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WORKSHOP SUMMARI ES
Two consecutive workshops were held subsequent to the symposium on
contaminated marine sediments in order to discuss topics presented in
the invited papers. Work Group I, led by William Adams, directed its
discussion to current knowledge of the extent of contamination, methods
for classification of contamination, effects on biological communities
and human health, and mobilization and resuspension of contaminated
sediments. Work Group II, led by John Herbich, focused on the assess-
ment and selection of remedial technologies, economic considerations,
and the lessons learned from the featured case studies.
The discussions consisted of brief summaries by each speaker and
questions and comments by the committee and invited work group
participants. The syntheses below were based on summaries compiled by
the group leaders and rapporteurs~ Jack Anderson and Michael Palermo,
for Work Groups I and II, respectively. No attempt was made to
attribute specific comments to specific individuals.
~-r ~
WORK GROUP I
EXTENT, CLASSIFICATION, AND SIGNIFICANCE OF CONTAMINATION
Extent of Contamination
Work Group I began its discussion by addressing the question of the
extent of contaminated marine sediment and the actual number of sites
of concern. Papers presented by Christopher Zarba and Andrew Robertson
were the main focus of discussion. It is not known how many sites
contain sediment contaminants at concentrations that cause biological
damage. It is, however, the consensus that in areas with high human
populations, the potential is great that anthropogenic chemicals are
present at levels high enough to cause concern.
There has been only a modest effort expended to date to
systematically determine the areal extent of sediment contamination in
this country. Recently EPA has begun an effort to develop
methodologies to assess the biological impact of in-place sediment
contamination. Various EPA coastal regions as well as coastal states
are lending encouragement.
20
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EPA Storage and Retrieval System (STORET) data have been used to
develop a document entitled "National Perspective On Sediment Quality"
for EPA under contract by Battelle. This document attempts to provide
a list of contaminated sites and chemicals of interest and a first-cut
derivation of "threshold effect levels." However, no attempt has been
made to check the quality of the STORET data against primary literature
sources. This document does not provide a complete list of the many
chemicals that have been reported in sediments. In fact, workshop
participants believed that a listing of sediment chemicals and their
respective concentrations would not necessarily provide useful data,
because differing sample collection techniques and analytical protocols
used to obtain the data prevent comparison from site to site. It is
felt that most of the STORET and literature data on sediments are best
interpreted in a qualitative sense. The determination of contaminated
sites was also based on very limited data and the list should not be
considered complete. In an effort to encourage standardization, a
manual has been developed by the U.S. Army Corps of Engineers (COE) and
U.S. Environmental Protection Agency (EPA) describing a standardized
method of sediment collection and handling.
It was also pointed out that the frequency of sampling and
reporting values is specific for a given site and is not an indication
of how contaminated a site is in relation to other sites. Certain
coastal areas with low contamination have been monitored frequently.
Nevertheless, these data are important for providing a frame of
reference. The Battelle report concluded that "there are hundreds of
sites in the United States with in-place pollutants at concentration
levels that are of concern to environmental scientists and managers.
More than one-third (63 out of at least 184 sites) involve marine or
estuarine waterways." EPA has concluded that "some of the major sites
that have been identified that contain chemicals of interest at high
concentrations include Puget Sound waterways, Corpus Christi Harbor,
New York Harbor, Baltimore Harbor, Boston Harbor, New Bedford Harbor,
Black Rock Harbor, the California sewage outfalls at Palos Verdes and
parts of San Francisco Bay" (Zarba, page 45~.
The NOAA National Status and Trends Program currently provides the
most comprehensive and systematic national data set on sediments.
Chemical concentrations in marine sediments at approximately 200 sites
have been monitored since 1984. The program was set up to evaluate the
quality of the marine environment over time and systematically excluded
hot spots of contamination. Criteria to eliminate hot spot sites were
based on historical data and personal knowledge about specific sites.
The Status and Trends Program found that high levels of contaminants in
sediments occurred at virtually all of the sampling sites near Boston
and New York and at some of the sites near San Diego, Los Angeles, San
Francisco, and Seattle, as well in Choctawhatchee and St. Andrews bays
in Florida.
Workshop discussion also centered on what was an appropriate
definition of contaminated sediments. Many participants believed that
a generic definition was difficult to establish since it was necessary
to judge contamination on the basis of both chemical concentrations and
biological effects. Currently, it is not always possible to ascribe a
particular biological effect to a given chemical concentration. It was
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the belief of many workshop participants that a determination of
whether or not a given site is contaminated should be made on the basis
of appropriate biological tests. It is clear that the science as a
whole needs to be able to relate biological effects to chemical
concentrations if the state of the art of evaluating sediments for
extent and degree of contamination is going to be advanced.
EPA is in the process of establishing sediment quality criteria.
At this time, there are no apparent specific guidelines regarding use
of EPA's sediment quality criteria. A technical oversight committee
(of the Science Advisory Board) has been formed to address this issue.
Newly derived criteria for sediments have been used by the Superfund
office as a guideline to help determine when additional biological
testing is needed.
