in Table 6-15 were determined.
These data were used as input values for the LandGEM model to estimate the LFG emission
rates for each COPC. It was necessary to model each of the four landfill parcels individually
for CH4 emissions. Figure 6-16 shows an example output file for NMOC emissions from the
LandGEM model. Figure 6-17 shows the emission rate data for NMOC versus time. Table 6-16
provides the emission rates estimated for each COPC within each parcel of the landfill.
The next step in characterizing the emissions of LFG is to use an atmospheric dispersion
model to evaluate the ambient impact of each of the COPCs. For demonstration purposes,
SCREENS was used to provide a screening level assessment. In order to properly screen the
landfill, each parcel shown in Figure 6-18 was evaluated separately and treated as an area
source within the model. Each parcel was modeled at a unity emission rate of 1 g/s to obtain a
1-h concentration. Because each parcel was modeled on a unity basis, the emission rates
generated from the LandGEM model could, in turn, be multiplied by this unity-derived
concentration to determine the 1-h maximum concentrations for each COPC. To convert these
concentrations to a representative annual concentration, all 1-h concentrations were multiplied
by the appropriate multiplying factor of 0.08. Table 6-17 provides the predicted maximum
annual concentrations for each COPC.
This time averaged emission rate is entered into the atmospheric dispersion model to
estimate the average exposure point concentration of each COPC. Using this approach, a
dispersion model run will be required for each chemical of concern. The dispersion model will
generate a normalized air concentration at the receptor of concern if the model is run at 1
g/m2-s. The estimated ambient air concentration is determined by multiplying the dispersion
coefficient by the time averaged emission rate. The LandGEM model runs for the Bush Valley
Landfill predicted very low emission rates, and the emission rate for every COPC declines from
2003 forward. Hence, for illustrative purposes, only the 2003 emission rates were used for
calculating the ambient air concentrations. These predicted ambient air concentrations were
summed to identify the worst-case scenario and then compared to the target concentrations
presented in Table 6-17.
6-32
-------
Emissions from Closed or Abandoned Facilities
43695OO
43694OO
4369300
43692OO
43691OO
4369OOO
4368900
18391200 18391300 183914OO 183915OO 183916OO 183917OO 183918OO
Figure 6-14. Bush Valley - NMOC Concentration (ppmvC) Isopleths from Summa Sampling.
43695OO
43694OO
43693OO
43692OO
43691OO
4369OOO
43689OO
183912OO 1S3913OO 183914OO 1S3915OO 183916OO 183917OO 183918OO
Figure 6-15. Bush Valley - 1,1-Dichloroethene Concentration (ppmv) Isopleths from Summa
Sampling.
6-33
-------
Table 6-14. Bush Valley - Analytical Results for Individual COPCs.
o
0.
1
2
Q
HH
e
_o
-4^
«
o
O
-J
_aj
"a,
VI
GVW-4
GVW-5
GMP-2
GMP-3
GVW-3
g
e
OK
M
O
0.30
037
ND
0.25
0.24
o
Z
0.88
1 00
0.55
0.80
0.70
Methane (%)
64.00
62.00
62.00
63.00
62.00
Carbon Dioxide (%)
37.00
40.00
38.00
38.00
36.00
I
o.
U
0
Z
2200.00
2200.00
1900.00
2000.00
2000.00
1,1-Trichloroethane (ppmv
Cs
i-H
NDa
ND
0.09
ND
ND
i
o.
e
-*^
o
_o
u
5
Cs
i-H
ND
ND
0.03
0.01
ND
i
o.
o.
e
"S
o
_o
5
i-H
ND
007
ND
ND
ND
i
o.
e
N
e
0.72
067
2.50
0.95
0.31
i
o.
s&
T3
_O
•_
-*^
O
.Q
cS
U
ND
ND
ND
ND
ND
o.
e
N
e
o
_o
6
0.19
075
ND
0.31
0.21
i
o.
e
«
o
_o
6
0.16
010
0.43
0.60
0.16
o.
|
o
6
ND
ND
ND
ND
ND
4-Dichlorobenzene (ppmv)
Cs
i-H
0.32
014
0.20
0.17
0.29
o.
T3
_O
U
e
^
ND
008
0.20
0.13
ND
o.
e
-*^
o
_o
u
«
•s
H
ND
009
0.31
0.68
ND
Toluene (ppmv)
Trichloroethene (ppmv)
4.00 ND
13.00 0.08
0.18 0.27
ND 0.67
0.55 ND
o.
."2
_o
o
_C
0.55
370
1.40
0.88
0.22
o.
e
o.
5.90
960
0.45
ND
8.00
o.
e
o
1.70
790
0.18
ND
2.40
GVW-1 0.42 1.20 63.00 36.00 2100.00 ND ND 0.09 0.41 ND 0.41 0.12 ND 0.18 0.06 0.06 3.40 0.07 0.12 10.00 1.30
GMP-7 1.00 34.00 36.00 27.00 860.00 ND 0.02 ND 0.05 ND ND 0.10 ND ND 0.01 0.08 ND 0.35 0.32 ND ND
GMP-8 0.21 1.70 68.00 32.00 1400.00 ND ND 0.05 0.07 ND ND 0.19 ND 0.02 ND ND 0.02 0.10 1.10 ND ND
3 GMP-9 1.50 49.00 34.00 15.00 690.00 ND ND ND ND ND ND 0.03 ND ND ND ND ND 0.03 0.07 ND ND
TMP-1 3.60 12.00 54.00 31.00 1400.00 ND 0.03 0.27 0.22 ND 0.15 0.18 ND 0.03 1.30 1.10 0.03 1.00 0.53 0.08 0.04
TMP-7 0.24 1.70 64.00 37.00 1600.00 0.03 0.04 0.22 0.19 ND 0.31 0.26 ND 0.09 0.49 1.20 0.01 1.4 0.61 0.02 0.04
TMP-8 0.47 7.90 60.00 33.00 1300.00 ND 0.04 0.28 0.40 ND 0.13 0.15 ND 0.03 2.20 1.30 0.12 1.00 0.43 0.30 0.13
GVW-2 0.46 1.50 64.00 36.00 1500.00 ND ND ND 0.42 ND 0.17 0.29 ND 0.03 ND ND 0.08 ND 0.05 1.60 0.39
GMP-4 1.20 8.40 57.00 38.00 1900.00 ND ND ND 0.94 ND 0.18 0.28 ND 0.06 ND 0.80 0.13 0.84 0.93 0.48 0.07
TMP-4 0.27 1.20 64.00 39.00 1800.00 0.05 0.04 0.10 0.60 ND 0.23 0.49 ND 0.09 0.18 0.72 0.08 0.72 0.48 0.11 0.10
TMP-6 0.19 0.72 64.00 36.00 1700.00 ND 0.03 ND 0.45 ND 0.18 0.00 ND 0.06 0.10 0.92 0.05 0.75 0.66 0.09 0.02
1 ND = not detected
-------
oo
. Bush Valley - 90th
COPC
NMOC
Percentile Concentrations
Parcel
(^lg/m3)
1.10xlO+6
1,1,1-Trichloroethane 515.
1 , 1 -Dichloroethene
1 ,2-Dichloroethane
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Methylene chloride
Tetrachloroethene
Toluene
Trichloroethene
Vinyl chloride
m, p -Xylene
o-Xylene
103.
280.
6610.
1400.
1470.
1740.
657.
4180.
4.29xlO+4
3220.
6920.
3.91xlO+4
1.17xlO+4
1
(ppmv)
2200
0.093
0.0255
0.068
2.035
0.298
0.549
0.284
0.186
0.606
11.2
0.59
2.66
8.86
2.66
for Individual COPCs.
Parcel 2
(|0,g/m3) (ppmv)
9.98xlQ-5 2000
1010. 0.31
987. 0.21
429. 0.16
1770. 0.29
2110. 0.55
572. 0.22
3.53xlO+4 8
1.06xlO+4 2.4
Parcel
(^g/m3)
8.99xlQ-5
166.
152.
1140.
1300.
1790.
585.
881.
6500.
8700.
8000.
6320.
2100.
3.13xlO+4
4180.
3
(ppmv)
1800
0.03
0.0378
0.276
0.405
0.38
0.218
0.144
1.84
1.26
2.088
1.16
0.806
7.09
0.949
Parcel
(Hg/m3)
9.33xlQ-5
282.
171.
412.
2720.
1010.
1150.
503.
607.
6190.
439.
4480.
2210.
5570.
1330.
4
(ppmv)
1870
0.051
0.0424
0.1
0.838
0.215
0.43
0.0822
0.1718
0.896
0.1147
0.822
0.849
1.264
0.3024
m
3
o'
D
-h
O
3
O
0
(D
Q.
o
D)
3
Q.
O
(D
Q.
D)
O_
§:
tt
-------
Guidance for Evaluating Landfill Gas
Model Parameters
Lo: 170.00 mA3/Mg
k : 0.0500 1/yr
NMOC : 2200.00 ppmv
Methane : 64.0000 % volume
Carbon Dioxide : 36.0000 % volume
Landfill Parameters
Landfill type : Co-Disposal
Year Opened : 1974 Current Year : 2004 Closure Year: 2004
Capacity: 303128 Mg
Average Acceptance Rate Required from
Current Year to Closure Year : 0.00 Mg/year
Model Results
NMOC Emission Rate
Year Refuse In Place (Mg) (Mg/yr) (Cubic m/yr)
1975
1976
1977
1978
1979
1980
1981
1982
1983
2001
2002
2003
2201
2202
2203
3.031E+04
6.063E+04
9.094E+04
1.213E+05
1.516E+05
1.819E+05
2.122E+05
2.425E+05
2.728E+05
3.031E+05
3.031E+05
3.031E+05
3.031E+05
3.031E+05
3.031E+05
3.175E+00
6.195E+00
9.067E+00
1.180E+01
1.440E+01
1.687E+01
1.922E+01
2.146E+01
2.359E+01
1.095E+01
1.041E+01
9.906E+00
4.970E-04
4.728E-04
4.497E-04
8.857E+02
1.728E+03
2.530E+03
3.292E+03
4.017E+03
4.707E+03
5.363E+03
5.987E+03
6.581E+03
3.054E+03
2.905E+03
2.764E+03
1.387E-01
1.319E-01
1.255E-01
Figure 6-16. Bush Valley - Example LandGEM Model Run Output.
6-36
-------
Emissions from Closed or Abandoned Facilities
Tl
25 - 1
^ ,5- 1 \
1965 1985 2005
Figure 6-17. Bush Valley
Table 6-1 6. Bush Valley -
COPCs
NMOC
1,1,1 -Trichloroethane
1 , 1 -Dichloroethene
1 ,2-Dichloroethane
Benzene
Carbon tetrachloride
Chlorobenzene
Chloroethane
Chloroform
1 ,4-Dichlorobenzene
Methylene chloride
Tetrachloroethene
Toluene
Trichloroethene
Vinyl chloride
m,p-Xylene
o-Xylene
^^
2025 2045 2065 2085 2105
Time (yr)
- NMOC Emission
Emission Rates of
Parcel 1
2003
(Mg/yr)
9.91
6.27xlO-4
1.52xlO-4
3.62xlO-4
8.33xlQ-3
1.76xlO-3
1.85xlQ-3
2.15xlO-3
8.43xlQ-4
5.29xlQ-3
5.39xlO-2
4.05 xlO'3
8.69xlQ-3
4.92xlQ-2
1.48xlO-2
2125 2145
2165 2185 2205
Rates versus Time.
COPCs by
Parcel 2
2003
(Mg/yr)
1.48
2.08xlO-4
2.03xlO-4
8.88xlQ-5
3.67xlQ-4
4.36xlQ-4
1.18xlO-4
7.30xlQ-3
2.19xlO-3
Parcel.
Parcel 3
2003
(Mg/yr)
1.38
3.55xlQ-5
3.44xlQ-5
2.46xlQ-4
2.84xlQ-4
3.79xlQ-4
1.26xlQ-4
1.82xlQ-4
1.39xlQ-3
1.85xlQ-3
1.71xlQ-3
1.35xlQ-3
4.49xlQ-4
6.67xlQ-3
8.94xlQ-4
Parcel 4
2003
(Mg/yr)
8.54
3.54xlQ-5
2.06xlO-5
5.25xlQ-5
3.48xlQ-4
1.31xlQ-4
1.47xlQ-4
6.23 xlO-5
7.65xlQ-5
7.91xlQ-4
5.37xlQ-5
5.71xlQ-4
2.82xlQ-4
7.09xlO-4
1.69xlQ-4
6-37
-------
00
Figure 6-18. Bush Valley - Defined Modeling Areas for SCREENS.
-------
VO
'•17. Bush Valley - Maximum Predicted Ambient Air Annual Concentrations.
Parcel
COPC
Methane
Carbon Dioxide
NMOC
1,1,1 -Trichloroethane
1 , 1 -Dichloroethene
1 ,2-Dichloroethane
Benzene
Chlorobenzene
Chloroethane
1 ,4-Dichlorobenzene
Methylene chloride
Tetrachloroethene
Toluene
Trichloroethene
Vinyl chloride
m, p -Xylene
o-Xylene
(ppmv)
9.41 xlO'7
3.13xlO-7
7.29xlO-7
2.13xlO-5
3.11xlO-6
5. 73 xlO-6
2.92xlQ-6
1.98xlQ-6
6.35xlQ-6
1.17xlO-4
6.17xlO-6
2.77xlO-5
9.25 xlO-5
2.78xlO-5
5
1
3
6
1
1
1
6
1
(Hg/m3)
4449.
6867.
82.17
.204 xlO-3
.260xlQ-3
.002 xlO-3
.907xlQ-2
.463 xlO-2
.538xlQ-2
.783xlQ-2
.991 xlO-3
Parcel 2
(ppmv) (|4,g/m3)
1102.
1854.
19.11
0.000
0.000
0.000
8.26xlQ-7 2.684xlQ-3
5.57xlQ-7 2.620xlQ-3
4.26xlQ-7 1.144xlQ-3
7.73 xlQ-7 4.725 xlQ-3
4.384xlQ-2
3
7
0.4473
.360xlQ-2
.205 xlO-2
0.4077
0.1224
1.47xlQ-6 5.617xlQ-3
5.86xlQ-7 1.524xlQ-3
2.14xlO-5 9.415xlQ-2
6.14xlO-6 2.825xlQ-2
Parcel 3
(ppmv)
8.94xlQ-8
1.19xlQ-7
8.32xlQ-7
1.22xlQ-6
1.12xlO-6
6.54xlQ-7
4.16xlQ-7
5.47xlQ-6
3.74xlQ-6
6.21 xlO-6
3. 46 xlO-6
2.41 xlO-6
2.11xlO-5
2.83xlQ-6
Parcel 4
(|Ig/m3) (ppmv)
1301.
1871.
19.17
4.948xlQ-4
4.793xlQ-4
3.425xlQ-3
3.959xlQ-3
5.288xlQ-3
1.754xlQ-3
2.544xlQ-3
1.931xlQ-2
2.583xlQ-2
2.380xlQ-2
1.884xlQ-2
6.258xlQ-3
9.305xlQ-2
1.247xlQ-2
1.47xlQ-7
1.17xlQ-7
2.93>
2.46>
6.42>
1.26>
2.34>
4.98>
2.63>
3.22>
2.41>
2.49>
3.7x
8.8x
D)
3
Q.
0
3
(D
Q.
Tl
D)
O
§
-------
Guidance for Evaluating Landfill Gas
Table 6-18 identifies target media concentrations corresponding to risk/hazard based
concentrations for ambient air in residential settings. Only air concentrations that satisfy both
the prescribed cancer risk level and the target hazard index are included in this table. The
approach described here also can be used to evaluate chemicals not listed in the tables. The
reader is cautioned to recognize that the concentrations presented in Table 6-18 are screening
levels. They are not clean up levels, or preliminary remediation goals, nor are they intended to
supercede existing criteria of the lead regulatory authority. The lead regulatory authority for a
site may determine that criteria other than those provided herein are appropriate for their
specific site or area.
Table 6-18. Bush Valley - Risk Assessment Analysis.
Target Ambient Air
Concentration to
Satisfy Both the
Basis of Prescribed Risk Level Total Predicted
CAS „, . . „ anH the Tareet Hazard Ambient Air
Chemical Target anu uie x arsei na^aru
No. „ f ,. Index Concentrations
Concentration muex
(R=10 6, HI=1) C
target
Cancer Non-cancer
(|ig/m3) (|ig/m3)
71556
75354
107062
71432
108907
75003
106467
75092
127184
108883
79016
75014
108383
95476
1,1,1 -Trichloroethane
1 , 1 -Dichloroethylene
1 ,2-Dichloroethane
Benzene
Chlorobenzene
Chloroethane (ethyl chloride)
1 ,4-Dichlorobenzene
Methylene chloride
Tetrachloroethylene
Toluene
Trichloroethylene
Vinyl chloride (chloroethene)
m, p-Xylene
o-Xylene
NCa
NC
Cb
C
NC
C
C
C
C
NC
C
C
NC
NC
7.4xlQ-2
0.25
2.3
0.31
4.1
0.32
1.7xlQ-2
0.11
2.2xlO+3
2.0xlO+2
9.4xlQ-2
0.31
60.
1.0xlO+4
8.0xlO+2
5.2
0.81
4.0xlO+2
37.
1.0xlO+2
l.lxlO+2
l.lxlO+2
6.5xlQ-3
2.2xlQ-3
7.6xlQ-3
8.4xlQ-2
2.6xlQ-2
2.2xlQ-2
2.7xlQ-2
2.8xlQ-2
8.8xlQ-2
0.48
6.6xlQ-2
8.6xlQ-2
0.61
0.17
a NC = non-cancer risk.
b C = cancer risk.
The sources of chemical data used in the calculations necessary to create Table 6-18 were
EPA's Superfund Chemical Data Matrix (SCDM) database or EPA's Water 9 database
whenever a chemical was not included in the SCDM database. EPA's IRIS is the preferred
source of carcinogenic unit risks and non-carcinogenic RfCs for inhalation exposure. The
following two sources were consulted, in order of preference, when IRIS values were not
available: provisional toxicity values recommended by EPA's NCEA and EPA's HEAST. If
no inhalation toxicity data could be obtained from IRIS, NCEA, HEAST, extrapolated unit risks
6-40
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Emissions from Closed or Abandoned Facilities
and/or RfCs were derived by using toxicity data for oral exposure (cancer slope factors and/or
reference doses, respectively) from these reference sources using the same preference order. It
is recognized that toxicity databases such as IRIS are constantly being updated; this table is
current as of August 2002. Users of this guidance are strongly encouraged to research the latest
toxicity values for contaminants of interest from the sources noted above.
The ambient air concentrations in the table are risk-based screening levels calculated
following an approach consistent with that presented in EPA 2001. Separate carcinogenic and
non- carcinogenic target concentrations were calculated for each compound when both unit
risks and reference concentrations were available. When inhalation toxicity values were not
available, unit risks and/or reference concentrations were extrapolated from oral slope factors
and/or reference doses, respectively. For both carcinogens and noncarcinogens, target air
concentrations were based on an adult exposure scenario and assume maximum exposure of an
individual (i.e., exposure to contaminants 24 hours per day, 7 days per week, over 70 years).
An inhalation rate of 20 m3/day and a body weight of 70 kg are assumed and have been factored
into the inhalation unit risk and reference concentration toxicity values.
6-41
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6-42
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Emissions from Closed or Abandoned Facilities
References
API. 1998. "Assessing the Significance of Subsurface Contaminant Vapor Migration to
Enclosed Spaces; Site-specific Alternatives to Generic Estimates," American Petroleum
Institute, December.
EQ. 2004. "User's Guide for the Johnson and Ettinger (1991) Model for Subsurface Vapor
Intrusion Into Buildings (Revised)," Environmental Quality Management, Inc., EPA Contract
No. 68D70002, Work Assignment No. 3-003, February.
Johnson, P.C., and R.A. Ettinger. 1991. "Heuristic model for predicting the intrusion rate of
contaminant vapors into buildings," Environ. Sci. Technol., 25:1445-1452.
Lindberg, S. E., and J. Price. 1999. "Measurements of the Airborne Emissions of Mercury from
Municipal Landfill Operations," J. Air and Waste Manag. Assoc., 49(5): 520-532.
Little, J.C., J.M. Daisey, and W.W. Nazaroff 1992. "Transport of subsurface contaminants into
buildings" Environ. Sci. TechnoL, 26(11):2058-2066.
Schaap, M.G., and F. J. Leij. 1998. "Database Related Accuracy and Uncertainty of Pedotransfer
Functions," Soil Science, 163(10):765-779.
SWANA. 2000. "A Review of the Literature Regarding non-Methane and Volatile Organic
Compounds In Municipal Solid Waste Landfill Gas," Solid Waste Association of North
America, Intern Program Monograph Series.
Tchobanoglous, G.; Theisen, H.; and Vigils, 1993. Integraged Solid Waste Management,
Engineering Principles and Management Issues, McGrawHill, Inc., New York, pp. 381-417.
U.S. EPA. 1989. CERCLA Compliance with Other Laws Manual, Part II, Clean Air Act and
Other Environmental Statutes and State Requirements, EPA/540/G-89/009 (NTIS PB90-
148461), U.S. Environmental Protection Agency, Office of Solid Waste and Emergency
Response, August.
U.S. EPA. 1991. Air Emissions from Municipal Solid Waste Landfills: Background Information
for Proposed Standards and Guidelines, EPA-450/3-90-011a (NTIS PB91-197061), U.S.
Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, March.
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Guidance for Evaluating Landfill Gas
U.S. EPA. 1992a. Workbook of Screening Techniques for Assessing Impacts of Toxic air
Pollutants (Revised), EPA-454/R-92-024 (NTIS PB93-210367), U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC, December.
U.S. EPA. 1992B Assessing Potential Indoor Air Impacts for Superfund Sites, EPA-451/R-92-
002 (NTIS PB93-122257), U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, Research Triangle Park, NC, September.
U.S. EPA. 1993a. Air/Superfund National Technical Guidance Study Series, Volume IV -
Guidance for Ambient Air Monitoring at Superfund Sites, EPA 451/R-93-007 (NTIS
PB93-199214), U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, May.
U.S. EPA. 1993b. Options for Developing and Evaluating Mitigation Strategies for Indoor Air
Impacts at CERCLA Sites, EPA-45 l/R-93-012, U.S. Environmental Protection Agency, Office
of Air Quality Planning and Standards, Research Triangle Park, NC, September.
U.S. EPA. 1993c. Radon Mitigation Standards, EPA-402/R-93-078, U.S. Environmental
Protection Agency, October (Revised April 1994).
U.S. EPA. 1995a. SCREENS Model User's Guide, EPA-454/B-95-004 (NTIS PB95-222766),
U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, September.
U.S. EPA. 1995b. User's Guide for the Industrial Complex (ISC3) Dispersion Models: Volume
I -User Instructions, EPA-454/B-95-003a (NTIS PB95-222741), U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC, September.
U.S. EPA. 1997a. Emission Factor Documentation for AP-42, Section 2-4, Municipal Solid
Waste Landfills, U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. August.
U.S. EPA. 1997b. Compilation of Air Pollutant Emission Factors, AP-42, Volume I, Fifth
Edition, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, NC, October.
U.S. EPA. 1998a. Environmental Technology Verification Report, Soil Gas Sampling
Technology, W. L. Gore & Associates, Inc., GORE-SORBER Screening Survey, EPA/600/R-
98/095, U. S. Environmental Protection Agency, Office of Research and Development, National
Exposure Research Laboratory, Las Vegas, Nevada, August.
U.S. EPA. 1998b. Environmental Technology Verification Report, Soil Gas Sampling
Technology, Quadrel Services, Inc., EMFLUX Soil Gas System, EPA/600/R-98-096, U.S.
Environmental Protection Agency, Office of Research and Development, National Exposure
Research Laboratory, Las Vegas, Nevada, August.
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Emissions from Closed or Abandoned Facilities
U.S. EPA. 1998c. Characterization of Municipal Solid Waste in the United States: 1997Update,
EPA-530/R-98/007 (NTIS PB2000-101333), U.S. Environmental Protection Agency, Office
of Solid Waste and Emergency Response, Washington, DC, May.
U.S. EPA. 1999a. Air Toxics Emissions-EPA's Strategy for Reducing Health Risks in Urban
Areas, EPA-453/F-99-002, U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, Research Triangle Park, NC, July.
U.S. EPA. 1999b. Municipal Solid Waste Landfills, Volume I: Summary of the Requirements
for the New Source Performance Standards and Emission Guidelines for Municipal Solid Waste
Landfills, EPA/453/R-96-004, U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, Research Triangle Park, NC, February.
U.S. EPA. 2001. Supplemental Guidance for Developing Soil Screening Levels for Superfund
Sties, OSWER 9355.4-24, U.S. Environmental Protection Agency, Office of Solid Waste and
Emergency Response, Washington, DC, March.
U.S. EPA. 2004. Measurement of Fugitive Emissions at a Region I Landfill, EPA-600/R-04-
001, U.S. Environmental Protection Agency, Office of Research and Development, National
Risk Management Research Laboratory, Research Triangle Park, NC, January.
Yaws, C.L., L. Bu, and S. Nijhawan. 1995. "Determining VOC adsorption capacity," Pollution
Engineering, February.
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7-4
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Emissions from Closed or Abandoned Facilities
Appendix A
Monitoring Landfill Gas Chemicals
of Potential Concern (COPCs)
A-l
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Guidance for Evaluating Landfill Gas
A-2
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Table of Contents
Section Page
1.0 Introduction A-5
2.0 Municipal Solid Waste Landfill Air Emission Mechanisms A-6
2.1 Gas Phase Emissions A-6
2.2 Particulate Emissions A-6
2.3 Transport and Diffusion A-7
2.4 Transformation, Deposition, and Depletion A-7
3.0 Defining COPCs A-7
3.1 Volatile Organic Compounds A-7
3.2 Semi-volatile Organic Compounds A-8
3.3 Non-volatile Organic Compounds A-9
3.4 Inorganic Compounds A-9
4.0 Developing a Site-Specific Target Compound List and Monitoring Design Elements . . . A-9
5.0 Composition of Landfill Gas A-13
6.0 Technologies for Monitoring COPCs at MSW Landfill Sites A-13
6.1 Grab Sampling A-14
6.2 Time-Integrated Sampling A-14
6.3 Real-Time Monitoring A-15
6.4 Passive Sampling A-16
6.5 Portable Real-Time Monitoring A-16
7.0 Sources of Sampling and Analytical Methodologies A-17
7.1 Federal Reference Methods A-17
7.1.1 Federal Reference Method 18: Measurement of Gaseous Organic Compound
Emissions by Gas Chromatography A-17
7.1.2 Federal Reference Method 25C: Determination of Nonmethane Organic
Compounds in MSW Landfill Gases A-18
7.1.3 Federal Reference Method 2E: Determination of Landfill Gas Production
Flow Rate A-18
7.1.4 Federal Reference Method 3C: Determination of Carbon Dioxide, Methane,
Nitrogen, and Oxygen from Stationary Sources A-18
7.2 Compendia of Methods A-19
7.2.1 Compendium Methods for Analysis of Volatile Organics A-19
7.2.2 Compendium Method IO-1/IO-2 for Suspended Particulate Matter A-21
7.2.3 Compendium Method to TO-12 for Nonmethane Organic Compounds A-23
7.2.4 Compendium Method TO-13A/TO-10 for Semivolatiles A-23
7.2.5 Compendium Method IO-5 for Mercury A-24
8.0 Real-time Monitoring for Organic Gases A-27
8.1 Gas Chromatography/Mass Spectroscopy A-27
8.2 Ion Mobility Spectrometry A-33
8.3 Diffusion-Limited Technique (Passive Sampling Devices) A-33
8.4 Radial Plume Mapping A-34
8.4.1 Horizontal Radial Plume Mapping A-34
8.4.2 Vertical Radial Plume Mapping A-34
8.4.3 Open-Path Fourier Transform Infrared Spectroscopy A-36
8.4.4 Open-Path Tunable Diode Laser Absorption Spectroscopy A-36
8.4.5 Ultraviolet Differential Optical Absorption Spectroscopy A-36
9.0 Real-time Monitoring for Suspended Particulate Matter A-36
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Guidance for Evaluating Landfill Gas
Table of Contents (concluded)
Section Page
9.1 Forward Scatter Near-infrared (RAM and MINIRAM) A-36
9.2 Cascade Impaction (Piezoelectrical Balance) A-37
9.3 Beta Attenuation Monitor A-38
9.4 TEOM Particle Monitor A-38
10.0 Federal Reference Method 21 A-39
10.1 Portable VOC Analyzers A-39
10.2 Instrument Specifications A-41
10.2.1 Monitor Response A-41
10.2.2 Measurement Range A-42
10.2.3 Scale Resolution A-42
10.2.4 Response Time A-42
10.2.5 Safety A-42
10.2.6 Probe Dimensions A-42
10.2.7 Response Factor A-42
10.2.8 Accuracy A-42
10.3 Performance Criteria A-42
10.4 Selecting an Analyzer A-43
11.0 Application of Different Sampling Techniques A-43
11.1 Landfill Surface Monitoring A-43
11.1.1 Grids A-44
11.1.2 Sampling Methods and Procedures A-45
11.1.3 Sampling Grid Pattern A-45
11.1.4 Monitoring Frequency A-45
11.1.5 Recordkeeping A-45
11.2 Soil Gas Sampling A-46
11.3 Vent Monitoring A-51
11.4 Perimeter Air Monitoring A-51
11.4.1 Site Characteristics A-52
11.4.2 Evaluation of Available Information A-53
11.4.3 Meteorological Data A-53
11.4.4 Selection of Instrumentation and Analytical Methods A-53
11.4.5 Number and Location of Sampling Sites A-54
11.4.6 Cost Factors A-56
12.0 References A-59
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Emissions from Closed or Abandoned Facilities
1.0 Introduction
Monitoring air pollutants at MSW landfills through various routes of exposure is required in almost all
regulations. Monitoring provides the regulator with information and data that can be used to determine
compliance with applicable emission limits. Specifically, monitoring requirements are identified in the
NSPS and EG regulations, the RCRA regulations, and as part of any risk evaluation procedures
performed at MSW landfills. Each of these regulations specify specific monitoring procedures identified
in various Federal reference methods and compendia methods used in assessing MSW landfill gas
emissions applicable to the regulations.
The NSPS (40 CFR 60, Subpart WWW) and EG (Subpart Cc) promulgated under Section 11 l(b) of the
CAA are in place to control emissions of NMOCs from MSW landfills. As discussed in Chapter 4,
NMOC is used under the NSPS and EG as a surrogate measurement of VOCs. As discussed in Chapter
4, the determination of the need for controls under the NSPS/EG is a thee-tier protocol, for which
sampling plays a major role:
• Tier 1 determination of the NMOC emission rate is performed through the application of the
LandGEM model using default input parameter values.
• Tier 2 involves determining the NMOC concentration generated by the landfill via Federal
Reference Method 25C or Federal Reference Method 18.
• Tier 3 employs Federal Reference Method 2E for determining the site-specific methane generation
rate constant.
In addition, the NSPS and EG regulations specify that each landfill must meet a surface methane
operational standard. Compliance with the standard is determined by Federal Reference Method 21, a
portable organic vapor analyzer, for measuring surface concentrations of methane along the entire
perimeter of the collection area and along a serpentine pattern spaced 30 meters apart for each collection
area on a quarterly bases. The portable organic vapor analyzer must meet all instrument specifications
provided in Section 3 of Federal Reference Method 21.
For an evaluation of the risks from exposure to MSW landfill gases, the route of human exposure is
inhalation of COPCs transported by the landfill gas. In addition, State and Federal requirements dictate
that the MSW landfill must be in compliance with air pathways ARARs, as appropriate. The three routes
of exposure are ambient air, subsurface convection, and subsurface vapor intrusion. Each of these
pathways must be considered by the RPM or OSC:
• For assessing the ambient air pathway, EPA's Compendium of Methods for Determination of Toxic
Organic Compounds in Ambient Air is used to quantify the various COPCs. For instance,
Compendium Method TO-10/13A is used for quantifying semi-volatiles/PAHs, Compendium
Method TO-15 for VOCs, Compendium Method TO-12 for NMOCs, Inorganic Compendium
Method IO-5 for mercury and Inorganic Compendium Methods IO-1/IO-2 for suspended particulate
matter.
• For assessing subsurface convection, Federal Reference Method 21 can be employed to quantify
subsurface methane vapor transport and indoor concentrations.
• Finally, for subsurface vapor intrusion into a building from contaminated ground water or for vapor
intrusion from subsurface convection, EPA's Compendium of Methods for the Determination of Air
Pollutants in Indoor Air is used to quantify the various COPCs. Method IP-l-A uses specially-
treated canisters and portable gas chromatographs for initial screening investigation for VOCs.
Method IP-7/8 uses polyurethane foam for capture of pollutants with subsequent analysis by GC/MS
for quantifying dioxin furans, polychlorinated biphenyls (PCBs) and semi-volatiles. Method IP-10
provides for monitoring of particulate matter using a single-stage impactor.
Under RCRA, Subtitle D, the owners or operators of all MSW landfill units must implement a routine
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Guidance for Evaluating Landfill Gas
methane monitoring program to ensure that the standards set forth in the regulations are met. The
frequency and type of methane monitoring system must be based on site-specific soil conditions. Federal
Reference Method 21 meets the monitoring specifications and other requirements of the Subtitle D rules.
The purpose of this Appendix is to provide the RPM and/or the OSC with information associated with
the monitoring techniques and instrumentation needed to quantify landfill gas constituents. This
appendix discusses the nature of landfill gases, the development of a target compound list (TCL),
technologies for monitoring landfill gases, including time-integrated and real-time monitoring for
inorganic, organic, and suspended particulate matter (SPM). Additionally, this appendix provides
guidance on the use and application of Federal Reference Methods (FRMs) and Compendia methods for
quantifying COPCs found in landfill gas.
2.0 Municipal Solid Waste Landfill Air Emission Mechanisms
Emissions from municipal solid waste (MSW) landfill sites are classified as either point or area sources.
Point sources include landfill gas vents and landfill gas combustion equipment exhausts (controlled
emissions), whereas area sources are generally associated with fugitive emissions (e.g., from landfill
cover materials, lagoons, material handling and contaminated surface areas).
Air contaminant emissions can be classified into two categories (i.e., gas phase emissions and particulate
matter emissions). The mechanisms associated with gas phase emissions are quite different from those
associated with particulate matter releases.
2.1 Gas Phase Emissions
Gas phase emissions primarily involve organic compounds but can also include inorganic compounds
and certain metals. Gaseous emissions from an MSW landfill site can be released through a variety of
mechanisms, including:
• Volatilization,
• Biodegradation,
• Photo-decomposition,
• Hydrolysis, and
• Combustion.
Volatilization is typically the most important mechanism for air releases and occurs when molecules of
a dissolved or pure substance escape to an adjacent gas layer. For wastes at the surface, this action results
in immediate transport into the atmosphere. Volatilization from subsurface wastes results in a
concentration gradient in the soil-gas from the waste to the surface. The rate of emissions is usually
limited by the rate of diffusion of contaminants to the soil-air interface. For MSW landfills still
generating methane, convective vapor transport due to pressure gradients can also be significant. The
rate of volatilization of contaminants at a soil-air boundary is a function of the concentration and
properties of the escaping chemical (molecular weight, vapor pressure, Henry's Law constant, boiling
temperature), soil properties (moisture, temperature, clay content, and organic content), and properties
of the air at soil level (temperature, relative humidity, and wind speed). The rate of volatilization from
liquid surfaces depends on the concentration of the contaminants at the liquid-air interface. Any factors
that enhance mixing in the bulk liquid and replenishment of contaminants in the boundary layer will
enhance the volatilization rate.
2.2 Particulate Emissions
Particulate matter (PM) emissions from MSW landfill sites can be released through wind erosion,
mechanical disturbances, and combustion. COPCs, such as semi-volatiles (polycyclic aromatic
hydrocarbons—PAHs), dioxin/furans (D/Fs), polychlorinated biphenyls (PCBs), and metals, can also
A-6
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Emissions from Closed or Abandoned Facilities
be adsorbed onto PM and thereby transported with the inert material.
The importance of each of these mechanisms varies as a function of source type. The hazardous
constituents of concern in a particulate release (which include PM and semi-volatiles) may involve
constituents that are either absorbed or adsorbed onto the particulate or constituents that actually
comprise the particulate. These constituents may include volatile and semi-volatile organic compounds,
metals, and non-volatile toxic organic compounds.
Significant atmospheric dust can arise from the disturbance of soil exposed to the air. Dust generated
from these area sources is referred to as "fugitive" because it is not discharged to the atmosphere in a
confined stream. The dust generation process is caused by two physical phenomena: (1) entrainment of
dust particles by the action of wind erosion of an exposed surface under moderate-to-high wind speeds
and (2) pulverization and abrasion of surface materials by mechanical disturbances.
For airborne particles, the particle size distribution plays an important role in inhalation exposure. Large
particles tend to settle out of the air more rapidly than small particles but may be important in terms of
non-inhalation exposure. Very small particles (i.e., those that are less than 10 |im in diameter) are
considered to be respirable and, thus, present a greater inhalation health hazard than the larger particles.
2.3 Transport and Diffusion
Once released to the ambient air, a contaminant or COPC is subject to simultaneous transport and
diffusion processes in the atmosphere. Atmospheric transport/diffusion conditions are significantly
affected by meteorological, topographic, and source factors.
The contaminant will be carried by the ambient air, following the spatial and temporal characteristics
of the wind flow as determined by the ambient temperatures and the wind direction and speed. The
turbulent motions of the atmosphere (as characterized by atmospheric stability conditions) promote
diffusion of airborne gases and particulate matter. Thus, the local meteorology during and after the
release determines where the contaminant moves and how it is diluted in the atmosphere.
2.4 Transformation, Deposition, and Depletion
Contaminants emitted to the atmosphere are subjected to a variety of physical and chemical influences.
Transformation processes can result in the formation of more hazardous substances or may result in
hazardous constituents being converted into less harmful ones. A variety of inorganic and organic
materials may be present along with the natural components of the air. The emissions may remain in the
atmosphere for a considerable time and undergo a myriad of reactions. Both primary and secondary
products are exposed to further changes through oxidation and photochemical reactions. In general,
however, these effects are secondary to transport and diffusion in importance and are subject to more
uncertainty.
3.0 Defining COPCs
Ambient air around a MSW landfill site is a very complex, dynamic system of interacting chemicals. As
previously discussed, the pollutants can be found in the gas phase, in the particulate phase, or in a liquid
aerosol surrounded by a gaseous atmosphere. The complex nature of the dynamic air system in and
around a MSW landfill site controls the complexity of the solution of sampling method and analytical
requirements in the identification and quantification of these chemicals. Each COPC has its own unique
characteristics, yet many fall within basic classes such as volatiles, semi-volatiles, aromatics, halo-
genated compounds, etc.
3.1 Volatile Organic Compounds (VOCs)
VOC is a general term used to describe the gaseous nonmethane organic emissions from a MSW land-
A-7
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Guidance for Evaluating Landfill Gas
fill. These compounds have vapor pressures
greater than 10"1 mm Hg and boiling points less Table A-1. Defining Hazardous Air Pollutants
than 200 °C. A capped landfill usually maintains
a stable temperature between 77 and 150 °F.
Temperature rises promote volatilization and
chemical reactions, and as a general rule,
emissions of VOCs and NMOCs double with
every 18 °F increase in temperature. Maximum
temperatures usually occur in the first year.
Temperature for years 5 to 10 are typically 100 to 115 °F. VOCs are predominantly found in the gaseous
state in the atmosphere, as identified in Table A-1, and illustrated in Figure A-1.
3.2 Semi-volatile Organic Compounds (SVOCs)
Semi-volatile organic compounds (SVOCs) are not as easily collected or analyzed as the VOCs.
However, attention has been focused on resolving the problems associated with SVOCs found around
Category
PM
SVOCs
VOCs
Vapor pressure
(mm Hg)
io-'
Boiling point
(°C)
>500
200 to 50
<200
SILVER (2212) »-
METALS
SEWII-VOLATILES
ANTHRACENE (342) -
BENZO(a)PYRENE(310) ^
ACENAPHTHYLENE (269) »
NAPHTHYLENE(218) •-
DICHLOROBENZENE(173) ^
CHLOROBENZENE(132) *-
TOLUENE (110) *-
BENZENE (80) •-
DICHLOROyETHANE (40) •-
VOLATILES
METHYLCHLORIDE (-24) *-
^^
700 °C
600 °C
500 °C
400 °C
300 "C
200 °C
100°C
0°C
-150°C
•«• CHROMIUM (2482)
LEAD (1744)
•* CADMIUM (765)
<* SODIUM (685)
^ BENZOfklFLUORANTHENE (480)
-« MERCURY (356)
- PHENANTHRENE (340)
-« 1,2,4-TRICHLOROBENZENE(213)
-« 0-DICHLOROBENZENE{180)
— STYRENE (145)
-. 1,2-DIBROMOMETHANE(131)
-. CHLOROFORM (61)
— ETHYL CHLORIDE (12.8)
-« FREON 12 (-29.8)
Figure A-1. Example of Defining COPCs by Boiling Point.
A-8
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Emissions from Closed or Abandoned Facilities
MSW landfill sites. Members of this class include PAHs with three or more fused rings; halogenated
compounds such as PCBs; organopesticides with chlorine and phosphorus; and various pesticides and
herbicides. Vapor pressures of these compounds range from 10"1 to 10~7mm Hg, and their boiling points
range from 200 to 500 °C, as illustrated in Table A-l and Figure A-l. These less volatile compounds are
present in the atmosphere, both in gaseous phase and in particle-bound phase. Their point of origin can
be landfill gas vents, LFG combustion equipment exhaust, or fugitive emissions from the surface of the
landfill.
3.3 Non-volatile Organic Compounds
Ambient air contains relatively low amounts of non-volatile organic compounds, which are organic
compounds with vapor pressures less than 10"7 mm Hg and boiling points greater than 500 °C. These
compounds are almost always found in the condensed particle-bound state. Polycyclic hydrocarbons
with more than four rings, and their nitrogenous and oxygenated derivatives, are the major constituents
of this category.
3.4 Inorganic Compounds
Inorganic compounds are those compounds with vapor pressures less than 10"12 mm Hg. These
compounds are almost always found in the particle state. Heavy metals, such as lead, chromium,
cadmium, zinc, beryllium copper, and other earth metals represent this category of COPCs.
4.0 Developing a Site-specific Target Compound List and Monitoring
Design Elements
Developing a site-specific target compound list (TCL) is a key factor in the long-term monitoring at a
MSW landfill site. MSW landfill sites often contain a complex mixture of contaminants, and not every
contaminant will pose a significant risk via the air pathway. Selection of too broad a range of compounds
can lead to excessive cost, whereas selection of too few may result in not meeting the data quality
objectives (DQOs) of the project. In most cases, the selection of a TCL at a MSW landfill site is a
compromise between technical feasibility and environmental significance.
The objective of developing a site-specific TCL is to establish a prioritized list of compounds for which
there are sampling and analytical protocols and to provide a tool for optimizing the air monitoring
design. The TCL includes compounds most commonly found at the MSW landfill site that pose the most
significant threat to human health and are most likely to enter the air pathway.
Certain compounds typically are considered to "drive" both the listing of target compounds and the risk
assessment as part of the air pathway analysis (APA). These compounds pose the most significant risk
during various phases of the life of a MSW landfill. Consequently, the objective of the APA is to focus
available resources and effort on those compounds thought to pose the most significant risk rather than
including an evaluation of every compound found at the MSW landfill site. The selected analytes,
therefore, become the COPCs. Compounds of interest for MSW landfills are categorized into four broad
classifications based on the compound and its physical and chemical properties. As previously discussed,
the four classifications are:
• NMOCs and VOCs, especially benzene and chlorinated solvents such as vinyl chloride, methylene
chloride, chloroform, etc.,
• SVOCs, such as PAHs, pesticides, dioxin/furans, and other semi-volatile inorganic compounds,
• Particulate matter and non-volatile compounds such as asbestos and cyanides, and
• Heavy metals, such as lead, chromium, cadmium, zinc, beryllium, copper, and arsenic.
