United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
Publication 9345.0-051
EPA540-F-94-014
PB94-963305
September 1994
v>EPA ECO Update
Office of Emergency and Remedial Response
Hazardous Site Evaluation Division (5204G)
Intermittent Bulletin
Volume 2, Number 3
Field Studies for Ecological Risk
Assessment
Ecological risk assessments of Superfund sites evaluate
the actual or potential effects of site contaminants on plants and
animals and assess the need for remediation, including consid-
ering remedial alternatives and evaluating ecological effects of
remediation. Such ecological risk assessments make use of a
variety of desktop, laboratory, and field approaches, which may
include chemical analyses of media, toxicity testing, literature
searches, evaluation of the condition of organisms, and ecologi-
cal field studies. As the name implies, ecological Held studies
are investigations that take place in the actual area under
scrutiny, focusing on the site's habitats and biota1 (resident
organisms) and comparing them with unimpacted conditions.
The ecological risk assessment of a Superfund site nearly
always requires some type of field study. At a minimum, some
field study is necessary in order to identify organisms and
habitats2 that may be at risk. By themselves, hazard indices
based on literature values rarely prove adequate for character-
izing ecological effects.
Rather than studying individual organisms, field studies
generally focus on populations or communities. Populations
are groups of organisms belonging to the same species and
inhabiting a contiguous area. Communities consist of popula-
tions of different species living together. For example, a forest
community consists of the plants, animals, and micro-organ-
isms found in a forest. A community also can be a more
restricted group of organisms. Within the forest, the soil com-
munity consists of only those organisms living in, or in close
association with, the soil. Less frequently, a field study evalu-
ates an ecosystem, which consists of both the organisms and the
nonliving components of a specific, limited area.3 In the case of
a forest, the ecosystem includes the soils, rocks, streams, and
springs as well as the resident organisms that make up the forest
community.
Which sites warrant a detailed field study? At many sites,
the existing information indicates a significant likelihood of
present or future adverse impact but is insufficient to support
remedial decision making. At such sites, field studies can
identify actually or potentially exposed organisms, exposure
routes, ecological effects, and also the potential of the site to
support biota. In the initial phase of an ecological risk assess-
ment, a field study can take the form of a site reconnaissance
visit by an ecologist. The ecologist can record the site's habitats
and many of its species and also note any obvious adverse
ecological effects. If a site warrants further field study, a more
'The first time that a technical term appears, it is bolded and
either defined in the text or in a footnote.
2 A habitat is the place that a species naturally inhabits.
3 Although ecologists often use this term to include much larger
resources, this definition gives the word dimensions usable at a
Superfund site.
IN THIS BULLETIN
The Organisms in a Field Study 3
Elements in the Design of a Field Study 5
Catalogue of Field Methods 9
Field Studies: Their Contribution 10
ECO Update is a Bulletin series on ecological risk assessment of Superfund sites. These Bulletins serve as supplements to RiskAssessment Guidance
for Superfund, Volume II: Environmental Evaluation Manual (EPA/540-1-89/001). The information presented is intended to provide technical
information 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.
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intensive effort during the analysis phase can help to provide
evidence of a link between a site's contaminants and an adverse
effect. As Table 1 shows, field studies can contribute information
at different stages of the ecological risk assessment and can assist
with each of the assessment's three components: problem formu-
lation, analysis, and risk characterization.4
The specific role of field study in an ecological risk assess-
ment varies with the site. Site managers5 should consult with the
Biological Technical Assistance Group (BTAG) in their Region to
determine the best approach to each site.6 This consultation should
occur at the earliest possible stage of site investigation. The BTAG
may suggest other methods—in addition to, or instead of, tech-
niques discussed in this document—that are especially appropriate
for a particular site.
This Bulletin provides site managers with an overview of
field study options. Four main sections follow this Introduction.
The first considers the organisms, which are the major focus of
most field studies, and the second describes the remaining ele-
ments in the design of a field study. The third section presents a
catalogue of common field study methods, while the fourth section
summarizes the contributions that field study can make to an
ecological risk assessment.
This Bulletin is intended only as a quick reference for site
managers, not as a comprehensive review of field methods or of the
ecological attributes evaluated using these methods. Those who
want to examine the subject in greater depth should consult the list
of references at the end of the Bulletin and also the list of additional
resources available from the federal government.
Table 1. Field Study Contributions to Ecological Risk Assessments
Task
Problem
Formulation
Analysis
Risk
Characterization
Site Reconnaissance Visit
Identify ecological
components potentially
exposed to contaminants.
Identify ecological
components likely to be
exposed to contaminants.
Identify readily apparent
effects.
Develop hypotheses of
relationship between
exposure and effects.
Intensive Field Study
Identify specific ecological
components and the
exposure pathways for
populations and
communities.
Describe populations and
community attributes
with respect to exposure.
Quantify exposure of specific
ecological components.
Quantify effects on
specific ecological components.
Characterize and document links
between exposure and effects.
Quantify relationship
between exposure and
effects.
4 In preparing this Bulletin, every effort was made to use the terminology found in the Framework for Ecological Risk Assessment (U.S. EPA. 1992.
Office of Research and Development, Risk Assessment Forum. EPA/630/R-92/001. Washington, D.C.). The three phases listed in the text are equivalent
to the four components of an ecological risk assessment described in "Ecological Assessment of Superfund Sites: An Overview" (ECO Update Vol. 1,
No. 2). The Framework's analysis phase corresponds to the "Overview's" exposure assessment and the ecological effects assessment phases.
5 Site managers include both remedial project managers and on-scene coordinators.
6 These groups are sometimes known by different names, depending on the Region. Readers should check with the appropriate Superfund manager
for the name of the BTAG coordinator or other sou rcesof technical assistance in their Region. A more complete description of BTAG structure and function
is available in "The Role of BTAGs in Ecological Assessment" (ECO Update Vol. 1, No. 1).
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The Organisms in a Field Study
Although a large number of species can inhabit a site, an
ecological risk assessment of a Superfund site concerns itself only
with those that are actually or potentially adversely affected by site
contamination or that can serve as surrogates for such species.
