United States Science Advisory Board EPA-SAB-EPEC-94-007
Environmental 1400 January 1994
Protection Agency Washington, DC
AN SAB REPORT:
EVALUATION OF A
TESTING MANUAL FOR
DREDGED MATERIAL
PROPOSED FOR
DISCHARGE IN INLAND
AND NEAR COASTAL
WATERS
PREPARED BY THE SEDIMENT
QUALITY SUBCOMMITTEE OF
THE ECOLOGICAL PROCESSES
AND EFFECTS COMMITTEE
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EPA-SAB-EPEC-94-007
February 1, 1994
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401M Street, S.W.
Washington, DC 20460
Subject: Review of the Draft Testing Manual for Dredged Material Proposed for
Discharge in Inland and Near Coastal Waters
Dear Ms. Browner:
On July 7-8, 1993, the Sediment Quality Subcommittee of the Ecological Processes and
Effects Committee met to review the Agency's draft document, Evaluation of Dredged Material
Proposed for Discharge in Inland and Near Coastal Waters: Testing Manual. The testing
manual provides test methods for evaluating the potential ecological and human health impacts of
contaminants in dredged material proposed for discharge under section 404 of the Clean Water
Act. At the request of the Office of Water, we reviewed the manual to determine whether it
provides an appropriate testing framework, and in particular, to evaluate: 1) the chemical and
physical analyses; 2) the types of bioassays and species selected for toxicity and bioaccumulation
tests; 3) the scope of the Tier IV (case-specific) studies; 4) the statistical methods used to
compare dredged material to reference sediment; and 5) the use of the mixing zone model
(STFATE) in a variety of shallow-water conditions.
In 1991, the Science Advisory Board reviewed the companion testing manual for
evaluating dredged material proposed for disposal in ocean waters. We were pleased to see that
many of the recommendations of that review have been addressed in the testing manual for inland
and near coastal waters. Overall, the proposed test methods in the manual are validated and
appropriate for use at this time. Although we have recommended a number of specific changes to
the test procedures, the primary focus of our report is on issues which are not well addressed in
the draft manual. Several of our broader recommendations are relevant to the Agency's overall
approach to contaminated sediments. Our principle recommendations are as follows:
a) The assessment of risks from discharge of dredged material in inland and near
coastal waters should be conducted in accordance with the Agency's Framework
for Ecological Risk Assessment, considering the full range of risks (including those
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from resuspension of pathogenic microorganisms in dredged material) and the risks
associated with alternative disposal options.
b) The toxicity of dredged material should be determined relative to known clean
sediments, rather than relative to reference sediments which may themselves be
causing contaminant-related impacts.
c) The manual should include plant bioassays to be conducted in conjunction with
animal tests in cases where the dredged material discharge site will be vegetated
(e.g. beneficial uses of dredged material for creation of wetlands, submerged
aquatic vegetation beds, and beach renourishment).
d) The development and implementation of a continuous release model for dredged
material discharge, to supplement the instantaneous discharge model (STFATE),
should be accelerated and included in the final manual.
e) Guidance on sampling design, field collection of samples, and statistical analysis of
data should be expanded.
We appreciate the opportunity to review this important document, and we hope that our
recommendations will be helpful to the Agency and the U.S. Army Corps of Engineers in
implementing section 404 of the Clean Water Act. The Sediment Quality Subcommittee has
reviewed a number of scientific issues and methodologies over the past years which are the
stepping stones to the development of sediment quality criteria and an overall contaminated
sediment strategy. We encourage the Agency to continue this interaction with the Board as
subsequent sediment technical documents are developed.
Sincerely,
/signed/
Dr. Genevieve M. Matanoski, Chair
Executive Committee
/signed/
Dr. Kenneth L. Dickson, Chair
Ecological Processes and
Effects Committee
/signed/
Dr. Robert J. Huggett, Chair
Sediment Quality Subcommittee
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U.S. Environmental Protection Agency
NOTICE
This report has been written as part of the activities of the Science Advisory Board, a
public advisory group providing extramural scientific information and advice to the Administrator
and other officials of the Environmental Protection Agency. The Board is structured to provide
balanced, expert assessment of scientific matters related to problems facing the Agency. This
report has not been reviewed for approval by the Agency and, hence, the contents of this report
do not necessarily represent the views and policies of the Environmental Protection Agency, nor
of other agencies in the Executive Branch of the Federal government, nor does mention of trade
names or commercial products constitute a recommendation for use.