Table A-2 summarizes the compound classes and the representative compounds in each of the four
classifications. Table A-3 provides typical concentrations of the different categories of COPCs in
ambient air.
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Table A-2. Example of Classification of COPCS (Organic and Inorganic Compounds) for Monitoring
Programs at MSW Landfill Sites.
Contaminant type Compound class
Volatile organic
compounds
Volatile inorganic
Aromatics
Halogenated
species
Oxygenated
species
Sulfur containing
species
Nitrogen
containing species
Acids
Representative compounds
benzene
toluene
ethylbenzene
carbon tetrachloride
chloroform
methylene chloride
chloromethane
1 ,2-dichloropropane
trans- 1 ,3 -dichloropropene
cis- 1 ,3 -dichloropropene
bromoform
bromomethane
acetone
2-butanone
carbon disulfide
benzonitrile
hydrogen cyanide
total xylenes
styrene
chlorobenzene
bromodichloromethane
dibromochloromethane
1, 1,2,2-tetrachloroethane
1,1,1 -trichloroethane
1 , 1 -dichloromethane
chloroethane
tetrachloroethane
trichloroethane
vinyl chloride
2-hexanone
4-methyl-2-pentanone
hydrochloric acid
compounds
Sulfur containing hydrogen sulfide
Semi-volatile organic
compounds
Phenols
phenol
2-methylphenol
4-methlphenol
2,4-dimethylphenol
2-chlorophenol
2,4-dichlorophenol
2,4,5-trichloropheno
2,4,6-trichlorophenol
pentachlorophenol
4-chloro-3-methylphenol
2-nitrophenol
4-nitrophenol
2,4-dinitrophenol
4,6-dinitro-2-methylphenol
Esters
bis(2-ethylhexyl)phthalate
di-n-butyl phthalate
vinyl acetate
di-n-octyl phthalate
diethyl phthalate
Chlorinated
1,2-dichlorobenzene
1,3 -dichlorobenzene
1,4-dichlorobenzene
1,2,4-trichlorobenzene
hexachlorobenzene
nitrobenzene
2,6-dinitrotoluene
2,4-dinitrotoluene
3,3 -dichlorobenzidine
Amines
n-nitrosodimethylamine
n-nitrosodi-n-propylamine
n-nitrosodiphenylamine
aniline
2-nitroaniline
3-nitroaniline
4-nitro aniline
4-chloroaniline
Ethers
bis(2-chloroethyl)ether
bis(2-chloroisopropyl)ether
Alkadienes
Miscellaneous and
aromatics
hexachlorobutadiene
benzoic acid
bis(2-chloroethoxy)methane
dibenzofuran
isophorone
hexachlorocyclopentadiene
benzyl alcohol
hexachloroethane
continued
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Contaminant type
Non-volatiles
Compound class
Polychlorinated
biphenyls (PCBs)
Inorganic metals
and nonmetals
Arochlor 1016
Arochlor 1221
Arochlor 1232
Arochlor 1242
aluminum
antimony
arsenic
asbestos
barium
beryllium
cadmium
calcium
chromium
cobalt
copper
iron
Representative compounds
Arochlor 1248
Arochlor 1254
Arochlor 1260
lead
magnesium
manganese
nickel
potassium
selenium
silver
sodium
thallium
tin
vanadium
zinc
Table A-3. Example of Typical Concentrations of Groups of COPCS in the Atmosphere.
Category Concentration range
PAHs 10-100 ng/m3
PCBs, Dioxins, Furans 1-10 pg/m3
Pesticides/Herbicides 10-100 ng/m3
Particles/Metals 10-50 ug/m3
Volatiles 0.5-5.0 ppb
Monitoring all emissions at an MSW landfill site is not realistic; so, when developing an air monitoring
program, target compounds are usually selected to represent either a broad classification or a specified
class of compounds. These target compounds (i.e., indicator compounds), at a minimum, should include
all contaminants with concentrations greater than or equal to 10% of the appropriate health-based action
level.
This approach provides a practical basis to address the large number of potentially emitted compounds
at the site. Many factors should be reviewed in the decision process for selecting COPCs, including:
• Types of air contaminants (organic, inorganic, biohazard),
• Physical state of air contaminants (gas, liquid, solid),
• Level of air contaminant emissions,
• Air monitoring objectives,
• Potential availability of standard sampling and analytical techniques,
• Homogeneity of the waste material, and
• Potential analytical interferences from the site.
The rate at which gaseous contaminants are emitted into the air depends, in part, on their volatilities,
which depend on vapor pressures and Henry's Law constants. Highly volatile compounds will typically
be emitted at a higher rate than compounds of similar concentration in the waste but with lower
volatility. Computer models that rely, in part, on compound vapor pressure and Henry's Law data as
input are often used to estimate potential emissions to the air. Emission rates can then be used as input
to an atmospheric dispersion model to gauge concentration levels at the property line of the MSW
landfills and at off-site receptors. Semi-volatile and nonvolatile compounds may also be of concern
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when they exist in significant concentrations within the waste or are contained in any wind-blown dust.
It often is not practical to monitor for every compound present in the waste or ambient air because of
the limitations of available technical or financial resources. In these cases, potential target compounds
should be ranked in terms of predicted concentration levels and applicable health-based action levels.
Note that the potential for adverse health effects varies from compound to compound, and the health-
based action levels may vary by orders-of-magnitude between compounds with relatively similar
structures and physical properties. For example, 1,2-dichloroethane is considered to be a much more
potent carcinogen than 1,1-dichloroethane, and benzene is considered to pose a much more significant
risk than equal amounts of toluene or xylene. Therefore, the most significant compounds at the site from
a health risk standpoint might not necessarily be those present in higher concentrations in the waste.
Basically, the objective is to find the type and/or species of COPCs that could be used to assess
emissions from the site (both point source and fugitive) and their air quality impact on the surrounding
community. The ideal target compound should be:
• Found in air emissions from the site in a fixed ratio to other constituents,
• Non-reactive or stable species,
• Found at levels above analytical detection limits,
• Unique to the MSW landfill site, and
• Of known toxicity and acceptable exposure criteria.
The objective of developing a site-specific TCL is to provide aprioritized list of COPCs associated with
the MSW landfill site. The TCL should be composed of those compounds that are most commonly found
at the MSW landfill site, pose the most significant threat to human health, and that are likely to enter the
air pathway. The number of target compounds to be monitored varies depending on the DQOs of the
MSW landfill site monitoring program, as identified in Table A-4.
Table A-4. Relationship Between Monitoring Design Elements and MSW Landfill Site Activities.
Site Activities
Design element
Level I: Screening or
baseline study
Level II: Short-term
investigation
Level III: Long-term
investigation
Number of target
compounds
Data quality
objectives
Sampling
Period
Duration
Frequency
Type of sampling
Multiple compound classes;
full analyte list
Identify compounds
accurately; semi-
quantitatively for NMOCs
and methane
24 hours
5 days to 1 year
Daily to once every 6 days
Mobile, walking the site and
taking a sample every 30
meters along the path and
along the perimeter
1-20
Quantify level of specified
compound(s); NMOC and
methane
8-24 hours
Duration of investigation
Daily
Fixed or mobile site from
vent tubes, bore holes,
sample wells, or perimeter
air monitoring stations
Monitoring method Low detection limits
characteristics Applicable to broad range of
compounds
Typically portable FIDs/PIDs
Rapid data turnaround
Low detection limits
Specific target compound
list
Quantify level of specified
compound(s)
24 hours
5 days to 1 year
Daily to quarterly
Fixed or mobile site from
vent tubes, bore holes,
sample wells, or perimeter
air monitoring stations
continued
Low detection limits
Specific target compound
list
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5.0 Composition of Landfill Gas
Landfill gas is made up primarily of methane (CH4) and carbon dioxide (CO2), but small quantities of
other gases are also present. EPA has determined that some of these compounds are carcinogenic or
associated with non-carcinogenic health effects. A list of COPCs often found in landfill gas is provided
in Table A-5.
Table A-5. COPCs Commonly Found in LFG.
Classification
Analyte
Very Volatile Organic
Speciated Volatile Organic Compounds
Inorganic Constituents
Methane
Non-methane Organic Compounds (NMOCs)
1,1,1-Triehloroethane (Methyl Chloroform)
1,1-Dichloroethene (Vinylidene Chloride)
1,2-Dichloroethane (Ethylene Bichloride)
Acrylonitrile
Benzene
Carbon Tetrachloride
Chlorobenzene
Chloroethane (Ethyl Chloride)
Chlorofluorocarbons (as Dichlorodifluoromethane)
Chloroform
Dichlorobenzene a
Ethylene Dibromide
Dichloromethane (Methylene Chloride)
Perchloroethylene (Tertrachloroethylene)
Toluene
Trichloroethylene (Trichloroethene)
Vinyl Chloride
Xylenes (all isomers)
Mercury (total)b
Hydrogen Sulfide
a The para-isomer is a CAA Title III listed HAP.
b No data was available to speciate total mercury into the elemental and organic forms.
6.0 Technologies for Monitoring COPCs at MSW Landfill Sites
A variety of sampling methods can be used to monitor emissions from MSW landfill sites. The methods
vary according to sample type (i.e., volatile compounds, semi-volatile compounds, inorganics, and
particulate-borne compounds), sample duration and detectability, and applicability to the monitoring
objectives of the program. The greatest number of available methods for any one type are for the volatile
fraction. Semi-volatile pollutants exist in both the vapor and particulate phases, so the sampling
methodology must address both. Finally, the concentration of particulate-borne contaminants (inorganic
and non-volatile organic) can be monitored by collection of the total mass loading during sampling.
Sampling techniques may be divided into broad classes, regardless of the analyte of concern. They are
grab sampling, time-integrated sampling, real-time monitoring, passive sampling, and portable real-time
monitoring.
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• Grab sampling—grab sampling involves collecting an instantaneous air sample. This technique
usually requires some form or type of container (i.e., canister, TED LAR bag, etc.) to contain the
instantaneous sample.
• Time-integrated sampling—time-integrated sampling involves collecting a sample over a fixed
time period (e.g., 1 hr, 4 hr, 8 hr or 24 hr) and provides a single, integrated value. Methods
included in time-integrated sampling are whole air canister sampling, solid adsorbent tube
monitoring, and most particulate matter and semi-volatile collection systems.
• Real-time monitoring—real-time monitoring involves sample extraction, conditioning,
analyzing, and reporting within a fixed time period, usually less than 15 minutes.
• Passive sampling—passive sampling involves collecting a sample over an extended period of
time without assistance from a pump. This sampling technique is usually exclusively associated
with monitoring volatile organics.
• Portable real-time monitoring—portable real-time systems provide sampling and analysis of a
limited target compound set. The use of portable systems allows one to survey the site and
identify hot spots, thus making it a very feasible tool during the investigation.
6.1 Grab Sampling
Grab sampling involves extracting a sample at a single point-in-time. The hardware for this sampling
is usually a whole-air sample container (i.e., specially-treated canister, glass sampling bulb, Tedlar bags,
or solid adsorbent tubes for colorimetric gas detection). In the grab sample mode, a sample is taken over
a very short period of time, from a few seconds to a few minutes.
Grab sampling is usually used in EPA's air pathway analysis program as a screening technique to
identify contaminants that might be present in an area of interest and to determine their approximate
concentrations. As an example, grab sampling can be used to collect volatile organics during the site
investigation stage using Tedlar bags or specially-treated canisters to help develop future long-term
monitoring plans or to assess the preliminary risks at the site.
Some of the advantages of grab sampling are that the methodology is simple to apply and sampling costs
are at a minimum. Several disadvantages, however, are associated with grab sampling. One major
disadvantage is that the value acquired is a single point in time and cannot be related to typical health
effect exposure durations. Another disadvantage is that the sample volume acquired is relatively small,
thus requiring very sensitive analytical techniques if the data is to be used for comparison with ambient
air regulatory limits. Finally, inward and outward diffusion of gases in some of the collection containers
has been observed, thus creating uncertainty in the data.
6.2 Time-Integrated Sampling
This category of monitoring is the most commonly used technique for monitoring COPCs at MSW
landfill sites. Time-integrated is most applicable if the pollutant is present in very low concentrations
because sampling can be conducted long enough to provide the analytical system sufficient sample to
meet required detection limits. Appropriate time-integrated sampling techniques are available for
collecting volatiles, semivolatiles, inorganics, and PM in the ambient air.
In time-integrated sampling, the sampling period can be as short as minutes or as long as weeks or
months depending upon the detection limits associated with the analytical system. The results from the
analysis of integrated samples are expressed as average concentrations over the sampling period.
Integrated sampling for PM can be done by high and low volume samplers, dichotomous samplers, or
size-select inlet samplers. The sophistication of the samplers ranges from manually operated hand-held
units to fully automated units that can run for weeks unattended.
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Integrated sampling for gaseous pollutants can be done by extracting a sample over a period of time
through solid absorbents, specially-treated canisters, impingers, or other collection devices that can
capture the analytes of interest over a period of time. In general, the greater the sampling time, the more
analyte is trapped on the collection media, thus allowing for lower health-based detection limits. Thus,
integrated sampling methods may not be adequate for evaluating compliance with short-term (e.g., 15
min, 1 hr) action levels that might be imposed at the site boundary. As an example, a high-volume
particulate monitor at the site boundary may not be adequate to determine compliance with a 1-hr
emission limit for selected inorganic metals. Integrated sampling methods are therefore useful for
determining pollutant concentrations when the regulatory limit is based on a time similar to the 8-hr
personnel exposure level or EPA's 24-hr national ambient air quality standards (NAAQS). For some
analytes, like semivolatiles, a sampling period of 72 hr may be required to obtain adequate sample to
meet the desired health-based detection limits.
Integrated sampling techniques offer additional advantages. They can be cost effective, require fewer
personnel than continuous monitoring and are sufficiently flexible to achieve the detection sensitivity
to meet the health-based detection limits needed in most regulatory monitoring programs. In addition,
samples can be analyzed at a more convenient time or place offsite. Several drawbacks of integrated
sampling include the lack of immediate feedback on the data that is acquired, thus preventing
modification of activities on site. In addition, time-integrated sampling methods typically do not give
site decision makers timely data so that they can determine worker and community acute exposure to
pollutants or the need for implementing emission controls. Another disadvantage is that short-term
information is also lost. Finally, time-integrated monitoring requires the collected sample to be
transported to another location for analysis, thus leading to possible sample integrity problems involving
sample deterioration, loss of analytes, and contamination from the surrounding environment.
6.3 Real-Time Monitoring
Real-time monitoring refers to methods that provide nearly instantaneous concentration values, thus
allowing multiple measurements over a very short time period of several minutes. In general, real-time
means the ability to extract, condition, concentrate, analyze, and report data nearly instantaneously. The
samples may be analyzed directly at the collection point, or the sample may be transported through heat-
traced lines to a central analytical center for analysis. In the former situation, a single analytical system
is used at each of the sampling points around the MSW landfill site or from vent tubes at the site. In the
latter case, a single analytical device is used to analyze samples from multiple sampling points around
the MSW landfill site. In this case, the analytical system cycles through each of the sampling points in
the network. Analytical systems may involve gas chromatography (GC), gas chromatography/mass
spectrometry (GC/MS) or mass spectrometry/mass spectrometry (MS/MS).
Real-time monitoring usually occurs when personnel at the MSW landfill site must make timely
decisions on the emissions from the site. Real-time monitoring also enables the investigator to see peak,
short-term concentrations that may have important health effects. Variations in concentration as a
function of time can be correlated with source emissions. The maj or advantage that real-time monitoring
has over portable real-time monitors is that most portable monitors react with entire classes of
compounds and tend not to be specific for a given compound that might be of concern. As an example,
photo-ionization detectors (PID) are very sensitive to aromatic hydrocarbons but significantly less
sensitive to aliphatic hydrocarbons or methane. In essence, a portable system does not have the
capability to differentiate between compounds if it does not have a GC column attached to it.
Although real-time monitoring systems have numerous benefits, they also have disadvantages. Such
systems are expensive and require frequent calibration and routine maintenance. In addition, real-time
systems are usually complex, requiring highly trained field personnel, rigorous quality-control (cali-
bration) procedures, and independent performance audits of routine monitoring and data handling
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Guidance for Evaluating Landfill Gas
operations. Finally, securing electrical power and a suitable location for housing the real-time system
and the adaptation of sampling lines and cables for the system can require long-term planning and entail
considerable expense.
6.4 Passive Sampling
In recent years, the development of passive sampling devices (PSD) has drawn much attention. These
devices sample by means of gas diffusion or permeation of the COPC (usually VOCs or volatile
inorganic compounds) on an adsorbent (i.e., Tenax, charcoal, CarboTrap 300) rather than by means of
a pump. They have been shown to be simple, convenient, inexpensive, and valid alternatives for
assessing time-weighted average concentrations for personal exposure monitoring.
Analysis of adsorbed compounds on sampling tubes is done by thermal desorption and chromato-
graphic separation. Specificity can be introduced into a passive sampling technique by choice of a
suitable adsorbent substrate that is unique to capturing a specific compound. As an example, a passive
sampler using chemically-coated glass fiber filter has been developed for formaldehyde. A comparison
of recoveries of trichloroethylene from active charcoal tubes and athermal desorbable personal monitor
revealed the passive sampler to exhibit better recovery efficiency. A personal dosimeter based on
molecular diffusion and direct detection by room temperature phosphorescence has been developed to
monitor vapors of polynuclear aromatics.
6.5 Portable Real-Time Monitoring
Probably one of the most attractive sampling and analysis approaches is that of portable sampling
methods based upon real-time monitoring. Portable sampling techniques are mostly used in screening
applications at MSW landfill sites. Portable monitoring allows instantaneous results to be acquired so
on-site decisions can be made for the protection of workers and off-site communities. Portable
monitoring allows rapid turn-around of data with relatively inexpensive instrumentation.
Two of the most common detectors utilized in portable gas sampling techniques are portable flame
ionization detectors (FIDs) and PIDs. These detectors, used in conjunction or separately, are generally
used to give background levels of NMOCs, methane, and total VOCs. Portable sampling techniques are
used to identify hot spots of NMOC, CH4, or total VOCs within a test locale. Two of the most important
attributes of these detectors are their ever-increasing levels of sensitivity and their ability to specifically
characterize and/or identify VOCs when used in conjunction with a chromatographic column,.
The operation of a FID involves the pollutant entering a flame where it is mixed with hydrogen and
burns. Ions and electrons formed in the flame enter an electrode gap, decreasing the gap resistance, thus
permitting a current to flow. The flow of electrons determines the pollutant concentration. The FID is
a universal detector, responding to a host of organic compounds and classes. One of the major
advantages of the FID is its lack of response to air and water. The FID therefore serves as a basis for
most commercially available "total hydrocarbon" and "non-methane hydrocarbon" analyzers. The
detection limits for most FIDs is about 100 ppbv.
Portable PIDs operate on the principle of photo ionization. In operation, the gas stream is subjected to
a high-intensity beam of UV radiation from a lamp of a particular energy. If the molecule ionization
potential is lower than that of the lamp, absorption occurs by the gas molecule, leading to the formation
of a positive ion and free electron. The positive ion is collected at the electrode and the resultant current
is directly proportional to the analyte concentration. Consequently, the ionization potential of the lamp
is very important in the detection of certain classes of compounds. Compounds having a high ionization
potential will be less easily detected than those with a lower ionization potential. Thus, a PID can
readily detect aromatic hydrocarbons but will not detect aliphatic hydrocarbons having a higher
ionization potential.
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Emissions from Closed or Abandoned Facilities
The manufacturers of photo ionization lamps usually provide lamps in four energy levels:
• 8.3 eV,
• 9.5 eV,
• 10.2 eV, or
• 11.7 eV.
It is more difficult to ionize an alkane (i.e., butane) than a chlorinated aromatic (i.e., chlorobenzene).
The selection of the lamp, therefore, allows the user to screen out certain organics based on their
ionization potential. If the lamp does not have enough energy to ionize the molecule, the detector does
not see it. Consequently, aromatics can be selectively detected in the presence of halogenated
hydrocarbons with a low-energy lamp (e.g., 9.5. eV), whereas both groups can be detected with a high-
energy lamp (11.0 eV). The sensitivity of the PID is considerably better than the FID in most cases
(10 ppb or better). Recent models have shown sensitivity in the sub-parts per billion range.
7.0 Sources of Sampling and Analytical Methodologies
As documented in Chapter 5, various Federal Reference Methods (FRMs) have been identified in the
MSW landfill regulations in support of characterizing emissions for these facilities. Although FRMs are
specific for a few of the COPCs, there are no methods for many others. It is appropriate that the correct
sampling and analytical method be selected. Accurate and reliable data can only be generated if the
correct samples of analytical method for each COPC is used. Where possible, the user should use FRMs.
However, there are available other sampling and analytical methods which are applicable to quantifying
emissions from MSW landfills, as identified in EPA's Compendia. This section will review both the
FRMs and Compendia methods which are applicable to MSW landfill gas monitoring.
7.1 Federal Reference Methods
7.1.1 Federal Reference Method 18: Measurement of Gaseous Organic Compound Emissions by Gas
Chromatography. This method can be considered a self-validating method since it requires method
performance data for particular applications prior to full use. Direct on-line GC analysis is preferred, but
this is frequently impossible for reasons of safety or access. When using direct analysis, a dilution
interface is often required. Alternatively, samples of the gas may be captured for later analysis. Several
types of sampling media for this alternative are discussed, including glass sampling bulbs, evacuated
stainless steel spheres (evacuated canisters are not mentioned specifically, but sometimes can be used),
and various sorbents.
Method 18 is useful for situations for which a specific method has not been developed and in which the
stack conditions are relatively mild. For example, high temperatures, high moisture, or a corrosive matrix
in a stack or vent may necessitate the use of other methods such as SW-846 Volatile Organic Sampling
Train (VOST).
Once the gas containing the pollutant of interest is cleaned of particulate matter and at ambient
temperature, there is the choice of several sample media. Most directly, a whole-gas sample is captured
in an inert container. Either Tedlar bags or evacuated specially-treated stainless steel canisters are used,
although there are differences in opinion on the use of evacuated canisters. Tedlar bags are relatively
cheap, light weight, and transparent so that the sample being collected may be observed. For example,
if water condenses inside the bag, it may be necessary to go to the VOST sampling train. However,
since the bags are transparent, gases collected in them must be protected from light if they are
photosensitive. Also, the gas must be drawn into the bag using some pumping apparatus. Evacuated
canisters, on the other hand, use the vacuum in the canister to draw the sample. Flow regulators are
often used in conjunction with canisters to guarantee a uniform flow and at such a rate that the sampling
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Guidance for Evaluating Landfill Gas
will last for a desired period (a few minutes up to 24 hours). In some cases, pumps are used with
canisters, which will withstand pressures above atmospheric, if necessary. Canisters must be pre-cleaned
(Tedlar bags should never be reused), but they are rugged and very easy to use. Both Tedlar bags and
canisters have limitations on the types of gases they may be used for. For example, canisters should not
be used for acid gases (e.g., HC1) nor for any sulfur compounds (e.g., H2S).
Along with the choice of sampling media, a range of gas chromatographic detectors can be used, as long
as they are appropriate for the target species. The detectors most frequently in current use are flame
ionization, photo-ionization, and electron capture detectors. Although the mass spectrometric detector
should, in principle, function similarly to non-specific detectors mentioned above for detecting eluting
species from the GC column, EPA is developing a MS-specific Method 18, which takes advantage of
the additional information available from GC/MS.
7.7.2 Federal Reference Method25C: Determination of Non-methane Organic Compounds (NMOC)
in MSWLandfill Gases. Federal Reference Method 25 C is applicable to the sampling and measurement
of nonmethane organic compounds (NMOCs) as carbon in MSW landfill gases. In operation, a stainless
steel sample probe that has been perforated at the bottom third is driven or augered to a depth of 1.0 m
below the bottom of the landfill cover and connected to an evacuated cylinder. Once the gas is trapped
within the evacuated cylinder, the cylinder valve is closed and the tank returned to the laboratory for
analysis. The NMOC content of the gas is determined by injecting a portion of the gas into a gas
chromatographic column to separate the NMOCs from CO, CO2, and CH4; the NMOCs are oxidized
to CO2, then reduced to CH4, and measured by a FID. In this matter, the variable response of the FID
associated with different types of organics is eliminated.
Prior to field deployment, the sample tank is evacuated, cleaned, and leak checked. In addition, the
analytical system must pass an initial performance test which includes an oxidation catalyst efficiency
check, a reduction catalyst efficiency check, NMOC calibration, and a system performance check. The
analytical system must also pass a daily NMOC analyzer calibration check before field samples are
analyzed.
7.1.3 Feder al Reference Method 2E: Determination of Landfill Gas Production Flow Rate. Federal
Reference Method 2E is used to calculate the NMOC flow rate from landfills. In operation, extraction
wells are installed either in a cluster of three or at five locations dispersed throughout the landfill. A
blower is used to extract LFG from the landfill. LFG composition, landfill pressures near the extraction
well, and volumetric flow rate of LFG extracted from the wells are measured and the landfill gas
production flow rate is calculated. The well head assembly used to determine production flow rate
involves a well head control valve, water knockout jar, orifice meterto measure pressure drop across an
inline orifice plate, blower assembly, and an outlet sample port.
7.1.4 Federal Reference Method 3C: Determination of Carbon Dioxide, Methane, Nitrogen, and
Oxygen from Stationary Sources. Federal Reference Method 3C is applicable to the analysis of CO2,
CH4, N2, and O2 concentrations by using a GC coupled with a thermal conductivity detector (TCD). In
operation, a gas sample is extracted directly to the analyzer or captured in a whole-air container
(canister/Tedlar bag), similar to Federal Reference Method 3 or Federal Reference Method 25C. If
captured in a whole-air container, the sample is taken back to the laboratory for analysis.
Analysis involves passing a portion of the sample through a chromatographic column that has the
capability to separate the listed gases. Once separated, their concentrations are determined with a TCD.
As with other GC methods, the GC analyzer is optimized, calibrated, and checked for linearity prior to
analysis of the field sample.
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Emissions from Closed or Abandoned Facilities
7.2 Compendia of Methods
Over the last several years, EPA's Office of Research and Development (ORD), National Risk
Management Research Laboratory (NRMRL) and the Center for Environmental Research Information
(CERI) has supported technology transfer programs involving peer-reviewed ambient air monitoring
methods presented in a standard format for use by regulatory and industrial personnel via publication
of a series of methods Compendia. These Compendia represent a series of documents reflecting EPA's
commitment to use standardized sampling and analytical procedures in environmental applications.
Presently, there are three Compendia:
1. Compendium of Methods for the Determination of Inorganic Compounds in Ambient Air,
EPA/625/R-96-010a, June 1999 (Winberry etal, 1999a).
2. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air,
Second Edition, EPA/625/R-96-010b, January 1999 (Winberry et al, 1999b).
3. Compendium of Methods for the Determination of Air Pollutants in Indoor Air, EP A/600/4-90-
010, April 1990 (Winberry et al., 1990).
While EPA has published numerous Federal Reference Methods (FRMs), there has been a lack of
standardized ambient air sampling and analytical methodologies which address the Clean Air Act
Amendments of 1990, Title III list of now 188 hazardous air pollutants (HAPs). The Compendia address
methodologies for characterizing various HAPs, both inorganic and organic constituents, including
sulfuric acid, nicotine, metals, PM2 5 (particulate matter having an aerodynamic diameter equal to or less
than 2.5 |im), mercury (particle/vapor), SVOCs, and specific VOCs.
The intent of the Compendia is to assist Federal, State, and local regulatory personnel in developing and
maintaining necessary expertise and up-to-date technology involving the sampling and analysis of
organic and inorganic compounds in ambient air. Historically, regulatory agency personnel have used
a variety of monitoring and analytical techniques to obtain results that varied widely in data quality. The
absence of the use of standardized procedures raised serious concern about the compatibility of the data
collected and its ultimate use. Ensuring data compatibility is critical, because environmental regulators
make major decisions based upon the interpretation of such data relating to public health issues and
applicable control options. The Compendia provide standardized procedures for the sampling and
analysis of organic and inorganic compounds in the ambient air, thus providing high quality data to the
regulatory community and making industry accountable for HAP emissions as part of their source
compliance strategy.
7.2.1 Compendium Methods for Analysis of Volatile Organics. Compendium Methods TO-14 and
TO-15 are applicable to specific VOC compounds and allow an analyst to reach the sub- ppb level.
Numerous compounds, many of which are chlorinated and more toxic than non chlorinated compounds,
have been successfully tested for storage stability in pressurized canisters. Method TO-15 is significant
in that it extends the Method TO-14A description for using canister-based sampling and gas chroma-
tographic analysis in the following ways:
• Method TO-15 incorporates a multisorbent/dry purge technique or equivalent for water
management, thereby addressing a more extensive set of compounds than addressed by Method
TO-14A.
• The Method TO-14A approach to water management alters the structure or reduces the sample
stream concentration of some VOCs, especially water-soluble VOCs..
• Method TO-15 uses the GC/MS technique as the only means to identify and quantitate target
compounds. The GC/MS approach provides a more scientifically-defensible detection scheme,
which is generally more desirable than using single or even multiple specific detectors.
• In addition, Method TO-15 establishes method performance criteria for acceptance of data,
allowing the use of alternate but equivalent sampling and analytical equipment.
• Method TO-15 includes enhanced provisions for inherent quality control. The method uses
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Guidance for Evaluating Landfill Gas
internal analytical standards and frequent verification of analytical system performance to assure
control of the analytical system. This more formal and better documented approach to quality
control guarantees a higher percentage of good data.
7.2.1.1 Compendium Method TO-14. This method is applicable to non-polar VOCs that have been
tested and determined to be stable when stored in pressurized and sub-atmospheric pressure canisters.
Numerous compounds, many of which are chlorinated VOCs, have been successfully tested for storage
stability in pressurized canisters. However, minimal documentation is currently available demonstrating
stability of VOCs in sub-atmospheric pressure canisters. Both sub-atmospheric pressure and pressurized
sampling modes typically use an initially evacuated canister and pump-ventilated sample line during
sample collection. Pressurized sampling requires an additional pump to provide positive pressure to the
sample canister. A sample of ambient air is drawn through a sampling train comprised of components
that regulate the rate and duration of sampling into a pre-evacuated specially prepare passivated canister.
The analytical strategy for Method TO- 14A involves using a high-resolution GC coupled to one or more
appropriate GC detectors. Historically, detectors for a GC have been divided into two groups:
non-specific detectors and specific detectors. The non-specific detectors include, but are not limited to,
the nitrogen-phosphorus detector (NPD), the FID, the electron capture detector (BCD) and the PID. The
Method TO-14A analytical system employs aNafion permeable membrane dryer to remove water vapor
from the sample stream. Polar organic compounds permeate this membrane in a manner similar to water
vapor and rearrangements can occur in some hydrocarbons due to the acid nature of the dryer.
Compendium Method TO-15 provides guidance associated with alternative water management systems
applicable to the analysis of a large group of VOCs in specially-treated canisters.
7.2.1.2 Compendium Method TO-15. This method is applicable to polar and non-polar VOCs that have
been tested and determined to be stable when stored in pressurized and sub-atmospheric pressure
canisters. This method documents sampling and analytical procedures for the measurement of subsets
of the 97 VOCs that are included in the 189 hazardous air pollutants (HAPs) listed in Title III of the
Clean Air Act Amendments of 1990. VOCs are defined here as organic compounds having a vapor
pressure greater than 10"1 Torrat25 °Cand760mmHg. This method applies to concentrations of VOCs
above 0.5 ppbv and typically requires VOC enrichment by concentrating up to one liter of a sample
volume. Use of Method TO-15 for many of the VOCs is likely to present two difficulties: (1) what
calibration standard to use for establishing a basis for testing and quantitation, and (2) how to obtain
audit standards. The atmosphere is sampled by introduction of air into a specially-prepared stainless steel
canister. Both subatmospheric pressure and pressurized sampling modes use an initially evacuated
canister. A pump ventilated sampling line is used during sample collection with most commercially
available samplers. Pressurized sampling requires an additional pump to provide positive pressure to the
sample canister. A sample of air is drawn through a sampling train comprised of components that
regulate the rate and duration of sampling into the pre-evacuated and passivated canister. The analytical
strategy for Method TO-15 involves using a high resolution GC coupled to a mass spectrometer.
Method TO-15 has been applied to the sampling and analysis of COPCs involving VOCs for emission
monitoring of landfill gases, soil gases, and in particular, ambient air around the perimeter of the
landfill,as illustrated in Figure A-2.
7.2.1.3 Compendium Method TO-16. This method is intended for the use of an FT-IR system that
acquires data using a long, open air path and does not require the acquisition of a sample for subsequent
analysis. The system produces data that is a time sequence of the path-averaged atmospheric
concentrations of various gases. Because the FT-IR can potentially measure the concentration of a large
number of atmospheric gases, this method does not address the require-ment for measuring a particular
gas or a set of gases. The primary geometric configurations of FT-IR instruments that are commercially
available are the monostatic configuration and the bistatic configuration. Once a set of target gases has
A-20
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Emissions from Closed or Abandoned Facilities
been selected, the wave number
regions to be used in the analysis are
chosen. For the monostatic
instrument geometry, the stray light
component must be sub-tracted from
each single beam spec-trum. For the
bistatic case, the black body radiation
spectrum must be subtracted from
each single beam spectrum.
The method of trace gas monitoring
using FT-IR-based, long-path,
open-path systems has a number of
advantages that are significant over
traditional methods. Some of these
advantages are related to the path
monitoring aspect of this method
which, by its very nature,
distinguishes the method from all
point monitoring methods. The main
advantages of these systems are:
• Integrity of the sample is
assured since no sampling
actually occurs;
• Multi-gas analysis is possible
with a single field spectrum;
• Path-integrated pollutant
concentrations are obtained;
• Spatial survey monitoring of
industrial facilities is possible if scanning optics are used;
• Rapid temporal scanning of line-of-sight or multiple lines-of-sight is possible; and
• Monitoring of otherwise inaccessible areas is possible.
The ultimate significance of remote sensing with FT-IR systems is a matter of cost effectiveness and of
technological advances. Technological advances are required in at least two important areas: (1) the
improvement in the characteristics of the instrumentation itself and (2) the development of "intelligent"
software. The software is required to improve the means for short-term adjustment of background and
water vapor spectra to account for the continual variation of ambient conditions that can adversely affect
the accuracy and precision of FT-IR based systems.
7.2.2 Compendium Method IO-1/IO-2for Suspended Particulate Matter (SPM). Compendium Method
IO-1/IO-2 involves time-integrated and real-time monitoring for total suspended particulate (TSP) matter
and PM10 (particulate matter with an aerodynamic diameter equal to or less that 10 |im). TSP and PM10
monitoring at the perimeter of a MSW landfill site may be required and can be integrated within the
MSW landfill gas monitoring program. From a regulatory standpoint, sampling options for TSP and
PM10 monitoring fall into two categories: reference methods and equivalent methods. Reference
methods are those sampling procedures that were initially established by EPA for determining average
TSP and PM10 concentrations during a fixed time period. Hence, these methods are also termed time-
integrated. These are by far the most commonly used TSP and PM-10 measure-ment methods.
Alternatively, EPA has more recently designated certain continuous reading instruments as equivalent
methods for measuring ambient air concentrations of TSP and PM10 at or near real-time. Real-time
Figure A-2. Example of Compendium Method TO-15
Application for Landfill COPCs at the Perimeter of the Site.
A-21
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Guidance for Evaluating Landfill Gas
measurements are useful when parameters such as the diurnal variation in concentration or changes in
concentration associated with specific site activities of interest.
The reference, or time-integrated, method for TSP is codified at 40 CFR 50, Appendix B. This method
uses a high-volume (hi-vol) sampler to collect particles with aerodynamic diameters of approximately
100 |im or less. The TSP sampler is a compact unit consisting of a protective housing; a high-speed,
high-volume electric blower; a filter holder capable of supporting an 8 by 10-inch filter; and a flow-
controller and blower assembly capable of maintaining the air-flow rate through the instrument at 40 to
60 ftVmin throughout the sampling period. The hi-vol sampler design causes the TSP to be deposited
uniformly across the surface of the fixed filter. The TSP hi-vol can be used to determine the average
ambient TSP concentration over the sampling period, and the collected material subsequently can be
analyzed to determine the identity and quantity of inorganic metals present in the TSP.
The reference method for PM10 is codified in 40 CFR 50, Appendix J. Two technologies have qualified
as meeting the sampling requirements of the reference method for PM10: a hi-vol with a 10 |im inlet and
a dichotomous sampler. The PM10 hi-vol is identical to the TSP hi-vol except that it is equipped with a
sampling inlet that directs only particles with aerodynamic diameter of 10 |im or less to the filter.
A dichotomous sampler collects both PM10 and PM25. The sample is further split into fractions above
and below 2.5 |im at the sample inlet. Both the hi-vol and dichotomous samplers deposit the particulate
matter uniformly across the surface of fixed filters. Both can be used to determine average ambient PM10
concentration over the sampling period, and the collected material from both subsequently analyzed for
inorganic metals and other materials present.
Both the hi-vol and the dichotomous sampler can be equipped with either of two basic types of flow
control systems, a mass-flow-control (MFC) system and a volumetric-flow-control (VFC) system. The
calibration and standard operating procedures differ considerably between these two types of
flow-control systems, and therefore operational procedures are control-system-specific.
The flow rate in an MFC system is actively sensed and controlled at a predetermined set point. Air is
pulled through the filter into the intake of the blower and subsequently exits the sampler through an exit
orifice, which facilitates measurement of the flow with a manometer or pressure recorder. The flow rate
is controlled by an electronic mass-flow controller, which uses a flow sensor installed below the filter
holder to monitor the mass flow rate and related electronic circuitry to control the speed of the blower
motor accordingly. The controlled flow rate can be changed by an adjustment knob on the flow
controller.
Real-time monitoring for TSP or PM10 can be done by utilizing the principle of micro-balance oscillation
impaction. A micro-balance oscillation impaction monitor (TEOM Monitor) utilizes the filter-based
measurement system for providing real-time mass monitoring capability.
The TEOM ambient particulate monitor is comprised of two main components: the TEOM sensor unit
and the cabinet assembly. The enclosure cabinet houses the mass flow controller with an in-line filter
cartridge and silicone tubing and an electronic circuit chamber with the appropriate wiring and fre-
quency signal output.
The microbalance is a rectangular metal enclosure which houses a metal cylinder (the sensor head) and
inner inlet tube. The metal cylinder contains an oscillating tapered element, an electronic feedback
system, and a filter cartridge. The tapered element is attached to a platform at its wide end (bottom) and
has a small metal tip onto which the filter cartridge sits. The electronic feedback system consists of an
amplifier board, which maintains the elements oscillation, and the electronics, which allow frequency
A-22
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Emissions from Closed or Abandoned Facilities
signals to be transcribed to mass units. At the bottom of the microbalance, a silicone tube that is
connected to the mass flow controller carries the air sample.
In operation, the particle-laden air is drawn in through a heated air inlet followed by an exchangeable
filter cartridge, where the particulate mass collects. The filtered air then proceeds through the sensor
unit, which consists of a patented microbalance system and an automatic flow controller. As the sample
stream moves into the microbalance system (filter cartridge and oscillating hollow tube), it is heated to
the temperature specified by the software. The automatic flow controller pulls the sample stream through
the monitor at flow rates between 0.5 to 1 L/min. The hollow tube is attached to a platform at its wide
end and is vibrated at its natural frequency. As particulate mass gathers on the filter cartridge, the tube's
natural frequency of oscillation decreases, and the electronic microbalance system continually monitors
this frequency. Based on the direct relationship between mass and frequency, the instrument's
microcomputer computes the total mass accumulation on the filter, as well as the mass rate and mass
concentration, in real-time. The data processing unit contains software which allows the user to define
the operating parameters of the instrumentation through menu-driven routines. During sample collection,
the program plots total mass, mass rate and/or mass concentration on the computer screen in the form
of sealers. The program allows two y-axis scales to be displayed and up to 10 variables to be plotted
simultaneously. In addition, the scales and variables used in plotting the data may be changed during
collection without affecting stored data.
7.2.3 Compendium Method TO-12 for NMOCs. A whole air sample is either extracted directly from
the MSW landfill vent, bore hole, landfill surface, or ambient air and analyzed on site by the GC system
or is collected into a precleaned specially-treated canister and analyzed offsite.
The analysis requires drawing a fixed-volume portion of the sample air at a low flow rate through a
glass-bead filled trap that is cooled to approximately -186 °C with liquid argon. The cryogenic trap
simultaneously collects and concentrates the NMOCs (either via condensation or adsorption) while
allowing the methane, nitrogen, oxygen, etc. to, pass through the trap without retention. The system is
dynamically calibrated so that the volume of sample passing through the trap does not have to be
quantitatively measured but must be precisely repeatable between the calibration and the analytical
phases.
After the fixed-volume air sample has been drawn through the trap, a helium carrier gas flow is diverted
to pass through the trap in the opposite direction to the sample flow and into a FID. When the residual
air and methane have been flushed from the trap and the FID baseline stabilizes, the cryogen is removed
and the temperature of the trap is raised to approximately 90 °C.
The organic compounds previously collected in the trap volatilize due to the increase in temperature and
are carried into the FID, resulting in a response peak or peaks from the FID. The area of the peak or
peaks is integrated, and the integrated value is translated to concentration units via a previously-obtained
calibration curve relating integrated peak areas with known concentrations of propane.
By convention, concentrations of NMOCs are reported in units of parts per million carbon (ppmC),
which, for a specific compound, is the concentration in parts per million by volume multiplied by the
number of carbon atoms in the compound.
7.2.4 CompendiumMethodTO-13A/TO-10forSemi-Volatiles/PAHs. Compendium Methods TO-13A
and TO-10 utilize a polyurethane foam plug and filter to trap semi-volatiles (PAHs, dioxins, furans,
PCBs, etc.) from landfill gas. Filters and adsorbent cartridges (containing XAD-2 or PUF) are cleaned
in solvents and vacuum-dried. The filters and adsorbent cartridges are stored in screw-capped jars
A-23
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Guidance for Evaluating Landfill Gas
wrapped in aluminum foil (or otherwise protected from light) before careful installation on a modified
high volume sampler.
Approximately 325 m3 of landfill gas over a 24-hour period is drawn through the filter and adsorbent
cartridge using a calibrated high-volume sampler for Method TO-13A. Method TO-10A uses the same
type filter/PUF adsorbent, but only the air is pulled through the PUF cartridge at a rate of 1 L/min. This
allows the collection of semi-volatiles from landfill gas vents and bore holes without disturbing the air
from the source.
The amount of air sampled through the filter and adsorbent cartridge is recorded, and the filter and
cartridge are placed in an appropriately labeled container and shipped along with blank filter and
adsorbent cartridges to the analytical laboratory for analysis.
The filters and adsorbent cartridge are extracted by Soxhlet extraction with appropriate solvent. The
extract is concentrated by a Kuderna-Danish (K-D) evaporator followed by silica gel clean-up using
column chromatography to remove potential interferences prior to analysis.
The eluent is further concentrated by the K-D evaporator, then analyzed by either GC equipped with a
FID or by MS detection or high performance liquid chromatography (HPLC). The analytical system is
verified to be operating properly and calibrated with five concentration calibration solutions, each
analyzed in triplicate. The amount of semi-volatiles detected on the extracted PUF/filter is related to the
concentration of the COPCs in the sample.
7.2.5 Compendium Method IO-5 for Mercury. Elemental mercury (Hg°) and most of its derivatives
are metabolic poisons which bioaccumulate in aquatic food chains, ultimately reaching concentrations
capable of causing neurological and reproductive damage in terrestrial, as well as, aquatic organisms.
Atmospheric Hg, although present only in trace amounts, has been established as a significant source
of mercury to aquatic environments.
Mercury compounds in the atmosphere exist in vapor and particulate forms, preferentially partitioning
into the vapor phase. Mercury species fall within two main categories; inorganic Hg compounds and
organic Hg compounds. The most common form of inorganic mercury is elemental mercury vapor. Other
inorganic forms of Hg include mercuric chloride (HgCl2) and mercurous chloride (HgCl). The organic
compounds include those compounds in which Hg is covalently bonded to a carbon atom, as in the case
of methyl and dimethyl mercury.
