&EPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/1-89-001
July 1989
Air/Superfund
AIR / SUPERFUND
NATIONAL TECHNICAL
GUIDANCE STUDY SERIES
Volume I - Application
of Air Pathway
Analyses for
Superfund Activities
Interim Final
Repository Material
'eminent Cofeetion
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PROCEDURES FOR CONDUCTING AIR PATHWAY
ANALYSES FOR SUPERFUND APPLICATIONS
VOLUME I
APPLICATION OF AIR PATHWAY ANALYSES
FOR
L\ SUPERFUND ACTIVITIES
INTERIM FINAL
Prepared for:
Mr. Mark E. Garrison, Work Assignment Manager
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
P
U
U.S. EPA Headquarters Library
Mail code 3201
-*> 1200 Pennsylvania Avenue NW
p, Washington DC 20460
K August 11, 1989
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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PREFACE
This Is one In a series of manuals dealing with air pathway analysis at
hazardous waste sites. This document was developed for the Office of Air
Quality Planning and Standards 1n cooperation with the Office of Emergency
and Remedial Response (Superfund). It has been reviewed by the National
Technical Guidance Study Technical Advisory Committee and an expanded review
group consisting of State agencies, various groups within the U.S. Environ-
mental Protection Agency, and the private sector. This document is an
interim final manual offering technical guidance for use by a diverse
audience including EPA Air and Superfund Regional and Headquarters staff,
State Air and Superfund program staff, Federal and State remedial and removal
contractors, and potentially responsible parties In analyzing air pathways at
hazardous waste sites. This manual is written to serve the needs of in-
dividuals having different levels of scientific training and experience in
designing, conducting, and reviewing air pathway analyses. Because assump-
tions and judgments are required in many parts of the analysis, the In-
dividuals conducting air pathway analyses need a strong technical background
in air emission measurements, modeling, and monitoring. Remedial Project
Managers, On Scene Coordinators, and the Regional Air program staff,
supported by the technical expertise of their contractors, will use this
guide when establishing data quality objectives and the appropriate
scientific approach to air pathway analysis. This manual provides for flexi-
bility in tailoring the air pathway analysis to the specific conditions of
each site, the relative risk posed by this and other pathways, and the pro-
gram resource constraints.
Air pathway analyses cannot be reduced to simple "cookbook" procedures.
Therefore, the manual is designed to be flexible, allowing use of profes-
sional judgment. The procedures set out in this manual are intended solely
for technical guidance. These procedures are not intended, nor can they be
relied upon, to create rights substantive or procedural, enforceable by any
party in litigation with the United States.
It is envisioned that this manual will be periodically updated to incor-
porate new data and information on air pathway analysis procedures. The
Agency reserves the right to act at variance with these procedures and to
change them as new information and technical tools become available on air
pathway analyses without formal public notice. The Agency will, however,
attempt to make any revised or updated manual available to those who
currently have a copy through the registration form included with the manual.
Copies of this report are available, as supplies permit, through the
Library Services Office (MD-35), U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711 or from the National Technical
Information Services, 5285 Port Royal Road, Springfield, Virginia 22161.
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DISCLAIMER
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use by the Air Management Division, U.S.
Environmental Protection Agency.
ii
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TABLE OF CONTENTS
Page
DISCLAIMER 1 i
ACKNOWLEDGEMENT vi
ACRONYMS vii
1.0 INTRODUCTION 1-1
2.0 AIR PATHWAY ANALYSES PROCESS OVERVIEW 2-1
2.1 Overview 2-1
2.2 Air Emission Mechanisms 2-2
2.3 Atmospheric Processes 2-7
2.4 Receptor Exposure Potential 2-9
2.5 Air Pathway Analyses Approaches 2-10
3.0 SUPERFUND AIR EMISSION SOURCES 3-1
3.1 Overview 3-1
3.2 Uncontrolled Sources 3-2
3.3 Remediation Sources 3-10
3.4 Post-Remediation Sources 3-16
4.0 APPLICATION OF AIR PATHWAY ANALYSES TO SUPERFUND 4-1
4.1 Overview 4-1
4.2 Remedial and Removal Applications 4-11
4.3 Application of Data Quality Objectives 4-17
5.0 OVERALL PROCEDURES FOR CONDUCTING AIR PATHWAY ANALYSES FOR
SUPERFUND 5-1
5.1 Overview 5-1
5.2 Recommended Superfund APA Procedure 5-3
5.3 Technical Procedures 5-8
5.4 Estimation of Baseline Emissions 5-11
5.5 Estimation of Emissions form Clean-up Activities 5-21
5.6 Dispersion Modeling and Air Monitoring Procedures 5-37
6.0 REFERENCES 6-1
iv
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LIST OF TABLES
Table Pace
1 Air Emission Mechanisms - Gas Phase Emissions 2-3
2 A1r Emission Mechanisms - Participate Emissions 2-6
3 Typical Emission Rates by Pollutant Class: Uncontrolled
Sources (Radian 1989a, Radian 1989b, EPA 1987b) 3-3
4 Typical Emission Rates by Pollutant Class: Remediation
Sources (Radian 1989a, Radian 1989b, EPA 1987b) 3-4
5 Typical Emission Rates by Pollutant Class: Uncontrolled
Sources (Radian 1989a, Radian 1989b, EPA 1987b) 3-5
6 Sources of Potential Superfund ARARs 4-8
7 Summary Table on Information on the Various Classes of
Assessment Technologies and Screening Assessment
Technologies 5-22
8 Summary Table on Information on the Various Classes of
Assessment Technologies and In-Depth Assessment
Technologies 5-24
9 Control Technologies Available for Each Remedial Option 5-31
10 Summary of Typical Air Emission Values by Source Type 5-33
iv
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LIST OF FIGURES
Figure Pace
1 Procedures for Conducting A1r Pathway Analyses (APA) for
Superfund Applications - Overview 1-4
2 Superfund Air Pathway Analyses (APAs) Activity-Specific-
Applications - Overview 4-2
3 Data Qual Ity Objectives ' Process Overview 4-19
4 Data-Quality Objectives - Application to Air Pathway
Analyses 4-20
5 Procedures for Conducting Air Pathway Analyses for Superfund
Appl 1 cat ions 5-2
6 Recommended Superfund Air Pathway Analyses - Procedure
Overview 5-4
7 Recommended Superfund Air Pathway Analyses Technical
Procedures - General Format 5-9
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ACKNOWLEDGMENT
This document was prepared for the U.S. Environmental Protection Agency
(EPA) by NUS Corporation and Radian Corporation. The project was managed by
Mr. Mark Garrison, National Oceanic and Atmospheric Administration, who is
assigned to the EPA-Region III. The principal author was Mr. Ronald Stoner
of NUS. The author would like to thank Mr. Jim Vickery and Mr. Joseph
LaFornara of the EPA Office of Emergency and Remedial Response as well as Mr.
Joseph Padgett, Mr. Stan Sleva, Mr. Joseph Tikvart, and Mr. James Durham of
the EPA - Office of Air Quality Planning and Standards, and Mr. Al Cimorelli
of EPA - Region III for their guidance and direction. He would also like to
acknowledge Mr. Robert Jubach, Mr. Hank Firstenberg, Mr. Thomas laccarino,
Mr. Ted Koss, and Ms. Elizabeth Butler for their overall contribution to this
document. Mr. Bart Eklund of Radian Corporation provided the final editing
of the manual and wrote portions of Section 5.
vi
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SUPERFUND ABBREVIATIONS/ACRONYMS
ACGIH American Conference of Government Industrial Hygienists
ACL Alternate Concentration Limit
AO Administrative Order on Consent
APA Air Pathway Analysis
APCD Air Pollution Control Device
ARAR Applicable or Relevant and Appropriate Requirement (Cleanup
Standard)
ATSOR Agency for Toxic Substances and Disease Registry
CAA Clean Air Act
CAS Carbon Adsorption System
CD Consent Decree
CERCLA Comprehensive Environmental Response, Compensation, and Liability
Act
CERCLIS Comprehensive Environmental Response, Compensation, and Liability
Information System
CERI Center for Environmental Research Information
CFR Code of Federal Regulations
CR Community Relations
CRF Combustion Research Facility -- Pine Bluff, Arkansas
CWA Clean Water Act
DQO Data Quality Objective
DRE Destruction and Removal Efficiency
EDO Enforcement Decision Document
ERT Environmental Response Team
ESP Electrostatic Precipitator
FIFRA Federal Insecticide, Fungicide, and Rodenticide Act
FP Fine Particualte
vii
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FS Feasibility Study
MRS Hazard Ranking System
HSWA Hazardous Waste Engineering Amendments to RCRA, 1984
HWERL Hazardous Waste Engineering Research Laboratory
IDLH Immediately Dangerous to Life or Health
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
NBAR Non-binding Preliminary Allocation of Responsibility
NCP National Contingency Plan
NEIC National Enforcement Investigations Center
CFPA National Fire Protection Association
NIOSH National Institute of Occupational Safety and Health
NPL National Priorities List
NRC National Response Center
NRT National Response Team
NTIS National Technical Information Service
OERR Office of Emergency and Remedial Response
O&M Operation and Maintenance
ORD Office of Research and Development
OSC On-Scene Coordinator
OSH Act Occupational Safety and Health Act
OSHA Occupational Safety and Health Administration
OSWER Office of Solid Waste and Emergency Repsonse
OTA Office of Technology Assessment
PA Preliminary Assessment
PEL Permissible Exposure Limits
PIC Products of Incomplete Combustion
viii
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PM-20 Particualte Matter with Physical Diameter <20 urn
PRP Potentially Responsible Party
QA/QC Quality Assurance/Quality Control
QAPP Quality Assurance Project Plan
RA Remedial Action
RCRA Resource Conversation and Recovery Act
RD Remedial Design
REL Recommended Exposure Limit
RI Remedial Investigation
RI/FS Remedial Investigation/Feasibility Study
ROD Record of Decision
RPM Remedial Project Manager
RRT Regional Response Team
RQ Reportable Quantity
SAB Science Advisory Board
SARA Superfund Amendments and Reauthorization Act
SCAP Superfund Comprehensive Accomplishments Plan
SI Site Inspection
SITE Superfund Innovative Technology Evaluation
SWDA Solid Waste Disposal Act (RCRA predecessor)
TLV Threshold Limit Value
TLV-C Threshold Limit Value - Ceiling
TLV-STEL Threshold Limit Value - Short-Term Exposure Limit
TLV-TWA Threshold Limit Value - Time-Weighted Average
TSDF Treatment Storage and Disposal Facility
TSCA Toxic Substances Control Act
ix
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TSP Total Suspended Part1culate
Title III Emergency Planning and Community Right-To-Know Act (SARA)
T&E Testing and Evaluation
UST Underground Storage Tank
VO Volatile Organics
VOC Volatile Organic Compound
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SECTION 1
INTRODUCTION
The muH1 -volume set of Procedures for Conducting Air Pathway Analyses
for Superfund Applications has been developed by the U.S. Environmental
Protection Agency (EPA) to address the potential for hazardous air emissions
from Superfund sites. These emissions can occur at hazardous spill locations,
undisturbed Superfund sites, as well as during site cleanups. Under the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
and the recent Superfund Amendments and Reauthorization Act (SARA), EPA has
the responsibility for assessment and cleanup of Superfund sites. Although
air emissions pose a potential human health risk at these sites, comprehensive
national guidance does not exist for determining the magnitude and impact of
these emissions.
An air pathway analysis is a systematic approach which involves the
application of modeling and monitoring methods to estimate emission rates and
concentrations of air contaminants. The goal of the multi-volume set is to
provide recommended procedures for the conduct of air pathway analyses (APAs)
which meet the needs of the Superfund program. This has been accomplished by
identifying the application of APAs in the Superfund process, and by providing
recommended procedures for conducting APAs for Superfund. The procedures are
intended for use by EPA Remedial Project Managers (RPMs), Enforcement Project
Managers (EPMs), and air experts as well as by EPA Superfund contractors. The
procedures are also generally applicable to hazardous waste sites not included
on the NPL.
The Procedures for Conducting Air Pathway Analyses for Suoerfund
Applications consists of four volumes as follows:
1-1
-------
Volume I - Application of Air Pathway Analyses for Superfund
Activities;
Volume II - Estimation of Baseline A1r Emissions at Superfund Sites;
t Volume III - Estimation of Air Emissions from Clean-up Activities at
Superfund Sites; and
Volume IV - Procedures for Dispersion Modeling and Air Monitoring
for Superfund Air Pathway Analyses.
Volume I presents the critical Information that an RPM or EPM will need
to answer the following questions:
What Is an APA and why Is It Important? (Section 2 - Air Pathway
Analyses Process Overview).
t What are the air emissions sources that should be evaluated at a
Superfund site? (Section 3 - Superfund Air Emission Sources).
0 How 1s an APA used within the Superfund process? (Section 4 -
Applications of Air Pathway Analyses to Superfund).
What Is an appropriate source-specific APA approach? (Section 5 -
Overall Procedures for Conducting A1r Pathway Analyses for
Superfund).
Where can EPA air experts and contractors find additional technical
procedures for Implementing the selected APA approach? (Section 5 -
which provides cross-references to Volumes II-IV).
The emphasis of Volume I Is providing a recommended APA procedure for the
remedial phase of the Federal Superfund process. The pre-remedial Superfund
activities (e.g., National Priority List scoring) already have a structured
1-2
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screening approach (I.e., the Hazard Ranking System) which accounts'for the
air pathway. The procedures, especially Volume I, are Intended to provide a
consistent and technically adequate approach for the conduct of APAs for
remedial phase activities (I.e., Remedial Investigations/Feasibility Studies,
Records of Decision, Remedial Actions and Operation and Maintenance). The APA
approaches discussed In Volume I are also generally applicable to removal
activities (If planning time for the selection and conduct of an APA Is
allowed) as well as to remedial activities since the activities of both are
similar except that removal activities operate under an accelerated schedule.
Volume I defines the general procedure for the conduct of APAs for
Superfund and references appropriate sections within Volumes II-IV for
detailed technical procedures regarding modeling and monitoring techniques
(see Figure 1). Volumes II through IV present and discuss alternative
modeling techniques and monitoring techniques for Implementing the Superfund
APA procedure presented in Volume I. Volume II (Radian, 1989a) presents
procedures for developing baseline air emissions for uncontrolled Superfund
sites, with an emphasis on landfills and lagoons. Volume III (Radian, 1989b)
presents procedures for estimating air emission impacts from remedial
activities. This volume includes emission estimation techniques for sources
such as incinerators, air strippers, soil vapor extraction, and soil handling.
Volume IV (NUS, 1989) presents procedures for dispersion modeling and air
monitoring. The information in Volumes II, III, and IV will be primarily of
interest to EPA air experts and Superfund contractors responsible for the
conduct of APAs. However, the technical procedures provided in Volumes II-IV
are not Superfund-activity specific. Therefore, Volumes II-IV will also be
useful to state air staff responsible for supporting hazardous waste site
cleanup projects.
1-3
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VOLUME I
APPLICATION OF AIR PATHWAY
ANALYSES FOR SUPERFUND ACTIVITIES
Identify Superfund Remedial
Activity- and Source-Specific
Need for an APA
Recommend APA Procedures for
Superfund Applications
e Reference Volumes II-IV for
Supplemental Technical
Procedures/RecommendatIons
RPMs/EPMs
1
Volume II
Procedures for Developing
Baseline Air Emission Estimates
Procedures for Baseline
Emission Estimates
Emission Estimation Techniques
for Landfill and Lagoons
i '
Volume III
Procedures for Estimating
Air Emission Impacts from
Remedial Activities
Procedures for Estimating
"Emissions
Emission Estimation
Techniques for
Incineration, Air Stripping
and Soils Handling and
Venting
1
Volume IV
Procedures for Dispersion
Modeling and Air Monitoring
Procedures for Dispersion
Modeling and Monitoring
Technical Recommendations
for Modeling and
Monitoring
Technical Staff/Contractors
Figure 1. Procedures for Conducting Air Pathway Analyses (APA)
for Superfund Applications - Overview.
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SECTION 2
AIR PATHWAY ANALYSES PROCESS OVERVIEW
2.1 OVERVIEW
It is Imperative that a consistent definition of air-pathway analyses be
used for specifying and implementing the recommended procedures presented in
this document. An air pathway analysis (APA) 1s a systematic approach
involving a combination of modeling and monitoring methods to assess actual or
potential receptor exposure to air contaminants. Therefore, an APA is an
exposure assessment for the air pathway and it provides input to the Superfund
risk assessment process. The primary components of an APA are:
Characterization of air emission sources (e.g., estimation of
contaminant emission rates);
Determination of the effects of atmospheric processes (e.g.,
transport and dilution); and
Evaluation of receptor exposure potential (i.e., what air
contaminant concentrations are expected at receptors of interest for
various exposure periods).
This section presents background information concerning air emission
mechanisms, atmospheric processes, receptor exposure potential and alternative
APA approaches. This information will provide an enhanced appreciation of the
bases and components of the recommended Superfund APA procedure and
supplementary technical procedures presented 1n Section 5.
2-1
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2.2 AIR EMISSION MECHANISMS
Superfund air emissions may be classified as either point or area
sources. Point sources include vents (e.g., landfill gas vents) and stacks
(e.g., incinerator and air stripper releases), while area sources are
generally associated with fugitive emissions (e.g., from landfills, lagoons
and contaminated surface areas). A further identification and discussion of
Superfund air contaminant sources is presented in Section 3.
Air contaminant emissions can be classified into two basic categories
(i.e., gas phase emissions and particulate matter emissions). The emission
mechanisms associated with gas phase and particulate matter releases are quite
different. Discussions of these air emission mechanisms are presented in the
following subsections.
A more detailed discussion of baseline air releases is presented in
Section 2 of Volume II of this series, and discussion of clean-up air
emissions is presented in Section 2 of Volume III.
2.2.1 Gas Phase Emissions
Gas phase emissions primarily involve organic compounds but may also
include certain metals. Gaseous emissions from a Superfund site can be
released through a variety of mechanisms, including:
t Volatilization;
Biodegradation;
Photodecomposition;
t Hydrolysis; and
Combustion.
The importance of each of these mechanisms varies as a function of source type
(see Table 1). The recognition of the significance of these mechanisms will
facilitate the selection of appropriate remediation approaches.
