vvEPA
United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
Publication 9345.0-051
December 1991
ECO Update
Office of Emergency and Remedial Response
Hazardous Site Evaluation Division (OS-230)
Intermittent Bulletin
Volume 1, Number 2
Ecological Assessment of Superfund Sites:
An Overview
This document is the second issue of the ECO Update
series of Intermittent Bulletins, published by the Toxics
Integration Branch, Hazardous Site Evaluation Division,
Office of Emergency and Remedial Response. Practical
experience with the process of ecological assessment at
Superfund sites has pointed to the need for information and
guidance concerning both the scientific and management
aspects of ecological assessment. The ECO Update series is
intended to fill this need.
Ecological Assessment of 'SuperfundSites: An Overview
is an updated framework for ecological assessment in the
Superfund program. As such, it offers a description of
ecological assessment components and a discussion of how
they fit into the Remedial Investigation and Feasibility
Study (RI/FS) process. Ecological assessment in the re-
moval process will be addressed in a future ECO Update.
The ECO Update Series
ECO Updates are a series of Intermittent Bulletins intended
to facilitate ecological assessment of Superfund sites. Each Bulle-
tin focuses on one aspect of ecological studies or ecological
assessment in the remedial process. Individual Bulletins may
discuss either technical methods or the management of ecological
assessments.
Limiting each Bulletin to a specific topic allows flexibility for
the user to select only those Bulletins that are applicable to the site
in question or the user's needs. For example, some sites do not
require toxicity tests, so investigators would not need to consult
Bulletins specific to testing. A user who needs only general
information on Natural Resource Trustees can refer to a specific
Bulletin on that topic and not have to look through a larger
document containing other, less relevant information.
The Bulletin series is written for both general and technical
audiences, which includes EPA site managers and staff, contrac-
tors, State personnel, and anyone else involved in the performance,
supervision, or evaluation of ecological assessments in Superfund.
Ecological assessment involves considerable professional
judgment. The ECO Updates assume that readers will confer
with qualified scientists for site-specific advice. These Bulletins
are not step-by-step guides on how to accomplish an assessment.
The series supplements the advisory process involving Regional
Biological Technical Assistance Groups (BTAGs). EPA staff
should consult their BTAG coordinator for more detailed infor-
mation on ecological assessment in their Region.
IN THIS BULLETIN
Background 2
What is an Ecological Assessment? 2
Ecological Assessment in the RI/FS Process 6
ECO Update is a Bulletin series on ecological assessment of Superfund sites. These Bulletins serve as supplements to Risk Assessment Guidance
for Superfund, Volume II: Environmental Evaluation Manual (EPA/540-1-89/001). The information presented is intended as guidance to EPA and
other government employees. It does not constitute rulemaking 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 these Bulletins.
Printed on Recycled Paper
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Background
The Comprehensive Environmental Response, Compensa-
tion, and Liability Act (CERCLA), as amended, requires EPA to
remediate uncontrolled hazardous waste sites in ways that will
protect both human health and the environment. To fulfill this
mandate, the National Oil and Hazardous Materials Contingency
Plan (NCP) requires that the baseline risk assessment, which is
conducted during the Remedial Investigation andFeasibilityStudy
(RI/FS), "characterize the current and potential threats to human
health and the environment."1 The NCP also specifies that
"[e]nvironmental evaluations shall be performed to assess threats
to the environment, especially sensitive habitats and critical habi-
tats of species protected under the Endangered Species Act."2
In December 1988, the Office of Emergency and Remedial
Response (OERR) and the Office of Waste Programs Enforcement
issued a joint memorandum to Regional Divisions responsible for
Superfund, directing that "thorough and consistent" ecological
assessments be performed at all Superfund sites in both the
removal and remedial programs. In particular,-the directive called
on the Regions to incorporate ecological assessment into the RI/FS
stage during development of the work plan, and to discuss the
ecological assessment in the Proposed Plan for site remediation.