Contaminant hot spots will draw increased attention in the future,
both as a result of the Comprehensive Environmental Response, Compen-
sation, and Liability Act of 1980 and because of the need to dredge
navigational channels. Existing regulations cover the extent of
biological and chemical testing that must be conducted before dredged
material can be placed back into the marine environment. However,
there are also many highly contaminated areas that do not fall under
COE navigational authority. Comparable procedures to determine the
extent and significance of contamination in areas outside of
established navigation channels are needed.
The work group noted that whether or not a contaminated site
qualifies for Superfund designation may have little meaning relative to
the degree of contamination. Since 8 direct link to human health is
required for Superfund status, those sediments impacting only aquatic
biota do not currently qualify.
Classification of Contamination
A discussion of available methods for evaluating and classifying
contaminated sediments followed, focusing on papers presented by Robert
Barrick (pages 64-77), Edward Long (pages 78-99), Dominic Di Toro
(pages 100-114), and Richard Swartz (pages llS-129~. The speakers
discussed the Apparent Effects Threshold method, the Sediment Quality
Triad, the Equilibrium Partitioning approach, and the Sediment Bioassay
approach. Advantages and disadvantages of these approaches are listed
in Table 1, page 7.
The Sediment Quality Triad and Apparent Effects Threshold (AET) are
methods of evaluating and classifying the extent of contamination
associated with the sediments in a given geographical area. These
approaches incorporate data from chemical analyses, biological toxicity
tests of the sediments, and in situ measurements of ecological
diversity. The data can be used to
1. rank and classify the relative quality of sediments among sample
sites;
2. prioritize sites for remedial action and estimate the size of
the area to be remediated;
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3. provide a descriptive ecological evaluation of the study site
based on chemical, biological, and ecological data;
4. rank sediments based on each component and evaluate differences
between each of the descriptors;
5. compare the combined or individual data for each descriptor
against similar data collected from a reference site; and
6. establish numerical criteria for contaminants found in the study
area.
The strength of these two approaches is that they incorporate both
biological and chemical measures of contamination, the data are
extensive and little follow-up work is needed, they do not assume a
specific route of uptake by the organisms, and contaminant indices can
be calculated. The approaches appear to be particularly suited for
sites where remedial action is anticipated. Weaknesses include the
following:
need for a large data base and development of statistical
evaluations of the developed criteria;
results are strongly influenced by the presence of unknown
covarying toxic contaminants; and
a poor understanding of the bioavailability of the chemicals
present.
Furthermore, the cost of developing criteria can be quite significant.
The Equilibrium Partitioning approach uses existing water quality
criteria effects data, together with estimated concentration of a
specific contaminant in the sediment interstitial water, to determine
if the contaminant will be toxic to benthic invertebrates. This
approach is designed to provide data on specific chemicals of interest
and to provide numerical endpoint criteria that can be used as a
guideline for assessing the safety of chemicals in sediments. It is
based on the assumption that for nonpolar organics, ecological effects
are most often observed as a function of the concentration of the
chemical in the interstitial water. It also assumes that the
bioavailability of nonpolar organics is controlled by the amount of
organic carbon present in the sediment. Furthermore, it assumes that
interstitial water concentrations can be estimated by knowing the
organic carbon content of a specific sediment, the sediment bulk
concentration of a specific chemical, and the carbon normalized
sediment-water partition coefficient (KoC) for the chemical. This
approach is currently being evaluated by EPA for development of
sediment quality criteria.
Once water quality criteria have been established, or a chronic
test with one or more sensitive aquatic organisms has been performed, a
sediment quality value can be calculated. The only data needed to make
this calculation are the water quality criterion or chronic effect
level and the carbon normalized sediment-water partition coefficient
for the chemical of interest. The Equilibrium Partitioning method is
chemical specific, like the Water Quality Criteria values, and
addresses the issue of bioavailability. To date, laboratory data
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developed for approximately five chemicals provide empirical
confirmation of the Equilibrium Partitioning approach. The
disadvantages of this approach are as follows:
· it does not address the issue of complex mixtures and chemical
interactions;
· at the present time it is available only for nonionic organics;
· it uses partition coefficients, which can vary significantly;
· it is limited to only a few chemicals for which water quality
criteria values exist; and
· it does not incorporate toxicological data for the specific
sediments of interest.
The Equilibrium Partitioning approach assumes that the interstitial
water is the primary medium through which contaminants are taken up.
However, ingestion appears to be a very important uptake mechanism of
contaminants for many marine worms. Carbon normalization of the
sediment contaminant concentration and the organism contaminant
concentration (by using organism lipid content) has provided a useful
method for assessing the uptake of nonpolar organics. However, concern
was expressed about the effect of grain size and the degree of
hydrophobicity needed in order for this approach to be valid.
The Sediment Bioassay approach can be used in two ways to determine
sediment quality values. First, bioassays can be performed with the
contaminated sediments of interest, and effect levels can be compared
directly with the concentration of the chemical on the sediment.