Such organisms are among a site's ecological components. Eco-
logical components are populations, communities, habitats, or
ecosystems actually or potentially affected by site contamination.A
field survey conducted as part of a reconnaissance visit can help to
identify the potentially affected organisms at a site. Some factors
to consider in making this identification include which media (e.g.,
soil, surface water, ground water) have become contaminated, the
site's contaminants, their environmental concentrations, and their
bioavailability.7
General Considerations in Selecting
Organisms for Study
Most sites have a large number of resident species, making it
necessary for the investigator8 to focus on a limited number of
these for detailed study. A variety of site-specific factors—includ-
ing the size of the site and the types of habitats that have become
contaminated—contribute to making this selection. In their role as
protectors of natural resources, trustees also can influence the
selection of organisms for study.
Species-specific factors also enter into the selection. These
include:
• Intensity of exposure. Species vary in the intensity of their
contact with contaminated media. For example, earthworms
and other invertebrates inhabiting a contaminated medium
receive longer and more intense exposures than wider-rang-
ing invertebrates such as butterflies. Some animals have
limited mobility early in their life cycle—as eggs, larvae, or
nestlings, for example—so have greater exposure than older
animals.
• Relative sensitivity to contaminants. Evaluation of a highly
sensitive species can bring about de facto consideration and
protection of other species inhabiting the site. However, at a
site with a complex mixture of contaminants, the investigator
may be unable to identify one sensitive species that is most
appropriate for study.
• Ecological function, along with significance of a species'
contribution to this function. An investigator may select a
species for study based on its ecological function. For ex-
ample, at a site with contaminated surface water, the investi-
gator may choose to study algae as the aquatic community's
primary producers.9 The investigator may specifically fo-
cus on those algal species that make a large contribution to
this function.
• Time spent on-site. To qualify for further study, a species
should inhabit the site during either a considerable portion or
a critical stage of its life cycle.
• Ease or difficulty of conducting field studies with the organ-
isms. A field study that requires capturing birds is resource-
intensive, and unlikely to occur at a typical Superfund assess-
ment. Where fish-eating birds are at risk because
bioaccumulating substances have contaminated the surface
water or aquatic organisms, the investigator might choose
instead to focus primarily on the fish that the birds eat or to study
a mammal or reptile with feeding habits similar to the birds.
• Appropriateness of surrogate species. In the case of a site
with an endangered or threatened species, the investigator
may elect to study a surrogate species with similar exposure.
Surrogate species offer the advantage of sampling and analy-
sis options that cannot be employed with threatened or
endangered species. However, in selecting a surrogate spe-
cies, the investigator should identify one that resembles the
site species in behavior, feeding, and physiological response
to the contaminants of concern. The best choice for a surro-
gate is not necessarily the one most closely related to the site
species.
• Other recognized values. At some sites the investigator may
want to consider a species because of other values associated
with it, such as economic or recreational value.
Based on the above considerations, the investigator generally
selects no more than a few species as subjects of the field study.
However, an investigator can choose to study a community. For
example, at a lake with contaminated water and sediment the
investigator can study the benthic community that lives in associa-
Although a large number of species
can inhabit a site, an ecological risk
assessment of a Superfund site con-
cerns itself only with those that are
actually or potentially adversely affected
by site contamination or that can serve
as surrogates for such species.
tion with the lake's bottom. When selecting a community as an
ecological component, the investigator needs to ascertain that the
study includes populations representing multiple trophic levels.10
At some Superfund sites, investigators have selected a wet-
land habitat as the ecological component for further study. Such a
choice can prove more protective of the environment since the
investigator can document a variety of adverse effects on the
7 Bioavailability is the occurrence of a contaminant in a form that
organisms can take up.
"The term "investigator" refers to the individual charged with
responsibility for designing and/or carrying out any part of an ecological
risk assessment. Investigators can include government scientists, contrac-
tors, or university scientists. However, the site manager (remedial project
manager or on-scene coordinator) retains ultimate responsibility for the
quality of the ecological risk assessment.
' A primary producer is an organism, such as an alga or a terrestrial
plant, that converts the energy from sunlight to chemical energy.
10 A trophic level is a stage in the flow of food from one population
to another. For example, as primary producers, plants occupy the first
trophic level, and grazing organisms occupy the second trophic level.
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habitat rather than having to demonstrate significant impact to only
one or a few species. Studying a habitat becomes especially
important when one or more of the remedies under consideration
could adversely affect the habitat. However, designating a habitat
as the ecological component can prove costly, depending upon
how the ecological risk assessment delineates the habitat.
To extend these general guidelines for selecting ecological
components, the following sections consider different kinds of
organisms that inhabit either aquatic or terrestrial environments
and detail how each can increase an investigator's knowledge of
the ecological conditions at the site.
Aquatic Organisms
At a site where contaminated surface water is a medium of
concern, field studies can focus on periphyton, plankton, benthic
macroinvertebrates, or fish. Periphyton are microscopic algae
that grow on sediment, stems and leaves of rooted water vegeta-
tion, and other surfaces that project above the bottom of a body of
water. Studying periphyton provides information about primary
producers in an aquatic environment. These organisms also in-
clude many species useful in assessing the cause, extent, and
magnitude of contaminant problems.
Plankton are microscopic organisms that float or swim
weakly in the water column. Plankton include algae, protozoa, and
small crustaceans. Planktonic algae are called phytoplankton,
and the protozoa and crustaceans in plankton are referred to as
zooplankton. Because plankton include primary producers, which
supply food for larger animals and also increase the amount of
oxygen dissolved in water, these organisms make an important
contribution to the aquatic community. Like periphyton, plankton
include species that are sensitive indicators of ecological injury
resulting from contamination or enrichment of water bodies.
As defined by EPA, benthic macroinvertebrates are inver-
tebrate animals that live in or near the bottom of a body of water and
that will not pass through a U.S. Standard No. 30 sieve, which has
0.595 mm openings. Such organisms occur in gravel, sediments,
on submerged logs and debris, on pilings and pipes, and even on
filamentous algae. Freshwater benthic macroinvertebrates include
insects, worms, freshwater clams, snails, and crustaceans. The
benthic macroinvertebrate communities of marine and estuarine
environments include worms, clams, mussels, scallops, oysters,
snails, crustaceans, sea anemones, sponges, starfish, sea urchins,
sand dollars, and sea cucumbers. When water becomes contami-
nated, some of the contaminants migrate to the sediment and
accumulate there. Field studies of benthic macroinvertebrates can
indicate the degree to which sediment contamination can ad-
versely affect biota. In addition, the composition and diversity of
benthic macroinvertebrate communities can indicate the overall
well-being of the aquatic ecosystem.
