United States
Environmental Protection
Agency
Office of Emergency and
Remedial Responce
Washington, DC 20460
EPA/540/1-89/001
March 1989
Superfund
S-EPA
Risk Assessment
Guidance for Superfund
Volume II
Environmental
Evaluation Manual
Interim Final
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EPA/540/1-89/001
March 1989
Risk Assessment
Guidance for Superfund
Volume II
Environmental Evaluation Manual
Interim Final
Office of Emergency and Remedial Response
U.S. Environmental Protection Agency
Washington, DC 20460
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Disclaimer
The policies and procedures set forth here are intended as guidance to Agency and other government
employees. They do not constitute rule making by the Agency, and may not be relied on to create a
substantive or procedural right enforceable by any other person. The Government may take action
that is at variance with the policies and procedures in this manual.
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Preface
This document is part of a two-manual set entitled
Risk Assessment Guidance for Super fund. One
manual, the Environmental Evaluation Manual,
provides guidance for ecological assessment at
Superfund sites; the other, the Human Health
Evaluation Manual, provides guidance for health risk
assessment at these sites. Guidance in both areas is
needed so that EPA can meet the requirements of
sections 121 (b) (1) and (d) of the Comprehensive
Environmental Response, Compensation, and
Liability Act (CERCLA), namely, that selected
remedial actions be protective of human health and
the environment. This risk assessment guidance also
can assist EPA in complying with other CERCLA
directives. For example, Section 121 (c) requires
future reviews to ensure that human health and the
environment continue to be protected at sites where
contaminants remain after remedial actions were
completed.
The Risk Assessment Guidance for Superfund
manuals were developed to be used during the
Removal and Remedial Investigation/Feasibility
Study (RI/FS) processes at Superfund sites. The
analytical framework and specific methods described
in the manuals, however, may also be applicable to
evaluations of hazardous wastes and hazardous
materials for other purposes. For the RI/FS process,
these manuals are companion documents to EPA's
Guidance for Conducting Remedial Investigations
and Feasibility Studies Under CERCLA (October
1988), and users should be familiar with that
guidance. The two Superfund risk assessment
manuals were developed with extensive input from
EPA workgroups composed of both Regional and
Headquarters staff. These manuals are interim final
guidance; final guidance will be issued after the
revisions to the National Oil and Hazardous
Substances Pollution Contingency Plan (NCP),
proposed in December 1988, become final.
Although environmental evaluation and human
health evaluation are different processes, they share
certain information needs and generally will use
some of the same chemical and other data for a site.
Planning for both evaluations should begin during
the scoping stage of the RI/FS, and site sampling and
other data collection activities to support the two
evaluations should be coordinated. An example of
this type of coordination is the sampling and analysis
of fish or other aquatic organisms; if such sampling is
done properly, data can be used in assessing human
health risks from ingestion of fish and shellfish and
in assessing impacts to, and potential effects on, the
aquatic ecosystem.
The two manuals in this set have somewhat different
target audiences. The Environmental Evaluation
Manual primarily addresses Remedial Project
Managers (RPMs) and On-Scene Coordinators
(OSCs), who are responsible for ensuring a thorough
evaluation of potential environmental effects at sites.
The Environmental Evaluation Manual is not a
detailed "how-to" type of guidance, and it does not
provide "cookbook" approaches for evaluation.
Instead, it identifies the kinds of help that RPMs or
OSCs are likely to need and where to find that help.
Then it describes an overall framework for
considering environmental effects. A detailed
discussion of environmental evaluation methods may
be found in Ecological Assessments of Hazardous
Waste Sites: A Field and Laboratory Reference
Documnet (EPA/600/3-89/013), published by EPA's
Office of Research and Development. The Human
Health Evaluation Manual, available in 1989,
provides a basic framework for health risk
assessment at Superfund sites. The health evaluation
manual is addressed primarily to the individuals
actually conducting health risk assessments for sites
and who are frequently contractors to EPA, States, or
gDtentially responsible parties. It is also targeted to
PA staff, including those responsible for ensuring a
thorough evaluation of human health risks (i.e.,
RPMs). The Human Health Evaluation Manual
replaces a previous EPA guidance document, The
Superfund Public Health Evaluation Manual, or
SPHEM (October 1986), which should be used until
the Interim Final Human Health Evaluation Manual
is available. The new manual incorporates lessons
learned from application of the earlier manual and
addresses a number of issues raised since publication
of the SPHEM.
in
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Environmental Evaluation Manual
EPA Work Group
EPA Headquarters
Office of Emergency and Remedial Response:
Office of Waste Programs Enforcement:
Office of Solid Waste:
Office of Solid Waste and Emergency Response:
Office of Air and Radiation:
Office of Federal Activities
Office of General Counsel:
Office of Information Resource Management
Office of Marine and Estuarine Protection:
Office of Policy, Planning and Evaluation:
Office of Research and Development:
Office of Toxic Substances:
Office of Underground Storage Tanks:
Office of Water Enforcement and Permits:
Office of Water Regulations and Standards:
Office of Wetlands Protection:
David Bennett
Karen Burgan
David Charters
Steve Golian
Sandra Lee
Arthur Weissman
Jack Schad
Sherry Sterling
Alec McBride
Ossi Meyn
Tom Pheiffer
Gary Snodgrass
Phillip Ross
Judy Troast
Joseph Freedman
Barbara Lamborne
Bob Zeller
Dexter Hinckley
Diane Niedzialkowski
Craig Zamuda
Thomas Baugh
Will LeVeille
Susan Norton
Jim Gilford
Iris Goodman
Martha Segall
Suzanne Marcy
John Maxstead
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EPA Regional Offices
Region 1:
Region 2:
Region 3:
Region 4:
Region 5:
Dorothy Allen Region 6:
Michael Bilger
Susan Svirsky
Peter Grevatt Region 7:
Mark Sprenger
Jeff Pike Region 8:
Ron Preston
Elmer Akin Region 9:
Russ Todd
Pamela Blakely Region 10:
Wayne Davis
Allison Hiltner
Pranas Pranckevicius
Pat Hammack
Jon Rauscher
Fred Reitman
Robert Fenemore
Robert Morby
Jay Silvernale
Greg Baker
Greg Eckert
Pat Cirone
Wayne Grotheer
Evan Hornig
EPA Laboratories
Athens, GA:
Cincinnati, OH:
Corvallis, OR:
Duluth, MN:
Gulf Breeze, FL
Las Vegas, NV:
Robert Ambrose
Cornelius Weber
Hal Kibby
Nelson Thomas
Hap Pritchard
Chuck Nauman
Narragansett, RI: Gerald Pesch
Other Agencies
National Oceanic and Atmospheric Administration: Sharon Christopherison
Thor Cutler
Ken Finkelstein
Alyce Fritz
John McCarthy
Oak Ridge National Laboratory:
U.S. Fish and Wildlife Service:
U.S. Forest Service (Arcata, CA):
Lee Barclay
Peter Escherich
Hart Welsh
VI
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Contents
Page
Preface iii
Environmental Evaluation Manual-EPA Work Group v
Figures •. ix
Tables ix
Acknowledgments x
1. Introduction J
1.1 What is Ecological Assessment? 1
1.2 Ecological Assessment in the Superfund Process 2
1.3 Who Should Read this Manual? 3
1.4 Organization of the Manual 3
2. Statutory and Regulatory Basis of Ecological Assessment ?
2.1 CERCLA/SARA Authorities 7
2.2 The National Contingency Plan 8
2.3 RemovalActionGuidance 9
2.4 Remedial Investigation and Feasibility Study (RI/FS) Guidance 10
2.5 CERCLA Compliance with other Environmental Statutes (ARARs) 11
3. Basic Concepts for Ecological Assessment 15
3.1 Objects of Study in Ecology 15
3.2 Types of Ecosystems 16
3.3 Effects of Contaminants on Ecosystems 21
3.3.1 Reduction in Population Size 21
3.3.2 Changes in Community Structure 21
3.3.3 Changes in Ecosystem Structme and Function 22
3.4 Factors Influencing the Ecological Effects of Contaminants 22
3.4.1 Nature of Contamination 22
3.4.2 Physical/Chemical Characteristics of the Environment 24
3.4.3 Biological Factors 25
4. The Role of Technical Specialists in Ecological Assessment 29
4.1 Site Characterization 30
4.2 Site Screening and Identification of Information Gaps 31
4.3 Advice on Work Plans 31
4.4 Data Review and Interpretation 32
4.5 Advice on Remedial Alternatives 33
4.6 Enforcement Considerations 33
Vll
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Contents (continued)
Page
5. Planning an Ecological Assessment 35
5.1 Determination of Need, Objectives, and Level of Effort
for Ecological Assessment 35
5.2 Evaluation of Site Characteristics 36
5.2.1 Nature and Extent of Contaminated Area 36
5.2.2 Sensitive Environments 37
5.3 Contaminant Evaluation 37
5.3.1 Identification and Characterization 37
5.3.2 Biological and Environmental Concentrations 38
5.3.3 Toxicity of Contaminants 38
5.3.4 Potential ARARs and Criteria 40
5.4 Potential for Exposure 40
5.5 Selection of Assessment and Measurement Endpoints 41
5.5.1 Ecological Endpoints 42
5.5.2 Evaluation of Potentially Affected Habitats 43
5.5.3 Evaluation of Potentially Affected Populations 44
5.6 Sampling and Analysis Plan 45
5.6.1 Field Sampling Plan 45
5.6.2 Quality Assurance 46
6. Organization and Presentation of an Ecological Assessment 49
6.1 Specify the Objectives of the Assessment 49
6.2 Define the Scope of the Investigation 4.9
6.3 Describe the Site and Study Area 4.9
6.4 Describe Contaminants of Concern .5.0
6.5 Characterize Exposure 50
6.6 Characterize Risk or Threat 52
6.7 Describe the Derivation of Remediation Criteria
or Other Uses of Quantitative Risk Information 56
6.8 Describe Conclusions and Limitations of Analysis . 56
Vlll
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Figures
Page
1.1 Relationship between health and environmental evaluations. 4
1.2 Logical organization of this manual 5
3.1 Levels of organization of matter 15
3.2a Examples of typical food chains, 17
3.2b A greatly simplified terrestrial food web 18
3.3 Thermal stratification of a north temperate lake 20
6.1 Example of study areamap 51
6.2 Graphic display of contaminant concentrations. 52
6.3 Map display of contaminant concentrations. 53
6.4a Map display of toxicity test results 54
6.4b Map display of toxicity test results 55
6.5 Graphic Display of Species Diversity Indices 57
6.6 Graphic Display of Trophic Structure 57
Tables
1.1 Additional EPA Documents to be Consulted 2
3.1 Forest Food Chain for DDT 27
6.1 Example of Presentation of Criteria Exceedences 56
IX
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Acknowledgments
This manual was prepared by The Cadmus Group, Inc., for the U.S. Environmental Protection
Agency, Office of Solid Waste and Emergency Response through Contract No. 68-03-3348. Project
Directors and principal authors were Michael J. Dover (Cadmus), Patricia Mundy (EPA) and John
Bascietto (EPA).
Many individuals contributed to this document. We especially wish to acknowledge the assistance
provided by Dr. James Gillett of Cornell University, who served as a review consultant to Cadmus
and offered many valuable comments that were incorporated into this version of the manual.
Other Cadmus contributors include Dr. David Burmaster (consultant to Cadmus), Beverly Brown
Cadorette, Scott T. Campbell, Gene E. Fax, Joseph P. Foran, Kenneth W. Mayo, and Theodore R.
Schwartz.
This manual is the product of an extensive planning and review process within EPA. The EPA
Work Group, which also included representatives from the National Oceanic and Atmospheric
Administration (NOAA) and the U.S. Fish and Wildlife Service (USFWS), conferred several times
to discuss the organization, content, and policy implications of the document. The Work Group
members reviewed and provided extensive comments on each of several drafts of the manual. In
the early stages of the project, members of the Region 111 Bioassessment Work Group - Dr. David
Charters (EPA Environmental Response Team), Dr. Alyce Fritz (NOAA, Region III), and Ronald
Preston (Environmental Services Division, EPA Region III) - provided invaluable planning
assistance.
The authors were privileged to have as a reference a draft version of a manual prepared by the
Ecological Risk Assessment Subcommittee of the EPA Region I Risk Assessment Work Group. The
document, entitled Guidance for Ecological Risk Assessments, was issued as a Draft Final in
February 1989. Concepts and some wording of the Region I document were adapted for use in
several parts of this manual. We gratefully acknowledge the Subcommittee's cooperation (in
particular, Susan Norton of the Office of Health and Environmental Assessment) in making their
draft available to us.
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Chapter 1
Introduction
This manual is intended to help Remedial Project
Managers (RPMs) and On Scene Coordinators (OSCs)
manage environmental evaluation of Superfund
sites. Environmental evaluation is an important part
of the Remedial and Removal processes. Since RPMs
and OSCs have primary responsibility for managing
these processes, it is important for them to under-
stand basic ecological concepts and how they relate to
hazardous waste remediation.
Environmental evaluation at Superfund sites should
provide decision makers with information on threats
to the natural environment associated with
contaminants or with actions designed to remediate
the site. Decisions such as those made on Superfund
sites are necessarily made with varying degrees of
uncertainty. The environmental evaluation is
intended to reduce the inevitable uncertainty
associated with understanding the environmental ef-
fects of a site and its remediation, and to give specfic
boundaries to that uncertainty. However, it is
important to recognize that environmental
evaluations are not research projects they are
not intended to provide absolute proof of dam-
age, nor are they designed to answer long-term
research needs. Not all sites will require
environmental evaluations. Indeed, many are in in-
dustrial areas with little if any wildlife. For those
sites that do need to be evaluated, the RPM or OSC is
responsible for determining the level of effort
appropriate to the decisions required for each site.
The purpose of this document is to provide a scientific
framework for designing studies, at the appropriate
level of effort, that will evaluate pertinent ecological
aspects of a site for the Remedial and Removal
processes. These ecological aspects include:
- Living resources at or near the site requiring
protection,
- Effects of the site's contaminants on those
resources, and
- Effects of remedial actions.
This manual does not offer detailed descriptions of
specific field or laboratory methods; these are
discussed in a companion publication prepared by
EPA's Office of Research and Development,
Ecological Assessments of Hazardous Waste Sites: A
Field and Laboratory Reference Document. The
Superfund Exposure Assessment Manual describes
methods for estimating and modeling the fate and
transport of contaminants in the environment. Other
information that should be used to supplement this
manual may be found in these and the other publica-
tions listed in Table 1.1.
The manual is based on the assumption that RPMs
and OSCs will obtain assistance from technical
specialists as early as possible in the assessment
process, and is designed to facilitate communication
between the RPM or OSC and these specialists.
Support for designing and evaluating ecological
assessments is available from technical assistance
groups in those EPA Regions that have formed them.
In other Regions, ecologists may be found on the
staffs of other EPA offices and contractors, or on the
staffs of other Federal agencies. The role of these
specialists is discussed in greater detail in Chapter 4.
1.1 What is Ecological Assessment?
Although "environmental evaluation" has been a
commonly used term for this process, ecological
assessment is a more precise description of the
activity, and will be used throughout this manual.
Ecological assessment, as discussed in this manual, is
a qualitative and/or quantitative appraisal of the
actual or potential effects of a hazardous waste
site on plants and animals other than people and
domesticated species. It is important to emphasize,
however, that the health of people and domesticated
species is inextricably linked to the quality of the
environment shared with other species. Information
from ecological studies may point to new or
unexpected exposure pathways for human popula-
tions, and health assessments may help to identify
environmental threats.
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Table 1.1 Additional EPA Documents to be Consulted
Title
Source
Reference No.
Superfund Exposure Assessment Manual (1988)
Ecological Assessments of Hazardous Waste Sites A Field
and Laboratory Reference Document (1989)
Ecological Information Resources Directory (1989)
User's Guide to the Contract Laboratory Program (1989)
Estimating Toxicity of Industrial Chemicals to Aquatic
Organisms Using Structure Activity Relationships (1988)
CERCLA Compliance with Other Laws Manual (1988)
Guidance for Conducting Remedial Investigations and
Feasibility Studies under CERCLA (Interim Final, 1988)
Office of Solid Waste and Emergency Response EPA/540/1-88/001
Office of Research and Development -
Corvallis Environmental Research Laboratory
Office of Information Resource Management
Office of Emergency and Remedial Response
Office of Toxic Substances
EPA/600/3-89/013
In Preparation
OSWER Dir. 9240.0-1
EPA/560/6-88/001
Office of Solid Waste and Emergency Response EPA/540/6-89/006
Office of Solid Waste and Emergency Response EPA/540/6-89/004
1.2 Ecological Assessment in the
Superfund Process
The Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA), as
amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA), calls upon EPA
to protect human health and the environment with
respect to releases or potential releases of con-
taminants from abandoned hazardous waste sites.
The proposed revision of the National Contingency
Plan (NCP) calls for identification and mitigation of
the environmental impacts of these sites and the
selection of remedial actions that are "protective of
environmental organisms and ecosystems." In addi-
tion, numerous Federal and State laws and
regulations concerning environmental protection are
potentially "applicable or relevant and appropriate
requirements" (ARARs). Compliance with these laws
and regulations may require evaluation of a site's
ecological effects and the measures needed to miti-
gate those effects. The specific legislative and other
mandates for ecological assessment are discussed in
Chapter 2 of this manual.
Ecological assessment may take place before, during
and after removal and remedial actions. Removal
actions, directed by the OSC, are generally taken in
response to an immediate hazard. When an
emergency response is under consideration, the
ecological assessment associated with removal
actions must be performed quickly. Existing
information, augmented by any field data that can be
collected in a short period of time, will be used to:
Decide if removal is necessary based on ecological
considerations,
Predict the ecological effects of removal actions,
and
Provide preliminary information to support a
Remedial Investigation if one is needed.
Ecological data should also be gathered before and
during remedial action, under the direction of the
RPM. These data will be used to:
- Determine the appropriate level of detail for the
ecological assessment,
- Decide if remedial action is necessary based on
ecological considerations,
- Evaluate the potential ecological effects of the
remedial action itself,
- Provide information necessary for mitigation of
the threat, and
- Design monitoring strategies for assessing the
progress and effectiveness of remediation.
A detailed assessment may be required to determine
whether or not the potential ecological effects of the
contaminants at a site warrant remedial action.
Although human health is frequently the major
concern, the ecological assessment may serve to ex-
pand the scope of the investigation, enlarging the
area under consideration, or redefining remediation
criteria, or both. Therefore, when appropriate, the
Scope of Work for the Remedial Inves-
tigation /Feasibility Study (RI/FS) should be written
to incorporate ecological investigations as early as
possible in the process.
The RPM also evaluates the alternatives outlined in
the RI/FS to determine whether the proposed
remedial action itself will have any deleterious
environmental effects. For example, if dredging is
included as part of a remedial alternative, the effects
of the dredging on aquatic organisms living on or in
the sediments will very likely need to be considered.
If a remediation plan proposes channeling a stream
into a new drainage area, the downstream effects on
wetlands may require investigation.
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Finally, ecological assessment may suggest
strategies for monitoring the progress and
effectiveness of remediation at or near a site. For
example, toxicity tests of soils, sediments, and water
have been used to supplement chemical residue data
in establishing cleanup criteria. On-site toxicity tests
may be more sensitive to low levels of contaminants
than other monitoring methods, and may indicate
toxicity of mixtures of contaminants more readily
than single-chemical criteria.
Environmental evaluation and human health
evaluation are parallel activities in the evaluation of
hazardous waste sites. As Figure 1.1 illustrates,
much of the data and analyses relating to the nature,
fate, and transport of a site's contaminants will be
used for both evaluations. At each point of these
common stages, however, analysts should be
sensitive to the possibility that certain contaminants
and exposure pathways may be more important for
the environmental evaluation than for the health
evaluation, or vice versa. It is also important to
recognize that each of the two evaluations can
sometimes make use of the other's information. For
example, the potential of a contaminant to
bioaccumulate may be estimated for a health
evaluation but be useful for the environmental
evaluation. Similarly, measurement of contaminant
levels in sport and commercial species for an environ-
mental evaluation may yield useful information for
the health evaluation.
1.3 Who Should Read this Manual?
This manual is designed for use by Remedial Project
Managers and On Scene Coordinators. The following
may also find the manual useful for understanding
the ecological assessment process as it relates to
Superfund sites:
EPA Regional Office managers of RPMs or
OSCs,
State hazardous waste officials who wish to
undertake ecological assessments of their
own,
EPA contractors and others who may perform
ecological assessments,
- Ecologists who have no past experience with
Superfund ecological assessments, and
Potentially responsible parties (if they are
performing the work at the site).
1.4 Organization of the Manual
This manual is intended to address the following
questions:
- How does ecological assessment help EPA
meet its statutory responsibilities?
- What is the underlying scientific basis for
ecological assessment?
- How should the RPM or OSC use technical
specialists in managing ecological
assessments?
