Wallingford Ship Canal Water Quality

What & Why

Seattle Public Utilities (SPU) and King County’s Ship Canal Water Quality Project is a 2.7-mile, approximately 18'10"-diameter tunnel that will capture and temporarily hold more than 29 million gallons of stormwater mixed with some sewage during heavy rains. When the storm passes, flows will be sent to the King County West Point Wastewater Treatment Plant in Magnolia.

The Ship Canal Water Quality Project includes the following activities in Wallingford:

  • Building the eastern end of the new storage tunnel (the tunnel boring machine will complete tunneling at this location)
  • Building a drop shaft to collect flows entering the tunnel and a small above-ground maintenance building near 3500 Interlake Avenue N
  • Installing new pipes to convey polluted stormwater and sewage to the tunnel
  • Providing odor control equipment to minimize odor

What’s happening now?

Ryan! Feddersen has been selected as the public artist for the Wallingford site.  In 2019, she will begin brainstorming concepts and ideas for art placement at the site.  Design of the Storage Tunnel Project (which includes site remediation and shaft construction at the Wallingford site) is near complete and the team is preparing to begin advertisement in March to hire the construction contracting firm.  Additionally, the Storage Tunnel Project includes the conveyance piping work at East Ballard, Fremont and north Queen Anne sites as well as the microtunnel under the Ship Canal between Fremont and north Queen Anne.

Project goals and benefits

This project will keep more than 75 million gallons of polluted water out of the Lake Washington Ship Canal, Salmon Bay, and Lake Union on average 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.