Second, sediments can be spiked in the laboratory and dose-response
relationships can be developed. This approach is incorporated in the
AET and Sediment Quality Triad approaches and has the same main
advantage in that it actually tests the sediment and chemical of
interest with benthic organisms. When bioassays are applied to field
samples, they provide a measure of the cumulative effect of all the
chemicals present. It is thought to be an efficient method of
evaluating sediments. The method does not assume a specific route of
chemical uptake, and it follows the approaches used to develop water
quality criteria.
Limitations of this approach as with others that incorporate
bioassays are that bioassays do not always identify problem areas.
Sometimes a more sensitive species is needed to detect a problem.
Furthermore, chronic test methods are not well developed at this time.
Field-conducted bioassays do not lend themselves to development of
specific chemical criteria, and laboratory-spiked sediments often have
different sorption properties than aged field samples. Discussion of
sediment bioassays centered on their sensitivity and the need for
standardized tests and good storage and handling procedures for field
sediments. Infaunal field assessments are thought to be useful
measures of ecological effects, but may become costly if detailed
analysis is needed.
In summary, approaches that develop single numeric criteria often
do not provide sufficient data for assessing the overall significance
of contamination at a site. A number of approaches may be needed to
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evaluate the significance and extent of contamination at any given
site. The Equilibrium Partitioning approach may be a good screening
tool to determine if the concentrations of chemicals are approaching
known effect levels. If so, additional biological and chemical
testing, as well as in situ evaluations, may be needed. The consensus
of the group was that all the methods discussed were useful and that no
one method had a clear advantage. There is a need for method
development and standardization for sediment bioassays, as well as
long-term sensitive tests. Also, methods should be developed that
evaluate mutagenicity, histopathology, bioenergetics, and other
short-term indicators of chronic toxicity. A three-step site
assessment approach was suggested:
1. review criteria,
2. conduct laboratory bioassays, and
3. perform infaunal surveys.
Ultimately, the method used to determine sediment quality criteria
should be one that can be conducted routinely and cost-effectively.
Significance of Contamination
A discussion of effects of sediment contamination on biological
communities and human health was based on the papers presented by John
Scott (pages 132-154) and Donald Malins (pages 155-164~. The work
group focused on the use of population and community parameters in
sediment quality assessment and indicators of risks to human health.
Certain population and community parameters can be useful in
assessing sediment contamination. It is clear that succession occurs
in the marine environment in response to contaminant stress. Most
studies to date have centered on hard-bottom communities. As a result,
there is less information on soft-bottom community succession. Typical
succession patterns indicate a steady progression from colonizing to
steady-state communities following environmental perturbation. The
addition of contaminant stress on the sequence of community succession
does result in measurable effects. It is possible to detect population
and community responses, but the science has not evolved to the point
of being able to interpret these responses in relation to specific
chemicals. When changes occur, frequently the cause is not known.
More chemical-specific approaches for evaluating ecological impacts are
needed. There is a need to know, for instance, if observed effects are
primarily due to reduction of the food source, habitat modification, or
some other altered variable. The tools for evaluating community health
need to be improved and become predictive.
Detection of hot spots is usually not a problem. In order to
detect areas with moderate contamination and to understand its impact,
better understanding of chronic effects caused by specific chemicals or
mixtures is needed. This is most readily done in the laboratory.
Ecological succession as a result of contaminants might be viewed as a
series of chronic effects occurring in the field. A series of
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sensitive chronic laboratory tests would greatly advance understanding
of mechanisms of toxicity and increase predictive capabilities. -
Discussion by the work group centered on the need for sensitive
laboratory assays with endpoints other than the traditional endpoints
of growth and survival. There is a real need for short-term indicators
of chronic toxicity. Certain data suggest that measurement of effects
of chemicals on the immune response system might partially fulfill that
role. Development of a suite of responses that could be measured in
the laboratory and related to ecological effects was encouraged. There
are often significant differences between the organisms studied in the
laboratory and the organisms inhabiting the area of concern. This
points to the need for either the development of more test methods or a
better understanding of functional roles at the species level. For
example, what does the loss of a single species mean for the health of
the community? The answer is not easily obtained.
The COE is required to use ecologically relevant species in each
region designated to receive dredged materials. Since there are no
standardized sediment bioassays with ecologically relevant species for
all areas and types of contaminants present, the COE has used a variety
of methods--including the Equilibrium Partitioning method--in addition
to bioassay testing.
The extent of contaminant transfer from the marine environment to
humans is also poorly understood and underassessed. However, limited
studies suggest that "significant changes in health status may occur in
humans consuming contaminated fish" (Malins, page 161) . The most
revealing data sugges tiny that contaminated sediments might present
human health problems are residue levels in the tissue of organisms
consumed by the public. Food chain transport is the primary concern,
particularly for persistent and bioaccumulative chemicals like
chlorinated organics and methyl mercury. Particularly worrisome are
indications from PCB research that infants born to mothers that eat a
lot of fish from PCB-contaminated areas showed delays in developmental
maturation at birth, were smaller, had a reduced head circumference,
reduced neuromuscular maturity, and behavioral anomalies (Malins, page
159~. Risk assessment for tissue residue levels requires additional
study: for example, the significance of various levels of chlorinated
organics that can be measured in the human blood stream needs to be
understood. Typically, FDA action limits for a particular chemical in
fish or shellfish are not derived using risk assessment models in which
a protection level for a risk of one in a million is derived. If this
were done for PCBs, the action level would be much lower than the
existing one of 2.0 ppm. In fact, some researchers believe if this
approach were used for a wide variety of chemicals found in seafoods,
most of the U.S. nearshore commercial fisheries would have to be
closed.