2-2
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TABLE 1. AIR EMISSION MECHANISMS - GAS PHASE EMISSIONS
ro
Volatilization
Pre- Remediation Sources
Landfills
Lagoons
Contamlnanted Soil
Surfaces
Open Containers
(above-ground)
Remediation Sources
Soil Handling
Air Stripper
Incinerator
Soil Vapor
Extraction
Solidification/
Stabilization
Post-Remediation Sources
Landfills
Lagoons
Soil Surfaces
Open Containers
(above-ground)
I
I
I
I
I
I
S
I
I
I
I
I
I
Blodegradation
S
I
I
I
N
N
N
N
N
S
I
I
I
Photo-decomposition Hydrolysis
N
S
N
S
N
N
N
N
N
N
S
N
S
N
S
N
S
N
N
N
N
N
N
S
N
S
Combustion
S
N
N
S
N
N
I
N
N
N
N
N
N
Key: I = Important
S = Secondary
N ° Negligible or Not Applicable
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Volatilization 1s 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 results In Immediate
transport Into the bulk atmosphere. Volatilization from subsurface wastes
results 1n a concentration gradient In the soil-gas from the waste to the
surface. The rate of emissions 1s usually limited by the rate of diffusion of
contaminants to the soil-air Interface. Volatilization 1s thus an Important
process for the release of gaseous emissions from both surface contamination
and contaminants in the shallow subsurface. The rate of volatilization of
contaminants at a soil-air boundary Is a function of the concentration and
properties of the escaping chemical, 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 Is dependent on the concentration of the contaminants in
the boundary layer of liquid 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. It is important to note
that "volatile" and "semi-volatile" are broad categories and further
subdivision by vapor pressure, toxicity, etc. may be necessary to properly
evaluate air emissions.
Several processes can act to reduce the concentration of a given
contaminant and thereby diminish its overall rate of emissions.
Biodegradation takes place when microbes break down organic compounds via
metabolic processes. Biodegradation may be an Important mechanism for gas-
phase emissions (and waste treatment) from wastes in the upper layers of the
soil or ponds. The rate of organic compound decomposition depends on the
structure of the compound, the metabolic requirements of the microbes, and the
amount of moisture, oxygen, and nutrients available to the microbes.
Photodecompositlon occurs when a hazardous chemical absorbs light and reacts,
or when the chemical reacts because of light absorption by surrounding
elements. Hydrolysis occurs when a chemical reacts with water. For organic
compounds, the reaction usually replaces a functional group with a hydroxyl.
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Combustion, the process of burning, can be a source of both participates
and volatile compounds (EPA, 1987b).
2.2.2 Particulate Emissions
Participate matter emissions from a Superfund site can be released
through wind erosion, mechanical disturbances, and combustion. Hazardous
substances, such as metals, can also be adsorbed onto particulate matter and
thereby transported with the Inert material. The Importance of each of these
mechanisms varies as a function of source type (see Table 2). The hazardous
constituents of concern in a particulate release may involve constituents that
are either absorbed or adsorbed onto the particulate, or constituents that
actually comprise the particulate. These 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 flow
stream. The dust generation process is caused by two basic physical
phenomena: entrainment of dust particles by the action of wind erosion of an
exposed surface under moderate-to-high wind speeds; and pulverization and
abrasion of surface materials by mechanical disturbances (EPA, 1985a).
For airborne particulates, 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
2.5 to 10 microns In diameter) are considered to be respirable and thus
present a greater health hazard than the larger particles.
2-5
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TABLE 2. AIR EMISSION MECHANISMS - PARTICULATE EMISSIONS
Pre- Remediation Sources
Landfills
Lagoons
t Contamlnanted Soil
Surfaces
t Containers
(above-ground)
Remediation Sources
0 Soil Handling
Air Strippers
t Incinerators
0 Soil Vapor Extraction
Solidification/
Stabilization
Post -Remediation Sources
Landfills
Lagoons
0 Soil Surfaces
0 Containers
(above-ground)
Wind Erosion
I
S
I
N
I
N
N
N
I
I
S
I
N
Mechanical
Disturbances
I
S
I
I
I
N
N
N
I
I
S
I
I
Combustion
N
N
N
N
N
N
S
N
N
N
N
N
N
Adsorption
S
S
I
N
S
S
S
S
S
S
S
I
N
Key: I = Important
S ° Secondary
N = Negligible or Not Applicable
2-6
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2.3 ATMOSPHERIC PROCESSES
The atmosphere 1s recognized as a major potential exposure pathway for
the migration of releases from Superfund sites. Unlike other environmental
media, the air pathway Is characterized by short migration times, relatively
large exposure areas, and a virtual Inability to mitigate the potential
consequences of a release after the contaminant enters the atmosphere. The
fundamental atmospheric processes affecting airborne contaminants Include
atmospheric transport and diffusion as well as transformation, deposition, and
depletion. The extent to which these atmospheric processes act on the
contaminant determines the magnitude, composition, and duration of the
release, the route of human exposure, and the Impact of the release on the
environment. Subsurface gas migration is another pathway which can result in
exposure to air contaminants from some Superfund sources (e.g., landfills,
underground tanks). Further discussions of the major atmospheric processes
are presented In the following subsections.
2.3.1 Transport and Diffusion
Once released to the ambient air, a contaminant Is subject to
simultaneous transport and diffusion processes 1n 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 field (as determined by wind
direction and speed conditions). 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.
2-7
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Terrain features can dramatically alter the transport and diffusion
experienced by a contaminant between Its source and receptors. Complex
terrain features such as valleys, hills and mountains can significantly affect
transport conditions and diffusion rates. The rate of diffusion will also
depend on whether the site Is located 1n an urban, rural or coastal setting.
Source factors such as release height and source configuration Influence
the transport and diffusion of air releases. In addition, atmospheric
releases Involving denser-than-air gases will behave differently than
neutrally buoyant materials.
2.3.2 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, on the other hand, 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 (Randerson, 1984). In general, however, these effects
are secondary to transport and diffusion in importance, and are subject to
more uncertainty.
Airborne contaminants can become depleted from the atmosphere by the
natural cleansing processes of wet deposition and dry deposition. Wet
deposition involves the incorporation of toxic pollutants into the various
forms of precipitation, and the subsequent deposition of the effluent onto the
ground, vegetation, and/or structures. Dry deposition proceeds without the
aid of precipitation and denotes the direct collection of gaseous and
particulate species on land or water surfaces. Gravitational settling also
plays an Important role in the deposition of particulate matter (especially
particles of greater than 30 microns In the vicinity of the source).
2-8
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Although deposition depletes concentrations of the contaminant In air, 1t
Increases the concentration of contaminants on vegetation and In soils and
water bodies. In addition, deposited contaminants are subject to some degree
of resuspenslon, particularly through wind erosion and wind speeds which
exceed 10-15 mph.
2.4 RECEPTOR EXPOSURE POTENTIAL
The primary modes of exposure to toxic contaminants released to the
atmosphere are direct Inhalation, ingestion of vegetation that is contaminated
as a result of deposition of particles, Ingestion of contaminated milk and
meat products from animals eating contaminated crops, and dermal contact.
The direct inhalation of airborne contaminants is the primary mode of
exposure from the toxic pollutant air pathway. Inhalation brings chemicals
into contact.with .the lung. Most Inhaled chemicals are gases or vapors of
volatile liquids. Absorption in the lung is usually high because the surface
area is large, and blood vessels are close to the exposed surface area.
Chemicals may also be inhaled in solid or liquid form as dusts or
aerosols. The absorption of solid particulate matter Is highly dependent upon
the size and chemical nature of the particles (Government Institutes, 1986).
The EPA has indicated that particles less than 10 microns in diameter are
small enough to penetrate to the thoracic region of the body.
The dose to an1Individual from breathing contaminated air is dependent
upon the Individual's ventilation rate (i.e., the rate of Inhaled air), body
weight, retention fraction, and the toxic air pollution concentration.
2-9
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Atmospheric deposition of contaminants onto feed crops and use of
contaminated water (due to deposition) to Irrigate feed crops can also result
1n the Ingestlon of contaminated crops by animals. In addition, contaminated
water can be used as part of the animals' drinking-water supply. Human
exposure to contaminants can then result from subsequent Ingestlon of
contaminated animal products.
Uptake of contaminants can also result from dermal contact with soil
contaminated from atmospheric deposition. Soil contact Includes both
Ingestlon from hand-to-mouth contact or absorption through the skin (Uhelan,
1987).
2.5 AIR PATHWAY ANALYSES APPROACHES
The following basic approaches are available for the conduct of APAs:
Modeling
Emission rates
Atmospheric dispersion; and
Monitoring
Emission rates
Air concentrations.
Emission modeling as well as emission monitoring can be used to
characterize source emission rates. Dispersion modeling is the primary
approach to characterize atmospheric processes and predict concentrations, and
air monitoring can be used to directly measure air concentrations at receptor
locations. However, there are numerous alternative modeling/monitoring
approaches that may be viable for site-specific APA applications.
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A1r emission models can be used to estimate constituent-specific emission
rates based on waste/source Input data for many types of Superfund sources.
(An emission rate Is defined as the source release rate for the air pathway in
terms of mass per unit time.) The models are based upon theoretical
considerations and have been evaluated against pilot-scale and field test
results. Often, the models are empirically correlated. However, because the
models attempt to predict complex physical and chemical phenomena, they are
uncertain and should be used carefully. These models can be particularly
useful when monitoring Is Impractical (e.g., when health-based criteria levels
are lower than the detection levels of a monitoring approach).
Source monitoring Is an alternative approach to determine emission rates
for existing sources. Direct emission sampling may be used for point sources
such as vents and stacks. An Isolation flux chamber (see Reference 5} may be
used for area source emission measurements. On-site air monitoring
(particularly near the emission source) is an alternative approach for
characterizing area source emissions If direct emission monitoring is not
practical (e.g., considering equipment availability and detection limits).
Atmospheric dispersion models can be used to estimate constituent-
specific concentrations at receptor locations of Interest based on input
emission rate and meteorological Input data. Atmospheric dispersion models
can also be used for monitoring program design applications to identify areas
of high concentration relative to actual receptor locations of Interest. High
concentration areas which correspond to actual receptors are priority
locations for air monitoring stations. Frequently, it may not be practical to
place air monitoring stations at actual off-site receptor locations. However,
it may be useful to characterize concentrations at these locations to support
a health and environmental assessment. In these cases, dispersion patterns
based on modeling results can be used to extrapolate monitored concentrations
to off-site receptor locations.
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Confirmatory air monitoring may also be appropriate to characterize air
concentrations for receptor locations of Interest. However, this approach Is
limited to existing sources, and monitoring methods or detection levels
commensurate with health criteria may not be available for all contaminants of
Interest.
Procedures for the selection of appropriate modeling versus monitoring
approaches for source-specific APA applications are provided in Section 5 of
this document. Additional technical discussions regarding the implementation
of modeling and monitoring APAs are presented In Volumes II through IV.
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SECTION 3
SUPERFUND AIR EMISSION SOURCES
3.1 OVERVIEW
Superfund sites are potential sources of air emissions that can Impact
onsite/offslte health and safety. Therefore, It 1s Important to Identify
site-specific air emission sources and conduct follow-up air pathway analyses
to characterize the potential Impacts. Superfund air emission sources can be
classified Into three stages as follows:
Pre-remediation sources;
Remediation sources; and
Post-remediation sources
Pre-remediation sources are Superfund sites that have not been cleaned
up, such as landfills, lagoons, contaminated soil surfaces and above-ground
containers (e.g., tanks and drums).
Remediation sources represent the disturbed site conditions during the
cleanup process. Usually, these sources have a higher air emission potential
than the undisturbed site. Remediation air emission sources Include soil
handling operations (e.g., excavation), air strippers, onsite incinerators,
soil vapor extraction (in-sltu venting), and solidification/stabilization
processes.
Post-remediation sources can Include the same types of air emission
sources found at uncontrolled sites (i.e., landfills, lagoons, contaminated
surface soils, and above-ground containers). However, air emission rates are
expected to be lower at the post-remediation stage compared to earlier stages.
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Superfund sites have the potential for gaseous and participate emissions
before, during, and after clean-up. A summary of potential emission rates
from these sources is presented in Tables 3, 4, and 5 for pre-remediation
sources, remediation sources, and post-remediation sources, respectively.
Brief discussions of each of these sources are presented in this section.
Landtreatment data are included in the tables, as they are indicative of
emissions from highly contaminated surface soils. Comprehensive discussion of
the emission potential for Superfund air emission sources are presented in
Section 2 of Volume II and Section 2 of Volume III.
3.2 PRE-REMEDIATION SOURCES
3.2.1 Landfills
A landfill is generally an excavated area or natural depression used for
waste disposal. Several methods of landfill construction exist, including the
trench, area, and ramp methods. Each method uses different techniques for
waste placement, compaction and cover. However, many landfills will lack
adequate records of waste placement techniques of waste characteristics, and
with few technological controls, such as liners or cover systems, that would
prevent escape of waste or waste constituents to the environment. For this
reason, air emissions from uncontrolled landfills are primarily area source
emissions that occur through a variety of mechanisms.
There are two primary area sources of gaseous emissions from landfills:
(1) lateral and vertical diffusion of volatile organic compounds through the
overburden or landfill cover; and (2) exposure of contaminated soils and waste
through water and wind erosion of cover material with subsequent evaporation
and/or sublimation of exposed liquids or solids. The short-term rate of
volatile emissions through the first mechanism, diffusion through the landfill
overburden or cover, is proportional to the volatility and areal extent of the
emission source. All other factors being equal, if the contaminant source is
highly volatile (expressed as a high vapor pressure or high Henry's Law
constant), volatile emissions will occur at a high rate. Likewise, if there
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TABLE 3. TYPICAL EMISSION RATES BY POLLUTANT CLASS: UNCONTROLLED SOURCES
(RADIAN 1989a, RADIAN 1989b, EPA 1987b)
Pollutant Class
Emission Rates (kg/day,
Unless Otherwise Noted)
Landfills
Volatile and semi-
volatile organ1cs
Particulates
4.18 x 10'5 - 1.06 x 10'3
kg/m'day
Not available.
Lagoons
Volatile and semi-
volatile organIcs
Partlculates
-5
6.19 x 10'3 kg/nfday
Not significant
Contamlnanted Soil
Surfaces:
Land treatment
Volatile and semi-
volatile organics
Partlculates
Not available
Not available
Waste piles
Volatile and semi-
volatile organics
Particulates
Not available
1.62 x 10'5 - 6.25 x 10'5
kg/nrday
Above-ground Containers
t Tanks
t Container storage
areas
Volatile and semi-
volatile organics
Particulates
Volatile and semi-
volatile organics
Particulates
11.54
Not significant
0.066
Not significant
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TABLE 4. TYPICAL EMISSION RATES BY POLLUTANT CLASS: REMEDIATION SOURCES
(RADIAN 1989a, RADIAN 19895, EPA 1987b)
Pollutant Class
Emission Rates (kg/day,
Unless Otherwise Noted)
Soil Handling
Volatile and seml-
volatile organics
Particulates
Not available
27.08 - 168.2
Air Strippers
Volatile and semi-
volatile organics
Particulates
0.05 - 2.5
Not significant
Incinerators*
Volatile and semi-
volatile organics
Particulate matter/
metals
NOX
HF
HC1
SO,
3.82 x 10'7 - 8.1 x 10'3
1.5 - 69
1.14 x 10'7 - 4.57 x 10'5
9.92 x 10'8 - 9.92 x 10'7
4.52 x ID'7 - 4.52 x 10'5
1.59 x 10'7 - 1.90 x 10'4
In-situ venting
Solidification/
Stabilization
Volatile and semi-
volatile organics
(uncontrolled emissions)
Volatile and semi-
volatile organics
(controlled emissions)
Volatile and semi-
volatile organics
Particulates
1-110 kg/day per
recovery well
0.01 - 5.5. kg/day per
recovery well
Not available
124 - 164
* Assume 95% efficiency for pollution control device.
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TABLE 5. TYPICAL EMISSION RATES BY POLLUTANT CLASS: UNCONTROLLED SOURCES
(RADIAN 1989a, RADIAN 1989b, EPA 1987b)
Pollutant Class
Emission Rates (kg/day,
Unless Otherwise Noted)
Landfills
Volatile and semi-
volatile organics
Participates
1.30 x 10'5 - 2.16 x 10'4
kg/nrday
Not available.
Lagoons
Volatile and semi-
volatile organics
Particulates
1.30 x 10'5 - 9.07 x 10'4
kg/nrday
Not significant
Contaminanted Soil
Surfaces:
Land treatment
Volatile and semi-
volatile organics
Particulates
8.78 x 10'4 - 0.014
kg/nrday
Not available
Waste piles
Volatile and semi-
volatile organics
Particulates
Not available
1.95 x 10'4 - 7.5 x 10-4
kg/mzday
Above-ground Containers
t Tanks
Container storage
areas
Volatile and semi-
volatile organics
Particulates
Volatile and semi-
volatile organics
Particulates
11.54
Not significant
0.066
Not significant
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1s widespread soil or ground-water contamination* diffusion of volatile
organIcs through the overburden will occur more rapidly than 1f the
contaminant source Is confined to a smaller area. The rate of gas generation
within the landfill also affects the rate of volatile emissions. Generation
of Inorganic gases (e.g., C02) within the landfill Is possible, especially at
sites with municipal wastes, and the movement of the Inorganic gases can carry
along organic compounds and enhance the latter's emission rates.
The second non-point source of gaseous emissionsexposure of
contaminated soils and waste through erosion, with subsequent evaporation
and/or sublimation of exposed liquids and solidsIs dependent on both the
construction and maintenance of the landfill cover system, and on factors that
influence erosion, such as rainfall rates and wind patterns. Emissions are
likely to be lowest at landfills that have periodic cover Inspection and
maintenance procedures, since erosion of these landfill covers would likely be
repaired before significant emissions could occur. However, uncontrolled
landfills rarely have regular cover Inspection and maintenance systems in
place, so the likelihood of emissions through this pathway at uncontrolled
landfills is high, particularly in climates conducive to erosion.
The most significant point source of gaseous emissions from landfills is
active gas venting system emissions. Active gas venting systems employ either
vacuum or positive pressure pumping to extract gases from landfill soils. The
extent of emissions from this source depends on the presence and/or efficiency
of the emission control device at the gas collection source. Commonly used
emission control devices are condensers, carbon adsorption filters, and
Incinerators. However, uncontrolled landfills are not likely to have emission
control devices in place on their gas venting systems.
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3.2.2 Lagoons
A lagoon, generally referred to for regulatory purposes as a surface
Impoundment, 1s a natural topographic depression, man-made excavation, or
diked area formed primarily of earthen materials designed to hold an
accumulation of liquid wastes, or wastes containing some liquids. The
discussion also applies to any free liquid at Superfund sites.
The primary source of air emissions from lagoons or surface Impoundments
1s emissions of volatile and semi -.volatile organlcs from the free liquid
surface. Uncontrolled Superfund sites are not likely to have mechanisms in
place (e.g., temporary covers) to control emissions from the liquid surface,
making this a significant air emissions pathway. As seen 1n Tables 3 and 5,
emissions from lagoons can be roughly equivalent to emissions from landfills.