Method IO-5 describes procedures for collection and analysis of vapor phase and particulate Hg in order
to provide an EPA-approved accessible sampling and analytical methodology for uniform monitoring
of Hg levels. The collection of mercury from ambient air, venttubes, and bore holes involves using gold-
coated bead traps and glass-fiber filters. The amalgamation process for vapor-phase Hg requires a flow
rate low enough to allow adsorption of the mercury in the air to the gold surface. On the other hand, the
significantly lower levels of particle-phase Hg requires a much higher flow rate in order to collect
sufficient particle mass for mercury determination. Therefore, separate sampling systems are needed for
the collection of Hg in the vapor and particle phases. Accurate flow determinations through both
sampling systems are critical in providing accurate Hg concentrations in air.
Vapor-phase mercury is collected using gold-coated glass bead traps. A Teflon filter pack with a glass
fiber filter is placed in front of the traps to remove particulate material from the air being sampled. Air
is pulled through the vapor-phase sampling system using a mass-flow controlled vacuum pump at a
nominal flow rate of 0.3 L/min.
A-24
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Emissions from Closed or Abandoned Facilities
Particle-phase Hg is collected using a glass-fiber filter in an open-faced Teflon filter pack. Air is pulled
through the particulate sampling system using a vacuum pump at a nominal flow rate of 30 L/min.
Determination of vapor- and particle-phase Hg in ambient air is accomplished using cold-vapor atomic
fluorescence spectrometry (CVAFS); more specifically, dual-amalgamation CVAFS. The amount of
vapor-phase Hg collected on a gold-coated bead trap is determined directly by CVAFS. The sample trap
is heated to release the collected mercury. The desorbed mercury is carried in an inert gas stream (He
or Ar) to a second gold-coated analytical bead trap. The Hg collected on the analytical trap is then
thermally desorbed and carried into the CVAFS analyzer. The resulting voltage peak is integrated to
produce the peak area for the sample.
Determination of Hg in the particle phase requires acid extraction of the glass-fiber filters prior to
analysis. The sample filters are extracted in a nitric acid solution using microwave digestion to yield
"acid-extractable" particulate mercury. The extract is oxidized to convert all forms of Hg to Hg+2
(ionized Hg), and SnCI2 is added to the extract to reduce the Hg+2to volatile Hg°. The Hg° is liberated
from the extract by purging with an inert gas (N2) and collected on a gold-coated bead analytical trap.
The amount of mercury collected on the trap is then determined using dual-amalgamation CVAFS. The
detection limits achieved using Inorganic Compendium Method IO-5 are 30 pg/m3 for particulate
mercury and 45 pg/m3 for vapor mercury.
Table A-6 documents the availability of both FRMs and Compendia methods available for characterizing
MSW landfill gas, soil gas, landfill gas combustion equipment exhaust, indoor air, and ambient air.
Table A-7 list the various advantages and disadvantages of EPA's Compendium Methods.
Table A-6. Applicability of FRMs and Compendia Methods for MSW Landfill COPCs.
Analyte
Landfill
Gas
Soil Gas
Landfill
Surface
Media
LFG
Combustion
Ambient Air
Indoor Air
COPCs Commonly Found
1,1,1-
Trichloroethane
1 , 1 -Dichloroethene
1 ,2-Dichloroethane
Acrylonitrile
Benzene
Carbon
Tetrachloride
Chlorobenzene
Chloroethane
Chlorofluoro-
carbons
TO-14/TO-
151
TO- WTO-
IS
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO- WTO-
IS
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
Mod.
212
Mod.
21
Mod.
21
Mod.
21
Mod.
21
Mod.
21
Mod.
21
Mod.
21
Mod.
21
FRM-
FRM-
FRM-
FRM-
FRM-
FRM-
FRM-
FRM-
FRM-
Method
SW-846
Method
Method
Method
Method
Method
Method
Method
Method
00303,
0030
0030
0030
0030
0030
0030
0030
0030
TO-14/TO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-l/TO-
14/TO-154
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
continued
A-25
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Guidance for Evaluating Landfill Gas
Analyte
Chloroform
Dichlorobenzene
Ethylene
Dibromide
Mercury
Methylene Chloride
Perchloroethylene
Toluene
Vinyl Chloride
Xylenes
NMOC
Other COPCs
Chlorinated
Organics
Total Reduced
Sulfur
Methane
C0/C02
Semi-Volatiles
(PAHs, D/Fs,
PCBs)
Suspended
Paniculate Matter
Speciated Reduced
Sulfur
Hydrogen Sulfide
Carbonyl Sulfide
Carbon Bisulfide
Flow Rates
Landfill
Gas
TO-14/TO-
15
TO- WTO-
IS
TO-14/TO-
15
IO-54
TO-14/TO-
15
TO-14/TO-
15
TO- WTO-
IS
TO-14/TO-
15
TO-14/TO-
15
TO-
12/FRM-
25C
TO-14/TO-
15
TO-14/TO-
15
Portable
Real
Time/TO-
14/TO-15
FRM3C
TO-10A1
FRM-5i2
FRM-15
FRM15
FRM-15
FRM-2E
Soil Gas
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
IO-5
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-14/TO-
15
TO-
12/FRM-
25C
TO-14/TO-
15
TO-14/TO-
15
Portable
Real
Time/TO-
14/TO-15
FRM3C
TO-10A
FRM-5i
Portable
Real Time
Portable
Real Time
Portable
Real Time
FRM2-E
Landfill
Surface
Mod. FRM-
21
Mod. FRM-
21
Mod. FRM-
21
IO-5
Mod. FRM-
21
Mod. FRM-
21
Mod. FRM-
21
Mod. FRM-
21
Mod. FRM-
21
Portable
Real Time
TO-14/TO-
15
Portable
Real Time
Portable
Real
Time/TO-
14/TO-15
FRM3C
NA
FRM-5i
Portable
Real Time
Portable
Real Time
Portable
Real Time
NA5
Media
LFG
Combustion
Method 0030
Method 0030
Method 0030
Method 00603
Method 0030
Method 0030
Method 0030
Method 0030
Method 0030
FRM-25C
Method 0030
FRM 15/1 5 A
FRM18
FRM3C
Method 00 103
FRM 5
FRM-15
FRM-15
FRM-15
FRM-2E
Ambient Air
TO-WTO-15
TO-WTO-15
TO-WTO-15
IO-5
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-WTO-15
TO-12/FRM-
25C
TO-WTO-15
TO-WTO-15
Portable Real
Time/TO-
14/TO-15
FRM3C
TO- 13 A1
IO-14
FRM-15
FRM-15
FRM-15
NA
Indoor Air
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
IO-5
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-l/TO-
14/TO-15
TO-
12/FRM-
25C
IP-1A
IP-1A
Portable
Real
Time/IP-lA
FRM3C
IP-74
IP-104
Portable
Real Time
Portable
Real Time
Portable
Real Time
NA
continued
A-26
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Emissions from Closed or Abandoned Facilities
1 Winberry, W.T., Jr., "Compendium of Methods For The Determination of Organic Compounds in Ambient
Air-Second Edition," U.S. Environmental Protection Agency, Office of Research and Development, Center
for Environmental Research Information, Cincinnati, OH, EPA-625/R-96/010b, January 1999
http://www.epa.gov/ttn/amtic/inorg.html (accessed August 2005).
2 40CFR Part 60, Appendix A http://www.epa.gov/ttn/emc/promgate.html (accessed August 2005).
3 Test Methods for Evaluating Solid Waste: Physical/Chemical Methods: SW-846
http://www.epa.gov/epaoswer/hazwaste/test/main.htm (accessed August 2005).
4 Winberry, W.T., Jr., Stephen Edgerton, and Linda Forehand, "Compendium of Methods For the
Determination of Inorganic Compounds in Ambient Air," U.S. Environmental Protection Agency, Office of
Research and Development, Center for Environmental Research Information, Cincinnati, OH,
EPA-625/R-96-010a, June 1999 http://www.epa.gov/ttn/amtic/airtox.html (accessed August 2005).
5 NA = not applicable.
8.0 Real-Time Monitoring for Organic Gases
Many varieties of organic species analyzers are available. Gas chromatographic systems include all
devices that separate organic species through use of a packed or capillary column and measure the
organic concentration using a detector at the end of the column. Several analyzers are hybrid
chromatographs, in that organic/inorganic separation is performed through chemical or thermal
techniques and analysis using typical detectors (i.e., flame ionization, electron capture, etc.).
8.1 Gas Chromatography/Mass Spectroscopy (GC/MS)
Gas chromatography is a common technique used for separating and analyzing mixtures of gases and
vapors. A gas mixture is percolated through a column of porous solids or liquid coated solids which
selectively retard sample components. A carrier gas is used to bring the discreet gaseous components
to a detector, and the sample can be identified and quantified through analysis of the detector response
and the component retention time. Gas chromatography has been in use in the laboratory since 1905;
however, it has only recently been used in environmental applications.
A compound in a gas matrix can be more fully identified through analysis of retention time in a GC/MS.
Identification can be established by comparing the total ion current profile of an eluted compound to a
published standard spectrum. GC/MS techniques are particularly suited for analysis of organics in air
through a concentration step. GC/MS has also been used to identity organic ambient air contaminants.
The concentration step involves passing the air sample through an absorber column that traps the organic
analytes followed by thermal desorption of that material in the GC. This technique is semi-continuous,
and overall response time of a GC/MS is typically greater than 3 minutes. This powerful tool has been
adapted to identify and quantitate organic compounds at landfills in close to real-time. At present, many
GC/MS instruments are in routine use as continuous monitors. Double mass spectrometry (MS/MS) and
laser multi-photon ionization mass spectrometry have been identified as potential on-line or real time
instruments for the identification of PAHs. These instruments do not use the GC for separation of
components and therefore do not involve the same delays in response time.
A disadvantage of GC/MS and MS/MS techniques is the complexity and cost of the instrumentation, and
investments of more than $75,000 are usually required. The mass spectra produced is complex and close
to real-time results can only be provided through a computer with extensive library searching
capabilities. The MS can scan for certain compounds within seconds; however, full spectrum scans
usually take greater than 3 minutes. These advantages should be weighed against the high sensitivity and
resolution capabilities of the GC/MS system.
A-27
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Table A-7. Advantages and Disadvantages of EPA's Compendia Methods.
Method
Desig.
Types of
Compounds
Determined
Sampling and Analysis Detection
Approach Limit
Advantages
Disadvantages
TO-1
(See also
Methods
TO-14A,
TO-15,
and
TO-17)
VOCs
(80 to 200'
'C)1
[e.g., benzene,
toluene, xylenes]
Tenax-GC Adsorption and
GC/MS OR GC/FID Analysis
Ambient air is drawn through
organic polymer sorbent
where certain compounds are
trapped. The cartridge is
transferred to the laboratory,
thermally desorbed, and
analyzed using GC/MS or
GC/FID.
.01-100 • Good data base.
ppbv • Large volume of air can be
sampled.
• Water vapor is not collected.
• Wide variety of compounds
collected.
• Low detection limits.
• Standard procedures available.
• Practical for field use.
Highly volatile compounds and certain
polar compounds are not collected.
Rigorous clean-up of adsorbent required.
No possibility of multiple analysis.
Low breakthrough volumes for some
compounds.
Desorption of some compounds difficult.
Structural isomers are the most common
interferences.
Contamination of adsorbent and blank.
contaminants may be a problem.
Artifact formation.
to
oo
TO-2
(See also
Methods
TO-14A,
TO-15,
and
TO-17)
Highly volatile
VOCs
(-15 to +120 °C)
[e.g., vinyl
chloride,
chloroform,
chlorobenzene]
Carbon Molecular Sieve
Adsorption and GC/MS or
GC/FID Analysis
Selected volatile organic
compounds are captured on
carbon molecular sieve
absorbents. Compounds are
thermally desorbed and
analyzed by GC/MS or
GC/FID techniques.
0.1-200 • Trace levels of volatile organic
ppbv compounds are collected and
concentrated on sorbent
material.
• Atmospheric moisture not
collected.
• Efficient collection of polar
compounds.
• Wide range of application.
• Highly volatile compounds are
adsorbed.
• Easy to use in field.
Some trace levels of organic species are
difficult to recover from the sorbent.
Structural isomers are common
interferences.
Water is collected and can de-activate
adsorption sites.
Thermal desorption of some compounds
may be difficult.
TO-3
(See also
Methods
TO-14A,
TO-15,
and
TO-17)
VOCs nonpolar
(-10 to +200 °C)
[e.g., vinyl
chloride,
methylene
chloride,
acrylonitrile]
Cryogenic Preconcentration
and GC/FID/ECD Analysis
Vapor phase organics are
condensed in a cryogenic trap.
Carrier gas transfers the
condensed sample to a GC
column. Adsorbed compounds
are eluted from the GC
column and measured by FID
or BCD.
0.1-200 • Collects wide variety of volatile
ppbv organic compounds.
• Standard procedures are
available.
• Contaminants common to
adsorbent materials are avoided.
• Low blanks.
• Consistent recoveries.
• Large database.
Moisture levels in air can cause freezing
problems with cryogenic trap.
Difficult to use in field.
Expensive.
Integrated sampling is difficult.
Compounds with similar retention times
will interfere.
continued
-------
Method
Desig.
Types of
Compounds
Determined
Sampling and Analysis Detection
Approach Limit
Advantages
Disadvantages
m
3
o
3
o
o
(/)
(D
Q.
D)
3
Q.
O
D
(D
Q.
Tl
D)
O
(D
TO-4
(See also
Method
TO-10A)
Pesticides/PCBs
[e.g., PCBs,
4,4-DDE, DDT,
ODD]
High Vol Filter and PUF
Adsorbent Followed by
GC/FID/ECD or GC/MS
Detection
Pesticides/PCBs trap on filter
and PUF adsorbent trap. Trap
returned to lab, solvent
extracted and analyzed by
GC/FID/ECD or GC/MS.
0.2pg/m3
-200
ng/m3
Low detection limits.
Effective for broad range of
pesticides/PCBs.
PUF reusable.
Low blanks.
Excellent collection and
retention efficiencies for
common pesticides and PCBs.
Breakdown of PUF adsorbent may occur
with polar extraction solvents.
Contamination of glassware may limit
detection limits.
Loss of some semi-volatile organics
during storage.
Extraneous organics may interfere.
Difficulty in identifying individual
pesticides and PCBs if using BCD.
TO-9A
Dioxins/Furans/
PCBs
to
VO
PUF Adsorbent Cartridge and
HRGC/ HRMS Analysis
Ambient air is drawn through
a glass fiber filter and a PUF
adsorbent cartridge by means
of a high volume sampler.
The filter and PUF cartridge
are returned to the laboratory
and extracted using toluene.
The extract is concentrated
using the Kuderna-Danish
technique, diluted with
hexane, and cleaned up using
column chromatography. The
cleaned extract is then
analyzed by high resolution
gas chromatography/high
resolution mass spectrometry
(HRGC/HRMS).
0.25-5000
pg/m3
Cartridge is reusable.
Excellent detection limits.
Easy to preclean and extract.
Excellent collection and
retention efficiencies.
Broad database.
Proven methodology.
Analytical interferences may occur from
PCBs, methoxybiphenyls, chlorinated
hydroxydiphenylethers, naphthalenes,
DDE, and DDT with similar retention
times and mass fractions.
Inaccurate measurement—Ds/Fs are
retained on paniculate matter and may
chemically change during sampling and
storage.
Analytical equipment required
(HRGC/HRMS) is expensive and not
readily available.
Operator skill level important.
Complex preparation and analysis
process.
Can't separate particles from gaseous
phase.
continued
-------
Method
Desig.
Types of
Compounds
Determined
Sampling and Analysis Detection
Approach Limit
Advantages
Disadvantages
TO-12 NMOCs (non-
methane organic
compounds)
Canister Sampling—cryogenic
Preconcentration and FID
Detection
Ambient air is drawn into a
cryogenic trap where the
NMOCs are concentrated.
The trap is heated to move
the NMOCs to the FID.
Concentration of NMOCs is
determined by integrating
under the broad peak. Water
correction is necessary.
0.1-200 • Standard procedures are
ppmvC available.
• Contaminants common to
adsorbent materials are avoided.
• Low blanks.
• Consistent recoveries.
• Large database.
• Good sensitivity.
• Useful for screening areas or
samples.
• Analysis much faster than GC.
Moisture levels in air can cause freezing
problems.
Non-speciated measurement.
Precision is limited.
TO-13A
PAHs
[e.g.,
benzo(a)pyrene,
naphthalene,
fluorene]
PUF or XAD-2 Adsorbent
Cartridge and GC/MS
Analysis
Ambient air is drawn through
a glass fiber filter and a PUF
or XAD-2 adsorbent cartridge
by means of a high volume
sampler. The filter and PUF
cartridge are extracted using
10% diethyl ether. The extract
is concentrated using
Kuderna-Danish technique,
diluted, and cleaned up using
column chromatography. The
cleaned extract is then
analyzed by GC/MS.
0.5-500
ng/m3
Allows for sample dilution if
concentration is too high during
analysis.
Repeated analysis is possible.
High-volume sampling provides
for lower detection limits.
Filter and PUF are low cost.
Method has interferences due to
contamination of solvents, reagents,
glassware, and sampling hardware.
Coeluting contaminants may cause
interference with target analytes.
Heat, ozone, NO2, and ultraviolet light
may cause sample degradation.
O
c
CL.
D)
3
O
(D
SL
c
!±
3
(Q
D)
3
Q.
continued
O
D)
-------
Method
Desig.
Types of
Compounds
Determined
Sampling and Analysis Detection
Approach Limit
Advantages
Disadvantages
m
3
o
3
o
o
(/)
(D
Q.
D)
3
Q.
O
D
(D
Q.
Tl
D)
O
(D
TO-14A
VOCs
(non-polar)
[e.g., toluene,
benzene,
chlorobenzene]
Specially-prepared Canister
and GC/FID/ECD or GC/MS
Detection
Whole air samples are
collected in an evacuated
stainless steel canister. VOCs
are concentrated in the
laboratory with cryogen trap.
VOCs are revolatilized,
separated on a GC column,
and passed to one or more
detectors for identification
and quantitation.
0.2-25 • Best method for broad
ppbv speciation of unknown trace
volatile organics.
• Simple sampling approach.
• Good QA/QC database.
• Proven field and analytical
technology.
Limited to non-polar compounds due to
use of permeation type dryer.
Sample components may be adsorbed or
decompose through interaction with
container walls.
Water condensation at high humidity
may be a problem at high concentrations
(ppm).
Complex equipment preparation
required.
Expensive analytical equipment.
TO-15 VOCs
(polar/non-polar)
!> [e.g., methanol,
oo benzene, xylene,
^ nitrobenzene]
Specially-prepared Canister
and GC/MS Analysis
Whole air samples are
collected in a specially-
prepared canister. VOCs are
concentrated on a solid sorent
trap or other arrangement,
refocused on a second trap,
separated on a GC column,
and passed to an MS detector
for identification and
quantification.
0.2-25 • Incorporates a multisorbent/ dry
ppbv purge technique or equivalent
for water management, thereby
addressing a more extensive set
of compounds.
• Establishes method
performance criteria for
acceptance of data.
• Provides enhanced provisions
for quality control.
• Unique water management
approach allows analysis for
polar VOCs.
Expensive analytical equipment.
Operator skill level important.
continued
-------
Method
Desig.
Types of
Compounds
Determined
Sampling and Analysis Detection
Approach Limit
Advantages
Disadvantages
TO-16 VOCs (polar/
non-polar)
[e.g.,ammonia,
ethylene, carbon
monoxide,
chlorobenzene]
FTIR Open Path Spectroscopy
VOCs are monitored using
real-time long-path open-path
Fourier transform infrared
spectroscopy (FTIR).
25-500 • Open path analysis maintains
ppbv integrity of samples.
• Multi-gas analysis saves money
and time.
• Path-integrated pollutant
concentration measurement
minimizes possible sample
contamination, and provides
real-time pollutant
concentration..
• Applicability for special survey
monitoring.
• Monitoring at inaccessible areas
possible using open-path FTIR.
High level of operator skill level
required.
Requires spectra interpretation.
Limited spectra library available.
Higher detection limits than most
alternatives.
Must be skilled in computer operation.
Substantial limitations from ambient CO2
and humidity levels associated with
spectral analysis.
to
TO-17 VOCs
(polar/non-polar)
[e.g., benzene,
toluene, o-
xylene,
chlorobenzene]
Multi-bed Adsorbent Tube
Followed by GC/MS
Ambient air is drawn through
a multi-bed sorbent tube
where VOCs are trapped. The
cartridge is returned to the
laboratory, thermally
desorbed, and analyzed by
GC/MS or other methods.
0.2-25 • Placement of the sorbent as the
ppbv first element minimizes
contamination from other
sample train components.
• Large selection of sorbents to
match with target analyte list.
• Includes polar VOCs.
• Better water management using
hydrophobic sorbents than
Method TO-14 A.
• Large database, proven
technology.
• Size and cost advantages in
sampling equipment.
Distributed volume pairs required for
quality assurance.
Rigorous clean-up of sorbent required.
No possibility of multiple analysis.
Must purchase thermal desorption unit
for analysis.
Desorption of some VOCs is difficult.
Contamination of adsorbent can be a
problem.
Numbers in parenthesis are the boiling point range of the organics applicable to that Compendium Method.
O
c
CL.
D)
3
O
(D
SL
c
~
3
(Q
D)
3
Q.
O
D)
-------
Emissions from Closed or Abandoned Facilities
8.2 Ion Mobility Spectrometry (IMS)
Ion mobility spectrometry (IMS) has traditionally been used for the study of ion molecule reactions and
the qualitative analysis of ultra trace levels of organic compounds. Advances in technology have resulted
in the development of small, rugged, and dependable cells using this technology. These advances have
allowed the use of this technology in industrial applications, where superior performance characteristics
have been achieved when compared to traditional monitoring methods. The ability to IMS to provide
real-time response, specificity, low temperature performance, and low maintenance of IMS-based
devices present decided advantages over electrochemical, paper tape detection, UV, and GC/MS
systems. IMS has the advantage of active sampling without moving parts.
Maintenance disadvantages of techniques such as electrochemical cells and papertape detectors are thus
overcome by the elimination of expendables. Most IMS instruments are under microprocessor control,
allowing the same basic configuration to be used for the specific detection of a wide variety of gases.
Specificity is achieved by programming the instrument to monitor the unique drift time for the
compound of interest. An algorithm converts the peak heights to a concentration by way of a calibration
table. Thus, even nonlinear responses are converted into a linear output. The concentration is displayed
on the front of the instrument and is also converted to a 4 to 20 ma signal for remote monitoring.
Although drift has not been seen to be a problem, recalibration is easily achieved in a two step
semi-automated procedure.
In operation, ambient air is drawn in the IMS instrument through a semi-permeable membrane on the
outside of the cell by use of a sampling pump. The membrane allows materials of interest to pass into
the detection cell while attenuating many possible interferents. Purified dry air from a self-contained
scrubbing system sweeps the membrane on the inside of the cell and delivers the sample to the reaction
region. The sample, consisting of one or more components, is ionized by reactions with a weak plasma
of positive and negative ions, formed by ionization of the purified air by a radioactive source. The
ionized sample molecules and reactant ions drift through the cell under the influence of an applied
electric field. A shutter grid allows periodic introduction of the ions into a drift tube where they separate
based on charge, mass, and shape. Smaller ions move through the drift tube faster than larger ions and
arrive first at the detector. The ability of an ion to move through another gas is called "mobility."
Because different ions have different mobilities, the ions arrive at the collector with different drift times.
The current created at the detector is amplified, measured as a function of time, and a spectrum is
generated. The mobility of the molecules can then be determined using pattern recognition algorithms
using a computer or microprocessor to analyze and compare features of the IMS signature with
information stored in memory. The electric field is periodically reversed so that ions of both polarities
can be studied.
8.3 Diffusion-Limited Technique (Passive Sampling Devices)
Passive sampling devices (PSDs) have been used extensively over the past decade by industrial
hygienists to assess the effects of respiratory exposures to hazardous pollutants on workers. Only
recently, however, has there been interest in using PSD's as part of a landfill gas monitoring program.
To obtain an accurate estimate of organic/inorganic species, the EPA has developed a PSD monitor. The
device is unobtrusive and lightweight. It operates quietly, and places little or no burden on the sampling
system. Passive devices, which require no pump, are much lighter in weight than traditional devices and
are not power-limited. They have the additional advantages of small size and relatively low cost, which
make them ideally suited as personal exposure monitors for toxic chemicals in air, bore-hole monitoring,
and unattended area monitoring, especially when electrical power sources are not readily accessible.
Passive air monitors may be either permeation or diffusion-controlled. In each ease, a collector or
sorbent material is separated from the external environment by a physical barrier that determines the
sampling characteristics ofthe device. Permeation-limited devices employ a membrane in which the test
compounds are soluble. Because of this solubility requirement, it is possible to achieve some selective
function with permeation devices by choice ofthe membrane material. However, because of solubility
variation even within a congeneric series of compounds, permeation devices must be calibrated for each
individual chemical that is sampled.
With diffusion-limited devices, the collector is isolated from the environment by a porous barrier
containing a well-defined series of channels or pores. The purpose of these channels is to provide a
geometrically well-defined zone of essentially quiescent space through which mass transport is achieved
A-33
-------
Guidance for Evaluating Landfill Gas
solely by diffusion. As a general criterion for this condition, the length/diameter ratio (L/D) of the pores
should be at least three.
Despite the potential limitations of applying passive monitors to quantitatively measure air pollutants,
these devices have in recent years been used quite successfully in ambient and indoor monitoring
applications. Their application to ambient atmospheres, which requires detection limits from 0.1 to 50
ppbv, presents a greater challenge. Most commercial devices use activated carbon as the collector.
Solvents such as carbon disulfide or a mixture of CS2 in methanol must be used to desorb the chemicals
for analysis. Concentration by evaporation of the solvent extract is impractical for the analysis of VOCs.
Consequently, carbon-based commercial dosimeters generally do not have adequate sensitivity for
ambient air monitoring.
8.4 Radial Plume Mapping
These techniques were developed in research and development programs funded by the EPA National
Risk Management Research Laboratory (NRMRL). Detailed spatial information is obtained from
path-integrated ORS measurements by the use of optimization algorithms. The method involves the use
of an innovative configuration of non-overlapping radial beam geometry to map the concentration
distributions in a plane. This method, radial plume mapping (Hashmonay et al., 1999; Wu et al., 1999:
Hashmonay et al., 2002), can also be applied to a vertical plane downwind from an area emission source
to map the crosswind and vertical profiles of a plume. By incorporating wind information, the flux
through the plane is calculated, which leads to an emission rate of the upwind area source. The RPM
method can be used with any ORS instrument. An extensive validation study of the RPM method was
conducted during 2003 using tracer gas releases, and the results of this validation study led to the
creation of an EPA draft protocol, which is currently under review by EPA, for using the RPM method
to characterize emissions from area sources.
8.4.1 Horizontal Radial Plume Mapping (HRPM). The radial plume mapping approach provides
spatial information to path-integrated measurements by optical remote sensing. This technique yields
information on the two-dimensional distribution of the concentrations in the form of chemical-
concentration contour maps (Hashmonay et al., 1999; Wu et al., 1999; Hashmonay et al., 2002). This
form of output readily identifies chemical hot spots, the location of high emissions. This method can be
of great benefit for performing site surveys prior to remediation activities.
HRPM is usually performed with the ORS beams located as close to the ground as practical. This
enhances the ability to detect minor constituents emitted from the ground because the emitted plumes
dilute significantly at higher levels above the ground. The survey area is divided into a Cartesian grid
of n times m rectangular cells. A mirror is located in each of these cells, and the OP-FTIR sensor scans
to each of these mirrors in the order of either increasing or decreasing azimuth angle, dwelling on each
for a set measurement time. The path-integrated concentrations measured at each mirror are averaged
over a several scanning cycles to produce time-averaged concentration maps. Meteorological
measurements are made concurrent with the scanning measurements.
Figure A-3 represents a typical horizontal RPM configuration in which n = m = 3. The lines represent
the nine optical paths, each terminating at a mirror (Hashmonay et al., 2002).
8.4.2 Vertical Radial Plume Mapping (VRPM). The vertical radial plume mapping method maps the
concentrations in the vertical plane of the measurement. By scanning in a vertical plane downwind from
an area source, one can obtain plume concentration profiles and calculate the plane-integrated con-
centrations. The flux is calculated by multiplying the plane-integrated concentration by the wind speed
component perpendicular to the vertical plane. The flux leads directly to a determination of the emission
rate (Hashmonay et al., 1998; Hashmonay and Yost, 1999, Hashmonay et al, 2001). Thus, vertical
scanning leads to a direct measurement-based determination of the upwind source emission rate.
Figure A-4 shows a schematic of the experimental setup used for vertical scanning. Several mirrors are
placed in various locations in a vertical plane in-line with the scanning OP-FTIR. Two of the mirrors
used in the configuration are mounted on a scissors jack (which is a piece of equipment used to create
a vertical platform for mounting mirrors in the configuration). The location of the vertical plane is
selected so that it intersects the mean wind direction as practical.
A-34
-------
Emissions from Closed or Abandoned Facilities
70
60 -
50
40 -
30 -
20 -
10 -
0 -
-10
-20 0 20 40 60 80 100
Figure A-3. Overhead View of an Example HRPM Configuration.
Monostatic ORS
Instrument
Vertical
Retroreflectors
Ground
Retroreflectors
Figure A-4. Example of a Vertical RPM Configuration.
A-3 5
-------
Guidance for Evaluating Landfill Gas
8.4.3 Open-Path Fourier Transform InfraredSpectroscopy (OP-FTIR). The OP-FTIR Spectrometer
combined with the RPM method is designed for both fence-line monitoring applications and for real-
time, on-site, remediation monitoring and source characterization. An infrared light beam, modulated
by a Michelson interferometer is transmitted from a single telescope to a retro-reflecting mirror target,
which is usually set up at a range of 100 to 500 meters from the transmitter. The returned light signal
is received by the single telescope and directed to a detector. The light is absorbed by the molecules in
the beam path as the light propagates to the retro-reflecting mirror and again as the light is reflected back
to the analyzer. Thus, the round-trip path of the light doubles the chemical absorption signal.
8.4.4 Open-Path Tunable Diode Laser Absorption Spectroscopy (OP-TDLAS). The OP-TDLAS
instrument is an interference free technique for making continuous concentration measurements of many
gases. Concentrations in the range of part per billions are suitable for measurements over an open path
up to 1 km, for gases such as CO, CO2, NOX, NH3, and CH4. The laser emits radiation at a particular
wavelength when an electrical current is passed through it. The light wavelength depends on the current
and therefore allows scanning over an absorption feature and analyzing for the target gas concentration
using Beer's law. Recent development of a multiple channel OP-TDLAS instrument allows scanning
electronically very fast (few seconds) among many beam-paths (presently, 8 beams). The multiple
channel OP-TDLAS applies a small 4-inch telescope, which launches the laser beam to a retro-reflecting
mirror. The laser beam is returned by the mirror to the telescope, which is connected with fiber optics
to a control box that houses the laser and a multiple channel detection device. The potential advantages
of the OP-TDLAS instrument include near real-time air concentrations, no requirement for sample
collection, no additional analytical costs (i.e., laboratory costs), and concentrations that are
path-averaged values instead of concentrations at specific sampling points. The disadvantage of the
OP-TDLAS instrument is the ability to measure only one gas (in most cases) with one instrument.
8.4.5 Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS). The UV-DOAS is a subset
of long-path absorption Spectroscopy. In long-path absorption, a known intensity of light is generated
and allowed to propagate through a predetermined space. UV-DOAS technology utilizes the ability of
molecules to absorb light as a basis for calculation of the concentration of molecules in a gas, and the
attenuation of light energy through the path length is assumed to be due to absorption by the target
species. The basic concept of the DOAS is the same as the above except multiple wavelengths are
measured. Concentrations are determined on the basis of Lambert-Beer's law. The light from the
receiver is sent over an optic cable to the spectrometer, where it is resolved into spectra by a grating. For
the specific wavelength area, about 100 spectra are obtained per second. These spectra are converted to
digital signals and stored in a multi-channel memory. The computer compares the spectra for each
wavelength with a precalibrated reference spectrum. The system can store data for a maximum of 1,000
wavelengths. On the basis of these comparisons, a program calculates the quantities of the substances
which are being monitored. The computer reports the margin of error for each measurement. Currently,
the simultaneous measurements for up to 50 organic/inorganic compounds are possible. The reference
beam is created mathematically, and only the measurement beam is necessary. By recording the various
shades of color in the light and analyzing them mathematically, the concentration of the different
molecules can be determined with great accuracy.
9.0 Real-time Monitoring for Suspended Particulate Matter
Suspended particulate matter (SPM) must be considered as part of the APA because PM can be emitted
from landfills that do not have covers. It is understood that particulate emissions from landfills normally
do not constitute a major source of COPCs. However, if the waste is excavated or disturbed by
mechanical processes, one should consider the possibility of toxic PM emissions as part of the APA.
This section will discuss four of the more popular real-time methods for monitoring ambient air
particulate matter. They are:
• Forward scatter near-infrared (RAM and MINIRAM) monitors,
• Cascade impaction-piezoelectrical balance monitors,
• Beta attenuation monitors, and
• TEOM particle monitors.
9.1 Forward Scatter Near-Infrared (RAM and MINIRAM)
The RAM is a stationary or portable self-contained aerosol monitor whose sensing principle is based on
the detection of near-forward scattered electromagnetic radiation in the near-infrared. The instrument
uses a pulsed semiconductor light emitting diode which generates a narrow-band emission centered on
A-36
-------
Emissions from Closed or Abandoned Facilities
940 nm. The scattered radiation is detected by means of a silicon photo-voltaic-type diode with integral
low noise preamplifier.
Signal processing is performed by employing a lock-in synchronous scheme that allows continuous
cancellation of detector and electronic circuitry drift and noise. The standard instrument is supplied with
three selectable ranges (0-2, 20, 200 mg/m3) to allow for high resolution over a concentration range of
five decades. Further readout flexibility is obtained through four selectable time constants (0.5,2,3 and
32 seconds); thus, the operator has complete control over both the range and the speed of response.
The concentration data are continually displayed by a three and one-half digit liquid crystal display.
Included in the display are two diagnostics to alert the operator; a flashing "k" on the right-hand side of
the display indicates that the reference scatterer is inserted, and a flashing "VDC" indicates a low
battery voltage. An analog voltage (0-10 FDC) output proportional to the concentration is also available
for strip chart recording, data logging and/or telemetry.
The flow system employs a diaphragm pump to produce the desired sampling flow to 2 L/min. A
secondary clean air steam of 0.2 L/min provides continuous flushing of filtered air over all critical
optical surfaces. Also, the entire inlet airflow is filtered during a zero check to effect a self-cleaning of
the optical sensing chamber. The flow meters are provided to allow for continuous monitoring of the
total and filtered flows.
The instrument is designed to operate continuously for 6 to 8 hours after the internal battery has been
fully charged. A separate charger is provided with which the RAM can operate indefinitely from the AC
line.
The MINIRAM (Miniature Real-time Aerosol Monitor) is a light scattering aerosol monitor of the
nephelometric type (i .e., the instrument continuously senses the combined scattering from the population
of particles present within its sensing volume—approximately 1 cm3—whose dimensions are large
compared with the average separation between the individual airborne particles).
The MINIRAM operating principle is based on the detection of scattered electromagnetic radiation in
the near infrared. The MINIRAM uses a pulsed gallium (GA) light emitting source, which generates a
narrow-band emission centered at 880 nm. This source is operated at an avenge output power of about
2 mW. The radiation scattered by airborne particles is sensed over an angular range of approximately
45 to 95 degrees from the forward direction by means of a silicon-photovoltaic hybrid detector with
internal low-noise preamplifier. An optical interference-type filter is incorporated to screen out any light
whose wavelength differs from that of the pulsed source.
In operation, air surrounding the MINIRAM passes freely through the open aerosol sensing chamber as
a result of air transport caused by convection, circulation, and ventilation. The MINIRAM requires no
pump for its operation, and the scattering sensing parameters have been designed for preferential
response to the particle size range of 0.1 to 10 |im, ensuring high correlation with standard gravimetric
measurements of both the respirable and inhalable size fractions. Optional flow accessories are available
for applications requiring specific inertial particle precollection, extractive sampling, concurrent filter
collection, etc.
9.2 Cascade Impaction (Piezoelectical Balance)
The cascade impaction piezoelectical balance air particle analyzer is an aerosol particle mass con-
centration and size distribution analyzer that gives data in real time. The monitor is based on the
principle of cascade impaction. However, it achieves its real-time capability by using the piezoelectric
quartz crystal microbalance (QCM) mass sensor to electronically weigh particles in each impactor stage.
The sensing component consist of dual-crystal design involving a sensing and reference crystal. Only
one of the two unsealed crystals collects particles. The other acts as a reference to null out temperature
and humidity effects. The frequency difference between the crystals is the QCM signal, and it changes
in proportion to particles collected on the sensing crystal. A built-in microcomputer process the QCM
signals and provides the data output in a printout.
The QCM sensing crystal with particles on it can be recovered from the sampler after a period of time
and analyzed for metals through scanning electron microscopy (SEM) and energy dispersive X-ray
(EDX) spectroscopy.
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Guidance for Evaluating Landfill Gas
9.3 Beta Attenuation Monitor
The beta attenuation monitor samples at ambient temperatures, relative humidities, and gas
concentrations to minimize particle volatilization biases. These monitors operate at a low-volume flow
rate (nominally 16.7 L/min) using either a virtual impact or cyclonic flow operating principal to
determine the 50 percent cut-point. For beta attenuation monitors, low energy beta rays (i.e., 0.01-0.1
MeV electrons) are focused on deposits on a filter tape and attenuated according to the approximate
exponential function of particulate mass (i.e., Beer's Law). These automated samples employ a
continuous filter tape. Typically, the attenuation through an unexposed portion of the filter tape is
measured, and the tape is then exposed to the ambient sample flow where a deposit is accumulated. The
beta attenuation is repeated, and the difference in attenuation between the blank filter and the deposit
is a measure of the accumulated concentration. Blank corrected attenuation readings can be converted
to mass concentrations for averaging times as short as 30 minutes. Although these monitors are capable
of producing half-hourly average mass concentrations, a 24-hour averaging period is required for typical
ambient concentrations to obtain sufficient particulate deposition for an accurate determination. The two
types of beta-gauges are the Adersen Beta-Gauge (Inorganic Compendium Method 10-1.1) and the
Thermo Environmental, Inc. (formally Wedding and Associates) Beta-Gauge (Inorganic Compendium
Method 10-1.2).
The Andersen monitor directly measures particulate mass at concentrations of 0.005-20 mg/m3 on a
real-time basis. With the Andersen instrument, ambient air enters the monitor through an inlet head. The
inlet head can be designed for either total suspended particulate matter (TSP), PM}0, or PM2 5 sampling.
If the sampling requirement is for PM10, then the flow rate is 16.7 L/min. The air containing the PM
enters the instrument where it is pulled through a glass fiber filter tape, and the particles are deposited
on the tape. Low level beta radiation is emitted from a stainless steel capsule containing Krypton-85 gas
towards the filter tape containing deposited particulate matter. The particulate matter on the tape reduces
the intensity of the beta radiation reaching the measuring chamber on the opposite side of the tape. To
compensate for the effect of the filter tape on the reduction of the level of beta radiation, the source
directs a second beam of beta particles through a "foil" that mimics clean filter tape to a second
measuring chamber (compensation chamber). No air flow is directed to the compensation foil, so the
effect of the foil on the beta radiation intensity remains constant. The instrument compares the
measurement of the compensation foil to the measurement of the filter tape with deposited PM to
determine the mass of the particulate matter. Because changes in temperature, pressure, or humidity can
affect measurement of PM on the filter tape, the measurements made through the compensation foil are
impacted to the same degree. The foil measurements provide baseline data to compensate for these
meteorological effects. Therefore, this monitor is less sensitive to temperature, pressure, and humidity
fluctuations than some other types of continuous particle monitors because the compensation foil
measurements provide baseline data. Because the measuring mechanism lacks moving parts, the
instrument is not as sensitive to vibrational effects as other types of continuous particulate monitors. The
Andersen monitor has certain limitations or interferences. In high-humidity or rainy climates, water may
collect on the filter tape and cause artificially high mass readings. In these same climates where the
instrument is housed in an air-conditioned environment, the ambient air inlet tube should be insulated
to avoid condensation or the inlet tube should be heated to ensure that any water drawn into the unit is
vaporized.
The Thermo Environmental, Inc. beta gauge operates under the same basic principles as the Andersen
monitor, but with some differences. The Thermo monitor can measure ambient mass concentration with
a resolution of about 3 |lg/m3 for a 1-h sampling period. A constant volumetric flow rate for the PM10
inlet of 18.9 L/min is used compared to the 16.7 L/min for the Andersen unit. A major difference
between the two monitors is the beta source. The Thermo monitor uses a carbon-14 beta source
compared to Krypton-85 gas for the Andersen monitor. The carbon-14 source does not require a license
by the Nuclear Regulatory Commission, whereas the Krypton-85 does.
9.4 TEOM Particle Monitor
Different from the beta-gauges, the Rupprecht and Pataschnick (R&P) real-time particulate monitor is
based upon atapering element oscillating microbalance (TEOM) as the filter-based measurement system
to continuously measure particulate mass at concentrations between 5 pg/m3 and several grams per cubic
meter on a real-time mass monitoring basis. The instrument calculates mass rate, mass concentration,
and total mass accumulation on exchangeable filter cartridges that are designed to allow for future
chemical and physical analysis. In addition, this instrument provides fhourly and daily averages. This
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Emissions from Closed or Abandoned Facilities
system operates on the principal that particles are continuously collected on a filter cartridge mounted
on the tip of atapered hollow glass element. The element oscillates in an applied electric field. With this
monitor, particle-laden air enters through an air inlet and then passes to the sensor unit containing the
patented microbalance system. The inlet system is equipped with a sampling head for either TSP, PM10,
or PM25.
In operation, the sample stream passes into the microbalance system, which consists of a filter cartridge
(!/2 inch diameter) and oscillating hollow tube, where the stream is heated to a predetermined
temperature. The filter cartridge is a 1A inch diameter thin aluminum base (foil-like) assembly. A water
resistant plastic cone, which fits onto the oscillating element, is attached to the aluminum base. An
automatic flow controller pulls the sample stream through the monitor at flow rates between 0.5 and 5
L/min. The wider end of the hollow element is fixed to a platform and is vibrated at its natural
frequency. The oscillation frequency of the glass element is maintained based on the feedback signal
from an optical sensor.
As mass accumulates on the filter cartridge, the resonant frequency of the element decreases, resulting
in a direct measurement of inertial mass. Based on the direct relationship between mass and frequency,
the monitor's microcomputer calculates the total mass accumulation on the filter and the mass rate and
mass concentration in real-time.
The TEOM monitor is very sensitive to mass concentration changes and can provide precise measure-
ments for sampling duration of 1-h or less. To achieve this level of precision, the hollow glass element
must be maintained at a constant temperature to minimize the effects of thermal variations. Because the
instrument's primary operating mechanism is the microbalance system, the instrument should be isolated
from mechanical noise and vibration. The operating temperature of the element can be lowered to
minimize the potential particle loss bias for more volatile compounds but must be maintained above the
maximum ambient temperature encountered during the field sampling.
Table A-8 outlines the various weaknesses and strengths of each of the discussed systems. The RPM
and/or the OSC should examine each of these items before incorporating them into a MSW landfill gas
monitoring program.
10.0 Federal Reference Method 21
The various fugitive emission regulations—New Source Performance Standards (NSPS), National
Emission Standards for Hazardous Air Pollutants (NESHAP), and state implementation plans
(SIPs)—require the use of Federal Reference Method 21 (FRM 21) for determining the concentrations
of fugitive VOCs with reference to methane. In particular, FRM 21 is specified as the sampling and
analytical methodology for the fugitive leak detection program applicable to petroleum refineries. This
same technology is now being applied to the monitoring of fugitive CH4 and VOC emissions at MSW
landfills. It is Therefore imperative to become familiar with FRM 21 and its application to landfill gas
monitoring.