Because fish occupy a range of trophic levels, they serve as
useful indicators of community-level effects. The relative ease of
identifying most juvenile and adult forms makes fish particularly
convenient subjects for field study. In addition, field study meth-
ods for fish are relatively simple and inexpensive. In selecting a
species for sampling, the investigator will want to consider its
characteristic home range. For a species that spends little time on-
site, a field study may not be able to establish whether any adverse
effects result from exposure to site-associated contaminants.
Semi-aquatic and Terrestrial Animals
Semi-aquatic and terrestrial animals—includinginsects, other
invertebrates, and vertebrates—can all provide useful information
about ecological effects associated with the site. Soil fauna, the
organisms most intimately associated with this medium, include
many species that perform important functions in terrestrial eco-
systems. For example, earthworms aerate the soil. Other soil-
dwellers—such as some small insects, soil mites, and certain
nematodes (a kind of worm), break down organic wastes and dead
organisms—releasing the elements and compounds they contain
and making these available to living organisms. Both soil aeration
and organic decomposition support the growth of terrestrial plants.
Consequently, plants can suffer impact if soil fauna are affected.
Insects' small size and their large numbers make them conve-
nient subjects of study. Further, a site generally has a large number
of species. Because these species occupy a variety of microhabitats
and also differ in their behaviors, the investigator can measure a
range of effects. For example, because insects include species at
different trophic levels, a field study can assess the potential for
biomagnification" of a site's contaminants.
Field studies focusing on such vertebrates as amphibians,
reptiles, and mammals can contribute to a site's ecological assess-
ment. Depending on their trophic level, these vertebrates may
ingest contaminants as a result of consuming contaminated plants,
other terrestrial animals, or fish. Burrowing animals, such as voles,
can show greater ecological effects from contaminated soil than
animals that have less intimate contact with the soil. Where
investigators at Superfund sites decide to study terrestrial verte-
brates, they generally choose small species, which are likely to
range over a smaller area than larger species. As a result, the
smaller species tend to spend more of their time on the site, making
it easier to estimate exposure.
Field studies of birds present certain difficulties at a
Superfund site. These organisms can range far off-site, making
it difficult for a field study to establish whether an adverse
ecological effect results from exposure to site-associated con-
taminants. In addition, bird studies can prove especially resource-
intensive. However, at a large site or a site with a complicated
contaminant picture, the investigator and the BTAG may decide
that avian field studies are worth the effort. For example, many
sites have large populations of waterfowl that can potentially
suffer adverse effects from site contaminants.
Terrestrial Vegetation
When a site has contaminants associated with the soil, field
study can focus on terrestrial vegetation. In particular, investiga-
tors may want to conduct field studies of vegetation at Superfund
sites where plants show signs of stress, such as stunted growth or
yellowing, or where pollution-tolerant species are abundant. Since
plants are the primary producers in terrestrial environments, an
ecological impact to vegetation can affect other terrestrial biota.
11 Biomagnification is the increasing concentration of a
bioaccumulating contaminant as it passes up a food chain or a food web.
A food chain is a series of organisms that sequentially feed on one another.
For example, mice eat seeds and are in turn eaten by owls. A food web,
which is a group of interrelated food chains, takes into account a species'
participation in multiple food chains. For example, birds, insects, and
other mammals also eat seeds, and cats, as well as owls, prey on mice.
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Elements in the Design
of a Field Study
As with any study, an ecological field study has several
elements. In addition to selection of the organisms, the elements of
a field study encompass the study's objectives, a reference site,
endpoints, methods, level of effort, sample design, quality assur-
ance/quality control standards, and the statistical analysis of the
data. When the investigator carefully crafts each of these elements,
the resulting study should achieve its objectives and should further
the overall ecological risk assessment of the Superfund site.
Under-developing any of these elements can weaken the study's
results and adversely affect the results of the overall assessment.
Objectives
To ensure that the study will have clear direction, the inves-
tigator needs to establish study objectives that address ecological
concerns for that site. The objectives should ensure that the field
study supports the over-all objectives of an ecological risk assess-
ment for a Superfund site. These objectives are (1) to determine
whether site contamination poses a current or potential threat of
adverse ecological effects; (2) if a threat does exist, to decide
whether remediation is required; and (3) if remediation is required,
to set cleanup levels.
Investigators will find that study objectives help to indicate
the appropriate level of effort. In an initial field study to identify
ecological components, for instance, an investigator might find
that a qualitative survey method would achieve the study's objec-
tive. The later study of adverse effects to a population might
require a more resource-intensive approach, such as semi-quanti-
tative or quantitative sampling to estimate population sizes or
capture of organisms and transport to a laboratory for biochemical
analysis.
Although the specific objectives for a field study will vary
both with the site and its stage in the ecological risk assessment
process, investigators should keep in mind that a field study
performed as part of a Superfund site's ecological risk assessment
is not a research project. Generally, a snapshot of site characteris-
tics can provide the needed information.
In addition to stating the purpose of a field study, the objec-
tives also should indicate whether the field study is occurring in
conjunction with another type of study, such as a toxicity assess-
ment. In such a case, the two studies have a shared goal: to
determine whether adverse ecological effects correlate with toxic-
ity. To meet this goal, the studies' objectives should emphasize the
need for integrating sampling plans and coordinating the collec-
tion of data. When sampling for coordinated studies occurs at the
same time and location, and with similar data quality objectives
and levels of precision, the investigator can more convincingly
compare results.
Reference Site
A reference site is a location that closely resembles the
Superfund site in terrain, hydrologic regime, soil types, vegetation,
and wildlife. A well-chosen reference site provides background
conditions, allowing the investigator to draw conclusions about the
ecological effects of contaminants on the Superfund site. The more
closely the reference site resembles the Superfund site, the more
valid will be the conclusions based on comparisons of the two. In
some cases, no single reference site adequately approximates the
Superfund site. In such a case, the investigator may need to identify
multiple reference sites.
