Integrating Sediment Clean Up and Watershed Management for Sinclair and Dyes Inlets, WA USA

Abstract : Integrating contaminated sediment clean up and restoration issues within the larger perspective of watershed management are especially critical in populated coastal and estuarine areas with multiple sources of stress from urbanization and development as well as sediment contaminated from historical sources. Sinclair Inlet and Dyes Inlet, located in the Puget Sound WA, have received historical inputs of contamination from military installations, industrial activities, municipal outfalls, and other nonpoint sources. As part of the record of decision to remediate contaminated sediments near the Puget Sound Naval Shipyard in Sinclair Inlet, sediments were dredged from contaminated areas, placed in an adjacent confined aquatic disposal pit, and covered with clean material dredged to deepen the navigational channel and turning basin. Other cleanup activities included restoring shoreline areas to minimize contaminated soil infiltration and improve shoreline habitat, and conducting a comprehensive cleaning, inspection, and repair of the Shipyard's storm water system. Concurrently, the City of Bremerton, also located in the Inlets, has made significant improvements to its combined sewer and storm water system, nearly eliminating combined sewer overflows and achieving a marked improvement in the water quality of the Inlets. Historical trends of contamination in the Inlets obtained from age-dated sediment cores show contamination levels peaking between 1940 and 1960 followed by an obvious decease in contaminant loads in the most recent deposits. During the interval between 1997-1978 and 2003 (following clean up activities) the sediments in Sinclair Inlet and Dyes Inlet changed significantly in texture by becoming, on average, nearly a full phi size coarser. Currently, models are being developed to simulate contaminant runoff and loading from the watershed and the fate and transport of contaminants in Sinclair and Dyes Inlets.