Since lagoons are usually smaller In area, the emission rate per given area is
much higher than for landfills. Air emissions occur through evaporation, and
generation of-aerosols through wave action. The degree of emissions through
evaporation 1s also affected by the volatility and solubility of the liquid in
the Impoundment, and by environmental factors such as temperature, atmospheric
pressure, and wind speed. Wind speed also affects generation of aerosols
through wave action.
At sites where there has been subsurface contamination of soils or ground
water through overtopping or leaks, a second, less important, source of
volatile and semi-volatile emissions Is lateral and vertical diffusion of
contaminants through the surrondlng soil. Significant air emissions through
this pathway are most likely at lagoons without natural or synthetic liners,
or where the bottom of the lagoon 1s at or near the water table. The extent
of emissions from this pathway also depends on the areal extent and chemical
nature (I.e., volatility) of the contaminants In the subsurface, and on the
physical properties of the soil (porosity, density, and moisture content)
surrounding the Impoundment.
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A final potential source of contaminant emissions from lagoons Is wind
erosion of contaminated soils and solid residues from dry areas of the
Impoundments or Impoundment berms. Generally, however, this Is not a
significant source of part1culate emissions.
3.2.3 Contaminated Soil Surfaces
Soil contamination and subsequent gaseous and partIculate air emissions
can occur through a variety of mechanisms, Including breaching of above-ground
tanks and containers, overtopping of surface Impoundments, subsurface seepage
of leachate from burled waste, and spills occurring through careless waste
handling practices. Wind transport of aerosols may occur during waste
application; volatilization may occur after waste application; and erosion of
contaminated soils may occur at any time. All of these air release mechanisms
are affected by meteorological factors such as temperature, precipitation,
wind speed, and barometric pressure.
Depending on their configuration with respect to prevailing winds, and
depending on whether a liner is present, waste piles can also be significant
sources of soil contamination and subsequent air emissions. Waste pile
controls that may reduce wind erosion and entrapment of participates include
windscreens and other enclosures; construction of piles with their length
perpendicular to the prevailing winds; use of foams or other coverings; and
use of dust suppressants.
In the case of spills or leaks from above-ground tanks and containers,
the highest potential for releases of volatile and semi-volatile organics
occurs Immediately after the release or spill. The rate and amount of
emissions will depend on the size of the spill, the chemical and physical
properties of the spilled material, and atmospheric conditions. After the
spill, migration of contaminants through the soil and in the ground water can
provide a long-term source of volatile emissions. The rate of transfer of
subsurface gases to the atmosphere by this mechanism is dependent on the
physical properties of the soil matrix (porosity, density, and moisture
3-8
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content) and on climatic conditions, Including rainfall, temperature,
barometric pressure, and wind speeds. Frequently, the emitting surface
becomes depleted of contaminants and acts as a barrier to Inhibit further
emissions. When the surface .1s disturbed during remediation, the emission
rate may then Increase substantially.
Transport of partlculates and contaminated soils can occur through wind
erosion, which has the potential to disperse contaminants and provide a long-
term, arearwide source of air emissions. The potential for wind erosion
depends on atmospheric conditions such as temperature, rainfall, and wind
speed, and on the physical state of the waste.
3.2.4 Containers
The extent of emissions from above-ground containers and tanks depends on
the age and structural Integrity of the container or tank and the physical
state and chemical characteristics of the waste 1t contains. In the event of
a spill, the extent of air emissions depends on waste volume and
characteristics, and on environmental conditions such as direction of
prevailing wind and wind speed.
The primary source of emissions from open, above-ground tanks and
containers 1s through volatilization from the free liquid surface.
Sublimation of sol Ids from open tanks or containers is generally a minor
source of volatile and semi-volatile emissions. Depending on the amount and
the nature of the wastes contained in closed tanks and containers, regular
venting may also be a source of volatile and semi-volatile emissions,
especially If the tank' is filled and emptied.
Tanks and containers that are old, or that have been subject to unusual
or repeated chemical and mechanical stresses, are more likely than new tanks
to lose their structural Integrity and release contaminants to the
environment. Massive container failures provide an Immediate source of
volatile emissions to the atmosphere from the spill area, and will generally
3-9
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contaminate surface and subsurface soils and ground water. Subsurface
contamination provides a long-term source of contamination via lateral and
vertical diffusion of subsurface gas through the overburden.
In addition to the potential for gaseous emissions, contaminated surface
soils and particulate wastes exposed through spills may be transported from
the site via wind erosion. The potential for wind erosion of particulates is
highest In areas of dry soils and high average wind speeds. Otherwise, the
potential 1s low. Once transported away from the site, particulates provide a
long-term source of air emissions.
3.3 REMEDIATION SOURCES
3.3.1 Soil Handling
Remedial action at almost any Superfund site will Involve soil
.excavation, transportation, dumping, storage, or grading. The soil may also
have to be screened to remove rocks, trees,.drums, etc. prior to undergoing
treatment. All of these operations have the potential to cause particulate
emissions and waste volatilization.
A potential point source of volatile emissions from remedial soil
handling operations is through breaching the Integrity of buried tanks and
drums through excavation operations. The potential for volatile emissions
through this mechanism Increases at uncontrolled disposal sites where records
of the location of buried tanks and drums have not been maintained. Enhanced
emissions of volatile and semi-volatile organics may also occur through
removal of overburden, exposing volatile wastes, and through facility soil
handling operations such as grading, dumping, and transportation.
All of these operations have the potential to cause particulate emissions
as well as volatile emissions. Generally, once contaminated soil is
excavated, It Is transported by truck to storage piles. Emissions of
contaminated soil particles and solid wastes will occur at all phases of soil
3-10
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handling operations. Their magnitude will depend on wind and weather
conditions, particle size and mass, soil type, and the amount of vehicular
traffic at the site, size and activity of waste piles, the presence or absence
of covers on trucks and piles, and the extent of onslte contamination. Once
partlculate emissions are mobilized through these mechanisms, which may
transport them away from the site, where they have the potential for
Intermedia transfer through surface water runoff or ground-water Infiltration.
3.3.2 Air Strippers
In air stripping, a counter-current flow of air and contaminated water is
used to strip volatile organic contaminants from water. Specified water and
air flow rates, tower configurations, and residence times are used to maximize
transfer of volatile organics from the liquid phase to the gas phase.
The primary source of volatile and semi-volatile emissions from air
stripping 1s the air stripper exhaust. In the-absence'of a pollution control
device, the extent of-volatile emissions from this source will depend on the
concentration of volatlles in the contaminated water, the Henry's law constant
of the contaminants, water temperature, air temperature, air/water contact
time, and air/water ratio. If an emission control device, such as a condenser
or a carbon adsorption filter, Is present on the air stripping tower, the
extent of volatile emissions will depend on its efficiency.
Other potential sources of air emissions from air stripping Include
holding or treatment tanks where contaminated water is in direct contact with
air, and fugitive emissions from connecting valves, pumps, and pipes. The
magnitude of volatile 'emissions from open holding tanks is dependent upon the
concentration of volatile organics In the water, volatility of the
contaminants, surface area of the exposed water, degree of agitation of the
water surface, and the residence time of water in the tank. In general,
fugitive volatile emissions from closed sources such as pipes and valves are
not significant since the wastewater they contain is relatively dilute.
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Since air stripping Is a treatment method for contaminated water
(primarily contaminated ground water), participate emissions are not a concern
with air stripping. However, drilling of wells designed to collect
contaminated ground water have a small potential for mobilization of
contaminated soil particles. Ground-water recovery wells are also a
potential, although minor, source of volatile emissions.
3.3.3 Thermal Treatment
The most common type of thermal treatment Is Incineration,and the
following discussion primarily relates to Incineration. However, emerging
technologies such as low temperature thermal stripping also have significant
potential for emissions of organic compounds.
Incineration 1s a process that uses controlled combustion to oxidize
materials to less toxic products, and to significantly reduce waste volume.
It requires maintenance of-excess oxygen in the combustion chamber to ensure
complete combustion of organic materials to C02, H20, SOX, NOX, KC1, HBr, and
HP. Emission control devices are commonly used on incinerators to reduce
emissions of acid gases, particulates, and other materials. The incinerator
types most commonly used for hazardous waste destruction are rotary kiln,
multiple hearth, fluidized bed, and liquid Injection.
The largest point source of both volatile and particulate emissions from
incinerators is stack exhaust. Incinerator stack exhaust generally contains
carbon monoxide, particulates, metals, nitrogen oxides, acid gases such as
SOX, HC1, HBr, and HF, products of Incomplete combustion, and the fraction of
waste not combusted at all. , Waste characteristics observed to affect
incinerator emissions include the physical state of the waste, moisture
content, particle size, thermal content, and chemical composition. Likewise,
operating characteristics such as waste feed rate, temperature, residence
time, excess air rate, facility size and type, atomization, and control device
efficiency also affect stack emissions.
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Since metals are not destroyed 1n Incinerators, they are released as a
component of stack gas, remain In the ash, or are removed In any control
devices present. Depending on their chemical characteristics, they are either
volatilized In the combustion chamber or remain 1n the solid phase. Volatile
metals such as mercury, selenium, antimony, cadmium, and lead tend to leave
the Incinerator In the stack gas (as vapor) or condense onto particles In the
stack gas stream, while less volatile metals such as nickel and chromium tend
to remain 1n the Incinerator bottom ash.
Partlculate emissions may originate from the waste feed, the auxiliary
fuel, or the combustion air. The extent of part1culate emissions Is strongly
affected by waste and fuel compositions, Incinerator type and operation, and
effectiveness of air pollution control devices.- Partlculate emissions consist
of Inorganic salts and metals that either pass through the system as solids or
vaporize In the combustion chamber and recondense as solid particles In the
stack gas. High molecular weight hydrocarbons may also contribute to
partlculate emissions through self-nucleatlon, dehydration by Inorganics, and
adsorption onto Inorganic oxides.
Formation of nitrogen oxides (NOX) tends to Increase with combustion
temperature. Excess air and high heat releases also contribute to NOX
formation. Emissions of SOX, HC1, HP, and HBr, depend on the sulfur,
chlorine, fluorine, and bromine content of the waste and fuel feeds, and the
efficiency of the pollution control device.
Fugitive emissions from Incinerator operations can be a significant
source of air emissions, and are sometimes more significant than stack
emissions. Fugitive emissions occur through leaking valve and pump fittings,
flanges, storage tanks, sampling and Instrument connections, and handling and
transfer operations. Fugitive emissions can be minimized through proper
design and operation and periodic inspections of incinerator facilities.
Fugitive emissions from collecting, transporting, and storing the waste prior
to Incineration may also be significant and must be considered.
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3.3.4 Soil Vaoor Extraction
Two systems exist to control the movement of subsurface gases: active
aeration (vacuum or positive pressure pumping) and passive venting. Active
aeration systems use positive pressure or vacuum pumping to bring gases to the
surface or divert them away from critical structures. Passive venting systems
allow natural pressure gradients to bring gases to the surface where they are
dispersed in the atmosphere.
Vacuum pumping systems use a series of vapor recovery wells, similar In
construction to ground-water monitoring wells, from which vapors are extracted
using a vacuum pump. Once extracted and collected, the vapors are usually
condensed and treated by methods such as carbon adsorption or Incineration.
Sources of volatile emissions from vacuum pumping Include Inadequate well
surface seals, and emissions from the pollution control device designed to
treat the recovered gas.
Positive pressure pumping Is not a gas collection technology, but rather
a method to divert subsurface gas from a critical area or structure. It
Involves Injecting pressurized air Into the ground to laterally displace the
subsurface gas. However, vertical as well as lateral displacement can occur,
causing gases to diffuse through overlying soils to the atmospheres. Passive
aeration systems make use of natural pressure gradients created through
temperature fluctuations, barometric changes, wind, and rainfall to slowly
move subsurface gases to the surface. If the concentration of volatiles In
the subsurface 1s significant, and the surface area over which they are
released to the air Is small, passive gas venting systems can be a significant
source of volatile air emissions. Environmental factors such as gravity,
pressure, temperature, wind, and rainfall; and soil parameters such as
porosity, density, and moisture content are more Important 1n passive rather
than active gas venting systems.
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3.3.5 Solidification/Stabilization
Solidification and stabilization processes are designed to reduce the
hazard potential of a waste by converting It to Its least soluble, mobile, or
toxic form. The most commonly used solidification/stabilization techniques
are Portland cementation and pozzolanlc cementation, but other techniques
Include thermoplastic micro-encapsulation, organic polymer binding, and 1n-
sltu vitrification.
The two most commonly used solidification/stabilization techniques
Involve mixing a waste slurry with either Portland cement or a pozzolanlc
material such as fly ash, cement kiln dust, lime kiln dust, or hydrated lime.
The resulting material has a low permeability, high structural Integrity, and
Improved resistance to leaching. The potential for air emissions from this
final material 1s very low. However, several steps 1n the
solidification/stabilization process are potential sources of volatile and
particulate air emissions.
These steps include loading wastes into the mixing bin, adding the
solidification material, mixing together the waste and solidification material
(sometimes with the addition of heat), removing the material from the mixing
bin, and replacing material at the site after processing. Both volatile and
particulate emissions are possible at each step in this process, depending on
waste characteristics, soil type and percent of moisture, and the
effectiveness of any emission control practices being used. The mixing step
Is generally the most important in terms of air emissions, and may account for
90+% of the emissions from stabilization. Common emission control practices
for solidification/stabilization techniques are enclosure of the waste mixing
area and apparatus, storage pile controls for raw materials, and enclosure of
the binder preparation area. In the absence of these controls, air emissions
depend on the volatile organic content of the waste particle size of the soil
or waste; meteorological conditions such as wind speed, direction of
prevailing winds, and amount of precipitation; and site activities such as
excavation, dumping, and storage in piles.
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3.4 POST-REMEDIATION SOURCES
3.4.1 Post-Rememdiation Sources - Landfills
Air emission sources for landfills after remediation are similar to those
for landfills before remediation, with several Important differences. Area
sources of gaseous and parti oil ate emissions are likely to be less significant
after remediation. For example, post-remediation landfills are not likely to
have high-level soil or ground-water contamination, which can be a significant
source of volatile emissions at uncontrolled landfills. Also, diffusion of
volatiles through the landfill cover Is less likely after remediation, since
gas recovery and collection systems are more likely to be in place, as well as
better covers. Erosion of the cover and volatilization of the waste is a less
significant air emissions pathway at post-remediation landfills, since the
cover 1s more likely to be Inspected and maintained regularly.
3.4.2 Post-Remediation Sources - Lagoons
The primary air emissions sources from post-remediation lagoons 1s
volatilization of organics and aerosol formation from the free liquid surface.
Emissions from this source are likely to be significant unless control
techniques such as foams or temporary covers are in place. As with pre-
remediation lagoons, emissions from the free liquid surface are higher at
well-mixed lagoons, and at lagoons containing highly volatile waste.
Emissions from lagoons are also affected by environmental factors such as
temperature, atmospheric pressure, and wind speed.
Lateral and vertical diffusion of contaminants through the overburden is
not a significant source of air emissions at a lagoon unless there Is
widespread soil or ground-water contamination. At post-remediation lagoons
that have been recently constructed or retrofitted to meet minimum technology
standards, soil or ground-water contamination Is not likely, making the
likelihood of emissions from this pathway very low.
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As with unremediated lagoons, a potential source of emissions from
lagoons after remediation 1s wind erosion of contaminated soils and solid
residues from dry Impoundments or Impoundment berms. However, with proper
design and operation controls In place, this 1s not a significant air
emissions source.
3.4.3 Post-Remediation Sources - Soil Surfaces
The extent of volatile and particulate emissions from any post-
remediation waste piles will depend on whether the pile is enclosed, and on
whether erosion control mechanisms, such as wind screens, dust suppressants,
and foams or other coverings are in place.
Removal and/or treatment of contaminated soils will occur during site
remediation, so emissions from contaminated soil surfaces and diffusion of
contaminants from the soil surface to the ground water are not expected to be
a problem at post-remediation sites.
3.4.4 Post-Remediation Sources - Containers
The primary source of emissions from tanks and containers is
volatilization from the free liquid surface. Sublimation of solids is
generally only a minor source of volatile emissions. Remediation will
typically Involve emptying tanks and containers and removal of any unsound
structures, so volatile emissions arising from leaks or ruptures are less
likely.
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SECTION 4
APPLICATION OF AIR PATHWAY ANALYSES TO SUPERFUND
4.1 OVERVIEW
This section provides background Information that identifies various air
pathway analysis (APA) applications within the Superfund program. Recommended
procedures that define a step-by-step process to conduct these Superfund APAs
are provided in Section 5.
Air pathway analyses are applicable to every activity in the Superfund
process (as Illustrated in Figure 2). In the pre-remedial phase of Superfund
(Preliminary Assessments, Site Inspections, and Hazard Ranking System scoring)
this involves data-gathering activities to assess potential and observed air
releases (in the 1988 revisions to the HRS) and to provide Input to a
determination on whether the site is to be placed on the National Priorities
List (NPL). However, EPA has already developed various technical procedures
and guidelines which discuss characterization of the air pathway for pre-
remedial Superfund activities. Therefore, the emphasis within this section is
to identify appropriate APA applications for Superfund remediation and removal
activities including planned removal activities, as well as post-remedial
activities.
Superfund APAs have the following functional applications:
Input to the selection of remedial technology/action.
t Input to the preparation and implementation of health and safety
plans to protect onsite workers from potential air emissions.
Input to the conduct of risk assessments as well as to the
preparation and implementation of emergency contingency plans to
protect the offsite population from potential air emissions.
4-1
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APA --->
APA --->
APA --->
APA --->
Removal
Actions at
Non-NPL Sites
APA --->
APA --->
APA --->
APA --->
APA --->
SITE DISCOVERY
1
Preliminary
Assessments
I
Site
Inspections
NATIONAL PRIORITIES
.LIST (NPL)
Remedial Investigations/
Feasibility Studies
Records of Decision
Remedial Designs
i
Remedial Actions
Operation and Maintenance
Removal
Actions at
NPL Sites
<--APA
Figure 2. Superfund Air Pathway Analyses (APAs) Activity-Specific
Applications - Overview.
4-2
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Identification and consideration of Federal Applicable or Relevant
and Appropriate Requirements (ARARs).
Identification and consideration of State Applicable or Relevant and
Appropriate Requirements (ARARs).
These functional (or generic) applications are discussed in the following
subsections. Specific APA applications for Superfund remedial and removal
activities are presented in Section 4.2.