The investigator should try to locate a reference site as close
as possible to the Superfund site so that it will accurately reflect the
conditions prevailing at the Superfund site. Yet the reference site
should lie at a great enough distance from the Superfund site to be
outside its sphere of influence and relatively contaminant-free. For
example, an upstream location often can provide appropriate
reference site conditions for a site with contaminated surface
water. A woodland site used as a reference site needs to lie at agreat
A field study performed as part of
a Superfund site's ecological risk
assessment is not a research project.
enough distance from the Superfund site that ranges of organisms
will not include both sites.Failure to choose appropriate reference
sites can result in inaccurate conclusions. For example, if the
surface water at the Superfund site consists largely of soft-bot-
tomed pools, then an area having fast-running streams with gravel
bottoms will not provide an appropriate comparison. Differences
in species composition and other features at the two sites will, at
least in part, reflect their very different aquatic habitats rather than
contamination at the Superfund site.
In the absence of suitable reference sites, an investigator may
need to turn to historical information about the site and/or a large
database in order to make a comparison between site conditions
and conditions in an uncontaminated area. If this approach be-
comes necessary, the investigator needs to choose a data source
that reflects the site's geologic, hydrologic, and ecological traits as
closely as possible. In making this selection, the investigator can
obtain advice and suggestions from the BTAG.
Endpoints
The identification of endpoints, which are ecological charac-
teristics that may be adversely affected by site contaminants, is
essential to a successful ecological risk assessment as a whole and
also to each of the studies that make up this assessment. Ecological
risk assessors have found it useful to recognize two levels of
endpoints, assessment and measurement endpoints. An assess-
ment endpoint is an explicit expression of the environmental
characteristic that is to be protected (24, 29).12 At a Superfund site
an assessment endpoint is an endpoint that may drive remedial
decision making. Determining potential contaminants of concern
and potential ecological components and developing a conceptual
model of a site's contaminant situation generally indicates which
ecological traits are assessment endpoints at a particular site.
12 Numbers in parentheses refer to references listed at the end of the
Bulletin.
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If an assessment endpoint is not directly measurable, investi-
gators employ one or more measurement endpoints—readily
measurable traits that approximate or represent the assessment
endpoint. Together, the ecological components and assessment
endpoints selected for the risk assessment determine the selection
of the measurement endpoint(s). (See Figure 1.) For example, at a
site where metals are the contaminants of concern and species are
present that may be adversely affected by metals, the investigators
may identify "population-level effects on resident species" as an
assessment endpoint and one or more metals-sensitive species as
ecological components. The choice of measurement endpoints
then points to accepted ways of measuring or predicting population
responses in resident species that are known (or at least suspected)
to be sensitive to metals.
Figure 1. The Relationship Between
Ecological Components,
Assessment Endpoints, and
Measurement Endpoints
In designing a field study, the ecological
components and assessment endpoints
generally drive the selection of measure-
ment endpoints.
Ecological
Component
Measurement
Endpoint
Assessment
Endpoint
Table 2 summarizes measurement endpoints for field studies.
Although a field study can focus on one population, an entire
community, or even two or three communities, as both Table 2 and
the following discussion indicate, measurement endpoints for field
studies are much more than simply "head counts."
Biomass, the total weight of individuals, can be a measure-
ment endpoint for both populations and communities. An investi-
gator may measure biomass directly by weighing collections of
small organisms or, for larger organisms, by weighing individuals
and summing their weights. Alternatively, he or she may use an
indirect method, such as applying length-to-weight regressions to
data detailing the number and length of individuals in a population,
an especially common approach for fishes.
Productivity, the rate of increase, is another measurement
endpoint that can apply to both populations and communities. For
plants, the rate of increase in biomass indicates productivity. For
many animals, investigators take the rate of increase in numbers as
the measure of productivity. Because productivity is a rate, mea-
surements or estimates must occur at least twice during the
growing season. However, investigators can infer productivity by
conducting seed or egg counts or by studying the age structure of
a population. At Superfund sites, investigators can infer relative
productivity by comparing data from the Superfund site and the
reference site(s).
A common measurement endpoint for terrestrial plant popu-
lations is cover, which is the percentage of ground area that lies
beneath the canopy (uppermost branches) of a tree or shrub
species. In evaluating a stand of trees, an investigator can instead
measure basal area, which is the sum of the cross-sectional area
of the trees' trunks.
Some measurement endpoints relate specifically to commu-
nity parameters. Species richness is the number of species in a
community. Species density refers to the number of individuals of
a given species per unit area, while relative abundance is the
number of individuals in a particular species compared to the total
number of individuals. Dominance, in the sense of commonness
at a site, describes a species that occurs in high abundance, as
indicated largely by species density. Diversity relates the abun-
dance of individuals in one taxon (level of classification) to the
total abundance of individuals in all other taxa. Evenness mea-
sures how evenly distributed individuals are among thecommunity's
taxa. Guild structure, which refers to the different types of
feeding groups in a community, also can be used to evaluate
community structure.13 A number of similarity and difference
indices14 can compare community structure at Superfund and
reference sites.
Another community-level measurement endpoint concerns
indicator species, which are species whose presence, absence, or
population density helps to indicate whether the environment is
contaminated. Some species are associated with thriving commu-
nities, so either absence or a reduced population can indicate an
ecologically disturbed environment. For example, the larval stage
of insects in the orders Ephemeroptera (mayflies), Plecoptera
(stoneflies), and Trichoptera (caddisflies), referred to collectively
as the "EPTs," show sensitivity to metals and other inorganic
contaminants. Reduced populations of EPTs, then, can indicate
toxic levels of metals or other inorganics in a stream. Conversely,
some species occur in association with a disturbed habitat, where
they dominate or kill native species weakened by exposure to
contaminants. For example, such plant species as Phragmites and
cattails (Typha) characteristically grow abundantly in disturbed
wetlands. Consequently, dense growth of Phragmites or cattails
indicates that a wetland may have suffered ecological stress.