The work group also raised the question of whether the public is
adequately protected and whether existing risk assessment models are
appropriate. Additional research is needed to determine if these risk
calculations are in fact real. Most risk assessments are currently
driven by the risk necessary to protect against cancer. This ignores a
host of other endpoints, such as reproductive effects, which may be
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more important than cancer effects. There was general consensus that
seafoods present a method of transfer of contaminants to humans, some
of which are obtained from the sediments. The extent of the risk that
is posed is not known. Emphasis should be placed on epidemiological
studies of populations living near contaminated sites, particularly
those with a history of consuming seafood from contaminated areas.
Resuspension of Sediments
Both the NRC Committee on Contaminated Marine Sediments and the
Society of Environmental Toxicology and Chemistry workshop on Priority
Research Needs on Risk Assessment (August 1987, Breckenridge, Colorado)
have targeted sediment resuspension and mobilization as a key research
need. Papers by Peter Sheng (pages 166-177) and Bruce Logan, Robert
Arnold, and Alex Steele (pages 178-198) on modeling of sediment
transport dynamics provided a focus for the work group discussion.
The work group agreed that cohesive sediment transport requires
more research. Many troublesome contaminants are associated with fine-
grained sediment particles. Because of the complexity of fine-grained
cohesive sediment transport, there are no validated, general models
available to describe it. Even practical rules of thumb are lacking in
some areas, although excellent studies have been done on various
elements of the transport problem, and both the COE and EPA are working
to develop useful models. At the outset, a reliable sediment mass-
balance should be constructed for each contaminated site, and--
ideally--field-validated models should be developed to describe
flocculation, biological aggregation, erosion, deposition,
resuspension, bioturbation, and advective diffusive transport.
Unfortunately, there are no data sets large enough to aid in this
task. Current models are based almost entirely on laboratory data and
have required extensive site-specific calibration, such as direct
measurements of resuspens ion rates .
Recent developments in instrumentation now make possible many of
the measurements needed to establish reliable models.. A suggested
approach was for EPA to sponsor a long-term research program at one of
the aquatic Superfund sites to derive the kinds of field data necessary
to build a useful model. A large portion of the data that would be
collected is necessary to meet existing EPA requirements. However,
collection of additional data also would be very useful.
Based on past experiences with deposition of PCBs in the Hudson
Rivers, DOT in the Palos Verdes Shelf, and kepone in the James River,
knowledge about long-term burial of persistent chemicals has been
gained. In each case, there have been areas where these chemicals have
become buried. However, reliable predictions of stability of deposited
materials under different and changing environmental conditions cannot
be made.
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WORK GROUP II
ASSESSMENT AND SELECTION OF REMEDIAL TECHNOLOGIES
The second work group, led by John Herbich, conducted a discussion
of remedial technologies that examined the state-of-the-art strategies
and technologies for control/treatment and disposal of contaminated
marine sediments, as well as economic considerations of remediation.
The discussion was based on papers presented by Michael Palermo et al.
(pages 200-220), M. John Cullinane et al. (pages 221-238), John Herbich
(pages 239-261), Robert Morton (pages 262-279), Ian Orchard (pages
280-290), and Thomas Grigalunas and James Opaluch (pages 291-310~.
Selection of Remedial Alternatives
At present, a range of control measures exists (both treatment and
containment technologies) that have potential or proven application to
dredging and disposal of contaminated sediments. During the symposium,
M. John Cullinane presented a procedure for selection of remedial
alternatives called the Dredged Material Alternative Selection Strategy
(DMASS). Many of the dredging and disposal technologies have been
derived from the hazardous waste field and have drawn heavily from the
Superfund program. Because of the variability of site and material
characteristics and the wide range of control/treatment technologies
available, no single technology will be the universal solution.
Furthermore, many factors in selection are not easily quantified. For
example, the potential need for a liner to protect groundwater
resources would be determined based on site-specific evaluation.
The nature of contaminated sediment must be considered carefully in
the selection of an appropriate control technology. In selecting such
a technology, sediments that contain some contaminants must be
distinguished from sediments that are highly contaminated and possibly
categorized as hazardous waste. While most hazardous waste disposal
problems deal with relatively small volumes of materials with high
concentrations of contaminants, problems with contaminated sediments
often involve large volumes of sediment with relatively low
concentrations of contaminants. For this reason, some technologies may
be technically ineffective or inefficient.
