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EXECUTT~E SUMMARY Contamination of marine sediments poses a potential threat to marine resources and human health (through consumption of seafood) in numerous sites throughout the country--particularly near metropolitan areas. Improving the nation's capability to assess, manage, and remediate these contaminated sediments is critical to the health of the marine environment as well as to its use for navigation, commerce, fishing, and recreation. As widespread as the problem of sediment contamination appears to be, understanding of the geographical extent and ecological significance of the problem is not well developed. In addition, management and remediation of contaminated marine sediments requires grappling with dynamic aquatic environments in which contaminant mobilization can occur in response to remediation itself, or as a result of natural resuspension, transport, and deposition of the bottom sediments. This report, prepared by the Committee on Contaminated Marine Sediments of the Marine Board of the National Research Council, examines the extent and significance of marine sediment contamination in the United States; reviews the state of the art of contaminated sediment clean-up and remediation technology; identifies and appraises alternative sediment management strategies; and identifies research and development needs and issues for subsequent technical assessment. The report contains the results of a symposium and workshop, with supplementary discussion and recommendations by the convertors. The committee members concluded that sediment contamination is widespread throughout U.S. coastal waters and potentially far reaching in its environmental and public health significance. A report sponsored by the U.S. Environmental Protection Agency (EPA), although limited in its data sources, estimated 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 involve marine or estuarine waterways." The National Oceanic and Atmospheric Administration's (NOAA) National Status and Trends Program, which selectively excluded "hot spots" from its sampling, found high levels of contamination in samples from sites in major urban areas, including Boston, New York, San Diego, Los Angeles, San Francisco, and Seattle. However, adequate data do not currently exist for comprehensively pinpointing or prioritizing 1
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2 candidates for remedial action. Even so, the means and methods for making such determinations are available (or close at hand), albeit needing much improvement. They include several that were evaluated by the committee. At present, no single technique is widely accepted and each has its advantages and disadvantages. A number of approaches may be needed to evaluate the significance and extent of contamination at any given site. Ultimately the methods used should be able to be conducted routinely and cost-effectively. In terms of risk to human health, transfer of contaminants from marine sediments to humans is poorly documented and underassessed. However, it appears that there may be cause for concern with regard to persistent bioaccumulative chemicals contaminating seafood. The impact of this type of contamination needs further investigation. Despite the widespread extent of the contaminated sediment problem, remedial actions directed at excavating, treating, or otherwise manipulating contaminated marine sediments have been extremely rare. Under the Superfund law, only sites designated on the National Priorities List can be funded for remediation. The Hazard Ranking System score, which determines placement on this list, gives heavy weight to potential contamination of drinking water sources, but little or no weight to sediment-mediated contamination of edible fish and shellfish. Furthermore, little effort has been made to identify contaminated sites in coastal environments under Superfund.i In its examination of state-of-the-art clean-up and remediation technology, the committee determined that existing technology is adequate in most situations. However, the committee noted that some specialized dredging equipment--e."., to allow excavation of contaminated sediments with a minimum of turbidity--is difficult to obtain in the United States (due to cabotage laws). To alleviate this problem, government support is encouraged for efforts to acquire or develop dredging equipment with features that make it well-suited to the excavation of contaminated sediments. The committee also found that the time required for EPA or its contractors to make a clean-up decision was more often a limiting factor in accomplishing effective clean-up than any constraints imposed by limitations in clean-up science or technology. The time required for a decision was sometimes speeded up, however, where the need for navigational dredging was a driving force. Remediating underwater sediment contamination can be a complex problem. Failure to make a decision may cause the problem to spread. Although in many instances the problem may correct itself given enough time, it is usually desirable to isolate and contain the contaminated area to the extent possible. Allowing the affected area to expand will generally only serve to increase the cost and complexity of the eventual clean-up. More attention needs to be focused on the design of 1Although as many as 141 of 1~100 (13 percent) present and proposed Superfund National Priorities List sites may be located adjacent to coastal areas and may or may not involve coastal sediments, no remedial action has been selected for the great majority of these sites.
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3 rapid short-term actions to limit the spread of contamination at the same time that more elaborate long-term remedies are assessed and developed. In some cases, no action can be the alternative of choice, assuming measures have been adopted to control contamination sources. This may be particularly true when natural sedimentation or dispersal may mitigate the problem or when natural detoxification of contaminants is occurring. During an evaluation process, the effects due to remediation should be compared with those associated with the no-action alternative. The committee recommended that future research and development be focused on establishing better better biological and chemical techniques for rapidly and reliably assessing the presence and severity of bottom sediment contamination, delineating the practical limits of capping as an efficacious remediation technology, identifying interim measures to limit the spread of contaminated sediments while long-term remedies are assessed, and formulating procedures and guidelines that adequately evaluate and prioritize health and environmental risks associated with sediment contamination, and against which effectiveness and clean-up needs can be measured. The committee also believed that in view of the high cost of most remedial actions, greater use should be made of benefit-cost comparisons. This would place investment in this area on the same economic footing as investments in other public projects. Cost-effectiveness analysis of alternative remedial actions, including "no action," should consider both short- and long-term costs, comparisons at and among sites, and incremental costs of additional levels of clean-up of contaminated sediments. Finally, increased emphasis on sediment assessment and clean-up practices has caused rapid changes and developments in state-of-the-art technologies. Developments and experience in methods for applying these technologies are also occurring at a rapid rate. Therefore, it is an important and appropriate role for the federal government (either through individual concerned agencies or, preferably, through a coordinated interagency committee) to frequently review and evaluate the effectiveness and scientific basis for newly developed sediment assessment and clean-up technologies and procedures.
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