13 Guilds, also called functional feeding groups, are groups of
animals occupying the same trophic level and feeding either in the same
way or in the same location. For example, among terrestrial plant-eaters
there are five guilds: stem-eaters, root-eaters, leaf-eaters, bud-eaters, and
nectar-sippers.
" An index is a single number that incorporates information from a
class of data.
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Methods
Field studies gather information about the site by observing
organisms, noting signs of an animal species' presence, or collect-
ing organisms for further study. With respect to methods, the work
plan for a site should include detailed instructions for sampling
organisms and collecting the relevant data. This data may include
such physical measurements as the temperature. .; sampling site.
Proper methodology ensures that the data collected can be ana-
lyzed and results interpreted.
Observation indicates whether a species occurs at the site. For
vegetation and for animals with limited mobility, the observer also
can note the condition of the organisms. Investigators need to keep
in mind that for more mobile animals, observation indicates only
whether the species occurs at the site, not what percentage of time
it spends there. Observing organisms can be as straightforward as
walking the site or can involve the use of specialized equipment,
as in remote sensing of terrestrial vegetation. Remote sensing by
such means as infrared or multispectral photography can prove an
effective way of detecting stressed vegetation at a large site.
The signs of an animal's presence include scat (feces);
burrows, nests, or dens; cast-off larval cases or cocoons; tracks;
and carcasses. Characteristic sounds, such as bird songs, also can
reveal an animal's presence and sometimes provide limited infor-
mation about relative abundance. Like direct observation of resi-
dent organisms, observation of animal sign indicates only whether
a species occurs at the site, not the percentage of time it spends
there.
Methods of collecting samples for further study vary with the
kind of organism being studied. A field worker can catch a fish in a
net, capture a mouse in a trap, or sieve organisms from a soil or
sediment sample. Depending on the species and objectives, once the
investigator has collected the organisms, he or she may make direct
observations and then release them. Alternatively, the investigator
may retain the organisms for further study, such as analyzing tissues
for their contaminant content or examining them microscopically
for indications of contaminant-related abnormalities.
From among the wide variety of available field methods,
those used at a Superfund site should provide data at a reasonable
cost and within a reasonable timeframe for that site. They should
be readily reproducible, reliable, and relevant to the site. The
BTAG can assist investigators in selecting methods appropriate to
a site. In choosing a method, investigators also need to be aware
that they should obtain permission from federal and state fish and
wildlife agencies before collecting vertebrates. Some states also
require permits for collecting certain other organisms.
At sites in the nation's temperate areas, investigators need to
coordinate site studies with seasons. Floristics surveys and photo-
synthetic measurements must be conducted during the growing
season. Surveying a migratory population, such as most bird
species, will require coordination with the season. In addition,
natality studies should occur during the warm months, when most
animal species produce young.
The final section of this Bulletin provides additional informa-
tion about techniques available for field studies of different types
of populations and communities.
Level of Effort
A site's characteristics, its contaminant picture, and a pro-
posed field study's objectives together indicate the level of effort
appropriate to carrying out the study. For example, an objective to
identify potentially affected animal species at a small site with few
habitats will require a lower level of effort than one that specifies
the evaluation of community structure at a large site with several
habitats. The number and nature of ecological components and
endpoints specified by the objectives also may affect a study's
level of effort. As the number of ecological components and/or
assessment and measurement endpoints increases, the level of
effort generally will increase. Additionally, some organisms are
more difficult to observe or sample than others, and some measure-
ments are more difficult to make. For example, collecting insects
usually entails less effort than collecting fish.
Type
Measurement Endpoints
for Populations
Table 2. Measurement Endpoints in Field Studies
Measurement Endpoint
Biomass
Productivity
Cover (terrestrial vegetation)
Basal area (terrestrial vegetation)
Measurement
Endpoints for Communities
Biomass
Productivity and Respiration
(aquatic communities)
Species richness
Species density
Relative abundance
Dominance
Diversity
Evenness
Similarity/difference between Superfund site and reference site
Similarity/difference in guild structure between Superfund site and reference site
Presence, absence, or population density of indicator species
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In conducting field studies, the level of effort varies with the
sampling method chosen: qualitative, semi-quantitative, or quan-
titative (17). Qualitative sampling, which has as its goal to observe
or sample as many taxa as possible in the available time, requires
the least effort. Qualitative sampling attempts to sample all habi-
tats, using several collection methods at each sampling station.
Such an approach can prove useful for a site reconnaissance visit,
with the objective of identifying potentially exposed ecological
components and readily apparent effects.
Rapid Bioassessment Protocol II is an example of a semi-
quantitative, or intermediate-level, sampling method for benthic
macroinvertebrates inhabiting flowing waters (21). This approach
offers a time-saving and cost-effective means of obtaining infor-
mation about benthic macroinvertebrates. In this approach, the
field team uses a net to collect organisms from two approximately
one-square-meter areas, one in a fast-flowing part of the stream
and the other in a slower-flowing area. The organisms are then
enumerated and classified only to family level, which requires less
time than classification to genus or species. A sub-sample of 100
organisms is then classified according to guild. An additional
sample is collected from an area with coarse particulate organic
matter, such as a leafpack or an area near the shore. The organisms
in this sample are classified simply as shredders or non-shredders.
Quantitative sampling uses methods that sample a unit area or
volume of habitat. Generally, these methods are applied to ran-
domly selected sampling units. As with semi-quantitative sam-
pling, the organisms collected are counted and classified.
In deciding on level of effort, investigators should be aware
that limited sampling efforts can provide enough data for an
adequate ecological risk assessment of a Superfund site. It is true
that differences in life cycle characteristics and diurnal effects do
prevent limited sampling from providing a comprehensive esti-
mate of all species. However, if field studies at the site sample
enough biota, these kinds of variations will have minimal effect on
the overall assessment.
Sampling Plan
A sampling plan for a field study indicates the number of
sampling points, the number of replicates for each sampling point,
the method for determining sampling locations, holding times for
samples, and any sample preparation required for laboratory
analysis. In making these decisions for an ecological field study,
the investigator needs to consider the study objectives, the level of
effort, the site's size, the ecological component(s), the measure-
ment endpoint, the method, the statistical method of analyzing
data, and the available resources. For example, the approach to
statistical analysis will affect sampling size. If the field study is one
of a group of coordinated studies, then the investigator also needs
to consider whether a particular sampling method can apply to all
the studies in the group.