FRM 21 can be found in 40 CFR 60, Appendix A. 40 CFR 60 covers the NSPS and EG, and Appendix
A contains the Federal Reference Methods that must be used in determining emission compliance with
the limits specified in the rules. FRM 21 does not recommend specific analyzers or manufacturers, but
it does define analyzer performance specifications.
10.1 Portable VOC Analyzers
Portable VOC analyzers take two forms: (1) single hand-held units containing all the instrumentation
in one unit, and (2) multi-component units that separate the inlet from the analytical section of the
system by way of an umbilical cord. This approach allows greater flexibility in the field to reach difficult
locations.
Each analyzer comprises two functional units: the probe mechanism and the analytical assembly. In
addition, each analyzer should contain a power supply (battery) and support gas(es). In the case of the
multi-component analyzer, there should be an umbilical connector between the probe and the analysis
unit, as illustrated in Figure A-6.
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Table A-8. Weaknesses and Strengths of Real-Time Monitoring Systems Applicable to MSW Landfill
Gas Monitoring.
Monitoring
Technique
Weakness
Strength
NDIR
NDUV
Electrochemical
GFC
OP-FTIR
Ion Mobility Spect.
(IMS)
GC/MS
Remote Monitoring
Passive Sampling
Devices
Other gases absorb in spectral region.
Optical maintenance high.
Pressure/Temperature sensitive.
Other gases absorb in spectral region.
Narrow absorption bands limit detection.
High-temperature required to detect O2.
Cell interface must remain moist.
Requires pressure cells in monitoring.
Gas cells may leak.
Applicability limited to small number of gases .
Must use library comparison of spectra.
Complex spectra interpretation.
1 Inability to discriminate between two
compounds with similar mass.
1 Linear range small.
1 Variable day-to-day response.
1 Gases must be able to accept an electrical
charge in order to be detected.
1 Greater equipment cost.
1 Requires high vacuum source.
1 Routinely requires preconcentration of sample.
1 Operating cost are higher than traditional
methods.
1 High degree of education required to operate
system.
1 Must have high concentration or integrated over
a longer time period than traditional systems.
1 Many interferences which have not been
completely studied.
Relative low cost.
Can be applied to multiple gases.
Use of differential absorption.
More sensitive than NDIR.
Water not an interference.
Inexpensive and portable.
Cells can be easily interchanged
or replace for different
pollutants.
• Multiple cells in one analyzer
allows flexibility.
• Improved specificity over
conventional NDIR/NDUV.
• Ability to monitor various
constituents at one time.
• Ability to analyze complex
spectrum.
• Can be used as extractive or
remote monitor.
• No consumables.
• On-site fast/instantaneous
analysis.
• No moving parts.
• Low detection limits.
• Sample matrix interference may
be minimized by GC.
• IMS universal detector.
• Positive compound identification.
• Systems now very portable.
• System more specific to analyte
identification.
• Less operator interpretation.
• More representative of emissions
in open path.
• On-line 24 hr per day.
• Multi-pollutant analysis routine.
• On-site analysis; no off-site
analysis required.
• Lost cost.
• Small and less obtrusive,
lightweight.
• No pump requirements.
• Quiet operation.
• Easy to use.
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Emissions from Closed or Abandoned Facilities
Figure A-6. Typical Federal Reference Method 21 Portable Fugitive VOC
Analyzer.
The objective of the probe assembly is to extract a representative fugitive emission sample from the
source (i.e., inlet or outlet to LFG combustion equipment, bore hole/soil gas sampling, landfill surface
monitoring, or ambient air monitoring) and move it to the detector for analysis. To minimize dilution
of the gas stream as it is being pulled into the system, FRM 21 specifies that the probe opening cannot
be greater then 1/4 inch outside diameter. Optional components of the probe and the interface assembly
include meter-readouts and particulate filters.
The analytical assembly normally contains the detector, electronics processing boards, pump, flow
control devices, high pressure gas cylinders, power supply, and service panel.
FRM 21 does not specify a particular manufacturer's instrument to be used in determining CH4 and VOC
emissions. Rather, FRM 21 requires that portable VOC detection equipment must meet specific
instrumentation specifications and certain performance criteria.
10.2 Instrument Specifications
FRM 21 has eight instrument specifications that must be met in order for the portable instrument to be
part of an emission monitoring program:
• VOC monitor response to the process chemical being tested,
• Measurement range must include the "leak definition,"
• Scale resolution,
• Response time,
• Intrinsically safe,
• Probe dimensions specifications,
• Response factor requirements, and
• Accuracy requirements.
10.2.1 Monitor Response. The portable VOC analyzer must be able to respond to compounds being
processed and regulated. Two of the most commonly used detectors in fugitive VOC monitoring are
• Flame ionization detector and
• Photoionization detector.
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Guidance for Evaluating Landfill Gas
By far the most widely used detector for portable total hydrocarbon analysis is the FID. The gas sample
is introduced into a hydrogen/air flame, the CH4 and VOCs are burned, ionized, and detected. The
technique is specific for organic compounds and gives relatively uniform response for the various
compounds.
The PID is the second most popular VOC analyzer. The PID analyzer also ionizes the VOCs in the gas
stream. Instead of burning the gas stream, it uses high intensity ultraviolet light (UV). Since the
ionization potential of a particular compound must be less than the ionization of the UV light energy in
order to be detected, this means that the PID is not as universal a detector as the FID.
10.2.2 Measurement Range. The portable fugitive VOC analyzer must have a measurement range that
encompasses the leak definition for landfill gas applications; this means that the instrument must be able
to detect fugitive CH4 and VOCs as high as 500 ppmv above background.
10.2.3 Scale Resolution. The third instrumentation specification is that the scale reading on the
analyzer must be readable to within ±2.5 % of the specified leak definition concentration when
performing a "no detectable emission" survey. For a leak definition of 500 ppmv, this means that the
scale reading must be readable to 12.5 ppmv.
10.2.4 Response Time. The response time (RT) instrument specification is defined as the time interval
from a step change in VOC concentration at the input of the sampling system to the time at which 90
percent of the corresponding final value is reached and displayed on the instrument readout meter. In
operation, zero gas is introduced into the instrument and a stable reading is obtained. Then, quickly
switch to the calibration gas and measure the time from switching to the time when 90 percent of the
final stable reading is attained. The user then performs this activity two additional times to obtain an
average of 3 readings for the average response time. FRM 21 specifies that the average must be less than
30s.
10.2.5 Safety. The instrument must be intrinsically safe. This is a very important requirement because
of CH4 emissions at MSW landfills and because many of the organic emissions are explosive.
10.2.6 Probe Dimensions. To minimize biases from dilution, the maximum outside diameter (OD) of
the sample probe can be no greater than % inch. A larger probe OD has the ability to pull surrounding
air into the probe, thus diluting the sample and producing a bias in the sampling system. The
specification also states that the pump in the instrument must be able to draw sample gas at a rate of 0.10
to 3.0 L/min into the 1/4 inch OD probe opening. The flow rate range was selected after field studies
indicated that this range limited the biases of the sampling technique due to sample extraction.
10.2.7 Response Factor (RF). This instrument specification requires that the RF be less than 10 for the
specific VOC being tested. This specification requires the user to use an instrument that responds within
a certain level of reliability and accuracy to the VOC being monitored. The specification requires the
user to determine the RF for each of the VOCs being monitored.
A response factor of 1.0 means that the instrument readout is identical to the actual concentration of the
chemical in the gas sample. As the RF increases, the instrument readout is proportionally less than the
actual concentration. A high RF means that the instrument does not detect the compound very well. A
low RF means that the instrument is very sensitive to the compound of interest.
10.2.8 Accuracy. Similar to the response time test, this instrument specification associated with
calibration precision (accuracy) requires a calibration gas to be introduced into the analyzer three times
and that the average response of the analyzer must be within 10 % of the certified calibration gas value
recorded on the calibration gas cylinder. This specification assures that the user is using a well
characterized instrument in determining CH4 and VOC concentrations.
10.3 Performance Criteria
FRM 21 requires the following checks for each analyzer to ensure that the analyzer meets FRM 21
performance criteria:
• The response factor (RF) must be determined for each compound that is to be measured before
placing the analyzer into service.
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• A response time (RT) test must be performed prior to placing the analyzer into service and whenever
there is a change to the sample pump or flow system of the analyzer.
• A calibration precision test must be completed prior to placing the analyzer into service and every
3 months thereafter (or at the next use, whichever is later).
The performance criteria specifications require that a calibration precision test be performed before the
analyzer is placed-in-service and at a minimum every 3-months.
The calibration precision test is performed by three analyses of zero gas being introduced, then an
analysis of the certified calibration gas (CH4) being introduced into the analyzer to determine the
analyzer's response to the calibration gas. The acceptance criteria is ±10 % of the certified calibration
gas concentration as recorded on the gas cylinder or on the certification papers.
Calibration tests must be performed prior to placing the monitor in service and should be done at the
inspector's dedicated facility for maintaining monitors. The basic components for performing calibration
checks on the analyzer are
• NIST traceable gas cylinders,
• Tedlar bags,
• Appropriate tubing, and
• Field portable VOC analyzer.
Detailed procedures are described in the regulations and with the manuals that accompany the analyzers
covering the proper operation, use and storage of the analyzer.
10.4 Selecting an Analyzer
There are no specific rules for selecting an analyzer since many factors that enter into the selection are
agency/site specific. However, the list below provides some items to consider when selecting an analyzer
to place in service as part of a landfill emission monitoring program.
• Determine the amount of use and type of emission points to monitor as part of the landfill emission
monitoring program.
• Specify needs for the portable fugitive analyzer to be used in order to minimize time and labor
associated with landfill gas monitoring requirements (i.e., bar code scanning needs, audible alarm
level capability, data logger capability, etc.).
• Size, weight and bulk of instrumentation.
• Ease of instrument data logger interface with project data management software.
• Enhanced speciation capability for future VOC emission inventory.
• Durability of analyzer, power supply system, and data logger under unique conditions (for example,
cold weather impacts).
• Ease of operation, calibration, and on-the-job repairs.
• Level of manufacturer's technical support.
11.0 Application of Different Sampling Techniques
Monitoring at a MSW landfill may involve landfill surface monitoring, soil gas monitoring, and LFG
combustion equipment monitoring.
11.1 Landfill Surface Monitoring
Landfill surface monitoring is usually performed to verify that the LFG collection system is working
adequately and that there are no detectable leaks in the system. Using a FRM 21 portable analyzer allows
the investigator to examine the property and certify control of fugitive emissions. However, the likeli-
hood of landfill surface monitoring success depends on how the investigator performs the soil gas
sampling methodology. The application of the methodology should be guided by the objectives of the
project and the perceived spatial and temporal array of the potential sampling targets. Of course, if the
landfill is controlled by an impermeable membrane, this type of sampling is unnecessary except at
membrane seams, suspected openings or tears, and at any membrane penetration (i.e., LFG vents).
Historically, the ability to obtain data distributed over a geographic area allows the investigator to obtain
scientific and accurate data so regulatory decisions can be made. The use of a grid design with patterns
of variable design and spacing can serve very effectively toward the objectives of obtaining a
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Guidance for Evaluating Landfill Gas
representative sample from a large geographical area. This approach has allowed the investigation of
large landfills to be accomplished at a very reduced cost with limited manpower.
First round sampling should consist of detection of methane and total NMOCs. Based on the results of
the first-round monitoring, a second round sampling plan should be developed to evaluate constituents
which comprise the LFG target compound list of COPCs.
11.1.1 Grids. It has been proven that obtaining spatial and temporal concentrations of targeted COPCs
from the landfill surface allows the investigator to accurately determine the condition of the landfill and
the likelihood of future emissions. Sampling in grid patterns of variable design and spacing can be a very
effective way to provide the data needed to meet the project data quality objectives (DQOs). The
selection of the grid size largely depends on the relationship between the project DQOs and the project
budget. Grid sizes as small as 10 x 30 m have been used when the boundaries of the waste or
groundwater plume are on the order of 300 x 300 m. On the other hand, for landfills that are
approximately 23,000 m2, the grid cells may range up to 100 x 100 m.
As illustrated in Figure A-7, atypical landfill surface area may be divided into squares or alternatively
one may circumnavigate the perimeter using a declining spiral technique. In effect, divide the landfill
surface in a pattern of squares or polygons with equal spacing. Experience, indicates that a 30m square
is adequate in addressing landfills up to 1000 x 1000 m. The tendency exists for investigators with
constrained budgets to utilize overly large grid cell spacings, resulting in inadequate, over-interpreted
data supporting doubtful conclusions.
While most of the effort is associated with characterizing the emissions from the landfill surface, the
investigator must also be aware that the regulations specify that the limit of 500 ppmv above background
is considered an emission point. As specified in the NSPS/EG requirements, the investigator must collect
an upwind and downwind sample during the investigation to document environmental concentrations
prior to the landfill surface monitoring. To obtain an upwind or downwind sample, go outside the
boundary of the landfill at a distance of at least 98 ft (30 m) from the boundary limits. Position the probe
into the wind and record the reading. This reading becomes the background concentration.
Figure A-7. Grid Landfill Surface Monitoring Route.
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Emissions from Closed or Abandoned Facilities
11.1.2 Sampling Methods and Procedures. A maximum surface concentration of 500 ppmv CH4 above
background indicates proper operation of the landfill cap and recovery system. The following test
methods and procedures should be followed, as outlined in 40 CFR 60, Appendix A, FRM 21.
A portable hydrocarbon analyzer that satisfies 40 CFR 60, Appendix A, FRM 21 should be used to
determine the CH4 concentration at each sampling point, and the instrument should be operated
according to manufacturer's instructions.
1. Assemble and start-up the instrument according to manufacturer's instructions.
2. Evaluate the response factor with a known concentration of certified methane gas and document.
3. Calibrate with a certified methane standard reference (80% of emission limit), also using zero gas
as background, certifying that the instrument returns to zero.
4. Repeat twice more to obtain three measurements of the methane standard and zero gas
concentration.
5. Calculate three individual and one average response factors.
6. Calibration Precision.
• Make three measurements by alternately using zero gas and calibration gas.
• Calculate the calibration algebraic difference between the meter reading and the known value.
• Calculate calibration precision (%).
7. Response Time.
8. Leak-check sample system.
9. Set electronic zero and alarm levels (if applicable).
10. Set zero using background (<10 ppm VOC) air.
• Sampling should be performed during typical meteorological conditions.
• Measure the background methane concentration by moving the analyzer probe inlet upwind,
outside the boundary of the landfill at a distance of at least 98 ft (30 m) from the limits of the
landfill. Record on the field test data sheet.
• The predetermined grid layout of the landfill with the grid mark separations no more than 30m
apart are the sampling points.
• The field portable detector probe should be no greater than 1 inch from the surface of the
landfill.
11.1.3 Sampling Grid Pattern. A pattern of parallel lines approximately 98 ft (30 m) apart should be
established over a maj ority of the surface area of the landfill that contains buried refuse. Per 40 CFR Part
60, Section 60.53 (c)(d), areas with steep slopes or dangerous areas will not be monitored. The tester
should walk the path and record a sampling result at approximately 98 ft (30 m) intervals as illustrated
in Figure A-7. The tester should first obtain a reading upwind of the site for background information.
Then, the tester should start at a known location and begin walking the perimeter of the site, noting
readings every 30 m. Perform parallel surveys until the complete landfill surface has been evaluated
using the grid approach. Any cracks, holes, passive vents breaches in the surface, or interfaces with
undisturbed native soil should also be tested.
Any reading 500 ppmv or more above background should be noted, and the locations of the readings
should be marked and recorded. Landfill cover maintenance or adjustments to the LFG collection system
should be made, and the location should be re-monitored within 10 calendar days of the initial
exceedance. If remonitoring the location shows a second high reading, additional corrective action
should then be taken, and the location should be remonitored within 10 days of the second high reading.
A proposed corrective action plan and corresponding time line should then be prepared for any location
where monitored methane concentrations equal or exceed 500 ppmv above background three times
within a quarterly period.
11.1.4 Monitoring Frequency. Surface emissions testing for the entire landfill should be performed
quarterly.
11.1.5 Recordkeeping. The location and concentration of each high reading recorded during the surface
emissions tests should be reported in an annual report. The concentration recorded at each location for
which a high reading was recorded in the previous month should also be included in the annual report.
Reports and monitoring records should be maintained for a period of five years.
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Guidance for Evaluating Landfill Gas
11.2 Soil Gas Sampling
The Geoprobe sampling device has been accepted as a useful device for collecting soil, soil-gas, and
groundwater samples at specific depths below ground surface. The Geoprobe is attached to the rear of
a customized vehicle. In the field, the rear of the vehicle containing the Geoprobe is placed over the
sample location. The vehicle is hydraulically raised on its base, and the probe is pushed into the ground
as the weight of the vehicle is transferred to the probe. A built-in hammer mechanism allows the probe
to be driven to predetermined depths, up to50 feet.
Using the Geoprobe as the entry point into the landfill, soil gas sampling can be collected by two
techniques:
• Withdrawing a sample directly from the probe rods after evacuating a sufficient volume of air to
ensure that a fresh sample is being extracted.
• Collecting a sample through tubing attached by an adaptor to the bottom of the probe section. This
is the preferred method because it provides more reliable results.
The internal framework of the Geoprobe is illustrated in Figure A-8. The investigator has numerous
options by which to collect the sample:
• Whole-Air Active Sampling (Compendium Method TO-15). Using this configuration, a
specially-treated whole-air canister is attached to the outlet of the sampling line which has been
extended to a predetermined depth. If the canister has been previously evacuated to a pressure of-29
inches Hg, then the vacuum in the canister will withdraw the soil gas sample. Normal operation
would also include an in-line flow controller and a sintered stainless steel filterto minimize particles
becoming entrained in the canister atmosphere. This would allow time-integrated sampling over a
given time period depending upon the selected flow rate. A normal flow rate of 1.5 mL/min would
allow a 24-hour sample to be collected. The canister is then returned to the analytical laboratory
where CH4, NMOCs, and speciated organics are detected by a FID and GC/MS detectors. This
approach is suited to soil gas monitoring where the contaminant concentrations are expected to be
high and the vadose zone is highly permeable to vapors. If a Tedlar bag is used to collect the soil
gas vapors, then an external pump is needed to move the sample from the probe tip into the Tedlar
bag.
• Solid Adsorbent Sampling (Compendium Method TO-17). Solid adsorbent technology requires
the soil gas sample to be forced from the probe tip through the adsorbent where the COPCs are
trapped. This system is well suited to sites where the soil may be highly permeable to vapor and
where the contaminant concentrations may be lower than required when applying whole-air active
sampling. Using solid adsorbent technology allows one to collect more sample by extending the
sampling period in order to reach desirable detection limits. Adsorbent technology allows one to
concentrate the COPCs while allowing gas constituents that interfere with the analytical system to
pass through the sampling system. Adsorbent technology allows the investigator to select a
particular adsorbent for a unique list of COPCs. Common absorbents utilized in air monitoring
programs are:
- XAD-2/Tenax/Charcoal for general medium volatile organics (C6-C20),
- Fluorisil for chlorinated organics, and
- Carobosieve SIII for nonpolar, very volatile organics (C2-C5 hydrocarbons).
Once the COPCs have been retained on the sorbent, the sorbent is returned to the laboratory for
analysis by thermal desorption followed by GC/MC identification of speciated organics.
• On-line GC Monitoring (Compendium Method TO-12/14A). Direct on-line GC monitoring
allows the investigator to obtain real-time data of COPC concentrations. From on-line data, one can
plot concentration over time to study soil permeation rates. In addition, on-line sampling can be
performed for other constituents (i.e., CO, CO2, O2, HC1, C12 SO2, NOX, etc.).
• FRMs 18/25. FRMs 18 and 25, were developed for source emissions testing, are very similar to
Compendium Methods TO-17 and TO-15, respectively.
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Emissions from Closed or Abandoned Facilities
Swage
union
Sea!
\
4'
.a
3=6
Plastic liner
1/8" Stainless
x^steel tubing
Bore hole
Compendium Method
TO-5
(Canister)
Tedlar Bag
Technology
On-line GC
Compendium Method
TO-17
(Solid Adsorbent)
Federal Reference
Method 18/25
1'
Figure A-8. Geoprobe Bore-hole Sampling Technique With Sampling Methodology.
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Guidance for Evaluating Landfill Gas
The success of an active sampling approach to soil gas monitoring starts with the investigator driving
a probe into the ground either by using the Geoprobe or by using a "slam bar." Both of these approaches
tend to destroy the natural soil permeability around the body of the probe due to soil compaction
concurrent with the insertion. This is most evident in moist, heavy clay soils. Similarly, in very dry,
cemented soils, driven probes can create fractures within the soil body, thus enhancing soil permeability
to vapor concurrent with insertion. This can allow ambient air to mix with the contaminated soil
atmosphere, thus diluting the soil gas sample. These concerns are significant when using soil probes with
internal diameters greater than 3 inches. Historically, cluster wells of soil vapor probes at different
depths (see Section 3.1, Figure 3-3) are used for subsurface CH4 monitoring.
In an effort to minimize the number of sampling probes being inserted into the landfill, the use of a 1/4
inch sampling probe allows for the ability to extract a sample while minimizing the impact on the soil.
Once in position, a pre-evacuated whole-air canister can be attached, as illustrated in Figure A-9, or a
syringe sampling approach can be used as illustrated in Figure A-10. For semi-volatile monitoring,
Figure A-11 illustrates the application of a low-volume sampling approach using EPA Compendium
Method TO-10 involving PUF adsorbent sampling collocated with a whole-air canister for VOCs using
Compendium Method TO-15. Once again, the sample extracted from the subsurface is regulated by an
in-line flow controller along with an in-line sintered stainless steel filter to remove particles in the
sample gas. This approach has many advantages:
• No power required for the monitoring system,
• One-man operation, thus minimizing labor hours,
• Ease of sampling operation and sample transport, and
• Field portable, allowing many samplers to be deployed for obtaining representative samples.
RCRA Subpart C requires monitoring of subsurface CH4 concentrations at the landfill property boundary
and within onsite structures. Subpart C does not, however, specify the number of wells or their spacing.
This is determined on a site-specific basis.
Finally, the collection and concentration of soil gas contaminants can be greatly effected by the
components of the sampling system. It is imperative that one use materials that are inert to the COPCs
in the field investigation. Areas to which the investigator needs to pay close attention are:
• Sealing around the probe shaft at the entry point to minimize infiltration of ambient air, which can
be minimized by packing the shaft with hydrated bentonite or clay, as illustrated in Figure A-8;
• Using stainless steel for the probe, with the bottom third perforated;
• Minimizing the use of porous or synthetic materials (i.e., PTFE, rubber or most plastics), which can
retain sample or contribute cross-contamination;
• Purging the sample probe before attaching it to the collection system; however, purging the probe
prior to sampling under conditions of low soil permeability and low contaminant concentration may
actually lower contaminant levels below the analytical detection limits;
• Leak-checking the sampling system prior to sample collection to detect potential leaks and to
minimize soil gas dilution; a leak-tight seal at the sampling port and leak-tight fittings in the
sampling equipment helps minimize dilution of sample gas by air infiltration;
• Keeping all transfer lines short as possible to minimize trapping particulate matter and condensing
extracted landfill gas in the lines.
As illustrated in Figure A-9, soil gas sampling for CH4 and VOCs typically employs an evacuated,
specially-treated canister connected to a flow controller and subsequently connected to the sampling
probe. The sampling probe is first purged of at least two volumes of air using a special fitting and a
purge pump. Flow is then stopped for a given time period to allow the vapor concentration in the soil
pores to re-establish equilibrium conditions. Actual sampling then beings at a sampling rate low enough
to prevent ambient air from infiltrating the sample. For shallow soil gas sampling, air may flow down
the annulus of the probe and dilute the sample if the sampling rate is too high and the seal at the ground
surface is not air-tight. Once a sufficient sample volume has been extracted, the canister is shipped to
the laboratory for analysis. It should be stressed that soil gas concentrations may vary considerably over
relatively small distances given the heterogeneity of the soil. Therefore, a sufficient number of samples
at varying locations should be taken to establish a reasonable average value for each contaminant. If
sampling is used to estimate soil gas concentrations beneath a building floor, the sampling probes should
be inserted through holes drilled in the basement slab. Alternatively, the probe can be inserted at an
angle under the building from outside the footprint of the building floor in contact with the soil.
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Figure A-9. Application of EPA's Compendium Method TO-15 for VOCs at a MSW
Landfill.
Figure A-10. Application of Syringe Monitoring for VOCs at a MSW Landfill.
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Figure A-11. Application of Compendium Method TO-10A (Semi-volatiles, PCBs) and
Compendium Method TO-15 (Methane, NMOCs, VOCs) Sampling at a MSW Landfill.
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11.3 Vent Monitoring
Monitoring vent tubes from MSW landfills is very similar to monitoring ambient air or LFG combustion
equipment. In vent monitoring, the investigator needs to select low-volume sampling technologies so
that the samples will be representative of the actual emissions from the vent. Sampling can be performed
directly from the vent by inserting a probe into a small sampling port or directly down the vent. The
sample is then extracted into the sampling apparatus, similar to bore-hole monitoring illustrated in Figure
A-8.
If the flow of exhaust gas through the vent tube is very low, one can encapsulate the exhaust of the vent
tube to retain the sample. The sampling probe is therefore inserted into the encapsulated vent. This
sampling approach is illustrated in Figure A-12. This application illustrates employing Compendium
Method TO-10, a low volume approach for sampling and analysis of dioxins, furans, and PCBs from
the capped landfill. Figure A-13 illustrates sampling the exhaust of the landfill vent by employing
samplers upwind and downwind of the emission point. Once again, a low volume sampling approach
is used to capture the exhaust from the landfill vent.
11.4 Perimeter Air Monitoring
Many factors must be considered when developing a monitoring plan for the characterization of
emissions leaving a MSW landfill. Such factors as target COPCs, monitoring equipment and analytical
capability, cost, availability of utilities at perimeter site locations, etc. The first step in the development
of a perimeter air monitoring program is the design of a monitoring strategy. The monitoring strategy
helps determine the overall objectives of the monitoring program. In developing a monitoring strategy
to meet sampling program objectives, several crucial items should be considered:
• Processes and sources to be characterized,
• Any relevant rules or ARARs that require the monitoring program to be conducted, and any specific
regulatory requirements,
• The intended use of the monitoring data,
• A summary of DQOs and other QA concerns, and
• Any cost, physical, and time constraints.
Figure A-12. Encapsulated Vent Tube Sampling for PCBs Utilizing EPA Compendium
Method TO-10A. (Note Portable Monitor to the Right of the Vent Tube for Ambient
Monitoring of Emissions During Normal Vent Tube Emissions.)
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Figure A-13. Upwind/Downwind Sampling for PCBs from a Landfill Vent,
The following is a brief overview of some of the important aspects when implementing and developing
a perimeter air monitoring program at a MSW landfill.
11.4.1 Site Characteristics. One of the most important aspects to consider when evaluating site
characteristics is the site terrain. The geometry of the site and the contour of the location directly
influence the extent and the design of the perimeter air monitoring program. Extremely complex terrain
will complicate the migration of contaminants and make evaluation techniques complex with uncertain
results. Fixed-point monitors may not be as effective as the application of open-path optical remote
sensing devices because of the likelihood of the fixed-point monitors missing the "site plume." To
compensate, one can increase the number of fixed-point monitors as part of the perimeter air monitoring
program on both the horizontal and vertical plane in an attempt to characterize the site plume. Another
option is to use air dispersion modeling to map the site plume; however, air dispersion modeling is often
difficult to implement and results may be inaccurate and non-representative.
Local meteorological conditions will also play a major role in the design of a perimeter air monitoring
program. The placement of inlet extractive probes of a real-time or time-integrated monitoring systems
must be such that the gas sample analyzed is truly representative of the site emissions regardless of wind
direction. Historically, the evaluation of the 5-year wind rose (i.e., wind speed and direction
distributions) is used to help locate inlet probes in an upwind/downwind scenario based upon the
dominant wind direction. However, the uncertainty of the meteorological conditions at the site would
require, at a minimum, four inlet probes for real-time or time-integrated monitoring systems around the
site with the first system placed in the upwind quadrant based on the 5 -year wind rose and the remaining
systems at 90° around the site with reference to the upwind station. This placement allows appropriate
coverage at a reasonable cost.
Accessibility to sampling sites is also a consideration when designing the perimeter air monitoring
system. Under best conditions, the site will have an access road around the perimeter where the CH4
sampling probes are located for ease of maintenance and auditing. The access road saves time and labor
when performing inspection and audits of monitoring equipment. In addition, available utilities are
important for both real-time and time-integrated networks of samplers.
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11.4.2 Evaluation of Available Information. A substantial savings in sampling time and costs can be
realized by evaluating existing information. Although such information seldom satisfies the objectives
of the sampling program, it can provide valuable insight into what analytes to sample, when and where
sampling should be performed, and what sampling techniques are likely to be successful. For example,
data from a past sampling program at a similar site may indicate which compounds are likely to be
present and at what concentrations. Historical data from a nearby site might indicate the extent to which
background concentrations may contribute to the on-site concentration measurements. Additionally,
information may be available on contaminant phase distribution characteristics and monitoring
equipment performance. The time devoted to locating and reviewing information on past test programs
usually pays for itself in the development of a more efficient sampling strategy.
11.4.3 Meteorological Data. Ordinarily, the monitoring strategy will include collecting meteorological
data. An important reason for evaluating these data is to determine whether the atmospheric conditions
and pollutant concentrations have an impact on the surrounding community and are truly representative
of conditions at the site. For example, because the volatilization of toxic compounds from contaminated
soil is influenced by soil temperature and moisture, temperature and rainfall measurements may be
especially important to monitoring strategies where the volatilization of contaminants from the soil is
to be characterized. In this example, an effort would be made to conduct the monitoring program during
periods when temperatures and rainfall are within normal ranges for the locale under study. At a
minimum, the following meteorological parameters should be monitored on a continuous basis:
• Windspeed and direction,
• Temperature (at 10 m and 2 m heights),
• Relative humidity,
• Barometric pressure, and
• Precipitation.
Meteorological data are also important in determining where to site probes and monitoring equipment,
and in assuring that siting decisions remain appropriate throughout the test period. The usual strategy
for siting probes is to establish monitoring locations downwind of the source, with possibly one or two
locations upwind of the source for background measurements. The use of an on-site meteorological
station both before and during the sampling period will provide the information necessary to make
intelligent decisions about monitor siting.
11.4.4 Selection of Instrumentation and Analytical Methods. An obvious factor in the selection of
instrumentation and analytical sampling methods is the ability of the method to measure the compound
of interest at a specified concentration, typically in the parts per million by volume to parts per billion
by volume range for highly toxic compounds. The ability of a sampling method to measure low
concentrations will depend on several factors, including:
The sensitivity of the sampling method for the particular compound of interest,
Applicability of the method for monitoring all target analytes,
Ability of the instrumentation to collect, speciate and detect specific analytes,
Cost constraints,
Methodology performance and reliability,
The detection limits of the chosen instrumentation and analytical method, and
Ease of set-up and operation.
Other important factors to consider in the selection of sampling methods are: (1) the potential for artifact
formation, (2) the minimization of erroneous data due to interfering compounds, (3) the ability of the
method to achieve desired data quality objectives, (4) the ability to simultaneously measure other
compounds of interest, and (5) the compatibility of the sampling method with available analytical
methods. Questions that should be answered in the selection of instrumentation are:
• Can the selected instrument detect the probable target compounds?
• Does the sampling methodology sample the analyte effectively and quantitatively?
• Does the instrument transfer the analyte quantitatively from the inlet to the analytical detector?
• Can the instrumentation produce precise, accurate, and quantitative results for all of the analytes
listed in the monitoring program goals?
• Does the selected instrumentation have detection limits low enough to meet the overall objectives
of the sampling program?
• Would the methodology be hampered by any interfering compounds?
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Typically, standardized sampling methods or Federal Register methods should be utilized in a perimeter
air monitoring program. Table A-9 outlines recommended time-integrated sampling and analytical
methods for traditional COPCs found at MSW landfills in order to reach health-based detection limits.
Table A-9. Recommended Sampling and Analytical Methodologies for COPCs at MSW Landfills.
Pollutant Methodology Sampling Media
Methane/NMOC Compendium Method TO-12 Whole-air canister/FID
Real-time CH4 NMOC
Speciated VOCs Compendium Method TO-15 Specially -treated canister/GC/MS
or Ion Trap
Semi-volatiles, including Compendium Method TO-13 A Filter/PUF/GC/MS
dioxm/furans, PCBs, Pesticides
Paniculate Matter/Metals Compendium Method IO-1/IO-2 Filter/ICP/MS
Mercury Compendium Method IO-5 Adsorbent Tube/AES
Reduced Sulfur Compounds Compendium Method TO-15 Specially-treated canister/FPD
Freons Compendium Method TO-15 Specially-treated canister/GC/MS
or Ion Trap
11.4.5 Number and Location of Sampling Sites. A variety of factors influence the number and location
of sampling sites around a hazardous waste site. Factors that influence the required number and location
of sites are:
• Evaluation of the 5-year wind rose for predominant wind direction; location of potential on-site
emission sources (i.e., process emissions, waste handling facilities etc.);
• Location of topographic features that affect the dispersion and transport of site emissions;
• Location of sensitive receptors at the site perimeter and offsite;
• Location of offsite sources that might contribute to background concentrations; and
• The level of confidence needed to ensure that the maximum concentrations are obtained.
In determining the number and location of sampling sites, dispersion models (screening and refined)
should be used to assist in estimating ground-level concentrations in the site vicinity and to determine
locations of maximum concentrations for short-term (up to 24 hours) averages and long-term (monthly,
seasonal, and annual) averages. Inputs into the dispersion model should include landfill waste emissions,
representative meteorological data, populations close to the site, and sensitive populations. The model
outputs should be plotted as concentration isolpeths for each COPC.
This information will assist in siting the monitoring stations. The first priority, however, should be to
locate sampling sites that:
• Provide information on possible high impacts of the emission plume on sensitive receptors (i.e.,
concerned citizens, downwind communities, schools, hospitals, etc.) and
• Are positioned in the plume of expected high concentrations of source constituents based upon
historical meteorological data and dispersion modeling results.
Typically, programs designed for determining long-term concentration levels (e.g., annual or lifetime
exposures) will require fewer sampling locations than those intended to monitor compliance with short-
term action levels. The long-term prevailing wind directions are usually more predictable than day-to-
day wind patterns. Sampling sites, therefore, can be more accurately situated for measuring significant
long-term effects.
For determining concentration levels with respect to short-term effects, a fixed network of sampling sites
should ideally be located around the perimeter of the MSW landfill, with additional samplers located
near working areas and near sensitive receptors. The number of sampling sites will depend, in part, on
the size of the landfill site. For large sites surrounded by nearby residences, a 12-station network would
provide nearly complete spatial coverage at the fence line (i.e., one sampling station every 15 degrees),
as illustrated in Figure A-14. However, cost considerations may not allow for this arrangement. Another
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example would be to determine the predominant 5-year wind rose and place one monitoring station
upwind and three monitoring stations downwind. A better application of the four station arrangement
must be to locate a monitoring station at the centroid of each of the 90 degree quadrants of a circle based
upon the 5-year wind rose, as illustrated in Figure A-15.
Figure A-14. Example of a 12-Point Perimeter Air Monitoring Network at
a MSW Landfill site.
5-Year Predominant
Wind Direction
I nlet Probe
#1
Inlet Probe
#2
Inlet Probe
#4
Inlet Probe
#3
Figure A-15. Example of a 4-Point Monitoring Station Network at 90°
Locations Around the Perimeter of a MSW Landfill Site.
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Each of the stations illustrated in Figure A-15 serves specific objectives as part of the MSW landfill
perimeter air monitoring program:
• Station #1 is the predominant upwind site based upon the previous 5-year wind rose; this station
should identify specific constituents entering and impacting the site;
• Station #2 is the second station that provides data on the impact of emissions from the site;
• Station #3 is the predominant downwind site based upon the previous 5-year wind rose; it should
be approximately 180° from Station # 1; working with Station # 1, a predominant upwind/downwind
concentration of the emissions from the site can be instantaneously calculated; and
• Station #4 monitors the impact of emissions from the site.
After the number of stations has been determined, the placement of samplers must be considered. In
many cases, constraints on placing samplers can be encountered because of wind flow obstructions
caused by nearby buildings, trees, hills, or other obstacles. Other constraints might be related to security,
the accessibility of electrical power, and the proximity to roadways or other pollution sources that might
affect the representativeness of the sample. Specific guidelines for siting samplers for representative
conditions are given in Table A-10.
Table A-10. Example of Summary of Key Probe Siting Criteria for Perimeter Air Monitoring Programs
at MSW Landfills.
Factor
Criteria
Vertical spacing
Horizontal spacing
Unrestricted airflow
Spacing from roads
Representative of the ground breathing zone and avoiding effects of obstructions,
obstacles, and on-site traffic. Height of probe intake above ground in general:
2-3 m above ground and 2-15 m above ground in the case of nearby roadways.
1 m or more above the structure that supports the inlet probe.
Minimum horizontal separation from trees acting as an obstruction must be >10
m from the dripline.
Optimum horizontal separation from trees should be >20 m from the dripline.
Distance from probe inlet to an obstacle such as a building must be at least twice
the height the obstacle protrudes above the inlet probe.
If the inlet probe is located on a roof or other structures, there must be a minimum
of 2 m separation from walls, parapets, penthouses, etc.
There must be a sufficient separation between the inlet probe and a furnace or
incinerator flue. The separation distance depends on the height and the nature of
the emissions involved.
Unrestricted airflow must exist in an arc of at least 270° around the inlet probe,
and the predominant wind direction for the monitoring period must be included in
the 270° arc.
A sufficient separation must exist between the inlet probe and nearby on-site
roadways to avoid the effect of dust and vehicular emissions on the inlet.
Inlet probe should be placed at a distance of 5-25 m from the edge of the nearest
on-site roadway depending on the vertical placement of the probe inlet, which
could be 2-15 m above ground.
11.4.6 Cost Factors. A number of issues affect the cost of establishing and conducting a perimeter air
monitoring program at a MSW landfill:
• Objectives of the perimeter air monitoring program,
• Analytes to be monitored and the program required detection limits,
• Frequency and duration of the monitoring program,
• Accessibility for installation of the perimeter system, and
• Contingency monitoring.
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The objectives of the perimeter air monitoring program will most certainly be affected by costs. Whether
the program is established to monitor risk-based concentrations of COPCs, evaluate or document off-site
exposure for protection of the surrounding community, or monitor on-site workers as part of an
industrial hygiene program, overall costs are affected. The primary objectives will dictate the type of
sampling equipment and analytical requirements to meet the DQOs of the program. Even the level at
which emissions are to be monitored will affect cost. For example, if the alert level at the perimeter is
measured in terms of CH4 and NMOCs rather than speciated organics, then the analytical equipment is
less complicated, thus less costly. If, however, the purpose is to monitor individual COPCs at the risk
level of 1-in-l million, the analytical system must be far more sensitive, thus increasing the cost of the
perimeter air monitoring program substantially.
The number and type of analytes to be monitored will also affect the cost of the program. If the
requirements are to monitor on a real-time basis for a large group of speciated organics rather than
monitoring for CH4 and NMOCs, the program cost will increase. A larger analytical system will be
required to give a full chromatogram of the analytes to be monitored. On the other hand, if one is able
to select an appropriate subset of the compounds to be monitored and limit their number to less than five,
cost savings can be achieved.
The frequency of sample collection will have a significant cost effect on the perimeter air monitoring
program. Although real-time, on-site automated monitoring helps reduce the cost because analysis is on-
site, the implementation of concurrent quality assurance monitoring using time-integrated systems must
be taken into account, which brings into issue data turnaround and laboratory responsiveness as a factor
in the decision for the implementation of the time-integrated monitoring techniques. Moreover, capital
equipment, maintenance, and operational costs must be considered.
All of the above factors play an important role in establishing a real-time or time-integrated perimeter
air monitoring system at a MSW landfill. Figure A-16 illustrates a full complement of monitoring
systems located at the perimeter of a MSW landfill. Figure A-16 includes sampling techniques for VOCs
(center sampler with canister); for TSP (far-field sampler); and for dioxins, furans, semi-volatiles, and
PCBs (near-field sampler). Some sampling stations at the perimeter of the MSW landfill site can be as
simple as a VOC sampler at the property line or perimeter of the site, as illustrated in Figure A-17.
Figure A-16. Time-Integrated perimeter Air Monitoring System at a MSW Landfill.
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Figure A-17. Compendium Method TO-15A Application for
Monitoring VOCs at the perimeter of a MSW Landfill.
In summary, this appendix has provided the RPM and other stake holders with information associated
with the monitoring techniques and instrumentation needed to quantify landfill gas constituents. It has
also discussed the nature of landfill gas, the development of a landfill target compound list (TCL), and
technologies for monitoring landfill gas, including time-integrated and real-time techniques for
inorganics, organics, and suspended particulate matter (SPM). Additionally, this appendix has provided
guidance on the use and application of Federal Reference Methods (FRMs) and Compendia methods for
quantifying COPC concentrations found in landfill gas.
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12.0 References
Hashmonay, R.A., M.G. Yost, D.B. Harris, and E.L. Thompson. 1998. Simulation Study for Gaseous
Fluxes from an Area Source Using Computed Tomography and Optical Remote Sensing, SPIE, 3534:
405-410.
Hashmonay, R.A., and M.G. Yost. 1999. Innovative Approach for Estimating Fugitive Gaseous Fluxes
Using Computed Tomography and Remote Optical Sensing Techniques, J. Air Waste Manage. Assoc.,
49:966-972.
Hashmonay, R.A., M.G. Yost, and C. Wu. 1999. Computed Tomography of Air Pollutants Using Radial
Scanning Path-integrated Optical Remote Sensing, Atmos. Environ., 33:267-274.
Hashmonay, R.A., D.F. Natschke, K.Wagoner, D.B. Harris, E.L.Thompson, and M.G. Yost. 2001. Field
Evaluation of a Method for Estimating Gaseous Fluxes from Area Sources Using Open-path Fourier
Transform Infrared, Environ. Sci. Technol., 35:2309-2313.
Hashmonay, R.A., K. Wagoner, D.F. Natschke, D.B. Harris, and E.L. Thompson. 2002. Radial Com-
puted Tomography of Air Contaminants Using Optical Remote Sensing, presented at the AWMA 95th
Annual Conference and Exhibition, Baltimore, MD, June 23-27.
Winberry, Jr., W.T., N.T. Murphy, and B. Coronna. 1990. "Compendium of Methods for the Sampling
and Analysis of Indoor Air," EPA-600/4-90-010, U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, Research Triangle Park, NC 27711, April.
Winberry, Jr., W.T. 1999a. "Compendium of Methods for the Determination of Organic Compounds in
Ambient Air-Second Edition," EPA-625/R-96/010a, U.S. Environmental Protection Agency, Office of
Research and Development, Center for Environmental Research Information, Cincinnati, OH, June.
Winberry, Jr., W.T., S. Edgerton, and L. Forehand. 1999b. "Compendium of Methods for the Deter-
mination of Inorganic Compounds in Ambient Air," EPA-625/R-96-010a, U.S. Environmental
Protection Agency, Office of Research and Development, Center for Environmental Research
Information, Cincinnati, OH, June.
Winberry, Jr., W.T., T. Carson and R. Crume. 1997. "Design, Installation and Utilization of Fixed-
Fenceline Sample Collection and Monitoring Systems (FFMS)," EM-200-1-5, U.S. Army Corps of
Engineers, Center of Excellence, Omaha, NB, September.
Winberry, Jr., W.T. 1998. "Compendium of Methods for the Determination of Inorganic Compounds
in Ambient Air," Environmental Testing and Analysis, 7:2, March/April.
Winberry, Jr., W.T. 1998. "Compendium of Methods for the Determination of Organic Compounds in
Ambient Air-Second Edition," Environmental Testing and Analysis, 7:3, May/June.
Wu, C., M.G. Yost, R.A. Hashmonay, and DY. Park. 1999 Experimental Evaluation of a Radial Beam
Geometry for Mapping Air Pollutants Using Optical Remote Sensing and Computed Tomography,
Atmos. Environ., 33:4709-4716.