Since many of the control/treatment technologies are unproven,
extensive research and evaluation needs to be conducted for a range of
technologies. The research should focus on applicability to treat
large volumes of sediment, the degree of treatment or control achieved,
and costs.
A comprehensive management strategy for evaluation of alternatives
for disposal of dredged material was developed by the COE and presented
at the meeting by Michael Palermo (pages 200-220~. The COE considers
the strategy to be technically appropriate for dredged material,
providing the necessary level of environmental protection. The
strategy utilizes testing procedures specially developed for dredged
material that consider the geochemical environments of aquatic,
intertidal, or upland disposal areas. A decision-making framework has
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also been developed that allows comparison of test results with
applicable standards and criteria using a consistent approach. The
procedures in the strategy are consistent with regulatory requirements
under the Clean Water Act and Ocean Dumping Act (Marine Protection,
Research and Sanctuaries Act).
The COE's strategy was applied in several of the case studies
presented at the meeting, including the New Bedford and Commencement
Bay Superfund projects and Everett Homeport project. No problems with
application of the strategy and associated decision-making logic have
been reported. Most potential problems with applying the strategy have
involved selection of appropriate criteria or standards on which to
base decision making. In this respect, it is essential to involve all
concerned agencies and parties at every step of the process. The
formation of public involvement coordination groups, interagency
steering committees, or similar mechanisms for involvement are
desirable.
The COE's management strategy has been adopted by Environment
Canada in the evaluation of dredged material disposal alternatives for
the St. Lawrence Seaway and other projects. West Germany and the
Netherlands have also adopted the strategy. The strategy covers only
contaminant testing and controls. However, the COE has a broader
umbrella of evaluation procedures under its Long Term Management
Strategy initiative, which includes consideration of other aspects of
decision making, such as cost. No other comprehensive strategies for
evaluation and selection of remedial alternatives specific to
contaminated sediments were identified by the work group.
The work group agreed that no action should always be considered as
a potential alternative to remediation in an evaluation process
assuming that the fate of contaminants has been quantified. No action
may be preferable where natural detoxification of contaminants occurs
or where natural sedimentation processes help to isolate the
contaminated material from the environment. During an evaluation
process, the effects due to remediation should also be compared to
those associated with the no action alternative and consideration
should be given to the time required for natural processes to isolate
the contaminants. Special consideration of "no action" should be given
to cases in which remediation may cause irreparable harm to the
resource.
For both clean-up or no action alternatives, removal and control of
additional contamination sources is of critical importance. In the
Commencement Bay evaluation, selecting no action was considered viable
if natural recovery through biodegradation or natural capping by
sedimentation was predicted to occur within 10 years. The extent of
sediment disturbance by currents and bioturbation influences the time
required for permanent burial in cases of natural sedimentation.
In selecting the remedial alternative, the goal of remediation
should be carefully considered. Goals such as "nondegradationt' or
'ifishable/swimmable," which are goals for actual improvement of
conditions, can result in vastly different criteria. In some cases,
multiple criteria are being used in evaluations.
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Public involvement is essential to success in selection and
implementation of a remedial alternative. Citizen advisory groups and
public notices and meetings are accepted ways to ensure appropriate
public involvement. It is not always certain that all available
information will reach the public; therefore, the forum should be
well-established to disseminate and put all information into proper
perspective.
Developments in Equipment for Removal of Contaminated Sediments
A variety of equipment and operating procedures have been developed
to dredge contaminated sediments while minimizing sediment resuspension
and contaminant release. Conventional dredges, such as hopper,
clamshell, and cutterhead dredges, are applicable when large volumes of
material are to be removed to maintain navigation. However, these
dredges are not well-suited for removal of highly contaminated sediment
without modifications to the equipment or operating procedures.
Equipment such as enclosed clamshell buckets, auger suction heads,
matchbox heads, and other specialized dredge heads have been developed
by the Japanese and the Dutch. These specialty dredges, for the most
part, have been developed especially for removal of sediment with
minimum resuspension.
One problem with utilization of specialty dredges is the
availability of the equipment in the United States. Patent agreements
must be considered. Some of the dredging companies have a U.S.
representative or licensee, which would facilitate acquisition of the
equipment. Jones Act requirements may limit the use of equipment with
foreign-made floating plants. However, the use of a foreign-made
dredge head on a U.S.-made floating plant is not restricted. Use of
these heads on other plants could also eliminate present constraints
for operation of such equipment in shallow water areas.
There is a need for research and development in the area of
equipment for contaminated sediment remediation. There is presently no
such effort going on in the United States. Incentive for U.S.
companies has been lacking mainly because of a perceived limited market
for such equipment. Development by federal agencies, such as the COE
or EPA, also has potential drawbacks. Ownership of specialty dredges
by these agencies may be objected to by the dredging industry, and may
be restricted by law.
Available Disposal Alternatives
In considering the removal of contaminated sediments, the work
group identified a wide range of disposal alternatives. Disposal in
open water, including ocean disposal, may be a viable option if
appropriate control measures, such as capping, are implemented. Except
for prohibited substances, disposal in open water with appropriate
controls is compatible with regulatory requirements under the Clean
Water Act and Ocean Dumping Act and is accepted under the London
Dumping Convention.