4.1.1 OnsIte Health and Safety
Potential air emissions at Superfund sites can pose a risk to the health
and safety of onsite workers. A decision maker such as an RPM or EPM is
confronted with the need to understand the nature of the air pathway risks in
order to set priorities and to allocate resources appropriate for control of
the risks. Therefore, APA results provide key input for the development of
site-specific health and safety plans.. 'Application of APAs can also be used
to provide field support to characterize the Impacts of potential or
accidental air releases. APA input to site health and safety plans includes
the following:
Site descriptions (wind/dispersion patterns);
Hazard evaluation (potential air emissions);
Delineation of work zones;
Selection of levels of protection;
Monitoring and sampling; and
Atmospheric hazard guidelines (action levels).
Standard site description input to the site health and safety plan
includes Information on climatology. Of particular interest are data which
can be used to characterize local wind and dispersion conditions. This may
involve obtaining available meteorological summaries from a representative
National Weather Service station or the conduct of an onsite meteorological
monitoring program. These meteorological data provide the basis to assess
4-3
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onsite air pathway hazards and to develop an appropriate health and safety
plan.
Hazard evaluation Involves Identifying potential air emission sources at
a Superfund site and estimating associated potential health and safety
Impacts. Therefore, monitoring and/or modeling may be necessary to
characterize onsite air concentrations and onsite worker exposure potential.
The hazard evaluation takes Into account baseline air concentrations at the
site as well as concentrations from the disturbed site (i.e., during
remediation). When evaluating emission data, It Is Important to consider the
time frame over which emissions take place. Therefore, 1t may be necessary to
examine the hazards from both short-term peak emissions and long-term average
emissions.
Delineation of work zones Is a primary component of the site health and
safety plan. The work zones are used to prevent or reduce the migration of
contamination. Therefore air pathway exposure factors are an Important
consideration in the site-specific delineation of these zones.
Air emission rate modeling, dispersion modeling, emission rate
monitoring, and/or air monitoring can provide a technical basis to define
potential air pathway exposures for baseline and disturbed site conditions.
These potential air pathway exposure conditions are considered when specifying
the work zones. In addition, the command post and other support facilities in
the Support Zone should be located upwind of the contaminated area.
Personnel must wear protective equipment when response activities involve
known or suspected atmospheric contamination; when vapors, gases, or
participates may be generated; or when direct contact with skin-affecting
substances may occur.
Selection of levels of protection Involves considering air pathway
exposure potential. Modeling and/or monitoring can be used to estimate these
potential exposures.
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To verify'that site control procedures are preventing the spread of
contamination at a Superfund site, a monitoring and sampling program 1s
generally established. This routinely Involves using direct-reading
Instruments and/or collecting air samples for particulate, gas, or vapor
analyses.
Atmospheric hazard guidelines (I.e., action levels) are established
within the site health and safety plan. These action levels provide a basis
to safeguard onsite workers at Superfund sites. If air monitoring results
exceed ambient criteria, then protective action procedures are triggered.
Additional Superfund program guidance regarding air pathway
considerations for site health and safety plans 1s provided in the following
documents:
US EPA, November 1984. Standard Operating Safety Guides, Memorandum
from William Hedeman, Jr.
US EPA, October 1985. Occupational Safety and Health Guidance
Manual for Hazardous Waste Sites Activities, Developed by
NIOSH/OSHANSCG/EPA.
OSHA, December 1986, Interim Final Rule for Hazardous Operations and
Emergency Response, 29 CFR 1910.120.
US EPA, December 1987. A Compendium of Superfund Field Operations
Methods.
4.1.2 OffSite Health and Safety
Potential air emissions from Superfund sites can also pose a risk to the
health and safety of people offsite. These potential off-site Impacts are an
integral component of the Superfund risk assessment process and should be
considered in evaluating baseline air emission from the undisturbed Superfund
site as well as from remediation activities. The need for air pathway
4-5
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exposure potential estimates Is addressed In the following Superfund
documents:
US EPA, January 1986 draft, Superfund Exposure Assessment Manual
US EPA, August 1986, The Endangerment Assessment Handbook
e US EPA, October 1986, Superfund Public Health Evaluation Manual.
The potential offsite Impacts of Superfund air emissions are also
addressed In Federal and State Applicable or Relevant and Appropriate
Requirements (discussed 1n Section 4.1.3).
For sites that have the potential for accidental air emission events, the
RPM/EPM should consider the application of air monitoring/modeling techniques
during site disturbance operations (I.e., exploration and remediation) which
have the potential for accidental air emission events. This approach (which
actually 1s an extended application of the onslte health and safety plan)
facilitates the early detection of these unplanned releases, estimation of
onslte/offslte Impacts, and provides Input for community emergency
prepardeness representatives.
Another Important role of Superfund APAs Is to support EPA community
relations efforts. This 1s especially appropriate for sites which are
perceived by the local community to have potentially unacceptable air Impacts.
The conduct of air monitoring/modeling studies can be used to provide early
warnings of actual releases. Also, the results of these air studies provide a
better basis to communicate the potential air pathway exposure potential to
the public and demonstrate EPA's responsiveness to the community's concerns.
4-6
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4.1.3 Applicable or Relevant and Appropriate Requirements (ARARs)
Superfund cleanup actions Include consideration of compliance with ARARs
of other environmental statutes as required by CERCLA Section 121. Federal
and State ARARs Include numerous complex provisions which frequently
necessitate the conduct of modeling studies and/or monitoring programs. ARARs
are critical to the evaluation of the air pathway, and EPA regional offices
need to quickly make ARARs determinations for a given site. These ARARs may
also limit air emissions and ambient concentrations at a Superfund site.
Thus, compliance with ARARs will directly affect the selection and design of
site-specific remedial/removal approaches Including the application of control
technology, as well as affecting the design of compliance monitoring during
remediation. Compliance with ARARs will therefore affect the project schedule
and costs. Therefore, RPMs and EPMs should Identify site-specific ARARs
during one of the initial tasks for a Superfund activity.
Sources of potential air pathway ARARs are summarized 1n Table 6. These
combinations of Federal and State ARARs involve numerous regulations which
vary as a function of source type. Federal ARARs that have been Identified
for Superfund air emission sources include the following:
Clean Air Act
Resource Conservation and Recovery Act
Occupational Safety and Health Act
Toxic Substances Control Act
Federal Insecticide, Fungicide, and Rodenticide Act
Atomic Energy Act
Uranium Mill Tailings Radiation Control Act.
The Clean Air Act is a complex law that is the basis for numerous
regulations that are potential ARARs for Superfund sites. Similarly, there
are several evolving regulations associated with the Resource Conservation and
Recovery Act.
4-7
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TABLE 6. SOURCES OF POTENTIAL SUPERFUND ARARs
FEDERAL
Clean Air Act
HMQS:
PM-10
502
CO
°3
"°x
Pb
NESHAP:
Asbestos
Benzene
NSPS:
VOC
PSO:
Anbient Inpact
BACT
MA:
Emission Off-sets
LAER
BCRA
40 CFR Z64
3004d
3004n
30040
Pre-Remedtat Ion Sources
Containers
Contaminated (Above-
Landfills Lagoons Soil ground)
X X
XXX X
X
X XX
X
X X
XXX X
X
XXX X
Remedial ton Sources
Soil Air
Handling Strippers Incinerators
In-Sttu Solidification/
Venting Stab 11 tat Ion
X X
X
X
XXX
X
X
X X
X
X
X
X
X
X
X
Post Remediation Sources
Container
Soil (above
Landfills Lagoons Surfaces ground)
X '
XX X
X XX
X
X
X X
XXX X
X
XXX X
00
(Continued)
-------
TABLE 6. (Continued)
3004u
Subpart 0
osm
T5CA
FIFHA
AEA
UHTRCA
STATE
Air Toxlea
Program:
SIP:
Odor/Fugitive
Oust Nuisances:
HUR - Air
Emissions:
Pre-Remedlatlon Sources
Landfills
X
Lagoons
X
Containers
Contaminated (Above-
Sol 1 ground)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Remediation Sources
Soil
Handling
Air In-SItu
Strippers Incinerators Venting
Solidification/
Stablllatlon
X
X
XXX
X
X
X
X
X
X
X
X
X
X
X
X
XXX
XXX
XXX
XXX
X
X
X
X
Post Remedl
Landfills Lagoons
X X
at Ion Sou
Soil
Surfaces
X
rces
Container
(above
ground)
X
X X
X
*
X X
X X
X
X
X
X
X
X X
X X
X X
X X
X
X
X
X
X
X
X
X
VO
Key:
PN-10 - Part leulite natter less than 10 nlcrons.
SO. - Sulfur dioxide
HA - (ton-attainment
CO - Carbon monoxide
0, - Oione
NO. - Nitrogen dioxide
VOC - Volatile Organic Compounds
TSCA - Toxic Substances Control Act
BACT - Best Available Control Technology
LAER - Lowest Achievable Enlsslon Rate
NAAQS - National Ambient Air Quality Standards
NESHAP - National Emission Standards for Hazardous Air Pollutants
FIFRA - Federal Insecticide. Fungicide, and Rodentlclde Act
NSPS - New Source Performance Standards
PSD - Prevention of Significant Deterioration
RCRA - Resource Conservation and Recovery Act
RCRA 40CFR264 - Fugitive Part leulate Emissions
RCRA 3004° - No Migration
RCRA 3004° - Location Standards
RCRA 3004" - Air Emissions Monitoring/Control
RCRA 3004" - Corrective Action
RCRA Subpart 0 - Hazardous Waste Incinerators
AEA - Atonic Energy Act
SIP - Site Implementation Plan for Clean Air Act
OSHA - Occupational Safety and Health Act
UMTRCA - Uranium Hill Tailings Radiation Control Act
-------
CERCLA Section 121(d)(2)(A) specifically limits the scope of State ARARs
to those that are promulgated and more stringent than Federal requirements.
In the case of State environmental programs which have been authorized by EPA
to be fully administered and enforced In lieu of the Federal program, the
stringency of the State requirements has already been established (I.e., the
State program must be at least as stringent, such that it provides for
compliance with the requirements of the Federal Act). A summary of principal
potential State ARARs which address the air pathway Is presented In Table 6.
A number of State and local air pollution control agencies have adopted
or are In the process of establishing programs to regulate what are generally
referred to as "toxic air pollutants." These programs differ from State to
State in the pollutants and sources regulated and the safe levels adopted.
Many states control toxic air pollutants through imposition of best
available control technology and then determine whether residual emissions
exceed State standards. Other States control toxic air pollutants through
acceptable ambient concentrations. In this process, the concentration of the
toxic pollutant Is estimated by modeling to a receptor, usually at the
fenceline of the source, and compared with the acceptable limit, the
definition of an "acceptable limit" varies widely from State to State. Many
States establish acceptable limits by applying a safety or uncertainty factor
to occupational standards (e.g., threshold limit values [TLVs]). These
factors vary from 1/10 to 1/420.
Other States regulate carcinogens using risk assessment principles. For
example, the risk to the most exposed individual in any population exposed to
a carcinogen (for an assumed 70-year lifetime) cannot exceed 1 x 10-5. A
typical State air toxics program will require a source to do the following:
4-10
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Identify pollutants of concern by comparing anticipated emissions
with the State air toxics 11st.
t Estimate emissions of toxic air pollutants, using procedures
approved by the State.
Estimate offsite concentrations, normally by air quality modeling
procedures approved by EPA or the State.
-Compare offsite concentrations to permissible State levels.
t If a new source Is likely to exceed the State limits, require
additional controls beyond what would otherwise be required.
In summary, State ARARs will generally Include more stringent ambient air
quality emission standards compared to Federal ARARs. But the most
significant aspect of State ARARs relevant to Superfund air emission sources
are the evolving State-specific air toxic programs.
Updated information on State air toxic programs can be obtained from the
EPA National Air Toxics Information Clearinghouse (the NATICH telephone number
1s (919) 541-0850). In addition, EPA-Superfund is currently preparing a
document, CERCLA Compliance with Other Laws Manual. When available, this
manual should be consulted for a more comprehensive discussion of ARARs.
4.2 Remedial and Removal Applications
Air pathway Impacts are evaluated and these results used as Input to
site-specific cleanup decision making by the RPH and EPN. Therefore, APAs are
conducted for various remedial and removal applications including the
following Superfund activities:
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Remedial Investigation/Feasibility Studies and Remedial Design
Records of Decision
0 Operation and Maintenance
Planned Removal Actions.
Following 1s a discussion of how APAs are used to support Superfund
declslonmaklng for each of these activities. Recommended procedures for the
conduct of these APAs are presented In Section 5.
4.2.1 Remedial Investigations/Feasibility Studies fRI/FSl and Remedial
Design
A1r pathway analyses are Involved 1n many of the standard RI/FS tasks.
The level at which the air pathway 1s evaluated 1s task dependent and ranges
from reviewing data collected In the field; evaluating ARARs; and evaluating
work plans, to performing atmospheric dispersion modeling; air quality
sampling; and meteorological monitoring.- Of the RI/FS tasks, APAs are applied
primarily to those listed below:
RI/FS Planning
i Field Investigations
t Risk Assessment
Bench and Pilot Studies
Remedial Alternatives Screening/Evaluation
Remedial Design.
An air quality analyst may be Involved In all of these RI/FS tasks to
assist the RPH/EPH 1n appropriate reviews and planning. Discussions of APA
Input to remedial design tasks are also Included in this section since these
tasks also support activities prior to onslte cleanup activities.
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RI/FS Planning --
The air pathway Is considered during RI/FS planning to ensure that the
air quality evaluation of the various remedial alternatives Is properly
addressed during succeeding tasks. Available air and supporting data
collected In the field are reviewed and analyzed with appropriate Input to the
plan preparation. If a preliminary risk assessment 1s to be performed for
this task, atmospheric dispersion and emission source modeling may be required
for the air pathway exposure assessment.
Field Investigations --
Air quality and emission source sampling may be required as part of the
media sampling program. Air modeling can be used to characterize sources for
a determination of onsite and offsite impacts and provide input for the design
of a monitoring program. In the event that exploratory excavations are
undertaken that could have significant releases impacting the air pathway,
realtime air support may be necessary. This can involve additional air
sampling, meteorological monitoring and dispersion modeling to characterize
and mitigate the impacts of potential air releases.
Risk Assessment --
This is another key RI/FS task with regard to the APA. The air quality
evaluation supports preparation and analysis of the public health and
environmental assessments for the various remedial alternatives. Atmospheric
dispersion and emission source modeling can be used with appropriate air
sampling data as input to an atmospheric exposure assessment.
Bench and Pilot Studies --
The APA for treatability (bench and pilot) studies primarily Involves
appropriate air quality and emission source sampling during the conduct of the
program. This would enable a review and evaluation of potential air impacts
and an assessment of necessary emission control technologies to be applied
during the remedial action.
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Remedial Alternatives Screening/Evaluation --
APA results can be used as Input to the remedial alternatives
screening/evaluation task to support analyses and comparisons of remedial
alternatives. Results of previous RI/FS assessments can be examined and
emission controls for the various remedial alternatives applied to ensure that
Impacts on public health and the environment are minimized. The air pathway
can be a significant consideration In the analysis and comparison of
alternatives.
Remedial Design --
APA Input to remedial design tasks Involves support to any bench and
pilot studies accomplished during the design phase and to required
environmental permitting. As with the RI/FS treatablllty studies, APA support
could Include air quality and emission source sampling and assessment of
emission control technologies. Permitting support Includes preparation of
air-related permits Including required documentation. This documentation may
Involve atmospheric dispersion modeling applications based on RI/FS
assessments. Environmental permitting requirements will be defined 1n the
ARAR determinations during the RI/FS and ROD activities.
4.2.2 Records of Decision
An APA Is conducted during the Record of Decision (ROD) to ensure that
the air pathway has been adequately evaluated 1n the process of selecting
site-specific remedial action. The APA to support the ROD Includes review of
the RI/FS air quality evaluation. The ROD documents this assessment by
discussing potential air Impacts, ARARs, and necessary mltlgatlve actions.
Any necessary air quality or emission source sampling planned to be conducted
during remedial actions or the operation and maintenance phase must also be
documented.
4-14
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4.2.3 Remedial Actions
Remedial activities at Superfund sites may expose Individuals located
both onsite and off site to air emissions of hazardous compounds. The APAs for
remedial actions provide the information to assess these emissions to
determine actual or potential Impacts. The specific air pathway evaluation
appropriate for a site-specific remedial action depends on two factors. The
first 1s whether any ARARs must be addressed. The second 1s whether the
potential for significant non-routine or routine air releases exists and, if
so, whether realtime evaluations of these releases during remedial activities
are necessary.
Evaluation of air-related ARARs 1s accomplished as an RI/FS activity and
documented in the ROD for the selected remedial alternative. An example could
be applicability of the Federal Clean Air Act requirements for remedial
alternatives such as onsite incineration of contaminated soils or air
stripping of contaminated groundwater. Should an ARAR trigger an air quality
monitoring program during a remedial action, the design and Implementation of
the program will be based on the ARAR and documented in the monitoring plan.
Realtime evaluations of air emissions are necessary if there is the
potential for significant releases or impacts during remedial actions.
Assessment procedures must be Implemented to evaluate when emergency actions
are required. A determination of the need for this realtime air impact
assessment capability could be accomplished using a screening atmospheric
dispersion modeling approach, which provides a conservative evaluation of
potential downwind impacts during various phases of the remedial action. The
RI/FS exposure assessment could also be used for this determination. A
realtime assessment of air concentrations at a Superfund site may involve a
combination of modeling and monitoring methods. This approach enables
appropriate site personnel to determine when pre-defined criteria or action
levels are reached or exceeded so that safeguards (including evacuations)
and/or mitigative actions can be implemented.
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4.2.4 Operation and Maintenance
The operation and maintenance stage after site cleanup may also Involve
compliance with ARARs or project requirements regarding monitoring emissions.
This could Include the conduct of emissions (source) monitoring or ambient air
monitoring. Source monitoring may Involve sampling of emissions from vents
while ambient air monitoring may be onsite and/or offsite. Collection of air
monitoring data may be necessary to ensure compliance requirements are met and
that operations are working properly.
Examples of remediated sites that may require monitoring Include passive
remediation* such as venting of a capped landfill, or a no-action alternative
involving a covered landfill. Both have the potential for volatile compounds
to migrate to the atmosphere through vents, cracks 1n the cap or soil, or
directly through porous soils. Additionally, any soils contaminated from
leakage of hazardous compounds may be suspended through wind erosion and
deposited at some downwind location. /Based on these site conditions, an air
monitoring program may be warranted. The air monitoring program may also
include meteorological monitoring.
4.2.5 Planned Removal Actions
Planned removal actions (assumed to be those where there is no immediate
threat to human health or the environment, but where expeditious removal is
warranted), like various remedial actions, may present the potential for
significant-air releases of hazardous compounds. A determination of whether
the potential exists for significant air releases during the activity can be
based on the application of dispersion models. If this potential exists, a
combination of modeling and monitoring methods can be used to provide realtime
assessments to characterize air releases and determine If emergency actions
are necessary.