To assist the Regions in implementing this policy, OERR
issued the Superfund Environmental Evaluation Manual3 in March
1989 to provide site managers with a general framework for
understanding the ecological assessment process. The manual is
predicated on the understanding that ecological assessment com-
bines careful observation, data collection, testing, and professional
judgment. Hence, the manual's principal goal is to introduce the
subject to site managers and encourage them to seek the advice and
assistance of the Regional BTAGf
What is an Ecological
Assessment?
The Environmental Evaluation Manual defines ecological
assessment as:
. . . a qualitative and/or quantitative appraisal of the
actual or potential effects of a hazardous waste site on
plants and animals other than people or domesticated
species.
In practical terms, ecological assessment comprises four
interrelated activities:
• Problem Formulation—qualitative evaluation of contami-
nant release, migration, and fate; identification of contami-
nants of concern, receptors, exposure pathways, and known
ecological effects of the contaminants; and selection of
endpoints5 for further study.
• Exposure Assessment—quantification of contaminant re-
lease, migration, and fate; characterization of exposure
pathways and receptors; and measurement or estimation of
exposure point concentrations.
• Ecological Effects Assessment—literature reviews, field
studies, and toxicity tests, linking contaminant concentra-
tions to effects on ecological receptors.
• Risk Characterization—measurementorestimationofboth
current and future adverse effects.
These components of ecological assessment are illustrated in
Figure 1. As the diagram indicates, each element in the process can
affect others. In reality, investigators frequently find that the
components do not always follow one another in a stepwise
manner, and may actually find themselves working on aspects of
all four components at the same time.
Problem Formulation
Problem Formulation defines the objectives and scope of the
ecological assessment. This component of an ecological assessment
primarily involves a review of existing data (including previous
studies of the site, such as the Preliminary Assessment, Site
Inspection, RI Field Investigation, and other sources). Its end
product is a conceptual model that identifies the environmental
values to be protected, the data needed, and the analyses to be used.
The problem formulation component may be difficult to
distinguish from exposure assessment or ecological effects assess-
ment. This situation arises from elements (e.g., effects andreceptors)
shared among these three components. Problem formulation dif-
fers from the other two components in the level of detail and
quantification. The difference lies in the distinction between
identification (i.e., naming and listing) of these common elements
and characterization (i.e., description and quantification). In
problem formulation, investigators:
• Focus on collecting preliminary information necessary to
design the exposure and ecological effects assessment, and
• Identify data needed to complete those assessments.
Continued on page 4
140 CFR Part 300.430 (d)(4).
2 40 CFR Part 300.430(e)(2)(i)(G).
3 U.S. Environmental Protection Agency, Risk Assessment Guidance for Superfund, Volume II: Environmental Evaluation Manual
(EPA/540-1-89/001), 1989.
4 These groups are sometimes known by different names, depending on the Region, and not all Regions have established BTAGs.
Readers should check with the appropriate Superfund manager for the name of the BTAG coordinator or other sources of technical
assistance in their Region.
5 An endpoint is an expected or anticipated effect of a contaminant on an ecological receptor. Endpoints are discussed at greater length
in the section on Problem Identification.