In general, sampling locations can be selected either non-
randomly or randomly. Qualitative and semi-quantitative surveys
make use of non-random sampling, taking into account the habitat
and mobility of the organisms and the location of contaminant "hot
spots." For quantitative sampling, investigators generally use
random sampling methods.
When the investigator has decided on the number of sam-
pling locations and the method of selecting them, he or she must
also decide how many replicate samples to collect per site. Both the
study objectives and the data quality objectives (discussed below)
influence this decision. While natural variability makes replicate
sampling desirable, for some field studies the sampling plan
cannot specify a fixed number of replicates. For example, field
biologists have no control over trapping success.
Quality Assurance/Quality Control (QA/QC)
Standards
Quality assurance and quality control standards are an essen-
tial element in the study plan. Included among the QA/QC consid-
erations are the data quality objectives (DQOs). These are
statements that define the level of uncertainty that the investigator
is willing to accept in environmental data used to support a
remedial decision. DQOs address the purpose and use of the data,
the resource constraints on data collection, and any calculations
based on the data. In particular, DQOs help investigators to decide
how many samples and replicates to collect in order to limit
uncertainty to an acceptable level.
DQOs also guide decisions about the level of detail necessary
for the study. For example, in field studies involving certain groups
of organisms, such as insects, DQOs establish the level to which
the investigation should take the identification of organisms.
Identification to the level of family or genus requires less expertise
and time than identification to the level of species. However, the
DQOs may require identification to the species level to obtain
detailed enough information about the site's ecological condition.
In addition to defining acceptable uncertainty, QA/QC stan-
dards address other concerns:
• Reference sites. As discussed earlier, the investigator should
achieve a careful match between the Superfund site and one
or more reference sites.
• Accurate identification of organisms. The investigator must
identify organisms accurately. A common means of ensuring
the accuracy of identification involves having the classifica-
tion of a subset of organisms verified by independent experts.
• Adherence to sampling plan. Field biologists must adhere
closely to the sampling plan in order to collect valid data.
Consequently, the study's design will need to incorporate
methods for checking how precisely personnel have followed
the sampling plan. For example, QA/QC standards may
require field biologists to maintain field notebooks and sub-
mit copies of these. Chain of custody documents provide
another means of tracking sample collection, transfer, and
analysis.
• Contractor. The contractor selected must have personnel
with the expertise needed to perform the particular type of
field study and interpret the data. In addition, the contractor
must have the necessary equipment and personnel skilled in
its use and maintenance.
Statistical Analysis of Field Data
In performingstatisticalanalysesof field data from Superfund
sites, two issues require special consideration: lack of randomness
and use of indices.
Lack of Randomness. Neither the Superfund site nor the
reference site is selected randomly. As a result of this lack of
randomness, the investigator must use one of the following ap-
-------
preaches in statistically analyzing differences between the
Superfund site and the reference site:
• The investigator selects sampling stations randomly at both
the Superfund site and the reference site(s), and then tests the
hypothesis that observed differences between these stations
result from conditions at the stations in the Superfund site.
• The investigator tests the hypothesis that the reference site(s)
and the Superfund site differ. If such a difference exists, the
investigator then employs nonstatistical methods to evaluate
whether contamination at the Superfund site causes this
difference.
Use of Indices. A field study can generate a volume of data too
large to be analyzed efficiently. In such a case, reducing classes of
data to a single number, called an index, simplifies the analysis.
Some of the community traits discussed earlier, including even-
ness and diversity, are examples of indices calculated from taxo-
nomic data. Indices also include biotic indices, which examine the
environmental tolerances or requirements of particular species or
groups of species.
While indices can make field data more manageable, inves-
tigators need to appreciate that indices have properties that can
preclude standard statistical comparison of results among sam-
pling locations (9). If an ecological risk assessment makes use of
indices, the discussion of uncertainty needs to address the limita-
tions of the indices and acknowledge the assumptions that they
make.
Field Methods
The following list includes a brief description, by type of
organism, of field methods useful in ecological risk assessments at
Superfund sites. Some methods focus on ways to collect on.- -
isms, while others concern ways to examine them.
These methods represent only a selection of those avaikn.-le.
In designing a field study, the investigator should consult the
BTAG, which may suggest approaches not described here. Please
note also that this catalogue includes only methods used in study-
ing biota. For methodology relating to the study of physical and
chemical characteristics of a site, investigators should consult the
following EPA documents:
• Sampler's Guide to the Contract Laboratory Program. EPA/
540/P-90/006, December 1990.
• Compendium of ERTSurface Water and Sediment Sampling
Procedures. EPA/540/P-91/005, January 1991.
• Compendium of ERT Soil Sampling and Surface Geophysics
Procedures. EPA/540/P-91/006, January 1991.
• Compendium of ERT Groundwater Sampling Procedures.
EPA/540/P-91/007, January 1991.
• Compendium of ERT Waste Sampling Procedures. EPA/540/
P-91/008, January 1991.
Periphyton
Scraping, coring, or suction. Field studies of periphyton can
involve collecting these organisms from their natural environment
by means of devices that scrape, core, or use suction (78, 30).
Artificial substrate. Materials such as granite, tile, plastic,
and glass can serve as an artificial substrate on which periphyton
communities can develop (78, 30).
DalaAnalysis. Investigators can study the taxonomic compo-
sition, biomass, species richness, and relative abundance of per-
iphyton communities from either natural habitats or artificial
substrates. In addition, analysis of data can yield information about
diversity, evenness, and similarity (78, 30).
Plankton
Trapping, pumping, netting, and using closing samplers.
Samples can be collected from natural substrates by means of
traps, pumps, nets, and closing samplers such as tubes and bottles
(3, 18, 30).
Data analysis. After identifying the organisms in the sample,
investigators can determine species richness, relative abundance,
and diversity (78).
Benthic Macroinvertebrates
Dredging and digging. Dredging and digging provide quali-
tative samples from the natural environment (77, 78).
