Duwamish River

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Duwamish River
Lower Duwamish River.jpg
The lower Duwamish Waterway and the First Avenue South Bridge (State Route 99), looking north. Slips 1, 2, and 3 can be seen on the eastern bank. Kellogg Island is the crescent-shaped island in the upper right portion. Terminal 115 is located in the central portion
Country United States
State Washington
Cities Seattle, Tukwila
Source Green River
Mouth Elliott Bay
Length 12 mi (19 km)

The Duwamish River is the name of the lower 12 miles (19 km) of Washington state's Green River. Its industrialized estuary is known as the Duwamish Waterway.


This 1909 topographical map of Greater Seattle shows the old route of the Duwamish (lower center).
Maps showing the changes of course and nomenclature of rivers in the Duwamish Valley, 1899-1959.

Until 1906, the White and Green Rivers combined at Auburn, and joined the Black River at Tukwila to form the Duwamish. In 1906, however, the White River changed course following a major flood and emptied into the Puyallup River as it does today. The lower portion of the historic White River—from the historic confluence of the White and Green Rivers to the conjunction with the Black River—is now considered part of the Green River. Later, in 1911 the Cedar River was diverted to empty into Lake Washington instead of into the Black River; at that time, the lake itself still emptied into the Black River. Then, with the opening of the Lake Washington Ship Canal in 1916, the lake's level dropped nearly nine feet and the Black River dried up. From that time forward, the point of the name change from Green to Duwamish is no longer the confluence of the Green and Black Rivers, though it has not changed location.[1]

The native Lushootseed name of the Duwamish River (and of the Cedar River) was Dxwdəw. The Lushootseed name of the Duwamish tribe was Dxw'Dəw?Abš or Dkhw'Duw'Absh. Both of these have been anglicized as Duwamish.

Modern use[edit]

The Green River at Tukwila, slightly upstream of where it becomes the Duwamish.
The Duwamish at South Park, Seattle

The Duwamish Waterway empties into Elliott Bay in Seattle, divided by the man-made Harbor Island into two channels, the East and West Waterways.

Due to 20th century industrial contamination, the lower 5 miles (8.0 km) of the Duwamish was declared a Superfund site by the United States Environmental Protection Agency. The contaminants include PCBs, PAHs, mercury, and phthalates.[2] The cleanup of the river has been controversial: one plan for an "early action" or hotspot cleanup proposed to dredge contaminated sediment and dump the resulting sludge in Tacoma's Commencement Bay, 26 miles (42 km) to the southwest. Opposition to this plan in both Seattle and Tacoma forced the sludge to be shipped to Klickitat County in south central Washington instead of disposal in Puget Sound.[3] The riverwide cleanup plan was released for public review on February 28, 2013. EPA's Community Advisory Group for the site, the Duwamish River Cleanup Coalition/Technical Advisory Group, has conducted a review of the plan and published a Community Fact Sheet with a summary of its assessment and recommendations for improvement. Comments on the plan are due to EPA by June 13, 2013.

Along with the contaminants already mentioned above the Duwamish River faces other types of pollution as well. One other major form of pollution is fecal coliform caused by sewage overflow. Even if these overflows were to be cleaned up the overall quality of the water would not improve much. The Duwamish River's most common pollutant is petroleum.[4] Other contamination would still occur from farms, surface runoff, or failing septic tanks.[5]


Despite the industrialization of the Duwamish river, it remains an important habitat for the thousands of salmon and trout that visit the marshes and estuaries each year to spawn. The Duwamish supports chinook, coho, chum and steelhead, not to mention the more rare sockeye, sea-run cutthroat trout and bull trout. Pink salmon run in the millions every odd-numbered years in recent history.[6] Many of the animal species found in or around the river contain an unhealthy amount of contaminants. For example, other than salmon, any type of fish or shellfish found in the river is unfit for human consumption. It was found that PCB levels in fish and crab that live in the waterway most of their lives are 35 to 110 times higher than in Puget Sound salmon. The Ecological Risk Assessment also found that river otters from the Lower Duwamish River might be exposed to such high levels of PCBs that the growth or survival of their offspring may be reduced.[7]

See also[edit]


  1. ^ "The Green-Duwamish: A River System Re-Plumbed", The Green-Duwamish River: Connecting people with a diverse environment. Duwamish River Cleanup Coalition/TAG. No date, appears to be 2008 or 2009.
  2. ^ "Lower Duwamish Waterway Site". Region 10 Cleanup. U.S. Environmental Protection Agency. Retrieved 2009-04-04. 
  3. ^ Paulson, Tom (2003-09-11). "Tainted sludge won't go to Tacoma". Seattle Post-Intelligencer. 
  4. ^ "Impacts of Environmental Problems on the Reuse and Redevelopment of the Properties in the Duwamish Industrial Area". Seattle, WA: Remediation Technologies, Inc. 1994. 
  5. ^ "Stakeholder Committee Report : Combined Sewer Overflow Water Quality Assessment for the Duwamish River and Elliott Bay". Seattle, WA: King County Department of Natural Resources. 1999. 
  6. ^ "Seattle's Aquatic Environments: Duwamish Estuary" (PDF). City of Seattle. Retrieved 2009-04-04. 
  7. ^ "Lower Duwamish Waterway Superfund Site" (PDF). Region 10 Cleanup. U.S. Environmental Protection Agency. June 2008. Retrieved 2008-11-03. 

External links[edit]

Coordinates: 47°35′04″N 122°21′37″W / 47.58444°N 122.36028°W / 47.58444; -122.36028