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County identifies alternatives to control combined sewer overflows in West Seattle


After receiving a great deal of community input and reviewing several options for each location, projects that will help protect public health and water quality near two popular West Seattle recreation areas will move forward for further environmental review.


After receiving a great deal of community input and reviewing several options for each location, projects that will help protect public health and water quality near two popular West Seattle recreation areas will move forward for further environmental review. The recommendations were made by the King County Department of Natural Resources and Parks Director Christie True.

To control combined sewer overflows (CSOs) from King County’s Murray Avenue Pump Station, one project would entail building a 1-million-gallon storage tank beneath private property across from Seattle’s Lowman Beach Park.

The second project would employ a system of rain gardens and swales – known as a Green Stormwater Infrastructure (GSI) project – between the sidewalks and streets in the Sunrise Heights and Westwood neighborhoods to reduce overflows from the Barton Pump Station near Seattle’s Lincoln Park.

True said both proposals will be evaluated as part of a formal environmental review process conducted under the State Environmental Policy Act (SEPA) in spring 2011.
“Both neighborhoods are densely developed, and that limits the number of suitable locations where these projects can be built,” she said.

“Residents expressed a wide range of opinions and preferences during our public process, and an overwhelming number opposed any major construction inside either Lincoln or Lowman Beach Parks,” she added. “Those options were not pursued because they posed an unacceptable level of impact to the community. We also had to consider the overall cost and technical feasibility.”

The project recommendations seek to balance technical and community considerations with state and federal requirements that King County control sewer overflows at the Barton and Murray pump stations to the state standard of no more than one event per year.

King County’s Barton Street Pump Station, located south of Seattle’s Lincoln Park, currently experiences an average of four overflows a year, while the Murray Avenue Pump Station north of Lincoln Park experiences an average of five.

During heavy rains, the GSI alternative would control CSOs at Barton Pump Station using soils and vegetation to capture and reduce stormwater that would enter the conveyance system. The area’s gentle topography and the connection of street drains to the combined sewer system make the alternative technically feasible.

West Seattle neighbors expressed support for this environmentally friendly solution, which also supports the County’s commitment to energy conservation and sustainability.

Identifying a CSO solution in the Murray basin was significantly more difficult due to the area’s steep terrain and the way in which sewer lines are configured. The volume of stormwater and wastewater to be stored is 10 times greater than it is in the Barton basin. For these reasons, GSI was not a feasible choice for this location.

Moving forward with a proposal for a storage tank across the street from Lowman Beach Park would require King County to purchase six private properties, a fact that County Executive Dow Constantine called regrettable, but necessary.

“As a life-long West Seattleite, I am keenly aware of the importance of every home, whether rental or owner-occupied, to the identity and stability of our community,” said the Executive. “However, the alternatives all have impacts of their own.”

The Murray proposal has the advantage of reducing the impacts of construction on park users and other neighbors. The proposal would also enable some future pump station construction that otherwise would be required in Lowman Beach Park to now be located across the street in the acquired site.

From an operational standpoint, the Murray proposal offers the advantage of a single facility in the immediate vicinity of the existing pump station, which supports reliable operation and efficient maintenance. The County will also seek to work with neighbors and the City of Seattle to make the completed site an asset to the park and to the community.

The SEPA process, scheduled to begin in early 2011, will allow public comment and continued opportunity for stakeholders to remain informed and involved. King County Wastewater Treatment Division staff is committed to working closely with affected community members through design, permitting and construction, which is scheduled to begin in 2013.

People seeking additional information can visit the project website at\csobeachprojects or contact Wastewater Treatment Division community services planner Martha Tuttle at 206-684-1207 or 711 TTY.


People enjoy clean water and a healthy environment because of King County's wastewater treatment program. The county’s Wastewater Treatment Division protects public health, the environment and the economy by serving 17 cities, 17 local sewer districts and more than 1.5 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for nearly 50 years.

Note to editors and reporters: Visit the WTD Newsroom, a portal to information for the news media about the Wastewater Treatment Division, King County Department of Natural Resources and Parks:

Related information

Puget Sound Beach CSO Control Projects

King County Wastewater Treatment