Seattle Public Utilities

South Lake Washington Sewage Reduction

Empty lot with concrete and some trees.

SPU property where the underground sewage storage tank will be built.

What & Why

SPU is planning to build additional storage for polluted stormwater and sewage to prevent future overflows into Lake Washington and comply with state and federal regulations. SPU has been considering potential options and locations for underground storage near Rainier Ave. S., between 57th Ave. S. and Lakeridge Park.

Seattle Public Utilities (SPU) held an open house in March 2014 to present information and receive feedback on this project to reduce sewage overflow in South Lake Washington. The options overview (pdf) and display boards (pdf) from the open house provide more background on the project and options SPU has considered.

Preferred alternative

The project team has selected our preferred alternative for this project. The preferred alternative, known as the “East of Rainier Ave.” option, is an underground storage tank to be constructed on SPU-owned property. Additional details are described in the preferred alternative overview (pdf).

New project schedule

After reviewing our sewage overflow reduction program and our regulatory requirements, SPU has decided to reschedule the completion date for this project. We now plan to initiate design in 2020, and complete construction in by the end of 2024. Delaying the project a few years provides an opportunity for SPU to field monitor two nearby projects that will be completed in the next few years. This will help us better understand the modified volumes of stormwater and sewage flows, and determine with more accuracy the required storage needed within this basin.


Grace Manzano, project manager
(206) 233-1534

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