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ABSTRACT
On July 7-8, 1993, the Sediment Quality Subcommittee of the Ecological Processes and
Effects Committee met to review the draft document, Evaluation of Dredged Material Proposed
for Discharge in Inland and Near Coastal Waters: Testing Manual., to determine whether it
provides an appropriate testing framework to evaluate potential ecological and human health
impacts of proposed discharges of dredged material under section 404 of the Clean Water Act.
Overall, the Subcommittee concluded that the tests were validated and appropriate for use at this
time. However, the Subcommittee questioned the premise of comparing contaminant-related
risks from dredged material to those from reference material which might itself be causing adverse
biological effects. Rather, the Subcommittee recommended that the toxicity of dredged material
be determined relative to known clean sediments. The Subcommittee felt that the assessment of
risks from discharge of dredged material in inland and near coastal waters should be conducted in
accordance with the Agency's Framework for Ecological Risk Assessment, considering the full
range of risks (including those from resuspension of pathogenic microorganisms in dredged
material) and risks associated with alternative disposal options. In assessing risks to human health
from bioaccumulating substances, the Subcommittee agreed that FDA action levels are the
appropriate benchmarks for comparison, as long as the tests are made on edible portions of food
organisms; bioaccumulation factors (BAFs) determined in amphipods or aquatic insects are not
appropriate for such a comparison. The panel also recommended that plant bioassays be
conducted in conjunction with animal tests in cases where the dredged material discharge site will
be vegetated (e.g., beneficial uses of dredged material for creation of wetlands, submerged aquatic
vegetation beds, and beach nourishment).
KEYWORDS: dredged material, ecological risk assessment, bioaccumulation, toxicity
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U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
ECOLOGICAL PROCESSES AND EFFECTS COMMITTEE
SEDIMENT QUALITY SUBCOMMITTEE
July 7-8, 1993
ROSTER
CHAIR
Dr. Robert J. Huggett, Virginia Institute of Marine Science, College of William and Mary,
Gloucester Point, Virginia
MEMBERS/CONSULTANTS
Dr. David W. Engel (Federal Liaison), National Marine Fisheries Service, Beaufort Laboratory,
Beaufort, North Carolina
Dr. John Gallagher, Halophyte Biology Laboratory, University of Delaware, Lewes, Delaware
Dr. Rolf Hartung, School of Public Health, University of Michigan, Ann Arbor, Michigan
Dr. Bjorn Kjerfve (Invited Expert), Baruch Institute, University of South Carolina, Columbia,
South Carolina
Dr. Frederic K. Pfaender, Institute of Environmental Studies, University of North Carolina,
Chapel Hill, North Carolina
Dr. Judith Weis, Department of Biological Sciences, Rutgers University, Newark, New Jersey
SCIENCE ADVISORY BOARD STAFF
Ms. Stephanie Sanzone, Designated Federal Officer, Science Advisory Board, U.S.
Environmental Protection Agency, 401 M Street, SW (1400F), Washington, DC 20460
Mrs. Marcia K. Jolly, Staff Secretary, Science Advisory Board, U.S. Environmental Protection
Agency, 401 M Street, SW (1400F), Washington, DC 20460
m
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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY 1
2. INTRODUCTION 4
2.1 Background 4
2.2 Charge to the Subcommittee 4
3. GENERAL COMMENTS 5
3.1 Test Methods 5
3.2 Comparison to Reference Sediment 5
3.3 Risk Assessment vs. Risk Management 6
3.4 Protection of Human Health 6
3.4.1 Bioaccumulation 7
3.4.2 Microbiological Concerns 8
4. BIOASSAY PROCEDURES AND TEST SPECIES 9
4.1 Need for Plant Bioassays 9
4.2 Bioassay Test Conditions 9
4.3 Test Sediments 10
4.4 Sampling Indigenous Infauna 10
5. TIER IV SUBLETHAL CHRONIC TESTS 12
6. USE OF THE STFATE MIXING ZONE MODEL 12
7. FIELD DATA COLLECTION AND STATISTICAL METHODS 13
8. TECHNICAL CORRECTIONS 14
9. REFERENCES CITED 16
IV
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1. EXECUTIVE SUMMARY
The Sediment Quality Subcommittee of the Ecological Processes and Effects Committee
has reviewed the draft document, Evaluation of Dredged Material Proposed for Discharge in
Inland and Near Coastal Waters: Testing Manual (May 1993), to determine whether it provides
an appropriate testing framework to evaluate potential ecological and human health impacts of
proposed discharges of dredged material under section 404 of the Clean Water Act. Overall, the
proposed test methods in the manual are validated and appropriate for use at this time. However,
since this is a rapidly advancing field, we encourage both EPA and the U.S. Army Corps of
Engineers to maintain active research programs to identify, develop, validate and apply new
approaches for assessing environmental and human health risks related to disposal of dredged
material. Our comments and recommendations are summarized as follows:
a) We recommend that the toxicity of dredged material be determined relative
to known clean sediments. The manual currently requires that the determination
of contaminant-related impacts be based on statistical comparisons between tests
with proposed dredged material and reference sediment. However, the criteria for
selection of reference sites are vague and subjective. If the chosen reference site
sediments contain contaminants that elicit the same level of effects as those in the
dredged material, then discharge could be approved even if significant mortality of
test organisms occurred in both. We disagree with the underlying assumption that
discharge of toxic dredged material at already-contaminated sites will not cause
additional degradation, since: 1) natural deposition may remove in-place
contamination from the biologically active zone if the source of contamination is
removed, and 2) the substance(s) causing the adverse biological effects in the
dredged material may have a different degradation half-life than those in the
reference sediments.