4-16
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An example activity which may Involve significant air releases 1s the
excavation of burled drums which could be ruptured by equipment or which have
lost their Integrity due to rust or corrosion. Spills of material may then
cause Impacts via the air pathway. These procedures allow appropriate
personnel to determine when pre-defined criteria or action levels are reached
or exceeded so that safeguards (Including evacuations) and/or mltlgatlve
actions can be Implemented.
4.3 Application of Data Quality Objectives
Summary of the Data Quality Objective Process-
Data quality objectives (DQOs) are qualitative and quantitative
statements that outline the decision-making process and specify the data
required to support Superfund decisions during remedial response activities.
Superfund guidance for development of DQOs is presented in Data Quality
Objectives Development Guidance for Uncontrolled Hazardous Waste Site Remedial
Response Activities. (US EPA, October 1986).
The risk of an RPM/EPM making a wrong decision is related to data quality
and quantity. As the quantity and quality of data increase, the risk of
making a wrong decision based upon the information generally decreases. This
is not a true linear relationship since at some point the collection of
additional data or improvement of data quality will not significantly decrease
the risk of making wrong decisions. The risk of making a wrong decision
decreases as data quantity and quality increases, until it reaches a point of
diminishing returns, where additional data or increased quality of data does
not significantly reduce the risk of making a wrong decision.
The consequences of a wrong decision must be weighed by the RPM for each
major decision to be made during the remedial action process. Where the
consequences of a wrong decision carry significant public health, safety, or
environmental impacts, greater attention must be paid to obtaining the data
required to ensure that the decision is sound. Therefore, the objective of
the DQO process as applied to APAs is to ensure that all Superfund air
4-17
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monitoring/modeling results are sufficient and of adequate quality to support
site-specific decision making.
The DQO process Is characterized by three stages, as Illustrated in
Figure 3. Stage 1 of the DQO process provides the foundation for Stages 2 and
3. Stage 1 Is undertaken to define the types of decisions that will be made.
In Stage 1, all available Information on the site 1s compiled and analyzed to
develop a conceptual model understanding of the site. This model describes
suspected sources, contaminant pathways, and potential receptors. The model
facilitates Identification of decisions which must be made and deficiencies In
the existing Information. Stage 1 activities Include defining program
objectives and Identifying and Involving end-users of the data. Stage 1
results 1n specifying the decision-making process and forming an understanding
of why new data are needed.
Stage 2 results In the stipulation of criteria for determining data
adequacy. This stage Involves specifying the level of data certainty
sufficient to meet the objectives specified 1n Stage 1. Stage 2 Includes
selection of the sampling approaches and the analytical options for the site,
Including evaluation of multiple-option approaches to effect more timely or
cost-effective data collection and evaluation.
Stage 3 results In the specification of the methods by which sufficient
data of acceptable quality and quantity will be obtained to make decisions.
This Information 1s provided in documents such as the sampling and analysis
(S&A) plan or work plan.
Application of the three-stage DQO process to Superfund APAs 1s
Illustrated in Figure 4. Stage 1 involves the Identification of APA
recommendations presented In Volume I, collection and review of APA input data
(e.g., reviewing available air monitoring data) with participation by air
experts. Stage 2 Involves selection of the APA sophistication level,
selection of the APA approach (i.e., modeling and/or monitoring), and
4-18
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STAGE 1
IDENTIFY DECISION TYPES
Identify and Involve Data Users
Evaluate Available Data
Develop Conceptual Model
Specify Objectives/Decisions
STAGE 2
IDENTIFY DATA USES/NEEDS
Identify Data Uses
Identify Data Types
Identify Data Quality Needs
Identify Quantity Needs
Evaluate Sampling/Analysis Options
Review PARCC Parameters*
STAGE 3
DESIGN DATA COLLECTION PROGRAM
Assemble Data Collection Components
Develop Data Collection Documentation
* PARCC
(Precision, Accuracy, Representativeness, Completeness, and Comparability)
Figure 3. Data Quality Objectives - Process Overview.
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STAGE 1
IDENTIFY DECISION TYPES
Identify APA Guidelines Recommendations (Vol 1)
Collect and Review APA Input Data
Involve air experts for Potential Off-Site Impacts
Involve Both Air Experts and Safety Experts/
Industrial Hygienists for Potential On-site Impacts
STAGE 2
IDENTIFY DATA USES/NEEDS
Select APA Sophistication Level (Vol I)
Select APA Approach (Modeling Versus Monitoring)(Vol I)
Evaluate APA Uncertainty (Vol I)
STAGE 3
DESIGN DATA COLLECTION PROGRAM
Develop APA (Modeling/Monitoring) Plan (Vols II-IV)
Figure 4. Data Quality Objectives - Application to Air Pathway Analyses.
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evaluation of the uncertainty of APA results. Stage 3 involves development of
a site-specific modeling and/or monitoring plan for implementing the selected
APA approach.
Figure 4 Illustrates how the DQO process is integrated into the overall
APA process. The various components of each DQO stage in Figure 3 directly
correspond to the major components of the APA protocol presented in Figure 4.
Therefore, the APA recommendations and technical protocols presented in
Volumes I-IV are based on application of the DQO process.
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SECTION 5
OVERALL PROCEDURES FOR CONDUCTING AIR PATHWAY
ANALYSES FOR SUPERFUND
5.1 OVERVIEW
A recommended air pathway analysis (APA) procedure for Superfund is
illustrated in Figure 5 and discussed in Section 5.2. This procedure
identifies activity-specific and source-specific requirements for the conduct
of APAs. Recommendations are presented concerning the selection of the
appropriate type of APA for each type of activity or source. This selection
process includes evaluation of modeling versus monitoring for the collection
of data necessary to complete the APA. The Superfund APA procedure also
refers to Volumes II, III, and IV for specific procedures and information
needed to conduct the recommended APAs. These volumes contain information for
the conduct of emission estimation assessments, air monitoring programs, and
dispersion modeling studies.
A five-step standard format typically used for implementing the
procedures in Volumes II, III, and IV is given in Section 5.3. The material
in these volumes is summarized in Section 5.4 through 5.6. Combined with the
recommended Superfund APA procedure, this five-step standard format will
provide useful information to the RPMs and EPMs for planning projects. This
information should be sufficient for the RPM/EPM to identify the type of
APA(s) needed for a particular site/application.
The other three volumes in this series are frequently referred to in this
section. Their contents can be inferred from their titles:
5-1
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SUPERFUND AIR PATHWAY
ANALYSES PROCEDURE
(Volume 1 - Section 5.2)
Identification of Superfund Activity-
and Source-Specific Needs for an APA
Selection of Modeling Versus
Monitoring Techniques
References Volumes II - IV for Technical
Procedures for Conduct of APAs
- Emission Estimation
- Air Monitoring
- Dispersion Modeling
TECHNICAL PROCEDURES - STANDARD FORMAT
(Volume 1 - Section 5.3)
Specification of a Five-Step Process for
the Implementation of Recommended APA
Procedures for
Developing Baseline
Air Emission
Estimates (Vol II)
Procedures for
Identification
of Recommended
APAs for RPM/
EPM Planning
Purposes
Procedures for
Estimating Air Emission
Impacts from Remedial
Activities (Vol III)
Procedures for
Dispersion Modeling
and Air Monitoring
(Vol IV)
PROCEDURES FOR THE CONDUCT OF APAs BY TECHNICAL STAFF/CONTRACTORS
Figure 5. Procedures for Conducting Air Pathway Analyses for Superfund
Applications.
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Volume II - Estimation of Baseline Emissions At Superfund Sites.
t Volume III - Estimation of Emissions From Clean-up Activities At
Superfund Sites.
Volume IV - Procedures for Dispersion Modeling and Air Monitoring
5.2 RECOMMENDED SUPERFUND APA PROCEDURE
The recommended APA procedure for Superfund applications is summarized in
Figure 6. This procedure involves three segments. The first segment
identifies APAs that should be conducted during RI/FS, ROD, and Remedial
Design activities. The second segment identifies the APA that should be
conducted during remedial or removal actions. The third segment addresses the
APA for the post-cleanup (i.e. operation and maintenance) phase. Each segment
is described below. The applications of these APAs within the Superfund
process have-.been discussed in Section 4 of this document.
It is important to keep in mind the basic distinction between screening
and refined (or "in-depth") techniques, and that the distinction can mean
different things for different APA approaches. The basic distinction is that
a screening approach is inherently conservative, i.e., that the results
represent an upper bound of what the true results might be. Along with its
conservative nature, a screen is meant to be simple and utilizes as few
resources as possible. The purpose of taking a screening approach is, that if
air impacts are acceptable in spite of the conservative nature of the
analysis, then the resources needed to conduct a refined or in-depth analysis
are conserved.
For APA approaches involving predictive modeling, it is relatively easy
to conform to this concept of a screen. This is because both emissions models
and air quality dispersion models can be run in a conservative fashion,
selecting conservative parameters. For example, contaminant concentrations in
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CHARACTERIZE PRE-REMEDIATION
SOURCE BASELINE AIR
CONCENTRATIONS
(APA to be conducted
prior to remedial/removal
activities)
PREDICT AIR CONCENTRATIONS
FOR REMEDIATION/REMOVAL
SOURCES
(APA to be conducted prior
to remedial/removal activities)
PREDICT AIR CONCENTRATIONS FOR
POST-REMEDIATION SOURCES
(APA to be conducted prior to
remedial/removal activities)
RI/FS, ROD,
Remedial
Design APAs
CHARACTERIZE AIR CONCENTRATIONS
ASSOCIATED WITH REMEDIATION/
REMOVAL SOURCES
(APA to be conducted during
remedial/removal activities)
Remedial
Actions
APA
CONFIRM CONTROLLED SOURCE
AIR CONCENTRATIONS
(APA to be conducted after
remedial/removal activities
completed)
Operation
and
Maintenance
APA
Figure 6. Recommended Superfund Air Pathway Analyses - Procedure Overview.
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soil or water, or meteorological conditions, etc. can be assigned "worst-case"
values. When ambient measurements are Involved, either to assist 1n
estimating emissions or attempting to determine downwind impacts, it 1s no
longer possible to ensure that a screening approach is conservative. The
reason for this is that ambient concentrations are generally highly variable
in space and time, and the few single-point measurements that can be made with
monitors run the risk of Identifying a "false negative", I.e., missing maximum
concentrations altogether. Furthermore, Instruments commonly used for
screening such as total hydrocarbon analyzers, have detection levels well
above levels of concern for many pollutants.
An illustration of the risk of confusing the meaning of a screen is when
a total hydrocarbon analyzer is used to provide a "screening estimate" of air
Impacts. If no air impacts are detected in a site survey it is tempting to
conclude that air impacts are not of concern. However, a more accurate
conclusion is often that pollutants may have been present at undetectable
levels (yet still at levels that are cause for concern), or that emissions
were not high on the day of the survey, or that high concentrations were
present but not detected by the few point measurements taken, it is thus
important both to design screening analyses and to interpret screening results
in light of whether inherent conservatism can be assured.
5.2.1 RI/FS. ROD, and Remedial Design APAs
As indicated in Figure 6, APAs should be conducted for the following
three source types to support preparation of the RI/FS, ROD, and Remedial
Design:
Pre-remediation Sources;
Remediation Sources; and
Post-remediation Sources.
Baseline air concentrations at Superfund sites should be characterized
prior to remediation. This should Include the following sequence of events:
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Step 1 - Identify/evaluate potential ARARs governing the air
pathway for pre-remediation sources.
Step 2 - Determine pre-remediation emission rates.
t Step 3 - Estimate baseline air concentrations with a dispersion
model using emission rate estimates as Input.
Step 4 - Measure baseline air concentrations.
The use of predictive models to estimate emission rates and the resultant
air concentrations is a cost-effective basis for initially characterizing the
potential spatial and temporal variability of baseline air quality. The
estimates can be used to perform a preliminary risk evaluation for the air
pathway. It is imperative to consider both short-term (peak) exposures and
long-term (average) exposures for on-site and off-site receptors. The
estimation procedures can, if designed carefully, provide an upper-bound
estimate of air concentrations in the baseline case. Often it is desireable
to perform monitoring to evaluate model predictions but not always necessary
if the screening evaluation has been performed conservatively. This typically
involves an air monitoring program to obtain concentration measurements at
strategic locations. By using predictive models, the cost and duration of any
subsequent air monitoring can generally be reduced without sacrificing data
quality.
Cleanup emissions should also be evaluated to support RI/FS, ROD, and
Remedial Design applications. This should include the following sequence of
events:
Step 1 - Identify/evaluate potential ARARs governing the air
pathway for remediation and removal sources.
e Step 2 - Estimate emission rates of remediation/removal sources.
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t Step 3 - Estimate air concentrations associated with
remediation/removal sources using emission rate estimates
as input.
This approach does not require monitoring since the concentration estimates
are generated prior to remediation or removal for use in planning the eventual
remedial action.
Post-remediation air emission sources associated with operation and
maintenance activities should also be evaluated to support RI/FS, ROD, and
Remedial Design applications. The sequence of steps is:
Step 1 - Identify/evaluate potential ARARs for post-remediation
sources.
Step 2 - Estimate emission rates of post-remediation sources.
Step 3 - Estimate air concentrations associated with post-
remediation sources using emission rate estimates as
1nput.
The baseline emission estimation procedures presented in Volume II are
applicable to post-remediation sources as well, but require revised
source/waste characterization data as input. Again, the approach does not
require air monitoring since the concentration estimates are generated prior
to site cleanup operations to meet the planning needs.
5.2.2 Remedial/Removal Action APA
The second major segment of the Superfund APA procedure, as shown in
Figure 6, Involves the conduct of an APA in support of, and concurrent with,
remedial or removal actions. This should involve the following approach to
characterize the air concentrations associated with these remediation/removal
sources.
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Step 1 - Identify/evaluate potential ARARs governing the air
pathway for remediation/removal sources.
Step 2 - Perform routine air monitoring during the remedial/
removal operations.
Step 3 - Implement a combination of modeling and monitoring
techniques to characterize non-routine air releases.
Air monitoring is the primary approach to characterize routine emissions
during remedial or removal operations. This 1s because the primary purpose of
the APA at this stage of the Superfund process is to demonstrate, via actual
data, that air concentrations are less than health, safety, and environmental
criteria. However, a combination of monitoring and modeling techniques should
still be used to characterize unplanned releases. For this application,
dispersion modeling results can be used to extrapolate monitoring data
obtained at or near the source to downwind receptor locations of interest.
Emission modeling may also be useful for evaluating the effect on emissions of
changes in operations, waste characteristics, etcetera.
5.2.3 Operation and Maintenance APA
The third major segment of the Superfund APA procedure involves the
conduct of an APA to support the operation and maintenance phase of the
Superfund process. Therefore, the objective of the APA at this post-cleanup
phase is to confirm air Impact estimates that were obtained during RI/FS, ROD,
and Remedial Design activities. The need for such an APA is generally limited
to sources which have the potential to exceed ARAR air criteria if not
properly operated and maintained. The following APA approach should, as
warranted, be Implemented:
t Step 1 - Identify/evaluate potential ARARs governing the air
pathway for post-remediation sources.
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t Step 2 - Conduct emission monitoring pursuant to ARAR criteria.
Step 3 - Conduct air monitoring pursuant to ARAR criteria.
Again, because both pre-remediation sources and post-remediation sources
involve similar source types (i.e. landfills, lagoons, soil surfaces, and
containers), the application of Volume II procedures to this application is
appropriate.
5.3 TECHNICAL PROCEDURES
The general format which is the basis of each of the Technical Procedures
presented in Volumes II-IV is illustrated in Figure 7. This format provides a
common framework for the conduct of emission estimates, monitoring program,
and modeling studies. This approach consists of a five-step process as
follows:
Step 1 - Collect and review input.informalion;
Step 2 - Select APA sophistication level;
t Step 3 - Develop APA plan;
Step 4 - Conduct APA; and
Step 5 - Summarize and evaluate results.
Following Is a brief discussion of each of these steps.
Step 1 - Collect and Review Input Information
This Initial step addresses the process of collecting and compiling
existing information pertinent to previous site-specific APAs based on a
literature survey. It includes obtaining available source, receptor, and
environmental data. Once the existing data have been collected, compiled, and
evaluated, data gaps can be defined and a coherent monitoring plan or modeling
plan developed based on the site-specific requirements.
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SUFERFUND APA PROCEDURE RECOMMENDATIONS
Activity-specific recommendations
Source-specific recommendations
Modeling/monitoring recommendations
COLLECT AND REVIEW APA INPUT INFORMATION
Source Data
Environmental Data
Receptor/Population Data
EPA TECHNICAL
GUIDELINES
SELECT APA SOPHISTICATION LEVEL
Screening
Refined
DEVELOP APA PLAN
Technical Approach
Evaluate APA Uncertainty
Peer Review/
RPM Approval
CONDUCT APA
Quality Control
Documentation
T
SUMMARIZE/EVALUATE RESULTS
Data Review
Data Format
Comparison to Health Criteria
Consider APA Uncertainty' '
Yes
T
No
ADDITIONAL ANALYSES NEEDED?
Input to EPA
Remedial/
Removal
Decision
Making
Figure 7. Recommended Superfund Air Pathway Analyses Technical Procedures
General Format.
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Step 2 - Select APA Sophistication Level
This step Involves the selection of the APA sophistication level
considering screening versus refined monitoring and modeling techniques. This
selection process depends on program objectives as well as available resource
and technical constraints. Technical aspects that should be considered
include the availability of appropriate monitoring and modeling techniques.
Step 3 - Develop APA Plan
This step involves preparation of an APA plan. The APA should include
documentation of the selected technical approach (e.g., non-representative
input data, modeling inaccuracies and monitoring limitations). The
application of DQOs will be an important aspect in the development of an APA
plan. The selected approach should be based on EPA technical guidelines, as
available. The APA plan also facilitates peer review of the technical
approach and a formal process for approval of the APA by the RPM/EPM. The
peer review process may Involve EPA air experts or contractor support.
Step 4 - Conduct APA
This step involves the implementation of the APA plan developed during
Step 3. The emphasis during Step 4 1s to conduct the APA commensurate with
appropriate quality control measures and DQO criteria. This also involves
documentation of the APA process (to facilitate the QC process and establish
an information base that may be useful for APAs at other Superfund sites).
Step 5 - Summarize and Evaluate Results
This step involves reviewing data and evaluating APA results for
validity. Additional components of this step should include:
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0 data processing;
preparation of statistical summaries;
0 comparison of upwind and downwind concentration results; and
concentration mapping, if possible.
Estimates of data uncertainties based on instrument limitations and analytical
technique Inaccuracies should also be obtained and used to qualify air
monitoring results. Results can be compared to ARAR air criteria and other
Superfund health and safety criteria. The results of Step 5 can also provide
input to the Superfund risk assessment process.