- What kinds of data are necessary for
ecological assessments?
The chapters following this introduction are
- Chapter 2: Statutory and Regulatory Basis
of Ecological Assessment,
- Chapter 3: Basic Concepts for Ecological
Assessment,
- Chapter 4: The Role of Technical Specialists
in Ecological Assessment,
- Chapter 5: Planning an Ecological Assess-
ment, and
- Chapter 6: Organization and Presentation of
an Ecological Assessment
As Figure 1.2 illustrates, Chapters 2 through 4
provide introductions to different aspects of the
ecological assessment process. Chapters 5 and 6 then
provide more specific guidance on the information
needed in an ecological assessment.
Chapter 2 describes the authority provided by
CERCLA (as amended by SARA), requirements
contained in the National Contingency Plan, and
references to ecological assessment in the RI/FS and
Removal Guidances. The chapter also discusses
Federal standards, requirements, criteria, or
limitations that are potential ARARs.
Chapter 3 describes the basic scientific concepts
underlying ecological assessment. It is intended to
assist the RPM or OSC in working with the ecologists
who will provide technical advice or perform the
studies, by describing the conceptual framework
within which these specialists make their judgments.
This chapter defines numerous terms that are used
later in the manual. Readers who are familiar with
the concepts and terminology of ecology and
environmental chemistry may choose to skim this
chapter or skip it entirely.
Chapter 4 details the role of technical specialists in
ecological assessment. Their primary function is to
assist the RPM and the OSC in directing the
collection and evaluation of information on ecological
effects. They may serve as advisers or may actually
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Identify Contaminants of Concern
Health-Specific
General Concern
(Health and Environmental)
Environment-Specific
Quantify Release, Migration and Fate
Run
Fate and Transport
Models
Measure
Environmental
Concentrations
Identify Exposure Routes
Health-Specific
General Concern
(Health and Environmental)
Environment-Specific
Potentially Exposed
Habitats
Human Populations
at Risk
Health Effects
Studies
Potentially Exposed
Populations
Sport or Com-
mercial Species
Ecological Effects
Studies and Tests
Other Species
Human Health
Evaluation
Environmental
Evaluation
Figure 1.1 Relationship between health and environmental evaluations.
perform the ecological assessment under the direc-
tion of the RPM or the OSC.
Chapter 5 discusses the process of developing an
appropriate study design for assessment of a site,
including evaluation of contaminants of concern, site
characteristics, and ecological assessment endpoints.
In addition to specifying study objectives, this phase
must also address quality assurance and quality con-
trol (QA/QC) issues associated with the assessment.
Chapter 6 describes a basic outline for an as-
sessment. Although each site's assessment will differ
according to the details of the contaminants,
exposure routes, potentially affected habitats, and
species, this chapter provides a checklist of items for
the RPM or OSC to expect when overseeing the
preparation of an assessment. For any individual
site, expansion of the topics here maybe needed, with
appropriate explanations.
This manual is an introduction to a complex subject.
Assessment of an actual site requires a detailed
knowledge of the habitats and species that are
potentially exposed, the activity and movement of
contaminants in the environment, and the sampling
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and analytical methods needed to make scientifically
defensible judgments. Use of this manual will
provide a basis for the successful management of
such assessments.
Chapter 2:
Statutory and
Regulatory Basis
1
Chapters:
Basic Principles
Chapter 4:
Role of Technical
Specialists
1
Chapters:
Planning an
Ecological
Assessment
Chapter 6:
Organization
and Presentation
Figure 1.2 Logical Organization of this manual.
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Chapter 2
Statutory and Regulatory Basis of Ecological Assessment
Ecological assessment of hazardous waste sites is an
essential element in determining overall risk and
protecting public health, welfare, and the
environment. The Agency considers ecological factors
in assessing hazards and in reviewing alternative
remedial actions because:
- Through the authority found in CERCLA (as
amended by SARA) and other statutes, the
Agency seeks to protect wildlife, fisheries,
endangered and threatened species, and valued
habitats.
- From a scientific viewpoint, the Agency needs to
examine ecological effects and routes of exposure
so that (a) important impacts and transport
pathways are not overlooked, and (b) reasonable
estimates are made of health and environmental
effects.
This chapter describes the statutory and regulatory
framework underlying ecological assessment.
Certain provisions of CERCLA and SARA are
especially important in this regard:
- The statutes require that remedial actions
selected for a site be sufficient to protect human
health and the environment.
- Compliance with applicable or relevant and
appropriate requirements (ARARs) entails
consideration of numerous Federal and State
laws and regulations concerning natural resource
preservation and protection when evaluating
possible response actions.
- SARA calls upon EPA to notify Federal natural
resource trustees of negotiations with potentially
responsible parties and to encourage trustees'
participation in the negotiations if a release or
threatened release may result in damages to
protected natural resources.
The chapter begins with a discussion of the authority
provided in the amended CERCLA for conducting
ecological assessments. Section 2.2 describes the
implementation of CERCLA as outlined in the
proposed revisions to the National Contingency Plan.
Guidance documents for removal actions and the
RI/FS process are discussed in Sections 2.3 and 2.4,
respectively. A wide array of potential ARARs is the
subject of Section 2.5. It is important to note,
however, that this section is not intended to be an
exhaustive survey of potential ARARs; the RPM or
OSC will need to ascertain the specific Federal and
State requirements that apply to each site, depending
on the contaminants of concern and the
characteristics of the site.
2.1 CERCLA/SARA Authorities
The Comprehensive Environmental Response,
Compensation and Liability Act, as amended by the
Superfund Amendments and Reauthorization Act of
1986, requires EPA to ensure the protection of the
environment in (1) selection of remedial alternatives
and (2) assessment of the degree of cleanup
necessary. Several sections of CERCLA make
reference to protection of health and the environment
as parts of a whole. Section 105(a)(2) calls for
methods to evaluate and remedy "any releases or
threats of releases. . . which pose substantial danger
to the public health or the environment." Section
121(b)(l) requires selection of remedial actions that
are "protective of human health and the
environment. " Section 121(c) calls for "assurance
that human health and the environment continue to
be protected." And Section 121(d) directs EPA to
attain a degree of cleanup "which assures protection
of human health and the environment."
CERCLA Section 104(b)(2) calls upon EPA to notify
the appropriate Federal and State natural resource
trustees promptly about potential dangers to
protected resources. The Federal natural resource
trustees include:
- The U.S. Fish and Wildlife Service (USFWS), the
National Park Service (NPS), and the Bureau of
Land Management (BLM) of the Department of
the Interior;
- The National Oceanic and Atmospheric
Administration (NOAA) of the U.S. Department
of Commerce; and
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- The U.S. Department of Agriculture
Service.
Forest
State agencies and Indian tribes are also designated
trustees for natural resources under their
jurisdiction. Section 122(j) of the amended CERCLA
requires the Agency to notify the Federal natural
resource trustees of any negotiations regarding the
release of hazardous substances that may have
resulted in natural resource damage. Section
122 (j)(l) also calls upon EPA to encourage Federal
natural resource trustees to participate in
negotiations with potentially responsible parties
(PRPs). If EPA seeks to settle with a PRP by signing
a covenant not to sue, the Federal natural resource
trustee must agree to this covenant in writing.
Section 122(j) (2) states that:
The Federal natural resource trustee may agree
to such a covenant if the potentially responsible
party agrees to undertake appropriate actions
necessary to protect and restore the natural
resources damaged by such release or threatened
release of hazardous substances.
The ecological assessment directed by the OSC or
RPM should not be confused with the Preliminary
Natural Resource Survey (PNRS) or the Natural
Resource Damage Assessment (NRDA), which
are performed by natural resource trustees. PNRSs
are simple screening studies, based on readily
available information, that may be conducted by
trustees to determine whether or not (a) trustee
resources may have been affected, and (b) further
attention to trustee resources is warranted at a
particular site. The NRDA may be conducted by one
or more trustees if a response action will not
sufficiently restore or protect natural resources
damaged by a release. The purpose of the NRDA is to
determine the appropriate level of compensation from
a responsible party. Data collected in an ecological
assessment may prove helpful to the trustees in
carrying out their responsibilities. It is important to
encourage the natural resource trustee to participate
in the Superfund process at the earliest possible
stage. In this way, the trustee can be assured that
any potential environmental concerns are addressed,
and conclusion of actions may be expedited.
2.2 The National Contingency Plan
As required by SARA Section 105, EPA has revised
the National Contingency Plan (NCP)1, which
provides for effective response to discharges of oil and
1 USEPA, National Oil and Hazardous Substances Pollution
Contingency Plan 40 CFR Part 300. EPA Proposed Revisions to
the NCP at 53 Fed. Reg. 51395 (Proposed Rule, December 21,
1988). All references to the "proposed NCP" in this manual are to
this proposed rule. Quotations from the NCP used in this section
are from the Preamble.
releases of hazardous substances. Section 300.120 of
the proposed NCP charges the site-specific OSC or
RPM with (1) identifying potential impacts on public
health, welfare, and the environment, and (2) setting
priorities for this protection.
Like CERCLA, the proposed NCP refers throughout
to health and environment as aspects of the
evaluation and remediation processes. For example,
in discussing the baseline risk assessment in a
Remedial Investigation, the purpose is defined as
determining "whether the site poses a current or
potential risk to human health and the environment
in the absence of any remedial action." The exposure
assessment in the RI "is conducted to identify the
magnitude of actual or potential human or
environmental exposures ..." The toxicity
assessment "considers. . . the types of adverse health
or environmental effects associated with chemical
exposures." In addition, the proposed NCP states that
"Superfund remedies will ... be protective of
environmental organisms and ecosystems."
Sections 300.175 and 300.180 of the proposed NCP
direct the RPM or OSC to coordinate with other
Federal and State agencies. USFWS and NOAA are
specifically cited with respect to endangered or
threatened species. Under Section 300.430, the RPM
or OSC is to notify affected land management
agencies and natural resource trustees regarding any
release or discharge that affects natural resources
under their jurisdiction. According to the proposed
NCP, "when trustees are notified of or discover
possible damage to natural resources, they may
conduct a preliminary survey of the area to
determine if natural resources under their trust are
affected." The document adds an important proviso:
Although a trustee may be responsible for certain
natural resources affected or potentially affected
by a release, it is important that only one person
(i.e., the lead agency OSC or RPM) manage
activities at the site of a release or potential
release. The OSC or RPM shall coordinate
responsibilities for CERCLA section 104
assessments, investigations, and planning,
including Federal trustees' participation in
negotiations with PRPs as provided in CERCLA
section 122(j)(l). Close communication and
coordination between OSCs/RPMs and trustees is
essential.
If, after the remedial action is completed, any
hazardous substances remain on a site "above levels
that allow for unlimited use and unrestricted
exposure for human and environmental receptors,"
the proposed NCP would require the lead Agency to
review the remedial action every five years to ensure
that the environment continues to be protected.
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2.3 Removal Action Guidance
The Guidance covering removal actions calls upon
the OSC to consider threats to the environment in
addition to public health when preparing the Action
Memorandum required for all removals.2For
example, in discussing the role of the National
Response Team (NRT), the Guidance states that the
NRT "should be activated as an emergency response
team if [al release . . . [i]nvolves significant
population threat or national policy issues ... or
substantial threats to natural resources. "3In the
section on determining the need for and urgency of a
removal, the manual specifies:
At any release, regardless of whether the site is
on the NPL, where the OSC determines that
there is a threat to public health, welfare or the
environment, . . . the OSC may take any
appropriate action to abate, minimize, stabilize,
mitigate or eliminate the actual or potential
release and the resulting threat.4
For those incidents not categorized as "classic
emergencies," the Guidance indicates that "the OSC
should conduct more extensive data collection and
analysis to document more completely the actual or
potential health and environmental threat." As an
example, the manual calls on the OSC to "make a
concerted effort to use existing environmental and
health standards as triggers for initiating response
and as guidelines in determining response actions."5
In describing the contents of the preliminary
assessment, the Guidance points out that "the OSC
must incorporate any special procedures or technical
criteria EPA has established for a variety of special,
complex cases," which include floodplains and
wetlands.'Among the determinations that need to be
made at the conclusion of the preliminary
assessment, the Guidance includes the following
If the OSC determines that natural resources
have been or are likely to be damaged, the OSC
should ensure that the trustees of the affected
natural resources are notified in order that they
may initiate appropriate actions7. . . .
The Guidance devotes a section to removal actions in
floodplains and wetlands, pointing out that such
actions "should be consistent to the extent practicable
with Federal policy and procedures for the protection
'Superfund Removal Process (OSWER Directive 9360.O-03B).
EPA Office of Emergency and Remedial Response, February 1988.
albid., p. 111-10.
'Ibid., p. 111-14.
5lbid., p. 111-15.
6 Ibid., p. 111-11.
'Ibid., p. 111-12.
of floodplains and wetlands." Descriptions and
references for the specific regulations are given in
Section 2.5, below. Under the policy established by
the Office of Emergency and Remedial Response,
specific actions are required of the OSC:
- "[As] part of the preliminary assessment, . . .
determine whether the release is in, near or
affecting a floodplain or wetland."
- If "the release is in proximity to or has the
potential to affect a floodplain or wetland,"
evaluate
- "Possible impact of proposed response
actions on the floodplain/wetland,"
- "Alternate response actions. ..," and
- "Measures to minimize potential adverse
impacts."
- "[DJocument the results of this evaluation in the
Action Memorandum."
- "[EJnsure that the implementation of approved
response actions minimizes adverse impacts on
the floodplain/wetland."8
The Guidance also makes specific reference to envi-
ronmental threats in the Appendices describing the
Action Memorandum. For example, demonstration of
actual or potential "catastrophic environmental
damage" may be cited as the reason for activating an
OSC's $50,000 authority in a time-critical removal.
In describing the characteristics of an incident, the
OSC is asked to demonstrate "that the incident
already has posed or imminently will pose an
imminent and significant danger to the public or to
the environment." One way of demonstrating this is
to show "proximity to ... significant natural
resources." The Guidance goes on to ask several key
questions whose answers will help determine if the
incident is time-critical:
Are there confirmed reports of injuries to natural
resources or injuries to or deaths of flora and
fauna? Are more anticipated? How sensitive
critical are these resources (e.g., protected
wildlife refuge)? Is there catastrophic environ-
mental damage?
Even if the incident does not appear to be time-
critical, the Guidance cautions the OSC that "[s]ome
environmental threats are not urgent, but
nevertheless are significant. " To aid in
demonstrating that failure to respond "will create an
'Ibid., pp. IV-12 and IV-13
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unacceptable impact on natural resources and the
environment," the Guidance poses these questions:
- "What additional information (beyond that
requested in the time-critical screen) documents
the threat to the environment (e.g., monitoring or
other data verifying injury to or destruction of
natural resources, critical habitats)?"
- "What are the known short- and long-term effects
that are likely if there is no response or response
is delayed? When is that threat likely to manifest
itself?"9
For removals that will take less than 12 months and
cost less than $2 million, Appendix 6 of the Guidance
provides a model Action Memorandum to assist the
OSC in meeting the requirements of CERCLA and
the proposed NCP. Under the heading "Site
Description," the model reminds the OSC to describe
"areas adjacent to the incident or site in terms of
vulnerable or sensitive populations, habitats and
natural resources. " The section goes on to cite
sensitive areas such as wetlands, floodplains,
"sensitive ecosystems," or wild and scenic rivers.
Under the heading "Threats to the Environment,"
the model calls upon the OSC to:
List all the current and potential threats. . . that
adversely affect the environment (e.g., damage to
ecosystem, animals, ground water). Identify any
natural resource or environmental damage that
already has occurred and the extent of exposure
(e.g., acute or chronic). Indicate whether there
have been reports of deaths of flora or fauna (e.g.,
fish kills). . . . Discuss potential damage to the
environment and indicate a time frame within
which damage will occur if response actions are
not taken.
Discuss all actual or potential impacts on the
affected area. Describe any anticipated exposure
and whether it is imminent. Indicate whether the
release threatens endangered species, critical
wetlands, or other resources protected under law.
State whether natural resources trustees have
been notified. 10
2.4 Remedial Investigation and
Feasibility Study (RI/FS) Guidance
Remedial Project Managers are responsible for all
phases of the remedial process, including but not
limited to the RI/FS. Ecological assessment of
appropriate detail may be conducted at any of these
phases. The nature, extent, and level of detail of the
ecological assessment will be determined according
to the phase of the remedial process, the specific
study objectives, and the characteristics of the site
and its contaminants. These decisions should be
made in close consultation with technical advisers, as
discussed in Chapter 4.
This Section focuses on ecological components of the
RI/FS process as outlined in EPA's RI/FS Guidance. 11
In the scoping phase, the RPM develops a project plan
to define the problem and identify solutions. Among
the activities at this stage are
collecting and analyzing existing data to develop
a conceptual model that can be used to assess
both the nature and the extent of contamination
and to identify potential exposure pathways and
potential human health and/or environmental
receptors.12
As part of the collection and analysis of existing data,
the Guidance specifically mentions "evidence of ...
biotic contamination," identification of "biotic
migration pathways," information on ecology of the
area, and data on "environmental receptors." The
Guidance further states:
Existing information describing the common
flora and fauna of the site and surrounding areas
should be collected. The location of any
threatened, endangered, or rare species, sensitive
environmental areas, or critical habitats on or
near the site should be identified.13
A limited field investigation may be undertaken in
this phase of the RI/FS process. The Guidance
includes a preliminary "ecological reconnaissance" in
the list of possible components of this field
investigation.
The project planning stage is also the time for the
RPM to begin preliminary identification of ARARs
and To Be Considered (TBC) information. The
Guidance points out that some requirements "may
set restrictions on activities within specific locations
such as floodplains or wetlands."14
Characterized as the most important part of the
scoping process, the identification of data needs
includes determining the information required to
"define source areas of contamination, the potential
pathways of migration, and the potential receptors
and associated exposure pathways." The objective is
9 Ibid., Appendix 5, pp. 3-5.
10lbid, Appendix 6, pp. 6-7.
11 Guidance for Conducting Remedial Investigations and
Feasibility Studies under CERCLA (Interim Final}. OSWER
Directive 9355.3-01. EPA Office of Emergency and Remedial
Response. October 1988.
12 Ibid., p. 2-2.
13 Ibid., p. 2-7.
14 Ibid., p. 2-13.
10
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to determine "whether, or to what extent, a threat to
human health or the environment exists."15
The culmination of the project planning stage is the
preparation of the Work Plan and the Sampling and
Analysis Plan (SAP). The Work Plan includes a
preliminary evaluation of (a) potential pathways of
contaminant migration and (b) public health and
environmental impacts. The SAP is a key step in the
assessment process, because it defines what data are
to be sought, why the data are needed, where and how
the data will be collected, and how the data will be
analyzed and interpreted. Equally important, the
SAP specifies the data quality objectives and quality
assurance plan for the study, indicating the levels of
precision and accuracy that are expected in data
collection and analysis, and describing how the
expected precision and accuracy will be maintained.
It is at this stage that data collection for ecological
assessment should be planned, including field
surveys, toxicity testing, bioaccumulation studies,
and sampling to determine the extent of
contamination. "As with other aspects of the SAP,
the planning process for ecological assessment may
be iterative: that is, analysis of early data may
indicate that the sampling and analysis need
revision. This may entail expanding the area to be
sampled or planning new toxicity tests. It may also
point to a reduction in effort if anticipated results fail
to materialize.
In describing the baseline risk assessment for the RI,
the RI/FS Guidance makes frequent reference to the
ecological side of the assessment. The baseline risk
assessment is intended to "provide an evaluation of
the potential threat to human health and the
environment in the absence of any remedial action. "
The process includes among its tasks the
identification and characterization of (a) levels of
contamination in relevant media, including biota,
and (b) "potential human and environmental
receptors." The toxicity assessment component
"considers . . . the types of adverse health or
environmental effects associated with individual and
multiple chemical exposure s." The risk
characterization component entails estimating
"carcinogenic risks, noncarcinogenic risks, and
environmental risks.""The Guidance specifies
further:
Characterization of the environmental risks
involves identifying the potential exposures to
the surrounding ecological receptors and
evaluating the potential effects associated with
such exposure(s). Important factors to consider
include disruptive effects to populations (both
plant and animal) and the extent of
perturbations to the ecological community.18
The Feasibility Study involves screening of
remediation alternatives for their effectiveness,
including their "potential impacts to human health
and the environment during the construction and
implementation phase.""Alternatives are expected
to be evaluated during the screening process "to
ensure that they protect human health and the
environment from each potential pathway of
concern."20
2.5 CERCLA Compliance with other
Environmental Statutes (ARARs)
Section 121(d)(2)(A) of CERCLA requires that the
Superfund remedial action meet Federal and State
standards, requirements, criteria, or limitations that
are "applicable or relevant and appropriate
requirements" (ARARs). The OSC or RPM is
responsible for identifying potential ARARs for each
site.