December 1991 • Vol. l,No.2
ECO Update
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Ecological Assessment of Superfund Sites: Overview
Figure 1
PROBLEM FORMULATION
Qualitatively evaluate contaminant release, migration, and fate
Identify:
Contaminants of ecological concern Exposure pathways
Receptors Known effects
Select endpoints of concern
Specify objectives and scope
EXPOSURE ASSESSMENT
Quantify release, migration, and fate
Characterize receptors
Measure or estimate
exposure point concentrations
ECOLOGICAL EFFECTS
ASSESSMENT
• Literature
• Toxicity testing
• Field studies
RISK CHARACTERIZATION
• Current adverse effects
• Future adverse effects
• Uncertainty analysis
• Ecological significance
I
REMEDIAL OBJECTIVES
I
ANALYSIS OF
REMEDIAL ALTERNATIVES
I
REMEDY SELECTION
RECORD OF DECISION
REMEDIAL DESIGN
REMEDIAL ACTION
ECO Update
December 1991 • Vol. l.No.2
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Qualitative Evaluation of Contaminant Release,
Migration, and Fate
This portion of problem formulation describes what is known
about contaminated media, contaminant movement, and the geo-
graphical extent of current and future contamination. Ecological
considerations for contaminant release, migration, and fate include:
• Ground water discharge to surface water and wetlands,
Transport of contaminated sediment,
Runoff from and erosion of contaminated soils, and
Bioaccumulation and bioconcentration.
Identification of Contaminants of Concern
Not all contaminants warrant equal attention with regard to
risk. Further, not all contaminants that pose human health risks are
important with respect to ecological risk—and vice versa. Factors
to consider in identifying a contaminant of ecological concern
include its:
• Environmental concentration in media (soils, surface wa-
ter, ground water, sediments, air, and biota) representing
ecological exposure pathways;
• Frequency of occurrence, defining the prevalence of the
contaminant in site media;
• Background levels, indicating the concentrations that can-
not be attributed to the site;
• Bioavailability, or presence in a form that can affect
organisms;
• Physical-chemical properties, such as volatility and
solubility;
• Potential for bioaccumulation or bioconcentration, based
on its physical-chemical properties and its tendency to occur
in biota at higher concentrations than the surrounding
environment;
• Potency, or the amount of toxicant capable of producing
adverse effects; and
• Effects, such as acute lethality or sublethal responses (e.g.,
reproductive impairment).
Identification of Exposure Pathways
Based on the analysis of contaminant release, migration, and
fate, investigators identify potential exposure pathways for eco-
logical receptors. An exposure pathway is the link between a
contaminant source and a receptor. In evaluating exposure path-
ways, the analyst should consider all media (ground water, surface
water, sediments, soils, air, and biota) that are or could be contami-
nated. For example, exposure may be the result of direct contact
with contaminated media (e.g., dermal, uptake through gills,
ingestion) or exposure through the food chain. Investigators should
consider all potential receptors when identifying exposure pathways.
Identification of Receptors
Receptors are individual organisms, populations, or commu-
nities that can be exposed to a contaminant. Identification of
receptors arises from a review of the fate, migration, and potential
release of contaminants. Ecologists begin by identifying poten-
tially exposed habitats on or near the site using a wide variety of
methods, including field reconnaissance, aerial photography, sat-
ellite imagery, and a review of previous studies to accomplish this
task. As they identify potentially exposed habitats, ecologists
develop lists of species known or likely to occur in each habitat.
Identification of receptors should include:
• Species considered essential to, or indicative of, the healthy
functioning of the habitat (e.g., stream invertebrates);
• Rare, endangered or threatened species on or near the site; and
• Species protected under Federal or State law (e.g., Migratory
Bird Treaty Act, Marine Mammal Protection Act).
Identification of Known Effects
Many sources, including data bases and publications, contain
information on ecological effects of contaminants. For example,
EPA's Ambient Water Quality Criteria (AWQC) Documents and
AQUatic Toxicity Information REtrieval (AQUIRE) data base
contain peer-reviewed data describing effects of contaminants on
aquatic (freshwater and marine) organisms. Data on terrestrial
effects and aquatic information not included in the AWQC docu-
ments or AQUIRE are available in the published literature. Where
appropriate, data on chemicals similar but not identical to site
contaminants can help characterize likely effects. Modeling tech-
niques, such as Quantitative Structure Activity Relationships
(QSAR), sometimes help in identifying surrogate chemicals for
data collection. These methods require specialized expertise to
ensure proper selection of surrogates and interpretation of results.