b) The manual should incorporate elements of EPA's Framework for Ecological
Risk Assessment and relate the test procedures in the manual to the overall
assessment of risks associated with various disposal options, including
discharge into coastal and inland waters.
c) The manual should address the full range of risks from discharge of dredged
material into coastal and inland waters, including those related to pathogenic
microorganisms. Currently, the manual focuses primarily on risks from chemical
contaminants that bioaccumulate and would, therefore, be transmitted to humans
through consumption of food exposed at the site. However, the 28-day
"bioavailability" test in the manual has several limitations: 1) one cannot assume
that an equilibrium has been reached after 28 days, especially in the case of
macromolecules, and 2) results of bioavailability tests must be evaluated in
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conjunction with information on the extent of uptake and storage of a contaminant
in the organisms.
The manual does not adequately address the most likely human health risk from
discharge of dredged material in inland and near-shore environments, namely the
resuspension of pathogenic microorganisms which have accumulated in sediments,
e.g., near sewage treatment plant outfalls. The testing manual should include
greater detail on the analytical methods available for assessing the extent of
microbial contamination, their strengths and weaknesses, and appropriate uses.
d) Where plants may become part of the ecosystem developing on the deposited
dredged material, plant bioassays should be conducted in conjunction with
animal tests. Although the manual specifically states that the tests apply to
dredged material to be used for beneficial uses, most of which (wetlands,
submerged aquatic vegetation beds, and beaches) will be vegetated, no plant
toxicity tests are required. Animals, no matter how carefully chosen, cannot serve
as surrogates for plants. For example, responses to herbicides, sulfides, pH,
sediment texture and fertility cannot be evaluated across kingdoms.
e) We recommend a number of specific changes to test procedures in the
manual, for example: 1) elutriate for chemical analyses and toxicity testing should
be prepared using water which mimics the salinity and ionic composition of the
water at the proposed discharge site rather than the dredging site; and 2)
consideration should be given to conducting sediment bioassays on core segments
since homogenizing sediment samples may result in over or under-estimation of
ecological risks from contaminated sediment.
f) Sublethal chronic tests are very important in assessing sediment toxicity and
such assays should be incorporated into Tier III as soon as they have reached
an acceptable level of development. Another source of information on longer-
term contaminant related impacts is analysis of benthic community structure and
bioaccumulation in indigenous infauna at proposed dredging and reference sites.
g) The STFATE mixing zone model appears to be competently implemented
and useful for instantaneous discharges of dredged material, although the
manual should include greater detail on the model's limitations, intended
uses, and governing equations. However, since most estuarine and near-
shore dredging is by means of pipe dredges with continuous discharge
dredged material release, we recommend that development/implementation
of a continuous release model be accelerated and included in the final
manual.
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h) We recommend that guidance on sampling design, field collection and
statistical analysis of data be expanded in the final manual.
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2. INTRODUCTION
2.1 Background
Under section 404 of the Clean Water Act, the Environmental Protection Agency (EPA)
and the U.S. Army Corps of Engineers (COE) share responsibility for managing disposal of
dredged material. The COE regulates non-federal dredging and dredged material discharge
activities through a permit program, and conducts federal dredging and dredged material activities
through its Civil Works Program. EPA is responsible for developing guidelines for designating
dredged material disposal sites. The statute requires that these 404(b)(l) guidelines be
comparable to criteria established under the Marine Protection, Research and Sanctuaries Act
(MPRSA) for disposal of dredged material into ocean waters.