The RPM or OSC should use the EPA ARARs
Manual21 to assist in identifying potential ARARs on
a case-by-case basis. Some of the Federal
environmental statutes and regulations that may be
ARARs for a particular site include:
- The Resource Conservation and Recovery Act of
1976, as Amended. RCRA requirements for
ground-water protection, surface impoundments,
waste piles, underground storage tanks, and
surface treatment are all considered to be
potentially applicable for both human health and
protection of the environment at sites that
contain RCRA-listed or characteristic wastes and
where waste management activities took place
after the effective date of the relevant RCRA
Subtitle. The RPM or OSC should consult with
the appropriate Regional RCRA staff to make
this determination.
- The Federal Water Pollution Control Act, as
Amended. This law, also known as the Clean
Water Act, includes numerous sections that may
pertain to remediation of Superfund sites. The
OSC or RPM should consult the ARARs Manual
for a detailed discussion of relevant sections.
15 Ibid., p. 2-14.
16 See EPA/ORD, Ecological Assessments of Hazardous Waste
Sites: A Field and Laboratory Reference Document
(EPA/600/3-89/013) for specific information on field and
laboratory methods.
"Ibid., pp. 3-35 through 3-43.
3 Ibid., p. 3-43.
9 Ibid., p. 4-24.
° Ibid., p. 4-30.
CERCLA Compliance With Other Laws Manual, (OSWER
Directive 9234.1-01) EPA Office of Emergency and Remedial
Response. Draft, August 8, 1988.
11
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Section 404, which requires protection of
wetlands, is of special importance for
environmental evaluation of Superfund sites.
The Clean Air Act of 1970, as Amended. Under
the CAA, EPA has established National Ambient
Air Quality Standards for key pollutants. In the
development of these standards, the Agency
prepares Air Quality Criteria documents that
investigate various effects of exposure to the
subject pollutants, including those that occur on
vegetation. These criteria documents and the
standards developed from them may help
establish remediation criteria where airborne
exposure is possible. In addition, EPA has
established limitations for numerous chemicals
in its National Emission Standards for
Hazardous Air Pollutants and the New Source
Performance Standards. The OSC or RPM may
wish to determine the utility of these standards
for the protection of natural resources from
airborne exposure to contaminants.
The Toxic Substances Control Act of 1976. Section
2601 (b) of the Toxic Substances Control Act
states the policy of the United States that ". . .
adequate data should be developed with respect
to the effect of chemical substances and mixtures
on health and the environment . . . ." Data
collected under TSCA concerning ecological
effects may prove useful in determining
protective levels of contaminants. The OSC or
RPM should refer to the ARARs Manual for other
information on applicability of TSCA.
The Federal Insecticide, Fungicide and
Rodenticide Act of 1947, as Amended. FIFRA
requires that all pesticides be registered with
EPA. To obtain registration, manufacturers must
supply EPA with certain data concerning
environmental fate and transport, health effects,
and ecological effects. EPA's Office of Pesticide
Programs (OPP) has issued Registration
Standards, which summarize the Agency's
assessment of many pesticide active ingredients,
some of which are found at Superfund sites. The
analyses contained in these documents may
assist in the evaluation of hazards and in
determining protective levels of contaminants.
OPP's regulatory positions on the continued
registration of individual pesticides may also
provide guidance on controlling environmental
hazards.
Endangered Species Act of 1973, as Reauthorized
in 1988. Section 7 of the Act requires Federal
agencies to ensure that their actions will not
jeopardize the continued existence of any
endangered or threatened species. The U.S. Fish
and Wildlife Service and the National Marine
Fisheries Service have primary responsibility for
this Act.
Fish and Wildlife Conservation Act of 1980.
Section 2903 requires States to identify
significant habitats and develop conservation
plans for these areas. Although it is unlikely that
a Superfund site would be located in one of these
significant habitats, the RPM should cofirm this
with the responsible State agency.
Marine Protection, Research and Sanctuaries Act
of 1972. Section 1401 declares the U.S. policy of
regulating dumping to ". . . prevent or strictly
limit the dumping into ocean waters of any
material which would adversely affect human
health, welfare, or amenities or the marine
environment, ecological systems, or economic
potentialities." This legislation may be relevant
for cleanup and removal actions at or near the
ocean.
Coastal Zone Management Act of 1972. This
legislation is designed to (a) encourage States to
develop management plans to protect and
preserve the coastal zone, and (b) ensure that
Federal actions are consistent with these
management plans. The RPM or OSC would need
to obtain these management plans if remedial or
removal actions will take place in the coastal
zone.
Wild and Scenic Rivers Act of 1972. Section 2171
declares that certain rivers ". . . possess
outstanding remarkable scenic, recreational,
geologic, fish and wildlife, historic, cultural, or
other similar value" and should be preserved, [f
remedial or removal action is taking place at or
near a river, the RPM or OSC should determine
whether it has been designated as "wild and
scenic," and whether there are any action-specific
ARARs regarding the site or its contaminants.
The National Park Service has primary
responsibility for this Act.
Fish and Wildlife Coordination Act, as Amended
in 1965. Section 662(a) states that the Fish and
Wildlife Service must be consulted when bodies of
water are diverted or modified by another
Federal Agency. The facility is to be constructed
"with a view to the conservation of wildlife
resources by prevention of loss, or damage to such
resources as well as providing for the
development and improvement thereof. ..." The
RPM should consult with USFWS or NOAA if
remedial action entails altering streams or
wetlands.
The Migratory Bird Treaty Act of 1972
implements many treaties involving migratory
birds. This statute protects almost all species of
12
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native birds in the U.S. from unregulated "take,"
which can include poisoning at hazardous waste
sites. The Act is a primary tool of the U.S. Fish
and Wildlife Service and other Federal agencies
in managing migratory birds.
The Marine Mammal Protection Act of 1972. This
law protects all marine mammals, some but not
all of which are endangered species. The National
Oceanic and Atmospheric Administration has
primary responsibility for this Act. The Fish and
Wildlife Service also has responsibility for some
species.
Under the authority of the Clean Water Act, EPA
develops Federal Water Quality Criteria (FWQCs),
including criteria for protection of aquatic life. In
1987, EPA's Office of Water Regulations and
Standards revised and published its Quality Criteria
for Water, 1986. For each of more than 120 inorganic
and organic compounds, this publication contains
numerical Ambient Water Quality Criteria for the
protection of fresh and salt water plants and animals
and their habitats, covering both acute and chronic
exposure. The proposed NCP describes the FWQCs
as:
• • • nonenforceable guidelines used by the States
to set Water Quality Standards (WQS) for surface
water. . . . States designate the use of a given
water body based on its current and potential use
and apply the FWQC to set pollutant levels that
are protective of that use. ... If a State has
promulgated a numerical WQS that applies to
the contaminant and the designated use of the
surface water at a site, the WQS will generally be
applicable or relevant and appropriate for
determining cleanup levels, rather than a
FWQC.
The proposed NCP discusses the difference between
use of a FWQC when the water will be used for
drinking and when the principal human exposure is
expected through consumption of fish. Separate
FWQC exist for protection of aquatic life. According
to the proposed NCP:
A FWQC for protection of aquatic life may be
relevant and appropriate for a remedy involving
surface waters (or ground-water discharges to
surface water) when the designated use requires
protection of aquatic life or when environmental
concerns exist at the site. If protection of human
health and aquatic life are both a concern, the
more stringent standard should generally be
applied.
The proposed NCP sets several criteria for
determining the relevance and appropriateness of a
FWQC. The FWQC should be "intended to protect the
uses designated for the water body at the site, or ...
the exposures for which the FWQC are protective are
likely to occur." The FWQC "must also reflect current
scientific information." Finally, the relevance and
appropriateness "depends on the availability of
standards, such as an MCL [Maximum Contaminant
Level] or WQS, specific for the constituent and use."
It is important to stress that the above list of statutes
is not intended to be exhaustive. In particular, the
preceding discussion focused only on potentially
applicable Federal laws and regulations. State, local,
and other Federal requirements may also be
applicable or relevant and appropriate. For a specific
site, specific requirements will apply, depending on
the contaminants of concern, the location of the site,
and the potentially exposed receptors. Some, all, or
none of the potential ARARs discussed in this Section
may apply. The RPM or OSC should confer with
appropriate State regulatory authorities, officials in
other EPA programs, and representatives of other
Federal agencies in the event of uncertainty on
possible ARARs.
13
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Chapter 3
Basic Concepts for Ecological Assessment
This chapter has three purposes. First, the chapter
introduces and defines ideas and terms commonly
used in ecology. Our intent is to make the RPM or
OSC aware of the general meaning of these concepts,
so as to facilitate discussion with the technical
specialists providing consultation on ecological
assessment. Second, the chapter discusses the nature
of contaminants' ecological effects. Although a
contaminant may cause illness or death to individual
organisms, its effects on the structure and function of
ecological assemblages may be measured in terms
quite different from those used to describe individual
effects. Third, the chapter describes some of the
biological, chemical, and environmental factors that
influence the ecological effects of contaminants.
Readers who are familiar with these topics may wish
to skim this chapter. Those who are well versed in
ecology and environmental chemistry may want to
skip it entirely.
3.1 Objects of Study in Ecology
Ecologists generally study three levels of
organization: populations, communities, and
ecosystems. (See Figure 3.1.) Each level has its
characteristic measures of extent, structure, and
change.
A population is a group of organisms of the same
species, generally occupying a contiguous area, and
capable of interbreeding. The size and extent of
populations are most often described in terms of
density, the number of organisms per unit area. Such
terms as standing crop or standing stock may be used
to indicate population size at a particular time
interval, with the unit area specified or implied. The
structure of populations is often expressed in terms of
the numbers of organisms in different age classes,
such as eggs, juveniles, and adults. Population
growth and decline are determined by characteristic
rates of birth, death, immigration, and emigration,
all of which are subject to change with environmental
conditions, including interaction with populations of
other organisms.
No species in nature exists in isolation from all
others. Populations of different species live together
Ecosphere
Ecosystems
Communities
Populations
Organisms
Figure 3.1. Levels of organization of matter.
Source: Living in the Environment, 3/E, by G.
Tyler Miller, Jr. Copyright (C) 1982 by
Wadsworth, Inc. Reprinted by permission
of the publisher.
in complex associations called communities. The
interactions among populations and the chemical and
physical constraints of the environment together
determine a community's structure and geographical
extent. The structure of a community is defined by
what species are present, in what numbers, and in
what proportion to each other. It is also described by
the food web, or trophic structure: that is, which
species eat which other species, or who produces and
consumes how much.
15
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Most communities change seasonally or over longer
cycles as some species increase or decrease in
abundance in response to environmental changes
such as temperature or rainfall cycles. Communities
also can evolve over longer periods of time in a
process known as succession. In successional
change, some species are displaced by others and new
environmental conditions are created that support
more species. For example, when a meadow "grows"
into a forest, annual plants are gradually replaced by
perennials, shrubs, and trees. Each plant type
modifies the environment in ways that tend to favor
the succeeding type. Eventually, tree canopies shade
much of the area that was once exposed to sunlight,
and a leaf-litter layer covers soil that was once bare.
Species diversity - expressed as the number of
species or the relative abundance of the various
species in a given area - is often used to characterize
and compare the structure and evolutionary
"maturity" of communities. Communities are in
constant" flux as organisms are born, eat and get
eaten, immigrate and emigrate, die and decompose.
These fluxes are described as energy and nutrient
flows through food webs, and are determined by rates
of primary production (photosynthesis) by plants and
rates of consumption by herbivores, carnivores, and
decomposers.
Just as populations exist only in association with
others in communities, so too do communities
interact continuously with the nonliving components
of the environment in an ecosystem: "A functional
system of complementary relationships, and transfer
and circulation of energy and matter. "'The
ecosystem comprises all the living organisms, their
remains, and the minerals, chemicals, water, and
atmosphere on which they depend for sustenance and
shelter. Living and nonliving components are closely
linked, each affecting the other. For example:
- Soil composition and structure are often
highly influenced by the organisms that
inhabit it, and by the decomposition products
of organisms after they die.
- Orological formations such as coral reefs and
chalk cliffs are the result of calcium
deposition by plants and animals over eons;
they in turn affect the flow of wind and water,
and provide habitat for countless other
organisms.
Ecosystems are characterized by many of the same
measures as communities: species composition and
diversity, nutrient and energy flows, and rates of
production, consumption, and decomposition. Unlike
community measures, however, ecosystem structure
and function includes nonliving stores of materials
1 Eugene P. Odum, Fundamentals of Ecology, Third Edition
(Philadelphia W.B. Saunders Company, 1971).
and energy along with the animals, plants, and
microbes that make up the biotic portion of the
environment. Because it encompasses all of the
relevant physical and biological relationships
governing organisms, populations, and communities,
the ecosystem is generally considered the
fundamental unit of ecology.
Energy and matter flow through ecosystems by
means of complex systems known as food chains
and food webs. (See Figures 3.2a and 3.2b.) A food
chain describes the transfer of material and energy
from one organism to another organism as one eats or
decomposes the other. Food chains are
hierarchically arranged into trophic levels:
- Primary producers -green plants
(including algae and microscopic aquatic
plants called phytoplankton) - capture solar.
energy through photosynthesis which
converts carbon dioxide and water into
carbohydrates, a form of energy storage
suitable for use by other organisms;
- Primary consumers (herbivores) eat
plants;
Secondary consumers (carnivores) eat
herbivores;
- Tertiary consumers (top carnivores) feed
on other carnivores; and
- Decomposers - including certain fungi, and
bacteria - feed on dead and decaying
organisms, liberating simple organic
chemicals and mineral nutrients for recycling
in the ecosystem.
Food webs are interconnecting food chains. These
more realistically describe the complex system of
pathways by which the flow of matter and energy
takes place in nature. Such pathways do not always
follow a strict progression of producer to herbivore to
carnivore. Some plants die and are decomposed
without first being eaten by herbivores. Many species
have mixed diets of plant and animal material;
others change their feeding habits seasonally or have
different food requirements at different life stages.
For example, many bird species that feed primarily
on seeds during most of the year switch to insects and
other invertebrates when raising young, because the
higher protein content of the animal prey increases
the likelihood that the young birds will survive.
3.2 Types of Ecosystems
The types of ecosystems vary with climatic,
topographical, geological, chemical, and biotic
factors. On land, they range from Arctic tundras to
tropical rain forests, sand dunes to mountain tops,
16
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Type of Food Chain
Primary Secondary Tertiary Quaternary
Producer Consumer Consumer Consumer Consumer
Terrestrial
Grazing
Grain
Terrestrial
Decomposer
Leaves
Bacteria
Terrestrial
Grazing
Decomposer
Leaves
Fungi
Squirrel
Hawk
Aquatic
Grazing
Phytoplankton Zooplankton
Perch
Bass
Humans
Terrestrial-aquatic
Grazing
Grain
Grasshopper
Frog
Trout
Humans
Figure 3.2a. Example of Typical Food Chains
Source: Living in the Environmental, 3/E, by G. Tyler Miller, Jr. Copyright (C) 1982 by Wadsworth, Inc. Reprinted by
permission of the publisher.
deserts to forests, pure stands of evergreens to mixed
stands of hardwoods. Freshwater ecosystems include
ponds, lakes, streams and rivers. In the transition
zones between land and water, wetlands include
fresh-water and salt marshes, wet meadows, bogs,
and swamps. Marine ecosystems range from
estuaries and intertidal zones to the open sea and
deep ocean trenches. Each ecosystem type has unique
combinations of physical, chemical, and biological
characteristics, and thus may respond to
contamination in its own unique way. Not only does
the environment influence the activities of
organisms, but organisms also influence the
environment.
The physical and chemical structure of an ecosystem
may determine how contaminants affect its resident
species, and the biological interactions may
determine where and how the contaminants move in
the environment and which species are exposed to
particular concentrations. For example,
contaminants in a forested area may be subject to less
degradation due to sunlight than the same chemicals
in grassland soils. Chemicals adhering to soil
particles are less likely to be washed into streams if
the soil is well covered with vegetation or
decomposing leaf litter than if the area is sparsely
vegetated or bare.
Terrestrial ecosystems are generally categorized
according to the vegetation types that dominate the
plant community. These are the species upon which
the rest of the community's structure is based - the
herbivores which feed on the vegetation, the
17
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Mountain Lions
Tertiary
Consumers
(Top Carnivores)
Secondary
Consumers
(Carnivores)
Primary
Consumers
(Herbivores)
Decomposers
(Microconsumers)
Figure 3.2b. A greatly simplified terrestrial food web.
Source: Living in the Environment, 3/E, by G. Tyler Miller, Jr. Copyright (C) 1982 by Wadsworth, Inc. Reprinted by
permission of the publisher.
carnivores which feed on the herbivores and on each
other, and the decomposers which feed on the dead
plant and animal material and return mineral
nutrients to the soil for recycling through the food
web. The vegetation found at a particular site is
determined by a wide variety of factors, including
climate, soil type, altitude and slope of the land, and
current and former uses of the land by people. Two
very common ecosystem types in the temperate zone
are deciduous forests and grasslands.
Temperate deciduous (leaf-shedding) forests are
found in eastern North America. They have plentiful,
evenly dispersed rainfall, moderate temperatures,
and contrasting seasons. The annual leaf fall
provides habitat for large numbers of insects and
fungi that feed on the leaf litter, eventually breaking
it down into organic materials and minerals that
build up the soil.
Temperate grasslands cover the interior of North
America and Eurasia, southern South America, and
Australia. They receive moderate amounts of
rainfall. Tall grasses tend to grow in soil having a
high moisture content, while shorter grasses occur in
more arid areas. Numerous grass species have
developed adaptations to take advantage of seasonal
variations in climate. One group grows in the cooler
temperatures of the spring and fall, while another
group thrives in the warmer temperatures of
summer. These seasonal shifts in species' growth
results in a high annual productivity in grasslands,
as the growing season for the community as a whole
is effectively extended to three seasons. This
productivity has allowed grasslands to support large
herds of grazing animals, such as bison, but the
comparatively simple vegetation structure tends to
support fewer animal species than a forest of similar
size. The high volume of plant material available for
decomposition in grasslands creates very different
soil compositions from those created by forest leaf
litter. Occasional fires contribute to the stability of
grasslands, as they hinder the growth of competitive
woody plants.
Wetlands are areas in which topography and
hydrology create a zone of transition between
terrestrial and aquatic environments. The combined
18
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characteristics of each create conditions of great
productivity and biological diversity. Because of
these unique conditions, both fresh-water and marine
wetlands perform several important ecological
functions and provide benefits that can be adversely
affected by contamination. These include:
- Hydrologic benefits such as flood attenuation
and ground-water recharge;
- Water-quality benefits such as (a) removal
and cycling of sediments, organic materials,
and nutrients, and (b) stabilization of banks
and shorelines and control of erosion; and
- Wildlife benefits such as providing habitat
and food sources for fish, shellfish, waterfowl
and other birds, mammals and other
wildlife.2
Contamination may adversely affect wetland
functions in many ways, depending on the wetland
type, geographic location, location within a
watershed, and other factors. For example, a
contaminated wetland may occur close to a National
or State park or wildlife management area, or may be
of a type and in an area that contains endangered
species. (According to the U.S. Fish and Wildlife
Service, most endangered species in the United
States are dependent on wetlands.) Ecological
impacts to wetlands may be either direct, where a
contaminant has been deposited into a wetland, or
indirect, where a wetland is in close proximity to a
contaminant source.
The type of wetland may by itself be important in
determining the ecological effects of contamination.
For example, heavy-metal contaminants are more
likely to impair ecological functions when released
into an acidic bog than a similar release into the
relatively well buffered waters of a salt marsh.
Hence, the classification of wetlands can be used as a
starting point for the evaluation of ecological
imp acts.'General wetland types include freshwater
deciduous wetlands (dominated by red maple in the
Northeastern U.S.), wet meadows (transitional stage
to terrestrial systems), bogs (acidic peat rich soils
prevalent in the Northeastern U.S.), bottomland
hardwood wetlands (dominant in the Southeastern
U.S.), and coastal salt marshes.
2 For more information, see U.S. Fish and Wildlife Service, An
Overview of Major Wetfand Functions and Values (FWS/OBS-
84/18), September 1984.
3 For a more complete reference on classification of wetland types,
see Cowardin, Carter, Golet and LaRoe, Classification of
Wetlands and Deepwater Habitats of the United States,
(FWS/OBS-79/31) U.S. Fish and Wildlife Service, December
1979.
Fresh-water ecosystems, though comparatively
smaller in area than marine and terrestrial habitats,
are of great significance because they are:
- A major component in the hydrological cycle
(rivers and streams drain a large percentage
of the earth's land surface),
- A breeding and rearing habit for wildlife
species of value to people,
- A readily accessible and low-cost source of
water for domestic and industrial use, and
- A valued recreational and aesthetic resource.
In fresh-water environments, the dynamics of water
temperature and movement can significantly affect
the availability and toxicity of contaminants.