5.4 ESTIMATION OF BASELINE EMISSIONS
The following description of Volume II Is taken from a recent conference
presentation (Schmidt and McDonough, 1989). The overall objective of Volume
II is to assist RPMs or site managers in assessing the impacts on air quality
from the site in its undisturbed condition. Specifically, the manual is
Intended to:
Present a protocol for selecting the appropriate level of effort to
characterize baseline air emissions;
t Assist site managers in designing an approach for estimating
baseline emissions;
Describe technologies useful for developing site-specific baseline
emission estimates (BEEs), which are defined as emission estimates
from disturbed and undisturbed sites and are necessary for
evaluating a no-action alternative and for evaluating potential
emissions during clean-up activities; and
Help site managers select the appropriate technologies for
generating site-specific BEEs.
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5.4.1 Protocol for Baseline Emission Estimates
A protocol Is presented in Volume II for generating BEEs. While not all
sites Mill require BEEs, the first three steps in the protocol should be
Implemented to see if BEEs are necessary for a given site. The protocol is a
recommended guideline; the level of effort that is required or the need to
develop BEEs for individual sites must be determined on a case-by-case basis.
Step 1 - Define the APA Objective
CERCLA and SARA legislation highlight the basic objectives for all
remedial Investigations. Simply stated, these objectives are to provide data
that are "necessary and sufficient" to characterize the "nature and extent" of
contamination on site. As the first step of the protocol to assess baseline
emissions, site-specific objectives should be developed; this will generally
occur simultaneously with the performance of Steps 2 and 3 (data collection
and review) of the protocol. Among the types of information that can be
reviewed and used to develop site-specific APA objectives are: waste
characteristics; distribution of the waste; location of population and
community concerns; technical feasibility; and program resources.
Step 2 - Site Scoping
The second step in the development of BEEs is collecting available
information about the site. This should be a quick, straightforward
information search, involving but not limited to the collection of records,
reports, shipping manifests, newspaper clippings, and information from
interviews with people living close to or affiliated with the site. For NPL
sites, data should be available from the preliminary assessment and site
inspection conducted prior to inclusion on the NPL. The type of Information
to be collected parallels, for the most part, the factors considered in
creating the objective.
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Step 3 - Evaluate Available Site Data
The existing site Information should be evaluated to determine the
potential for air pathway contamination. If It Is determined through this
assessment that the site poses no potential for air pathway contaminant
migration, then no further evaluation of the baseline emissions is required.
The site manager must record the basis for this decision and include these
data in the site investigation documentation. In most cases Insufficient
Information will be available at this stage, and further work will be
warranted. If air emissions are a potential concern, the next step of the
protocol (site screening study) should be implemented to provide additional
information to make a judgement regarding the potential for air emissions from
the site. At this point the site-specific APA objectives should be reviewed
to ensure they are still realistic, attainable, and applicable.
Step 4 - Design and Conduct the Site Screening Study
Designing a site screening study to assess the air emissions potential
involves the selection of an air emissions measurement/assessment technology.
The four broad categories of measurement/assessment technologies include:
Direct emissions measurement;
Indirect emissions measurement;
t Air monitoring/modeling; and
Emissions (predictive) modeling.
Each technology can be further categorized according to its level of
complexity as screening (quick and simple) or in-depth (very detailed).
The activities necessary to design and conduct the site screening study
are:
Determine the feasibility of obtaining the screening data (identify
any site factors that may limit this activity);
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Select appropriate tracer species, screening technologies, and
appl1cable equlpment/1nstrumentatlon;
Design the site Inspection technical approach and test plan,
Including the quality assurance/quality control (QA/QC) program.
Make sure that all units of a combined site are studied;
t Circulate the site screening approach for review and ensure the
screening addresses the site-specific objective(s);
t Modify the site screening program, as necessary;
Conduct the site screening study and document the findings; and
Determine If the site screening study was adequate to characterize
the air contamination migration pathway and if detailed BEE data are
necessary. If detailed BEEs are necessary, initiate the in-depth
site characterization study. If not, document the site Inspection
survey results and the basis for discontinuing the APA.
Step 5 - Design and Conduct the In-Deoth Site Characterization
The activities to design and conduct an in-depth study are similar to
those described for the screening APA except that In-depth assessment
technologies rather than screening technologies are used.
5.4.2 Summary of Baseline Air Emission Measurement Techniques
The recommended technologies are organized into four generic categories:
direct emission measurement technologies, indirect emission measurement
technologies, air monitoring/modeling technologies, and emissions (predictive)
modeling technologies, and in-depth assessment technologies. The screening
technologies provide some level of air emission assessment but may not
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accurately represent the site's potential for air emissions. The in-depth
assessment technologies are much more rigorous and generally provide a more
accurate estimate of the potential for air emissions from the site. Screening
technologies are typically used in the site inspection stage of the remedial
investigation (RI), whereas in-depth assessment technologies are typically
used during site characterization.
The types of volatile or particulate species that can be measured by the
technologies are essentially unrestricted; their measurement depends on the
sampling media selected and analysis technique rather than the emission
measurement technology. However, few of the technologies are applicable to
both volatile and particulate emission rate measurement.
Direct Emission Measurement Technologies
Direct emission measurement technologies are often the preferred
technologies for investigating the air pathway. The technologies generally
consist of isolating or covering a small section of the site surface or
subsurface using a chamber or enclosure. The concentration of emissions
produced by the isolated surface is measured within the chamber or from an
outlet line. These concentration measurements, along with other technology-
specific parameters, are then used to calculate an emission flux or relative
concentration valve. The emission flux (rate per area) can generally be
related to an emission rate for the entire source.
The cost of the direct emission measurement technologies varies
considerably. However, most of the technologies are cost-effective, allowing
for several measurements in a given day. Real-time instruments can be used
with all the direct technologies to provide immediate data for decision-making
during the sampling program, and for the relative ranking of the emission rate
at locations across the site. This procedure can be used to reduce the number
of samples requiring laboratory analysis by screening for those samples with
significant concentrations.
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Direct emission measurement technologies, as a class of assessment
technologies, are generally preferable to other classes of technologies
because they have been proven to be a cost-effective approach for obtaining
emission rate and concentration data and they avoid the necessity of modeling
to develop BEEs. Direct emission measurement technologies and equipment are
generally relatively simple and straightforward.
Indirect Emission Measurement Technologies
Indirect emission measurement technologies generally consist of measuring
the atmospheric concentration of the emitted species and then applying these
data to an equation (air model) to determine the emission rate. Many of the
equations were developed to determine downwind concentrations resulting from
stack emissions. For area emission sources, the source is treated as a
virtual point source or line source.
The in-depth technologies are very similar as all Involve clusters of
ambient air samplers positioned very close to the emission source. The
concentration profile technique involves a vertical array of samplers directly
over the source. The transect technique Involves vertical and horizontal
arrays of samplers within the downwind plume. The boundary layer technique is
a simplified version of the transect technique and involves several downwind
samplers, each at a different height.
A disadvantage of indirect emission measurement technologies is that the
results are highly dependent on meteorological conditions, interacting source
patterns, and uncertainties Inherent in the dispersion equations. The
indirect technologies require meteorological monitoring to properly align the
sampling systems and to analyze the data following sample analysis. Changing
meteorological conditions significantly affect the efficiency of collecting
useful data. Unacceptable meteorological conditions may invalidate much of
the data collected, requiring an additional sampling effort. The technologies
also may produce false negative results if the emitted species are present in
low concentrations which are below the sampling and analysis detection limits,
or if upwind sources cannot be fully accounted for. The technologies also may
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not be feasible at some sites where the source area is excessively large, or
where insufficient space exists downwind of the source to set up the sampling
array without disturbance of the air flow pattern by obstructions (e.g.,
buildings, tanks).
The types of volatile and participate species that can be measured by the
technologies are essentially unrestricted, they depend on the sampling media
selected and analysis technique rather than the emission measurement
technology.
Indirect emission measurement technologies generally do not provide
significant data on the emission rate variability for different locations
across a site. This is because the emission concentration is measured
downwind of the site after some atmospheric mixing. The technologies
generally do not allow for the evaluation of individual contaminated areas at
the site unless the areas are separated from one another and are not located
upwind of one another.
The costs of the indirect emission measurement technologies vary
considerably. The screening technologies are relatively simple and straight-
forward to implement, and require minimal labor and analytical costs. The in-
depth technologies are complex and require considerable equipment, labor, and
analysis costs. All of the technologies are subject to data loss or sampling
delay due to inappropriate meteorological conditions.
Air Monitoring Technologies
Air monitoring technologies that measure the ambient air concentration
resulting from area emission sources are combined with air dispersion modeling
to calculate the area source emission rate. The primary difference between
indirect emission measurement technologies and air monitoring technologies is
the distance at which measurements are made downwind from the source.
Indirect measurements are made near the source or units of a combined site
(usually on site) and may be able to distinguish between multiple units within
a site, depending on the spacing between units. Air monitoring is generally
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performed at considerable distance downwind from the source and usually cannot
distinguish between multiple units within a combined site. Air monitoring
typically measures lower concentrations because the contaminant plume 1s
subject to additional air dispersion.
The first step to use the ambient air sampling data to develop emission
rate estimates Is to select an air dispersion model which accurately reflects
the site-specific conditions, Including regional and local terrain, typical
wind stability, etc. Guidance for selecting an appropriate model for the
Superfund source In question can be found in Volume IV of this series. The
models are used with air monitoring and meteorological monitoring data to
estimate emission rates.
Air monitoring and air dispersion models are used to determine the
emission rate through an iterative process. An emission rate is first
estimated for the area source. This estimated emission rate, along with
meteorological data collected during air monitor ing,-.1s. used to calculate a
predicted downwind concentration. The predicted concentration is then
compared to the measured downwind concentration. Based on this comparison,
the estimated emission rate is adjusted appropriately, and the process is
repeated until acceptable agreement is reached between the measured and
predicted downwind air concentrations. The success or failure of this
technique depends on designing the monitoring network appropriate for the
concentration gradients and averaging times of concern. Guidance contained in
Volume IV of this series can be consulted to determine what kind of network is
necessary.
Emissions fPredictive! Modeling
Emissions models have been developed to predict emission rates for a
variety of waste site types Including landfills without internal gas
generation, landfills with Internal gas generation (typically co-disposal
sites), open dumps, waste piles, spills, land treatment operations, aerated
lagoons, non-aerated lagoons, and lagoons with an oil film. These models are
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almost exclusively theoretical, and each model Is generally applicable to only
one type of waste site.
The predictive models can be used as screening or in-depth technologies.
Emissions models, used as screening technologies, use data that can be
obtained or calculated from information available in the literature, or can be
assumed with some level of confidence. Emission models, used as in-depth
technologies, require site-specific site and waste characterization data. The
selection of model Input sources (site-specific, literature value, or assumed)
should be based on the requirements of the decision-making process and the
level of resources available. Site-specific data should be used whenever
possible to increase the accuracy of emission rate estimates. Each model
requires estimating the emission rate of the individual components of the
waste; and then summing the emission rates to determine the overall emission
rate. For complex waste, application of the models is best performed on a
computer to speed the calculation. An emission flux can be calculated by
dividing the emission rate by the emitting area.
A wide variety of variables are associated with each of the predictive
models; however, a number of key inputs are required by many of the models.
These key inputs for landfills include: the vapor diffusion coefficient
through the soil or mass transfer coefficient across the air/soil boundary for
waste constituents; the physical size of the source expressed as area, length,
and/or width, depending on the model used; physical parameters of the landfill
cover, such as depth of cover, permeability, and soil porosity (total, air-
filled, and/or effective porosity); physical/chemical parameters of the waste,
including chemical composition, weight or mole fraction for constituents,
vapor concentration of constituents at the waste surface or within the soil
cover, and partial pressures of constituents; atmospheric conditions, such as
temperature, wind speed and direction, and barometric pressure; and estimates
of the soil gas velocity through the soil cover. The key Inputs for lagoons
include: mass transfer coefficients; physical/chemical parameters of the
waste, Including chemical composition, weight or mole fractions, partial
pressures, and Henry's Law Constants; physical dimensions of the lagoon
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surface; atmospheric conditions, such as temperature, and wind speed and
direction; layering of waste within the lagoon; and physical/chemical
parameters of a surface crust.
While all of these parameters can be estimated with varying levels of
confidence, it Is best, when possible, to collect site-specific data.
Physical/chemical measurements of waste constituent can be obtained from
sampling and analysis programs, although a records review Is advisable to
identify key constituents and ensure representative sampling. Likewise, a
sampling -and analysis program combined with a records search 1s desirable to
determine the physical size and shape of the source and the porosity and
permeability of any soil cover. Atmospheric conditions are easily obtained
from various weather services which can provide regional data; however,
collecting some site-specific meteorologic data to ensure representativeness
is desirable. Diffusion and mass transfer coefficients are typically
calculated based on the wastes' chemical composition and their known chemical
properties, such as Henry's Law Constants, although tabulated diffusion
coefficients are now available. The referenced literature includes suggested
methods for calculating the diffusion coefficients as well as some tabulated
data. Diffusion and mass transfer coefficient can also be determined
experimentally in the lab; however, disturbance of the waste and landfill
cover to obtain site-specific materials would probably introduce uncertainty.
Screening and In-Deoth Technologies
Volume II describes measurement technologies as "screening" and "in-
depth" .assessment technologies which can be used to support screening APA-
(Step 3 of the protocol) and detailed APA (Step 5 of the protocol),
respectively. Screening assessment technologies are listed and described in
Table 7 and In-depth assessment technologies are listed and described In Table
8. Applications for specific assessment technologies, as well as advantages
and disadvantages or limitations of these technologies, are provided. Volume
II provides discussion of these technologies so that an RPM could make a
decision on the selection and use of a technology for a site specific APA.
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TABLE 7. SUMMARY TABLE OF INFORMATION ON THE VARIOUS CLASSES OF ASSESSMENT
TECHNOLOGIES AND SCREENING ASSESSMENT TECHNOLOGIES
Class of Assessment
Technology
Application
Advantages
Disadvantages
Direct Emission
Measurement
Head Space Sampler
Head Space Sample In
a Bottle
Landfills and lagoons.
especially if
identification of BEEs
per units on a combined
site Is required.
All landfills; lagoons
(non-aerated) with
flotation device.
All landfills and
lagoons where you have
a sample of the waste.
High precision and
accuracy, measures
undisturbed BEE without
modeling, can
distinguish between
units if combined site.
Representative of
volatile emissions
potential.
Rapid screening
technology that is easy
to perform.
Heterogenoeous waste
will require higher
number of measurement
points for
representative BEE.
Sampling devices
required.
Representativeness must
be considered.
Can lose a significant
fraction of the
volatile species during
handling. Representa-
tiveness must be
considered.
t Indirect Emission
Measurement
Upwind/Downwind
Mass Balance
Real-Time Instrument
Survey
o Air Monitoring/
Modeling
Larger landfills and
lagoons and sites with
waste handling
activities, combined
sites.
Landfills and lagoons
(any area source).
Lagoons and some
landfills.
Landfills and lagoons
(any area source).
Landfills and lagoons
(any area source).
Upwind/Downwind
Landfills and lagoons
(any area source).
Assess BEE from an area
source, regardles sof
homogenisty and site
activity. Can be used
for inaccessible sites.
Broadly applicable and
can provide an estimate
of emissions.
Limited resources are
required.
Rapid, real-time data
that can be used to
Indicate emissions
potential.
Typically provides data
that represents air
concentrations the
comnunlty Is exposed to
(fence line).
Broadly applicable,
provides community
ambient concentration
data.
Limitations imposed by
modeling, techniques
are influenced by
meteorological
conditions, may not be
able to distinguish
between units of a
combined site or up-
wind Interference.
Single point ambient
measurements may not
represent the emission
source.
Requires concentration
data over time.
Inherent Insensltwity
due to low mass of
volatile species.
Highly variable,
quality control program
for analyzers required.
Limitations Imposed by
modeling, techniques
are Influenced by
meteorological
conditions, analytical
sensitivity may be a
limiting factor.
Low concentrations with
high variability.
measurement subject to
meteorological
influences.
5-22
(Continued)
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TABLE 7. (Continued)
Class of Assessment
Technology
Application
Advantages
Disadvantages
o Emissions Modeling
(Predictive)
Landfills and lagoons.
especially applications
with site-specific
Information.
- Closed landfills, no
gas generation.
- Closed landfills, gas
generatIon.
- Open landfills.
- Land treatment.
- Non-aerated lagoons.
- Aerated lagoons.
Provide rapid.
Inexpensive assessment,
particularly where only
a few species are of
concern. Model inputs
can be assumed or taken
from literature If
site-specific data Is
not available.
Same
Same
Same
Same
Sam
Same
Accuracy, precision
dependent on quality of
site-specific data or
assumptions. Most
models have limited
validation.
Same
Same
Same
Same
Same
5-23
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TABLE 8. SUMMARY TABLE OF INFORMATION ON THE VARIOUS CLASSES OF ASSESSMENT
TECHNOLOGIES AND IN-DEPTH ASSESSMENT TECHNOLOGIES
Class of Assessment
Technology
Application
Advantages
Disadvantages
Direct Emission
Measurement
Emission Isolation
Flux Chamber
Soil Probe
(Volatlles)
Downhole Emission
Flux Chamber
(Volatlles)
Landfills and lagoons.
especially If Identifi-
cation of BEES per
units on a combined
site Is required.
Landfills-active.
Inactive, soil
contamination, waste
piles: lagoons (non-
aerated) with flotation
on device.
Landfills-active,
inactive, soil
contamination, waste
piles; lagoons-berms
around lagoons, heavy
sludges.
Landfills-active,
Inactive, soil
contamination, waste
piles; lagoons-berms
around lagoons, heavy
sludges.
High precision and
accuracy, measures
undisturbed BEE without
modeling, can
distinguish between
units If combined site.
High precision and
accuracy, measures
undisturbed BEE without
modeling, can
distinguish between
units 1f combined site.
Can obtain a subsurface
disturbed BEE 1 to 10
feet below land surface
without excavation.
Can obtain a subsurface
disturbed BEE 1 to 100
feet below land surface
with a hollow stem
auger drill rig.
Heterogeneous waste
will require higher
number of measurement
points for represent-
ative BEE.
Heterogeneous waste
will require higher
number of measurement
points for represent-
ative BEE.
Heterogeneous waste
will require higher
number of measurement
points for represent-
ative BEE.
Layered or stratified
waste will require BEE
for each discrete
layer.
Vent Sampling
(volatlles)
Wind Tunnel
Measurement
(volatlles and/or
particulate matter)
Waste repositories with
passive or active
venting system, common
at municipal, and co-
disposal landfills.
Specialized for
particulate emissions
from waste piles and
solid surfaces.
landfills, lagoons
(non-aerated) with
flotation on device.
Simple BEE measurement
procedure.