Stream netting, coring, or sampling with a grab. Stream
netting, coring and sampling with a grab collect quantitative
samples from the natural environment. Stream netting involves
using specialized nets to collect samples. The Surber and the Hess
are stream nets commonly used to sample macroinvertebrates in or
on substrate. Some types of stream nets collect macroinvertebrates
drifting in the water column (a normal occurrence with benthic
macroinvertebrates inhabiting flowing water). A grab is a sam-
pling device with jaws that penetrate and extract an area of the
substrate (7, 4, 12,17, 18, 21).
Sweep netting. Sweep nets collect qualitative samples associ-
ated with aquatic vegetation (17, 78).
Sampling with other devices. More quantitative methods of
sampling benthic macroinvertebrates associated with aquatic veg-
etation involve using either the Wilding stovepipe or the Macan,
the Minto, or the McCauley samplers (77, 78, 27).
Artificial substrate. Communities of benthic macro-
invertebrates can develop on artificial substrates introduced into
the site's surface water (77, 78, 27).
Data analysis. Once the sample has been collected, the
investigator can identify the species present and measure biomass.
Further analysis of data can disclose such parameters as species
richness, species density, diversity, and relative abundance (77,
78, 27).
Fish
Seining. Seines are effective sampling devices for shallow
waters such as streams, nearshore areas of lakes, and shallow
marine and estuarine locations. The most commonly used seine
consists of a specialized net attached to long vertical poles (4, 21,
30).
Trawling. In deeper waters that have no obstructions, inves-
tigators use a tapered conical fishing net called a trawl. Aboat pulls
the trawl through the water at a specified depth (78, 27, 30).
Passive netting. For passive netting, the field biologist at-
taches a net to the bottom of a river or lake. Fish that swim into the
net become entangled or unable to escape. Passive nets include gill,
trammel, and hoop nets (20,18, 21, 30).
Electrofishing. This technique, which applies an electrical
charge to a small area in a body of water, momentarily immobilizes
-------
fish. Electrofishing is effective forsampling fish in streams, rivers,
and lakes (18, 21, 30).
Chemical collection. This specialized technique involves
exposing the animals to fish toxicants (27). Investigators should
familiarize themselves with state regulations regarding the use of
these substances. While use of such chemicals is a standard
procedure, this method is not preferred because of its negative
effects.
Fish tissue collection. Methods for collecting fish tissue are
described in References 25, 27, and 28.
Data analysis. Once the investigator has identified the fish, he
or she can determine such measurement endpoints as relative
abundance and species richness (18, 21, 30).
Terrestrial Vegetation
The methods described for terrestrial vegetation work equally
well for upland and wetland areas. This is true even though in
wetlands, by definition, the prevailing vegetation is typically
adapted to saturated soil conditions.
Remote sensing. Remote sensing, which uses either satellite
imagery or aerial photography, is useful when contamination of a
site has resulted in restricted access or when initial site reconnais-
sance requires surveys of large areas. The technique provides
information about general landscape patterns, gross features of the
vegetation, and photosynthetic rates. Infrared and multispectral
remote sensing also can be used to identify and map areas of
stressed vegetation (13). Usually, some limited ground-level sur-
vey (ground-truthing) is required to verify identification of species
and condition.
Quadrats and transects. Quadrats and transects are often used
in vegetation survey and sampling methods to provide a more
quantitative approach to collecting data. Quadrats are closed sam-
pling units or plots. Transects consist of belts, strips, or lines used
as a sampling unit. Both methods define precise, isolated areas for
sampling, recording, mapping, or studying organisms within a
larger area. Both methods allow investigators to estimate character-
istics such as cover, species frequency, and density (2,10).
Point method. The point method estimates cover using sam-
pling points (2, 10).
Distance methods. Distance methods provide a means of
estimating coverage and species density in forests, which would
require large quadrats to sample trees adequately. There are
several different versions of distance methods but in general the
methods are based on measuring distances between random points
and the sampled plants, or between individual plants (2, 10).
Soil Fauna
Coring. Field biologists collect samples by coring devices
(23).
Driving organisms from soil sample. Heat, moisture, or
chemical stimuli drive the organisms from the soil into collection
chambers (23).
Sieving. Sieving can be used to retrieve the fauna from the
soil. Dry sieving separates soil fauna from fallen leaves and friable
soil. Wet sieving, also called soil washing, is used to extract
organisms from fine mud, sediments, and leaf litter (23).
Density separation. Flotation, centrifugation, and sedimenta-
tion separate organisms from soil on the basis of density (23).
Data analysis. After the investigator has identified the organ-
isms, he or she can determine parameters that characterize the
community.
Terrestrial and Flying Insects
Trapping. Traps can be used to collect insects of particular
species, groups of species, insects at specific life stages, or insects
with specific behaviors. Trapping methods include the use of
all ractant chemicals, light, hosts, host substitutes, and insect sounds.
Traps include emergence, pitfall, and sticky traps, to name a few
(23). The type of trap used affects both the range of species
collected and the types of data collected. When collecting several
kinds of insects, the investigator can determine such measurement
endpoints as species diversity (23).
Sign. Frass (feces), nests, cast-off larval cases or cocoons, and
auditory signals indicate the presence of particular insects (23).
Amphibians, Reptiles, and Mammals
Auditory and visual study. Visual studies can determine the
presence of species on a site. In addition, sounds can indicate the
presence of certain amphibians and mammals. (19, 22).
Sign. Tracks, nests, burrows, dens, scat, or carcasses indicate
which species occur on a site (79, 22).
Trapping. Traps and nets can provide more quantitative means
of sampling and, depending on the breadth of the study, allow an
investigator to determine population and/or community parameters
relative to the reference site. Trapping methods include both live
traps and kill traps. Depending on the study objectives, the investi-
gator either makes observations on live-trapped animals and re-
leases them or retains the animals for further study (5, 6, 7,19).
Tissue collection. Methods for collecting tissues are de-
scribed in Reference 26.
Birds
A uditory and visual studies. Ornithologists identify the species
at a site by walking specified areas or distances (e.g., along a
transect) and record birds sighted or identified through their songs (5).