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Appendix B
Testing for Homogeneity Using
The Wilcoxon Rank Sum Test
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In order to properly characterize the emissions from a landfill and to determine how many and where
subsurface samples should be collected, it is necessary to identify those areas of the landfill that are
nearly homogeneous. This determination is performed by using the results of the surface screening
procedures. Through the application of statistical methods on these screening data it is possible to
determine if the landfill must be subdivided into near homogeneous areas. For the purpose of this
guidance it was decided to use the statistical method referred to as the Wilcoxon two-sample, rank-sum
test. The Wilcoxon Rank-Sum Test is a non-parametric procedure for comparing two independent
samples of sizes n\ and n2, after the samples are combined and the observations are ordered from
smallest to largest. Generally, non-parametric tests replace assumptions about normality with less
stringent assumptions, such as symmetry and continuity of distributions. This method is used to
determine if two independent sample populations are statistically similar (i.e., same mean and median).
For this application, statistically similar populations refer to areas within the landfill that have methane
or NMOC emission profiles that are nearly homogeneous.
B.1 Procedures
The Wilcoxon statistical procedure can be broken into a six step procedure.
Step 1 Define Hypothesis
The purpose of hypothesis testing is not to question the computed value of the sample statistic but to
make judgments about the difference between the sample statistic and a hypothesized population
parameter.
• Null hypothesis (Ho: xl is equal to x2) - There is no difference between the two populations, and
they have the same mean concentration.
• Alternative hypothesis (Ha: xl is not equal to x2) - There is a difference between the two populations
and they have different mean concentrations.
A level of significance (a) must also be established at this point for testing the hypothesis. There is no
single standard or universal level of significance fortesting ahypothesis. If the hypothesis is correct, the
significance level indicates the percentage of sample means that is outside the desired level of
confidence. The higher the significance level, the greater the probability of rejecting ahypothesis when
it is actually correct. Whether a null hypothesis is accepted or rejected depends largely on the chosen
level of significance. The significance level (also known as the alpha-level) of a statistical test is the pre-
selected probability of rejecting the null hypothesis when it is, in fact, true. Usually a small value such
as one percent or five percent is chosen. If the P value calculated for a statistical comparison is smaller
than the significance level, the null hypothesis is rejected. A five percent significance level has been used
in this guidance document.
Step 2 Tabulate Data and Assign Populations
To use the selected statistical methodology, the landfill surface screening data that was collected to
identify methane or NMOC hot spots must be assigned into two populations (e.g., east landfill and west
landfill). The following methodology and criteria is recommended:
N = nv + n2
Where:
N = Total population of concentration data,
nl = Population of size nl from area 1 of the landfill,
«2 = Population of size n2 from area 2 of the landfill,
nl < n2, and
«! > 4.
The available data should be listed in a sequential manner in terms of spatial relation between sampled
grid locations. The sample sets should have a spatial relationship that is continuous and inclusive. The
interface between populations sets n^ and n2 should have practical meaning. Figure B-l illustrates
acceptable and unacceptable population assignments. Since the goal is to determine if the landfill is a
homogeneous emitter, the initial effort is to subdivide the data into two populations of size n^ and n2 such
that the average concentration and the distribution ofthe emission datais approximately equal. Graphical
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contouring and mapping of the concentration data will allow one to quickly determine how to subdivide
the data. Absent graphical contouring, a trial and error method is used to assign the concentration data
to one or the other data sets.
N,
Acceptable if N,
-------
Step 5 Apply Decision Criteria
For small sample sets, the two populations can be considered statistically similar and, therefore, one
homogeneous area if Wa 20 and n^ >4). The appropriate
confidence interval for a given situation can be put into this worksheet. Several error messages are
embedded within this worksheet to assist in troubleshooting and ensure proper application of these
methods. This sheet will also indicate whether the two sample sets are considered homogenous by
comparing the calculated Z statistic to the ZK and Z]_a associated with the designated level of confidence.
Sheet 4: Step 2b - Check Results
This worksheet is used to check the results for small data sets (N<21). On this worksheet, an appropriate
confidence interval for a given situation can be selected from a drop down menu. This sheet will look
up the appropriate Wa and W^ values based on the values found in the Wilcoxon Rank Sum Table found
later in this workbook. Several error messages are embedded within this worksheet to assist in
troubleshooting and ensure proper application of these methods. This sheet will also indicate whether
the two sample sets are considered homogenous by comparing the calculated Wrs value with the Wa and
W^ values.
Sheet 5: Verify Locations
This sheet plots the input coordinate data for use in determining how to best divide the sample sets.
Sheet 6: Wilcoxon Rank-Sum Tables
This sheet contains the Wilcoxon Rank-Sum Tables. These tables are provided for information purposes
only and as a reference for extracting and comparing Wa and Wl_a values with Wrs when dealing with
small sample sets on Sheet 4.
B.3 Spreadsheet Access
The complete useable form of these spreadsheets can be found on the Environmental Quality
Management, Inc. web site, as Wilcoxon.xls. To access and download this file, go to
http://www.eqm.com/lfg/ (accessed August 2005). Then click on the link to download the file.
B-4
-------
EPA-600/R-05/123b
September 2005
GUIDANCE FOR EVALUATING
LANDFILL GAS EMISSIONS FROM
CLOSED OR ABANDONED
FACILITIES: Appendix C
by
Thomas Robertson and Josh Dunbar
Environmental Quality Management, Inc.
Cedar Terrace Office Park, Suite 250
3325 Durham-Chapel Hill Boulevard
Durham, North Carolina 27707-2646
EPA Contract No. 68-C-00-186, Task Order 3
EPA Project Officer: Susan A. Thorneloe
U.S. Environmental Protection Agency
Office of Research and Development
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
Research Triangle Park, North Carolina 27711
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
-------
Appendix C
Example
Generic Quality Assurance Project Plan
-------
EXAMPLE GENERIC
QUALITY ASSURANCE PROJECT PLAN
for the
APPLICATION OF GUIDANCE FOR EVALUATING
LANDFILL GAS EMISSIONS AT
CLOSED or ABANDONED SITES
EPA Contract No. 68-C-00-186
Task Order Number 3
EQ Project No. 030177.0003
Prepared for
Mrs. Susan Thorneloe
U.S. Environmental Protection Agency
Office of Research and Development
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
Research Triangle Park, North Carolina 27711
Submitted by
ENVIRONMENTAL QUALITY MANAGEMENT, INC.
Cedar Terrace Office Park, Suite 250
3325 Durham-Chapel Hill Boulevard
Durham, North Carolina 27707-2646
(919) 489-5299 FAX (919) 489-5552
Revision 0 - August 31, 2005
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QUALITY ASSURANCE PROJECT PLAN:
EVALUATING LANDFILL GAS EMISSIONS AT
CLOSED or ABANDONED SITES
EPA Contract No.
Work Assignment No:
EPA Remedial Project Manager:
Name Date
EPA WA Manager:
Name Date
EPA QA Officer:
Name Date
Contractor Project Manager:
Name Date
Contractor QA Officer:
Name Date
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Table of Contents
List of Appendices 2
List of Figures 3
List of Tables 3
List of Acronyms 4
Distribution List 5
A. Project Management 7
A-l Project Definition and Background 7
A-2 Project Organization 8
A-3 Project Task Descriptions 11
A-4 Quality Objectives and Criteria 22
A-5 Special Training/Certification 36
A-6 Documents and Records 37
B. Data Generation and Acquisition Elements 39
B-l Sampling Process Design 39
B-2 Sampling Methods 42
B-3 Sample Handling and Custody 43
B-4 Analytical Methods 49
B-5 Quality Control 55
B-6 Instrument/Equipment Testing, Inspection and Maintenance Requirements 59
B-7 Instrument Calibration and Frequency 62
B-8 Inspection/Acceptance Requirements for Supplies and Consumables 70
B-9 Indirect Measurements 70
B-10 Data Management 72
C. Assessment/Oversight 73
C-l Assessments and Response Actions 73
C-2 QA Reports to Management 80
D. Data Validation and Use 80
D-l Validation and Verification Methods 80
D-2 Reconciliation with User Requirements 85
Appendix
A. Site Specific QAPP - TBD A-l
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List of Figures
A-l Project Organization Chart 9
A-2 Flow Chart for Assessing Air Impact by Modeling 12
A-3 Flow Chart for Assessing Vapor Diffusion from Groundwater 13
A-4 Idealized Project Schedule 23
B-l Chain-of-Custody Form 45
B-2 Chain-of-Custody Report for Canister Samples 47
B-3 Example Nonconformance Report 61
C-l Field QA/QC Audit Outline 74
C-2 Laboratory QA/QC Audit General Considerations 75
C-3 Sample Corrective Action Report 77
C-4 Sample Field Change Request 79
D-l Data Package List 82
D-2 Data Package Document Inventory List 83
List of Tables
A-l Preliminary Target Analyte List 16
A-2 Summary of Data Collection Efforts 20
A-3 Air Pathway Action Levels 21
A-4 Field Sampling Summary for Each Site 29
A-5 Summary of Precision, Accuracy, and Detection Limits for VOC Analysis of Air
Samples, Low-Level Sample Technique 32
A-6 Summary of Precision, Accuracy, and Detection Limits for VOC Analysis of Air
Canister Samples, High-Level Sample Technique 33
A-7 Summary of Precision, Accuracy and Completeness Goals for Physical Properties 34
B-l Summary of Sampling and Analytical Approach 40
B-2 Targeted Instrument Conditions for Analysis of VOCs 51
B-3 Guidelines for Minimum QA/QC Samples for Field Sampling Programs 57
B-4 Routine Preventative Maintenance Procedures and Schedules for Field
Monitoring Equipment 62
B-5 Target Calibration Concentrations and Quantitation Ions for COPC 66
C-l QA Reports to Management 80
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List of Acronyms
Acronym Definition
ARARs applicable or relevant and appropriate requirements
ASTM American Society of Testing and Materials
CCV continuing calibration verifications
CERCLA Comprehensive Environmental Response, Compensation and Liability Act
CFR Code of Federal Regulations
CLU-IN Hazardous Waste Cleanup Information
COC chain of custody
COPCs contaminants of potential concern
DQA data quality assessment
DQOs data quality objectives
ELCT electrolytic conductivity detector
ERTC Environmental Response Team Center
FID flame ionization detector
FRM Federal reference method
GC/MS gas chromograph/mass spectrometer
IS internal Standard
LEL lower explosive limit
LFG landfill gas
LOI limit of identification
MDL method detection limit
MQL method quantitation limit
MRL method reporting limit
MS/MSD matrix spike/matrix spike duplicate
NIOSH National Institute for Occupational Safety and Health
NIST National Institute of Standards and Technology
NMOCs nonmethane organic compounds
NSCEP National Service Center for Environmental Publications
OSHA Occupational Safety and health Administration
OVA organic vapor analyzer
PE performance evaluation
PID photoionization detector
QAPP Quality Assurance Project Plan
QA/QC quality assurance/quality control
RDL reliable detection limit
RPD relative percent difference
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List of Acronyms (concluded)
Acronym Definition
RPM remediation project managers
RRT relative retention time
SARA Superfund Amendments and Reauthorization Act
SCS Soil Conservation Service
SOP standard operating procedure
TAL target analyte list
TCD thermal conductivity detector
THC total hydrocarbon concentration
TNR toluene-normalized response
TOM task order manager
UHP ultra high purity
VOCs volatile organic compounds
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Distribution List
EPA Remediation Project Manager
EPA Laboratory Manager
EPA WA Manager
EPA QA Manager
Contractor Project Manager
Contractor QA Officer
Contact task order manager to determine the date of the most recent version of this QAPP.
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ELEMENT A - PROJECT MANAGEMENT
A.I Project Definition and Background
EPA recently developed a draft guidance document to assist remediation project managers
(RPMs), risk assessors, and others in assessing human health and safety concerns associated with
landfill gas (LFG) emissions at closed or abandoned landfill sites. The Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA) and the Superfund Amendments and
Reauthorization Act (SARA) mandate the characterization of all contaminant migration pathways
from contaminated sites. At CERCLA landfills, characterization of the air pathway is often delayed
until the cover systems are designed. Recently there has been increased interest in the use of
alternative (i.e., permeable) cover systems that may not adequately control LFG. In these cases, it is
necessary to characterize the nature of the LFG emissions and the risks that would result from
exposure. To address these concerns, a guidance document entitled Guidance for Evaluating Landfill
Gas Emissions at Closed or Abandoned Sites has been developed. A fact sheet and the guidance is
available for viewing or downloading from EPA's Hazardous Waste Cleanup Information (CLU-IN)
Web site at http://cluin.org (accessed August 2005). Hard copies are available free of charge from:
U.S. EPA National Service Center for Environmental Publications (NSCEP)
P.O. Box 42419
Cincinnati, OH 45242-2419
Telephone: (513) 489-8190 or (800) 490-9198
Fax: (513)489-8695
The task order manager (TOM) and RPM will determine which sites are to be selected. It is
anticipated that existing information will indicate if LFG is being emitted from the landfill in an
uncontrolled manner, if there is a groundwater plume migrating offsite, if there are nearby offsite
structures, and if access to the site and nearly structures is assured.
The primary purpose of the project is to provide the RPMs with information that will allow them
to determine if LFG controls are needed and if compliance with applicable or relevant and appropriate
requirements (ARARs) have been achieved. Field work is a means to collect the information needed
to implement the procedures included in the guidance. Comparability of concentration data from site-
to-site is not anticipated. Still there needs to be a unifying level of acceptable uncertainty in order to
define measurement quality objectives. Data quality objectives are a starting point of an interactive
process, and they do not necessarily constitute definitive rules for accepting or rejecting results. The
measurement quality objectives have been defined in terms of standard methods with accuracy,
precision, and completeness. These objectives are believed to be achievable based on method
specifications, instrument capabilities, historic data, and experience.
The density of sample locations will be determined on a site-specific basis. It is anticipated that
the number of samples will be statistically robust, and the completeness goals recognize that the
guidance techniques can be evaluated without collecting a massive number of samples. The study
design is such that the impacts of the LFG emissions on the residence closest to the portion of the
landfill with the highest contaminant of potential concern (COPC) and methane (CH4) concentrations
are evaluated. Whether or not there are other offsite receptors that may be adversely affected by the
LFG emissions is not determined.
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This generic Quality Assurance Project Plan (QAPP) will be used as a guidance document for
preparing site-specific QAPPs. This QAPP will be applied to all activities involving environmental
measurements. This document includes sections that detail the procedures that will be used to sample
and analyze LFG. Preparation of this QAPP follow EPA requirements as stated in the document EPA
QA/R-5 Requirements for quality assurance project plans (March 2001).
A.2 Project Organization
The project organization chart is shown in Figure A-l. is the TOM. She/he is
responsible for coordinating activities and for obtaining the staff and resources needed to complete
this project. is the contractor project manager with primary responsibility for both
administrative and technical matters. This project is a collaborative effort between (organizations).
Close coordination between the project participants will be needed to ensure that the QAPP
requirements are understood and that all of the project objectives are met.
The TOM has overall responsibility for ensuring that the proj ect meets EPA obj ectives and quality
standards. The TOM is also responsible for defining the scope of work and deliverables required for
the delivery order. She/he will ensure that the performance of assigned tasks addresses the quality
assurance (QA), quality control (QC), and chain-of-custody (COC) procedures specified in this
QAPP. She/he is responsible for selecting the landfill sites and for coordinating activities at them. The
TOM must review and approve the QAPP.
The EPA QA manager will be responsible for reviewing and approving the generic and site-
specific QAPPs. The EPA QA manager may schedule audits at her/his discretion.
The site laboratory manager is responsible for directing all of the onsite activities including
obtaining equipment, supplies, and qualified personnel. He/she will assign duties to the site
monitoring and sampling team as required to complete the study effort in a cost-effective and timely
manner. The site laboratory manager is responsible for organizing and deploying competent field
crews. He/she will communicate regularly with the TOM and proj ect manager to ensure that progress
is achieved and that expenditures are controlled. The sampling and monitoring team will include
persons that have the training and experience needed to carry out the activities described in the
generic and site-specific QAPPs. The sampling and monitoring field team leader is responsible for
documenting compliance with the QAPP and standard operating procedures (SOPs). The field team
leader shall implement corrective actions as needed and he/she shall report any sampling or
monitoring issues that may affect data quality to the quality assurance officer. The site laboratory
manager must review and approve the QAPPs.
The contractor proj ect manager is responsible for preparing proj ect deliverables and for managing
the proj ect. She/he will ensure that the agreed project milestones budgets and schedules are achieved.
He/she will communicate regularly with the TOM, the Environmental Response Team Center (ERTC)
project manager, and the site-specific remedial project coordinators to ensure that the project and
QAPP is completed as planned. The project manager must approve the QAPPs.
-------
EPA Task Order Manager
EPA Environmental
Response Team Center
Project Manager
Site Sampling and
Monitoring Team
Volatile Organic
Analysis
Organic Laboratory
Manager
Physical Parameter
Analysis
Site Laboratory
Manager
EPA QA Manager
EPA Remeadiation
Project Site Manager
Health and
Safety Officer
Contractor
Project Manager
QA Officer
Chemist
Sampling and
Analytical
Specialist
Hydrogeologist
Data Reduction 8.
Info. Management
Specialist
Document/Record
Management
Figure A-1. project Organization Chart
o -
l-*5 K<
oo o
o> o
(Jl
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The RPM is responsible for providing background and historical information, site access, site
security, utilities, and health and safety training. The background information will include site plans,
topographic maps, historical sampling data, and so forth. The RPM is also responsible for defining
ARARs and acceptable risk ranges on a site-by-site basis. The RPM must approve the generic QAPP
and the site-specific QAPP applicable to his/her site.
The QA officer will remain independent of the day-to-day activities and will have direct access
to the corporate executive staff as needed to resolve any QA disputes. In these roles she/he will:
• Maintain QA/QC oversight;
• Prepare and review QAPPs and amendments;
• Review and provide audit reports;
• Initiate, review, and follow-up on corrective actions;
• Approve QAPPs and amendments; and
• Participate in project meetings as directed.
The QA officer shall be responsible for reviewing and approving the generic and site-specific
QAPP. The QA officer shall review the laboratory reports to determine if the methods and procedures
have been properly followed and documented. Discrepancies will, if feasible, be corrected, and
appropriate annotations will be recorded. Any variances that cannot be corrected will be flagged, and
the usefulness and limitation of the laboratory data will be ascertained. The QA officer will conduct
field audits in order to verify that QAPP and SOP requirements are being followed. The field audit
will be completed during the first two days of each site investigation. Corrective actions will be
initiated from the field in order to minimize adverse impacts. Audit items will include:
• Verification of field instrument calibration,
• Duplicate reading of direct read instruments at 5 percent of locations,
• Predefined precision, accuracy, and completeness objectives,
• Review of Log Books, and
• Verification of training.
The sampling and analytical specialist is an expert that can be accessed by the field team.
The document and record manager is responsible for preparation of all reports and for filing all
material in the appropriate project file.
The hydrogeologist is a subject area expert that will provide assistance in evaluating the soil
properties and the nature and extent of any groundwater contamination.
The data reduction and information management specialist will be responsible for entering the
field and laboratory results into a data management system. The system will allow the concentration
gradients to be calculated and graphed accordingly. The system will allow for statistical evaluation
and it will include flags and audit tails that will allow one to find the original information source.
The technical staff for this project are experienced employees who possess the degree of
specialization and technical competence required to effectively and efficiently perform the work
described herein. Each manager as shown on the organization chart is responsible for the qualification
and capabilities of the staff being selected and assigned to this project.
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A.3 Project Task Descriptions
The air pathway evaluation procedures contained in the draft guidance document encompass
estimates of emissions to the ambient air and subsequent air dispersion and inhalation exposures.
Figure A-2 is a flow chart for assessing air impacts by modeling. Emission estimation procedures use
the LandGEM model1 along with LFG sampling to estimate the uncontrolled release of toxic and
nontoxic LFG constituents to the ambient air. Ambient air dispersion is simulated using both
screening-level and refined models to estimate exposure point concentrations for both risk evaluation
purposes and for comparison with air pathway ARARs.2 In addition to an ambient air exposure
evaluation, subsurface vapor transport and intrusion into aboveground structures must also be
evaluated. Subsurface vapor intrusion into buildings can be caused by convective vapor transport (i.e.,
due to pressure gradients) and diffusive vapor transport from contaminated groundwater below the
structure. These exposure pathways are evaluated using a combination of modeling and sampling.
Figure A-3 is a flow chart for assessing the impacts from contaminated groundwater. The following
tasks will be completed during this project.
Task 1 - Preparation of QAPP
In cooperation with the TOM and the EPA site laboratory manager, the contractor will prepare
a QAPP that specifies the type of data to be collected at each of the sites being evaluated. Sites may
vary significantly in age, size, content, design, meteorology, topography, and so forth. Comparability
of concentration data from site-to-site is not anticipated. The TOM and the RPM will determine
which site is being evaluated. The QAPP will indicate (1) the specific data and information to be
collected at each site by EPA Regional personnel, (2) the field testing and sampling to be conducted
by the sampling and analysis team, and (3) the data and information to be collected and analyzed by
the contractor. A site-specific QAPP will specify the sampling and analytical procedures to be
employed as well as the QA and QC procedures to be used to ensure that the data obtained are of
sufficient quality and quantity for risk evaluation purposes. Each site-specific QAPP will act as a road
map for conducting site-specific data acquisition and site information retrieval.
Task 2 - Estimation of LFG Emissions
For each site, historical data will be collected on the size of the landfill, the amount and type of
waste deposited, and the waste deposition dates and frequencies. For sites that lack these data, the
volume of each landfill will be estimated based on the landfill dimensions; the total amount of waste
will be estimated based on a default value of the in situ waste density. Waste deposition frequencies
and distributions will also be approximated if historical data are lacking. From these data and the
distribution of wastes in the landfill or landfill cells, the LandGEM model will be employed to
estimate the time-dependent LFG emissions over a residential exposure duration of 30 years for risk
evaluation purposes and over the appropriate averaging time(s) for the purposes of comparison with
any air pathway ARARs. The emissions of individual toxic components of the LFG will also be
landfill Gas Emission Model, Version 3.01. U.S. EPA Control Technology Center,
EPA-600/R-05/047. Available at http://www.epa.gov/ttn/catc/dirl/landgem-v302-guide.pdf
(accessed August 2005).
2Guidance for Evaluating Landfill Gas Emission at Closed or Abandoned Facilities,
EPA-600/R-05/123a.
-------
c
Start
fc
>
Grid Sample
PIDandFID
Sample All
Passive Vents
with PID and FID
C
End Ambient Air
Analysis
YES—
Use LandGem Model
and 90th Percentile
Cones, to Estimate
Emissions by Stratum
and/or Vent
Determine COPC
90th Percentile Cones.
for Each Stratum
and/or Vent
Construct
Detailed LFG
Sampling Plan
Perform Max.
Cone.
Screening-Level
Analysis
Option 1
If
o
(Ji
Subdivide Site into
Strata of Similar
COPC Cone.
Variability
Option2
Use Options
in Appendix
Cind Ambient Air
Analysis
Use ISC3 Dispersion
Model to Estimate
Normalized Air Cones.
by Stratum and/or
Vent at Receptor(s)
Use Normalized Air
Cones, and Actual
Emissions to Estimate
Actual Air Cones.
Figure A-2. Flow Chart for Assessing Air Impacts by Modeling.
-------
.YES^
Contaminate
Groundwater Below
Building(s) or Future
and-use Sites?
Collect/Estimate
Groundwater
Cones. Below
Receptor Site(s)
Perform Risk
Calculations
Estimate Indoor
Air Cones. Using
EPA Soil Vapor
Intrusion Model
Perform Soil
Gas
Sampling at
Receptor Site(s)
Use Existing Data
to Determine Soil
Stratigraphy and
Properties at
Receptor Site(s)
End Vapor Intrusion
from Groundwater
Analysis
Use Soil Borings to
Determine Soil
Stratigraphy and
Properties at
Receptor Site(s)
Estimate Indoor
Air Cones. Using
EPA Groundwater
Vapor Intrusion
Model
- SCS soil classes
- Soil dry bulk densities
- Soil water-filled porosities
- Soil organic carbon contents
Option 1
—YES—
Option 2
•YES->
Perform
Indoor Air
Sampling
•YES>
STOP
End Groundwater
Vapor Intrusion
Analysis
Figure A-3. p|OW chart for Assessing Vapor Intrusion from Contaminated Groundwater.
if
£8°
tji
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Page 14 of 86
estimated using the LandGEM model. This requires an average LFG concentration of each con-
stituent. These concentrations will be measured using LFG sampling techniques.
If the landfill employs uncontrolled vents, each vent will be sampled separately. If vents are not
employed or if the area of influence for the vents is not adequate, site LFG concentrations will be
delineated using a superimposed grid system. The number of sampling points will be determined as
a function of the landfill size, homogeneity of its contents, and the amount of resources available for
sampling and analysis activities. Soil gas sampling will be conducted approximately one meter below
any landfill cover using either a slam-bar sampling device or a Geoprobe sampling rig depending on
equipment availability and soil properties. It is assumed that ERTC will provide all sampling
equipment required. Screening level sampling will be performed using portable instruments that
respond to either methane and non-methane organic compounds (NMOCs). EPA Method 25A will
be used to determine total hydrocarbon concentration (THC). The NMOC concentration will be
determined by placing a charcoal trap between the sample location and the instrument. From these
data, the relative NMOC concentrations will be determined by the difference between the total organic
concentrations with and without methane. Once the NMOC concentrations have been determined, the
areal extent of the site will be partitioned statistically into contiguous areas of near homogeneous
NMOC concentration.
The number of samples that must be obtained to estimate the mean concentration of an area is
strongly dependent on the heterogeneity of the chemical distribution. Thus, for an area with uniform
distribution, few samples are needed to provide good characterization. Conversely, an area with
widely variable distribution would require a great number of samples. For areas with nonuniform
distribution such as a landfill, the total number of samples can be reduced by subdividing the area into
zones with similar levels of contamination and variability. The objective of screening is to identify
the areas with near homogeneous NMOC concentration; the Wilcoxon rank sum test (also known as
Mann-Whitney test) will be used to determine if there is an area with a higher mean concentration
when compared to the entire landfill.
The Wilcoxon rank sum test may be used to test for a shift in location between two independent
populations (i.e., the measurements from one population tend to be consistently larger than those from
the other population). This statistical procedure does not require normal distribution. The method is
not adversely affected by no detect values, and an equal number of samples is not required.
The Wilcoxon rank sum test procedure is as follows.
H0: Populations from which the two data sets have been drawn have the same mean.
HA: The population have different means.
For this project, a significance level (a) has been set to 5 percent.
1. Consider all m = nl+ n2 data as one set. Rank the m data from 1 to m; that is, assign the rank
1 to the smallest datum, the rank 2 to the next largest datum,..., and the rank m to the largest
datum. If several data have the same value, assign them the mi drank, that is, the average of the
ranks that would otherwise be assigned to those data.
2. Sum the ranks assigned to the n^ measurements from population one; denote this sum by Wrs.
3. If «j < 10 and n2 < 10, the test ofH0 may be made by referring Wrs to the appropriate critical
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value in Table X in Christensen (1977)3 page A-14.
4. If «j > 10 and n2 > 10 and no ties are present, compute the large sample statistic
Wrs - nl(
m+
1/2
5. If «j > 10 and n2 > 10 and ties are present, compute
12
z ',
m+ 1-
1/2
where7 is the number of tied groups and tj is the number of tied data in they'th group.
6. For a one-tailed a level test of H0 versus the HA that the measurements from population one
tend to exceed those from population two, reject H0 and accept HA if Zrs > Zj.a.
7. For a one-tailed a level test of H0 versus the HA that the measurements from population two
tend to exceed those from population one, reject H0 and accept HA if Zrs < - Z^.
This procedure will be repeated until the landfill has been divided in zones or areas of near
homogeneity. This partitioning will be subsequently used to determine sampling patterns for the
second round of sampling.
Each area with a near homogenous NMOC concentration as determined by the screening level
results will be sampled, using a slam-bar or Geoprobe for subsurface sampling and stack sampling
equipment for vents. LFG samples will be collected in Summa or equivalent canisters. An on-site gas
chromatography/mass spectrometer (GC/MS) will be provided by the ERTC for sample analysis. EPA
Method TO-15, "Determination of Volatile Organic Compounds" will be used for analyzing the
cannister contents. The target analytes for all sites are listed in Table A-l. This list may be expanded
on a site-specific basis if other chemicals of potential concern are identified by the RPM. In addition,
duplicate samples in canisters will be sent to the ERTC offsite laboratory for analyses. The duplicate
sample concentrations will be compared with the on site GC/MS results to estimate any potential
sample bias. This is important because on-site GC/MS analysis is not anticipated to be a commonly
available analytical option for future users of the guidance, and it provides a QC check of the methods
being used. Sample concentrations will be subsequently corrected for air infiltration according to the
procedures specified on page 2-8 in the draft guidance document.
3Christensen, Howard, 1977. Statistics - Step by Step, Houghton Mifflin Company,
Boston.
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Table A-1. Preliminary Target Analyte List
Classification
Very Volatile Organic
Speciated Volatile Organic Compounds
Analyte
Methane
Nonmethane Organic Compounds (NMOCs)
1,1,1-Trichloroethane (Methyl Chloroform)
1,1-Dichloroethene (Vinylidene Chloride)
1,2-Dichloroethane (Ethylene Bichloride)
Acrylonitrile
Benzene
Carbon Tetrachloride
Chlorobenzene
Chloroethane (Ethyl Chloride)
Chlorofluorocarbons (as
Dichlorodifluoromethane)
Chloroform
Dichlorobenzene (Meta- and Para-isomers)
Ethylene Dibromide
Dichloromethane (Methylene Chloride)
Perchloroethylene (Tertrachloroethylene)
Toluene
Trichloroethylene (Trichloroethene)
Vinyl Chloride
Xylenes (all isomers)
Estimated LFG
Concentration
(ppmv)
500,000
4,000
4
15
32
28
93
0.25
10
7
56
2
0.33
0.001
46
15
380
8
20
80
With the area-dependent mean concentrations of LFG constituents, the mass emissions of each
constituent for each near homogeneous area will be estimated using the LandGEM model based
on steady-state constituent concentrations. The LandGEM model will be run for a period of 30
years (and for ARAR-specific averaging times) for each area. The time-dependent emissions of
each LFG constituent will then be determined as the product of the yearly LFG emissions
predicted by the LandGEM model and the constituent mass fraction. The time-averaged emissions
of each constituent from each area will then be calculated using a trapezoidal approximation of the
integral over the exposure duration as specified on Page 2-13 of the draft guidance document.
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Task 3 - Estimation of Ambient Air Concentrations
Time-averaged ambient air concentrations of each constituent will be approximated using the
SCREENS dispersion model4 as specified in the draft guidance document. A risk evaluation will
then be performed for each constituent based on default residential inhalation exposure
assumptions at the point of maximum plume impact. Residential exposure assumptions are defined
for the inhalation/pathway by the following equations and assumptions:
CRmh(l} = ADI x CSFmh(i}
_ Ca x IR x ET x EF x ED x O.OOlmg / pg
BW x AT x 365 days I yr
URF xBWx
where
ADI = Average daily intake of chemical /',
CSFinh(i) = Chemical specific inhalation cancer slope factor,
URFj = Chemical specific inhalation unit risk factor,
Ca = Total air concentration of COPC /',
IR = Inhalation rate of 0.63 m3/h adults; 0.3 m3/h children,
ET = Exposure time, 24 h/day,
EF = Exposure frequency = 350 days/yr,
ED = Exposure duration; 30 yr-adult, 6 year child,
BW = Body weight 70 kg adult, 15 kb/ child, and
AT = Averaging time 70 yr.
As required, a comparison of estimated ambient air concentrations with the appropriate air
pathway ARARs will also be made. Estimated average exposure point concentrations and resulting
inhalation risks will be compared with the acceptable risk range and also compared with any
regulatory standards as specified in the site-specific air pathway ARARs. The RPM is responsible for
establishing the acceptable risk range, regulatory standards, and ARARs on a site-specific basis.
Determination of ARARs and risk ranges are site-specific determinations that are beyond the scope
of this example generic QAPP. The guidance presents procedures and techniques for estimating
ambient air and indoor air concentrations that can be compared to the applicable regulatory and health
standard. If the results of the SCREENS dispersion modeling indicate that the exposure point air
concentrations are clearly not a problem, the ambient air risk and ARAR evaluations can be
4SCREEN3 Screening Procedure for Estimating Air Quality Impacts of Stationary
Sources Revised EPA 450/R-92-019.
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considered accomplished. If the screening level comparison indicates there is a potential problem,
dispersion modeling will be continued using the refined ISC3 model. The refined model uses site-
specific information (location, geometry, meteorological, etc.) to estimate the ambient air concen-
tration at the selected receptor locations. If refined dispersion modeling indicates that the exposure
point concentrations still represent a potential health risk or that air pathway ARARs may be
exceeded, ambient air sampling may be considered at the discretion of the TOM. Such ambient air
sampling would consist of a series of stationary Summa canisters.
Task 4 - Estimation of Indoor Air Concentrations Due to LFG Transport
At each selected site, pre-existing LFG monitoring data (e.g., pressure, COPC concentration, CH4
concentration, NMOC concentration, flowrate, etc.) will be obtained. This information will be used
to estimate the subsurface methane and LFG COPC concentrations at selected landfill boundary
points. If these data are lacking and if approved by the TOM, cluster wells will be drilled to determine
subsurface methane and COPC concentrations. If required, drilling, equipment, and personnel to
install the cluster wells will be supplied by the RPM. LFG constituent concentrations (e.g., methane,
NMOCs, COPCs) will be determined for each soil stratum between the ground surface and the depth
of the landfill in proximity to the landfill boundary closest to an offsite structure. If any subsurface
methane concentration is greater than the lower explosive limit (LEL) at the site boundary,
preliminary vapor transport and intrusion modeling will be performed for methane and COPCs using
the Little et al. (1992)5 steady-state model as specified in the guidance. This involves estimates of the
subsurface pressure at the landfill boundary and the soil vapor permeability. If data are available for
in situ soil saturated hydraulic conductivity, the soil vapor permeability will be estimated based on
this value. If saturated hydraulic conductivity data are lacking, the soil vapor permeability will be
estimated based on the Soil Conservation Service (SCS) soil textural classifications. This involves
taking subsurface soil samples and analyses of soil particle size distributions through an American
Society for Testing and Materials (ASTM) standard method (ASTM methods D2216, D1587, D854,
and D422). Subsurface pressure at the landfill boundary must be empirically determined for the most
permeable soil strata between the landfill boundary and the offsite structure(s) of interest. If sub-
surface monitoring wells are available, pressure will be measured using the procedures specified in
40 CFR 60, Appendix A, Method 2E. In addition to vapor transport and intrusion modeling, portable
photoionization detection (PID) instruments will be used to detect any methane in preferential
subsurface convection pathways or conduits (e.g., water meters, utility lines, etc.) as well as within
and under any potentially affected offsite structure(s).
If preliminary modeling or sampling indicates potential indoor air methane concentrations greater
than 25 percent of the LEL, or COPC concentrations that represent unacceptable risks, soil gas
sampling below or adj acent to potentially affected buildings or indoor air sampling will be considered
at the direction of the TOM. If soil gas sampling is used, further modeling6 will be employed to better
estimate indoor air concentrations based on soil gas sampling results. If indoor air sampling is used,
5Little, J.C., J.M. Daisey, and W.W. Nazaroff 1992. "Transport of subsurface
contaminants into buildings" Environ. Sci. TechnoL, 26(11):2058-2066.
6Users Guide for Johnson and Ettinger Model for Subsurface Vapor Intrusion into
Buildings, EPA-OERR, June 2003.
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Page 19 of 86
other sources of the COPCs must also be accounted for including outdoor air and anthropo- genie
sources inside the structure of interest such as off-gassing of household chemicals and building
products.
Task 5 - Estimation of Indoor Air Concentrations Due to Vapor Intrusion from Contaminated
Groundwater
Existing site data will be reviewed to determine if groundwater contaminated by landfill waste has
migrated off site under houses or other structures. If so, COPC concentrations within the contam-
inated groundwater will be estimated from existing site data as a function of downgradient location
and distance. These data will be provided by the RPM. These data will then be used by the contractor
to estimate, through modeling, the potential indoor air concentrations of COPCs due to vapor
transport and intrusion into offsite structures. The screening-level models described in the draft
guidance document will be used to predict indoor air concentrations. Use of these models requires
data on subsurface soils directly below potentially affected structures. These data include soil dry bulk
density, moisture content, and vapor permeability (top soil stratum only). If data are lacking,
continuous soil cores would be taken from the soil surface to the top of the water table at locations
adjacent to the structure(s). Enough cores must be obtained to allow for a reasonably accurate
estimate of average values below the structures. It is assumed that all equipment required to obtain
these soil samples will be provided by the RPM. If the subsequent risk evaluation indicates possible
adverse health effects, soil gas or indoor air sampling would be performed at the direction of the TOM
to verify predicted indoor air concentrations.
Task 6 - Preparation of Work Assignment Report
At the conclusion of the field investigation part of the work assignment, the contractor will
prepare a written report summarizing the results of the field investigations, present a series of lessons
learned, and provide recommendations to be used in revising the draft guidance document and draft
fact sheet previously prepared under a separate EPA contract and work assignment. Revisions will
be suggested based on the results of applying the draft guidance document procedures at the test
landfill sites. Upon approval of the written report by the TOM, the contractor will revise the draft
guidance document and fact sheet and prepare three case studies for use in the draft guidance
document based on the three test sites. These documents will then be submitted to the TOM for
review. Upon receipt of all final comments from the TOM on the revised guidance document and fact
sheet, the contractor will prepare and submit to the TOM final versions of both documents.
This QAPP describes a sampling, analysis, and monitoring program designed to estimate the
emissions of hazardous and toxic compounds that exist in the LFGs at each site. A general overview
of the data collection effort is provided in Table A-2.
Determination of conformance with the National Contingency Plan (NCP), 40 CFRPart 300, or
compliance with any non air pathway ARARs, permit conditions, or Federal, state, or local regula-
tions and statutes is beyond the scope and intent of this example generic QAPP. The sampling and
analytical procedures described herein are designed to evaluate the significance of the emissions from
the landfill. Action levels for the air pathway are site specific. The site-specific QAPP will include
the information needed to complete Table A-3.
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Table A-2. Summary of Data Collection Efforts.
Site Background Information
1. Administrative contact, address, and telephone number
2. Maps (topographic, site plan, proximity, soil, groundwater, basement, wetland, etc.)
3. Landfill cross section and areal dimensions
4. Cover design basis (engineering specifications and design parameters)
5. LFG collection and treatment system design basis
6. Description and quantification of landfill contents and COPCs
7. Operational history (annual acceptance rates, years of operation, fill plan, etc.)
8. Extent and nature of groundwater contamination
Sampling, Monitoring, and Analytical Componentsa
S Methane and NMOC via portable flame ionization detectors (FID) on a 30-meter grid and at all
vents and on-site structures
S CO2, CH4, N2, and O2 via Method 3 C at 20 locations with highest NMOC concentration
S Site-specific COPC Tedlar bags or Summa canisters and mobile GC/MS (Laboratory-SOP 2102
or 1819) at locations with highest NMOC concentrations for each near homogeneous area (not to
exceed 20)
S If needed, LFG gas flow rate via five equal volume wells spread over the landfill using Federal
Reference Method 2E
S Soil properties (% moisture, bulk density, particle density, particle size) at locations with the
highest NMOC soil gas concentration using Laboratory-SOP 2012 and ASTM methods D2216,
D1587, D854, and D422 standard for each near homogeneous area
S In situ LFG pressure at up to 10 locations with 30-meter spacing along the landfill boundary
closest to any off-site structures
S Site-specific volatile organic target analyte list via Tedlar bags or Summa cannister and mobile
GC/MS (Laboratory-SOP 2102 or 1819) at up to 10 landfill boundary locations having the
highest NMOC soil gas concentration
S If needed, in situ hydraulic conductivity of permeable soil horizons via standard constant head
(D2434) methods at up to 10 boundary locations
S If needed, site-specific COPCs via Tedlar bag or Summa canisters and mobile GC/MS
(Laboratory-SOP 2102 or 1819) at up to three locations between the landfill boundary having the
highest NMOC soil gas concentration and the nearest off-site structure
S If needed, indoor air for site-specific COPCs via Tedlar Bag or Summa Cannister and mobile
GC/MS (Laboratory-SOP 1819) at the off-site structure closest to the boundary location having
the highest NMOC soil gas concentration
S If needed, up to three ambient outdoor air samples for site specific COPCs via Summa cannister
and mobile GC/MS (Laboratory-SOP 1819) at the off-site laboratory
S If needed, soil properties (% moisture, bulk density, particle density, and particle size) at up to
three potentially affected off-site structures using standard laboratory methods (ASTM Methods -
D2216, D1587, D854, and D422)
S If needed, up to three groundwater samples for the site-specific COPCs via 40-ml volatile organic
analysis (VGA) vials and GC/MS (SW846-8260) at potentially affected off-site structures located
over the top of the groundwater plume
Site-specific QAPP will identify when the "if needed" samples are to be collected.
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Table A-3. Air Pathway Action Levels.
Chemical of Potential
Concern
1,1,1 -Trichloroethane
1 , 1 -Dichloroethene
1 ,2-Dichloroethane
Acrylonitrile
Benzene
Carbon Tetrachloride
Chlorobenzene
Chloroethane
Chlorofluorocarbons (as
Dichlorodiflur-methane)
Chloroform
(Trichloromethane)
1 ,2-Dichlorobenzene
Ethylene Dibromide
Hydrogen Sulfide
Methylene Chloride
Tetrachloroethylene
Toluene
Trichloroethylene
Vinyl Chloride
Xylene (P)
Xylene (M)
Xylene (O)
Methane
Mercury
Limits of
Explosivity,"
%
1.8-14
6.5-15.5
6.2-16
3-17
1.2-7.8
NA
1.3-9.6
3.0-15.4
NA
NA
2.2-9.2
NA
4-44
13-23
NA
1.1-7.1
8-10.5
3.6-33
1.1-7.0
1.1-7.0
0.9-6.7
5.4-15
NA
Non-carcinogenic
Reference
Concentration,15
Hg/m3
1 x 103
3.2 x 101
1 x 1Q1
2.0 x 10°
6 x 101
2.5 x 10°
2.0 x 101
1 x IQ4
2x 102
3.5 x 1Q1
2.0 x 102
2 x 1Q-1
ND
3 x IQ3
3.5 x 1Q1
4.0 x 102
2.1 x 1Q1
1.0 x 102
7x 103
7 x 103
7 x 103
ND
3 x 1Q-1
Carcinogenic
Inhalation Unit
Risk Factor,b
(^ig/m3)1
NAC
5 x IQ-5
2.6 x IQ-5
6.8 x IQ-5
7.8 x IQ-6
1.5 x IQ-5
NDd
ND
ND
2.3 x IQ-5
ND
2.2 x IQ-4
ND
4.7 x IQ-7
5.8 x IQ-7
ND
1.7 x IQ-6
4.4 x IQ-6
ND
ND
ND
ND
ND
State/local
Ambient Air
Toxics
Standard,
Hg/m3
a Pocket Guide to Chemical Hazards USDHHS-CDC-1998
b Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities, July 1998.
c NA - Not applicable
dND-Nodata
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Page 22 of 86
Site-specific QAPPs will include a listing of the methods, procedures, and protocols. The O&M
manuals, field related SOPs for sampling and analysis, Health and Safety Plan, and QAPP will be
available for the field team to use and reference during onsite activities. The site laboratory manager
is responsible for assuring that the appropriate documents are available. The site-specific QAPP
components will be submitted to the TOM at least 30 days prior to the beginning of any data
generating activity at the site. The QA requirements are described in EPA QAR-5, "Requirement for
Quality Assurance Proj ect Plans." The contractor anticipates that the TOM and EPA Q/A officer will
review and approve any substantive changes in the QAPP.