The waters in lakes and ponds have relatively long
residence times. For example, consider the Niagara
River as it flows into Lake Ontario. The Niagara's
strong currents move a given molecule of water along
the 37-mile length of the river in about one day.
However, the same molecule will remain in the lake
for several years before it flows into the St. Lawrence
River. A similar molecule will remain in Lake
Michigan for nearly a century, while another one
would remain in Lake Superior for 191 years.
In addition, temperate lake ecosystems exhibit strong
seasonal cycles. In summer, surface waters warm up
and become thermally stratified - that is, they do
not mix with the colder bottom waters. (See Figure
3.3.) As a result, nutrients released through
decomposition of animal and plant material tend to
accumulate in the bottom waters. In the fall and
spring, when these temperature differentials
disappear, the waters in the lake are able to mix,
allowing circulation of accumulated nutrients. As
nutrients are brought up into water that receives
sunlight, they become available to aquatic plants,
which can use the nutrients to support
photosynthesis. These plants provide energy that
sustains growth of most other organisms in the lake
system. At each of these seasonal shifts, the biotic
communities in the upper waters exhibit clear
successional changes in their planktonic
communities. (Plankton are small plants and
animals that float passively, or can swim weakly, in
the water column.) These annual cycles can also
greatly influence the availability of contaminants
that may reside in the lake sediments for part of the
year and be dissolved or suspended in the water
column at other times. Such contaminants may
become available to upper-water organisms during
periods of mixing.
Rivers and streams are substantially different from
lakes and ponds not only in their obvious physical
19
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Winter
Temperature
(Degrees^)
0
Depth 3
(Meters)
10
2 4 6 8 10 12 14
Oxygen (Parts Per Million)
Temperature
Oxygen
Summer
Temperature
(Degrees C)
20 25
Depth
Meters)
2468 10121416
Oxygen (Parts Per Million)
Temperature
Oxygen
Figure 3.3 Thermel stratification of a north temperate lake.
Summer conditions are shown on the right, winter conditions on the left. Note that in summer a warm oxygen-rich
circulating layer of water, the epilimnion, is separated from the cold oxygen-poor hypolimnion waters by a broad
zone, called the thermocline, which is characterized by a rapid change in temperature and oxygen with increasing
depth.
Source Figure 11-9 from Fundamentals of Eco/ogy, Third Edition, by E.P. Odum. Copyright (C) 1971 W.B. Saunders Company, A Division
of Harcourt, Brace, Jovanovich, Inc. Reprinted by permission of the publishers.
conditions (e.g., moving vs. standing water, low vs.
high degree of thermal stratification) but also in the
types of organisms that they can support, especially
in the numbers of smaller organisms and in the types
of larger plants and animals. For example, a racing
brook will have low numbers of plankton (regardless
of the concentrations of nutrients present) because
the current rapidly moves them down-stream. In the
same brook, large plants must be firmly attached to
rocks or rooted in the sediment, and fish must be
strong swimmers. In contrast, a lake or pond can
accumulate high densities of plankton, and lily pads
and slow-swimming fish can thrive. As a broad
generality, food chains and food webs in flowing
waters will have fewer links or trophic levels than
those in still waters.
Marine ecosystems are of primary importance
because of their vast size and critical ecological
functions, which maintain much of the global
environment's capacity to sustain life. The sea
accounts for some 70 percent of the earth's surface
and supports a wide variety of life forms at all depths,
especially in the areas bordering continents and
islands. Oceans are constantly in motion and always
circulating, which is critical for replenishing
nutrients and dissolved oxygen vital for marine life.
The world's oceans have pH values around 8 and
average salinity of about 35 parts per 1,000. (Fresh
water averages less than 0.005 parts per 1,000.)
The continental shelf comprises the submerged
margins of the land mass. The high concentration
and diversity of marine life found here is due to a
high level of nutrients deriving from both land and
sea bottom. Most of the world's marine fishing
grounds are on the continental shelf. The
characteristics of different types of ecosystems in this
area can affect the nature and magnitude of the
ecological risk associated with contaminants.
Intertidal environments, with their continuous
cycles of exposure and re-immersion, provide unique
physical conditions for resident organisms and for
flow and availability of contaminants. For instance, a
volatile compound introduced into a rocky intertidal
zone with considerable wave and tidal action will
volatilize into the air much more rapidly than the
same chemical released into a marsh with few waves
and little tidal action. As another example, crude oil
spilled onto the rocky, wave-swept coast of France in
the early 1970s is now difficult if not impossible to
detect; similar oil spilled about the same time along a
marsh in Buzzards Bay, Massachusetts, is still
detectable. Hence, tidal and subtidal ecosystems may
range from relatively sheltered estuaries, where
sediment deposition is the major physical condition,
to open coasts, where wind and wave exposure are the
dominant forces governing the fate of chemicals.
Estuaries are partly open bodies of water closely
associated with the sea in coastal zones, including
river mouths, bays, tidal marshes, or waters behind
barrier beaches. The mechanics of estuarine systems
are unique since they are strongly influenced by the
salt water of tides and the drainage of fresh water
from land. Tides play an important role in removing
wastes and providing food. With a continual flow of
nutrients from upstream and from nearby marine
environments, estuaries support a multitude of
diverse communities, and are more productive than
their marine or freshwater sources. They are also
especially important as breeding grounds for
numerous fish, shellfish, and species of birds.
20
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3.3 Effects of Contaminants on
Ecosystems
The introduction of contaminants into an ecosystem
can cause direct harm to organisms, or may
indirectly affect their ability to survive and
reproduce. The results of contamination may be
immediately apparent or may become noticeable only
after considerable delay. The effects of contaminants
on ecosystems are due in part to the physical and
chemical properties of the chemicals themselves, but
are also mediated by the unique combination of
physical, chemical, and biological processes occurring
in each ecosystem. In addition, populations of exposed
organisms can differ in their response to
contaminants depending on their natural tolerance
to the chemical, their behavioral and life-history
characteristics, the dose to which they are exposed,
and the exposure time. Furthermore, responses may
be transient (and therefore reversible) or permanent
(irreversible).
Ecological assessment seeks to determine the nature,
magnitude, and transience or permanence of
observed or expected effects. This must be
accomplished in an environment that is itself
changing and causing change in the organisms and
systems under study. Hence, one critical goal of
ecological assessment is to reduce the uncertainty
associated with predicting and measuring adverse
effects of a site's contaminants.
3.3.1 Reduction in Population Size
Populations change in size through births, deaths,
immigration, and emigration. Contaminants can
cause reductions in populations of organisms through
numerous mechanisms affecting one or more of these
four processes. Most obvious are increases in
mortality due to the exposure of some organisms to
lethal doses, or decreases in birth rates caused by
sublethal doses. Mortality may also increase because
a food source (e. g., a key prey species) has been
depleted, perhaps by exposure to the contaminant, or
because the contaminant allows tolerant organisms
to outcompete other species for scarce resources.
Birth rates can decline not only due to toxic effects
but also through reduction of suitable breeding
habitat or changes in the availability of high-quality
food for breeding females. Populations may also be
reduced through increased emigration or decreased
immigration if organisms can sense and avoid
contaminants in the environment, or if the
contaminants' sublethal effects cause a change in
migratory behavior.
3.3.2 Changes in Community Structure
Many communities are constantly changing.
Populations may increase and decrease with the
seasons or over longer periods. Predation and
competition among species may bring about changes
in the relative abundance of various species. Chance
events, such as severe storms, may cause sudden
increases in mortality of some species and open up
habitat for others to colonize. Underlying all of this
change, however, is a certain range of possibilities
that help to define a given community. In the absence
of a major disruption, species composition and
relative abundance in a community can be expected
to vary within definable boundaries, perhaps
cyclically or perhaps randomly.
Contaminants introduced into such systems create
new boundaries, changing the range of possibilities
in ways that are not always predictable. Because
most contaminants of concern exhibit toxic effects,
they often reduce the number and kinds of species
that can survive in the habitat. This may result in a
community dominated by large numbers of a few
species that are tolerant of the contaminant, or a
community in which no species predominate but most
of the component populations contain fewer
organisms. A contaminant need not be directly toxic
to affect community structure. If, for example, a
change occurs in the salinity or dissolved oxygen
content of an aquatic system, the new environmental
conditions may eliminate some species and favor
others, creating an entirely new species mix and food
web. For example, salinity changes in Lake Michigan
are changing the species composition of the primary
producer component of the lake community from one
dominated by green algae and diatoms to one
composed principally of blue-green algae. Because
many fish species currently in the lake are unable to
feed on the blue-green algae, this species change
portends significant shifts in other segments of the
lake community.
Contaminants may cause or induce changes in the
composition and structure of a biotic community as a
secondary effect of the changes in the size of
particular populations. These species may be a major
source of food or shelter for the rest of the community,
such as the large marine plants that give their name
to California's kelp forests. Others may be crucial in
maintaining a balance of species in a habitat. If, for
example, a key predatory species is reduced or
eliminated, the relative abundance of prey species
may change significantly. In studies where predatory
starfish were removed from an intertidal community,
the number of species of prey animals (barnacles and
shellfish) dropped from fifteen to eight. The starfish
was preventing some species from outcompeting
others because it preyed on whatever species was
most abundant. In agricultural insect pest control,
the phenomena of pest resurgence and secondary pest
outbreaks are well known. When an insecticide kills
off predatory insects along with the target pest, the
pest population sometimes rebounds to much higher
numbers than before because few predators remain to
keep it in check. Destruction of the predators may
21
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also allow populations of other plant-feeding insects
to increase beyond the limits imposed by the
predators, thus creating new pest problems.
3.3.3 Changes In Ecosystem Structure and
Function
As contaminants modify the species composition and
relative abundance of populations in a community,
the often complex patterns of matter and energy flow
within the ecosystem may also change. If certain key
species are reduced or eliminated, this may interrupt
the flow of energy and nutrients to other species not
directly experiencing a toxic effect. If plant life is
adversely affected by a contaminant, the ecosystem
as a whole may capture less solar energy and thus
support less animal life. If microbial or invertebrate
populations are disrupted, decomposition of dead
plants and animals may not occur rapidly enough to
supply sufficient mineral nutrients to sustain the
plant community.
3.4 Factors Influencing the Ecological
Effects of Contaminants
A contaminant entering the environment will cause
adverse effects if:
- It exists in a form and concentration
sufficient to cause harm,
- It comes in contact with organisms or
environmental media with which it can
interact, and
- The interaction that takes place is
detrimental to life functions.
Adverse effects may also occur if a contaminant
interacts with other chemicals already present such
as to raise the overall toxicity of the contaminated
environment. The likelihood of harm is thus a
combined function of chemical, physical, and
biological factors, depending both on the nature of the
contaminant and the nature of the environment into
which it is released.
3.4.1 Nature of Contamination
Classification of Chemicals
Chemical contaminants typically found at hazardous
waste sites are classified into groups based on the
analytical methods used to analyze for the chemicals
in question. The CLP User's Guide4divides the
contaminants commonly found at Superfund sites
into two major classifications: inorganic and organic
' User's Guide to the Contract Laboratory Program, EPA Office of
[ADD] (1988).
compounds (substances containing the element
carbon).
The CLP routine inorganic analytical group is
subdivided into two categories: heavy metals (lead,
mercury, etc.) and cyanide. For the metal analysis,
the OSC or RPM will need to determine whether they
need "total" metal analysis (sample as collected in
the field) or "dissolved" metal analysis (sample
filtered to remove particulate matter).5A large
amount of particulates in the sample matrix can
produce large differences in the analytical results
between the two analyses. The choice of analytical
method also may depend on the expected route of
exposure and the biotic species of concern at a
particular site.
The routine organic analyses are subdivided into
three categories: volatiles (benzene, vinyl chloride,
etc.), semivolatiles (phenol, naphthalene, etc.), and
pesticides (DDT, arochlors, etc.). For compounds not
routinely analyzed for, or for unusual matrices,
special analytical methods may be requested from the
CLP. The OSC or RPM should consult the CLP User's
Guide regarding the availability of special services.
New procedures are also being developed in response
to special requirements at some sites.
When requesting analytical services, the OSC or
RPM should take note of any special conditions on the
site that may make results of routine analyses
insufficient for assessment needs. For example, it
may not be possible to detect very low concentrations
of certain contaminants in a sample matrix that
contains (a) high concentrations of other
contaminants or (b) chemicals (interferents) that
coextract with the contaminants of concern.
Physical and Chemical Properties
Measurement of key physical/chemical properties of
contaminants is useful in ecological assessment for
two main reasons. First, these properties generally
govern the transport and fate of chemicals in a
particular environment. Second, for chemicals about
which little is known, these characteristics can help
the analyst identify chemical analogues among other
commonly observed compounds that may serve as
initial predictors of the novel compound's transport
and fate.
The Superfund Exposure Assessment Manual (EPA,
1988), or SEAM, provides a comprehensive
discussion of the environmental fate of contaminants
by medium. Chapter 3 of the SEAM, "Contaminant
Fate Analysis," includes both screening criteria and
quantitative methods. Intermedia transfers and
transformation are included in sections covering
'"Filtered" is operationally defined as that which passes through a
0.45 urn filter.
22
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atmospheric, surface-water, and ground-water fate,
as well as biotic exposure pathways. In addition, the
Ecological Information Resources Directory (EPA,
1989) will contain updated references for some
parameters, such as bioconcentration factors.
Frequency of Release
The ecological effects of a single or occasional release
are likely to be considerably different from those
associated with a continuous release. Frequent
release of a nonpersistent compound may have a
long-term effect equivalent to a single release of a
very persistent chemical. Occasional release may
temporarily depress an invertebrate population, but
continuous release may trigger drastic shifts in the
species composition of an ecosystem. These effects
should be carefully considered when performing
quantitative exposure analyses as described in the
SEAM.
Toxic chemicals may enter the environment, or move
among compartments of the environment, on several
possible time scales. For example, toxic discharges
from a Superfund site to a waterway may occur:
- Only once (e.g., from an accidental spill),
- Intermittently (e.g., from storms causing
nonpoint-source runoff of contaminated
soils),
- Seasonally (e.g., from snowmelt in the
spring),
- Regularly (e.g., from daily activities at the
site), or
Continuously (e. g., from ground-water
discharge to the waterway).
Some or all of these types of release may happen at a
particular site, and each type of release may cause a
different concentration and mass to enter the
waterway.
Different species of plants and animals may have
different abilities to withstand or resist intermittent
or continuous releases of toxic chemicals, so it is
important to characterize the sources in terms of the
kind of release that is occurring. For example, adults
of a species may withstand a short-term discharge
that kills all the juveniles, but be severely affected by
a regular or continuous release. If such a differential
effect were suspected, knowing the nature of the
discharge might lead to monitoring strategies that
emphasize one life stage or the other. Similarly,
chronic discharges that allow bioaccumulation of
certain toxicants may cause more lasting damage to
certain species than to others. Such releases might be
especially harmful to relatively immobile species.
Toxicity
Exogenous chemicals in an ecosystem can greatly
increase the mortality rate of component populations,
or can change the organisms' ability to survive and
reproduce in less direct ways, such as:
- Altering developmental rates, metabolic
processes, physiologic function, or behavior
patterns;
- Increasing susceptibility to disease,
parasitism, or predation;
Disrupting reproductive functions; and
- Causing mutations or otherwise reducing the
viability of offspring.
In assessing toxicity, the analyst is concerned about
two aspects. The hazard posed by a contaminant is
the effect (or endpoint), such as those mentioned
above, that the chemical (or mixture of chemicals)
can cause in the organism. The dose-response
relationship describes the amount of chemical
necessary to produce the observed effect. A broad
array of toxicity tests are available for evaluating the
effects of contaminants and their dose-response
relationships. These are summarized in the
companion volume to this manual and related
references.6
The toxicity of a substance is generally described by
the duration of exposure or the reactions it elicits.
Acute toxicity causes death or extreme
physiological disorders to organisms
immediately or shortly following exposure to
the contaminant.
Chronic toxicity involves long-term effects of
small doses of a contaminant and their
cumulative effects over time. These effects
may lead to death of the organism or
disruption of such vital functions as
reproduction.
Acute or chronic exposure can have lethal or
sublethal effects.
- Lethal doses cause death directly through
disruption of key physiological function.
Population levels are affected by the
"Ecological Assessments of Hazardous Waste Sites: A
Reference Document (EPA/600/3-89/013). EPA Office of
Research and Development 1969.
23
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contaminant if the overall mortality rate is
increased.
Sublethal toxicity entails symptoms other
than death or severe disorder, but may have
long-term effects on a population. For
example, some toxicants at low concen-
trations cause a change in the behavior of
migratory fish, interrupting their natural
habit of returning to freshwater streams to
spawn.
Evaluating the toxicity of a particular substance
requires careful specification of the endpoints of
concern, which entails describing
- The organism tested or observed,
- The nature of the effect,
- The concentration or dose needed to produce
the effect,
- The duration of exposure needed to produce
the effect, and
- The environmental conditions under which
the effects were observed.
Ecologists will often use professional judgment to
select a particular organism as an "indicator species,"
that is, a species thought to be representative of the
well-being and reproductive success of other species
in a particular habitat. The indicator species may
also be chosen because it is known to be particularly
sensitive to pollutants or other environmental
changes. In addition, ecologists will often study some
life stage of interest in the indicator species, such as:
- Reproductive success as measured by the
survival of gametes, larvae, or embryos;
- Survival of juveniles or molts;
- Longevity of adults; or
- Incidence of disease, including physiological
and behavioral abnormalities.
In studies of toxicity, certain measures are commonly
used:
- LD50or L C50 - the administered dose or
environmental concentration at which 50
percent of the experimental organisms die in
a spectified period of exposure time (often 96
hours).
- ED5?or E C50 - the dose or concentration at
which 50 percent of the experimental
organisms exhibit a certain nonlethal
3.4.2
physiological or behavioral response in a
specified time period (often 96 hours).
No Observed Effects Level (NOEL) or No
Observed Adverse Effects Level
(NOAEL) - these measures, which are not
time-dependent, describe the threshold below
which predefined effects are not observed.
When this threshold has not been
determined, the Lowest Observed Effects
Level (LOEL) or Lowest Observed
Adverse Effects Level (LOAEL) describe
the lowest recorded dosage at which effects
were observed.
Physical/Chemical Characteristics of the
Environment
A wide variety of environmental variables can
influence both the nature and extent of effects of a
contaminant on living systems. These factors -
interacting with each other, with contaminants, and
with organisms - can affect the outcome of a
contamination by:
- Chemically changing the contaminant to
make it more or less toxic,
- Making the contaminant more or less
available in the environment, or
- Making the organisms more or less tolerant
of the chemical.
Among the many factors that can affect the outcome
of contamination in the environment are
temperature, pH, salinity, water hardness, and soil
composition.
Temperature affects the chemical activity of
contaminants and biological activities of organisms
in the environment. Low temperatures may be
advantageous in certain contamination episodes,
since both chemical and biological activity may be
low. For example, low winter temperatures can
reduce the toxicity of mining effluent to
macroinvertebrates found in streams. But the same
low temperatures can be detrimental in other
circumstances. In a study of susceptibility of seabirds
to oil contamination, researchers found that an
amount of oil on the feathers too low to cause death
under normal environmental conditions was much
more stressful at colder temperatures.
The pH of the environmental medium may affect a
contaminant's chemical form, solubility, and toxicity.
This is especially true in the case of toxic metals. A
one-unit decrease in pH can cause a more than
twofold increase in lead concentrations in the blood of
exposed rainbow trout. Studies have also shown that,
24
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in general, as environmental pH decreases, the
toxicity of contaminants tends to increase.
Salinity, the amount of dissolved salts in a volume of
water, is an environmental variable to which many
marine and estuarine species are very sensitive.
Some contaminants reduce these organisms'
tolerance of normal changes in salinity, decreasing
their ability to adjust to salinity fluctuations. For
instance, one species of yearling salmon
demonstrated reduced tolerance of increases in
salinity after long-term exposure to copper.
Hardness, the amount of calcium, magnesium, and
ferric carbonate in fresh water, can affect the toxicity
of inorganic contaminants. Several Federal and State
water quality criteria and standards are dependent
on specific hardness ranges.
Soil composition can greatly affect the nature and
extent of movement and toxicity of contaminants.
Soils with a high clay-humus colloid content can
absorb high levels of certain ions and neutral
organics. The organic content of some wetland soils
can bind large amounts of heavy metals, rendering
them unavailable to the biota. Some water-insoluble
pesticides are known to adsorb to soil particles that
can then transport the chemical to surface water
when erosion occurs. Light, sandy soils readily
permit percolation of chemicals to ground water,
which may in turn contaminate surface waters.
3.4.3 Biological Factors
Susceptibility of Species
Species differ in the ways that they take in,
accumulate, metabolize, distribute, and expel
contaminants. Taken together, these traits result in
marked differences among species in their sensitivity
to contamination. For example, over 400 species of
insects and mites have developed resistance to
pesticides used to control them, while hundreds of
other species exposed to the same chemicals remain
susceptible.
