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A new sewer pipeline will be installed near the intersection of Rainier Avenue and Martin Luther King Boulevard to divert flows to an existing pipe with extra capacity. Any excess flows from this area will be routed to a storage tank at the intersection of South Hanford Street and South 27th Avenue.


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Project information

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Project need

King County’s pipes in Rainier Valley and elsewhere to send sewage and stormwater to a treatment plant in Magnolia to be cleaned. Pipes in the northern Rainier Valley get too much stormwater during storms and spill into the Duwamish River. These spills are called “combined sewer overflows” or CSOs. King County will build new pipes and a new 340,000 gallon storage tank to keep more pollution out of the Duwamish.

service areaArea served by Rainier Valley Wet Weather Storage Project
 , May 2014

Protects public health

Contact with raw sewage and stormwater can make people sick. Unless they are cleaned at a treatment plant, sewage and stormwater can also harm Puget Sound, Lake Washington, and the Duwamish River. The pipes and plants we have to clean sewage and stormwater help keep us healthy.

Cleans up the Duwamish River

The new pipes and tank will avoid CSOs from Rainier Valley and keep sewage and stormwater out of the Duwamish River. They will keep the Duwamish River cleaner by keeping millions of gallons of water pollution out of the river each year (on average).

Untreated CSO volume reduction, before and after project

How did King County decide what to build?

The county has different tools it can use to keep Rainier Valley’s sewage and stormwater out of the Duwamish River. Not every tool is right for every neighborhood. The Rainier Valley facility must work for a big, very busy area where a lot of people live and work.

What works for Rainier ValleyWhat works for Rainer Valley (  , Spring 2014 newsletter)