Minimizing CSOs into Puget Sound

King County has a history of reducing the discharge of untreated stormwater and wastewater into Puget Sound. An integral part of the program is the new Murray Combined Sewer Overflow Control project which minimizes overflows by storing up to 1-million-gallons of excess combined sewage. During heavy rain, the Murray Avenue Pump Station capacity can be exceeded, resulting in untreated CSOs into Puget Sound. The new storage system reduces yearly CSO events from five to one, meeting the Environmental Protection Agency's Consent Decree and improving Puget Sound water quality.

Using a unique circular shape gravity-fed storage tank, automated cleaning system, and odor control system, the facility efficiently fulfills its duty while blending into the neighborhood. Extensive community involvement — including public meetings, a charrette process and advisory groups — reduced visual impacts. The facility encourages public access, improves connectivity and enhances environmental stewardship with a green roof, bioretention swales and permeable pavement to treat stormwater runoff. The artwork creates a “Mountains to Sound” theme, a metaphor for water’s journey from the Cascades to the shoreline, a journey reflected in the facility’s use.

Opened to an enamored crowd, the facility is a model for enhancing the environment and infrastructure while creating a destination for residents.