In 1991, the Science Advisory Board reviewed the Testing Manual for Evaluation of
Dredged Material Proposed for Ocean Disposal (Ocean Testing Manual), which addresses
dredged material disposal governed by section 103 of the MPRSA (EPA-SAB-EPEC-92-014).
Like the Ocean Testing Manual, the document titled Evaluation of Dredged Material Proposed
for Discharge in Inland and Near Coastal Waters: Testing Manual is intended to form the basis
for the assessment of contaminant-related environmental impacts from proposed discharge of
dredged material. Test results are evaluated along with consideration of physical impacts,
disposal alternatives, etc. prior to a final decision.
2.2 Charge to the Subcommittee
On July 7-8, 1993, the Sediment Quality Subcommittee of the Science Advisory Board's
Ecological Processes and Effects Committee met to review the draft document, Evaluation of
Dredged Material Proposed for Discharge in Inland and Near Coastal Waters: Testing Manual
(Inland Testing Manual). The Office of Science and Technology in the Office of Water requested
that the Subcommittee review the draft testing manual to determine whether it provides an
appropriate testing framework to evaluate potential ecological and human health impacts of
proposed discharges of dredged material under section 404 of the Clean Water Act, and, in
particular, to evaluate 1) the chemical and physical analyses; 2) the types of bioassays and species
selected for toxicity and bioaccumulation tests; 3) the scope of the Tier IV studies; 4) the
statistical methods used to compare dredged material to reference sediment; and 5) the use of the
mixing zone model (STF ATE) in a variety of shallow-water conditions.
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3. GENERAL COMMENTS
3.1 Test Methods
The Subcommittee commends the authors of the Inland Testing Manual in that many of
the recommendations made by the SAB on the Ocean Testing Manual have been addressed here.
For example, a major concern with the Ocean Testing Manual involved the selection of toxicity
test organisms and the tests themselves. With the exception of plant bioassays, which were not a
consideration for the Ocean Testing Manual, most of these concerns have been alleviated in this
draft of the Inland Testing Manual. The test methods in the manual are validated and appropriate
for use at this time. However, since this is a rapidly advancing field, we encourage both EPA and
the COE to maintain active research programs to identify, develop, validate and apply new
approaches for assessing environmental and human health risks related to disposal of dredged
material (e.g., cell culture bioassays, biomarkers, and molecular measures). Of particular
importance would be to take advantage of scientific developments occurring in other federal
agencies (U.S. Fish and Wildlife Service, U.S. Department of Agriculture, Air Force, etc.) and in
other countries, particularly Canada and Western Europe.
3.2 Comparison to Reference Sediment
The Inland Testing Manual describes a testing strategy wherein toxic effects of proposed
dredged material are compared to reference sediment and control sediment. Reference sediment
is defined in the manual as sediment obtained from the proposed disposal site (but outside the
footprint of any past disposal), and control sediment is characteristic of the test organisms'
collection site or laboratory-rearing environment. Survival of test organisms in the control is used
only to verify that the test procedures themselves are not resulting in unacceptable mortality, and
statistical comparisons are only done between tests with proposed dredged material and reference
sediment.
If the chosen reference site sediments contain contaminants that elicit the same level of
effects as those in the dredged material, then discharge could be approved even if significant
mortality of test organisms had occurred in both. This leads to the possibility that the limiting
factor(s) governing whether or not a dredged material is suitable for overboard disposal is not its
toxicity but rather the toxicities of the suite of potential reference sites. The Subcommittee
believes this to be inconsistent with optimum protection of coastal and inland waters since the
criteria for selection of reference sites are much too vague and subjective.
The underlying assumption that discharge of toxic dredged material at already-
contaminated sites will not cause additional degradation of the aquatic environment is often, if not
usually, false. One reason is that when in-place contaminated sediments are in depositional areas,
sedimentation will remove them from the biologically active zone if the source of contamination is
removed (e.g., as seen with Kepone contamination in the James River, Virginia). Discharge of
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contaminated materials on top of in-place contaminated sediments constitutes a continuation of
the pollution source and may result in additional degradation of coastal and inland waters.
Another concern is that there is usually no assurance that the substance(s) causing the adverse
biological effects in the dredged material are the same as those in the reference sediments. One
only knows that the biological responses were nearly the same. For example, if the contaminants
in the dredged material had a longer degradation half-life than those in the reference sediment,
then that discharge would constitute increased or additional degradation.