Figure A-4 presents an example of an idealized project schedule. Site-specific schedules will be
developed at least 30 days prior to initiating any field activities on a site-by-site basis.
Project and quality record requirements may include:
• Site-specific QAPP,
• Audit reports,
• Status reports,
• Corrective action reports,
• Data review and data validation reports, and
• Project data records .
A.4 Quality Objectives and Criteria
Data quality obj ectives (DQOs) are qualitative and quantitative statements developed using EPA's
DQO process (QA/G-4 Guidance for DQO Process). The statements clarify the project's objectives,
define the appropriate types of data, and specify tolerable levels of potential decision errors. These
end use requirements form the basis for establishing the quality and quantity requirements of the data
being generated. DQOs define the performance criteria that must be met in order to limit the
probability of making unacceptable decision errors.
DQOs are quantitative and qualitative statements that are designed to:
• Clarify study objectives,
• Define type of data,
• Establish most appropriate conditions from which to collect data, and
• Specify acceptable levels of decision error that will be used as the basis for establishing the
quantity and quality of the data needed to support the outcome decisions.
For this proj ect the qualitative obj ectives are to evaluate the kinds and amounts of emissions from
selected landfill and to determine whether the draft guidance allows the users to determine if LFG
controls are needed. This generic QAPP and the site-specific QAPP result from the systematic
planning process and contain information needed to carry out the data gathering and meet the DQOs.
No criteria are currently in place to decide which types or how many data gaps or procedural problems
will trigger a revision or even abandonment of the draft guidance. Combined with the likely
variability of emissions and the proximity to off site structures, the threshold of what will qualify as
significant will probably be when it is determined that the procedures are to costly or that the guidance
user is unable to reach an acceptable end point for one of the three sites being evaluated. Based on
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Task Name
Taskl
Draft QAPP
EPA Review of Draft QAPP
Final QAPP
Site Selection and Coordination
Site-Spec! fie QAPP
Task 2
Sitel Field Work
Site 1 Data Analysis
Site 1 Case Study
Site 2 Field Work
Site 3 Field Work
Site 2 Data Analysis
Site 3 Data Analysis
Site 2 Case Study
Site 3 Case Study
EPA Review of Case Studies
Task 3
Revise Draft Guidance
Revise Draft Fact Sheet
EPA Review Drafts
Final Guidance
Final Fact Sheet
Duration
154 days
22 days
68 days
30 days
20 days
1 5 days
93 Days
1 0 days
25 days
13 days
1 0 days
1 0 days
25 days
25 days
8 days
8 days
20 days
30 Days
1 0 days
1 0 days
10 days
10 days
1 0 days
Start
Mon 7/23/01
Mon 7/23/01
Wed 8/22/01
Fri 11/30/01
Wed 1/23/02
Wed 2/1 3/02
Mon 4/8/02
Mon 4/8/02
Mon 4/22/02
Tue 5/28/02
Mon 4/29/02
Mon 5/20/02
Mon 5/13/02
Tue 6/4/02
Tue 6/1 8/02
Wed 7/1 0/02
Mon 7/22/02
Mon 8/19/02
Mon 8/19/02
Mon 8/19/02
Tue 9/3/02
Tue 9/1 7/02
Tue 9/1 7/02
Rnish
Wed 3/6/02
Tue 8/21/01
Thu 11/29/01
Tue 1/29/02
Wed 2/20/02
Wed 3/6/02
Fri 8/1 6/02
Fri 4/19/02
Fri 5/24/02
Thu 6/13/02
Fri 5/10/02
Mon 6/3/02
Mon 6/17/02
Tue 7/9/02
Thu 6/27/02
Fri 7/19/02
Fri 8/16/02
Mon 9/30/02
Fri 8/30/02
Fri 8/30/02
Mon 9/1 6/02
Mon 9/30/02
Mon 9/30/02
August
7/15 7/22 7/29 8/5 8/12 8/19 8/28
September
9/2 1 9/7 1 9/16 1 9/23
October
9/30 1 10/7
^~~~.'."
Project: Application of Guidance
For Evaluating Landfill Gas Emissions at Superfund Sites
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Task Name
Taskl
Draft QAPP
EPA Review of Draft QAPP
Final QAPP
Site Selection and Coordination
Site-Spec! fie QAPP
Task 2
Sitel Field Work
Site 1 Data Analysis
Site 1 Case Study
Site 2 Field Work
Site 3 Field Work
Site 2 Data Analysis
Site 3 Data Analysis
Site 2 Case Study
Site 3 Case Study
EPA Review of Case Studies
Task3
Revise Draft Guidance
Revise Draft Fact Sheet
EPA Review Drafts
Final Guidance
Final Fact Sheet
Duration
154 days
22 days
68 days
30 days
20 days
1 5 days
93 Days
1 0 days
25 days
13 days
1 0 days
1 0 days
25 days
25 days
8 days
8 days
20 days
30 Days
1 0 days
1 0 days
10 days
10 days
1 0 days
Start
Mon 7/23/01
Mon 7/23/01
Wed 8/22/01
Fri 11/30/01
Wed 1/23/02
Wed 2/1 3/02
Mon 4/8/02
Mon 4/8/02
Mon 4/22/02
Tue 5/28/02
Mon 4/29/02
Mon 5/20/02
Mon 5/13/02
Tue 6/4/02
Tue 6/1 8/02
Wed 7/1 0/02
Mon 7/22/02
Mon 8/19/02
Mon 8/19/02
Mon 8/19/02
Tue 9/3/02
Tue 9/1 7/02
Tue 9/1 7/02
Finish
Wed 3/6/02
Tue 8/21/01
Thu 11/29/01
Tue 1/29/02
Wed 2/20/02
Wed 3/6/02
Fri 8/1 6/02
Fri 4/19/02
Fri 5/24/02
Thu 6/13/02
Fri 5/10/02
Mon 6/3/02
Mon 6/17/02
Tue 7/9/02
Thu 6/27/02
Fri 7/19/02
Fri 8/16/02
Mon 9/30/02
Fri 8/30/02
Fri 8/30/02
Mon 9/1 6/02
Mon 9/30/02
Mon 9/30/02
{November
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December
12/2 1 12/9 1 12/16 1 12/23 1
January
12/30 1 1JS
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Project: Application! of Guidance
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Task Name
Taskl
Draft QAPP
EPA Review of Draft QAPP
Final QAPP
Site Selection and Coordination
Site-Spec! fie QAPP
Task 2
Sitel Field Work
Site 1 Data Analysis
Site 1 Case Study
Site 2 Field Work
Site 3 Field Work
Site 2 Data Analysis
Site 3 Data Analysis
Site 2 Case Study
Site 3 Case Study
EPA Review of Case Studies
TaskS
Revise Draft Guidance
Revise Draft Fact Sheet
EPA Review Drafts
Final Guidance
Final Fact Sheet
Duration
154 days
22 days
68 days
30 days
20 days
1 5 days
93 Days
1 0 days
25 days
13 days
1 0 days
1 0 days
25 days
25 days
8 days
8 days
20 days
30 Days
1 0 days
1 0 days
10 days
10 days
1 0 days
Start
Mon 7/23/01
Mon 7/23/01
Wed 8/22/01
Fri 11/30/01
Wed 1/23/02
Wed 2/1 3/02
Mon 4/8/02
Mon 4/8/02
Mon 4/22/02
Tue 5/28/02
Mon 4/29/02
Mon 5/20/02
Mon 5/13/02
Tue 6/4/02
Tue 6/1 8/02
Wed 7/1 0/02
Mon 7/22/02
Mon 8/19/02
Mon 8/19/02
Mon 8/19/02
Tue 9/3/02
Tue 9/1 7/02
Tue 9/1 7/02
Project: Application of Guidance
For Evaluating Landfill Gas Emissions at Superfund Sites
Finish
Wed 3/6/02
Tue 8/21/01
Thu 11/29/01
Tue 1/29/02
Wed 2/20/02
Wed 3/6/02
Fri 8/1 6/02
Fri 4/19/02
Fri 5/24/02
Thu 6/13/02
Fri 5/10/02
Mon 6/3/02
Mon 6/17/02
Tue 7/9/02
Thu 6/27/02
Fri 7/19/02
Fri 8/16/02
Mon 9/30/02
Fri 8/30/02
Fri 8/30/02
Mon 9/1 6/02
Mon 9/30/02
Mon 9/30/02
| February March
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Task Name
Taskl
Draft QAPP
EPA Review of Draft QAPP
Final QAPP
Site Selection and Coordination
Site-Spec! fie QAPP
Task 2
Sitel Field Work
Site 1 Data Analysis
Site 1 Case Study
Site 2 Field Work
Site 3 Field Work
Site 3 Data Analysis
Site 2 Case Study
Site 3 Case Study
EPA Review of Case Studies
Task3
Revise Draft Guidance
Revise Draft Fact Sheet
EPA Review Drafts
Final Guidance
Final Fact Sheet
Duration
154 days
22 days
68 days
30 days
20 days
1 5 days
93 Days
1 0 days
25 days
13 days
1 0 days
1 0 days
25 days
8 days
8 days
20 days
30 Days
1 0 days
1 0 days
10 days
10 days
1 0 days
Start
Mon 7/23/01
Mon 7/23/01
Wed 8/22/01
Fri 11/30/01
Wed 1/23/02
Wed 2/1 3/02
Mon 4/8/02
Mon 4/8/02
Mon 4/22/02
Tue 5/28/02
Mon 4/29/02
Mon 5/20/02
Tue 6/4/02
Tue 6/1 8/02
Wed 7/1 0/02
Mon 7/22/02
Mon 8/19/02
Mon 8/19/02
Mon 8/19/02
Tue 9/3/02
Tue 9/1 7/02
Tue 9/1 7/02
Project: Application! of Guidance
For Evaluating Landfill Gas Emissions at Superfund Sites
Finish
Wed 3/6/02
Tue 8/21/01
Thu 11/29/01
Tue 1/29/02
Wed 2/20/02
Wed 3/6/02
Fri 8/1 6/02
Fri 4/19/02
Fri 5/24/02
Thu 6/13/02
Fri 5/10/02
Mon 6/3/02
Tue 7/9/02
Thu 6/27/02
Fri 7/19/02
Fri 8/16/02
Mon 9/30/02
Fri 8/30/02
Fri 8/30/02
Mon 9/1 6/02
Mon 9/30/02
Mon 9/30/02
| May
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Task Name
Taskl
Draft QAPP
EPA Review of Draft QAPP
Final QAPP
Site Selection and Coordination
Site-Spec! fie QAPP
Task 2
Sitel Field Work
Site 1 Data Analysis
Site 1 Case Study
Site 2 Field Work
Site 3 Field Work
Site 2 Data Analysis
Site 3 Data Analysis
Site 2 Case Study
Site 3 Case Study
EPA Review of Case Studies
Task 3
Revise Draft Guidance
Revise Draft Fact Sheet
EPA Review Drafts
Final Guidance
Final Fnrl She^t
Duration
154 days
22 days
68 days
30 days
20 days
1 5 days
93 Days
1 0 days
25 days
13 days
1 0 days
1 0 days
25 days
25 days
8 days
8 days
20 days
30 Days
1 0 days
1 0 days
10 days
10 days
1 0 Hnu<:
Start
Mon 7/23/01
Mon 7/23/01
Wed 8/22/01
Fri 11/30/01
Wed 1/23/02
Wed 2/1 3/02
Mon 4/8/02
Mon 4/8/02
Mon 4/22/02
Tue 5/28/02
Mon 4/29/02
Mon 5/20/02
Mon 5/13/02
Tue 6/4/02
Tue 6/1 8/02
Wed 7/1 0/02
Mon 7/22/02
Mon 8/19/02
Mon 8/19/02
Mon 8/19/02
Tue 9/3/02
Tue 9/1 7/02
Tue 9/1 7/02
Project: Application of Guidance
For Evaluating Landfill Gas Emissions at Superfund Sites
Finish
Wed 3/6/02
Tue 8/21/01
Thu 11/29/01
Tue 1/29/02
Wed 2/20/02
Wed 3/6/02
Fri 8/1 6/02
Fri 4/19/02
Fri 5/24/02
Thu 6/13/02
Fri 5/10/02
Mon 6/3/02
Mon 6/17/02
Tue 7/9/02
Thu 6/27/02
Fri 7/19/02
Fri 8/16/02
Mon 9/30/02
Fri 8/30/02
Fri 8/30/02
Mon 9/1 6/02
Mon 9/30/02
Mnn QA1fi/n5
[Ajjgust
7/14
7/21 7/28 8/4 8/11 8/18 8/25
Task
Split
Progress
Milestom
*•
JMMM dj
Summary ^^^•^^^^ E:
Project Summary ^^^•^^^^ D(
External Milestone +
September
9/1 1 9/8 1 9/15 1 9/22 1
1
1 -
ternal Milestone +
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October
9/29 1 10/6
PageS
00
ON
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these premises, quantitative objectives are established for critical measurements in terms of data
quality indicators goals for accuracy, precision, and completeness.
The overall QA objective is to determine if the LFG emissions to the ambient air and subsurface
vapor intrusion into buildings create acceptable or unacceptable inhalation risks or hazards of fire or
explosion and whether potential ambient air ARARs may be exceeded.
The objectives are achieved if as a result of conducting the field investigation and implementing
the guidance one can:
• Determine compliance with air pathway specific ARARs,
• Determine if the methane concentration at receptors is greater than 25 percent of the LEL, and
• Determine if the health risks due to LFG migration and vapor migration from groundwater to
off-site receptors are acceptable.
The guidance document assumes that the user will gather available information and that said
information has been generated in a manner consistent with good management practices. The conduct
of basic research or resolution of disputes concerning the following is beyond the scope of work for
this project:
• Age of landfill,
• Dimensions and cross sections of landfill,
• Content of landfill and identification of COPCs on a section-by-section basis,
• Annual waste acceptance rate,
• Design basis of the landfill cover, and
• Design basis of the LFG collection and vent system .
It should be noted, however, that the adequacy and correctness of the existing information may
materially affect the outcome and decisions that are made concerning health risk and explosion
hazards.
For QA purposes the existing site data and information will be accepted and used if:
• It has been publicly acknowledged and accepted by EPA and
• It has been included in the publicly available site-specific records and documents and there has
been no dispute concerning the validity or acceptability of the records and documents.
If there are data gaps in the existing data and information, the site-specific case study will note the
critical data gap(s).
For QA purposes physical and chemical data will be accepted if it is from standard and commonly
accepted references (e.g., CRC Handbook of Chemistry).
QA objectives and protocols for the field sampling and analysis portion of the project are
summarized in Table A-4. The number of samples to be collected for this project/event are site
specific and will be included in an appendix at least 30 days prior to conducting the field activities
presented in Table A-4. This table identifies analytical parameters desired; type, volume, and number
of containers needed; preservation requirements; number of samples to be collected; and associated
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number and type of QA/QC samples based on QA level III. All project deliverables will receive an
internal peer review prior to release. The following QA protocols are applicable to the sample
matrices:
1. Sample documentation in the form of field logbooks, the appropriate field data sheets, and
COC forms will be provided. COC sheets are optional for field screening locations.
2. All instrument calibrations and performance check procedures or methods will be summarized
and documented in the field/personnel or instrument log notebook.
3. Detection limit(s) will be determined and recorded, along with the data, where appropriate.
4. Sample holding times will be documented; this includes documentation of sample collection
and analysis dates.
5. Initial and continuing instrument calibration data will be provided.
a. For air samples, lot blanks, field blanks, collocated samples, trip blanks, and breakthrough
samples will be included.
b. For soil gas samples, duplicate samples, zero air samples, field standards, ambient air
samples, and matrix spikes will be included.
Table A-4. Field Sampling Summary for Each Site
Source
Landfill
cover,
passive
vents,
extractive
vents
Parameter
A. CH4
screen
B. CH4 QC
duplicate
C. NMOC
screen
D. NMOC
QC duplicate
E. Organic
COPCs
F. Organic
COPC QC
collocate/
split
G. Fixed gas
H. Fixed gas
QC collocate/
split
I. Trip/plot
blank
Media
in situ
in situ
in situ
in situ
Tedlar bag
or Summa
cannister
Summa
cannister
in situ
Summa
cannister
Summa
cannister
Holding
Time3
Direct read
instrument
Direct read
instrument
Direct read
instrument
Direct read
instrument
7 day
7 day
Direct read
instrument
7 day
7 day
Flow Rate,
L/min
1.0
1.0
1.0
1.0
0.1
0.1
1.0
0.1
Volume,
L
1.0
1.0
1.0
1.0
1.0 to 6.0
6.0
1.0
6.0
6.0
No. of
Samples
TBD
5% A
TBD
5%C
3 per
homogeneous
area
5%E
E
5%G
10% For
I/day
continued
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Source
Native
Offsite Soil
Air
(ambient or
indoor)
Parameter
A. CH4
B. CH4 QC
Duplicate
C. Organic
COPCs
D. Organic
COPC - QC
duplicate
E. Organic
COPC QC
collocate/
split
F. Soil
properties
G. Soil
properties
QC Duplicate
H.Gas
pressure
I. Gas
pressure QC
Duplicate
J. Trip/lot
blank
A. Organic
COPC
B. Organic
COPC QC
Duplicate
C. Trip/lot
blank
Media
Tedlar bag
or Summa
cannister
Summa
cannister
Tedlar bag
or Summa
cannister
Summa
cannister
Summa
cannister
Split barrel
Split barrel
in situ
in situ
Summa
cannister
Summa
cannister
Summa
cannister
Summa
cannister
Holding
Time3
7 day
7 day
7 day
7 day
7 day
24 h
24 h
Direct read
instrument
Direct read
instrument
7 day
7 day
7 day
7 day
Flow Rate,
L/min
0.01
0.01
0.01
0.01
0.01
NAb
NA
NA
NA
0.01
0.01
0.01
0.01
Volume,
L
1.0 to 6.0
6.0
1.0 to 6.0
6.0
6.0
0.5
0.5
NA
NA
6.0
6.0
6.0
6.0
No. of
Samples
TBD
5% A
TBD
5%C
5%D
TBD
5%F
TBD
5%H
10%Eor
I/day
TBD
5% A
10%Bor
I/day
a All samples are unpreserved, stored at temperatures between 65 and 75 °F and away from sunlight.
b NA = not applicable.
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6. Performance evaluation (PE) samples are not anticipated but may be included at the discretion
of the TOM.
7. The following three options are applicable:
a. Definitive Identification - analyte identification on 10 percent of the screened (field or lab)
or 100 percent of the unscreened samples will be confirmed using a U.S. EPA-approved
method; documentation such as chromatograms, mass spectra, etc., will be provided.
b. Quantitation - documentation for quantitative results from screening and U.S. EPA-
approved verification methods (for screened samples) or quantitative results (in the case
of unscreened samples) will be provided.
c. Analytical Error - the analytical error will be determined by calculating the precision,
accuracy, and coefficient of variation on a subset of the screened samples or on all of the
unscreened samples using an EPA-approved method.
The quality components of precision, accuracy, representativeness, completeness, and compar-
ability for this project are discussed below. This QAPP applies to any project site that requires
sampling or monitoring. Site-specific information, however, will be addressed in a site-specific
QAPP.
A. 4.1 Precision and Accuracy
Uncertainty associated with the measurement data is expressed in terms of accuracy and precision.
The accuracy of a single value contains the component of random error in a measurement and also
the systematic error, or bias. Accuracy thus reflects the total error for a given measurement. Precision
values represent a measure of only the random variability for replicate measurements. In general, the
purpose of calibration is to eliminate bias, although inefficient analyte recovery or matrix inter-
ferences can contribute to sample bias, which is typically assessed by analyzing matrix spike samples.
At very low levels, blank effects (contamination or other artifacts) can also contribute to low-level
bias. Bias can also be introduced by laboratory contamination. The potential for bias is evaluated by
method blanks. Instrument bias is evaluated by control samples.
Calibration standards, QC check samples, and performance evaluation samples will be prepared
from vendor-certified standards or generated from stock materials of known purity. Records of the
preparation and validation of all QA/QC-related samples will be maintained by the laboratories
responsible for the analyses. Laboratories will be identified in the site-specific QAPPs.
Experience in conducting volatile organic compound (VOC) measurement programs has shown
that the typical analytical precision values that can be attained, measured as the percent coefficient
of variation (%CV), are <50 percent for electrolytic conductivity detector (ELCD) compounds and
<30 percent for flame ionization detector (FID) compounds and fixed gases. Accuracy values of
between 50 and 150 percent recovery can typically be achieved for the ELCD compounds, and
recoveries between 70 and 130 percent can typically be achieved for the FID compounds and fixed
gases. The instrument detection limit for many of the VOC compounds are typically below 1 ppbv
for low-lev el samples. In high-level samples, however, compounds present in low concentrations will
be masked by the largest peaks or will be below detectable quantities because of dilution or injection
volume considerations. This is particularly a problem when one or two compounds are orders of
magnitude higher in concentration than the remaining compounds in the sample. These matrix effects
can adversely affect the precision and accuracy of the method.
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The soil gas and air samples being collected as part of this project are expected to be relatively
low in concentration, resembling unaffected ambient air samples, while the extractive/passive vent
samples are expected to contain ppm-level concentrations (e.g., 5-250 ppm) of hydrocarbons. Both
sample sets will be quantitated for the same list of target analytes (Table A-l). The main differences
in the two analyses will be the method the samples are injected into the chromatograph and the
number and concentration of the calibration standards. Tables A-5, A-6, and A-7 list the accuracy,
precision, and targeted/estimated detection limits for a subset of the target analytes. Analytical
detection limits are matrix, laboratory, instrument specific. Each laboratory will be required to
explain and justify only differences that are discovered during the project. Table A-5 shows
anticipated limits for the low-level analysis (i.e., soil gas samples) for compounds where these limits
have been experimentally and empirically determined. This same information for the high-level
samples (i.e., vent and gas collection system samples) is shown in Table A-6. For compounds not on
these lists, the accuracy, precision, and detection limits may or may not have been empirically
determined. The collection of duplicate samples during this program will help assess the precision
of the other compounds; however, for cost control purposes and because the information is not
needed to meet the project objectives, no attempt will be made to derive empirical detection limits
or accuracy estimates for compounds not included in the site-specific target analytes list (TAL).
Table A-5. Summary of Precision, Accuracy, and Detection Limits for VOC Analysis of Air
Samples, Low-level Sample Technique.
Analyte (VOC Compound Number)
Analytical
Precision3
Analytical
Accuracy6
Target Detection
Limits0 (ppbv)
PRIMARY COMPOUND LIST (Includes TO-14 Compounds): These compounds are monitored daily for
precision and accuracy.
Benzene46'58 (#79)
Benzyl chloridef & m-dichlorobenzenef (#230)
Chlorobenzenef (#128)
Ethylbenzened-e'f(#129)
n-Decanee & p-dichlorobenzenef (#23 1)
o-Dichlorobenzenef'h (#163)
o-Xylene4*'1 (#137)
p-Xylene & m-xylene46' (#131)
Methane
Arcylonitrile
Ethylene Dibromide
Toluene^^lll)
1, 1, l-Trichloroethanef (methyl chloroform - #76)
l,2-Dichloroethanef'g (#74)
l,l-Dichloroethylenef (vinylidene chloride - #42)
Caibon tetrachloridef (#80)
Chloroethanef (ethyl chloride - #21)
Chloroformf(#67)
Dichlorodifluoromethanef (freon 12 - #7)
30%
50%
30%
30%
30%
30%
30%
30%
30%
30%
30%
30%
50%
50%
50%
50%
50%
50%
50%
70-130%
50-150%
50-150%
50-150%
50-150%
50-150%
50-150%
70-130%
70-130%
70-130%
70-130%
70-130%
50-150%
50-150%
50-150%
50-150%
50-150%
50-150%
50-150%
0.4
0.6
0.5
0.7
0.7
0.7
0.5
1.0
0.2
0.2
0.7
0.5
0.2
0.2
0.2
0.5
0.2
0.1
0.2
continued
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Analyte (VOC Compound Number)
Methylene chloridef>B (dichloromethane - #44)
Tetrachloroethylenef (#125)
Trichloroethylenef & Bromodichloromethane (#235)
Vinvlchloridef(#10)
Analytical
Precision3
50%
50%
50%
50%
Analytical
Accuracy1"
50-150%
50-150%
50-150%
50-150%
Target Detection
Limits0 (ppbv)
0.2
0.1
0.1
0.3
a Analytical precision is measured from duplicate analysis of the daily calibration standard (DCS) or continuing calibration
checks (CCCs) at a concentration of 2-8 ppbv for primary compounds.
b Analytical accuracy is measured using two sigma control charts using DCS recoveries or from laboratory control sample
recoveries when available (see footnote e). No more than two compounds from FID and three compounds from ELCD (or the
appropriate 95% Poison probability value) should exceed these tolerances in any valid standard analysis for the system to be in
statistical control. NOTE: This measurement reflects analytical accuracy and does not include sampler recovery, storage
stability, or matrix effects.
c Instrument detection limits (IDLs) for core compounds represent the most conservative measured value (rounded up) based on
seven replicate detection limit determination studies. These IDLs may change with actual IDL determination and sample
matrix. The IDLs listed for TAL represent a one-time seven replicate detection limit study. NOTE: These detection limits
assume a dilution factor of 1. This procedure is based on guidance contained in 40 CFR Part 136 Appendix B.
d Compounds in standard used to measure database (qualitative) accuracy.
e Compounds used to determine carbon response factor accuracy with a second source standard.
fTO-15analyte.
g Analytical individual response factor (IRF) accuracy will be determined by comparing compounds common in both the
individual response factor laboratory control standard (IRF-LCS) and the DCS.
h Compound may coelute with other compounds in typical VOC sample patterns. Polar compounds may coelute with several
compounds, especially when present at high concentration.
1 Carbon response factor, not an IRF, will be used for quantitation because of chromatographic coelution in the DCS.
Table A-6. Summary of Precision, Accuracy, and Detection Limits for VOC Analysis of Air
Canister Samples, High-Level Sample Technique
Analyte (VOC Compound Number)
Analytical
Precision3
Analytical
Accuracy*
Target Detection
Limits0 (ppbv)
CALIBRATED COMPOUND LIST: These compounds are monitored on daily basis. This is a high level
standard.
Benzene4e'f'g (#79)
Benzyl chloridef & m-dichlorobenzenef (#230)
Chlorobenzenef (#128)
Ethylbenzene4e'f(#129)
n-Decanee & p-dichlorobenzenef (#23 1)
o-Dichlorobenzenef'h (#163)
o-Xylene401'1 (#137)
p-Xylene & m-xylene46' (#131)
Toluene^ (#111)
1, 1, l-Trichloroethanef (methyl chloroform - #76)
l,2-Dichloroethanef'g (#74)
l,l-Dichloroethylenef (vinylidene chloride - #42)
Carbon tetrachloridef (#80)
Chloroethanef (ethyl chloride - #21)
Chloroformf (#67)
Chloromethanef (methyl chloride - #5)
30%
50%
30%
30%
30%
30%
30%
30%
30%
50%
50%
50%
50%
50%
50%
50%
70-130%
50-150%
50-150%
50-150%
50-150%
50-150%
50-150%
70-130%
70-130%
50-150%
50-150%
50-150%
50-150%
50-150%
50-150%
50-150%
100
150
125
175
175
175
125
250
125
50
50
50
125
50
25
250
continued
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Analyte (VOC Compound Number)
Dichlorodifluoromethanef (freon 12 - #7)
Methylene chloridef>B (dichloromethane - #44)
Tetrachloroethylenef (#125)
Trichloroethylenef
c- 1 , 3 -Dichloroethylene
t- 1 ,3 -Dichloroethylene
Vinvlchloridef(#10)
Analytical
Precision3
50%
50%
50%
50%
50%
50%
50%
Analytical
Accuracy1"
50-150%
50-150%
50-150%
50-150%
50-%50
50-150%
50-150%
Target Detection
Limits0 (ppbv)
50
50
25
25
50
50
75
1 Analytical precision is measured from duplicate analysis of the daily calibration standard (DCS) or continuing
calibration checks (CCCs) at a concentration of 2-8 ppbv for primary compounds.
3 Analytical accuracy is measured using two sigma control charts using DCS recoveries or from laboratory control
sample recoveries when available (see footnote e). No more than two compounds from FID and three compounds
from ELCD (or the appropriate 95% Poison probability value) should exceed these tolerances in any valid
standard analysis for the system to be in statistical control. NOTE: This measurement reflects analytical accuracy
and does not include sampler recovery, storage stability, or matrix effects.
: Instrument detection limits (IDLs) based on a load volume of 0.5 mL for core compounds represent the most
conservative measured value (rounded up) based on seven replicate detection limit determination studies. These
IDLs may change with actual IDL determination and sample matrix. NOTE: These detection limits assume a
dilution factor of 1. This procedure is based on guidance contained din 40 CFR Part 136 Appendix B.
1 Compounds in standard used to measure database (qualitative) accuracy.
: Compounds used to determine carbon response factor accuracy with a second source standard.
fTO-15analyte.
1 Analytical individual response factor (IRF) accuracy will be determined by comparing compounds common in
both the Individual response factor laboratory control standard (IRF-LCS) and the DCS.
1 Compound may coelute with other compounds in typical VOC sample patterns. Polar compounds may coelute
with several compounds, especially when present at high concentration.
Carbon response factor, not an IRF, will be used for quantitation because of chromatographic coelution in the
DCS.
Table A-7. Summary of Precision, Accuracy and Completeness Goals for Physical Parameters.
Parameter
Precision
Accuracy (%)
Fix Gas (CO2, CH4, N2, O2)
Gas Standard
Calibration Error
Sampling Bias
Zero and Drift
5% RSD
NAa
NA
NA
20% Bias
2% Bias
5% Bias
3% Bias
Soil Properties
Percent Moisture
Bulk Density
Particle Density
Particle Size
Balance Calibration Check
5% RSD
5% RSD
5% RSD
5% RSD
0.5 g
5
5
5
5
5
Completeness
80
80
JNA = not applicable.
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The Guidance for Evaluating Landfill Gas Emissions at Closed or Abandoned Sites (EPA-600/R-
05/123a) notes that modern analytical techniques are not capable of achieving a detection or
quantitation limit that would demonstrate there is no significant risk (e.g., 1 x 10"6) for at least seven
of the COPCs. The guidance assumes that if the COPC is measurable and quantifiable, then one can
determine if LFG controls are necessary and if the risks are acceptable. The guidance recommends
that if the laboratory does not detect a specific COPC in any sample then the chemical be excluded
from the risk and remediation analysis. If the laboratory reports a COPC concentration for some
samples but no COPC concentration for other samples, then a value equal to 50 percent of the
quantitation limit will be assigned to the non-detects (NDs) and the average concentration be
calculated accordingly.
Analytical precision estimates for this program will be based on the collection and analysis of
duplicate samples collected from different locations across the landfill. A discussion of the
experimental design, including duplicate sample collection, is presented in Section B.I. Duplicate
samples will be collected at a minimum frequency of 5 percent of the total number of samples. In
order to assess both sampling and analytical precision, a nested design will be used with each
duplicate also being analyzed in duplicate.
Accuracy estimates for the TAL list will be obtained by analyzing known standards or spiked
samples—i.e., lab control standard (LCS) and LCS duplicate (LCSD) samples. Accuracy estimates
for the on-site analyzers will be obtained by analyzing certified standards.
A. 4.2 Representativeness
A key consideration is collecting enough samples to adequately incorporate the large spatial
variability inherent in a population of gaseous emissions. Soil vapor sites generally depict seasonal
patterns that fluctuate in response to soil surface-sealing events such as precipitation and frost, in
contrast to dry warm periods. Precipitation and frost tended to alter the physical structure of the soil
pore spaces, rendering the soil less permeable. During soil surface-sealing events, the preferential
escape route for soil gas flow is through the unrestricted soil vapor wells due to their penetration
through the surface seal. (Similar responses have been noted in protected crawl spaces beneath
homes.) The literature indicates that annual cycles depict highest methane concentrations around
spring thaws, secondarily high concentrations around early fall, and the rest of the year showing
considerably lower concentrations. From an environmental perspective, the most disconcerting
changes are those noted at monitoring locations that initially had low-to-insignificant combus-tible
gas concentrations, but later exhibited escalating LEL values. Long-term temporal variability is not
represented in this study. Short-term variability will be incorporated and assessed.
Emission samples will be collected at approximately 20 sample points following a preliminary
screen for areas of higher emissions (described in Section A-6 under Task 2). Section B. 1 discusses
the rationale for the sampling design. Thus, a biased sampling approach is intended to ensure that the
areas of higher emissions are included in the sample design. The soil gas emissions are expected to
be relatively small compared with the passive vent emissions. All of the passive vents will be screened
for flow rates and LFG to ensure the most accurate representation of this parameter.
Samples from the gas extraction system will be collected from each vent. The combined header
is the best location to obtain a representative sample of LFG because this source is a spatial composite
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of all the extraction wells. Although it will be necessary to collect grab (rather than time-integrated)
samples, samples will be collected at different times over the course of the study to incorporate short-
term sample variation in the design and obtain the best representation of the extracted LFG.
Nongaseous samples are also scheduled to be analyzed for the TAL and other physical chemical
properties. These include native soils, landfill cover soils, and potentially, groundwater. These
samples will all be collected in a way to ensure that the samples are representative of the time and
space they inhabit, but the sample design is not intended to incorporate the large component of spatial
or temporal variability. These samples will, therefore, not purport to represent the landfill site as a
whole or the surrounding areas.
A. 4.3 Completeness
Data completeness, or the rate of data capture, is defined as the percentage of the total number of
observations of a given parameter that is considered valid. For these sample types, data completeness
will equal the number of valid sampling and analysis events divided by the total number of sampling
and analytical episodes attempted. The data capture objective for this program is 80 percent.
A.4.4 Data Usability
The analytical data will be reviewed and checked against the defined quality specifications for
each method. The effect of failing to meet any objective depends on the particular situation. In any
case, when the quality criteria are not met, the effect will be evaluated and discussed in the final data
report. Corrective action will be initiated, as appropriate. Any qualifications in the usability of the data
will be delineated.
A.5 Special Training/Certification
Quality work can only be expected from staff who are qualified to perform project assignments.
As a minimum, project personnel shall receive training, as applicable, on (1) QAPPs, (2) site health
and safety plans, and (3) instrument calibration procedures. The sites are undergoing a hazardous
substance response that is covered under CERCLA; as such, employees (including contractor
employees) engaged in field activities are subj ect to the Occupational Safety and Health Act (OSHA)
standards specified in 40 CFR 1910.120. All field workers must demonstrate that they have received
a minimum of 40 hours of training prior to arriving on site.
Additionally, on-site management and supervisors must demonstrate that they have received at
least eight additional hours of specialized training on managing hazardous substance operations.
Project staff conducting site work shall be under the direct supervision of a trained and experienced
supervisor for at least three days before routine operations may begin. The contractor anticipates that
site-specific health and safety training will be conducted by the site safety and health officer as
designated by the RPM.
At least one field team member, prior to arrival onsite, will be trained on the Department of
Transportation standards that are applicable when shipping hazardous materials.
The sampling, monitoring, analytical, and data reduction techniques and procedures are believed
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to be routine and standardized. Each person assigned a duty or task shall have demonstrated
proficiency and experience prior to arriving at the site or conducting an assigned task. Records of
personnel qualification and training are to be maintained by each participating organization.
Affirmative statements from each person participating in the field project will be obtained to indicate
that the person has been appropriately trained on the QAPP, calibration procedures, health and safety
plan, and OSHA requirements prior to their being allowed to work on the sites. This information shall
be recorded in a log book by the field team manager.
A.6 Documents and Records
Document control is the process of ensuring that documents are reviewed for adequacy, approved
for release or distribution, and used where a prescribed activity is to be performed. Record control is
the process of providing ready and reliable storage, protection and disposition of records. The records
manager will prepare an index of the records used to complete this project.
The TOM will be responsible for ensuring that the most up-to-date and approved version of the
QAPP has been distributed to those persons identified on the distribution list.
The following types of records will be compiled. The RPM will provide an index and cross
reference to all site-specific documents and files that are being used to provide the historical data
concerning the site. This index will be included in the project files and stored until the project records
are disposed.
• Field Logbooks - The field team manager is responsible for ensuring that logbooks include
sufficient information to document the events so that reliance on memory is minimized. The
title page of each logbook will include:
S Person to whom the logbook is assigned,
S Logbook number,
S Project name,
S Start date,
S End date, and
S Number of completed pages.
Entries into the logbook will include but not be limited to:
S Names of persons conducting field activities;
S Level of personal protection equipment;
S Signature of person making entry;
S Sample number and description of sample event;
S Equipment and methods used;
S Climatic conditions;
S Sample location (coordinates and description);
S Instrument readings and reference to raw data sheets used;
S Changes and variance from SOPs (nonconformance document);
S Corrective actions taken to correct and minimize impact of nonconforming actions
(corrective action report);
S Field data, observation notes, and calibration results; and
S Description of packaging, shipping, and custody records.
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• COC Records - COC forms will be used to ensure that sample custody is documented.
Standardized COC forms and procedures will be followed. A copy of the COC form used for
each group of samples will be placed in the project files.
• QC Sample Records - Information needed to document the generation of QC samples (such as
field, trip, equipment, duplicate, and matrix spike) shall be compiled and placed in the project
files. The information will include documentation on sample integrity and preservation,
calibration, and standards traceability.
• Corrective Action Reports - These reports will be compiled whenever there is a variance from
the QAPP. The report will describe the reasons for the variance and document the effects on
the data usability.
• Manifest Records - If applicable and necessary to show regulatory compliance, copies of
manifest records will be prepared and placed in the project records.
• Laboratory Records - Each laboratory will compile and maintain sufficient records to
document that samples were managed in accordance with the site-specific QAPP and the
laboratory-specific QAPP. Each laboratory shall include the following information as part of
its deliverable:
S Sample data (e.g., run date and time, batch number, quantity, results),
S Sample management records (COC, handling and storage, preservation),
S Test method (sample preparation, extraction, instrument calibration results, detection and
reporting limits, test-specific QC criteria), and
S QA/QC reports demonstrating proper control and compliance with the analytical methods
or applicable SOPs.
The format of the data packages will be consistent with the site-specific QAPP requirements.
Records and project files will be retained for at least three years from the date that the revised draft
guidance document is submitted for EPA review and approval. The index of records will be retained
for at least 5 years. The record will be retained at the contractors project office.
The evidence files for analytical data will be maintained at the contractor's Project Management
Office. The content of the evidence file will include all relevant records, reports, correspondence,
logs, field logbooks, laboratory sample preparation and analysis logbooks, data package, pictures,
subcontractor's reports, COC records/forms, data review reports, etc. The evidence file will be under
custody of , in a secured area.
Raw data from the VOC chromatograms will be stored on magnetic tape or disks. Other analytical
data (i.e., records of injections, volumes, dilutions, and absorbency values) will be recorded in bound
paginated instrument logbooks. All logbook entries will be dated and initialed by the author. In
addition to the analytical results, the preparation of analytical standards and QC samples will also be
documented. Typical information will include the dates of preparation for stock standards,
manufacturers' lot numbers, preparation procedures, and so forth. Chromatograms, standard curves,
and other laboratory documentation will be maintained in a central file for future inspection. Copies
of instrument logbooks and maintenance records will also be available for review.
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ELEMENT B. DATA GENERATION AND ACQUISITION
B.I Sampling Process Design
Although this QAPP applies to all sites being monitored and sampled, specific sampling process
design can only by addressed on a site-specific basis.
The information needed to determine the practicality and usefulness of the guidance will be
captured by observing the field activities, documenting issues and questions that arise, determining
if the required data was obtained, and seeking input from the proj ect participants concerning the level
of effort required versus the level of effort anticipated. The project team led by the TOM will
collaboratively determine if the guidance was practical and useful.
This document describes a monitoring program designed to estimate the emission rates and the
concentrations of methane and other chemicals of potential concern. The experimental design is to
study the composition and emission rates of the landfill gas being emitted to ambient air. Each of the
three selected landfill sites will be sampled to:
• Provide the landfill gas composition that is representative of each section of the landfill as a
whole,
• Provide the landfill gas composition at the landfill boundary in the subsurface strata,
• Provide the landfill gas composition in the subsurface strata immediately above a groundwater
plume and adjacent to potentially affected off-site structures,
A general overview of the sampling and monitoring approach is provided in Table B-l.
The limitations inherent in this study include logistical constraints on the number of samples that
can be evaluated. Spatial and temporal variability are considered to be important variables relative
to sampling. Landfills are known to exhibit large variations in gas production from one area to the
next. The focus of the sample design is to maximize the spatial coverage by collecting LFG
information from all vents and on-site structures and from locations that are established by using a
systematic 30 m by 30 m sampling grid that is defined by the landfill cover and extends to 30 m
beyond the landfill boundary. This systematic screening technique is designed to identify hot spot
locations for both methane and NMOCs. The screening results will be used to identify up to 20
locations that will be sampled for the COPC-TAL. Depending on the landfill cover material, it is
assumed that the landfill vents will have higher LFG concentrations, and their impact on the ambient
air will be greater than the impacts derived from the surface emissions. The sample design assumes
that the emissions from the 20 locations with the highest NMOC concentration will adequately
characterize the total landfill emissions.
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Table B-1. Summary of Sampling and Analytical Approach.
Emission Source
^andfill grid size 30 x
30m plus vents and
msite structures
.andfill NMOC hot
spots (not to exceed 20
ocations)
'ermeable native
subsurface soil gas at
)oundary locations (not
to exceed 20 samples)
'ermeable native
subsurface soil gas at
)ff-site structure(s) (not
to exceed 3 samples)
ndoor air (not to
;xceed 3 samples)
Outdoor air (not to
;xceed 3 samples)
Parameter
CH4 and NMOC
hot spots
COPCs
COPCs
Fixed LFG (CH4,
CO2, N2, and O2)
CH4
COPC
Soil properties (%
moisture, bulk
density, particle
size,
classification)
Gas pressure
Soil properties (%
moisture, bulk
density, particle
size,
classification)
COPCs
COPCs
Sampling
Technique
Direct reading
instrument
Summa canister SOP
1704
Summa canister SOP
1704
Summa cannister
Direct reading
Summa canister SOP
1704
Summa canister SOP
1704
Split barrel SOP
2012
Direct reading
instrument
Split barrel sampling
SOP 2012
Low-level Summa
cannister SOP 1704
Low-level Summa
canister SOP 1704
Analytical Technique
On- site
Modified FRMa 21
Section 4. 3.1
TAGA-SOP 1712
Mobile GC/MS
SOP 1819
Multigas analyzer
Multigas manager
Mobile GC/MS
SOP 1819
FRM2-E
Mobile GC/MS
SOP 1819
Mobile GC/MS
SOP 1819
Off-site
TO15
FRM3C
Multigas monitor
with appropriate
detectors
TO15
ASTMD2216,
D1587, D854,
D422, D2487
ASTMD2216,
D1587, D054,
D422, D2487
1FRM = Federal reference method.
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The sample design assumes that the proximity of off-site structures to the landfill boundary is the
dominant risk driver for subsurface vapor intrusion into off-site buildings via pressure gradients. This
assumption may be invalid if there are interceptors, diversion structures, barriers, geologic faults, and
preferential vapor pathways between the landfill and the building.
The sample design assumes that up to 10 clustered LFG monitoring wells, spaced 30m apart and
situated along the landfill boundary closest to the nearest off-site building, is sufficient to delineate
the presence of a methane vapor plume. This assumption may be invalid if the LFG concentration and
pressures outside of the established study area are higher than those inside the study area. Site-specific
data concerning native soil variability, LFG concentration variability, and distances between the
nearest structure and the landfill all affect the risks posed by the landfill. The number of wells and the
spacing may be adjusted up and down at the discretion of the TOM.
The sample design assumes that the nearest off-site building may be affected by the subsurface
migration of LFG. Off-site subsurface soil gas sampling for up to three locations in the vicinity of the
nearest building is anticipated. These samples will be collected within each soil strata and as close to
the building foundations as practicable. Three indoor air and three ambient air samples may be col-
lected if screening level modeling shows potentially unacceptable risks. The ambient air samples
would be collected just outside of the building's roof drip line.