Site managers should obtain information from other investi-
gations conducted on or near the site, to help target the ecological
assessment toward the most relevant questions. Examples of such
information include:
• Field or laboratory studies from previous investigations of the
site;
• Corroborated reports of unusual events such as fish kills,
other animal mortal!ty, highly stressed vegetation, or absence
of species that experts would expect in the habitat; and
• Fish or wildlife consumption advisories issued by State or
local government agencies.
Selection ofEndpolnts
Investigators next identify effects requiring further study.
These are known as endpoints. Risk assessors distinguish between
two types of endpoints. An assessment endpoint describes the
effects that drive decision making, such as reduction of key
populations or disruption of community structure. Measurement
endpoints approximate, represent, or lead to the assessment end-
point, using field or laboratory methods.6 An assessment endpoint
often has more than one measurement endpoint associated with it.
Most studies have more than one set of assessment and measurement
endpoints.
The critical step in selecting endpoints is deciding what
effects are important to remedial decision making. The assessment
6 Glenn W. Suter II, "Ecological Endpoints," Chapter 2 in USEPA, Ecological Assessment of Hazardous Waste Sites: A Field and
Laboratory Reference (EPA/600/3-89/013).
December 1991 • Vol. l,No.2
ECO Update
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endpoint should reflect a potentially significant ecological impact.
Primary criteria for selecting measurement endpoints are based on
their usefulness in linking field or laboratory data to the assessment
endpoint.
For example, the assessment endpoint for a particular site
might be the probability of a significant reduction of a fish
population. The measurement endpoint used to arrive at such a
probability might be the chemical concentration shown to cause a
reduction in survival, growth, or reproduction in a standard labo-
ratory toxicity test.
Ecologists often select more definitive site-specific measure-
ment and assessment endpoints during the exposure assessment
component Information on contaminant migration, fate, and other
factors, discussed below under "Exposure Assessment," influ-
ences the choice of appropriate endpoints.
Specifying Objectives and Scope
The purpose of the activities described above is to identify the
preliminary objectives and scope of the ecological assessment and
additional data needed to complete the assessment This is critical
to the assessment process. It ensures that data collection, field
studies, laboratory tests, and the overall assessment can answer the
questions relevant to making remedial decisions.
Ecological assessment is an iterative process. As such, in-
vestigators often must revise the objectives and scope of the
ecological assessment as they collect and analyze site data. Using
such information, they can identify a need for more study, different
studies, or fewer studies.
Exposure Assessment
Exposure assessment quantifies the magnitude and type of
actual and/or potential exposures of ecological receptors to site
contaminants. The key elements in exposure assessment are
• Quantification of contaminant release, migration, and fate;
• Characterization of receptors; and
• Measurement or estimation of exposure point concentrations.
Exposure assessment often involves considerable effort and
technical expertise to complete. Site managers should consult with
their Regional BTAG to identify specific approaches for evaluat-
ing ecological exposure.
Quantification of Release, Migration, and Fate
In the Exposure Assessment phase, investigators develop
estimates of current and future contaminant levels in affected
media, including all relevant spatial and temporal characteristics
of the contamination. These estimates can then be used to deter-
mine exposure point concentrations (discussed below).
Direct sampling of media yields information on the current
location and concentration of contaminants. Fate-and-transport
models predict the movement of contaminants from the source and
between media. Site managers should consult their BTAGs and
other Regional specialists about sampling design, sample place-
ment and timing, and the availability and selection of models
applicable to their sites.
Characterization of Receptors
Most sites requiring ecological assessments contain a large
number of species, populations, and communities—from microbes
to mammals, from algae to trees. Evaluating risks for each and
every species present is impossible. To develop a reasonable and
practicable evaluation, the investigator focuses on a limited number
of receptors for the assessment Ecologists select these receptors
based on the endpoints of concern and specific characteristics of the
site under study.