Usually, the major consideration as to how species
will react to a potential toxicant is the dose.
Generally speaking, the higher the dose, the greater
is the likelihood that biological effects will occur.
However, response to a particular dose may also
depend on the duration of exposure. Some organisms
can take in higher doses of a toxic material if
exposure is spread out over time in smaller doses. For
example, in one experiment, hens were fed leptophos
(an organophosphate insecticide) in a single high
dose or a series of lower doses. At the lower but
multiple doses, the hens developed ataxia (paralysis
of the legs) later than with the single high dose, but
the total dosage over time was greater in the multiple
feeding than the single amount that caused
immediate ataxia.
Susceptibility of an organism varies with the
mechanism through which contaminants are taken
up from the environment. A given environmental
concentration may result in different actual dosages
for different species. For instance, some fish not only
take in certain chemicals through their gills as they
breathe, but can also absorb the chemicals through
their skin. Species also differ in the way in which
their bodies metabolize, accumulate, and/or store
contaminants. For example, an organism that
commonly holds energy in reserve in the form of body
fat may experience little effect from the
accumulation of fat-soluble chlorinated hydrocarbons
such as DDT. However, in a time of scarce food
supplies, the animal might then metabolize large
amounts of fat, receiving a high dose of chemical as it
does so.
In general, the susceptibility of a species to a
particular contaminant will depend primarily on:
- The rapidity with which the contaminant is
absorbed from the environment,
- The resultant dosage actually incurred at the
physiological site where toxic effects occur
within the organism (the "site of action"),
- The sensitivity of the site of action to the
dosage incurred,
- The relationship between the site of action
and the expression of symptoms of toxic
injury, and
- The rapidity of repair or accommodation to
the toxic injury.
Characteristics Governing Population Abundance
and Distribution
For a given set of environmental conditions, species
have characteristic attributes such as birth rates, age
and sex distributions, migration patterns, and
mortality rates. The species' habitat preferences, food
preferences, and other behavioral characteristics
(e.g., nesting, foraging, rearing young) also may
determine population size and distribution in an
area, and may also significantly affect the potential
for exposure.
Differences in responses to contamination due to such
characteristics may be manifest immediately. For
instance, a species with a high proportion of juveniles
in its age distribution might suffer a more precipitous
decline after a release than another species that has a
higher proportion of adults, simply because adults of
25
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a species can often sustain higher doses of a toxicant
before succumbing than can juveniles.
Alternatively, the effects of species attributes
governing population abundance and distribution
may become apparent only when the stress is
removed from the environment. Some species are
very successful at colonizing new habitats. They
typically have high rates of reproduction and short
generation times, and are able to disperse widely in
search of suitable habitat. For example, annual
weeds, often the first plants to occupy disturbed
environments, usually produce large numbers of
seeds that are easily dispersed by wind or other
means. In well established, more stable habitats,
such "pioneer" species are often poor competitors
against other species for limited resources. The
species thriving in stable environments use the
resources efficiently in the areas where they become
established, and typically have low reproductive
rates, long generation times, and often, longer life
spans. They also tend to be better competitors in the
territories they occupy. These are the species that are
more likely to recolonize a disturbed habitat only
after some considerable delay.
Species often combine characteristics of both of these
idealized types. They may exhibit high reproductive
rates and dispersal capability, along with other traits
that allow them - under the right conditions - to
outcompete later invaders. For example, in the
southern United States, the imported fire ant has
become a serious nuisance due in part to its ability to
recolonize areas where insecticides were applied to
control it. If the chemicals kill off other ant species,
the fire ant is better able than its competitors to
immigrate quickly and become entrenched in the
newly opened habitat.
Temporal Variability in Communities
The effects of a contaminant discharge into a
particular habitat may vary with seasonal or longer
cycles governing community structure and function.
Effects may be apparent immediately at one point of
the cycle (e.g., in spring), whereas at another point
the effects would be delayed. Contaminants may also
elicit different effects at different stages of a
community's development.
Seasonal changes entail relatively predictable,
ordered changes associated with organisms' life
histories, and are driven principally by cyclical
changes in weather and other physical influences.
Examples include:
- The spring blooms of plankton in estuaries
and lakes,
- The change throughout the summer in the
relative abundance of species of stream
insects,
- The appearance of successive species of
annual plants from spring to fall, and
- The concentration and dispersal of various
animal species for breeding, nesting, and
foraging.
When conducting an ecological assessment at a
Superfund site, the analyst must consider these kinds
of temporal variations when determining the
probability of exposure. Depending on the time of
year or the point in some longer cycle, a potentially
exposed species may or may not be present or in a
vulnerable life stage at the time of a chemical
release.
Successional time scales are less regular and hence
less predictable. Biological interactions or physical
changes mediated by biological activity are usually
important in the evolution of communities. The
classic example of succession is the gradual change of
a meadow to a forest. This series of events is
measured in scores of years in undisturbed
environments, and is not likely to be important in
assessment of Superfund sites. Other successional
change may be brought about by natural disturbance
or human intervention and occur more rapidly. For
example, intensive herbicide use in agricultural
production sometimes results in preferential survival
of weed species that are naturally tolerant to the
chemicals used on the site. As the herbicides continue
to kill off sensitive species, the herbicide-tolerant
weeds come to dominate the non-crop plant
community, and may in turn determine which
species of insects, small mammals, and birds inhabit
the area.
Movement of Chemicals in Food Chains
Food-chain transfer of contaminants represents a
potential exposure route that should be addressed in
assessing the ecological effects of a site. The processes
involved in accumulation and transfer of chemicals
via food webs are complex. Nonetheless, an
understanding of a few basic aspects may be helpful
in evaluating the importance of this phenomenon at a
given site:
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Elevated concentrations of contaminants in
organisms compared to environmental
concentrations may not always signal food-
chain transfer. Animals and plants
canaccumulate chemicals directly from the
medium in which they live. Bioac -
cumulation of chemicals in this manner is
especially important for aquatic organisms
and for terrestrial plants and animals (e.g.,
earthworms) in direct contact with soils.
Elevated levels of a chemical found in most
fresh-water fish and aquatic and soil
invertebrates occur by direct concentration of
the contaminant from the water, soil, or
sediment rather than through the food chain.
Certain species are more likely to be exposed
due to food-chain transfer of bioaccumulating
chemicals than others. Predators and other
species near the tops of food chains are among
the most vulnerable. Long-lived, fattier, and
larger species have a greater opportunity to
accumulate compounds in their tissues.
Species that are more sensitive to the
chemicals than the animals on which they
are preying may be at particular risk of
exposure (e.g., osprey feeding on contam-
inated fish).
Certain chemicals are more likely to be
transferred via food webs than others.
Organochlorines and other persistent organic
compounds (either parent materials or
metabolizes resistant to further degradation)
are more likely to be transferred than are
non-chlorinated hydrocarbons and metals.
Organic compounds with higher molecular
weights are more likely to be transferred
than those with lower molecular weights.
Compounds with high Log P'values are
most likely to be accumulated.
Plants may take up chemicals with low Log P
values by way of their roots, but cannot
transport significant amounts of compounds
with high molecular weights and high Log P
values in the same manner. However, foliage
can become contaminated from soil or water
by sorption of volatilized chemical on the
leaves or by deposits of dust, aerosols, and
vapors.
Longer food chains increase the time needed
to reach equilibrium levels of contaminants
in the predators at the top of the chain. The
maximum value of bioaccumulation in the
top species is also lower in longer food chains,
but there is a greater certainty that a toxic
chemical will have time to exert its effects on
the population. Table 3.1 illustrates this for
DDT applied to forest foliage. The table also
shows the shift from DDT at the low end of
the food chain to the more stable and toxic
metabolite, DDE, at the high end.
Bioaccumulation may be less than predicted
for a variety of reasons. For example,
organisms may avoid the chemical or prey
that have consumed it, or exposure time may
be insufficient to achieve equilibrium in
living tissues. Furthermore, not all food
chain transfers lead to biomagnification'.
Field monitoring should be used wherever
possible to determine actual tissue
concentrations.
For terrestrial species, bioconcentration
factors (BCFs)'°of as little as 0.03 can be
signficant if the residue is toxic. For aquatic
species, BCFs greater than 300 are generally
considered significant.
Tabla 3.1. Forest Food Chain for DDT
Receptor
Foliage
Forest litter
Litter invertebrates
Ground-feeding birds
Canopy-feeding birds
Bird-eating hawks
and owls
Source: James W. Gillett,
Chemical
DDT
DDT/DDE
DDT/DDE
DDE
DDE
DDE
Cornell University
Years to
Maximum Cone
0
1
2
4-5
5-7
7-10
'The process that results in increased concentrations of
contaminants in organisms with increasing trophic levels in the food
chain.
'The logarithm of the octanol-water coefficient (Kow). Predictor of
bioaccumulation in the oils of fish end the fat of animals.
'Higher concentration in the consumer than in the contaminated
source.
10The BCF is the ratio of the concentration of a contaminant in the
organism to the concentration in the immediate environment (soil,
water, and sediments).
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Chapter 4
The Role of Technical Specialists in Ecological Assessment
"Every site is unique."
This is probably the most common generalization on
which ecologists who have worked on hazardous
waste sites will agree. It is also only partly true.
What makes every site unique is its particular
combination of characteristics - the contaminants of
concern, the topography of the site, the presence or
absence of surface water, the vegetation, other
species present, soil types, proximity to other import-
ant habitats, etc. Taken together, these factors
present an almost infinite array of potential
ecological risk scenarios - the populations at risk, the
nature of the contaminants, their toxicity to different
species, routes and probabilities of exposure, en-
vironmental factors contributing to or inhibiting
toxicity, short- and long-term shifts in the structure
of biotic communities, and the effects of remediation
on the habitats at or near the site.
Nonetheless, ecologists are able to find common
elements in their study of populations, communities,
and ecosystems, some of which were discussed in
Chapter 3. These common elements form the basis for
designing a strategy for characterizing any indi-
vidual site and defining its specific properties. Thus,
although every site is unique, the methods for
assessing each site are not. Deciding which factors
are important, and which methods to use to assess
those factors, is a complex task requiring the ex-
pertise of ecologists who are familiar with the
organisms, ecological processes, and environmental
parameters that characterize a site. This chapter
outlines how such specialists can help the RPM or
OSC specify, obtain, and evaluate information
needed to assess ecological effects at Superfund sites.
This guidance manual presumes that the RPM or
OSC will obtain the assistance of ecologists and other
environmental specialists. In some Regions, informal
or formally constituted technical assistance groups
already exist. In other Regions, advice may be
obtained from various sources, including:
- EPA Regional Environmental Services
Divisions;
- The EPA Environmental Response Team;
- EPA Regional NEPA coordinators;
- Ecosystem-specific EPA programs, such as
the Great Lakes National Program Office in
Chicago, or the Chesapeake Bay Program
Office in Annapolis, Maryland;
- Laboratories of EPA's Office of Research and
Development; and
- Regional and field offices of the U.S. Fish and
Wildlife Service, the National Oceanic and
Atmospheric Administration (especially
NOAA's Coastal Resource Coordinators), and
other Federal and State environmental and
resource-management agencies.
Generally, technical specialists serve an advisory
role. Their function is to assist the RPM or OSC with
information collection and evaluation, and to help
ensure that ecological effects are properly considered
in investigations and decisions. In specific cases, it
may be possible to make arrangements (such as
interagency agreements in the case of non-EPA staff)
for them to be involved directly in conducting the
work.
In the following sections, we describe how ecological
specialists can contribute to the RI/FS and Removal
processes. We have divided the discussion into five
major aspects:
- Site characterization,
- Site screening and identification of
information gaps,
- Work plan development,
- Data review and interpretation, and
- Enforcement.
These divisions are made for convenience of
discussion only. Not all sites will require all five
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types of activity, and some activities may proceed in
parallel rather than sequentially.
4.1 Site Characterization
RPMs and OSCs are encouraged to consult with
ecologists as early as possible to obtain their help in
conducting an effective ecological assessment. This
assessment should begin with an ecological
characterization of the site. In the RI/FS process, this
stage corresponds with the early phases of developing
a site management strategy.
An initial site description will be necessary to orient
the technical specialists. This description should be
assembled by the RPM or OSC from existing sources
of information, without conducting formal field
studies. Its primary purpose is to allow the specialists
to:
- Identify issues that should be addressed in
the ecological assessment to follow, and
Develop data-collection strategies.
The description should include information on the
location of the site, its history, likely contaminants of
concern, and the environmental setting of the
proposed actions. Although primary responsibility
for preparing the site description lies with the RPM
or OSC, the technical specialists should provide
guidance, when requested, on what information they
need in the initial site description to allow them to
understand the scope of the problem. Much of the
information needed at this stage is commonly used
material, available from published sources or from
previous assessments of the site. For example, studies
in support of a removal action may be useful in
planning for a Remedial Investigation.
Site location. The technical specialists should be
provided with maps and descriptions of the site,
indicating, where possible:
- The geographical area (town, county,
quadrant, or other appropriate unit) around
the site;
The locations of streams or other surface
waters on or near the site;
- Locations of other ecological habitats such as
forested areas, grasslands, floodplains, and
wetlands on or near the site;
- Locations of soil types and current or
projected uses; and
Locations of contaminant sources at or near
the site.
Topographical maps published by the U.S. Geological
Survey should be provided. For areas that are
predominantly privately owned, floodplains are
delineated on the Flood Insurance Rate Maps and the
Flood Hazard Boundary Maps published by the
Federal Emergency Management Agency. For areas
that are predominantly owned by States or the
Federal government, the controlling agency can
usually provide floodplain information.
Documentation of the fact that a site exists in or near
wetlands is an important first step in the ecological
assessment. Several sources of information are
available to RPMs and OSCs to determine if a
contaminated area is in or near a wetland. Maps of
wetlands are available from a variety of sources,
including the U.S. Fish and Wildlife Service, local
and State planning agencies, and the Section 404
staffs in the EPA Regions. The National Wetlands
Inventory maps (NWI) developed by the Fish and
Wildlife Service, or other more specific information
at the State level should be consulted as early as
possible. If more exact locations and/or boundaries
are required, the Federal Manual for Identifying and
Delineating Jurisdictional Wetlands (March 1989)
should be consulted. This manual was developed to
identify Jurisdictional wetlands subject to Section 404
of the Clean Water Act and the "Swampbusters"
provision in the Food Securities Act, as well as to
identify vegetated wetlands for the NWI.
The OSC or RPM should contact the State
Geographical Information System, Information
Management Office, and Land Management Offices
for additional maps of environmental resources.
Aerial and satellite photographs that include the site
and its surroundings should also be sought out and
provided to the specialists if appropriate.
Site history and contaminants of concern. The
initial site description should include a history of the
site drawn from existing sources. Topics that should
be addressed include available information on
chemical-handling activities, storage locations, and
known or potential contaminants. If a health effects
assessment has already been performed on the site,
standard information on contaminants - chemical
composition, amounts, and locations - will also be
useful for ecological assessment. Where available,
the descriptions of chemicals should also include in-
formation on:
- Decomposition rates and products,
- Bioaccumulation potential,
- Known toxic effects, and
- Fate and transport.
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Environmental setting. The initial site description
should include any available information on geology,
hydrogeology, and ecological habitats at or adjacent
to the site. Geological information may be obtainable
from existing publications of the U.S. Geological
Survey or similar sources. Precipitation records for
nearby weather stations (often located at the nearest
airport) can be obtained from the National Weather
Service. Previous environmental analyses may be
available for some sites, which could help identify
important habitats or species for the assessment to
consider. These might include, for example, an
Environmental Impact Statement for a nearby
facility (e.g., highway, power plant), a State
Remedial Action Plan for a designated Area of
Concern, or a National Pollutant Discharge
Elimination System permit for wastewater discharge
into a nearby waterway.
Obtaining information about local ecological
resources may require consultations with local
experts on the subject, including State pollution-
control officials, State or Federal fisheries and
wildlife-management specialists, State or Federal
foresters, agricultural extension agents or Soil
Conservation Service officials, and others familiar
with the terrain and biology of the region. These
individuals may also provide important details re-
garding past, present, and likely future uses of land
and water resources in the area. The RPM or OSC
may want to consult the technical assistance group or
individual specialists for help in identifying people to
contact for this information. These contacts may also
provide assistance in identifying potential ARARs for
the site.
Using this information, the technical specialists
should be able to begin identifying the habitats
potentially affected by contaminants at the site. Key
to this activity will be a preliminary definition of the
likely pathways for exposure to the contaminants.
Once these habitats are identified, the relevant Fed-
eral and State natural resource trustees should be
notified and invited to participate in planning the
ecological assessment, if they are not already serving
as technical specialists.
If possible, one or more technical specialists should
accompany the RPM or OSC to the site for an initial
field reconnaissance. This visit can help clarify for
the assistance group the kinds and amounts of data
that may be needed to characterize the site and its
contaminants, keeping in mind that seasonal
changes may alter the nature and quantity of
releases or affected organisms.
4.2 Site Screening and Identification of
Information Gaps
Following collection of existing data, the technical
assistance group should be in a position to determine
the nature and extent of ecological assessment that
will be necessary for the site. If no ecological exposure
pathways have been revealed in this initial review,
little or no additional work may be needed. Alter-
natively, certain exposure pathways might be
eliminated from further study while others might
require more data. For instance, if there is no surface
water on the site and no opportunity for
contaminants to reach surface waters off the site,
further data on aquatic effects would very likely be
pointless, even though concern about exposure to
terrestrial organisms might warrant extensive
sampling and testing.
Examination of preliminary data could point up
important gaps in the information concerning
characterization of the site. Site visits, aerial or
satellite photographs, or information from local
experts may reveal habitats subject to exposure that
were not part of the original data-gathering effort.
For instance, careful examination of the site might
result in the discovery of a previously unreported
stream running through the property that could raise
questions about contaminants reaching an off-site
wetland.
Review of the data from initial studies may also
indicate that potential exposure pathways or
receptors were either overlooked or previously
unknown to the site investigators. For example,
evidence might be found that small mammals are
burrowing and foraging near storage facilities. This
information would probably raise concern about
direct exposure of these animals to contamination.
Depending on the persistence and bioaccumulation
potential of the contaminants, the observation of
these mammals might also suggest additional risk to
predatory birds and mammals both on and off the site
through the food chain. These concerns might then
lead to a new study plan to trap some of the mammals
and test their tissues for contaminants.
The technical specialists might also conclude from
information developed during the early stages that
the contaminants identified at the site are causing
unexpected toxic effects. For instance, biotic surveys
might show an absence of certain fish species that
occur in otherwise similar, but uncontaminated,
streams. If there is reason to suspect that the absence
of these fish may be caused by toxic effects, field or
laboratory toxicity tests might be appropriate to
determine the toxicological potential of the
contaminants.
4.3 Advice on Work Plans
Where applicable, ecological assessment is an
integral part of the RI/FS Work Plan. Technical
specialists should be consulted as early as possible in
the development of the Work Plan and the Sampling
and Analysis Plan, to ensure that the plans for eco-
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logical assessment are well designed and capable of
answering the necessary questions about the
ecological effects of the contaminants at a site.
Effective ecological assessment will require a design
that is tailored to each site's specific characteristics
and the specific concerns to be addressed. Choosing
which of the many possible variables to investigate in
the study will depend on the nature of the site, the
types of habitats present, and the objectives of the
study. The technical specialists should therefore
assist the RPM in specifying technical objectives for
the investigation. Such objectives might include:
- Determination of the extent or likelihood of
impact,
- Interim mitigation strategies and tactics,
- Development of remedies, or
- Remediation criteria.
The technical specialists can then help the RPM
develop data quality objectives to support these
technical objectives.
Although each assessment is in some way unique, it
is possible to outline the general types of data that
may be required. For terrestrial habitats, the
technical specialists may specify such data needs as:
- Survey information on soil types, vegetation
cover, and resident and migratory wildlife;
- Chemical analyses to be conducted in
addition to any previous work done as part of
a Preliminary Assessment or Site Investiga-
tion; and
- Site-specific toxicity assessments to be
conducted.
For fresh-water and marine habitats, the information
needed will most likely include:
- Survey data on kinds, distribution, and
abundance of populations of plants
(phytoplankton, algae, and higher plant
forms) and animals (fish, macro- and micro-
invertebrates) living in the water column and
in or on the bottom;
- Chemical analyses of samples of water,
sediments, leachates, and biological tissue;
- Sediment composition and quality, grain
sizes, and total organic carbon; and
- Toxicity tests designed to detect and measure
the effects of contaminated environmental
media on indicator species, or on a
representative sample of species, such as
water fleas (Daphnia or Ceriodaphnia),
amphipods, chironomid midge larvae, tubifi-
ciid worms, mysid shrimp, and fathead
minnows.