BEE for partIculate
matter and/or volatlles
as a function of wind
speed.
Often difficult to
measure low gas flow
rates which causes
imprecision and
inaccuracy, Include
sampling schedule that
Identifies diurnal
variations/other
factors that influence
gas production.
Heterogeneous waste
will require higher
number of measurement
points for
representative BEE,
additional support
equipment needed to
produce simulated wind
speed.
(Continued)
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TABLE 8. (Continued)
Class of Assessment
Technology
Application
Advantages
Disadvantages
Indirect Emission
Measurement
Concentration-Prof11e
(volatlles)
Transect (volatiles/
participate matter)
Boundary Layer
(volatlles)
Larger landfills and
lagoons and sites with
waste handling
activities, contained
sites.
Lagoons, landfills-
large solid waste site
and contaminated soil.
Lagoons, landf111s-
large or small sites.
Lagoons, landfills-
large or small sites.
Assess BEE from an area
source, regardless of
homogentsty and site
activity. Can be used
for Inaccessible sites.
Specialized measurement
and modeling technique.
high precision and
accuracy for an
Indirect technique
Specialized measurement
and modeling technique,
can be used for
partlculate matter from
waste handling.
Specialized measurement
and modeling technique,
can be used for
partlculate matter from
waste handling.
Limitations Imposed by
modeling, techniques
are Influenced by
meteorological
conditions, may not be
able to distinguish
between units of a
combined site or up-
wind Interference.
Must meet meteor-
ological conditions of
technique, not well
suited for small waste
areas, sophisticated
support equipment
required.
Must meet meteor-
ological conditions of
technique, technique
Influenced by meteor-
ological conditions.
Must meet meteor-
ological conditions of
technique, technique
Influenced by meteor-
ological conditions.
« Air Monitoring/
Modeling
Concentration-Prof1le
(volatlles)
Transect (volatlles/
partlculate matter)
Boundary Layer
(volatiles)
Landfills and lagoons.
complete site
emissions, monitoring
at downwind distances
greater than indirect
emission measurement.
Not typically used for
downwind measurements.
Lagoons, landfills (any
waste site or waste
handling treatment for
total site emissions).
Lagoons, landfills (any
waste site or waste
handling treatment for
total site emissions).
Typically provides data
that represents air
concentrations the
conmunity is exposed to
(fence line).
None.
Generally applicable to
most situations.
Generally applicable to
most situations.
Limitations imposed by
modeling, techniques
are influenced by
meteorological
conditions, analytical
sensitivity may be a
limiting factor.
Modeling may not
predict emissions from
data taken downwind.
Limitations Imposed by
modeling, techniques
are Influenced by
meteorological
conditions, analytical
sensitivity may be a
limiting factor.
Limitations imposed by
modeling, techniques
are influenced by
meteorological
conditions, analytical
sensitivity may be a
limiting factor.
(Continued)
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TABLE 8. (Continued)
Class of Assessment
Technology
Application
Advantages
Disadvantages
Emissions Modeling
(Predictive)
Landfills and lagoons.
especially applications
with site-specific
Information.
AP-42 Oust Emissions
for Vehicles
(participate matter)
Covered Landfill
Models (volatlles)
Road dust.
Covered landfills.
Open Dump Models
(volatlles)
Open Landfills.
Lagoon Models
(volatlles)
Lagoons, with or
without aeration.
Provide rapid,
Inexpensive assessment,
particularly where only
a few species are of
concern. Model inputs
can be assumed or taken
from literature If
site-specific data Is
not available.
Established EPA-
approved mode1
Provide rapid,
inexpensive assessment.
Models can be selected
based on available
input data. Can
account for bio-gas
generation at co-
disposal sites.
Account for non-steady
state emission (I.e..
declining emission)
over time.
Provide rapid,
inexpensive assessment.
Models can be selected
based on available
data.
Accuracy, precision
dependent on quality of
site-specific data or
assumptions. Most
models have limited
validation.
Accuracy depends on
quality site-specific
data.
Accuracy, precision,
dependent on quality of
Input data. Do not
account for losses to
other pathways.
Accuracy, precision
dependent on quality of
input data. Do not
account for losses to
other pathways. Do not
account for bio-gas
generation.
Accuracy, precision
dependent on quality of
Input data. Do not
account for losses to
other pathways. Assume
constant source
strength over time.
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5.5 ESTIMATION OF EMISSIONS FROM CLEAN-UP ACTIVITIES
The following description of Volume III Is taken from a recent conference
presentation (Eklund and Summerhays, 1989). Volume III 1s Intended for
estimating air Impacts as part of the evaluation of alternative remedial
options (e.g. incineration versus air stripping versus removal). It
summarizes information obtained from a literature search. The manual can also
be used for estimating emissions once a specific remedial action has been
selected. For example, it can be used to estimate the air impact from
altering the rate of clean-up or changing some other key engineering parameter
for a given remedial technology. It also provides guidance on control
technologies.
The manual provides the important function of standardizing the air
pathway analysis (APA) for remediation of NPL sites, thereby ensuring that a
uniform and systematic approach is followed for the diverse universe of NPL
sites. The manual provides a step-by-step protocol for estimating air quality
emissions resulting from site mitigation. For each step, a three tiered
approach is presented. In order of preference these are:
1) Use of site-specific data;
2) Use of predictive contaminant transport models using site-specific
inputs; and
3) Use of tabulated default values for when site-specific information
is unavailable.
Therefore, emission estimates can be estimated despite limitations in the
knowledge of the site. Of course, the confidence of the emissions estimate
depends on the associated confidence of the inputs to the estimation
procedure. In general, the required information to develop an emission
estimate is: the volume of waste present, the average concentration of the
5-27
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given contaminant in the waste, and the form of the waste (liquid versus solid
versus sludge).
5.5.1 Potential Emissions Bv Source Type
The potential emissions of concern for thermal destruction, groundwater
stripping, soil vapor extraction, soils handling, and fixation/stabilization
are described In the following paragraphs.
Thermal destruction is an engineered process in which controlled
combustion is used to decompose the chemical structures of organic compounds,
thereby substantially reducing the volume and toxicity of the hazardous
components of the waste. A variety of thermal destruction technologies exist,
with various types of incineration being the most commonly used. Thermal
destruction technologies are required to show that they can achieve at least
99.99% destruction and removal efficiency for toxic organic compounds under
ideal conditions. Other pollutants which may be present in the incinerator
exhaust gas include trace metals, participate matter, carbon monoxide,
nitrogen oxides, sulfur oxides, and hydrogen chloride. In addition to stack
emissions, significant air emissions may result from fugitive losses arising
from handling of the waste feed and the ash and other by-products that are
produced.
Air stripping of ground water effectively transfers volatile organic
contaminants from the liquid-phase to the gas phase. Typically in an air
stripping tower, contaminated ground water is introduced at the top of the
tower, and passes down through packing media while air is forced through the
tower counter-current to the water flow. For volatile compounds, removals in
excess of 99.5% have been demonstrated. Emissions of semi-volatile organic
compounds may also be a concern. It is generally effective to treat the VOs
in the exhaust gas from the stripper using carbon adsorption or incineration.
5-28
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Soil vapor extraction (SVE), or in-situ venting, uses soil aeration to
treat subsurface zones of contaminated soil for volatile organics. Generally,
SVE systems consist of a network of vapor recovery wells connected to a vacuum
source. The wells are screened over the soil layer of interest. Make-up air
permeates down from the ground surface or may be injected to the subsurface
via an air intake well. Volatile organics are the main emission type, though
some semi-volatile compounds may also be extracted. Treatment after the
vacuum source by carbon adsorption or other means is typically possible.
Soils handling covers a wide variety of operations that may result in
area-wide sources of fugitive emissions. These include: excavation (backhoe,
dragline, bulldozer, etc.), short and long haul transport, dumping, grading,
and storage piles (both active and inactive). The primary emissions of
concern are particulate matter and volatile organics; metals or other toxics
present in the particulate matter may also be a concern at some sites.
Control technologies generally involve designing the remedial action plan to
minimize the opportunities for emissions tb occur and use of foam or water
sprays during remediation to temporarily reduce emissions.
Stabilization/solidification processes are currently being developed and
evaluated for hazardous waste applications. Stabilization processes reduce
the hazard potential of a waste by converting it to its least soluble, mobile,
or toxic form. The physical nature or handling characteristics of the waste
are not necessarily changed by the technique. Solidification processes
(encapsulation processes) bind the waste in a structurally sound, uniform
solid. For both processes, wastes are loaded into a mix bin and other
materials are added in either a batch or continuous process. Therefore, these
processes generally require removal of the soil/waste from its original
location. Emissions of concern are particulate matter and volatile
hydrocarbons. The latter emissions may be enhanced by the exothermic nature
of many of these processes.
5-29
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5.5.2 Screening Considerations
Basic considerations for making a gross estimate of emissions due to
remedial activities are given below. It 1s intended to be used as a screening
tool to assess whether emissions from remediation may be significant at a
given site, using a given remedial technology. Sites that have the potential
for significant emissions, based on this screening, should have their
emissions potential subsequently evaluated using the more precise estimation
procedures for each remedial technology given elsewhere. The screening
procedure is necessarily conservative, i.e., sites with any likelihood of
significant emissions are referred to the more precise, but more time
consuming, estimation procedures.
The necessity of evaluating air emissions for a given site is dependent
on the type of hazardous material(s) at the site, the size of the site, and
the proposed treatment options. The following information should be known to
initially assess the emissions potential of the site:
i Estimate the volume (m3), mass (kg), and type of waste material to
be treated;
t Estimate the concentration of VOCs, heavy metals, dioxins, asbestos,
and pesticides in the waste material (ug/g);
List the probable treatment options and control technologies; and
Estimate the operating rate for remedial activities.
Table 9 lists remedial options and their associated control technologies.
Typical operational rates and air emission values for various remedial options
are presented in Table 10.
5-30
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TABLE 9. CONTROL TECHNOLOGIES AVAILABLE FOR EACH REMEDIAL OPTION
Remedial Operation Contaminant
Control Technology
Incineration Hydrocarbons
Participate
Add Gases
NOX
Fugitives
Ground Water Stripping Hydrocarbons
In-s1tu Venting
Soils Handling
Excavation
Transportation
Hydrocarbons
Particulates,
Hydrocarbons
Participates,
Hydrocarbons
Afterburner, Operational (in-
furnace) methods
Venturl scrubber, Electrostatic
preclpltator, Ionizing wet scrubber,
Fabric filter (baghouse)
Spray dryers, Ionizing wet scrubber,
venturl scrubber
Catalytic reduction, Operational
(in-furnace) methods
Inspection/maintenance
Condensation
Carbon adsorption (disposable)
Carbon adsorption (regenerable)
Incineration
Condensation
Carbon adsorption (disposable)
Carbon adsorption (regenerable)
Incineration
Water sprays of active areas
Oust suppressants
Surfactants
Foam coverings
Water sprays of active areas
Dust suppressants
Surfactants
Road carpets
Road oiling
Speed reduction
Coverings for loads
(Continued)
5-31
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TABLE 9. (Continued)
Remedial Operation Contaminant Control Technology
Soils Handling (Cont.)
Dumping
Partlculates, Water sprays of active areas
Hydrocarbons Water spray curtains over bed during
dumping
Oust suppressants
Surfactants
Storage Partlculates, Windscreens and other enclosures
Hydrocarbons Orientation of pile
Slope of pile
Foam covering and other coverings
Oust suppressants
Grading Partlculates, Light water sprays
Hydrocarbons Surfactants
Stabilization/ Partlculates, Enclosure of mixing area/apparatus
Solidification Hydrocarbons Storage pile controls for raw /
materials
Enclosure of binder preparation area
Suction hood (in-situ treatment)
5-32
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TABLE 10. SUMMARY OF TYPICAL AIR EMISSION VALUES BY SOURCE TYPE
Remedial Option
Incineration
Air Stripping
In-sltu Ventilation
Excavat ton
Backhoe
Dragline
Scraper
Bulldozer
Grading
Transport
Unpaved Roads
Paved Roads
Dumping
Storage
Stabilization
Typical
Operation
Rate
650 n^/mln"
50.000.000 BTU/hr
3500 L/mln
0.15-0.85 m3/m1nd
900 m3/day
700 itrVday
340-610 m3/day
1100 m3/day
-
5 trucks/hr
5 trucks/hr
24-270 m3/day
-
-
Uncontrolled Emissions Controlled Emissions
PN VOC PM VOC
0.5-23 g/m3 0.1-500 ug/m3 34-110 mg/m3 -
0 5-50 kg/day6 0 50-100 ppmc
0 1-110 kg/day 0 50-100 ppmc
0.002-0.22 kg/ - -e -
metric ton
. -
.
-
0.03-5.4 kg/hr - -e
1.3 kg/VKT - -e -
0.022-0.15 kg/ - -e
VKT
0.005-0.16 kg/ - -e
metric ton
0.39-1.5 g/m2/ - -e
day
0.31-0.41 kg/ - -e -
metric ton
a£xhaust gas rate.
bAssume 1-10 mg/L pollutant.
C95-99X efficiency for gas streams of 1000-10.000 ppm VO. Multiple treatment units may feed a
single control system.
Exhaust gas rate per recovery well.
eAssume control efficiency of SOX.
Note: "-" Implies Insufficient data to generate typical value.
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No clear-cut rules-of-thumb exist for screening which remedial actions
are likely to have significant emissions and which remedial actions are not.
Only a quantitative evaluation of emissions and their impacts can show the
significance of a remedial action. Nevertheless, considerations based on
common sense may be used to make qualitative judgments of potential
significance. If any of the conditions below are met, then a more rigorous
review is recommended.
1. Off-site receptors are near (e.g., within 1 km) of the emission
source.
2. The contamination includes any volume of dioxins or areas containing
highly concentrated pesticides, volatile carcinogens, or asbestos,
and the material will be handled or exposed.
3. The total contamination (mass x concentration) of pesticides, toxic
metals, volatile carcinogens, or asbestos at the site is substantial
(e.g., exceeds 100 kg), and this material will be handled or
exposed.
4. The total contamination (mass x concentration) of VOCs at the site
is substantial (e.g., exceeds 1,000 kg VOCs), and this material will
be handled or exposed.
5. Volatile organic contaminants are to be treated by incineration,
groundwater stripping, or in-situ ventilation, and no emissions-
controls are to be used.
6. There is reason to believe the control technology will not be
effective for some toxic compounds present in the waste.
7. The anticipated operating rate is relatively large (e.g., >10 times
the values given in Table 10.
5-34
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Note that sites' with Insignificant Impacts on any off-site areas may still
have an Impact on the health and safety of on-slte workers, and appropriate
precautions should be followed.
5.5.3 Detailed Procedures
Simple equations are presented 1n Volume III for estimating emissions
from various remedial action alternatives. Predictive models are being
developed by EPA or Industry for all the emission sources discussed 1n this
paper, but none of the emission models are fully developed and validated at
this time. Two examples of detailed procedures are presented below, one for
organic emissions from incineration and one for organic emissions from air
stripping of ground water.
Incineration
RCRA mandates that the principal organic hazardous components be 99.99%
destroyed or removed. Additional requirements dictate a limit on particulate
emissions'of 180 rag/standard'm3 {0.08 grains/standard ft3). Similarly, for
wastes containing dioxins or polychlorinated blphenyls (PCBs), TSCA
requirements generally apply that dictate a destruction and removal efficiency
of 99.9999% of these pollutants.
A default approach to estimating emissions from thermal destruction of
hazardous waste 1s to assume that the requirements of RCRA and TSCA will be
exactly met. If emissions are to be estimated in a feasibility study or
otherwise prior to incinerator design, then this default approach may be the
only option for estimating emissions. After the incineration is designed,
three additional options for evaluating actual emissions more precisely may be
available. The first and most rigorous method for emissions estimation would
be to perform a trial burn on the waste in question or a similar waste and
sample the influent and effluent streams for the pollutant of concern. Where
this is not technically or economically feasible, a second approach using
theoretical or empirical equations correlating incinerator operating
parameters to pollutant emission rates is desirable. In the absence of
5-35
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applicable correlations, a third approach is to use data accumulated from the
various trial burns that have been conducted, and assume the results are
applicable to the site in question.
To estimate the uncontrolled emissions of organic compounds from this
unit, use the following procedure:
ER, - ((l-(DRE/100))/1000)(C,)(mJ (Eq. 1)
where:
ER, « emission rate for pollutant i (kg/hr);
ORE = appropriate ORE value (e.g., 99.99%);
IT^ - mass flow rate for waste feed (kg/hr); and
C, « waste feed concentration for pollutant 1 (g/kg).
Air Stripping of Ground Hater
Air stripping towers can achieve nearly complete removal of volatile
organics from ground water, so emissions estimates can be based on the rate at
which contaminants are being treated, i.e. concentration x flowrate. For
volatile organics, the emission rate can be estimated as:
ER, = (CMn)(Qfn)(10-6)(l-(CE/100))(RE/100) (Eq. 8)
where: ER, - emission rate for species i (g/min);
C, 1n - concentration of species i in influent ground water (ug/L);
Q1n - flow rate (L/min);
RE » removal efficiency (%); and
CE = control efficiency (%).
Default values of 99.5% removal efficiency and 1000 liters per minute flowrate
can be assumed if design specifications are unavailable.
5-36
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For semi-Volatile..organic compounds or inorganic contaminants, the
removal efficiency from air stripping may be assumed to be 0%. If site-
specific data are available, emissions can be calculated using Equation 10.
ER, o (C1.1nHQln) " (C1.outHQout) (fg. 1Q)
106
where: C, out = concentration of species i in effluent (ug/L); and
Qout = effluent flow rate (L/min).
Note that the flow rates of the influent and effluent streams will differ due
to evaporative losses in the air stripping tower.
Emissions are typically either treated by carbon adsorption or left
uncontrolled. If on-site incineration is practiced concurrently, then the
exhaust can usually be used as make-up air to the incinerator. Control
efficiency of.carbon adsorption systems will vary with the inlet gas VO
concentration, the type of VOs present, and the molecular weight of the
compounds. Assume that compounds with molecular weights less than 45 have a
control efficiency of 0% and compounds with molecular weights greater than 130
have a control efficiency of 100% (they may be permanently bound to the
carbon). For compounds with molecular weights between 45 and 130, assume that
inlet streams of 200-10,000 ppm VO can be treated with exhaust gas
concentrations of 50-100 ppm typically obtainable. Inlet streams with over
10,000 ppm VOs are candidates for liquid recovery techniques.
5.6 DISPERSION MODELING AND AIR MONITORING PROCEDURES
The following description of Volume IV is taken from a recent conference
presentation (Garrison and Cimorelli, 1989). Volume IV contains a five-step
procedure for carrying out an APA, and provides details on how to carry out
each step for each of the two major approaches, i.e., modeling and monitoring.