A more logical approach would be to consider the "control sediments", now used in the
testing protocol, the same way that reference site sediments are in the present document. In other
words, determine the toxicity of the dredged material relative to known clean sediments. This
information can then be considered, along with information on other potential dredging/disposal
impacts, in a risk management context.
3.3 Risk Assessment vs. Risk Management
The assessment of contaminant-related impacts from discharge of dredged material (e.g.,
determination of chemical content, dilution requirements, bioaccumulation potentials, toxicities,
etc.) is considered in the "Analysis" and "Risk Characterization" sections of the Agency's
Framework for Ecological Risk Assessment (EPA/630/R-92/001). However, the decision on
whether or not to dispose of contaminated sediments on or near other contaminated sediments is a
risk management decision. In this case, risk management includes consideration not only of the
relative toxi cities of the dredged material and sediment from the proposed disposal site, but also
whether or not it is prudent to dispose of a material in coastal or inland waters if it contains
hazardous materials in toxic amounts, and other available management options.
We recommend that the Inland Testing Manual incorporate elements of the Framework
for Ecological Risk Assessment, and relate the test procedures in the manual to the overall
assessment of risks associated with various disposal options, including discharge into coastal and
inland waters. It appears that most, if not all, of the analyses needed are already required; it is
only the thought process and data treatment and integration that differ.
3.4 Protection of Human Health
The Inland Testing Manual suggests that protection of human health from impacts
associated with discharge of dredged materials is a major goal. However, the manual addresses
human health risks mainly for chemical contaminants that bioaccumulate and would, therefore, be
transmitted to humans through consumption of food exposed at the disposal site. Several
concerns are not addressed by this approach:
a) The links between exposure offish and shellfish to dredged material, subsequent
bioaccumulation of chemicals in aquatic organisms, and transfer to humans in
amounts sufficient to cause adverse health effects are not clear.
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b) Exposure of human populations to chemical contaminants through direct water
contact, i.e., swimming and recreational use, is not addressed at all.
c) Health risks from exposure to pathogenic microorganisms resuspended by
dredging and discharge activities are not adequately addressed.
3.4.1 Bioaccumulation
The bioaccumulation of chemicals from sediments is of potential concern to the
accumulating organisms and to the consumers of such organisms. The Inland Testing Manual
relies heavily on a 28-day "bioavailability" test for the assessment of bioaccumulation.
Bioavailability is defined as the ability of a substance to be taken up by an organism. This
definition of bioavailability includes practically everything except very large macromolecules and
solids. Thus, the simple question of whether a substance is bioavailable is not very useful. It is
the extent of the uptake and storage that is important, and that requires estimates of equilibrium
concentrations in the bioaccumulating organism relative to the concentration of the chemical in
water, sediment and food materials. Alternatively, the extent of bioaccumulation can be estimated
from a knowledge of uptake rates, metabolism and excretion rates, and the storage compartments
in the organism. To discern whether an equilibrium has been attained requires repetitive sampling.
One cannot assume that an equilibrium has been reached after 28 days, especially in the case of
macromolecules and substances with a high octanol-water partitioning coefficient (Kow).
Furthermore, it is inherently difficult to determine whether an equilibrium has been
attained by inspection of bioaccumulation curves alone. Shallow slopes in a bioaccumulation
curve combined with variabilities in the data often lead to visual estimates that underestimate the
true equilibrium concentration. Even if accurate determinations of the equilibrium and
bioaccumulation coefficient have been made, these cannot account for any biomagnification in
higher trophic levels. The manual is correct in pointing out that the phenomenon of
biomagnification appears to be applicable only to a limited set of chemicals.
The major stated purpose in the manual for determining the degree of bioaccumulation of
chemicals in sediments is the protection of human health. The Food and Drug Administration
(FDA) action levels are the benchmarks against which the extent of bioaccumulation are
compared. This is appropriate, as long as the comparisons are made on edible portions of food
organisms. In other words, bioaccumulation factors (BAFs) in mussels, oysters or edible parts of
fish can be used in conjunction with FDA guidelines as part of a risk assessment process for the
protection of human health. BAFs determined in amphipods or aquatic insects are not appropriate
for such a procedure, although such BAFs are potentially useful for the development of exposure
guidelines for the protection of organisms that consume amphipods or aquatic insects.
Neither the use of excess cancer risk slope factors (which is often at variance with FDA
action levels) nor the "computerized risk and bioaccumulation system" expert system were
evaluated by the Subcommittee because insufficient detail was provided.