Where specialists have reason to believe that
contaminants may move from one type of habitat to
another, such as chemicals washing into a stream in
runoff water, data from each potentially exposed
habitat will be needed. The Superfund Exposure
Assessment Manual contains much valuable
information on predicting movement of contaminants
from one medium to another.
The technical specialists should also provide
guidance on such quality assurance and quality
control (QA/QC) issues as:
- The area to be covered in biotic and chemical
sampling programs,
- The number and distribution of samples and
replicates to be drawn from each habitat,
- The preferred biological analysis techniques
to be used,
- Adherence to the assumptions of predictive
models used in the analysis,
- The physical and chemical measurements
(e.g., dissolved oxygen in a water sample, pH
of water or soil, ambient temperature) to be
taken at the time of the survey, and
- Any special handling, preservation methods,
or other precautions to be applied to the
samples.
Technical specialists may make specific
recommendations on sampling and analytical
methods, or they may review plans and offer
comments or suggestions for improvement of the
assessment methodology. Ideally, the sampling and
assessment process should be a phased approach,
where preliminary results are reviewed by technical
specialists, who may find reason to suggest changes
in the scope of the project or in the methods used
during subsequent stages of the study.
4.4 Data Review and Interpretation
The technical assistance group should also be called
upon to review data and provide comments on the
interpretation of data. In most situations, extensive
and long-term ecological studies are unlikely to be
undertaken, and informed professional judgment will
be required to determine if the weight of evidence
supports a particular decision regarding the site.
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Specialists should be closely involved in reviewing
interim and draft assessments as these documents
are completed. The appropriate specialists should be
consulted to ensure that the assessments:
Address all important habitats and
contaminants of concern,
- Identify all significant receptor populations,
- Portray all relevant routes of exposure,
Characterize all significant ecological
threats, and
For instance, channeling a stream may deprive a
wetland of its primary water source; earthmoving
and construction operations may increase siltation of
nearby streams due to increased soil runoff. In such
situations, compliance with appropriate laws and
regulations may require that the remediation plan
include provisions for minimizing environmental
damage. Ecologists should therefore be involved as
early as possible in the selection and review of
remedial alternatives so that ecological as well as
public health concerns are addressed in the
Feasibility Study.
Technical specialists should also be involved in
designing monitoring programs to evaluate the
success of a removal or remedial project. Biological
monitoring plans should be developed to evaluate the
effects of remedial actions on local populations of
various forms of wildlife. In addition, toxicity tests
can be used as sensitive indicators of the presence or
absence of contaminants following remediation. Such
tests may be useful in defining cleanup levels.
- Describe uncertainties in the assessment
process.
The specialists may also provide advice on how to
present the results to decision makers who are not
trained in environmental science.
4.5 Advice on Remedial Alternatives
Remediation measures can also pose environmental
threats.
4.6 Enforcement Considerations
If ecological effects of contaminants area factor in en-
forcement actions, technical specialists may be a
valuable resource both in crafting the decision
documents and in providing support for the decision.
Proposed decisions that incorporate ecological
criteria for cleanup or remedial action should be re-
viewed by appropriate ecological experts to ensure
that the criteria (1) are accurately described and (2)
can be effectively implemented. Technical specialists
may serve as expert witnesses in court or
administrative hearings in support of enforcement
actions. Finally, as discussed above, ecologists may
be consulted on the design and implementation of
monitoring programs to help ensure that remedial
actions achieve their objectives.
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Chapter 5
Planning an Ecological Assessment
Because ecological assessments will vary widely from
site to site, no standard design is appropriate. The
scope, level of detail, and design of the assessment
should be determined in close consultation with
ecologists who understand both the technical issues
involved and the requirements of the Superfund
program. Some of the factors that should enter into
the planning stage are:
- The objectives of the assessment, as
determined by the management decisions
required at the site;
- The programmatic goals, mandated
schedules, and budgetary restrictions
associated with the site's remediation;
- The kinds, forms, and quantities of
contaminants at the site;
The means of potential or actual release of
contaminants into the environment;
- The topography, hydrology, and other
physical and spatial features of the site;
- The habitats potentially affected by the site;
- The populations potentially exposed to
contaminants;
- The exposure pathways to potentially
sensitive populations; and
- The possible or actual ecological effects of the
contaminants or of remediaractions.
This phase of the assessment process is concerned
with determining what information should be collect-
ed for an ecological assessment. It consists primarily
of identifying characteristics of the contaminants and
the potentially affected environments, to:
- Determine if enough evidence exists to
warrant further investigation of ecological
effects at the site;
- Establish the scope of the ecological
assessment (if one is judged necessary) in
terms of spatial and temporal extent, tests to
be conducted, time and resources needed, and
level of detail required; and
Define study goals and data quality
objectives if collection of new data is deemed
necessary.
If new data are collected, it is essential that data
quality objectives reflect specific programmatic
goals and management objectives, to ensure that
time and funds spent to gather and analyze data
are used efficiently and effectively.
This chapter discusses the principal components of
defining the scope and design:
- Determination of the objectives and level of
effort appropriate to the site and its
contaminants,
- Evaluation of site characteristics,
- Evaluation of the contaminants of concern,
Identification of exposure pathways, and
- Selection of assessment endpoints.
These are logically distinct activities, but they are
not necessarily undertaken sequentially. All may be
underway simultaneously, or one activity may await
the outcome of data from other activities. The
outcome of this process is the Sampling and Analysis
Plan (SAP), which specifies the methods for data
collection and analysis, and the procedures for
quality assurance and control (QA/QC).
5.1 Determination of Need, Objectives,
and Level of Effort for Ecological
Assessment
Defining the scope and design of an assessment is
initially based on available information and data
from previous studies. Using this material, the RPM
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or OSC should consult with technical specialists, who
can be expected to use good professional judgment to
provide advice on how to evaluate a specific site. The
outcome of this phase should be an assessment design
that will ensure scientific defensibility of data and
decisions based on those data, while remaining
cognizant of the CERCLA-mandated schedules and
budget constraints faced by decision makers.
An ecological assessment may be conducted to:
- Document actual or potential threat of
damage to the environment, in support of a
proposed removal action;
- Define the extent of contamination;
- Determine the actual or potential effects of
contaminants on protected wildlife species,
habitats, or special environments;
- Document actual or potential adverse
ecological effects of contaminants, as part of a
Remedial Investigation;
- Develop remediation criteria; and
- Evaluate the ecological effects of remedial
alternatives, as part of a Feasibility Study.
A given assessment may entail one or more of these
objectives as the primary reason(s) for the study.
Specification of assessment objectives should in turn
allow clear definition of the ecological endpoints of
concern, the study methods to be employed, and the
data quality objectives for the study.
The RPM or OSC should confer with technical
specialists to determine appropriate levels of detail
for ecological assessment of a site based on available
information. This should be undertaken as an
iterative process. Data from the field may warrant
further investigation and greater detail. Conversely,
such data may indicate that little or no additional
work is necessary to characterize ecological effects.
The definition phase should be used to identify the
criteria needed to make these judgments.
Each assessment will vary in the extent to which
resources, exposure concentrations, effects, and other
variables are identified and quantified. The more
serious effects found may not relate absolutely to the
amount of detail required in the assessment. The
need for detailed, quantitative information will be
driven by the difficulty in adequately characterizing
the parameters that comprise the assessment. For
instance, a fish kill might be readily traced to a high
concentration of a contaminant from a point source.
On the other hand, considerable effort might be
needed to evaluate the causes of unusually low
populations of fish in a stream that contains low
levels of diverse and dispersed contaminants.
5.2 Evaluation of Site Characteristics
5.2.1 Nature and Extent of Contaminated Area
In defining the scope and design for an ecological
assessment, it is important to determine the full
spatial extent of the contamination through
sampling and measurement. The sampling plan
should be designed with a broad enough radius to
find the "edge of the plume," the farthest extent of the
contamination in soils or other environmental media.
Maps and aerial photographs should be used
whenever possible to define the general habitats at or
adjacent to the site. Small wetlands, intermittent
streams, and other potentially important areas that
might have been missed during a preliminary site
visit may be seen from aerial photographs or maps.
Significant off-site information may also be derived
from good maps and photographs (e.g., discharges
from surrounding areas that may affect the site).
This type of information may provide significant
insight into the conduct of the site investigation.
Ground verification of all habitat locations should be
conducted before developing any sampling plans.
At this stage, it is also important to determine which
transport processes are likely to be at work with
respect to each contaminant. From this information,
analysts should be able to discern likely off-site
exposure routes and the habitats threatened or
potentially threatened by that exposure. The RPM or
OSC should consult the Superfund Exposure
Assessment Manual (SEAM) for detailed information
on predicting chemical fate and transport in the
environment.
In characterizing a site and determining how
contaminants may move through the environment
associated with the site, the RPM or OSC should
examine trend data such as variations in climatic
conditions that may affect population levels of
resident species. These data may indicate conditions,
such as periods of high rainfall or drought, that place
additional stress on local ecosystems and may affect
the fate and effects of contaminants.
Based on all of this information, and in close
consultation with technical specialists, the RPM or
OSC should set site-specific objectives for
investigation of each potentially contaminated
habitat, including
- Environmental media to be sampled and
analyzed for contaminant levels,
- Detection limits for contaminants,
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Toxicity tests to be performed and species to
be tested, and
Ecological (population, community, or
ecosystem) effects to be measured or
predicted.
Data quality objectives arising from these study
objectives should then be developed to determine
what level of effort will be necessary to obtain
scientifically defensible answers. It is important to
emphasize that the extent of delineation of exposed
habitats should be determined by the potential for
exposure, not by arbitrary distances or boundaries
that lack a biological justification.
5.2.2 Sens/five Environments
For a particular site, the project team should prepare
a list of habitats requiring special attention in the
assessment. Although ecological judgment is
necessary to define some priorities, State and Federal
laws and regulations designate certain types of
environments, such as wetlands, as requiring special
consideration or protection. Critical habitats for
species listed as threatened or endangered also may
require protection. Consultation with natural
resource trustees and other technical specialists will
be invaluable in ensuring identification of these key
areas.
In addition to identifying habitats that meet specific
State or Federal criteria, the project team should also
consider if any other habitats on the site are:
- Unique or unusual, or
Necessary for continued propagation of key
species (e. g., rare or endangered species,
essential food sources or nesting sites for
other species, spawning and rearing habitats,
etc.).
The importance of habitats on or near a hazardous
waste site will vary from area to area, depending on
such factors as:
- The species native to the area and their
significance (e.g., regionally important sport
fish),
The availability and quality of substitute
habitats,
The land use and management patterns in
the area, and
- The value (economic, recreational, aesthetic,
etc. ) placed on such habitats by local
residents and others.
The project team should define and identify sensitive
environments based on a site- and area-specific
analysis, keeping in mind the ecological connections
between the site and nearby habitats.
5.3 Contaminant Evaluation
5.3.1 Identification and Characterization
Along with site characterization, a parallel prime ob-
jective in defining the scope and design of an assess-
ment is to characterize the contaminants of concern
(and their transformation products) in terms of their
known or suspected potential to cause ecological
harm. Besides identifying and classifying the con-
taminants of concern, the RPM or OSC should make
sure that characteristics of the chemicals are mea-
sured that will help to determine the site's likely eco-
logical effects. Based on measured or calculated phys-
ical/chemical properties and other published data,
the contaminants' likely persistence in the environ-
ment should be estimated. The RPM or OSC should
also obtain information to describe the frequency, in-
tensity, and route(s) of chemical release to the envi-
ronment.
Preliminary information on the physical/chemical
properties, bioaccumulation potential, and other
characteristics of contaminants can be used to define
the parameters of studies to be conducted for an
ecological assessment. For example:
If chemicals are known or suspected to be
water-soluble, analysts should be prepared to
investigate potential exposure routes to
aquatic habitats. Water-soluble compounds
may also be expected to move readily within
the aqueous phase of some soils, increasing
the likelihood of exposure for soil-inhabiting
organisms.
For chemicals with low volubility in water,
the RPM or OSC should investigate the
potential for the compound to adsorb to soil
particles. Should this occur, the chemical
could be transported through erosive soil
runoff to surface waters or other terrestrial
environments near the site. Contaminated
soil particles may also be ingested by
organisms living on or in the ground.
- If a contaminant is judged to be persistent, or
if environmental release is frequent or
continuous, the ecological assessment may
(where time permits) include chronic as well
as acute toxicity tests on potentially exposed
organisms. The RPM or OSC may also need to
consider studies and/or use of appropriate
predictive models to assess long-term
population effects.
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If compounds are known or suspected to
bioaccumulate, studies may be needed to
determine the extent of bioaccumulation in
potentially exposed organisms. This will
probably entail a close look at transport and
exposure pathways and collecting data on
contaminant concentrations in tissues of
likely bioaccumulators such as fish.
5.3.2 Biological and Environmental
Concentrations
Based on the preliminary information about the
nature the contaminants, a sampling and analysis
plan can be devised to determine contaminant
concentrations in all relevant media. As in all other
assessments, the best measures are those that are
accurate, precise, and representative of the situation
in space and time. The best way to achieve this is to
plan sampling programs with ecological assessment
as a clearly specified objective. As a general
principle, sampling, monitoring, and measurement
should be designed by taking account of exposure
pathways to habitats and organisms on or near the
site.
A brief field reconnaissance of the site, combined
with accurate maps or aerial photographs, should be
sufficient to identify important habitats that may
require sampling. Consultation with ecologists
familiar with the area will probably indicate the
kinds of organisms to be expected on the site and the
probable exposure pathways that should be
investigated. This in turn should lead to study
designs for measuring contaminants in media
appropriate to those exposure pathways. For
instance, if a compound is known or suspected to be
volatile, air sampling in potentially exposed habitats
may be appropriate. If the chemicals are believed to
have reached surface waters, stream sediments and
biota may need to be analyzed to determine the full
extent of contamination. If biological transport of the
contaminants is considered possible, the sampling
plan may need to include testing for the presence or
effects of low levels of chemical at some distance from
the source.
If contaminants are suspected of bioaccumulation or
are considered fairly persistent, the RPM or OSC may
need to require studies to determine if the chemicals
are being transferred from organism to organism
through the food web. Food-chain linkages can be
evaluated using information on the trophic
relationships of the species at a site. Direct
measurements of chemical residues in animal tissues
provide the most direct approach for assessing the
extent to which food chain transfer of chemicals may
be occurring. If such biological transfer of
contaminants is suspected, the RPM or OSC should
consult with technical specialists on the proper
design of studies to evaluate the extent and effects of
the phenomenon.
Estimating chemical fate and transport is a key first
step in quantifying exposure. Having identified the
exposure pathways, the analyst should plan on
sampling pertinent media to determine the
concentrations of the contaminants of concern. As
discussed in detail in the SEAM, predictive models
can help in estimating fate and transport of
contaminants. For Superfund sites, the analyst
should consult the SEAM and specialists to
determine the applicability of any particular model
to the specific site. Among the considerations will be
the assumptions underlying the model, the quantity
and quality of input data needed, and the degree of
confidence in the model's results. The decision on
what model(s) to use may determine sampling and
analytical design, including analyses required,
sample sizes, sampling method, and sampling
frequency.
5.3.3 Toxicity of Contaminants
A key objective of the definition phase of the
assessment process is to develop a sampling and
analysis plan to assess the toxicity of site
contaminants to potentially exposed populations of
plants and animals. Evaluating the toxicity of a
substance at a particular site requires careful
specification of the effects of concern, such as
mortality or reproductive failure, and the duration of
exposure (i.e., acute or chronic). At the planning
stage, literature reviews are the most likely sources
of information on the toxicity of contaminants.
Literature searches can help guide an investigation,
especially in identifying the likely mechanisms of
toxicity. However, the user of a literature review
must fully understand the restricted character of the
information. Its value in characterizing actual or
probable hazards at a specific site is extremely
limited, for several reasons:
- Toxicologists generally study a population of
one species because the effects on a
community or ecosystem are too difficult for
standard practice. If the species chosen for
the study is not a good indicator species for
habitats found at the site, the study's findings
may be a poor predictor of the site's actual
hazards.
- Toxicologists generally study the effects of a
single toxicant at a time. This practice is
rarely representative of field conditions
where organisms may be stressed
simultaneously by several toxic ants,
fluctuations in the availability and quality of
nutrients, and variations in weather and
climate. When organisms are exposed to two
toxicants at the same time, the effects may be
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directly additive, more than additive
(synergistic), or less than additive
(antagonistic), depending on the toxicants in
question, the organisms exposed, and the
environmental conditions.
Published research may use death or a
subacute effect, such as behavioral change, as
the endpoint. Incorporating statistics into
their analyses, scientists may select the
median (50 percent) response of a population,
or they may choose some other percentile of
response as appropriate, perhaps the 10
percent or the 90 percent response. Unless
the measures used in the research correspond
well to the objectives of the ecological
assessment, the results may be difficult to
apply to the specific site or contaminants at
issue.
Researchers usually report a fixed time for an
experiment. For example, for aquatic tests,
toxicologists often study the response over 48
or 96 hours, depending on the species and the
toxicant. Occasionally, researchers will study
a complete generation of organisms or a
complete cycle of reproduction and
recruitment, but rarely do they have the
resources or time to study several
generations.
A wide array of experimental protocols and results
exists in the literature, in which every variation from
study to study can be found different organisms,
toxicants, laboratory conditions, endpoints,
concentrations, statistical summaries, and durations.
Although all of these studies may be informative for
some purposes, they are difficult to compare and
contrast, and judging the validity of extrapolation to
a specific site and its contaminants should be left to
qualified specialists.
Despite the wide diversity of experimental designs,
ecologists have settled on a few widely recognized
organisms and protocols for study. For example:
-To study effects on terrestrial invertebrates,
researchers commonly use one or more
species of earthworms to represent soil
organisms, generally using two- or four-week
test protocols.
Toxicology studies of birds often use bobwhite
quail, ring-necked pheasants, or mallard
ducks.
Because of their widespread use for human
health assessment, there exists a large data
base of toxicity studies on laboratory rats,
mice, and rabbits. Therefore, these are also
commonly used as surrogate species for
estimation of toxicity to other mammals.
- For equivalent studies of aquatic organisms,
scientists have long used species of Daphnia
or Ceriodaphnia (water fleas) to represent
freshwater invertebrates in 48- or 96-hour
test protocols, while freshwater fish have
been represented by the fathead minnow,
rainbow trout, and bluegill.
- The MicrotoxRtest, dissolved oxygen
depletion test, or reazurin reduction test are
sometimes used to indicate toxic effects on
microbial populations.
- Commonly studied marine and estuarine
species include mysid shrimp, Dungeness and
blue crabs, oysters, mussels, and sheepshead
minnows.
- For studies of effects on plants, domesticated
species are often used, such as lettuce seeds in
germination tests.
It is often possible to select one or more of these
commonly tested species as surrogates for species
found at a site if toxicity testing is warranted. To
develop a proper understanding of conditions at the
site, data on surrogate species need to be interpreted
by wildlife/fishery toxicologists and ecologists
experienced in evaluating contaminants. Differences
in physiology between closely related species or
apparently minor differences in physical or biological
conditions at the site can often complicate such
interpretations.
Literature surveys can help identify possible targets
for investigation if toxic effects are reported, but they
are unlikely to eliminate chemicals from further
consideration if negative results are reported.
Positive findings in a laboratory research study of
toxic effects may indicate the mode of action of the
chemical. They may also help the investigator
determine the endpoint for toxicity tests conducted
with materials from the site. Laboratory tests
indicating low toxicity may or may not mean low
toxicity in the field, since even the best laboratory
simulation cannot mirror field conditions.
Generally speaking, field data, monitoring
information, and toxicity testing of contaminated
media are more useful and reliable than literature
estimates. Wherever possible, the assessment should
be based on data collected from the field.
In those circumstances where exposure appears
likely, toxicity testing will be needed to determine
the effects of contaminants in the concentrations
found or expected at the site on potentially exposed
plant and animal populations. Results from
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published studies can serve as a useful guide for
deciding:
- What toxicity tests (e.g., acute, chronic)
should be conducted with field-collected
samples,
- What kinds of organisms should be tested,
What effects should be anticipated, and
- How the tests should be interpreted.
From these decisions, a specific set of data quality
objectives should be formulated, including:
- The number and type of tests to be run,
- The environmental conditions to be
monitored,
- The detection limits for contaminants,
The number of samples to be taken, and
- The acceptable margin of error in analyzing
results.
Site-specific information on sensitivity to
contaminants should be gathered wherever
necessary and feasible. Studies to collect such data
should be designed carefully, in close consultation
with technical specialists. The general categories of
studies that might be conducted include the
following:
- In-situ (in-field) toxicity tests. Methods for
in-situ studies are available for aquatic
toxicology and, to a more limited extent,
terrestrial toxicology. Such methods usually
involve exposing animals in the field to
existing aquatic or soil conditions. Generally,
these methods involve the use of enclosures to
hold the animals at a specific location for the
designated exposure period (e.g., caged fish
studies).
