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Seola Creek drainage basin map - small size
Seola Creek drainage basin (click to enlarge)

Project overview

This project will retrofit King County’s Regional Detention Facility #DR0562 (Seola Pond) with water quality features. This is a collaborative effort between King County and the City of Seattle. A portion of funding for this project also comes from the Washington State Department of Ecology in the form of a stormwater facility retrofit grant.

The Seola Creek watershed consists of areas of the City of Seattle, unincorporated King County and the City of Burien. The Seola Creek Drainage Basin is an urbanized area that was largely developed before stormwater runoff quantity and quality controls were required. Currently, urban stormwater runoff from this area flows directly to Puget Sound without benefit of water quality treatment. The Seola facility was constructed as a joint King County/City of Seattle project in 1990 to reduce local flooding. It is located at Southwest 105th Street and 30th Avenue Southwest, the approximate center of the drainage basin.

The Seola facility and the pipe systems serving the facility are undersized with respect to the area of the upstream drainage basin. During two- to five-year storm events, the Seola facility backs up, overtops 30th Avenue Southwest and flows onto privately owned properties.

Project description

The Seola Pond Regional Detention facility will be converted into a combination detention pond/wetpool. The facility will be enlarged and retrofitted with a permanent wetpool for water quality treatment. This will reduce the amount of pollutant transport to Seola Creek and ultimately, Puget Sound. The hydraulics of the Seola facility will be improved to foster healthy wetland plantings and consequently improve water quality. This project will also retrofit a roadside ditch upstream of the pond to employ bio-filtration to remove pollutants.

Flood protection will be increased by excavating additional live stormwater storage within the facility and installing an additional emergency pond overflow pipe.

Seola Creek detention facility
Seola Retention/Detention facility
Seola Creek project aerial photo
Seola Creek Retrofit Plan and Aerial

Project timeline

Benchmark Targeted Completion Date
Community Outreach Ongoing
Complete Feasibility and Alternative Analysis 1st Quarter 2014
Preliminary Design 2nd Quarter 2014
Public Meeting 2nd Quarter 2014
Complete Final Design 4th Quarter 2014
Receive Permits 4th Quarter 2014
Invitation to Bid 1st Quarter 2015
Construction 2nd Quarter 2015

Project documents

30% Plans

Lead agency

This project is being designed and managed by the King County Department of Natural Resources and Parks, Water and Land Resources Division, Capital Services Unit. Our primary goal is to implement Surface Water Management Capital Improvement Program (CIP) projects by planning, designing, constructing and managing multidisciplinary teams and stakeholders. 

What is next?

King County is committed to working closely with project area neighbors.  Please contact the Project Manager, Wendy Kara, P.E. for more information regarding this project.

Drainage problem?

For the King Drainage, report drainage problems online or call 206-477-4811.
For the City of Seattle, report problems from Seattle Public Utilities home page or 206-386-1800.

For more information about Seola Creek Basin Retrofit Project, please contact Wes Kameda, project Manager, WLR, Capital Services Unit.