In characterizing receptors, investigators collect information
(primarily from published literature) on the species' feeding habits,
life histories, habitat preferences, and other attributes that could
affect their exposure or sensitivity to contaminants.
Exposure Point Concentrations
After identifying receptors, and selecting a subset of those
receptors, investigators estimate the concentration of contami-
nant^) in the media to which the receptors are exposed. This is
known as the exposure point concentration, which investigators
measure in the environmental medium or estimate using assump-
tions and/or fate-and-transport modeling.
The amount of contaminant a receptor takes in depends on
such factors as:
• The properties of the contaminant,
• The way the organism assimilates it (e.g., direct absorption,
ingestion),
• The nature of the receptor (e.g., behavior, life history), and
• The physical/chemical properties of the media (e.g., pH,
hardness, organic carbon content).
If a contaminant is known or expected to bioconcentrate or
bioaccumulate, investigators collect and analyze samples from
biota at two or more trophic levels (e.g., plant, herbivore, carnivore)
along with surrounding media. Risk assessors use this information
in two ways:
• Directly, as exposure point concentrations for dietary expo-
sure pathways for ecological receptors; or
• Indirectly, for calculating site-specific bioconcentration fac-
tors (BCFs) or bioaccumulation factors (B AFs) to predict the
food-chain transfer of contaminants to organisms at higher
trophic levels.
Ecological Effects Assessment
This component concerns quantitatively linking concentra-
tions of contaminants to adverse effects in receptors. Literature
reviews, field studies, and/or toxicity testing provide this "dose-
response" information: that is, how much toxicant is associated with
how much of an adverse effect.
Literature Reviews
Organisms differ widely in their ability to tolerate toxicants,
depending on several factors, including environmental conditions,
the nature of the chemical, the age and reproductive status of the
organism, and inherent differences among species. Literature re-
ECO Update
December 1991 • Vol. l,No.2
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views can provide specific dose-response information for the
species under study.
Dose-response information is useful in risk characterization
(discussed below) or as the basis for further ecological effects
studies. By comparing measured concentrations of contaminants
in site media with literature values for adverse effects, investiga-
tors can decide whether they need to proceed with site-specific
investigations such as field studies or toxicity tests.
Field Studies
Ecological field studies offer direct or corroborative evidence
of a link between contamination and ecological effects. Such
evidence could include:
• Reduction in population sizes of species,
• Absence of species normally occurring in the habitat,
• Presence of species associated primarily with stressed habitats,
• Changes in community diversity or trophic structure, and
• Incidence of lesions, tumors, or other pathologies.
Ecologists usually compare data on observed adverse effects
to information obtained from a reference area not affected by
contamination from the site. For instance, for a stream contami-
nated by a waste site, the reference site might be an area upstream
from the source of contamination, or a nearby uncontaminated
stream with similar physical characteristics.
Investigators must collect chemical and biological data si-
multaneously. This allows them to determine if a correlation exists
between contaminant concentrations and ecological effects.
Toxicity Testing
Toxicity tests evaluate the effects of contaminated media on
the survival, growth, reproduction, and metabolism of test organ-
isms. When ecologists review test results along with data on
chemical concentrations and biological observations from field
studies, they often find convincing evidence that observed or
predicted effects are attributable to the presence of hazardous
substances. Investigators also use toxicity tests to demonstrate the
spatial extent of contamination and identify areas of high contami-
nant concentrations.
Risk Characterization
The science of risk assessment in ecology has not evolved to
the point where scientists can make standard risk calculations for
common risk scenarios, as they often do in human health evalua-
tions at Superfund sites. Risk characterization in ecological assess-
ment is a process of applying professional judgment to determine
whether adverse effects are occurring or will occur as a result of
contamination associated with a site.
Risk characterization is primarily a process of comparing the
results of the exposure assessment with the results of the ecological
effects assessment Available methods (either quantitative or
qualitative) seek to answer the following questions:
• Are ecological receptors currently exposed to site contami-
nants at levels capable of causing harm, or is future exposure
likely?