The sample design assumes that at least one building may be affected by vapor volatilizing from
contaminated groundwater. The sample design assumes that the groundwater concentration of each
COPC is already known and that soil gas sampling will be conducted in the vicinity of a building
located within the areal extent of the groundwater plume. The sample design assumes that soil gas
samples may be collected within each permeable soil strata and as close to the potentially affected
building foundation as possible.
The sample design also assumes that three indoor air samples may be collected from the basement
or an interior room of the potentially affected building located above the groundwater plume. Up to
three ambient air samples will be collected just outside of the building's roof drip line. The following
technical criteria will be used to identify the building:
• Accessibility and
• Proximity to most contaminated groundwater.
Soil gas emissions are controlled by many physical and chemical properties and processes. Soil
gas monitoring does not provide repeatable quantitative information over time because of the dynamic
nature of phase equilibria, geologic variability, temperature variability, biodegradation, abiogenic
degradation, and so forth. The study design is not intended to address temporal variability. Field
activities will be halted and rescheduled if the ground has been saturated by rain, snow, or flood
waters within 48 hours of the scheduled sampling date. The field team leaders will record in a logbook
local temperature, humidity, barometric pressure, and elapsed time since a significant (0.1 inch) rain,
snow melt, or flood.
The sample design proposes that hand-held global positioning system devices will be used to
guide the field technician in establishing the X, Y, Z coordinates for each sample or measurement
taken. The project-specific QAPP will include a local coordinate system, and it will establish a bench
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mark that will allow the locations to be plotted on a scale map of the study area. Field technicians will
use professional judgment in determining whether or not they can reasonably collect the samples or
instrument readings at the predefined location. Log notes will be used to document the rational and
decision process whenever a sample location is modified. The field technician will collect duplicate
samples at the next location if a sample cannot be collected within 15m of the predefined location.
These replicate samples will be used to evaluate reproducibility and variability of the sampling and
analysis procedures.
The maximum tolerable uncertainty associated with determining the LFG-COPC concentrations
and the pressure measurements has not been established. The concentration data will be used in
equations and models that use other parameters and constants that have a substantial degree of
uncertainty already associated with them. Expending additional resources to improve the measurement
data quality by a factor of two to five would require the use of ultra trace techniques that are much
more costly and time consuming. The sampling and analytical methods proposed herein are well
defined and commonly used.
The sample design assumes that the RPM will select the off-site building and obtain access
agreements.
The sample design assumes that the RPM will have already completed the utility checks and that
they are accurately plotted on scale drawings.
B.2 Sampling Methods
This section describes the sampling and analytical methods that will be used to complete this
project. The monitoring will consist of measuring the concentration of LFG components (CH4,
NMOCs, CO2, N2, O2, and COPCs), determinating soil properties, and determinating in situ LFG
pressure.
The soil gas samples will be collected at site-specific locations. The soil gas sampling will be
performed in accordance with U.S. EPA - ERT standard operating procedures (Laboratory-SOP 2042
- Soil Gas Sampling). The soil gas samples will be obtained by the slam-bar method to create a small-
diameter hole that is approximately 5 to 6 feet below ground surface. A narrow diameter tube will be
inserted into the hole to a point just above the bottom of the hole. The top of the hole will be sealed.
The soil gas sampling tube will be purged by use of a sampling pump before a soil gas sample is
collected.
If Summa canisters are used to collect LFG samples, all canisters will be cleaned prior to the
sampling event, by placing them in areas maintained at 150 °C; the canisters will be evacuated to at
least 10"3 torr and then pressurized with humidified nitrogen to 30 psig. This process will be repeated
three times. This process is described in Laboratory-SOP-1703 - Summa Canister Cleaning.
The extractive vents (individual gas collection wells) will be sampled for gas temperature, gas
flow rate, and gas composition, including methane, carbon dioxide, total NMOCs and the COPCs
included on the target analyte list. The moisture content will be determined on the basis of adiabatic
saturation. The extractive vents will be operating under a relatively high vacuum (e.g., 10 to 12 in.
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of Hg); hence, the cannister samples will be filled until the canister and duct pressures are equal.
Subatmospheric sampling will require a regulator, pressure gauge, and temperature gauge to be part
of the sampling equipment. The volume of gas is to be collected is fixed by the volume of the Summa
canister (6 L).
Passive vents will be sampled to determine LFG flow rates. The passive vent flow rates will be
determined using a vane anemometer or a turbine meter (EPA reference Method 2D). These methods
are intrinsically safe and simple to operate, and measurements can be conducted without modifying
the vents. The gas will be collected into Summa canisters and Tedlar bags as specified in the sampling
strategy. The sample line will be inserted several feet inside the vent. Canisters will be kept at a slight
vacuum (e.g., 1 to 4 in. Hg) following sample collection.
Ambient air sampling (indoor and outdoor) must be performed by following SOP 2105 - Air
Assessment Sampling and Monitoring Guidelines. Any ambient air samples will be collected over an
8- to 10-hr period.
The gas samples will be collected in a Summa canister(s) as specified in the sampling strategy.
Samples will be drawn into the Summa canisters in accordance with Laboratory SOP 1704 - Summa
Canister Sampling. All samples will be documented following Laboratory SOP 4001 - Log Book
Documentation, Laboratory SOP 2002 - Sample documentation, Laboratory SOP 2004 - Sample
packaging and shipment, and the COC procedures described in Section B.3.
The gas samples will be analyzed for the organic COPC target analyte list by using the mobile
GC/MS and following SOP 1819 - Analysis of Volatile Organic Compounds in air samples by Viking
Spectratrack 620 Gas Chromatography/Mass Spectrometry. All Summa canisters destined for off-site
analysis will be shipped to the laboratory that will be named in the site-specific QAPP.
B.3 Sample Handling and Custody
The following text and COC procedures will be followed.
A sample or evidence file is under one's custody if either:
• Are in your possession,
• Are in your view, after being in your possession,
• Are in your possession and you place them in a secured location, and
• Are in a designated secure area.
The sample packaging and shipment procedures summarized below will ensure that the samples
will arrive at the laboratory with the COC intact. Standard procedures for sample handling and
custody include:
• The field sampler is personally responsible for the care and custody of the samples until they
are transferred or properly dispatched. As few people as possible will handle the samples;
• All canister and bag containers will be tagged with sample numbers and locations;
• Sample tags will be completed for each sample using waterproof ink unless prohibited by
weather conditions. For example, a logbook notation would explain that a pencil was used to
fill out the sample tag because the ballpoint pen would not function in freezing weather;
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• The field team leader will review all field activities to determine whether proper custody
procedures were followed during the field work and decide if additional samples are required.
Field logbooks will provide the means of recording data collection activities performed. As such,
entries will be described in as much detail as possible so that a particular situation could be recon-
structed without reliance on memory. Field logbooks will be bound field survey books or notebooks.
Logbooks will be assigned to field personnel, but will be stored in the document control center when
not in use. Each logbook will be identified by the project-specific document number.
The title page of each logbook will contain the following:
• Person to whom the logbook is assigned,
• Logbook number,
• Project name,
• Project start date, and
• End date.
Entries into the logbook will contain a variety of information. At the beginning of each entry, the
date, start time, weather, names of all sampling team members present, level of personal protection
being used, and the signature of the person making the entry will be entered. The names of visitors
to the site, field sampling or investigation team personnel, and the purpose of their visit will also be
recorded in the field logbook.
Measurements made and samples collected will be recorded. All entries will be made in ink and
no erasures will be made. If an incorrect entry is made, the information will be crossed out with a
single strike mark. Whenever a sample is collected, or a measurement is made, a detailed description
of the location of the station, which includes compass and distance measurements, will be recorded.
The number of the photographs taken of the station, if any, will also be noted. All equipment used to
make measurements will be identified, along with the date of calibration.
Samples will be collected following the sampling procedures documented in the site-specific
QAPP. The equipment used to collect samples will be noted, along with the time of sampling, sample
description, depth at which the sample was collected, volume, and number of containers. A sample
identification number will be assigned prior to sample collection. Field duplicate samples, which will
receive an entirely separate sample identification number, will be noted under sample description.
The COC form is used to track and document unbroken custody of samples as identified by the
unique sample number. The contractor's standard form is shown on Figures B-l and B-2. Blank
forms can be obtained by contacting The contractor's QA/QC staff personnel. The original COC form
will be kept by the receiving laboratory and will accompany the analytical report. A copy of the COC
form from each group of samples will be supplied to the contractor's's QA/QC chemist, and a copy
will be placed in the project files.
-------
^Environmental Quality Management, Inc.
f Environmental Quality
f\ Management. Inc.
Project Name
Project Number
Project Manager
Sample Team Leader
ANALYSIS REQUEST AND
CHAIN OF CUSTODY RECORD
Lab Destination
Lab Contact/Phone
Lab Purchase Order No.
Carrier/Waybill No.
Reference Document No,
Page 1 of
Report to:
Bill to:
ONE CONTAINER PER LINE
Sample Number
Sample Description/Type
Date/Time
Collected
Container
Type
Special Inslruetions:
Possible Hazard Identification:
Non-hazard D Flammable D Skin Irritant D Other
Turnaround Time Required:
Normal !H Rush D Results Required by
Sample
Volume
Pre-
servative
Requested Analytical
Method/(Parameters)
Condition of
Receipt (Lab)
Sample Disposal:
Return to Client D Disposal by
Lab C1 Archive (mos.)
QA Requirements:
1 . Relinquished by Date:
(Signature/Affiliation) Time:
2. Relinquished by Date:
(Signature/Affiliati
on) Time:
1 . Received by
(Signature/Affiliation)
2. Received by
(Signature/Affiliation)
Date:
Time:
Date:
Time:
Comments:
Figure B-1. Chain-of-Custody Form.
ft 55
o o
o
(Jl
-------
Environmental Quality
Management, Inc.
Project Name
ANALYSIS REQUEST AND
CHAIN OF CUSTODY RECORD
Project No.
Reference Document No.
Page of
C\ <-*•> O*
o -r §
Sample Shipment Date
ONE CONTAINER PER LINE
Sample
Number
Sample
Description/Type
Date/Time
Collected
Container
Type
Sample Volume
Pre-
servative
Requested Analytical
Method/(Parameters)
Condition of
Receipt
Figure B-1. Chain-of-Custody Form (continued).
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Stainless Steel Canister Chain-of-Custody
To be Completed by Field Sampler
Sample Control Number
Canister Number
Date Sampled
Well/Station Number
OVA Reading (Peak)
Address/Refinery Location
Sampler's Initials
Type (Circle One) Ambient or Point Source (specify):
Time:
Comments:
To be Completed by Lab (Part One)
Operation
1. Canister Cleaned
2. Canister Blanked
3. Filter Cleaned
4. Canister Evacuated
5. Canister Shipped
6. Canister Received
7. Analysis Completed
8. Sample Discarded
Date
Initials
Comments
Pressure:
APL =
APF =
APL-APF=
To be Completed by Lab (Part Two)
Parameter
Dilution 1
Dilution 2
Dilution 3
Dilution 4
Initial Pressure
Final Pressure
AddUHPAir
Dilution Factor
FINAL Dilution Factor
Dilution Date
Dilution Time
Initials
Figure B-2. Chain-of-Custody Report for Canister Samples.
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Samples will be accompanied by a properly completed COC form, and the sample numbers and
locations will be listed on the COC form. When transferring the possession of samples, the individuals
relinquishing and receiving will sign, date, and note the time on the record. This record documents
transfer of custody of samples from the sampler to another person, to a mobile laboratory, to the
permanent laboratory, or to/from a secure storage area.
Samples will be properly packaged for shipment and dispatched to the appropriate laboratory for
analysis, with a separate signed custody record enclosed in each sample container. Shipping
containers will be locked and secured with strapping tape and EPA custody seals for shipment to the
laboratory. The preferred procedure includes use of a custody seal attached to the front right and back
left of the container. The custody seals are covered with clear plastic tape. The container is strapped
shut with strapping tape in at least two locations.
All shipments will be accompanied by the COC record identifying the contents. The original
record will accompany the shipment, and the pink and yellow copies will be retained by the sampler
for returning to the sampling office.
If the samples are sent by common carrier, a bill of lading should be used. Receipts of bills of
lading will be retained as part of the permanent documentation. If sent by mail, the package will be
registered with return receipt requested. Commercial carriers are not required to sign off on the
custody form as long as the custody forms are sealed inside the sample cooler and the custody seals
remain intact.
The contractor's chemist must be notified prior to any sample collection activity. This person will
be the primary line of communication between the project site and the laboratory.
The designated laboratory sample receipt clerk is authorized to accept samples and is charged with
the responsibility for proper completion of the required sample receipt documentation. As required,
analysts are assigned to assist the sample receipt clerk in sample log-in procedures. In all cases, COC
and analytical request documents become part of the permanent file relative to the samples collected.
Those files are retained indefinitely in the laboratory's facility.
All samples in storage at the laboratory are retained in the custody of the designated sample
custodian until released as required for analytical work. A record of the custody change is made by
the analyst and checked by the sample custodian at the time the sample is taken from the cold storage.
Internal custody files are retained indefinitely in laboratory files.
After analysis is complete on a sample set, the samples or sample processing products will be held
for 30 days. The laboratory is responsible for disposing the samples, and it must be accomplished in
complete accordance with all regulations governing such activities.
All samples, including those collected with direct reading instruments, will be given a unique
sample identification number that identifies the type of sampling medium, the date collected, and the
sample type (regular, blank, collocated). This information will facilitate manipulation of the data.
Each sample number will have five distinct parts. An example is shown below.
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LFSG-01-101501-R-001
The first part of the sample number designates the sample type:
• LFSG indicates landfill soil gas;
• NSG indicates native soil gas;
• PVG indicates passive vent gas;
• EVG indicates extractive vent gas;
• AA1 indicates ambient air indoor;
• AAO indicates ambient air outdoor;
• OC indicates other condensate sample type;
• OL indicates other liquid sample type, groundwater, leachate, etc.; and
• OS indicates other soil type, split barrel.
The second part designates the sample media:
• 00 indicates Tedlar bag sample,
• 01 indicates Summa canister sample,
• 02 indicates direct-read gas analysis,
• 04 indicates fixed gas (CH4, O2, N2, CO2) analysis, and
• 05 indicates soil sample to be analyzed for physical properties.
The next six numbers represent the date the sample was collected (MMDDYY). The next letter
indicates the sample type: R for Regular, D for duplicate, C for Collocated or B for Blank. The last
three digits are a sequential number unique for each site, starting at 001 and continuing until the
sampling is complete.
B.4 Analytical Methods
The analytical methods for this project are divided into on-site analysis—organic vapor, fixed
gases (oxygen, nitrogen, methane, carbon dioxide), and flow rate measurements—and off-site
analyses (VOC canisters and physical properties). The analytical methods to be used in this project
include:
Compound Method
Gaseous Organic COPC TO-15 per EPA/600/R-96/033, March 1996
Methane TO-15 per EPA/600/R-96/033, March 1996
Gaseous NMOC GC/FID per EPA/600-R-98/16
Fixed Gases (CO2, CH4, N2, O2) FRM 3C
Soil Moisture ASTM D2216
Bulk Density ASTM D1587
Particle Density ASTM D854
Particle Size ASTM D422
Aqueous Liquids SW846 Method 8260
SW846 Method 8270
LFG Pressure FRM 2E
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Acceptance criteria is established by data generated from a specific method and instrument, and
will be laboratory specific. Procedures (laboratory SOPs or published methods) will include specific
information on tuning criteria, calibration procedures, and acceptance criteria for QC check standards.
The specific information on laboratory analysis will be included in the site-specific QAPPs.
B.4.1 On-site Analyses
The Agilent 6890 gas chromatograph and 5973N mass spectrometer (GC/MS) will be used to
perform on-site analysis of gas samples. The target compounds are site specific but inclusive of the
COPCs identified in Table A-3.
Organic vapor samples will be analyzed by trapping and subsequent thermal desorption of aliquots
via an OI analytical 4560 sample concentrator followed by GC/MS analysis. The ChemStation data
system will be used to evaluate and process the data. Table B-2 lists the targeted Agilent GC/MS and
the OI Analytical 4560 Sample Concentrator operating conditions. Once the trap is cooled, an aliquot
of sample (250 to 1000 mL) will be drawn onto the sorbent trap along with 25 nL of the internal
standard. The internal standard is a mixture of bromochloromethane, chlorobenzene-d5 and 1,4-
diflorobenzene at 10 ppbv in accordance with Method TO-15. The sample will be inj ected by thermal
desorption onto the column head of the GC/MS for subsequent analysis. The GC is temperature
programmed to separate the VOCs that will be detected by the MS detector. VOCs in the sample will
be identified by comparing their retention times and mass spectra to those of an analytical standard
and a reference mass spectral database, the National Institute of Standards and Technology (NIST)
library.
The fixed gases of methane, oxygen, nitrogen, and carbon dioxide will be analyzed using the
micro gas chromatograph (Model M200H MGC). The M200H MGC will be set up on site. The site-
specific QAPP will define the setup procedures that will be used by EPA-Laboratory. Soil gas
samples will be collected and brought to the M200H MGC location for analysis. The M200H MGC
will be operated in accordance with the manufacturer's operating manual.
The M200H MGC is a dual capillary column (A and B) and micro-chip thermal conductivity
detector (|j,TCDs) analytical instrument. An internal sampling pump pulls a vapor-phase sample
through a fixed sampling loop for a programmed period of time. Injection valves are activated, and
a sample aliquot is simultaneously injected onto both capillary columns.
Once injected into the MGC system, the sample components are separated by the capillary
columns into discrete peaks. The peaks are detected by the (jTCDs, and the results are electronically
stored by the EZChrom 200 data system. The dual column and dual |jTCD system allows independent
detection and identification of compounds. The results from column A are reported for nitrogen and
oxygen. The results from column B are reported for carbon dioxide and methane.
The EZChrom 200 data system controls all operations for the M200H MGC. The identification
and quantitation of compound peaks are conducted by comparing the sample peak responses and
retention times with those of standards stored in the EZChrom 200 method calibrations. Both single-
point and multipoint calibrations can be used. The gas samples will be analyzed using a multipoint
calibration for CH4, O2, andN2 (the primary target compounds), and a single-point calibration for CO2
(the secondary target compound) with an additional check standard to verify results.
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Table B-2. Targeted Instrument Conditions for Analysis of VOCs.
Agilent GC/MS
Column
lead Pressure
"low rate
Split Ratio
GC Temperature
njector Temperature
Vlass Spectrometer
Source Temperature
Rtx-Volatiles, 0.18 mm ID x 20 m, 2.0 ^m df
16.82psi
helium at 0.8 mL/min
40:1
35°C(holdl.Omin)
15 °Cperminto 190 °C
10 °C per min to 200 °C (hold 5.0 min)
180 °C
Electron impact ionization at a nominal electron energy
of 70 electron volts, scanning from 36 to 260 amu at
one scan/s
230 °C
QI Analytical 4560 Sample Concentrator
'urge Gas
7low Rate
'urge3
Sample Vacuum Flow
Valve Temperature
Transfer Line Temperature
Adsorption Temperature
Desorb Temperature
3ake
Water Management Heat
During Purge
During Desorb
During Bake
helium
40 mL/(min)
±12minat20°C
50 mL/min
150 °C
150 °C
Ambient (27 °C)
4minatl90°C
8 min at 200 °C
ON
100 °C
o°c
240 °C
1 Total purge time varies depending on the total sample volume.
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Two landfill systems will be monitored for flow rate: the extractive system vents and passive
landfill gas vents. The flow rate from the extractive system will be measured using a standard pitot
tube placed at the centroid of the header pipe or from an in-line orifice plate. The duct temperature
will also be measured. The delta pressure inside the pipe, static pressure of the pipe, gas temperature,
gas molecular weight, and moisture content, and pipe cross-sectional area will be used to calculate
a volumetric flow rate. The equations used to calculate the volumetric flow rate are shown below.
To help minimize any effect caused by disturbance of the pitot tube itself, a C-inch-diameter standard
pitot will be used.
Pd = Pa + Ps (1)
Vs = ^(Td)(^P] I (MW}(Pd) (2)
a = (^)G4)(3600) (3)
Qs = (a)(528°R)/ Wy29.92) (4)
Where: Pd = absolute duct pressure (inches Hg),
Pa = ambient pressure (inches Hg),
Ps = duct static pressure (inches Hg),
Vs = vapor recovery well velocity (feet per second),
Td = duct temperature (degrees Rankine),
AP = differential pressure across the pipe (inches H2O),
MW= average gas molecular weight (pounds per pound-mole),
Qa = actual flow rate (cubic feet per hour),
A = cross-sectional area of duct (square feet),
Q, = standard flow rate (SCFH),
528°R = standard temperature in degrees Rankine (68 °F), and
29.92 in. Hg = standard pressure.
The LFG molecular weight will be determined from results of canister analysis using EPA Method
3 procedures. The moisture content will either be estimated on the basis of duct temperature and
adiabatic saturation tables, measured directly using EPA Method 4, or taken from plant measurements.
Flow rate measurements from the LFG passive vents will be performed using a vane anemometer
or portable turbine meter (EPA Method 2D). These devices provide a measure of linear velocity and
are very adapted to measuring ducts and vents. The velocity can then be converted to volumetric flow
using the vent cross-sectional area. Gas temperature and barometric pressure will be measured and
used to calculate a standard volumetric flow.
Organic vapor analyzers (OVA) will be used on site to "sniff out areas of high methane and
NMOC concentrations. These instruments use FIDs or PIDs to measure methane and non-methane
hydrocarbon concentrations. These instruments will be used to identify locations where the LFG
escaping from the landfill has the highest NMOC concentration. The instruments will be calibrated
daily during the project using methane or ethane (10,000 ppmv) in air standards traceable to NIST
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standards. The OVA's will also be checked using a zero point—ultra high purity-air (UHP-air)—and
low range (100 ppmv) calibration gas.
B. 4.2 Off-site Analyses
Bulk density is the ratio of the mass of the dry solids to the bulk volume of the sample. The bulk
volume includes the volume of the solids, pores, and any liquid that may be present. For lithified
geologic materials (rocks, stones, gravel), the bulk density for a given sample is a fixed value. For
unconsolidated sediments, the bulk density will vary as a function of grain packing. If expandable
clays are present, the bulk density will vary as a function of moisture content. For this project, bulk
density will be determined using ASTM method D854. The mass of the samples is calculated by
difference using a top-loading balance. The dimensions of the specimen (cube or cylinder) are
measured using a ruler having a precision of ±1 mm. The bulk density is calculated by dividing the
mass by the volume (grams per cubic meter).
For particles less than 4.75 mm in diameter, particle density is determined by measuring the mass
of liquid required to fill a closed container of known volume containing a known mass of solids. The
volume of the liquid is calculated from the mass of the liquid and the known density of the liquid at
the temperature at which the measurements are made. The volume of the solids is the difference
between the volume of the container and the volume of the liquid. Particle density is the mass of the
solids divided by the volume of the solids. In ASTM Method D 854, specific gravity is defined as "the
ratio of the weight in air of a given volume of a material at a stated temperature to the weight in air
of an equal volume of distilled water at a stated temperature." If specific gravity rather than density
is desired, then the density of the solids at the stated temperature is divided by the density of water
at a stated temperature.
The water content or moisture content of the soil samples will be determined using ATSM Method
D 2216. In this method, a measured mass of soil is dried in an oven at 110 ±5 °C until the sample
reaches a constant mass. If performed on site, a microwave oven may be used to dry the soil samples.
The water content, expressed as a percentage, is then calculated as the ratio of the mass of water
present to the mass of soil, multiplied by 100.
The particle size distribution of the soil samples will be determined using ASTM D422-63, which
is performed in two steps. The first step, for particulates above 75 |j,m, (retained on a Number 200
sieve) uses a number of sieves of various sizes to achieve fractionation down to 75 |j,m (Number 200
sieve). In the second step, the size distribution of the material that passes the Number 200 sieve (i.e.,
less than 75 |j,m) will be determined by using a sedimentation process and a hydrometer.
As specified in the sampling strategy, some organic vapor samples will be sent to an off-site
laboratory. The VOCs collected will be analyzed using a GC equipped with dual columns and
multiple detectors. The detectors include a FID, a PID, and an ELCD. Samples will also be analyzed
using GC/MS to confirm compound identity and help identify compounds not identified by other
methods. Fixed gas (i.e., N2, O2, CO2, and CH4) analyses will also be performed off site using a
thermal conductivity detector (TCD). Calibration information is presented in Section B.7.
The canisters will be shipped to the site-specific laboratory for analysis. On arrival, the canister
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COC forms will be reviewed for completeness, and the final field pressures will be checked to verify
that the canisters did not leak during transit. Canisters determined to have leaked will be voided and
not analyzed. Following pressure checks, the canisters will be pressurized with UHP-grade helium
to both dilute the sample and facilitate its removal from the canister. Helium will be used because
UHP-grade nitrogen or air would normally interfere with the fixed-gas analysis.
The speciated VOC analysis samples will use Method TO-15. EPA method TO-15 provides
techniques for the analysis of airborne VOCs collected as whole air or LFG samples in stainless steel
canisters. Up to 0.5 L of gas is withdrawn from the canister through a mass flow controller and is
either cryofocused via liquid argon or concentrated using a multi-sorbent bed. The focused sample
is then flash heated through a hydrophobic drying system which removes water from the sample
stream prior to analysis by full scan GC/MS. For low level analysis, a cryogenic valve is employed
to cold trap the gases onto the GC column.
Compounds are qualitatively identified based on retention time and by comparing background-
subtracted sample spectra to the reference library spectra. An analyte is qualitatively identified when
the following two criteria are met:
• The relative retention time (RRT) for the analyte must be within ±0.06 RRT units of the RRT
of the analyte in the daily continuing calibration check. When high moisture in a sample causes
a retention time shift, an exception is taken, providing the shift is consistent based on the
internal standards;
• Ions present in the standard spectrum greater that 10 percent of the most abundant ion must be
present. Also, the relative intensity of the ions greater than 10 percent, must be ± 20 percent
of the intensity in the standard spectrum.
The ion intensity test is performed by the GC/MS software. Ions that do not meet the intensity
criteria are flagged in the raw data. Failure to meet the intensity criteria my be indicative of matrix
interference or low signal to noise (i.e., low concentration).
Quantitation is based on the integrated abundance of the primary ion for each analyte. If the
response for any quantitation ion exceeds the initial calibration range of the GC/MS system, the
sample is diluted and reanalyzed.
When interference with the primary quantitation ion occurs, quantitation on the secondary ion is
carried out after a new response factor (using the secondary ion) is generated from the calibration.
Therefore, the same ion used to establish the response factor is used to quantify target analytes in the
sample. This is noted in the laboratory narrative included in the report. The criterion for using the
secondary ion for quantitation is a difference in the reported result of 50 percent or more.
Canisters are connected to the inlet of the focusing unit with 1A in. stainless steel fittings, and
connections are leak checked by monitoring the flow on the controller. As vacuum is achieved, the
flow will drop to less than 5 ml/min. After leak checking is complete, the valve on the canister is
opened and flow allowed to equilibrate. The equilibration period also allows for sweeping of the line
and trap. During this time, a 1-cc gas sample valve injection of internal standard/surrogate standards
is made.
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Sampling is initiated by rotating the port valve into the sample position. Air from the canister flow
into the focusing trap. Sampling continues until the desire volume of air has been withdrawn.
Following the sampling period, the port valve is rotated into the back flush position, and the trap
heater is turned ON. Contents of the trap are then swept by carrier gas into the drier. Following this,
the drier is flash heated and the contents back flushed into the GC/MS. For low level analysis, the
gases are cold-trapped on to the GC column using a cryogenic valve. A 4 to 5 min bake cycle is then
used to clean the system for the next sample. The bake cycle eliminates sample carry over by sweeping
both the heated trap and heated drier to vent.
VOC samples collected in Summa polished stainless steel canisters are subject to a 7-day hold
time. The 7-day analytical hold time is not meant to be a statement of compound stability or sample
integrity. All compounds on the target analyte list have been studied for compound stability in Summa
canisters and found to be stable up to 30 days (there have been very limited studies of stability beyond
30 days).
The identification of peaks will be based on normalized retention times, detector responses, and
individual compound response from the daily calibration standard in accordance with Method TO-15.
The retention time of each peak on the FID will be calculated relative to the retention time (RRT) of
toluene. The PID data will then be scanned for any peaks that matched the FID retention times. The
corresponding PID/FID response ratio will then be compared with the sample's PID/FID response for
toluene to generate a toluene-normalized response (TNR) factor. Different compound classes and
individual compounds produce characteristic TNRs. The RRT and TNR data will be compared with
the compound database parameters as well as the daily analysis of calibration standard for potential
matches. The potential matches will be reviewed and validated by experienced personnel (both at the
performing laboratory and by the contractor's chemist) to ensure data quality. During this program,
the chromatograms will be validated for the major compounds (i.e., those contained in the calibration
standard) found in the chromatogram followed by evaluation of the chromatograms for compounds
not calibrated. The quantitation of the major compounds will be based on individual response factors,
which will be calculated daily by analyzing either a low-level standard (cryogenic trapping technique)
or a higher-level standard (fixed loop method). The remaining compounds will be quantitated on the
basis of a hexane response. The identification will be based on a library search. The lessons learned
project summary will note whenever compounds not on the target list are identified, but there will be
no attempt to quantify the concentrated by rerunning the samples with a different set of calibration
curves.
B.5 Quality Control
The overall QA objective is to provide defensible data of known quality meeting QA objectives.
To that end, procedures are developed and implemented for field sampling, COC, laboratory analysis,
and reporting that will provide results which are legally defensible in a court of law. Specific
procedures for sampling, COC, instrument calibration, laboratory analysis, data reporting, audits,
preventive maintenance of field equipment, and corrective action are described in Section B6 of this
QAPP.
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Each laboratory participating in this project will have established a QA program with the
objective of providing sound analytical chemical or physical measurements. This laboratory-specific
program will incorporate the QC procedures, any necessary corrective actions, and all documentation
required during data collection, as well as the QA measures performed by the laboratory's manage-
ment to ensure acceptable data production. The contractor's Q A officer will verify that the laboratory
has a written QA plan and that the laboratory has an organizational structure committed to
• Maintaining data integrity, validity, and usability;
• Ensuring that analytical measurement systems are maintained;
• Detecting problems through data assessment and established corrective action procedures that
keep the analytical process reliable; and
• Documenting all aspects of the measurement process to provide data that are technically sound
and defensible.
The EPA laboratory team manager will select the laboratories using their existing contractor
selection processes. The purpose of this section is to address the specific objectives for accuracy,
precision, completeness, representativeness, and comparability.
Field blank, trip blank, duplicate and matrix spike, and split/collocated samples will be analyzed
to assess the quality of the data derived from the field sampling program. Field blank samples consist
of distilled water and are analyzed to check for procedural contamination at the site that may cause
sample contamination. Trip blanks consist of distilled water and or reagents. These trip blanks will
be used to assess the potential for sample contamination during sample shipment and storage.
Duplicate samples will be analyzed to check for sampling and analytical reproducibility. Matrix
spikes provide information about the effect of the sample matrix on the digestion and measurement
methodology. The matrix spike will include the COPC-TALs identified in Table A-l. Laboratory
spiking levels will be at the same concentration as the field sample. All matrix spikes will be
performed in duplicate and will hereinafter be referred to as matrix spike/matrix spike duplicate
(MS/MSD) samples. MS/MSDs will be collected for every 20 or fewer investigative samples. Soil
and gas MS/MSD samples require no extra volume for VOAs or extractable organics. Split/collocated
samples will be collected for five percent of the gaseous samples. These collected samples will be
analyzed offsite as a check on the on-site laboratory efforts.
The number of duplicate, field blank, equipment blank, trip blank, and split samples to be
collected are listed in Table B-3.
The level of QC effort for testing on the organics target analyte list (volatiles and semi-volatiles)
will be equivalent to the protocols of "Laboratory Data Validation Functional Guidelines for Eval-
uating Organic/Pesticides and PCBs Analyses" EPA-540/R/94/090-092. The level of QC effort for
testing of methane and NMOC in air samples will conform to the protocols from the National Institute
for Occupational Safety and Health (NIOSH) "Manual of Analytical Methods," Third Edition, U.S.
Department of Health and Human Services, August 1994.
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Table B-3. Guidelines for Minimum QA/QC Samples for Field Sampling Programs.
Media
Soil,
Sediment,
Solids
Gases
Calibration/
vfeat Source
Material
Duplicates/
Replicates
5%
5%
One per 20
samples
Field
Blanks
None
One per reagent per
sampling event, per
media lot
One per reagent per
sampling event
Equipment
Blanks
None
One per
sampling event
One per
sampling event
Trip
Blanks
None
5%
None
Split
Samples
None
5%
None
MS/MSDs
None
5%
None
Note: Laboratory blanks are method-specific and are not included in this table.
The QC level of effort for the field measurement of methane and NMOCs consists of pre-
measurement calibration and a post-measurement verification using standard reference materials.
This procedure will be performed twice a day for each day of screening level analyses. The QC effort
for field measurements will include twice daily calibration of the instrument using mixtures of gas
in cylinders. The calibration gases will include UHP-air, methane, and ethane in air. Dilution probes
will be used to verify that calibration between 0 and 500 ppm is maintained. Scott Speciality Gases
or similar commercial suppliers will provide the calibration gases and a certificate of analysis will be
obtained for each lot used.
The fundamental QA objective with respect to accuracy, precision, and sensitivity of laboratory
analytical data is to achieve the QC acceptance criteria of the analytical methods being used and the
targets presented in Tables A-5, A-6, and A-7.
Laboratory results will be assessed for compliance with required precision, accuracy, and
sensitivity as described below.
Precision
Precision of laboratory analysis will be assessed by comparing the analytical results between
MS/MSD for organic analysis. The relative percent difference (RPD) will be calculated for each pair
of duplicate analysis using the equation
RPD =
S-D
D)I2)
x 100
Where: S = First sample value (original or MS value) and
D = Second sample value (duplicate or MSD value).
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Field precision is assessed through the collection and measurement of field duplicates at a rate of
1 duplicate per 20 analytical samples.
Accuracy
Accuracy of laboratory results will be assessed for compliance with the established QC criteria
using the analytical results of method blanks, reagent/preparation blank, MS/MSD samples and field
blanks. Blank contamination is an indicator of systemic contamination, and it may alter the detection
limits that can be achieved by the analytical methods. The analytical results of the various blanks will
not be used to alter the quantitative results. The percent recovery (%R) of matrix spike samples will
be calculated using the equation
A- B
%R = x 100
Where: A = The analyte concentration determined experimentally from the spiked sample,
B = The background level determined by a separate analysis of the unspiked sample, and
C = The amount of the spike added.
Accuracy in the field is assessed through the use of field and trip blanks and through the adherence
to all sample handling, preservation, and holding times. Onsite analyses will be validated via
collocated/split samples being sent to an offsite analytical laboratory at a rate of one collocated sample
per 20 samples analyzed onsite.
Sensitivity
Achieving method detection limits depends on instrumental sensitivity and matrix effects.
Therefore, it is important to monitor the instrumental sensitivity to ensure data quality through
constant instrument performance. The instrumental sensitivity will be monitored through the analysis
of method blank, calibration check sample, and laboratory control samples, and so forth.
The usefulness of sampling and analysis data also depends on whether they meet the criteria for
completeness, representativeness, and comparability. The QA objectives are that all measurements
be representative of the medium or operation being tested and that all data resulting from sampling
and analysis be comparable. Wherever possible, sampling and analysis by reference methods and
standard reporting units specified by the analytical method will be used to aid in ensuring that QA
objectives are met.
COMPLETENESS is a measure of the amount of valid data obtained from a measurement system
compared to the amount that was expected to be obtained under normal conditions. It is expected that
the analytical laboratory will provide data meeting QC acceptance criteria of 80 percent or more for
all samples tested. Following completion of the analytical testing, the percent completeness will be
calculated by the equation
(number of valid data)
Completeness (%): = 7 ^r x 100
f number of samples collected j
V for each parameter analyzed;
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Field completeness is a measure of the amount of valid measurements obtained from all the
measurements taken in the proj ect. Field completeness for this proj ect will be greater than 80 percent.
REPRESENTATIVENESS expresses the degree to which data accurately and precisely represent
a characteristic of a population, parameter variations at a sampling point, a process condition, or an
environmental condition. Representativeness is a qualitative parameter that depends on the proper
design of the sampling program and proper laboratory protocol. The sampling network will be
designed to provide data representative of site conditions. During development of the sampling
network, consideration will be given to past waste disposal practices, existing analytical data, physical
setting and processes, and constraints inherent to the Superfund program. The rationale of the
sampling network is discussed in detail in Section B.I. Representativeness will be satisfied by
ensuring that proper sampling technique are used, proper analytical procedure are followed, and
holding times of the samples are not exceeded in the laboratory. Representativeness depends on the
proper design of the sampling program and will be satisfied by ensuring that the site-specific QAPP
is followed and that proper sampling techniques are used. Representativeness is determined through
completion of the DQO Process presented in Section A7. Representativeness will be assessed by the
analysis of duplicated samples, and Table A-4 indicates how many duplicate samples are to be
evaluated. The duplicate sample locations will be identified in the site-specific QAPPS.
COMPARABILITY expresses the confidence with which one data set can be compared with
another. The extent to which existing and planned analytical data will be comparable depends on the
similarity of sampling and analytical methods. The procedures used to obtain the planned analytical
data are expected to provide comparable data. These new analytical data, however, may not be
directly comparable to existing data because of a difference in procedures and QA objectives.
Comparability depends on the proper design of the sampling program and will be satisfied by ensuring
that the site-specific QAPP is followed and that proper sampling techniques are used.
Field data will be assessed by the QC officer. The QC officer will review the field results for
compliance with the established QC criteria. Accuracy of the field measurements will be assessed
using daily instrument calibration, calibration check, and analysis of blanks. Precision will be
assessed on the basis of reproducibility by obtaining multiple readings of a single sample.
B.6 Instrument/Equipment Testing, Inspection and Maintenance Requirements
The nature of the project activities requires periodic inspections to ensure that they are being
completed in accordance with applicable regulations and project/contract requirements. Inspections
are typically completed by the QA officer and other designated project personnel. The nature and
frequency of inspections is a function of project activities; preparation, initial, follow-up, and final
inspections are typically conducted. Results of inspections will be summarized, and inspection reports
will be provided to the TOM on a regular basis. Recommendations for correcting deficiencies
identified during inspections are developed by the Project Manager and discussed with the TOM.
Equipment used in the field is calibrated by the manufacturer or calibration is checked in-house
prior to use. Calibration of the equipment is verified in accordance with the manufacturer recom-
mendations and whenever repairs are made after a malfunction has been noted. The Field Team
leader maintains a list of certificates for each piece of equipment being used. Maintenance records
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of equipment adjustments and repairs are kept in equipment maintenance logs. These records include
the date and description of the maintenance performed.
A preparatory inspection will be performed, at the request of the TOM, prior to initiation of field
activities. The preparatory inspections will include:
• Review of task order requirements,
• Review and approval of plans and other submittals,
• Verification of control testing procedures and schedules,
• Examination of all materials and equipment to ensure that approved submittals conform to
design specifications and are promptly stored,
• Review of activity hazard assessments to ensure appropriate levels of health and safety,
• Verification of construction tolerances and workmanship standards,
• Verification of adequacy of any required preliminary activities including an inspection of the
work area,
• Discussion of QC procedures that required levels of workmanship and inspection criteria on
site with project staff concentrating on the work plan and impending activities,
• Review of preparatory inspection notes and verification of the status of preparatory activities,
• Verification of procedures and schedules for control testing,
• Evaluation of the results of any control testing,
• Examination of the quality of the workmanship of construction (where appropriate),
• Review of the safety procedures in accordance with the site Safety and Health Plan including
equipment required and upgrade/downgrade criteria, and
• Review of project submittals and proposed activities for omissions or dimensional errors.
Follow-up/Final Inspections
Follow-up inspections will be performed at the request of the TOM to ensure continued
compliance with the project contract requirements. These inspections encompass:
• Verifying control test results,
• Examining the quality of workmanship of construction (where appropriate),
• Reviewing project submittals relating to project closeout.
Any nonconforming items will be documented in a nonconformance report. Figure B-3 presents
an example nonconformance report. Corrective actions to noted deficiencies will be required unless
a variance from the specifications is approved by the TOM.
Field equipment for a site will be identified in the site-specific QAPP. Specific preventive
maintenance procedures to be followed for field equipment are those recommended by the
manufacturer.
Field instruments will be checked and calibrated in the warehouse before they are shipped or
carried to the field. These instruments will be checked and calibrated daily before use. Additionally,
calibration checks will be performed after every 20 samples and will be documented on the Field
Meter/Calibration Log Sheets.
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if ft '}
Nonconformance Report
Date Project
Project
Description of Nonconformance:
Inspector Date
Corrective Action Required:
Prepared by:
Name:
To be verified by:
Name:
Date
Date
Corrective Action Executed:
Executed by:
Name:
Inspected by:
Name:
Approved by:
Name:
Follow up
Name:
Date
Date
Date
Date
Figure B-3. Example Nonconformance Report.
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Critical spare parts such as tape, papers, diaphragms, and batteries will be kept on the site to
minimize instrument downtime. Backup instruments and equipment will be available on site or within
one-day shipment to avoid delays in the field schedule. Table B-4 presents routine preventive
maintenance schedules for common field monitoring equipment.
Table B-4. Routine Preventative Maintenance Procedures and
Schedules for Field Monitoring Equipment.
Instrument
Combustible Gas and O2
Alarm
Photoionization Detector
Flame lonization
Detector
Water Level Indicator
Activity
Charge battery pack
Clean sample inlet filter
Clean probe
Clean lamp
Check for proper operation and response
Recharge battery pack
Recharge hydrogen tank with zero hydrogen
to 1500 - 2000 psi
Check for proper operation and response
Replace batteries
Keep tape and probe free from contamination
Frequency
As needed
Each time recharged
Each use
As needed
Daily
After each use
As needed
Daily
As needed
Before and after each use
A routine preventive maintenance program is conducted by the analytical laboratory as part of a
QA/QC program to minimize the occurrence of instrument failure and other system malfunctions.
The analytical laboratory is expected to have an internal group or equipment manufacturer's service
contract to perform routine scheduled maintenance and to repair or to coordinate with the vendor for
the repair of all instruments. All laboratory instruments will be maintained in accordance with
manufacturer's specifications and the requirements of the specific method employed. This
maintenance must be carried out on a regular scheduled basis and be documented in the laboratory
instrument service logbook for each instrument. Emergency repair or scheduled manufacturer's
maintenance will be provided under a repair and maintenance contract with qualified representatives.
Project-specific equipment lists will be included in the site-specific QAPP.
B.7 Instrument Calibration and Frequency
This section describes procedures for maintaining the accuracy of all the instruments and
measuring equipment that will be used for conducting field tests and laboratory analyses. These
instruments and equipment should be calibrated prior to each use or on a scheduled periodic basis.
The Field Team Leader is responsible for assuring that calibrations are current and documented.
Whenever possible, widely accepted calibration methods, such as those published by ASTM or
U. S. EPA or those provided by manufacturers, will be adopted for both field and laboratory analytical
instrumentation. At a minimum, calibration methods will take into consideration the type of equip-
ment to be calibrated, reference equipment, and standards to be used. Equipment will be calibrated
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using reference equipment and standards having known relationship to nationally recognized
standards (e.g., NIST) or accepted values of natural physical constants. If national standards do not
exist, the basis for the reference standard or calibration will be documented.
Reference equipment will be used only for calibration and will be stored separately from
functioning, measuring, and testing equipment to prevent inadvertent use. In general, reference
equipment will be at least 4 to 10 times as accurate as the equipment being calibrated.
All continuing calibrations are performed in the field prior to instrument use. Every calibration
is recorded in the maintenance logbook for each instrument. QC check standards from separate
sources will be used to check initial calibration and acceptance and rejection criteria. When the
difference between the continuing calibrations and the QC check standards exceeds plus or minus 20
percent, use of the instrument will be suspended until corrective actions are taken or until it is
determined that a greater variance will be allowed. The acceptance/rejection criteria can only be
revised by approval of the laboratory manger and the TOM. Vapor meters will be calibrated daily with
one span gas. All analytical instrumentation will utilize continuing calibration standards in addition
to the initial calibration curve. These will be run at varying concentrations including low, mid, and
high range to ensure continuation of the curve.
