Received from King County:
A six-year pilot study that begins this month will test the effectiveness of activated carbon as a tool to clean up historic contamination in Lower Duwamish Waterway sediment.
The Boeing Company, King County, Port of Seattle, and the City of Seattle will manage the $4.4 million study at the direction of the U.S. Environmental Protection Agency (EPA) and the Washington State Department of Ecology.
Study results plus tribal and community input will help the EPA decide if this technology could be used to reduce contamination levels in the Lower Duwamish Waterway.
Researchers will apply a layer of clean sand mixed with activated carbon to 3, one-acre sections of the waterway bottom contaminated by polychlorinated biphenyls (PCBs) and other harmful pollutants during the past century.
The areas will be monitored to determine whether the carbon is effective at keeping contaminants away from the small organisms, called benthos, that live in the sediment and serve as the basis of the food chain in the estuary.
Carbon is commonly used as a purifier in a variety of commercial and industrial purposes. Household water and aquarium filters use activated carbon to remove impurities.
Studies to-date in other locations show activated carbon significantly reduces the exposure of organisms to pollutants such as PCBs. PCBs were used commonly in caulks, paints and electrical transformers before they were banned in 1979.
EPA’s proposed plan for cleanup of the Lower Duwamish Waterway calls for dredging to permanently remove contaminated sediment in areas of higher levels of contamination and areas prone to erosion. This activated carbon technology may be used for stable areas with lower contaminant levels.
The study sponsors, King County, City of Seattle, Port of Seattle and The Boeing Company, make up the Lower Duwamish Waterway Group (LDWG). The group has spent $40 million and more than a decade studying Duwamish Waterway contamination and cleanup options.
The LDWG has invested more than $150 million to clean up contamination hot spots, called “early actions,” which reduces PCB contamination in the waterway sediment by half. Later this year, the EPA is scheduled to release the final cleanup plan, called a Record of Decision, for the remaining contamination.
Additional information is available at http://yosemite.epa.gov/r10/cleanup.nsf/sites/lduwamish or by calling Hanady Kader with EPA Region 10 at 206-553-0454.