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Lower Duwamish Waterway
Source Control Investigation
Early Action Area 3. Slip 4
Slip
4 is located approximately 3 miles upstream from Harbor Island, just north of
Boeing Plant 2. The slip encompasses 6.4 acres and is approximately 1,400 feet
long with an average width of 200 feet. The northwest side of the slip is mostly
covered with docks and a berthing area.
Sediments in Slip 4 have accumulated chemical contaminants from numerous
sources. These sources are both historical and potentially ongoing. Chemicals
entered the slip in different ways, such as through direct discharges, spills,
bank erosion, groundwater discharge, surface water runoff, or other non-point
discharges.
In the inner portion of the slip, PCB concentrations have been greater than
state standards since at least 1990. Phthalate contamination is also present.
Under EPA and Ecology oversight, the City of Seattle and King County are
investigating the potential sources of sediment contamination at Slip 4 and
preparing for a cleanup that will begin in 2007.
Georgetown Steam Plant Flume
The Georgetown Steam Plant (GTSP) is located at 6700 13th
Avenue South in Seattle, Washington. It is on the east side of the Lower
Duwamish Waterway. The Site is bordered to the west by Ellis Avenue South,
the south by North Boeing Field, and the northeast by King County
International Airport.
When built, the GTSP was next to the Duwamish River. When the river was
straightened in 1916 to form the Duwamish Waterway, the GTSP Flume (Flume)
was constructed to carry cooling water to Slip Four.
The city of Seattle (City) is preparing to clean and replace the Flume.
The City will conduct part of the Flume project as an Independent Remedial
Action under the Washington Department of Ecology. The remainder is being
performed under Environmental Protection Agency (EPA) oversight as part of
an Administrative Settlement Order on Consent (ASAOC).
The City has completed a State Environmental Policy Act (SEPA) environmental
checklist for the project and has issued a Determination of Non-significance
(DNS). The checklist and a fact sheet about the project can be viewed
below:
Related Information
Additional Resources
This page last updated
02/21/2008
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