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Containment alternatives, such as in-water confined disposal
facilities or upland disposal sites, involve proven technologies.
These sites can be constructed as simple containments or may
incorporate a wide range of control measures, such as chemical
treatment, filtration, solidification/stabilization, liners, and
covers.
More intensive alternatives involving various treatment or
destruction technologies may be effective for sediments with high
levels of contamination. However, they are normally expensive and
their application to large volumes of sediment--especially if not
highly contaminated--is not generally an economically favored
alternative.
The work group also considered the effectiveness of capping for
isolating contaminated sediments. Capping, covering contaminated
sediment with clean sediment, has been shown to be a viable disposal
alternative for contaminated dredged material in Long Island Sound and
New York Harbor. Monitoring has shown that contaminated material can
be placed in mounds and clean material placed over it to successfully
cap the mounds. Care in the placement procedure is essential for
success and may involve use of precision navigation, taut-wire buoys,
and rigorous inspection procedures. Most projects to date have
involved capping on level bottoms. Capping has been proposed for the
New Bedford pilot project and Commencement Bay and has been used in
Norwalk Harbor.
Research issues related to capping that need to be addressed
include capping procedures for deeper water sites and mass release
predictions. These research needs have become evident with the
proposed Everett Navy Homeport project and the pending designation of a
deep-water site for disposal of material from New York Harbor.
There are presently no mathematical models developed to evaluate or
design capping technology. However, to date there has been no evidence
of displacement of capped material by the capping process. Even with
material on the bottom in a mounded configuration, there has been no
evidence of material being squeezed out from under the cap. In
general, the geotechnical information related to capping is mainly
judgmental since the parameters involved are not known with certainty.
Monitoring also is of vital importance with capping projects. Advances
in monitoring equipment and techniques are as important as advances in
equipment for dredging and placing the material. However, monitoring
of capped sites should not be planned or required unless there is a
clear objective and the use of the monitoring data is clearly defined.
If designed and executed correctly, capping has low risk and is
generally a less expensive remedial alternative than confined disposal
facilities. However, capping is generally only feasible in low-energy
environments and where a source of capping material is available.
Capping within the boundaries of a channel area poses special problems
due to potential need for future deepening and vessel traffic and
anchoring. In general, deeper water sites offer low-energy
environments. However, potential dispersal of contaminated sediments
during placement in deep water is greater. Determining an acceptable
level of sediment contaminant dispersal is a major question.
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In New York Harbor, there are several large (4 to 20 million yd3)
borrow pits that were created during sand mining operations over the
past 40 years. The COE's New York District has completed a draft
environmental impact statement for use of these pits as containment
disposal sites for contaminated sediments. The dredged sediment would
be placed in the pits and capped with clean sand to both isolate and
contain the contaminated material and to restore the seafloor to its
original bathymetry and compos ition . The capped depos it would not have
surface relief. A major issue is the value of existing borrow pits in
concentrating fish populations, possibly making it desirable to leave
the old pits unfilled and constructing a new pit specifically for the
disposal site. This option may actually be less expensive than
conventional open-water disposal in the area and would probably be
reserved for questionable material or material that is unacceptable for
ocean disposal.
The fact that capping is considered a containment alternative and
not a treatment alternative may present some legal disadvantages from
the perspective of Superfund sites. The preference under the Superfund
Amendments and Reauthorization Act (SARA) for treatment-based permanent
solutions must be re-evaluated for cases of sediment contamination.
The relatively high volumes of material in most contaminated sediment
sites--as compared to most Superfund sites--dictates that the
containment option in many cases may be the best remedial alternative.
However, capping materials may themselves be modified, or perhaps with
the addition of carbon or other sorbent materials may be able to remove
contaminants. In such cases, capping could be defined as a treatment
alternative for these purposes.
Economic Considerations
A major consideration in implementing most of the desired
technologies is cost. Some remedial technologies, such as removal of
solids and associated contaminants through gravity settling, chemical
clarification, and filtration or solidification and stabilization of
sediment, are relatively inexpensive ($10 to $50 per yd3) and have
proven applicability to contaminated sediment disposal (this compares
to $1.67 per yd3 for navigational dredging of clean sediments). Other
more intensive technologies such as incineration or chemical extraction
are much more expensive ($200 to $750 per yd3) and have not been proven
in large-scale demonstrations. Some of the intensive technologies may
result in secondary pollution or a waste stream of a differing nature
that will also require treatment (e.g., air pollution problems related
to incineration). In such cases, pilot studies can be useful in
demonstrating applicability. Few detailed estimates of costs are
available. For the Commencement Bay Superfund site, an array of PCB
destruction technologies was examined with costs ranging from $200 to
$500 per yd3 of sediment treated. Cost information for the New Bedford
Superfund site should be available in the future.
The question of who will pay for remediation is another major con-
sideration. In the case of Superfund, responsible parties are liable
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for clean-up or remediation. Voluntary clean-up efforts by responsible
parties and out - of - court settlements are made in some cases . If
remedial action is pursued, EPA and the states ~ through the Superfund)
will bear costs for listed Superfund sites in which costs cannot be
recovered from responsible parties. For cases requiring remediation
not listed under Superfund, the question of who bears the costs
remains .
In general, remedial actions are costly and increasing levels of
remediation lead to rapidly increasing costs. The role of trade-offs
at and among sites must be considered, particularly given the scarcity
of funds to be used to clean up Superfund sites and the increasing
number of sites.
Both benefit-cost and cost-effectiveness analyses can assist in
making remedial action decisions at a site and in allocating efforts
among multiple sites (fund balancing). Benefit-cost analysis can put
the issues in perspective and is the only approach that can place
public and private investments at sites on the same economic footing as
investments in other environmental projects or other public projects in
general. However, to use benefit-cost analysis, an explicit value (or
range of values) must be assigned to human health and environmental
resources. Such valuation is difficult to do in many cases, it can be
controversial (particularly placing a value on mortality), and it may
be rendered more complicated by the potential liability of responsible
parties for damages under CERCLA.
Cost-effectiveness analysis avoids the need to value human health
and environmental goods explicitly. Instead, the general goal is to
select (1) the least-cost approach~es) to achieve a given objective or
(2) the actions that provide the greatest returns (e.g., number of
lives saved or illnesses avoided) for a given budget. However, to be
applied correctly, short- and long-term costs must be included, and
costs must be estimated consistently for alternative actions at a site
and among sites.
Cost-effectiveness is required under SARA; however, benefit-cost
analysis is not required in remedial action decisions nor is it widely
applied. Reasons for this might include the difficult nature of these
calculations in some cases, the reluctance to assign explicit economic
values to public health, legal considerations regarding the liability
for damages by potentially responsible parties, and the legal standing
of some economic analyses under the current legislation.
Also discussed was the potential role of strict liability for
damages in providing financial incentives for source control to avoid
creation of new sites. The natural resource damage assessment
regulations established under CERCLA and the Clean Water Act were
described and their scope and advantages outlined. Limitations of the
liability approach were mentioned, including the fact that it can only
be applied if the responsible party can be identified.
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International Joint Commission Areas of Concern
A number of the approaches described above are being considered by
the International Joint Commission (UC) for remediation of
contaminated sediment problem areas in the Great Lakes. Two major
options generally are considered feasible. A confined disposal
facility, built by diking nearshore areas of the lake, is considered a
proven technique. These facilities provide effective containment when
properly designed. Confined facilities built on upland sites are the
second major option. Other options, such as capping, strip mine
reclamation, and solidification, also have been evaluated by the IJC
and hold promise for specific projects.
The Canadians dispose of large quantities of contaminated sediments
each year. Technologies used in projects in the Netherlands and West
Germany are being evaluated for use in Canada. These technologies
involve use of hydrocyclones to separate contaminated fractions of
sediment for more efficient treatment.
Two projects in Canada have progressed to the implementation
stage. Hamilton Harbor, which involves clean-up of contaminated
sediment containing PCB and metals from an estuary basin, was scheduled
to start in summer 1988. For this project, solidification was
unnecessary and would require more storage areas for disposal. The
disposal at Hamilton will be in a conventional confined disposal
facility. A second project at Port Hope, involving approximately
25,000 yd3 of sediment contaminated with metals and uranium, will
involve reclamation of the uranium and treatment.
In the United States, a site at Wauke~an Harbor will involve
dredging and upland disposal Of 50,000 yd , including a hot spot of
5,000 to 10,000 yd3. A site at Ashtabula will involve disposal of
20,000 yd3 at a permitted hazardous waste site, and incineration of
5,000 yd3 of hot spot material.
CASE STUDIES
Case studies were presented during the symposium for New Bedford
Harbor, the Hudson River, the James River, and Commencement Bay.
Considerable effort was made in each of these studies to acquire good
data on the extent and degree of contamination. In most cases, the
extent of contamination was better defined than its potential
transport.
For all the case studies, three main options were considered:
1. complete removal of all contaminated sediment,
2. removal of limited volumes or hotshots, and
3. no action.
Disposal and treatment of the removed material involved consideration
of a wide range of alternatives. The selection of an alternative was
dependent on three main factors:
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1. public acceptance (the NIMBY [not in my back yard] syndrome is
of importance here),
2. cost, and
I. environmental effects.
The five case studies presented a diverse set of physical,
chemical, and biological characteristics related to sediment
contamination. In the case of the James River, the chemical of
concern, kepone, was a chlorinated pesticide that entered the aquatic
environment directly from the manufacturing process. In effect, it was
a point source that impacted approximately 500 km2 of river bottom.