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3.4.2 Microbiological Concerns
The most likely human health risk, and, in some cases, perhaps the greatest overall adverse
effect from discharge of dredged material in inland and near-shore environments, is the
resuspension of pathogenic microorganisms which have accumulated in sediments, e.g., near
sewage treatment plant outfalls. Following resuspension during dredging and discharge, the
redeposition of these very small particles may be very slow, spread over a large area, and not be
well predicted by the mixing zone model designed for different purposes. Human exposure to
these pathogens can occur via the three pathways described in section 4.2.1 of the Inland Testing
Manual: 1) through consumption of contaminated seafood, 2) direct contact, and 3) through
contamination of drinking water supplies.
Although discharge of dredged material must be in compliance with state water quality
standards (i.e., standards must not be exceeded outside the mixing zone), we question whether
dredging operations routinely include any measurement of pathogens or indicator organisms. In
addition, current microbial water quality standards, especially the total coliform standard for
shellfish, are in dispute and widely acknowledged to not be protective for viral disease.
In section 4.2.1, the manual does include a brief discussion of microbiological concerns
related to dredging and discharge of sediments and provides literature references where more
detail can be found. However, while it may be beyond the scope of this manual to address all of
these issues comprehensively, the manual should include greater detail on the analytical methods
available for assessing the extent of microbial contamination, their strengths and weaknesses, and
appropriate uses.
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4. BIOASSAY PROCEDURES AND TEST SPECIES
4.1 Need for Plant Bioassays
In the Ocean Testing Manual, potential contaminant effects on plants were not considered
because the only plant communities exposed to the dredged material were the phytoplankton
communities during the time the dredged material dropped through the photic zone to the aphotic
sea bottom. In estuarine and inland settings, however, the photic zone frequently extends to the
bottom of the open water where benthic micro- and macroalgal communities develop. These
benthic micro-algae are often the source of much of the phytoplankton as they are suspended by
natural or human-induced turbulence. In addition, the Inland Testing Manual states in section 2.3
(page 23) that the tests apply to dredged materials to be used for beneficial uses, most of which
(wetlands, submerged aquatic vegetation~SAV~beds, and beaches), will be vegetated (both
angiosperm and algae). Wetlands obviously have angiosperm and algal bases to their food webs,
as do SAV beds. In human-assisted beach nourishment, the dredged material may end up in the
intertidal area where benthic micro flora grow on and between the sand grains. These organisms
play a stabilizing role as well as serving as a food source for invertebrates which in turn are eaten
by surf-zone fish and shore birds. Some of the deposited material is often used to form a primary
dune which is planted with beach grass, such as Amophila. The point is that plant communities
must be considered.
Animals, no matter how carefully chosen, cannot serve as surrogates for plants. For
example, responses to herbicides, sulfides, pH, sediment texture and fertility cannot be evaluated
across kingdoms. Where plants may become part of the ecosystem developing on the deposited
dredged material, plant bioassays should be conducted in conjunction with animal tests.
Candidate plant assays which could be incorporated in the manual would include tests involving
root elongation, seed germination, and chlorophyll content. Plant considerations should be
integrated throughout the manual in order that the user be aware of their primary importance in
new ecosystems developing on the deposited dredged material.
4.2 Bioassay Test Conditions
The proposed bioassay testing techniques for dredged material currently use standardized
EPA protocols. However, these protocols may not be representative of the salinity and
temperature conditions at the proposed disposal site. Salinity and temperature affect not only the
physiology of the test organism, but also can modify contaminant toxicity, bioavailability, and
reactivity (e.g., salinity may influence metal speciation and bioavailability). For these reasons, we
recommend that the water used in elutriate testing should mimic the salinity and ionic composition
of the water at the proposed discharge (vs. dredging) site. The manual should require that, in
addition to bioassays conducted using standard protocols, parallel bioassays be conducted under
conditions of salinity and temperature that are representative of the discharge site. Such
modifications of the testing procedure should give a more realistic estimate of sediment toxicity
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for specific disposal sites. Of course, care must be taken not to exceed the thermal or salinity
tolerances of the test organisms and we recommend that additional freshwater test species be
added to Tables 9 and 10 of the manual.