- Field observations. Correlation of the
abundance and distribution of animals and
plants with measurements of chemical
concentrations may not prove the existence of
toxic effects, but may offer some insights as to
likely sensitivities and add to the "weight of
evidence" concerning the site.
- Toxicity tests of contaminated water, soil,
sediments, or elutriates in the laboratory.
These can be used to evaluate the lethal or
sublethal effects of chemicals as they occur in
environmental media. They can also be used
to test for toxicity of mixtures as they
actually occur in the environment. Some
methods for these tests have been published
by EPA.1
5.3.4 Potential ARARs and Criteria
Once the contaminants at a site have been identified,
the RPM or OSC should identify those for which
criteria have been established, and determine
whether any such criteria apply as potential ARARs
at the site in question. (See Chapter 2.) If usable and
applicable criteria exist, the assessment should
include sampling and monitoring plans to determine
the extent to which those criteria are exceeded by
environmental concentrations at the site. If criteria
do not exist for the contaminants in question,
analysis of known toxic effects and possible threshold
levels may be used to develop site-specific criteria
against which to compare field data. The RPM or
OSC may also wish to consult with technical
specialists to determine if any chemicals for which
criteria have been established might be appropriate
analogues for the contaminants of concern at the site.
EPA's Office of Toxic Substances has published a
volume describing the use of analogues for
estimating toxicity to aquatic organisms.2
5.4 Potential for Exposure
Before the effects of a contaminant on an organism
can be evaluated, it is necessary to know how much of
the chemical is actually or potentially reaching the
point of exposure (the location where effects can
occur). This depends on characteristics of the
contaminant, the organism, and the environment.
Exposure assessment seeks to answer the following
questions:
- What organisms are actually or potentially
exposed to contaminants from the site?
What are the significant routes of exposure?
- To what amounts of each contaminant are
organisms actually or potentially exposed?
- How long is each exposure?
- How often does or will exposure take place?
'Ecological Assessments of Hazardous Waste Sites: A Field and
Laboratory Reference Document (EPA/600/389/013), EPA Office
of Research and Development, 1989; J.C. Greene, S.A. Peterson,
C.L. Bartels, and W.E. Miller, Bioassay Protocols for Assessing
Acute and Chronic Toxicity at Hazardous Waste Sites, EPA
Office of Research and Development, January 1988.
2Estimating Toxicity of industrial Chemicals to Aquatic
Organisms Using Structure Activity Relationships, Office of Toxic
Substances (EPA/560/688/001 ), July 1988.
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- What seasonal and climatic variations in
conditions are likely to affect exposure?
- What are the site-specific geophysical,
physical, and chemical conditions affecting
exposure?
Analysis of contaminant concentrations in tissues of
exposed organisms can help provide a link between
environmental concentrations and the amount of
contaminant likely to reach the site of action. For
many contaminants and organisms, time delays may
need to be considered when attempting to correlate
environmental and biotic concentrations. This will
allow for the time that may elapse before a chemical
is taken up into living tissue. Some of the factors that
may influence uptake include:
- The environmental concentration of the
contaminant in the media to which the
organism is most often exposed;
- The metabolic rate of the organism, which
in turn may be a function of such
environmental parameters as temperature,
availability of sunlight, water, nutrients,
oxygen, etc.;
- Species-specific metabolic processes, such
as food absorption rates and the ability to
degrade, accumulate, store, and/or excrete
the contaminant;
- Behavioral characteristics such as food
preferences and feeding rates (both of which
may vary with the time of year and the age of
the organism), and the ability to detect and
avoid contaminated media or food;
- Other characteristics of the organism,
such as gill surface area, lipid content, and
metabolic ability to liberate a "bound"
residue; and
- The bioavailability of the contaminant, i.e.,
its tendency to partition into a form
conducive to uptake; this will vary among
chemicals and organisms. Bioavailability
will be influenced by such environmental
factors as temperature, salinity, pH, redox
potential, particle size distribution, and
organic carbon concentrations.
Because individuals and species accumulate
contaminants differentially in their tissues,
environmental concentrations and uptake rates will
not necessarily predict biotic concentrations.
Pharmacokinetic distribution following bioaccum-
ulation determines the concentration of contaminant
that actually reaches the physiological site of action
within an organism, and thus the likelihood of
adverse effects. Whether or not bioaccumulation is
suspected, analysts should try to determine
contaminant concentrations in environmental media
and biotic tissues simultaneously. Based on these
data, site-specific bioconcentration factors (BCFs)
can be estimated. One must make sure, however, that
the measured environmental concentrations are
relatively stable and not short-term aberrations. If
site-specific BCFs cannot be derived from monitoring
data, the analyst may need to use published BCF
values or predicted BCFs.
To be meaningful, chemical analyses of biota should
use sample sizes large enough to obtain variance
estimates. Extrapolating contaminant
concentrations from a sample of organisms to an
average for the population may be a complex process.
Such factors as the time of year of the sample, the life
stage or age of the organisms, and the spatial
distribution of the population may need to be
considered. For highly mobile animals, estimates of
exposure may need to be adjusted to account for the
likelihood that not all of the animal's food will be
obtained from the affected area. In one study, for
example, the analysts calculated exposures for mink
and mallard ducks based on the assumption that the
contaminated area represented ten percent of their
home ranges. When such adjustments are made, the
analyst should clearly state the justification for the
assumptions and estimates used.
The SEAM provides detailed guidance on estimating
or predicting environmental concentrations in media
and intermedia transfers of contaminants. In
addition, it offers a brief discussion on evaluating
biotic exposure pathways to human populations.
However, the SEAM is specifically intended for
estimation of human exposure. Since human and
environmental receptors do not share all exposure
routes, the analyst will need to go beyond the decision
models provided in the SEAM to consider exposure of
environmental receptors. For example, in the
exposure assessment for contaminated soil, the
analyst will need to determine if the soil is sterile or
if it is inhabited by plants and animals. If the soil is
inhabited, the analyst will need to determine if
organisms are contaminated and, if so, what the
potential is for off-site movement of animals or food
chain transfer of contaminants.
5.5 Selection of Assessment and
Measurement Endpoints
Based on the available information concerning the
site, the contaminants, and the likely exposure
pathways, the analyst should identify and select
appropriate endpoints for the assessment. The
companion volume to this manual discusses in detail
the distinction between assessment and
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measurement endpoints.'Assessment endpoints
are those describing the effects that drive decision
making, such as reduction of key populations or
disruption of community structure. Measurement
endpoints are those used in the field to approximate,
represent, or lead to the assessment endpoint. If new
data are to be collected to evaluate these endpoints,
EPA's guidance on data quality objectives should be
followed (see Section 5.6).
5.5.1 Ecological Endpoints
Toxicity of contaminants to individual organisms can
have consequences for populations, communities, and
ecosystems. As discussed in Chapter 3, changes in
rates of mortality, birth, immigration, and
emigration can cause population sizes in an affected
area to increase or decrease. These changes can also
lead to shifts in the spatial distribution of
populations in the environment. Such population-
level effects may in turn determine the nature of
changes in community structure and function, such
as reduction in species diversity, simplification of
food webs, and shifts in competitive advantages
among species sharing a limited resource. Finally,
ecosystem functions may be affected by
contaminants, which can cause changes in
productivity or disruption of key processes. For
example, at a Superfund site contaminated with
creosote and related compounds, the analysts noted:
The presence of beds of detritus in the stream and
layers of contaminated undecomposed leaves in
the soil indicates that litter degradation is not
occurring, at least not at a natural rate.
Contaminants can disturb ecosystems in ways other
than direct toxicity. For example, a chemical that
decreases available oxygen in aquatic systems can
have catastrophic effects, whether or not it is toxic to
the organisms there. Contamination leading to
destruction of terrestrial vegetation can result in
increased sedimentation of streams, which can
adversely affect benthic populations that never come
in contact with the chemical, Remedial actions that
reduce water flow to a wetland or that replace
indigenous vegetation with introduced plant species
can remove an essential resource for one or more
species in the community. In assessing the ecological
effects of a site or its remediation, the analyst should
consider use of appropriate measures of community
and ecosystem function to determine if the weight of
evidence indicates that effects other than toxicity are
significant.
To characterize the effects of contaminants on
populations, communities, and ecosystems, the
'Ecological Assessments of Hazardous Waste Sites: A
Reference Document. EPA Office of Research and Development,
1989.
analyst may choose one or more measures depending
on the objectives of the study.
Use of these measures will usually require
comparison of the site to a carefully selected
reference area. To allow proper comparison, it is
important that reference areas be chosen that:
- Are in close proximity to the contaminated
area(s);
- Closely resemble the area(s) of concern in
terms of topography, soil composition, water
chemistry, etc.; and
- Have no apparent exposure pathways from
the site in question or from other sources of
contamination.
The RPM or OSC should consult closely with
technical specialists on specific criteria for selecting
an appropriate reference area.
The following are examples of measures that might
be used to compare contaminated and reference
areas:
- Population abundance - the number of
individuals of a species in a given area,
usually measured over a period of time or at a
specified time;
- Age structure - the number of individuals in
the population in each of several age classes
or life history stages, which can be an
indicator as to whether the population is
increasing, decreasing, or stable;
- Reproductive potential and fecundity -
expressed as the proportion of females of
reproductive age, the number of gravid
females, the number of eggs or viable
offspring per female, or the percentage of
females surviving to reproductive age;
Species diversity - the number of species in
an area (species richness), the distribution of
abundance among species (evenness), or an
index combining the two;
- Food web or trophic diversity - calculated
in the same way as species diversity, but
classifying organisms according to their place
in the food web;
- Nutrient retention or loss - the amount of
undecomposed litter or, conversely, the
amounts of nutrients lost to ground or surface
waters;
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- Standing crop or standing stock - total
biomass in an area; and
Productivity - sometimes determined in-
directly by measuring oxygen production by
the plant community per unit time; ecologists
also sometimes gauge respiration rates by
measuring carbon dioxide output per unit
time, and calculate the ratio of production to
respiration (P/R ratio) as a measure of the
efficiency of the ecosystem.
From measures such as these, specific assessment
endpoints can be established, such as "reduction in
population abundance" or "reduced fecundity." These
would then be quantified to develop site-specific
measurement endpoints, such as "significant
difference between contaminated and reference areas
with respect to numbers of organisms or numbers of
young per female."
The analyst should use these measures with a great
deal of caution. If differences appear in the above
measures between contaminated and
uncontaminated areas, it is a complex task to
demonstrate that the effect observed is the result of
contamination rather than some other factor.
In planning an ecological assessment, the OSC or
RPM will be concerned with potentially affected
habitats and, through them, potentially affected
populations. Within each of these categories, a set of
characteristic endpoints will need to be considered,
and special types will elicit particular attention.
5.5.2 Evaluation of Potentially Affected Habitats
Habitats in the vicinity of a Superfund site can be
affected by:
- Direct or indirect exposure to the site's
contaminants due to transport from the
source;
Physical disruption of the habitat due to the
site's design or operation;
Chemical disruption of ecosystem processes
due to the contaminants' interference with
natural biochemical, physiological, and
behavioral processes;
- Physical or chemical disturbance or
destruction due to cleanup or remedial
activities; and/or
Other stresses not related to the site or its
contaminants, such as extreme weather
conditions or air pollution.
Each of these types of effects will be manifested
differently in different ecosystems, depending on the
magnitude of the disturbance and the nature of the
habitat receiving the disturbance. The various types
of terrestrial, aquatic, and marine ecosystems each
have their own particular structures, dynamics,
energy flows, and transport mechanisms that
determine how they are affected by chemical or
physical insult such as might occur at a Superfund
site.
Structure and Dynamics
Planning an ecological assessment should consider
collection of qualitative and (where feasible)
quantitative information about the structure and
dynamics of biotic communities that are potentially
threatened, with sufficient detail to:
Decide whether a detailed ecological
assessment is necessary,
- Develop a defensible professional judgment
as to the likelihood of contamination and
adverse effects, and
Define study goals and data quality
objectives for an ecological assessment if it is
justified by the preliminary evidence.
When considering study objectives for an ecological
assessment, the RPM or OSC may wish to specify
that data be collected to support calculation of certain
measures of community structure and function.
These include determining species diversity and
community productivity. It is important to recognize
that such measures were not designed for the purpose
of estimating or demonstrating environmental harm,
and they may be inappropriate for many sites. When
these measures are used, they should not be relied
upon to the exclusion of other information; rather,
they may add to the weight of evidence supporting a
particular conclusion about a site and its
contaminants. Used properly, in close consultation
with technical specialists, these measures may help
to:
Delineate the extent of contamination at a
site, and/or
Document the ecological effects of
contamination.
Measures of biotic diversity have often been used to
aid in characterizing community structure. The use
of these measures in the context of hazardous waste
sites rests on the premise that a disturbed or stressed
area will exhibit changes in the composition and
relative abundance of species as compared to a
reference area that appears not to be contaminated.
When using diversity indices or measures of
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community structure, the analyst should choose for
study those segments of the ecosystem that are likely
to:
Be exposed to the contaminants of concern,
and/or
- Contain organisms suspected of being
vulnerable or sensitive to those contaminants
or the effects of remediation.
Thus, for example, if the chemicals are present in
surface soils, it would probably be useful to apply
diversity comparisons to the soil or leaf litter
organisms at a potentially affected site and a
reference area.
The Office of Research and Development volume,
Ecological Assessments of Hazardous Waste Sites: A
Reference Document, contains detailed discussions of
assessment and measurement endpoints for
evaluating community and ecosystem level effects.
Significance and Uniqueness
The significance or uniqueness of an environment is
often a subjective judgment, that may be determined
by social, aesthetic, or economic considerations. Some
environments, such as critical habitats for
endangered species, are defined by law. To the extent
that these concerns can be spelled out in the
definition phase, they should be articulated with
regard to any such habitats. Generally speaking,
environments may be considered significant because,
in the professional opinion of technical specialists,
they:
Are unusually large or small,
- Contain an unusually large number of
species,
Are extremely productive (such as an
important fishery),
Contain species considered rare in the area,
or
- Are especially sensitive to disturbance.
In defining the scope of an ecological assessment,
consideration of such environments should be similar
to that given to rare and endangered species (see
below). These areas may have unusual underlying
physical and chemical characteristics that may affect
removal and remediation decisions. The existence,
location, and sensitivity of such environments should
be noted, and study objectives may need to be
developed to reflect the potential exposure of these
special areas to contamination.
5.5.3 Evaluation of Potentially Affected
Populations
Productivity and Abundance
Ecologists use the word "productivity" to mean the
rate at which new biomass is produced per unit time.
Plant stress may be a useful indicator of reduced
productivity in an affected area. Visual inspection of
the site during an initial visit may be sufficient to
identify probable stress on terrestrial vegetation
(such as yellowing, leaf drop, or other symptoms), but
it is important to bear in mind that the cause could be
something other than toxic effects of the
contaminants. Reduction in the growth of plants in
terrestrial or aquatic habitats will not be as easily
observed and may require a detailed botanical survey
in comparison to a reference area to be verified.
Bioassays may need to be conducted to determine if
the productivity of the plant community is being
affected, and whether or not contaminants from the
site are implicated. Toxic effects may be determined
in tests using algae or easily grown terrestrial plants
as test species. Seed germination, root elongation and
morphology, and plant growth assays can be used to
evaluate contaminated soils' effects on plant
development.
Toxic chemicals may exhibit a wide range of effects
that can ultimately influence productivity and
abundance of animals. Effects of contaminants on
animal productivity can be assessed through the use
of field ecological studies, on-site toxicity tests, and
laboratory tests. Study designs and data quality
objectives for field and laboratory studies should be
developed to determine exposure concentrations and
their likely relation to observed or suspected effects.
The RPM or OSC should seek out trend data such as
population fluctuations of key species over time. Such
information may be available from State and Federal
fish and game personnel, or from previous
environmental analyses (such as an Environmental
Impact Statement) conducted in the vicinity of the
site. These data can assist analysts in distinguishing
between normal fluctuations and changes that may
be attributable to the effects of contamination.
Rare, Threatened, and Endangered Species
By definition, endangered and threatened species are
already at risk of extinction: the loss of only a few
individuals from the population may have significant
consequences for the continued existence of the
species. In the definition phase of the assessment
process, the presence of threatened or endangered
species, and/or habitats critical to their survival,
should be documented. If information is available on
these or related species' sensitivity to contaminants
of concern, this should also be indicated. The RPM or
OSC should consult with Federal and State natural
44
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resource trustees or other specialists to determine the
location of such species and their potential for
exposure to the contaminants.
Rare species may present a more difficult problem for
ecological assessment. A species may be rare in a
given locale because:
- The area is at the edge of the species'
principal geographical range,
The natural habitats available in the area
are only marginally able to support the
species,
- The species may be prevented from attaining
high numbers by competition from other
species or by predation, or
The species depends upon rare habitats or
food sources for its continued existence.
If a species is rare, but not legally designated as
either threatened or endangered, the RPM or OSC
will have to depend on consultation with local
ecologists and other experts to determine the
importance of the species in the context of the site.
The major sources of information on rare, threatened,
and endangered species are field offices of the Fish
and Wildlife Service (U.S. Department of Interior)
and the National Oceanic and Atmospheric
Administration (U.S. Department of Commerce),
officials of State fish and game departments and
natural heritage programs, and local conservation
officials and private organizations.
Potentially Affected Sport or Commercial Species
In planning an ecological assessment, the analyst
should note potential effects on species that are of
recreational and commercial importance. In addition,
species such as food sources that directly support
these important species, and habitats essential for
their reproduction and survival, should be considered
in the planning and assessment process.
Information on which species are of recreational or
commercial importance in an area can be gathered
from State environmental or fish and wildlife
agencies, Federal agencies such as NOAA and the
U.S. Fish and Wildlife Service, and local
conservation and fish and game personnel.
Commercial fishermen's and trappers' associations
may also be valuable sources of data.
Most States maintain fish stocking programs for
sport or commercial fisheries. The agencies running
these programs can provide information on where
fish are stocked and released, and the areas to which
they migrate. Many States also gather creel survey
data for stream reaches or other bodies of water, and
collect harvest data for management of deer, game
birds, and other animals.
5.6 Sampling and Analysis Plan
The planning stage of the ecological assessment
process culminates in the Sampling and Analysis
Plan (SAP), which consists of a Field Sampling Plan
and a Quality Assurance Project Plan (QAPP). In
directing the preparation of the SAP, the OSC or
RPM should be satisfied that the following questions
are answered:
- What are the specific objectives of the sampling
- How will the proposed data collection meet those
objectives?
Will the sampling plan (types, number,
distribution, and timing of samples) provide
sufficient information to meet the objectives?
- Does the sampling plan address all important
exposure pathways and environmental receptors?
- Does the sampling plan make the best use of
preexisting data and sampling locations?
- Is the sampling of the various media associated
with the site coordinated to allow maximum
integration of the data (e.g., to measure or predict
intermedia transfer of contaminants)?
5.6.1 Field Sampling Plan
To address all of these issues effectively, a Sampling
and Analysis Plan should be developed that takes
account of:
- Actual or potential sources of contaminant
release,
- The media to which contaminants can be or are
being released,
- The organisms that can come into contact with
the contaminants, and
- The environmental conditions under which
transport and/or exposure may be taking place.
Identification of exposure routes and media should
lead in turn to a selection of the most appropriate
plant and animal species to be sampled for analysis of
contaminant concentration, toxicity testing, or other
measures of potential effects. If food-chain transfer of
contaminants is suspected, information on the
trophic structures of affected ecosystems will be
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needed to determine which species should be
examined for chemical residues.
completeness, and representativeness of the data are
known and documented.
Biological data to be collected in conjunction with
these analyses may include such parameters as dry
weight of tissues or organisms, percent moisture,
lipid content, and the size and age or life stage of the
organism. Contaminant concentrations may need to
be expressed relative to the whole-body weight
(sometimes minus the intestines) or weight of the
edible portion (for input to human health studies).
Depending on the media to be sampled, the
contaminants of concern, and the organisms under
study, the sampling plan will also require collection
of data on environmental conditions at the time of the
study. For aquatic systems, these include:
- Water quality parameters such as hardness,
pH, dissolved oxygen, salinity (for marine
ecosystems), temperature, presence or absence of
thermocline, color, dissolved organic carbon,
conductivity, and total suspended solids;
- Hydrologic characteristics such as flow rate,
ground-water discharge/recharge rates, aquifer
thickness and hydraulic conductivity, depth,
velocity and direction of current, tidal cycle and
heights, and surface water inputs and outflows;
and
- Sediment parameters such as grain size
distribution, permeability and porosity, bulk
density, organic carbon content, pH, color,
general mineral composition, benthic oxygen
conditions, and water content.
For studies of potentially contaminated soil,
information will be needed on such parameters as
particle size, permeability and porosity, fraction and
total organic carbon, pH, redox potential, water
content, color, and soil type.
