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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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21 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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22 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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23 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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24 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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25 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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26 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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27 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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28 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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29 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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30 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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31 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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32 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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33 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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34 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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35 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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36 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: