Project

The Joint Ship Canal Water Quality Project includes the construction of an underground storage tunnel to reduce the amount of polluted stormwater and sewage that would otherwise flow, during periods of heavy rainfall, into the Lake Washington Ship Canal, Salmon Bay, and Lake Union. This is a joint project between Seattle Public Utilities and the King County Wastewater Treatment Division, which will construct a storage tunnel that will stretch 2.7 miles from the Seattle neighborhoods of Ballard and Wallingford. The boring of the tunnel was officially completed on June 15, 2023. The storage tunnel will have the capacity to store more than 29 million gallons of untreated stormwater and sewage until it can be pumped out and sent to the West Point Treatment Plant for treatment once capacity eases. The tunnel will improve the region’s water quality by eliminating 75 million gallons of untreated stormwater and sewage. Completion of the Joint Ship Canal Project is currently scheduled for August 2026.

The permanent financing for this project will be provided by a combination of loans from the U.S. Environmental Protection Agency (EPA) through the Water Infrastructure Finance and Innovation Act (WIFIA) and the Department of Ecology through State Revolving Fund (SRF) loans. Interim financing ahead of certain of these permanent financing sources is being provided by the Commercial Paper Program and unrestricted cash from the capital fund.