Lower Duwamish Waterway
Until the 20th century, the Duwamish River meandered widely through a valley
consisting of floodplains, freshwater wetland, and tidal marshes before emptying
into Elliott Bay, Puget Sound, near Seattle, Washington. In the early 1900’s,
the lower portion of the Duwamish River was straightened and dredged to improve
navigation and industrial development. The material dredged up from the bottom
of the river was used to create Harbor Island. Since 1916, parts of the river
have been regularly dredged to support ship navigation.
Click here to view Historical Maps of the Duwamish River from 1945 and 1955.
1945 (a) historical sites
1945 (b) historical sites
1955 (a) historical sites
1955 (b) historical sites
The River Today
The Lower Duwamish Waterway Superfund site is made up of approximately 5.5
miles of the downstream portion of the Duwamish River which flows into Elliott
For decades much of the land adjacent to the Lower Duwamish Waterway has been
industrialized. Current commercial and industrial operations include cargo
handling and storage, marine construction, boat manufacturing, marina
operations, concrete manufacturing, paper and metals fabrication, food
processing, and airplane parts manufacturing.
This waterway serves as a major shipping route for containerized and bulk cargo.
Common shoreline features within the Lower Duwamish Waterway include constructed
bulkheads, piers, wharves, buildings extending over the waters, and steeply
sloped banks armored with fill materials.
Although the Lower Duwamish Waterway is viewed primarily as an industrial
corridor, two residential neighborhoods border the banks of the river:
South Park and Georgetown.
There are also small patches of inter-tidal habitats where birds, fish, and
marine invertebrates live. Kellogg Island is the largest continuous area of
inter-tidal habitat remaining in the Lower Duwamish Waterway. Over the
past 20 years, public agencies and volunteer organizations have worked to
restore intertidal and subtidal habitat to the river. Some of the largest
restoration projects are at Herring House Park/Terminal 107, Turning Basin 3,
Hamm Creek, and Terminal 105.
Contaminants in the Lower Duwamish sediments include, but are not limited to,
PCBs (polychlorinated biphenyls)
PAHs (polycyclic aromatic hydrocarbons), mercury, other metals, and
phthalates. In September 2001, the U.S. Environmental Protection Agency (EPA)
added the LDW to the Superfund or National Priorities List. In February 2002 the
Washington State Department of Ecology (Ecology) listed the LDW under the
authority of the Washington Model Toxics Control Act (MTCA).
Many sources have contributed to the contamination, such as marina operations,
shipyard and aircraft operations, combined sewer overflows (CSOs)
more than 100 storm drains, and other industrial uses.
Early Action Areas
The concentrations of sediment contamination in the Lower Duwamish Waterway
vary widely. Many areas exceed the Washington Sediment Management Standards
and/or regional Dredged Material Management Program criteria.
As part of the first phase of the remedial investigation, seven priority areas
of the waterway that had higher contamination levels were identified for early
Sediment removals took place at the Duwamish/Diagonal Way (Combined Sewer
Overflow/Storm Drain (CSO/SD). The Norfolk CSO sediment removal was
completed before the Superfund work began in the waterway.
Preparation for sediment cleanup is currently in progress at the following
early action areas: Slip 4, Boeing Plant 2, and Terminal 117. Work at
other early action areas will be considered as additional information is
gathered in the second phase of the remedial investigation, and as resources
become available. Source control action plans are complete for Duwamish/Diagonal
and Terminal 117. The source control action plan for Slip 4 is in
development. These plans will contain information on the source areas, the
source control work, and monitoring that are needed, and how progress for each
early action site will be reported.