Calibration procedures and frequency specified by the method will be used by the field analytical
laboratory. When the field laboratory is used only for screening purposes, however, a less-stringent
approach to calibration can be used—for example, using three concentration levels instead of five.
The option will be specified and documented in the project-specific QAPP.
All certified gas standards will be provided by Scott Specialty Gases, Inc., or a similar supplier.
The VOC standard will contain at least 20 COPC-TAL compounds each at approximately 1 ppmv in
helium. Helium is used to avoid problems associated with conducting the fixed gas (CO2, N2, O2)
analyses. The initial calibration will be performed by varying the volume of the standard; volumes
of 1, 5, 25, 50, and 100 mL of the 1 ppmv standard result in a calibration curve of 1, 5, 25, 50, and
100 nL, respectively. Daily calibration check standards will be obtained by analyzing the 25-nL
standard. The initial calibration response factor report and the continuing calibration reports will be
provided with the laboratory report.
Stock standards should be purchased in a high pressure cylinder blend that is designed to
minimize vapor phase interactions and maximize long-term stability. The standards would be blended
into the working range by taking known aliquots using density-based calculations. Density-based
calculations are used to determine the prescribed amounts and final concentrations.
To prepare internal standards (IS) the prescribed amounts of neat material and 50 |jL of water are
spiked into a Tedlar bag containing 10.0 L of nitrogen. The contents of the Tedlar bag are transferred
into an evacuated 6 L Summa canister, pressurized, and diluted. A 1.0 mL of the internal standard
blend is injected into the canister interface as each standard, blank, and sample is being loaded. The
final concentration is 25 ppbv for each of the following:
bromochloromethane
chlorobenzene-dj
1,4 -difluorobenzene
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The internal standards' retention times for the blanks and samples must be within ±0.5 min (30 s)
of the retention times in the continuing calibration check. In addition, the IS area must be within ±40
percent of the continuous calibration verification's (CCV's) IS area for the blanks and samples. A
warning limit of ±30 percent is used to investigate possible mis-injection of the IS. If the ISs for the
blank do not pass the acceptance criteria, the system is inspected and the blank reanalyzed. Analyses
are discontinued until the blank meets the IS criteria.
If the ISs in a sample do not pass the acceptance criteria, the sample must be reanalyzed unless
obvious matrix interference is documented. If the ISs are within limits in the re-analysis, the second
analysis will be reported. If the ISs are out-of-limits a second time, then the data is reported from the
first analysis and the matrix effect narrated in the laboratory narrative included with the report.
A humidified blank (less than 20% relative humidity at 25 °C) is analyzed after each CCV sample
run: (1) At the beginning of the analytical shift or sequence (when an initial calibration is not being
performed); (2) every 12 hr of analyses or every 20 samples, whichever comes first; and (3) at the end
of the analytical sequence. A blank is also analyzed in the event saturation-level concentrations are
incurred to demonstrate that contamination does not exist in the chromatographic system.
The acceptance criteria for the concentration of each target analyte in each blank must be less than
the greater of (1) the reliable detection limit (RDL) for the target analyte; (2) the method reporting
limit (MRL) when the MRL is not greater than 5% of the project and analyte specific action level, (3)
5 % of the analyte concentration detected in each associated field samples; and (4) 10% of the action
level. Environmental sample detections greater than the MRL but less than 10 times the corresponding
blank detections should be qualified. The following definitions and procedures are used to quantify
the acceptance criteria.
The RDL is the upper 95% upper confidence limit of the method detection limit (MDL). The
MDL is the minimum concentration of a substance that is significantly greater than zero (an analytical
blank) at the 99% limit of confidence and is determined using the procedure described in 40 CFR, Part
136, Appendix B.
The MRL is the threshold or censoring limit below which target analyte concentrations are
reported as " < MRL" where "MRL" is the numerical value of the method reporting limit. The MRL
is usually established by contract and is based on the laboratory's limits of identification (LOIs),
method quantitation limits (MQLs), or project-specific action levels. The MRL for undetected
analytes should not be less than the LOI or RDL and must not be greater than the action level.
The LOI is the lowest concentration of analyte that can be detected with 99% confidence; that is,
the LOI is the concentration at which the probability of a false negative is 1%. The LOI is adjusted
for method specific factors (e.g., sample size) and may be approximated as twice the detection limit.
The LOI may be set equal to about two times the MDL (e.g., if it is assumed that the standard
deviation is not strongly dependent upon concentration).
The MQL is the concentration of an analyte in a sample that is equivalent to the concentration of
the lowest initial calibration standard adjusted for method specified sample weights and volumes (e.g.,
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extraction volumes and dilutions). Typically, MQLs are equal to or greater than the lowest initial
calibration standard and are at least five times greater than the MDL. MQLs must also be less than
project-specific action levels. It is usually desirable for the MQL to be equal to some fraction of the
project's action levels (e.g., one half or one third of the action levels).
A duplicate sample analysis will be performed on 10 percent of the samples at the laboratory. The
relative percent difference between the two analyses must be less than or equal to 25 percent for all
compounds detected at greater that 5 times the detection limit. If this limit is exceeded, the sample
will be re-analyzed a third time. If the limit is exceeded again, the cause is investigated and the
system brought back to working order. If no problem is found in the system, the data will be flagged
to note the non-conforming event.
A mid-level spike (laboratory control sample using a subset of the independent source standard)
is analyzed daily prior to sample analysis. If the site specific criteria are not meet, the system is
checked and the standard re-analyzed. In the event that the criteria cannot be met, the instrument is
recalibrated.
The calibration for meta and para-xylenes will be performed using only the meta-xylene isomer
because the two isomers co-elute on the GC column and have identical ion spectra and response
factors. The IS mix will consist of bromochloromethane, 1,4-difluorobenzene and chlorobenzene-d5,
each at approximately 1 ppmv. Twenty-five mL of the internal standard mix, equivalent to a 25-nL
standard, will be added to all samples and standards. The targeted standard concentrations and
quantitation ions that will be used are listed in Table B- 5.
Mass spectrometer tuning will be performed and checked daily. Seven mL of p-bromo-
fluorobenzene (BFB) at 1 ppmv, equivalent to about 50 ng of BFB, will be analyzed to validate the
mass spectrometer tuning. The specific mass number that the instrument will be tuned to is laboratory
specific. This number will be provided in the site-specific QAPP.
VOCs in the samples will be identified and quantitated using ChemStation software. This soft-
ware uses reconstructed and extracted ion chromatograms matched with retention time windows to
identify and quantify target compounds. The report prints the identified compound, calculated
concentration, mass spectra (both raw and background subtracted), quantitation, and qualifier ion
chromatograms. The spectra of all non-target compounds with a peak area of at least 20 percent of
the nearest internal standard in the total ion chromatogram will be compared to the NIST Mass
Spectral Database. The summaries will contain the best match provided by the computer search
algorithm and an estimated amount for each tentatively identified compound. The tentatively
identified compounds produced by this automated search will be found in the library search compound
(LSC) report.
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Table B-5. Target Calibration Concentrations and Quantitation Ions for COPCs.
Compound
Working Calibration Standard
1 , 1 -Dichloroethane
1 ,2-Dichloroethane
1,1,1-Trichloroethane (methyl chloroform)
1 , 1 ,2-Trichloroethane
1,1-Dichloroethene (vinylidene chloride)
cis- 1 ,2-Dichloroethene
trans- 1,2-Dichloroethene (ethylene Bichloride)
Acylonitrite
Benzene
Carbon Terrachloride
Chlorobenzene
Chloroethane (ethyl chloride)
Chloroform
Chloromethane (methyl chloride)
Dichlorobenzene
Dichlorodifluoroethane
Ethylbenzene
Ethyl chloride
Ethylene Dibromide
Methylene Chloride
Tetrachloroethene (Perchloroethylene)
Toluene
Trichloroethene (Trichloroethylene)
Vinyl chloride
M - Xylene
o-Xylene
P-xylene
Internal Standard
Bromochloromethane
1 ,4-Difluorobenzene
Chlorobenzene -d5
Tuning Standard
4-Bromofluorobenzene
Quant. Ion
63
62
97
97
61
96
96
53
78
117
112
64
83
50
146
85
91
64
107
49
166
92
130
62
91
91
91
128
114
117
N/A
Concentration
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
1.00 ppmv
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Detection limits are determined by analyzing a low level standard (1 to 5 ng/ml). The limit of
quantitation (LOQ) for each sample analyzed via TO-15 is calculated using
LOQ= (OC](DF]
Where: LOQ = Results (parts per billion by volume in sample),
OC= parts per billion by volume on-column from the MDL
DF= Dilution factor
The target compound results will be calculated using
Where Rc = Results concentration (parts per billion by volume on-column),
Ac = Area of compound in sample,
AIS = Area of internal standard in sample,
CIS = Concentration of the internal standard (ppbv), and
ICAL-RRF = Initial calibration relative response factor.
Then
R = (RC)(DF)
Where R = Results (parts per billion by volume in sample)
DF= Dilution factor.
Dilution factor includes canister pressurization dilution and any subsequent dilution required to
ensure all results are within the instrument calibration range.
An OVA will be used to screen the landfill for methane and non-methane organic carbon vapors.
This instrument will be calibrated using methane and ethane in air standards. An initial calibration
using zero air and two upscale standards (500 to 100,000 ppmv) will be completed twice each field
day. Following this calibration, the OVA will be single-point checked daily with a mid-level (100 to
500 ppmv) methane or ethane standard as appropriate.
The following QA/QC procedures will be performed for this project.
• The Agilent GC/MS will be tuned daily for perfluorotributylamine (PFTBA) to meet
abundance criteria for p-bromofluorobenzene as listed in EPA Method 624. Tuning results will
be included in the calibration data section. The tune will be adjusted when necessary.
• Initial calibrations will be performed. All compounds must meet the acceptance criteria of
having a correlation coefficient greater than 0.95.
• Continuing calibrations will be performed. All compounds must meet the acceptance criteria
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of having a percent difference (%D) of less than or equal to ±25 percent.
• Five instrument blanks will be analyzed after the calibration standard(s) and before samples
will be analyzed. Blank analyses will be performed after samples with high VOC concen-
trations to check for carryover and to ensure that the GC/MS system was clean.
• Sample container blanks will be collected daily and analyzed for the COPC-TAL.
• Known concentrations of the gas standards will be used to generate a 2-point calibration for
nitrogen and oxygen, and a single-point calibration for carbon dioxide. A Scott Specialty Gas
standard, containing 15 percent methane, 5.01 percent oxygen, 4.99 percent nitrogen, and
49,600 ppm carbon dioxide will be used for the level 1 calibration. Ambient air, with a
concentration of 20.950 percent oxygen and 78.080 percent nitrogen (Reference: Handbook
of Chemistry and Physics) will be used for the Level 2 calibration for oxygen and nitrogen.
A Scott Specialty Gas standard containing 10,100 ppm carbon dioxide will be used as a check
standard to validate the carbon dioxide calibration. The procedure may be changed to a single-
point calibration for oxygen and nitrogen using ambient air as the standard and the 10,100 ppm
carbon dioxide standard if the oxygen and nitrogen content of all of the initial samples are very
close to the amounts found in ambient air and samples containing the most carbon dioxide had
levels relatively close to the 10,100 ppm carbon dioxide standard.
• Approximately 5 percent duplicate samples will be collected and analyzed.
• Approximately 5 percent split replicate analyses will be performed.
• Periodically throughout each sampling day (once every 20 samples at least), calibration
standards will be injected and the performance of the instrument noted. The instrument will be
recalibrated as required.
• To ensure the system is clean prior to analysis, the columns will be baked over night prior to
each day of analysis. Ambient air samples will be analyzed after each initial calibration.
Target compound results will be reported in tabular form. Analytical results will be reported in
parts per billion by volume.
The calibration package for each day of analysis will be included in an appendix to the laboratory
report. This package will include copies of the injection logbook, BFB tune, and the initial and the
continuing calibration quantitation report. The quantitation report will list the retention time,
quantitation ion, peak area, and amount in nano liter. Amounts listed on these quantitation reports
will be generated by using the linear regression plot of the initial calibration. The calibration plots
will also be included in an appendix. Quantitation reports for the blanks and samples will also be
found in an appendix. Quantitation will only be interpolated between calibration standards.
Extrapolation below or above the calibration standard will not be done. The lower calibration standard
will be at the MDL as established by the individual laboratory. The COC forms will be in an
appendix.
The following is a list of the QA/QC flags that may be used in qualifying the results:
A - Assumed volume for the method blank,
B - Concentration less than three times the reported blank result,
C - Compound calibration relative standard deviation (RSD) greater than 30 percent
(concentrations calculated by average response factor only),
D - Compound calibration check relative percent deviation greater than 25 percent,
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E - Concentration exceeded highest calibration level,
J - Below quantitation limit,
U - Not detected at or below the LOQ,
I - Concentrations are estimated due to interference, and
R - Data unusable, narrative provided in summary report.
A formal calibration program is essential for verifying that the instruments and equipment are
working properly and are capable of producing quality data.
The two basic types of calibrations are periodic and operational. Periodic calibration is usually
applied to apparatus such as thermometers, balances, ovens, and pipettes that do not directly produce
an analytical result. Periodic calibrations are performed on a specific time schedule regardless of the
frequency of use of the apparatus. Operational calibration applies to analytical instruments and
manual analyses. Operational calibrations precede each use of the instrument and are performed
during use at frequencies defined in the test method. Each participating laboratory is expected to have
a QA plan that addresses operational and periodic calibrations, maintenance, and documentation
procedures and requirements.
Bench analysts are responsible for ensuring that their analyses are performed under valid
calibrations.
• Balances
A qualified and experienced technician will examine and calibrate if needed, analytical and
top-loader balances annually. Calibration will be verified daily or before each use.
• Refrigerators and Freezers
The temperature of refrigerators and freezers used for storing samples and extracts must be
monitored daily. Nongaseous samples must be stored at 4±2 °C. Organic standards are
maintained at -10 to -20 °C. Summa cannister will be stored at ambient temperatures.
• Ovens
The temperatures of ovens used for sample analysis must be monitored daily.
• Thermometers
Thermometers must be checked upon receipt and annually thereafter against a NIST-traceable
thermometer over the range at which they are to be used. Those differing more than 2°C from
true are returned (if new) or discarded.
• Micro pipettes
Micro pipettes are used for preparing dilutions of calibration solutions and samples and for
adding reagents and spiking solutions during analysis. Micro pipettes must be calibrated upon
receipt, monthly thereafter, and after maintenance. The pipette is repaired or discarded if its
delivery volume is greater than ±5 percent of the true value.
Equipment that fails calibration or becomes inoperable during use will be removed from service,
segregated to prevent inadvertent use, and tagged to indicate it is out of calibration. Such equipment
will be repaired and recalibrated to the satisfaction of the field team supervisor, as appropriate.
Equipment that cannot be repaired must be replaced. Results of activities performed using equipment
that has failed recalibration will be evaluated by the involved QA personnel or site supervisor, as
appropriate. The results of the evaluation will be documented and appropriate personnel will be
notified. Scheduled calibration of measuring and test equipment does not relieve any personnel of the
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responsibility of using properly functioning equipment. If an equipment malfunction is suspected,
the device will be tagged and removed from service or recalibrated as needed.
Records will be prepared and maintained by the individual laboratory in accordance with its QA
plan, for each piece of calibrated measuring and test equipment and each piece of reference
equipment, to indicate that established calibration procedures have been followed. Records for
equipment used only for a specific project will be maintained in the project files.
B.8 Inspection and Acceptance Requirements for Supplies and Consumables
It is the responsibility of the equipment and supply manager to secure all the equipment, supplies,
and consumables necessary to conduct the monitoring, sampling, and analytical methods described
in Sections B. 1 through B.4. Each of the participants in this study will have a document system that
is designed to assure that equipment and supply specifications are developed in accordance with the
methods and procedures needed to meet the project objectives. The system should:
• Determine technical and quality requirements for all supplies and consumables by evaluating
task order requirements, applicable or relevant and appropriate technical requirements, contract
requirements, and other issues or documents identified.
• Determine if acceptance testing should be performed based on findings of the technical review.
• Determine acceptability of leased, rented, or purchased items based on findings of the quality
review.
• Arrange and documenting acceptance testing, if required.
• Handle any nonconforming items.
• Procure equipment, supplies, and consumables that meet established technical and quality
requirements.
• Track and verify the quality of the required equipment, supplies, and consumables.
• Maintain required documentation to ensure the quality and adequate technical performance of
all equipment, supplies, and consumables.
Prior to mobilizing, a packing list of the equipment and consumables being used at the site for
field sampling, monitoring, or on-site analysis will be sent to the QC officer for review and approval.
The list will include as appropriate:
• Size, type, and number of sample containers,
• Model number(s) of instruments being used for screening the landfill for methane and NMOC
contaminants,
• Quantities and characteristics of calibration and span gases or solutions,
• Quantities and characteristics of spiking material, and
• Log book assignments by person and serial number.
The QC officer will compare the list of equipment and consumables to those required by the
methods and the QAPP.
B.9 Indirect Measurements
Sources of previously collected data and other information must be clearly identified to establish
acceptance criteria for use of such data as well as limitations resulting from uncertainty in its quality.
Information that is nonrepresentative and possibly biased and is used uncritically may lead to
decision errors. Acquired data may include but are not limited to
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• Data from handbooks,
• Historical information,
• Computerized databases,
• Site-specific parameters, and
• Maps, drawings, photographs.
Indirect measurement data must be developed to support data QA objectives. Acceptance criteria
for each collection of data for use has been determined with respect to
• Representativeness. To be assessed qualitatively by verifying that the site-specific informa-
tion was developed in a systematic and documented manner. Comparability is being ensured
by the use of the same reporting units and normalization of the information. Comparison of
the laboratory and monitoring data generated by this project with historical data is not a
significant factor.
• Bias. To be assessed by checking the available records for statements concerning bias. For
example, if the percent recovery for matrix spike samples has been used to indicate that the
historically reported concentrations for chemicals of potential concern are biased low, the
decision to exclude a chemical from the site-specific COPC-TAL would be erroneous, and the
risk would be underestimated. Similarly, if the reported concentration data is biased high, the
decision to include a specific COPC on the TAL would be erroneous and resources spent on
unnecessary sampling and analysis would be wasted. Site-specific COPC-TAL will be estab-
lished prior to mobility for field work. Time and budget constraints will be a dominant factor
in selecting the COPC-TAL.
• Precision. To be assessed by checking the available records for statements concerning
precision. If the relative standard deviation or coefficient of variance for the historical data
used to characterize the COPC concentrations is high, the number of samples or the density of
the sample grid could be erroneous, and an inadequate number of samples would be collected.
Similarly, if the precision is low, the number of samples and the density of the sample grid
would need to be increased, and the costs for sampling and analysis would be increased
unnecessarily. The sample density will be established prior to mobility for field work. Time
and budget constraints will be the dominant factor in selecting the number of samples to be
collected and analyzed.
• Qualifiers. To be assessed by checking the available records for statements concerning the
usability and limitations of the results. Clearly, any data that has been previously rejected will
not be used. Absent clear indications that the data quality is questionable or must be restricted,
the data will be used as if it is correct and the best available.
• Summarization. The data will be summarized and normalized to the extent reasonable and
possible. Normalization will be achieved by using common units of measure. The data quality
obj ective achieved would be compared to the obj ectives for accuracy, precision, completeness,
and detection limits specified herein.
Use of indirect data will be limited when found to not meet acceptance criteria. The impact of
results on DQOs with respect to the environmental decision will be reviewed to determine re-
quirements for qualification or replacement of results.
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B.10 Data Management
This section describes the procedures and criteria for recording, validating, and reporting data.
Several types of data will be generated and reported during this program. As part of the QC effort,
the field team leader and the QC officer will verify that persons responsible for data entry (electronic
and manual) are being careful. Periodic observations will be made to assure that accurate data re-
cording is achieved. The electronic data will be in the form of digital data files created by the data
acquisition system. Backup copies of the electronic files will be created daily. The integrity of the
raw data files is to be maintained, so all data manipulation will be performed on a copy of the raw
data file.
Much of the data will be generated on site; therefore, these parameters will be recorded and
validated on a semi-continuous basis during the monitoring program. This activity will consist of
ensuring that data calibrations are kept current, that data are continuously recorded in the proper
format, and that any problems are properly and expeditiously recorded. An on-site computer will be
used to help process and archive the data produced during the field sampling effort. The site-specific
QAPP will identify the type of computer and software needed to interface with the instrumentation
being used in the field. Data loggers will be used to the extent possible in order to minimize data
entry errors. This will help ensure that all the samples scheduled are collected and that the data
collected during this program is properly handled.
Following field collection of data, all electronic data collected will be stored in a central project
file server for security and retrieval in its original form (as collected) and in its modified form
(following data validation and reevaluation). Those items not in electronic form will be filed in a
central project filing system at the contractor's project office and in accordance with the contract
agreement between the EPA and contractor that authorizes the work.
Analytical Data Handling
Specific data recording and validation resulting from analytical procedures as described in
Sections B.2 through B.4 will be recorded by the generating laboratory and will be included with the
laboratory report and records being stored by the contractor. These records will be available upon
request of the TOM for a period of 3 years.
On-Site Data Handling
The data generated while on site will all be real-time or semi real-time; care must be exercised to
ensure that all the data are being properly recorded and that accurate records are kept of all on-site
activities. All on-site data will be kept on formatted data sheets and in bound logbooks. Where
possible, instrument data loggers will be used that can then be downloaded through an RS-232 port
directly into the on-site computer system. Logbook entries will be made in ink, and separate
notebooks or notebook sections will be set aside for the various parameters. All supporting data
generated will be well documented regarding where the data were collected, the landfill section, grid
number or vent identification number or identifier, time and date the data were collected, and any
other supporting documentation. Microsoft Office software is the platform of choice for recording and
archiving electronic field data. The field team leader and the QC officer will verify that persons
responsible for data entry are being careful. Periodic observations will be made to assure that accurate
data recording is being achieved. The field team leader or the QC officer will determine twice a day
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if corrective actions are required.
The on-site data validation procedures focus mainly on ensuring good accurate data collection
and identification. In addition, instrument calibration will be regularly checked and compared with
previous calibration data to determine if there is any change or drift in these data. Duplicate sample
measurements will be evaluated to ensure that the instruments are operating properly and repro-
ducibly. If discrepancies in instrument operation are noted, the data will be flagged accordingly.
ELEMENT C. ASSESSMENT AND OVERSIGHT
The purpose of assessment is to ensure that the QAPP is implemented as prescribed. This section
addresses tools and procedures for assessing the effectiveness of implementation of the project and
associated QA/QC.
C.I Assessments and Response Actions
Performance and system audits of both field and laboratory activities may be conducted to verify
that sampling and analysis are performed in accordance with the procedures established in the QAPP.
The audits of field and laboratory activities include two separate independent parts: internal and
external audits.
Internal audits of field activities (sampling and measurements) will be conducted by the
contractor's QA officer. The audits will include examination of field sampling records, field
instrument operating records, sample collection, handling and packaging in compliance with the
established procedures, maintenance of QA procedures, COC, and so forth. These audits will occur
during the first two days of the field work being completed on a site-by-site basis of the project to
verify that all established procedures are followed. Upon detection of a deficiency, the auditor has
the authority to stop work being conducted with the notification of the project manager and TOM in
order to determine and implement corrective action. Follow-up audits will be conducted to correct
deficiencies and to verify that QA procedures are maintained throughout the project. The audits will
involve review of field measurement records, instrumentation calibration records, and sample docu-
mentation. A summary of general considerations for field audits is presented in Figure C-l.
External field audits may be conducted by the U.S. EPA Office of Research and Development
National Risk Management Research Laboratory's Air Pollution Prevention and Control Division.
These audits may be conducted anytime during the field operations. These audits may or may not be
announced and are at the discretion of the U. S. EPA. External field audits will be conducted according
to the field activity information presented in the QAPP.
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I. Sample Collection
Work Plan Adherence
Proper Documentation
• Sample matrix
• Location
• Volume
• Analysis requested
• coc
II. Sample Storage and Shipment
Proper Containers and Preservative
Samples Refrigerated/Iced
III. Decontamination
Equipment
• Protective
• Sampling
• Large (backhoes, drill rigs, etc.)
Proper Solutions Used
Disposal Procedure
IV. Safety
Proper Level of Protective Clothing
Site Health and Safety Plan Present
Monitoring Equipment
First Aid Accessibility
V. Quality Control
DQOs
SOPs for Sampling
Work Plan Availability
Weather Conditions Affecting Sample Quality
Figure C-1. Field QA/QC Audit Outline.
The internal performance and system audits of an analytical laboratory may be conducted by
the contractor's QA officer or authorized QA chemist. Internal performance and system audits are
not currently anticipated. The system audits may be conducted on an as-requested basis if QC
problems are suspected and will include examination of laboratory documentation on sample
receiving, sample log-in, sample storage, COC procedure, sample preparation and analysis, instrument
operating records, and so forth. Blind replicate QC samples may be collected and submitted to the
laboratory concurrently with the project samples. The QA officer will evaluate the analytical results
of these blind performance samples to ensure the laboratories maintain acceptable performance. A
summary of general considerations for laboratory audits is presented in Figure C-2. Upon detection
of a deficiency, the auditor has the authority to stop work being conducted with the notification of the
project manager and TOM in order to determine and implement corrective action.
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I. Sample Receipt
coc
Adequate Facilities
II. Sample Storage
Controlled Access
Proximity to Chemical Storage
Physical Conditions
Holding Times
III. Sample Work and Analysis
SOPs
Adequate Facilities
• Organized work space
• Proper ventilation
• Minimized contamination
Notebooks
Logbooks
• Sample and standard preparation
• Instruments - sample analysis
• Calibration - tune
• Check samples
• Balance
• Temperature
IV. QC Samples
Blanks
Spikes
Duplicates
Surrogates
Control charts
V. Lab Organization
Internal QA Program
• Written QA Plan
• Internal Audit
Data Handling and Review
Data File Storage
• Hard Copies
• Other Media
Lab Capacity
Figure C-2. Laboratory QA/QC Audit General Considerations.
Corrective actions may be required for two classes of problems: analytical and equipment problems
and noncompliance problems. Analytical and equipment problems may occur during sampling and
sample handling, sample preparation, laboratory instrumental analysis, and data review.
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For noncompliance problems, a formal corrective action program will be determined and
implemented at the time the problem is identified. The person who identifies the problem is
responsible for completing a Nonconformance Report and notifying the project manager. If the
problem is analytical in nature, information on these problems will be promptly communicated to the
QA officer. Implementation of corrective action will be confirmed in writing through the same
channels and by completing a Corrective Action Report. Figure C-3 presents a sample corrective
action report.
Any nonconformance with the established QC procedures in the site-specific QAPP will be
identified and corrected. The project manager, TOM, laboratory manager or RPM or their designee
will issue a Nonconformance Report for each nonconforming condition.
Corrective actions will be implemented and documented in the field record book. No staff member
will initiate corrective action without prior communication of findings to the field team manager. If
corrective actions are insufficient, work may be stopped by stop-work order by the project manager,
laboratory manager or the TOM.
Technical staff and project personnel will be responsible for reporting all suspected technical or
QA nonconformances or suspected deficiencies of any activity or issued document by reporting the
situation to the project manager or designee. This manager will be responsible for assessing the
suspected problems in consultation with the project QA officer on making a decision based on the
potential for the situation to impact the quality of the data. If it is determined that the situation
warrants a reportable nonconformance requiring corrective action, then a nonconformance report will
be initiated by the manager.
The project manager will be responsible for ensuring that corrective action for nonconformances
are initiated by:
• Evaluating all reported nonconformances,
• Controlling additional work on nonconforming items,
• Determining disposition or action to be taken,
• Maintaining a log of nonconformances,
• Reviewing nonconformance reports and corrective actions taken, and
• Ensuring nonconformance reports are included in the final site documentation in project files.
If appropriate, the project manager will ensure that no additional work dependent on the
nonconforming activity is performed until the corrective actions are completed.
Corrective action for field measurements may include:
• Repeating the measurement to check the error,
• Checking for all proper adjustments for ambient conditions such as temperature,
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Corrective Action Report
Date: Job Name:
Name: Title:
Description of Problem:
Reported to:
Name:
Title:
Corrective Action:
Reviewed and Implemented by:
Name: Title:
Six-Week Follow-up Performed by:
Name: Title:
cc: project manager
QA officer
Project Activity Log
Figure C-3. Sample Corrective Action Report.
Checking the batteries,
Recalibrating,
Checking the calibration,
Replacing the instrument or measuring devices, or
Stopping work (if necessary).
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The laboratory manager or his designee is responsible for all on-site activities of the project team.
In this role, the laboratory manager is required to adjust the activities and schedule to accommodate
site-specific needs. When it becomes necessary to modify a QAPP, the responsible person notifies
the TOM of the anticipated change and implements the necessary changes after obtaining the
approval of the TOM. The change in the program will be documented on a field change request (FCR)
signed by the initiators and the project manager. The FCR for each document will be numbered
serially. The FCR shall be referenced in the field team manager's log book, and they will be
transported to the project record office for filing and storage. Figure C-4 presents a sample FCR. The
TOM must approve the change in writing, if feasible, or verbally prior to field implementation. If
unacceptable, the action taken during the period of deviation will be evaluated in order to determine
the significance of any departure from established program practices and action taken.
The project manager is responsible for controlling, tracking, and implementing the identified
changes. Reports on all changes will be distributed to all affected parties, which includes the TOM,
laboratory manager, contractor project manager, and the contractor QA officer.
Corrective actions are required whenever an out-of-control event or potential out-of-control event
is noted. The investigative action taken is dependent on the analysis and the event. Laboratory
personnel are alerted that corrective actions may be necessary if:
• QC data are outside the warning or acceptable windows for precision and accuracy;
• Blanks contain target analytes above acceptable levels;
• Undesirable trends are detected in spike recoveries or RPD between duplicates;
• There are unusual changes in detection limits;
• Deficiencies are detected by the QA Department during internal or external audits or from the
results of performance evaluation samples; or
• Inquiries concerning data quality are received.
Corrective action procedures are often handled at the bench level by the analyst, who reviews the
preparation or extraction procedure for possible errors and checks the instrument calibration, spike
and calibration mixes, instrument sensitivity, and so on. If the problem persists or cannotbe identified,
the matter is referred to the laboratory supervisor, manager, or QA department for further investi-
gation. Once resolved, full documentation of the corrective action procedure is filed with the QA
department.
The contractor QA officer also may request corrective action for any contractual nonconformance
identified by audits or data validation. The TOM may request corrective action by the laboratories
for any nonconformances identified in the data validation process through the ERTC manager.
Corrective action may include:
• Re-analyzing the samples, if holding time criteria permits,
• Resampling and analyzing,
• Evaluating and amending sampling procedures or evaluating and amending analytical
procedures, or
• Accepting data and acknowledging the level of uncertainty.
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Date:
Project Name:_
Description of Change:
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Field Change Request
Project No.
Initiator:
Date:
Reason for Change:
Approvals:
Field Team Leader:
QA officer:
Project manager:
Owner Representative:
Date:.
Date:.
Date:
Date:
Figure C-4. Sample Field Change Request.
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If resampling is deemed necessary due to laboratory problems, the project manager must identify
the necessary approach including cost recovery for the additional sampling effort.
C.2 QA Reports to Management
Periodic reports will be submitted by the Q A officer. Table C-1 lists all Q A reports to management.
Table C-1. QA Reports to Management.
Report
Progress
Quarterly QA
Performance
Self-Evaluation
Lab Audit
Data Validation
Frequency
Monthly
Quarterly
As needed
As needed
As needed
Distribution
TOM, Laboratory
Manager, RPM, EPA
QC Manager
TOM, Laboratory
Manager, EPA QC
Manager
TOM, Laboratory
Manager, EPA QC
Manager
TOM, Laboratory
Manager, EPA QC
Manager
Laboratory Manager,
TOM, RPM, EPA-QC
Manager
Comments
Contains QA section where monthly activities
are listed and includes any audits performed
during the month and proposed corrective
actions.
Summarizes status report of corrective actions
initiated during the quarter.
Contains QA section outlining performance on
all sites.
Audit findings report including list of audit
exceptions and rating of the laboratory
following an on-site systems audit.
Report summarizes the findings from the
validation of a data package submitted by the
subcontracted laboratory.
ELEMENT D. DATA VALIDATION AND USE
Data are reviewed and validated by the contractor's Q A officer using the laboratory data validation
guidelines established by the U. S. EPA in the reference titled "Laboratory Data Validation Functional
Guidelines for Evaluating Organic/Pesticides and PCB's analyses" EPA/540/R94/090-092. Additional
criteria may be deemed necessary by the EPA on a site-specific basis. These additional requirements
will be listed in a site-specific QAPP, if needed.
D.I Validation and Verification Methods
All samples collected at a project site will be analyzed on site or sent to the analytical laboratory
that has been selected by ERTC in accordance with existing contract procedures.
The analytical laboratory will perform in-house analytical data reduction and verification under
the direction of the laboratory manager. The laboratory QA officer is responsible for assessing data
quality and advising of any data that were rated "preliminary" or "unacceptable" or other notations
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that would caution the data user of possible unreliability. Data reduction, validation, and reporting
by the laboratory(ies) will be conducted as follows:
• Raw data produced by the analyst is turned over to the respective area supervisor;
• The area supervisor reviews the data for attainment of QC criteria as outlined in established
EPA methods and for overall reasonableness;
• Upon acceptance of the raw data by the area supervisor, a computerized report is generated and
sent to the laboratory QA officer;
• The laboratory QA officer completes a thorough audit of reports at a frequency of one in ten,
and an audit of every report for consistency;
• The QA officer and subject area supervisors decide whether any sample reanalysis is required;
and
• Upon acceptance of the preliminary reports by the QA officer, final reports will be generated
and signed by the laboratory project manager. The laboratory package shall be presented in the
same order in which the samples were analyzed.
Data packages will be organized in accordance with the data package checklist and the data
package inventory list (Figures D-l and D-2). Then, data will be sent to the contractor project
management office for data validation.
The contractor QA chemist will conduct a systematic review of the data to verify compliance with
established QC criteria based on the spike, duplicate, and blank results provided by the laboratory.
An evaluation of data accuracy, precision, sensitivity, and completeness based on criteria in Section
B will be performed and presented in the site report.
The data review will identify any out-of-control data points and data omissions and interacts with
the laboratory to correct data deficiencies. Decisions to repeat sample collection and analyses may
be made by the TOM based on the extent of the deficiencies and their importance in the overall
context of the project.
Validation will be accomplished by comparing the contents of the data packages and QA/QC
results to the requirements contained in Office of Solid Waste and Emergency Response Directive
9360.4-01. Raw data such as GC/MS ion abundance chromatograms, GC chromatograms, and mass
spectra, data reports, and data station printouts will be examined to ensure that reported results are
accurate. The contractor QA officer will be responsible for this.
The quality of analytical data used throughout a project is determined by assessing the data
usability and evaluating the compliance of the data with the analytical protocol. This is determined
by assessing quantitative and qualitative quality control measures. Analytical data validation is a
rigorous qualitative and quantitative assessment of the reported analytical data and provides an
indication of the overall data quality for use in the decision making process. The data quality
assessment is based on both an evaluation of the compliance to the method performance, reporting,
and quality control criteria as well as on evaluation and interpretation of the QC measured and their
impact on the usability of the results.
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EQ
^ DATA PACKAGE CHECKLIST
C.O.C.# Laboratory:.
I. GENERAL
1. All enclosed pages are legible, sequentially numbered, and easily identifiable.
2. There are no yellow sticky notes, tablet sheets, or other undocumented forms in
the data package.
3. All required documents, including a completed chain of custody form are enclosed.
4. The data package is divided into sections that are clearly labeled for each analyte
or method.
II. NOTEBOOK PAGES
5. All copies of notebook pages are identified by notebook number (if applicable) and
page number.
6. All units are clearly defined.
7. Each page has been signed and dated by the analyst and reviewer.
8. All written explanations have all of the necessary information included and may
stand alone as written.
III. CERTIFICATE OF ANALYSIS
9. The report sheet has been signed and dated by both the reviewer and the analyst.
IV. RAW DATA
10. All raw data (chromatograms, quant lists, other instrument output, etc.) has been
labeled properly, signed, and dated by the analyst.
V. CORRECTIONS
11. No white-out or correction tape has been used on any raw data.
12. All cross-outs consist of only a single line, and have been initialed and dated.
13. All cross-outs have a legitimate, sufficient, documented explanation.
I have checked this report and data package to make certain that the above conditions are in
compliance with the assigned data quality objective.
Name Title Date
Data were obtained while the analytical process was in-control and met the agreed upon data
quality objectives.
Project Manager Date
Figure D-1. Data Package List.
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E
Q
DATA PACKAGE DOCUMENT INVENTORY LIST
c.o.c.#
Laboratory:,
If the listed document is in the data package, initial and indicate the page of the associated item:
Document
Narrative
Review sign-off sheet
Chain-of-custody sheet
Methods used
Sample results report form
QA/QC results report form
Copy of extraction and logbook pages
Extraction / sample preparation bench sheets
DFTPP 12 hour tuning and mass calibration report(s)
BFB 12 hour tuning and mass calibration report(s)
Initial calibration raw data
Continuing calibration raw data
Raw data for field, QC, and blank samples
Check-standard results
Chromatogram with peak indicated, dated and initialed
Expanded scale blow-up of manually integrated peak
Unknown report, library search, best-fit spectra
Raw data for quantitated analytes
Serial Dilutions
Standard Methods
Interference Check Standard
Example calculations
Page#
Initial
For Items that are not applicable note as N/A
I have checked this report and certify that the above items are present in the data package and
are found on the associated page number.
Name
Title
Date
Figure D-2. Data Package Document Inventory List
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QA Level IA is a term to describe a data package standard that has neither definitive identification
of pollutants nor definitive quantitation of their concentration level. It is used to determine a quick
preliminary assessment of site contamination.
QA Level IB is a term to describe a data package standard that requires additional deliverables and
further review of the data than a QA Level IA package. Laboratory precision and accuracy data are
evaluated (through the use of summary forms) in this level to provide results that can be
semiquantitative. It is used for analyte-specific site assessments.
The QC chemist is responsible for
• Reviewing faxed preliminary laboratory data to verify that requested methods were used,
appropriate detection limits were achieved, sample identifications are correct, and the data was
reported on time;
• Verifying completeness of package and reviewing calibration data, QC sample results, raw data
(if applicable), and any problems identified by the laboratory;
• Contacting laboratory to recover items not found in the preliminary data check and maintaining
communication with the laboratory as the need arises throughout the data validation procedure;
• Performing the data validation as outlined in Section 6.0 of this document and completing the
Data Validation Checklist; and
• Completing the Validation Report that details and summarizes the findings of the data
validation.
D.1.1 QA Level IA Data Validation
Once a final data package is received by the contractor, the QC chemist separates the package into
sections and notes if any items are missing.
If items are missing from the data package, the laboratory is notified, and the missing items are
requested to be sent the next business day.
Once the package is complete, the following items are reviewed:
• Chain-of-custody information,
• Sample results summary,
• Method references,
• Dates of extraction and analysis,
• Calibration summaries, and
• Surrogate recoveries.
The sample result certificates are copied and the originals are forwarded to the project manager
along with a cover letter identifying the results of the QA IA validation.
D.1.2 QA Level IB Data Validation
All criteria in the Q A Level IA Data Validation are reviewed; however, the following items in the
data package are also evaluated:
• Matrix spike and matrix spike duplicate results,
• Sample duplicate results,
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• Laboratory control sample results,
• Tuning criteria (if applicable),
• Internal standards results (if applicable),
• Method blank summaries, and
• Interference check sample results (if applicable).
The sample result certificates are copied and the originals are forwarded to the project manager
along with a cover letter identifying the results of the QA IB validation.
Included in data validation of a sample set is an assessment of COC and associated field QC
samples. COC must be maintained from point of sampling through laboratory analysis. Both field and
laboratory COCs are reviewed and certified by the validator. Field QC samples are also reviewed,
verified, and reported in the validation report. Field QC sample acceptance criteria are presented in
Section B.
All data generated for the sites will be in a format organized to facilitate data review and
evaluation. The computerized data set will include the data flags determined by data validation. The
data flags will include such items as: (1) concentration below required detection limit, (2) estimated
concentration due to poor spike recovery, and (3) concentration of chemicals also found in laboratory
bank. The data reviewer comments will indicate that the data are: (1) usable as a quantitative con-
centration, (2) usable with caution as an estimated concentration, or (3) unusable due to out-of-control
QC results.
The data set will be presented to the TOM and available for controlled access by the project
manager and authorized personnel using a site-specific project number. The complete data set will
be incorporated into the final site report.
D.2 Reconciliation with User Requirements
The purpose of data reconciliation is to determine if the data qualitative and quantitative are of
the right type, quantity, and quality to support their intended use. To that end, evaluations will be
performed by the contractor's data reduction and information specialist to reconcile data with the
requirements defined by project specifications.
The data quality assessment (DQA) process is used to reconcile results with DQOs. By using the
DQA process, decisions or estimates can be made with the desired confidence, and sampling design
performance over a wide range of performance outcomes can be determined.
The DQA process involves five steps that begins with a review of the planning documentation and
ends with an answer to the question posed during the planning phase of the study. These steps
roughly parallel the actions of an environmental statistician when analyzing a set of data. The five
steps are briefly summarized as follows:
1. Review the DQOs and Sampling Design Review the DQO outputs to ensure that they are still
applicable. If DQOs have not been developed, specify DQOs before evaluating the data (e.g.,
for environmental decisions, define the statistical hypothesis and specify tolerable limits on
decision errors; for estimation problems, define an acceptable confidence or probability interval
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width). Review the sampling design and data collection documentation for consistency with the
DQOs.
2. Conduct a Preliminary Data Review Review QA reports, calculate basic statistics, and generate
graphs of the data. Use this information to learn about the structure of the data and identify
patterns, relationships, or potential anomalies.
3. Select the Statistical Test Select the most appropriate procedure for summarizing and analyzing
the data, based on the review of the DQOs, the sampling design, and the preliminary data
review. Identify the key underlying assumptions that must hold for the statistical procedures to
be valid.
4. Verify the Assumptions Verify the assumptions of the statistical test and evaluate whether the
underlying assumptions hold or whether departures are acceptable, given the actual data and
other information about the study.
5. Draw Conclusions from the Data. Perform the calculations required for the statistical test and
document the influences drawn as a result of these calculations. If the design is to be used
again, evaluate the performance of the sampling design.
These five steps are presented in a linear sequence, but the DQA process is by its very nature
iterative. For example, if the preliminary data review reveals patterns or anomalies in the data set that
are inconsistent with the DQOs, then some aspects of the study planning may have to be reconciled
in Step 1. Likewise, if the underlying assumptions of the statistical test are not supported by the data,
then previous steps of the DQA process may have to be revisited. The strength of the DQA process
is that it is designed to promote an understanding of how well the data satisfy their intended use by
processing it in a logical and efficient manner.
Nevertheless, it should be emphasized that the DQA process cannot absolutely prove that one has
or has not achieved the DQOs set forth during the planning phase of a study. This situation occurs
because a decision maker can never know the true value of the item of interest. Data collection only
provides the investigators with an estimate of this, not its true value. Further, because analytical
methods are not perfect, they too can only provide an estimate of the true value of an environmental
sample. Because investigators make a decision based on estimated and not true values, they run the
risk of making a wrong decision (decision error) about the item of interest.
For this project, the qualitative objectives are to determine if LFG controls are needed. This
generic QAPP and the site-specific QAPPs result from the systematic planning process and contain
information needed to carry out the data gathering and meet the DQOs. Combined with the likely
variability of emissions and the proximity to off site structures, the threshold of what will qualify as
significant will be determined by the RPM. Based on these premises, quantitative objectives are
established for critical measurements in terms of data quality indicators goals for accuracy, precision,
and completeness. The target acceptance criteria for these indicators are included in Tables A-5, A-6,
and A-7.
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APPENDIX A
SITE I SPECIFIC QAPP
(TO BE DEVELOPED BY THE RPM)
A-l
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