Nest success. The evaluation of nest success on the basis of
measures such as clutch size and number of fledglings is practical
only for very large Superfund sites (7).
Trapping. Not practical for most Superfund sites, a variety of
traps and nets can be used to capture birds (6).
Field Studies: Their Contribution
As the previous sections of this Bulletin indicate, field studies
can contribute to all phases of the ecological risk assessment of a
Superfund site and in a variety of ways. Specifically, a well
designed field study can allow investigators to:
• Identify and describe the habitats and species (including
those of special concern) actually or potentially exposed to
waste site contaminants.
• Indicate detrimental ecological effects that may have oc-
curred on or near the site.
• Provide information adding to the weight of evidence linking
adverse effects to the site's contaminants.
• Provide samples for biomarker studies, such as
10
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bioaccumulation studies, biochemical analyses, and
histopathological studies.15
• Aid in identifying remedial alternatives that are protective of
natural resources.
• Assist in monitoring remediation effectiveness.
Investigators should consult with their Region's BTAG to
determine whether and when to conduct field studies and to select
the studies most appropriate to their sites.
References
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2. Barbour, M.G., J.H. Burk and W.D. Pitts. 1980. Terrestrial
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3. Bloesch, J. (Editor). 1988. Mesocosm Studies.Hydrobiologia
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4. Coull, B. C. 1980. Shallow Water Marine Biological Re-
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5. Davis, D.E. and R.L. Winstead. 1980. Estimating the Num-
bersof Wildlife Populations. Pages221-245 in S.D.Schemnitz
(Editor). Wildlife Management Techniques Manual. Fourth
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6. Day, G.I., S.D. Schemnitz and R.D. Taber. 1980. Capturing
and Marking Wild Animals. Pages 61-88 in S.D. Schemnitz
(Editor). Wildlife Management Techniques Manual. Fourth
Edition. The Wildlife Society, Washington, DC.
7. Downing, R.L. 1980. Vital Statistics of Animal Populations.
Pages 247-267 in S.D. Schemnitz (Editor). Wildlife Manage-
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8. Escherich, P. and D. Rosenberger. 1987. Guidance on Use of
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9. Greig-Smith, P. 1983. Quantitative Plant Ecology. Third
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10. Green, R.H. 1979. Sampling Design and Statistical Methods
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NY.
11. Hair,J.D. 1980. Measurement of Ecological Diversity. Pages
269-275 in S.D. Schemnitz (Editor). Wildlife Management
Techniques Manual. Fourth Edition. The Wildlife Society,
Washington, DC.
"A biomarker is a physiological, biochemical, or histologies!
response that is measured in individual organisms and that indicates either
exposure or sub-lethal stress.
12. Hess, A.D. 1941. New Limnological Sampling Equipment.
Limnol. Soc.Amer. Spec. Publ. 6:1-5.
13. Kapustka, L.A. 1989. Vegetation Assessment. Section 8.3 in
Warren-Hicks, W., B.R. Parkhurst, and S.S. Baker Jr. (Edi-
tors). Ecological Assessment of Hazardous Waste Sites: A
FieldandLaboratoryReference. EPA/600/3-89/013. Environ-
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14. Karr, J.R. 1981. Assessment of Biotic Integrity Using Fish
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15. Karr, J.R., K.D. Fausch, P.L. Angermeier, P.R. Yant, and I.J.
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17. Klemm. D.J.,P.A. Lewis, F. Fulk,and J.M. Lazorchak. 1990.
Macroinvertebrate Field and Laboratory Methodsfor Evalu-
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Quality Assurance, U.S. Environmental Protection Agency,
Cincinnati, OH.
18. LaPoint, T.W. and J.F. Fairchild. 1989. Aquatic Surveys.
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20. Nielsen, L.A. and D.L. Johnson (Editors). 1983. Fishing
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R.M. Hughes. 1989. Rapid Bioassessment Protocols for Use
in Streams and Rivers: BenthicMacroinvertebrates and Fish.
EPA/600/4-89-001. Assessment and Watershed Protection
Division, Office of Water, U.S. Environmental Protection
Agency, Washington, D.C.
22. Smith, R.L. 1966. Ecology and Field Biology. Harper and
Row, New York, NY.
23. Southwood,T.R.E. \91&. Ecological Methods: WithParticu-
lar Reference to the Study of Insect Populations. Second
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24. Suter, G. 1989. Ecological Endpoints. Chapter 2 in Warren-
Hicks, W., B.R. Parkhurst, and S.S. Baker Jr. (Editors).
Ecological Assessment of Hazardous Waste Sites: A Field
11
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and Laboratory Reference. EPA/600/3-89/013. Environ-
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25. U.S. Environmental Protection Agency. 1981. Interim Meth-
ods for the Sampling and Analysis of Priority Pollutants in
Sediments and Fish Tissue. EPA/600/4-81/055. Environ-
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26. U.S. Environmental Protection Agency. 1982. Test Methods
for Evaluating Solid Waste: PhisycallChemical Methods.
SW-A46.2nd edition. Office of Solid Waste and Emergency
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Additional Print Resources
Available from the Federal
Government
Adamus, P.R. et al. 1991. Wetland Evaluation Technique. Vol.
1: Literature Review and Evaluational Rationale. Technical
Report WRP-DE-2. U.S. Army Corps of Engineers.
Baker, B. and M. Kravitz. 1992. Sediment Classification Meth-
ods Compendium. EPA/823/R-92/006. U.S. EPA Office of
Water.
Beyer, W.N. 1990. Evaluating Soil Contamination. Biological
Report 90(2). U.S. Department of Interior.
Fletcher, J. and H. Ratsch. l99Q.Plant Tier Testing: A Workshop
to Evaluate Nontarget Plant Testing in Subdivision J Pesti-
cide Guidelines. EPA/600/9-91/041.
Linder, G. et al. 1992. Evaluation of Terrestrial Indicators for
Use in Ecological Assessments at Hazardous Waste Sites.
EPA/600/R-92/183. Office of Research and Development,
ERL-Corvallis, OR.
U.S. Environmental Protection Agency. 1988. Guidance for
Conducting Remedial Investigations and Feasibility Studies
under CERCLA. EPA/540/G-89/004.
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