New Bedford Harbor exemplified a relatively confined point source of
PCBs and the trace metals cadmium, copper, lead, and non-point sources
of PAHs. Approximately 4 km2 of New Bedford Harbor were contaminated
where tidal current velocity and range are 25 to 122 cm/see and 1 m,
respectively. Commencement Bay sediment became contaminated from both
point and non-point sources by PCBs, PAHs, hexachlorobenzene, 4-
methylphenol, and the trace metals arsenic, cadmium, copper, lead,
zinc, and mercury. Approximately 2.1 km2 of Commencement Bay have
been deemed contaminated enough to require clean-up, mostly in
sheltered waterways. Contamination in the Hudson River is pre-
dominantly PCBs and chlorinated hydrocarbon pesticides, but also
includes heavy metals. The major source of PCBs to the system was
discharges from two General Electric capacitor manufacturing facilities
in the upper part of the Hudson River. River flow is variable due to
hydroelectric plants. Sixty percent of the contamination in the Hudson
is contained in 40 hot spot areas in the river sediments. The Navy
Homeport project in Everett, Washington contains approximately 775,800 m
of contaminated sediment with concentrations of PAHs, PCBs and heavy
metals (arsenic, cadmium, copper, lead, mercury, and zinc). The con-
taminated area covers 0.3 km and is located in an urban embayment
(ranging in depth from 28 to 40 ft. with 11-ft tides and quiescent
near-bottom velocities (10 to 20 cm/see).
All the case study areas exhibit stressed biological communities or
organisms that have accumulated some or all of the contaminants in
their tissues. There was no evidence that biota in the James River
have been harmed by kepone, but they do have tissue concentrations in
excess of FDA action levels for human consumption. In New Bedford
Harbor, there was an apparent chronic toxicity gradient from the
Acushnet River to outer New Bedford Harbor, coincident with a gradient
in PCB concentrations. Historical data on Commencement Bay indicate
high sediment toxicity, accumulation of toxic substances in indigenous
biota, and the presence of liver abnormalities and tumors in flatfish.
In the Hudson River, high levels of PCBs were detected in fish as early
as 1969, and the striped bass fishery was closed. The sediments of
concern in the Everett Homeport project contain stressed benthic
communities with low biomass values, low diversity values, and low
Infaunal Trophic Index values.
Various remedial actions have been or are being cons idered for the
five areas . In the James River, chemical conversion, stabilization,
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dredging, and sorption were considered. The cost estimates ranged from
$3 x 10 to in excess of $10 x 109. None of these were chosen and
natural sedimentation has decreased the biological availability of the
contaminant to the point that commercial fishing restrictions have now
been lifted. For Commencement Bay, in situ capping, dredging with
various confined disposal options, and treatment are being considered.
The choice of remedial actions has not yet been made, thus costs are
not available. Evaluation of remedial options for New Bedford Harbor
are ongoing. In situ capping, dredging-disposal, and dredging-
treatment-disposal are being considered. Cost estimates range from $20
x 106 to $200 x 106. A course of action was to be chosen by June 1989.
In the Hudson River, proposed hot spot dredging was considered,
followed by a number of options, including upland disposal, inciner-
ation, basic extraction sludge treatment, ozone-ultraviolet exposure in
an ultrasonic bath, microbial treatment, and steam Gasification. The
cost of these options ranged from $20 to $160 per m . Alternatives
continue to be considered and weighed, and the search continues for a
final solution to PCB removal or destruction in the sediments to be
dredged. Contaminated sediment disposal options for the Everett
Homeport project were nearshore/intertidal disposal, upland disposal in
a saturated or unsaturated sediment condition, or conf ined aquatic
disposal (capping in deep water). The last of these was chosen and its
estimated cost is $17.5 million, or $5.30/yd3 (@ $6.90/m3~. Effective-
ness of the capping will be determined by extensive monitoring.
Mark Brown, representing the New York State Department of
Environmental Conservation, presented the department's perspective on
Hudson River PCB clean-up efforts. He reported that removal of
approximately 50 percent of the total PCBs, corresponding to
approximately 30 percent of the erodible PCBs, was now anticipated.
The contamination has been well defined and will be removed "because it
is there." The contamination has accumulated in areas of low energy,
and predicting its mobilization has been difficult. Removal of all
contamination is not feasible. Sediments with PCB concentrations of 25
to 50 mg/kg will be left in certain areas of the Hudson River.
John Brown, of General Electric Corporation, discussed the natural
PCB degradation in the Hudson River. The nature, cause, and environ-
mental significance of biodegradation of PCBs have been investigated.
The biodegradation process has been duplicated in the laboratory and
follows the same processes found naturally in many systems. The no
action alternative is viewed as a preferable option where there is a
naturally occurring, gradual lowering of the hazard.
Investigation of the Buffalo River was described by Gerhard Jirka
of Cornell University. He stated that simple, realistic prediction
tools for evaluation of the no action alternative are needed.
Combinations of field data, laboratory experiments, and models should
be considered. For the Buffalo River, an extension of the COE's HEC-6
model was used to assess movement of contaminated sediment under
expected flow conditions. The important considerations included time
horizon, sequence, and sensitivity. Extreme events were found to have
great influence on the results.
Representative terms from entire chapter:
contaminated sediment
