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Title: Long-term impacts induced by disposal of contaminated river sediments in Elliott Bay, Seattle, Washington
Authors: Dexter, Robert N.
Anderson, Dale E.
Quinlan, Elizabeth A.
Keywords: Environmental effects
Environmental impact analysis
Dredged material
Dredging spoil
Elliott Bay (Wash.)
Puget Sound (Wash.)
Seattle (Wash.)
Aquatic ecology
Waste disposal sites
Polychlorinated biphenyls (PCB)
Dredging Operations Technical Support Program (U.S.)
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Dredging Operations Technical Support Program (U.S.)) ; no.Technical Report D-84-4
Abstract: Long-term trends in the physical, chemical, and biological characteristics of dredged material at a deepwater, experimental disposal site in Elliott Bay, Seattle, Washington, were studied. This site was studied previously as part of the US Army Corps of Engineers Dredged Material Research Program which determined the behavior of dredged material during disposal and characterized its impact over the following 9 months. The site was selected for additional work for a number of reasons. The dredged sediments contained high concentrations of polychlorinated biphenyls (PCBs) and the benthic community did not recover to predisposal conditions during the original study. Analysis of the data obtained during three cruises over a 1-1/2-year period, initiated 3 years after the original disposal, yielded the following conclusions: (A.) The dredged material deposit was essentially unchanged by physical processes. No evidence of significant erosion or deposition of new sediment was observed, based on bathymetric surveys and direct sediment analyses. In addition, analysis of bottom currents indicated that velocities sufficient to erode the deposit occur infrequently. (B.) The PCBs in the dredged material deposit were chemically stable, with no evidence that either diffusion or degradation was altering PCB concentrations. (C.) Benthic macrofauna at the site were observed to have completely recovered from the impacts immediately following disposal and, in fact, appeared to be present in greater abundance in the dredged material than in the surrounding sediments. This enrichment reflected a biological response to the physical characteristics of the dredged material and/or a greater abundance of detrital food at the disposal, site. (D.) While not exhibiting any toxic response, the macrofauna on the dredged material were found in general to have higher concentrations of PCBs than those from the surrounding areas. The PCB levels in the organisms appeared to be directly proportional to the levels in the ambient sediments. Results of this study provide a basis for a realistic evaluation of the environmental impacts of open-water dredged material disposal and thus assist in establishing environmentally sound management strategies for future disposal activities.
Description: Technical Report
Gov't Doc #: Technical Report D-84-4
Rights: Approved for public release; distribution is unlimited
Appears in Collections:Technical Report

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