The OSC or RPM should consult the SEAM and
technical specialists to determine the specific set of
environmental parameters that should be measured
to permit effective analysis of contaminant fate,
transport, exposure, and effects.
5.6.2 Quality Assurance
EPA policy requires that all Regional Offices,
program offices, laboratories, and States participate
in a centrally managed quality assurance (QA)
program. This requirement applies to all
environmental sampling, monitoring, and
measurement efforts mandated or supported by EPA
through regulations, grants, contracts, or other
formal means. Each program office or laboratory that
generates data must implement minimum
procedures to ensure that the precision, accuracy,
To ensure that these responsibilities are met
uniformly across the Agency, each EPA program
office or laboratory must have a written Quality
Assurance Project Plan (QAPP) covering each
monitoring or measurement activity within its
purview. These Quality Assurance and Quality
Control (QA/QC) requirements apply for all
monitoring at all Superfund sites or at any location
where toxic substances have been released to the
environment.
QAPPs are written documents for all planned
sampling or monitoring at a named location,
including ecological assessments of Superfund sites.
The program office, Regional Office, contractor,
grantee, State, or other organization must prepare
and receive written approval for the QAPP for the
specific sampling and measurement program before
the field or laboratory work can begin.
The QAPP presents, in specific terms, the policies,
organization, objectives, functional activities, and
specific QA/QC activities designed to achieve the
data quality goals for single or continuing activities.
The QAPP must cover all environmentally related
measurements, including but not limited to:
- The measurement of physical, chemical, or
biological variables in air, water, soil, or other
environmental media;
- The determination of the presence or absence of
pollutants or contaminants in waste streams or
site media;
The assessment of ecological effects studies;
- The study of laboratory simulation of
environmental events; and
- The study or measurement of pollutant transport
and fate, including diffusion (i.e., dispersion and
transport) models.
The QAPP serves two important functions. First, it
seeks to ensure that as much as possible is done at the
beginning of a study to achieve the QA objectives for
the data. Second, it allows for analysis of the study to
determine what improvements can be made if QA
objectives are not met. The plan cannot guarantee
results, but it requires the analyst to justify a
particular approach before proceeding.
For each major measurement variable, the QAPP
must state specific data quality objectives. This is
usually accomplished by preparing a table listing the
variable, the sampling method, the measurement
method, the experimental conditions, the target
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precision (measured in relative standard deviation),
the target accuracy (measured in acceptable relative
deviation from the true value), and the completeness
(measured in terms of percent coverage). The RPM or
OSC should also require project analysts to specify
clearly:
- What tests are to be performed,
What measurements are to be taken, and
How the results will be used (e.g., estimate
exposure, correlate diversity or abundance with a
chemical gradient, predict population response to
ambient contaminant levels).
Consultation with a technical assistance group to
define data needs and study goals is essential for the
successful specification of data quality objectives.
The ecological assessment is not a research project
and thus should not be expected to entail long-term
field studies. With the guidance of technical
specialists who understand both the scientific
questions at issue and the exigencies of the
Superfund program, it is possible to define carefully
delineated studies to collect the data needed for
making reasoned judgments on Superfund sites.
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Chapter 6
Organization and Presentation of an Ecological Assessment
This chapter provides a checklist of the basic ques-
tions that should be asked in an ecological
assessment. It is intended to ensure completeness and
consistency in the reporting of assessment results.
The amount of detail required in a given report will
depend upon the scope of the study, as determined in
the iterative planning process discussed in Chapter 5,
and the amount of data collected in the investigation.
Regardless of the level of detail, the assessment
report should be clear and concise, to ensure that the
results are readily understood and properly
interpreted.
To aid Agency review of assessments, metric units
should be used throughout. These include
specification of appropriate units in chemical
quantification such as ug/1, ug/g, etc., instead of
mixing ratios such as ppb or ppm.
Some information, such as characterization of the
site or the contaminants of concern, may have been
given in other sections of a report such as an RI or
Action Memorandum. If so, the information can be
referenced; however, the analyst may wish to
summarize such information in the ecological
assessment section.
6.1 Specify the Objectives of the
Assessment
As discussed in Section 5.1, an ecological assessment
may be undertaken for a variety of reasons, from
evaluating the threat posed by a site to examining
the effects of remedial alternatives. For example, for
two sites evaluated by EPA's Environmental
Response Team, the assessment objectives were
stated as follows:
The main objective of this. . . investigation was to
generate data that could be utilized for the
determination of site cleanup criteria for the
creosote contaminated soils and sediments in the
floodplain of the Creek.
The objective of this study was to determine if the
arsenic compounds, present in the water and
sediments of the River watershed
are resulting in an adverse ecological impact. The
data collected [were] utilized in conjunction with
existing data to determine the bioavailability
and toxicity of arsenic contamination to the
resident aquatic biological communities, and [to]
quantitatively assess impacts.
6.2 Define the Scope of the Investigation
This section of the report should describe the kind
and amount of information that was collected in the
study. The analyst should describe the data in terms
of the physical, biological, and chemical parameters
measured, estimated, or calculated in the
assessment. It is also important to specify the time
frame of the study:
- Over what time period(s) and in what season(s)
were the data collected?
- At what time intervals were samples taken?
- Were the data used to assess current effects or
past damage, or to predict future scenarios?
The discussion gives the reader a clear indication of
the nature, depth, and boundaries of the
investigation. Was the assessment, or the data used
in the assessment, based on long-term studies of the
site and its surroundings or do the data provide a
"snapshot" of the site in a restricted time period? Was
the sampling extensive or limited to specific areas?
Are the analyses reasonably straightforward or are
considerable inferences and professional judgments
involved?
6.3 Describe the Site and Study Area
In this section, the analyst should provide a physical
description of the site at a level of detail appropriate
to the scope of the assessment. The study area for an
ecological assessment may extend well beyond the
boundaries of the area in which hazardous wastes
have been stored or released. For example, depending
on the available pathways for exposure and the
habitats potentially exposed to contamination, the
area under investigation might include portions of
several tributaries of a potentially affected river, a
49
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wetland downhill or downstream from a release
source, or a wildlife refuge within the same drainage
basin as a waste site.
The description should include the size of the area (in
metric units) within the physical boundaries defined
for the assessment and the size of physical features
such as stream reaches, roads, wetlands, or forested
areas. The report should provide a map of the area,
showing all physical features at a minimum resolu-
tion equivalent to a 7.5' USGS quadrangle map,
marked to show any changes to the topography up to
the present time. This map should include all
potentially affected areas linked to the contaminated
zone by pathways of concern through any media,
sampling locations, and any reference areas selected
for the investigation. An example of such a map is
given in Figure 6.1.
A brief description of the contamination that led to
listing of the site, or a reference to such a description
should be included, giving dates where possible.
The description of the site and study area should
provide a full accounting of the ecosystems and
populations potentially exposed to contamination.
This may be accomplished with a narrative
description of each habitat (e.g., oak-hickory forest,
Spartina salt marsh, etc.), accompanied by lists or
tables of species collected or observed there. The
resident and transient flora and fauna should be
described, or if catalogued, the table can be
referenced. Where relevant, it should be noted if a
cited species is:
- Resident, breeding, or a rare or frequent
transient (e.g., migratory waterfowl),
- Endangered or threatened, or
- A natural resource trustee concern.
The significance, uniqueness, or protected status of
potentially exposed ecosystems (as discussed in
Chapter 5) should also be noted and documented.
Other information with possible bearing upon the
ecological characteristics of the site should be
provided, such as current or projected land uses;
proximity to population centers, industry,
agriculture, or hunting areas; and special climatic
conditions affecting movement, availability, or
effects of contaminants.
Finally, the site description should include narrative
characterizations of:
- Likely or presumed exposure pathways, such as
surface water, air, soils, sediments, or vegetation;
and
- Any readily observed effects potentially
attributable to the site, such as stressed or dead
vegetation, fish kills, or unusual changes in
species composition or distribution in a habitat.
6.4 Describe Contaminants of Concern
The ecological assessment should specify which
contaminants at a site are of particular concern from
an ecological perspective. This list may differ
somewhat from those contaminants that raise ques-
tions about human health risks. For example, a given
chemical may exhibit low toxicity toward mammals
but be highly toxic to fish, invertebrates, or plants.
The fate of a contaminant in the environment may
make it unavailable for human exposure while in-
creasing exposure for other organisms. For instance,
a chemical that is found to be adsorbing to soil and
sediment particles may pose little risk to humans,
but may cause considerable disruption of terrestrial
vegetation or benthic invertebrates.
Results of chemical analyses should be presented in
tabular form, identifying compounds and the media
in which they were found. If tables of data from the
human health evaluation are used by reference, it is
important to report measurements of parameters
affecting the toxicity to biota, such as alkalinity or
total organic carbon. It is important to note the
source of all analytical data, including laboratory,
CLP certification, sampling and analytical method,
and date of analysis. Data may be summarized, but
both the mean and range should be included, along
with an explanation of how and why calculations
were made. The report should explain how non-
detects, replicates, duplicates, etc. were treated in the
statistical analysis. All sample data should be
accounted for: infrequency of detection (rarity) is an
unacceptable explanation for culling a particular
data item from the sample. The report should
describe both laboratory and field analysis of
contaminants, along with variances from detection
limits that affect the applicability of the data to the
study.
6.5 Characterize Exposure
This section should identify actual and potential
exposure pathways, taking into account
environmental fate and transport through both
physical and biological means. The analyst should
consult the Superfund Exposure Assessment Manual
and technical specialists to make sure that all likely
exposure pathways have been considered. In
discussing the investigation of exposure pathways,
the report should describe each pathway by
chemical(s) and media involved, and identify the
pathway in space and time with respect to the site
and the period of investigation. If contaminant
concentrations and effects data (such as toxicity tests
or population studies) correspond to identified
50
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il3~M/\\v (
•y^sw/sppy
Legend
... Ground Contour
Surface Water and
SW/SD01 Sediment Sampling Location
«— Stream
a Structure
Approximate Boundary
0 ~ 400
Scale in Feet
Phase I Surface Water and
Sediment Sampling Locations
Figure 6.1 Example of study area map.
pathways by spatial or temporal gradient, their
presentation should demonstrate the correlation.
If sampling stations have been selected to measure
concentrations of contaminants along likely exposure
pathways, the sampling data should be presented in
such a way as to allow the reader to see quickly the
relationship between a sample's location and its
contaminant levels. For instance, stations can be
numbered in a sequence that indicates their relative
distance from the source of contamination, as shown
on a map of the study area. Another method is to
present the data on a scatter diagram, in which
sampling locations are shown as points on a graph
with distance from the source given on the X-axis and
concentrations on the Y-axis. Ideally, concentrations
of key contaminants should be displayed in graph
form with geographic locations indicated (see Figure
6.2) or on a map (see Figure 6.3).
Results of toxicity tests may also be effectively
displayed using maps. For example, in a study of the
effects of PCBs and other contaminants at a
Northeastern site, the researchers showed the results
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Arsenic Concentrations in Various
Fractions at Water Sampling Sites
500
400
300
200
100
Arsenic Concentration (ug/l)
Total Arsenic
Dissolved Arsenic
Particulate Arsenic
Detection Limit
(10 pg/l)
ERT-2 ERT-4 ERT-5 ERT-6 ERT-8
Figure 6.2 Graphic display of contaminant concentration.
ERT-9 ERT-10 ERT-11
of toxicity testing on a map of the affected area
(Figure 6.4). This type of presentation makes readily
apparent the relative hazard associated with
different locations.
If such gradients are not apparent, or are
contradicted by other data, the analyst should discuss
the possible reasons for the discrepancy in the report.
If exposure pathways are modeled, the report should
clearly state the limiting assumptions of the model(s)
used. A full reference for every model used in the as-
sessment should be included. The analyst should
characterize the uncertainty associated with all
parameters that are measured or modeled, and
specify statistical significance levels for quantitative
results.
If the analysis uses data from toxicity tests,
population studies, or other effects-related
investigations, to demonstrate that exposure has
occurred, the report should carefully explain the
limitations of the data. For instance, the site and
reference area might differ in terms of the degree of
physical disturbance, which may account for some of
the observed effects. If toxicity test results are
presented in the form of LD50s or ED50s, they should
be shown graphically on a log probit scale.
6.6 Characterize Risk or Threat
In characterizing risks or threats to environmental
receptors associated with Superfund sites, the
analyst should try to answer the following questions:
- What is the probability that an adverse effect will
occur?
- What is the magnitude of each effect?
- What is the temporal character of each effect
(transient, reversible, or permanent)?
- What receptor populations or habitats will be
affected?
Depending on the assessment objectives and the
quality of the data collected, the answers to these
questions will be expressed quantitatively,
qualitatively, or a combination of the two.
If water quality or other criteria have been exceeded
at a site, this may be sufficient in some cases to
justify remediation. In presenting the data, the
analyst should document the number and location of
sampling results that exceed the acute and/or chronic
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Soil and Sediment Total
PAH Concentrations
0 8
(Located Upstream)
(2360)- Surface (< 15cm) Total
PAH Concentrations (mg/kg)
(5435)- Depth (> 15cm) Total
PAH Concentrations (mg/kg)
50ft
Figure 6.3 Map display of contaminant concentrations.
criteria for the protection of the species and habitat of
concern at a site. The number of exceedences can be
compared to the number of total measurements for
each contaminant in a table. In addition, the
locations of all exceedences and the locations of all
measurements can be shown with different symbols
on a map. Use of a map can be especially helpful if
contaminant concentrations form a reasonably clear
gradient leading away from the source.
Beyond criteria exceedences, however, risk
characterization is most likely to be a weight-of-
evidence judgment. The analyst should present a
summary of the risk-related data concerning the site,
including
- Environmental contaminant concentrations,
- Contaminant concentrations in biota,
- Toxicity test results,
- Literature values of toxicity,
- Field surveys of receptor populations, and
- Measures of community structure and ecosystem
function.
If the contaminants at the site are exerting a clear
effect, the data from all of these studies will, on
balance, support the conclusion that an effect is
occurring. If the data are ambiguous, the analyst
should try to discern the reasons for conflicting re-
sults and present those reasons along with the
rationale for the conclusion reached.
Ecological risk characterization entails both
temporal and spatial components. In describing the
nature and probability of adverse effects, the analyst
should also consider such questions as:
- How long will the effects last if the contaminants
are removed? How long will it take for receptor
populations to recover from the effects of the
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100% Mortality Rate in Adults
63% Mortality - Eggs
(2,600 ppm Total RGBs")
26% Mortality-Adult
60% Mortality in Progeny
(Hatched Fish)
85% Mortality in Eggs
(220 ppm Total PCBs*)
Mortality-Eggs
(17 ppm Total PCBs*)
Legend
A Sediment Sample Location
• Trisponder Station Location
Reference.
1 % Mortality in Progeny
31% Mortality in Eggs
(0.03 ppm Total PCBs*)
* Mean PCB Concentration
SumationCL1-CL10.
Jv._(10 ppm Total PCB's*)
Toxicity of
Sediments to the Fish
Cyprinadon Variegatus
3,000
' 6,000 Feet
Figure 6.4a Map display of toxicity test results.
54
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100%
(2,600 ppm Total PCBs*)
92.2% _1
(220 ppm Total PCBs*)
g'.'" Coggeshal St.
Rte. 195
Legend
A Sediment Sample Location
• Trisponder Station Location
Reference:
(13.3% 0.03 ppm Total PCBs*)
* Mean PCB Concentration
SumationO.1 -CLIO.
73.3%
fc-^"". (56 ppm Total PCBs*)
65.5%.
(32 ppm Total PCBs*)
46.7% _'r POP6S IS'and * -^-Rte. 6
(17 ppm Total PCBs*) .'
Percent Mortality of
Sediments to the Amphipod
Ampelisca Abdita
3,000
1 6,000 Feet
Figure 6.4b Map display of toxicity test results.
55
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contaminants? Will there be intergenerational
effects?
Will the contaminants move beyond the current
area of study through biotic transport? What
effect will remediation have on this movement?
If there are community and ecosystem effects of
the ontamination, is removal of the
contaminants sufficient to restore community
structure and ecosystem function? If not, what
else will be needed?
- How do the data on exposure and observed or
predicted effects relate to the rapidity of response
required? Which responses are required
immediately? Which can or should be undertaken
later?
- What limits will proposed remediation or
mitigation actions place on future options for
further remediation, follow-up assessment, and
resource use?
Questions like these will most likely be answerable
only in narrative form, as an expression of best
professional judgment by a qualified ecologist.
Nonetheless, they lie at the heart of ecological
assessment. Many populations and ecosystems
exhibit considerable resilience in the face of
disturbance; in fact, change is more common in
ecosystems than stability. Populations are
continually increasing and decreasing due to natural
cycles and chance occurrences. In many situations,
when a source of contamination is removed, natural
systems will rapidly recover their former appearance.
Hence, for the same amount of chemical released, the
risk associated with an acutely toxic but short-lived
chemical may be considered important but less so
than a moderately toxic chemical that is highly
persistent.
6.7 Describe the Derivation of
Remediation Criteria or Other Uses
of Quantitative Risk Information
If water quality or other criteria are available for
comparison to observed concentrations of con-
taminants, the analyst should try to show the data
along with applicable criteria so that exceedences are
easily apparent. Table 6.1 is an example of this kind
of presentation. If criteria exceedences occur along a
clearly identified gradient, the data may best be
presented in a map.
Remediation criteria may also be derived from risk
information developed for use under other
environmental statutes, such as the Toxic Substances
Control Act or the Federal Insecticide, Fungicide and
Rodenticide Act. If the report recommends remedi-
ation criteria based on such information, the analyst
Table 6.1. Example of Presentation of Criteria Exceedences
Mean and Maximum Surface Water Concentrations (ug/l) in On-
Site Lakes at a Landfill
Chemical
Observed
Concentrations
Mean Maximum
Water Quality
Criteria'
Acute Chronic
Ammonia
Copper
Cyanide
Iron
Zinc
Phenol
160*
16
NE
125
20
NE
6,800*
50*
0.04*
1 ,300*
150*
2.1*
20
48
ND
300
30
1
20
29
ND
300
30
1
'Federal, state, or county criteria used as available
Key NE = Not evaluated
ND = No detectable amount permitted
= Criteria exceeded
should give a full reference citation for the source of
reference doses, standards, or risk assessments use in
calculating the criteria. In addition, the analyst
should provide an explanation of, or reference for, the
calculation method used to develop the criteria.
Equations and parameters (such as exposure factors)
used in the calculations should be provided in the text
or referenced.
6.8 Describe Conclusions and Limitations
of Analysis
Assessment of Superfund sites will depend primarily
on the weight of evidence supporting particular
conclusions, since ecological effects seldom occur in
isolation from other stresses. To accomplish this, it
may be necessary to use a variety of measurements in
an effort to establish that a trend is likely in the data.
For example, in a study of an arsenic-contaminated
site and a nearby river system, the analysts
compared several different indices of species
diversity for benthic invertebrates (Figure 6.5) and
examined differences in the trophic structure at the
various sampling locations (Figure 6.6). Analysts
next combined these data with information on
contaminant concentrations and toxicity tests. They
concluded that arsenic concentrations in the stream
sediments were significantly affecting benthic inver-
tebrates downstream from the contamination source.
In presenting conclusions from an ecological
assessment, the analyst should address the degree of
success in meeting the objectives of the evaluation.
The report should present each conclusion, along
with the items of evidence that support and fail to
support the conclusion, and the uncertainty
56
-------
o.
s-.> o
OQ -
II
3 ra in-
-§
ERT-2 ERT-4 ERT-5 ERT-6 ERT-8
Branch River
Sam pie Location
Comparison of Various Diversity Indices Calculated for the
Benthic Invertebrate Sampling Locations
Figure 6.5 Graphic display of species diversity indices.
50
Composition of Functional Feeding Groups at
Benthic Invertebrate Sampling Sites
Percent Composition
40
30
20-
10-
0
I Shredders
I Predators
n Collectors CD Scrapers
GM3 Piercers • Misc. Omnivores
1
ERT-2 ERT-4 ERT-5
Branch
ERT-6
ERT-8
River
Figure 6.6 Graphic display of trophic structure.
accompanying the conclusion. Analysts should also
describe factors that limited or prevented
development of definitive conclusions.
The process of assessing ecological effects is one of
estimation under conditions of uncertainty. To
address this necessary reality, the analyst should
provide information that indicates the degree of
confidence in the data used to assess the site and its
contaminants. In summarizing assessment data, the
RPM or OSC should specify sources of uncertainty,
including:
- Variance estimates for all statistics;
- Assumptions underlying use of statistics, indices,
and models:
The range of conditions under which models or
indices are applicable; and
Narrative explanations of other sources of
potential error in the data (e. g., unexpected
weather conditions, unexpected sources of
contamination).
Ecological assessment is, and will continue to be, a
process combining careful observation, data
collection, testing, and professional judgment. By
carefully describing the sources of uncertainty, the
analyst will strengthen the confidence in the con-
clusions that are drawn from the analysis.
57
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