• If adverse ecological effects are observed or predicted, what
are the types, extent, and severity of the effects?
• What are the uncertainties associated with the risk
characterization?
The risk characterization concludes with a risk description,
which (1) includes a summary of the risks and uncertainties, and
(2) interprets the ecological significance of the observed orpredicted
effects. The risk description is a key step in communicating
ecological risks to site managers and decision makers. When
ecologists interpret and communicate ecological significance for
the risk description, they should consider such factors as the nature
and magnitude of the effects, the spatial and temporal distribution
of the effects, and the potential for recovery.
Ecological Assessment in the
RI/FS Process
Because the RI/FS supports risk-management decision mak-
ing, assessment of ecological risk plays an essential role. Figure 2
shows where ecological information is necessary in the RI/FS and
post-RI/FS activities.
Scoping of the RI/FS
Scoping of the ecological assessment should begin with, and
be included as part of, the overall RI/FS scoping process to:
• Help identify the kinds of remedial decisions that site man-
agers need to make,
• Determine the types of ecological data investigators need to
support decision making, and
• Design field and/or laboratory studies for collecting those
data.
Ecologists should participate in developing a conceptual
model of the site. The ecological portion of this model is developed
during theProblemFormulationphaseoftheecological assessment
Ecological assessment can be a complex undertaking. For this
reason, site managers need to consult with their BTAGs while
preparing work scopes. For most sites, Remedial Project Managers
should develop a phased approach to the ecological assessment
with expert review at each phase. In this way, investigators can use
data or observations from one phase to determine the most appro-
priate studies for the next phase.
Continued on page 8
December 1991 • Vol. l,No.2
ECO Update
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Ecological Assessment in the RI/FS Process
Figure 2
If"' 'BstablishroeBtof
PROBLEM
FORMULATION
Review ecological
data collected from
site inspection and
other studies
Review sampling/
data collection
plans
Formulate
preliminary
remediation
goals
Determine level
of effort for base-
line ecological
risk assessment
Refine
remedial goals
based on
risk assessment
and ARARs
CONDUCT BASELINE ECOLOGICAL
ASSESSMENT
• Exposure Assessment
• Ecological Effects Assessment
• Risk Characterization
Conduct risk
evaluation of
remedial
alternatives
Ecological
Monitoring
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RI/FS Site Characterization
The Site Characterization phase of the RI/FS requires a
baseline risk assessment, which includes an ecological assess-
ment. The purposes of this ecological assessment are to:
• Describe the observed or potential magnitude of adverse
ecological effects at the site and the primary cause of the
effects, and
• Characterize the ecological consequences of the "no further
action" remedial alternative.
Site managers should ensure that ecological studies for the
baseline risk assessment are completed during the field investiga-
tion phase of site characterization.
Feasibility Study
Ecological information contributes to the Feasibility Study
(FS) process by assisting decision makers in the assessment and
selection of remedial alternatives. In developing preliminary
remediation goals (PRGs), investigators must address the results
of the ecological assessment and other ecological issues specified
in criteria, guidance, and applicable or relevant and appropriate
requirements (ARARs).
Most FSs examine numerous remedial alternatives. In such
cases, site managers must screen the alternatives to narrow the
list that will be evaluated in detail. The ecological assessment
helps this detailed analysis of alternatives by identifying risks or
benefits of each with respect to ecological receptors. The
analyses and conclusions of the ecological assessment can pro-
vide information on:
• The effectiveness of the alternative in reducing ecological
risks associated with contamination, and
• The ecological effects that may result from the remedial
action (e.g., habitat destruction).
The ecological assessment can provide information for eco-
logical monitoring during remedial and post-remedial activities.
For detailed advice on applying ecological information to the FS
process, site managers should consult their Regional BTAGs. D
December 1991 • Vol. l,No.2
ECO Update
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