4.3 Test Sediments
The sediment bioassay procedures call for homogenizing the sediments prior to
introduction of test animals. In the normal benthic environment, the sediment profile is quite
important in that the macro-benthic organisms are exposed only to the top several centimeters of
sediments, and it is the toxicity of these sediments that is of greatest concern. While dredging and
discharge operations will tend to homogenize the sediments, upon discharge the dredged material
will settle at different rates. Lighter, smaller particles will settle out more slowly than heavier
particles, forming a surface layer of sediments which newly settling larvae will contact. Since
these smaller particles are more likely to have greater contamination, due to their greater surface
area per unit mass, the process of sediment homogenization prior to a bioassay will likely expose
test organisms to a less toxic environment than had the original sediment profile been retained.
Conversely, at reference sites where clean sediment has accumulated on top of contaminated
sediment, homogenization of reference sediment may result in greater toxicity to test organisms
than the undisturbed sediment.
Therefore, it may be appropriate to require that analyses (chemical and bioassay) be done
with the top two centimeters of sediment cores if they are fine grained (less than 63 microns)
since this is the material most likely to be mobilized in dredging/disposal operations. Since mixing
the sediment cores may result in an over or under estimation of ecological risks, consideration
should be given to conducting some tests on core segments, e.g., 0-2 cm, 8-10 cm, etc.
In any case, substrates which have been collected for toxicity testing from control,
reference and dredging sites need to be closely matched for those physical and chemical
characteristics that are required to support the growth and survival of the test organisms.
Otherwise, the tests are likely to measure deviations from basic growth requirements rather than
impacts of any contaminants in the sediments.
4.4 Sampling Indigenous Infauna
The diversity of the benthic community is a clear indication of the habitability of the
sediments at a given site. In locations that are not dredged too frequently, and where vessel
traffic is not too great, it may be possible to do benthic community analysis in order to supplement
information obtained from sediment bioassays. Identification of organisms sieved from the
sediments prior to sample processing would allow a first order assessment of community diversity
at the proposed dredging site relative to that at a reference site. In addition, organisms collected
from the dredging site could be analyzed for body burden of contaminants of concern to
supplement the bioaccumulation tests (for which various chemicals may not reach steady state by
28 days). This will give a truer indication of long term steady-state bioaccumulation.
10
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11
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5. TIER IV SUBLETHAL CHRONIC TESTS
Sublethal chronic tests are very important in assessing the toxicity of a sediment and such
assays should be incorporated into Tier III as soon as they have reached an acceptable degree of
development. Such tests include Necmthes growth, and reproduction in the amphipod
Leptocheirus. Development of sexual maturation in Mysids may also be a good test, despite the
epibenthic nature of these animals.
Tier IV guidelines are envisioned for the most complex situations. It is not possible to
write detailed directives for the investigation of such situations. However, it must be recognized
that environmental toxicological testing is open ended and there are always additional tests that
can be conducted that could provide useful data. Therefore, it is critical that there be a process
for negotiating which questions are of concern in each case.
6. USE OF THE STFATE MIXING ZONE MODEL
The Inland Testing Manual details the use of a numerical simulation model to determine
the "instantaneous discharges from barges or scows and sequential discharges from hopper
dredges." The model is the COE's STFATE (Short-Term Fate of Dredged Material Disposal in
Open Water Model). Since most estuarine and near-shore dredging is by means of pipe dredges
with continuous discharge dredged material release, we recommend that
development/implementation of a continuous release model be accelerated and included in the
final manual.
STFATE appears to be a competently implemented and useful instantaneous discharge
model. The STFATE program, which is provided on PC-based diskettes with the manual, is easy
to use. However, since the documents on which this model are based were not available in
advance of our review meeting, we have not attempted to review the technical aspects of the
model. Rather, our comments center on the way in which the model is presented in the
document.
In general, the description of STFATE, both in the body of the manual and in Appendix C,
should be more detailed. The model's limitations, intended uses, and governing equations should
be clearly stated in the manual. We recommend that the manual be revised to include the
following:
a) The STFATE model should be introduced as an instantaneous discharge model by
name in section 2.8.
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b) The basic conceptual approach of the STFATE model and its application to water
column testing should be included in section 10.1. This how-to-do section should
clearly specify the intended applications and inherent limitations of the model. For
example, the model is intended for short-term (1-2 hours) and shallow-water
(without vertical density stratification) applications.
c) Full theoretical and technical details of STFATE should be presented in Appendix
C, including governing equations, all model assumptions, some details of the
solution techniques, capabilities, limitations, and calibration and validation
procedures. The original published documentation of the model should be
referenced.
Once a continuous dredged material discharge model is completed, it should be presented
in a similar fashion, with PC-compatible diskettes supplied with the document. Note, however,
that for continuous discharge of dredged material into tidal waters, it will become necessary to
discuss and account for the oscillatory nature of the currents and the associated tidal dispersion.
