Seattle Public Utilities

Ship Canal Water Quality

ShipCanalWaterQuality

Seattle Public Utilities and King County are building underground stormwater and sewer storage.

What & Why?

Sewage and stormwater from many older parts of the city, including Ballard, Fremont, Wallingford, and Queen Anne, all funnel into one set of pipes. In dry weather conditions, all sewage flows to King County’s West Point Wastewater Treatment Plant in Magnolia. During wet weather conditions, polluted runoff can exceed the pipes’ capacity and send a mixture of stormwater (90%) and sewage (10%) to outfalls that flow into the nearest water body. These combined sewer overflows, or CSOs, contain contaminants that can make people sick and harm fish, wildlife, and the environment.  

Seattle Public Utilities and King County are working together to build an underground storage tunnel to reduce the amount of polluted water that spills into the Lake Washington Ship Canal from Ballard, Fremont, Wallingford, and Queen Anne. The 2.7-mile, 18’10” diameter tunnel will capture and temporarily hold more than 29 million gallons of stormwater and sewage that overflows during heavy rains. When the storm passes, flows will be sent to King County’s treatment plant to be treated and discharged.

What’s happening now?

Learn more about work in your neighborhood:

Project goals and benefits

This project will keep over 62 million gallons of polluted water out of the Lake Washington Ship Canal, Salmon Bay, and Lake Union each year. The project will limit CSOs to no more than one per outfall per year on average, in compliance with state and federal laws.

Get Involved

Stay up-to-date on what’s happening with the Ship Canal Water Quality Project.

Upcoming meetings & events

  • SCWQP tabling at the Fremont Fair (June 16-17)
  • SCWQP tabling at the Ballard Seafood Fest (July 13-15)

Past briefings & events

Interested in seeing the presentation and/or materials for any of the events below?  Contact us at SPU_ShipCanalProject@seattle.gov and we’ll send it to you.

April – June 2015

  • Ballard District Council

July – September 2015

  • Seattle Bike Advisory Board
  • Seattle Freight Advisory Board
  • Wallingford Community Council
  • Wallingford Chamber of Commerce
  • Fremont Neighborhood Council
  • Groundswell Northwest
  • Ballard Chamber of Commerce
  • Ballard District Council

October – December 2015

  • Seattle Pedestrian Advisory Board
  • Wallingford Nearby Neighbors (twice)
  • Queen Anne Community Council

January – March 2016

  • Wallingford Community Council
  • North Seattle Industrial Association Presentation

April – June 2016

  • Groundswell Northwest
  • Tabling at Fremont Fair

July – September 2016

  • Seattle Pacific University
  • Tabling at Ballard Seafood Fest

October – December 2016

  • Draft Supplemental EIS Public Hearing and Open House
  • Fremont Neighborhood Council
  • Ballard District Council

January – March 2017

  • Seattle Department of Transportation & Cascade Bicycle Club (twice)
  • Seattle Freight Advisory Board
  • Wallingford Community Council

April – June 2017

  • Seattle Freight Advisory Board
  • Tabling at Fremont Fair
  • Civil Rights, Utilities, Economic Development & Arts Council Committee briefing

July – September 2017

  • Seattle Bicycle Advisory Board
  • Tabling at Ballard Seafood Fest
  • Burke Gilman Trail, Missing Link: All Segment Workshop

October – December 2017

  • Burke Gilman Trail Missing Link Public Event
  • Burke Gilman Trail Missing Link Self-Guided Walking Tour Project Table
  • Seattle City Light Open House
  • Fremont and Wallingford Drop-ins (3)
  • Wallingford Nearby Neighbors
  • Friends of Street Ends
  • King County

January – March 2018

  • Ballard District Council
  • Fremont Neighborhood Council
  • Queen Anne Community Council
  • Wallingford Community Council
  • Ballard Conveyance Drop-in Session
  • Urban Forestry Commission
  • Seattle Pedestrian Advisory Commission

April – June 2018

  • Ballard District Council
  • Wallingford Chamber of Commerce
  • Fremont Drop-in Sessions