In the document, each approach is described in a separate section, but here,
5-37
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the two approaches are described together for each step. This Is meant to
highlight their similarities and differences. The five-step procedure is
intended to be consistent with the Superfund Data Quality Objective (DQO)
process, at least in a qualitative sense. Consistency is achieved by designing
the steps to focus initially on simple, conservative analyses and only
refining if previous steps indicate that it Is necessary. The quantitative
part of the DQO process involves setting numerical bounds on the degree of
confidence that one can place on the results of an analysis. It has always
been problematical for air analyses to specify numerical degrees of
confidence. EPA is examining the question of developing numerical DQOs for
air, but no results have been incorporated into Volume IV.
The five steps are as follows:
Step 1 - Review Existing Site Information/Develop APA Inputs;
t Step 2 - Select APA Sophistication Level;
t Step 3 - Develop APA Plan;
Step 4 - Conduct APA; and
Step 5 - Summarize and Evaluate Results.
These five steps are discussed in more detail below.
Step 1 - Review Existing Site Information/Develop APA Inputs
In this step information and data relevant to a site's potential air
impacts are obtained and reviewed, and inputs required for a modeling exercise
or monitoring program developed. This information can guide the analyst and
the site manager in developing a coherent, sensible APA involving the
appropriate mix of modeling and/or monitoring analyses. The level of detail
available for a given site can vary considerably; generally speaking, more
information will be available the longer the site has been under
investigation. It will probably be necessary at this stage for the air
analyst to develop information that is not already available. The information
consists of source and pollutant data, receptor data, and environmental data.
5-38
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Any previous APA results should also be reviewed for Information that may be
relevant to the current effort.
Source and Pollutant Data
The number and types of source located at the site should be Identified,
as well as the types of contaminants present and the potential for each
contaminant to be released to the atmosphere. The characteristics of the air
pollutant should be Identified (I.e., gaseous or partlculate, or a toxic
constituent adsorbed onto dust particles). For a modeling exercise, source
dimensions for area and volume sources, as well as stack parameters for stack
sources, need to be specified. Emission rates need to be specified as well,
which can be determined according to the procedures outlined In Volumes II and
III. Short-term maximum emission rates, as well as long-term averages, should
be developed, and an effort made to Identify emissions variability based on
the mechanisms that are active in producing emissions (e.g., soil handling,
meteorological conditions). It should be noted that due to the complexity of
the emissions mechanisms for some Superfund source types, that the process of
specifying an emission rate may in Itself involve a fairly complex protocol
and field measurements to measure emissions directly or to monitor and "back-
calculate" an emission rate based on an assumed concentration distribution.
Specific emission rates and source characteristics are not directly
relevant to a monitoring exercise; however, it is almost always advisable to
perform modeling as a part of designing the monitoring network. When
developing; information in preparation for monitoring, it is quite important to
know what concentrations of each pollutant are important, i.e., what are the
ARARs or risk levels that will determine whether a concentration is acceptable
or not. This will have a direct bearing on whether monitoring is possible or
not, and also on what type of monitoring approaches can be used. It 1s also
quite Important, both for modeling and monitoring, to know what averaging
times are important. Much of the risk assessment part of health analyses is
based on long-term averages, both for carcinogens and for systemic toxicants
for which reference doses have been established. If short-term effects are
important, however, the modeling and/or monitoring approach will have'to take
5-39
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that Into account. In particular, for a few very toxic chemicals, an
Instantaneous concentration above a certain level can cause Immediate adverse
health effects, even death. This will have a strong influence on the choice
of models and monitoring methods.
Receptor Data
A dispersion model can calculate concentrations at virtually any
location. Generally, a gridded receptor field is utilized in a model to
identify concentration gradients and maximum concentrations. Population data
in.the general vicinity of the site, and location of individual residences in
the immediate vicinity of the site, should be determined. Sensitive receptors
(e.g., hospitals, schools) should also be identified. This information can
help design a receptor grid and Interpret modeling results in terms of actual
exposures to maximum concentrations, and can help in a monitoring network
design by focusing on areas of greatest concern.
Environmental Data
This type of information consists generally of climatology, topography,
land use classification, and meteorology. Climatological data, especially in
the form of wind roses that identify the frequency of occurrence of wind
direction, can provide a baseline of information on general wind patterns that
may affect transport of pollutants from a site. Local topography can
dramatically influence pollutant transport. For example, a site located
downslope of an elevated terrain feature might be affected by density-driven
flows that have a pronounced diurnal nature. Topographic features can channel
and divert large-scale regional wind flow, such that the wind direction on-
site can be much different than measurements taken off-site. Land-use
classification affects whether the area should be modeled as "urban" or
"rural," a choice that must be made as an option in most dispersion models.
All of these factors can affect the design and siting of a monitoring program.
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Meteorological data Is a vital Input to a dispersion model. It 1s
Important to Identify early on 1n the process whether meteorological data
representative of the site 1s available. Data from the nearest National
Weather Service (NWS) station is generally the easiest to obtain; however, it
Is representative of a broad area only when the area Is relatively flat.
Without representative meteorological data, a modeling exercise will be driven
by "worst-case" conditions. Recalling the definition of a screen discussed
above, this is consistent with a conservative approach; however, lack of data
sharply limits- the options for refining a screening analysis. Because of
this, a program-to measure on-s1te meteorological data (unless NWS or other
available data can be considered representative) should always at least be
considered as soon after listing a site on the NPL as possible. A procedure
for developing an on-site data base 1s Included in Volume IV.
Step 2 - Select APA Sophistication Level
In this stage of the APA process, a decision is made as to what level of
sophistication will be employed in the analysis and what models and/or
monitoring techniques will be used. A modeling exercise will almost always
start out with a screening approach, and steps to refine the analysis are
taken only if screening results indicate unacceptable concentrations An
exception to this sequence of events might be to take a more refined approach
initially if the Input data are readily available and the additional effort
would not have a significant impact on resources.
Selecting a model is an important part of this step. For most Superfund
sources, the Industrial Source Complex (ISC) model, in its short-term (ISCST)
and long-term (ISCLT) versions, is directly applicable. The model can be run
in a screening mode for short-term predictions. Development of modeling
guidance is continuing and revisions should be investigated prior to
developing a modeling plan. For example, an effort is underway as a follow-up
to Volume IV to develop a long-term screen, i.e., an application of ISC for
long-term concentrations in instances when a site-specific frequency
distribution of meteorological inputs is not available. Additional reviews of
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1C are underway to examine and possibly modify the area source algorithm in
the model. This is particularly important for Superfund sources since many of
them are modeled as area sources. The updated version of EPA's screening
procedures (EPA, 1988c) for point sources contains a computerized version of
the document, called the SCREEN model, that can also find useful application
for Superfund sources.
The sequence of events in a monitoring exercise is different than that of
a modeling exercise; namely, that a "screening" monitoring approach is not
necessarily conservative. Nonetheless it is useful to think of monitoring in
terms of screening and refined approaches with a different meaning. Screening
monitoring techniques are generally associated with relatively high detection
levels (i.e., in the range of parts per million for gaseous contaminants) and
frequently provide near real-time results in the field. The detection levels
are often greater than levels that are of concern from a long-term exposure
perspective, and thus the usefulness of these techniques is limited to
situations where there is a desire to know if very large short-term
concentrations are present at a site.
Refined monitoring techniques most often provide high-quality.data at low
detection levels (typically ppb range for gaseous contaminants) through whole
air collection in bags or stainless steel canisters, or solid-adsorbent
collection followed by detailed laboratory analysis with turn-around time
measured in days to weeks. Refined screening techniques, such as field
portable GC analyzers or field laboratories, offer an approach in-between
screening and refined, but generally cannot provide the rigorous QA/QC
procedures or the degree of speciation available from a certified off-site
laboratory. A developing technology that does not require sampling is the use
of long path optical absorption techniques that use radiation in the infrared
or ultraviolet spectral regions and an interferometer to obtain absorption
spectra that can be interpreted to identify and quantify the presence of trace
gases.
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The choice of sophistication level depends very much on what levels of
detection will provide the site manager with meaningful Information, and on
what lead time 1s acceptable. Baseline assessments, for example, can often
wait for detailed laboratory analyses; on the other hand, air concentrations
monitoring during remediation need to be known In real-time so that decisions
on site activities can be made with full knowledge of air concentrations.
Step 3 - Develop APA Plan
An APA plan for a modeling exercise should be documented 1n a protocol
that describes how the analysis will be carried out. The protocol should
document what sources are to be modeled and how emissions will be calculated.
Source characterization, Including sizes and initial dispersion for area and
volumetric sources and stack parameters for point sources, should be
specified. Other important topics for the protocol are selection of
meteorological data, specification of a receptor grid, choice of model and a
detailed 11st of model options, and determination of background
concentrations. Preparation of a protocol 1s often overlooked, but the lack
of a protocol can lead to re-doing an analysis 1f Important details are not
considered.
A monitoring APA plan Includes several elements. Monitoring constituents
should be selected based on several factors, including the physical and
chemical properties of the pollutants, their toxicity and health effects, the
availability of monitoring techniques, and concentration standards. The
monitoring network design must be specified, including the number of sampling
sites, their location, the number of samples to be taken, and the duration of
the sampling effort. Meteorological monitoring should be Included in the
plan, to provide at least for measurement of wind speed and direction and
sigma theta (standard deviation of the wind direction, an indicator of
atmospheric turbulence). Additional parameters that should be considered are
temperature, temperature gradient, solar radiation and/or net radiation, and
precipitation. Finally, the monitoring plan should be documented 1n a QAPP.
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Step 4 - Conduct APA
This step Involves carrying out the selected APA through modeling or
monitoring or a combination of the two. Important elements of this step
Include ensuring that qualified personnel are conducting the APA, that all
QA/QC elements of the monitoring plan are being followed, and providing for
meaningful reporting and display of APA results. Modeling results can be used
to generate isopleths of concentration around a site. Superimposing the
isopleths on a site map is an extremely useful way to present results.
Steo 5 - Summarize and Evaluate Results
Monitored and/or modeled concentrations that are the end result of an APA
need to be evaluated to determine if applicable standards are met (or will be
met, in the case of projecting future concentrations). Data outputs from APA
should be evaluated to make this determination. If the APA is being conducted
during site remediation, turn-around time is critical so that decisions can be
made immediately on whether to stop or modify cleanup activities. The basic
decisions that need to be made as the result of an APA are as follows: 1) To
control a source further or modify an activity to reduce air emissions, 2) To
reject or modify a proposed remedial alternative based on its projected
impacts, or 3) To refine the APA by obtaining more accurate emissions
estimates or representative meteorological data, or utilizing a more refined
model.
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SECTION 6
REFERENCES
1. Eklund, B. and J. Summerhays, Procedures for Estimating Emissions
from the Clean-up of Superfund Sites. Presented at the 82nd Annual
Meeting of the Air and Waste Management Association, Anaheim, June
1989.
2. Ehrenfeld, J. and J. Bass. Evaluation of Remedial Action Unit
Operations at Hazardous Waste Disposal Sites. Pollution Technology
Review No. 110, Noyes Publications, Park Ridge, New Jersey, 1984.
434 pp.
3. Garrison, M.E., and A.J. Cimorelli. Procedures for Conducting Air
PathwaAnalyses at Superfund Sites. Presented at the 82nd Annual
Meeting of the?Air and Waste Management Association, Anaheim, June
1989.
4. Government Institutes, Inc. EPA Toxicology Handbook. ISBN No.
0-86587-142-6, Government Institutes, Inc., Rockville, Maryland,
1986.
5. National Institute for Occupational Safety and Health. Occupational
Safety and Health Guidance Manual for Hazardous Waste Site
Activities. (Prepared jointly by the National Institute for
Occupational Safety and Health, Occupational Safety and Health
Administration, U.S. Coast Guard, and U.S. Environmental Protection
Agency.) DHHS (NIOSH) Publication 85-115, Washington, D.C., 1985.
6. NUS Corporation. Procedures for Dispersion Modeling and Air
Monitoring for Superfund Air Pathway Analyses, U.S. Environmental
Protection Agency. RTP, NC 1989.
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7. Occupational Safety and Health Administration. Interim Final Rule
for Hazardous Operations and Emergency Response. 29 CFR 1910.120,
December 1986.
8. Radian Corporation. Procedures for Conducting Air Pathway Analyses
for Superfund Applications Volume II: Estimations of Baseline
Emissions from Superfund Sites. U.S. Environmental Protection
Agency, RTP, NC. 1989a.
9. Radian Corporation. Procedures for Conducting Air Pathway Analyses
for Superfund Applications Volume III: Estimation of Air Emissions
from Clean-up Activities at Superfund Sites. U.S. Environmental
Protection Agency, RTP, NC., 1989b.
10. 0. Randerson, Editor. Atmospheric Science and Power Production.
DOE/TIC-27601, U.S. Department of Energy, Washington, D.C., 1984.
11. Schmidt, C. and M.McDonough. Estimation of Baseline Air Emissions
at Superfund Sites. Presented at the 82nd Annual Meeting of the Air
and Waste Management Association. Anaheim, CA June 1989.
12. U.S. Environmental Protection Agency. A Compendium of Superfund
Field Operations Methods. EPA/540/P-87/001 (OSWER Directive
9355.0-14), Washington, D.C., 1987a.
13. U.S. Environmental Protection Agency. Compilation of Air Pollution
Emission Factors Volume I: Stationary Point and Area Sources,
Fourth Edition. EPA Publication No. AP-42, Research Triangle Park,
North Carolina, 1985a.
14. U.S. Environmental Protection Agency. Data Quality Objectives
Development Guidance for Uncontrolled Hazardous Waste Site Remedial
Response Activities. Washington, D.C., 1986a.
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15. U.S. Environmental Protection Agency. The Endangerment Assessment
Handbook, Washington, D.C., 19865.
16. U.S. Environmental Protection Agency. Field Standard Operating
Procedures #6 - Work Zones. OSWER Directive 9285.2-4, Washington,
D.C., 1985b. 19 pp.
17. U.S. Environmental Protection Agency. Field Standard Operating
Procedures #8 - A1r Surveillance. OSWER Directive 9285.2-3,
Washington, D.C., 1985c. 24 pp.
18. U.S. Environmental Protection Agency. Final Guidelines for
Carcinogen Risk Assessment. 51 FR 33992, September 24, 1986. 12
pp.
19. U.S. Environmental Protection Agency. Final Guidelines for the
Health Assessment of Suspect Developmental Toxicants. 51 FR 34028,
'September 24, 1986. 13 pp.
20. U.S. Environmental Protection Agency. Final Guidelines for the
Health Risk Assessment of Chemical Mixtures. 51 FR 34014, September
24, 1986. 12 pp.
21. U.S. Environmental Protection Agency. Final Guidelines for
Mutagenicity Risk Assessment. 51 FR 34006, September 24, 1986. 7
pp.
22. U.S. Environmental Protection Agency. Guidance Document for Cleanup
of Surface Impoundment Sites. OSWER Directive 9380.0-6, Washington,
D.C., 1986c.
23. U.S. Environmental Protection Agency. Guidance Document for Cleanup
of Surface Tank and Drum Sites. OSWER Directive 9380.0-3,
Washington, D.C., 1985d.
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24. U.S. Environmental Protection Agency. Guidance on CERCLA Compliance
with Other Environmental Statutes. OSUER Directive 9234.0-2,
Washington, D.C., 1985e. 19 pp.
25. U.S. Environmental Protection Agency. Hazardous Waste Treatment,
Storage, and Disposal Facilities (TSDF) - Air Emission Models.
EPA-450/3-87-026, Research Triangle Park, North Carolina, 1987b.
26. U.S. Environmental Protection Agency. Hazardous Waste Treatment,
Storage, and Disposal Facilities; Air Emission Standards for
Volatile Organics Control; Proposed Rule. 52 FR 3748, February 5,
1987c. 23 pp.
27. U.S. Environmental Protection Agency. Modeling Remedial Actions at
Uncontrolled Hazardous Waste Sites. OSWER Directive 9355.0-8,
Cincinnati, Ohio, 1985f.
28. U.S. Environmental Protection Agency. Quality Assurance/Field
Operations Methods Manual. OSWER Directive 9355.0-14, Washington,
D.C., 1986d.
29. U.S. Environmental Protection Agency. Remedial Action at Waste
Disposal Site Handbook (Revised) OSWER Directive 9380.0-4,
Cincinnati, Ohio, 1985g.
30. U.S. Environmental Protection Agency. Samplers and Sampling
Procedures for Hazardous Waste Streams. EPA-600/2-80-018,
Cincinnati, Ohio, 1980. 70 pp.
31. U.S. Environmental Protection Agency. Standard Operating Safety
Guides. OSWER Directive 9285.1-1B, Washington, D.C., 1984a.
32. U.S. Environmental Protection Agency. Superfund Exposure Assessment
Manual. OSWER Directive 9285.5-1 (Pre-Publication Edition),
Washington, D.C., 1988a. 157 pp.
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33. U.S. Environmental Protection Agency. Superfund Public Health
Evaluation Manual. EPA/540/1-86/060 (OSWER Directive 9285.4-1),
Washington, D.C., 1986e. 175 pp.
34. U.S. Environmental Protection Agency. Superfund Remedial Design and
Remedial Action Guidance. OSWER Directive 9355.0-4A, Washington,
D.C., 1986f.
35. U.S. Environmental Protection Agency. Superfund Removal Procedures
- Revision Number Three. OSWER Directive 9360.0-03B, Washington,
D.C., 1988b.
36. U.S. Environmental Protection Agency. Transfer, Storage, and
Handling Operations. Washington, D.C., 1987d.
37. U.S. Environmental Protection Agency. Userjs Guide to the Contract
Laboratory Program, OSWER Directive 9240.0-1, Washington, D.C.,
1984b, 114 pp.
38. U.S. EPA. Screening Procedures for Estimating the Air Quality
Impact of Stationary Sources. EPA-450/4-88-010, August 1988c.
39. Water Pollution Control Federation. Pretreatment of Industrial
Wastes. Manual of Practice No. FD-3, Washington, D.C., 1981, 159
pp.
40. Whelan, G., D.L. Stringe, J.G. Droppo, Jr., B.L. Steelman and J.W.
Buck. The Remedial Action Priority System (RAPS): Mathematical
Formulations. DOE/RL/87-09, Pacific Northwest Laboratory, Richland,
Washington, 1987.
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NOTICE TO THE READER - IF YOU WOULD LIKE TO RECEIVE
UPDATED AND/OR REVISED COPIES OF THIS VOLUME IN THE
NATIONAL TECHNICAL GUIDANCE STUDIES SERIES, PLEASE
COMPLETE THE FOLLOWING AND MAIL TO:
Mr. Joseph Padgett
U.S. Environmental Protection Agency
MD-10
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