This will not prove to be as simple as the application of the STFATE model.
7. FIELD DATA COLLECTION AND STATISTICAL METHODS
Field data collection is primarily discussed in Chapter 8, and statistical methods are
discussed in Appendix D. In addition, these topics are also referred to in many sections
throughout the document. We recommend that these sections be expanded. The document
should include practical advice on the design of sampling, how, where and when to collect the
field data, and how to analyze the data statistically. In the case of bottom sediment sampling, the
manual should specify how deep the sediment samples should be. The information should be very
specific, including the answers to what, how, when, and where to collect the data, advice on the
number of samples and replicates, a holistic discussion of the overall sampling design and strategy,
and guidance on data analysis following sampling. This would best be accomplished in Chapter 8.
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8. TECHNICAL CORRECTIONS
In addition to the comments provided in previous sections of this report, we would like to
note the following technical corrections which should be incorporated into the final Inland Testing
Manual:
a) The document currently contains a mixture of units, encompassing the SI, the cgs,
the MKS, and the English systems. In conformance with conventional and national
scientific standards, metric units should be used throughout the document and
equations that use English units should be reformulated. As the engineering
community still in part uses English units, it would be appropriate to specify the
English-unit equivalents within parentheses, in addition to metric units.
b) In several places in the document (pp. 107, 113, 122), estuarine salinity is referred
to as varying from 1 to 25 ppt and the near coastal salinity as exceeding 25 ppt.
We realize that the purpose of specifying salinity ranges is to suggest the range of
salinity tolerances of the various test species. However, the commonly accepted
salinity range for estuaries is 1-35 ppt and near coastal salinity is usually greater
than 30 ppt.
c) The title of Part III of the document is "Data Generation." Although numerical
modelers often refer to the output of simulation models as data, and thus modeling
as generation of data, this is confusing and a controversial practice. We
recommend that this title be changed and that Chapter 8 be retitled "Field
Sampling."
d) Footnote "b" of Table 9 (p. 107) should refer to Echinoderms as having pluteus
larvae—veliger larvae belong to mollusks.
e) Any reference to determining population or community effects from results of
single species bioassays should be deleted from the manual. For example, section
6.0 of the manual on Tier III Evaluation (p. 51) includes the statement, "laboratory
toxicity tests, as used in dredging assessments, are generally only intended to be
indicative of possible impacts to community structure, not to specific individual
species". The current state-of-the-science concerning the natural parameters that
control population and community structure does not usually allow extrapolation
from single species bioassays to population or community effects.
f) The definition of "biomagnification" given on p. 5 of the draft manual should be
amended to include the condition that organisms at higher trophic levels will have
higher body burdens than those at lower trophic levels.
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g) Page 65 of the manual includes the statement, "Contaminants have a greater
affinity for clay and silt than for sand." To ensure that sandy sediments are not
automatically excluded from sampling and testing, it would be helpful to include a
statement that, while contaminants may be present in lesser concentrations, they
may be more bioavailable from sandy sediments.
h) It should be noted in the section dealing with toxic equivalency factors (p. 89 of
the draft manual) that these factors have been derived for human health purposes,
and that for aquatic organisms the relative toxicities of different PCB congeners
and dioxins are likely to be quite different.
i) While it may be true that EPA has not published Agency-approved analytical
methods for analysis of saline water (as stated in 9.4.2 of the manual), widely
accepted methods for chemical analysis of estuarine and ocean waters do exist and
should be referenced in the testing manual (e.g., Strickland and Parsons, 1972;
Grasshoffetal., 1983)
j) The manual states that water column concentrations outside the mixing zone which
exceed 0.01 of the toxic (LC50 or EC50) concentration are deemed to be acutely
toxic to water column organisms. The origin of the 0.01 factor should be
explained (i.e., the factor originated as an "application factor" to relate acute to
chronic toxicity and was largely a matter of judgement).
k) The manual includes procedures for assessing ammonia toxicity in dredged
material (Appendix F of the manual). The toxicity of sulfides should receive
similar consideration.
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9. REFERENCES CITED
Grasshoff, K., M. Ehrhardt, and K. Kremling. 1983. Methods of
sea water analysis. 2nd, revised and extended edition. Verlag Chemie, Weinheim. 419p.
Strickland, J.D.H. and T. R. Parsons. 1972. A practical handbook
of sea water analysis. Bulletin of the Fisheries Research Board of Canada 122:1-172.
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