Seattle Public Utilities

Delridge Sewer System Improvements

  • Delridge Sewer CSO 2 Delridge sewer improvement project area.
  • Delridge Sewer CSO 3 Delridge sewer improvement project area.

What & Why

Seattle Public Utilities (SPU) is currently working on two projects in the Delridge neighborhood. This project will improve the sewer system, and the other will create a natural drainage system.

What’s happening now?

Construction on the two sewer improvement projects is now complete and both combined sewer overflow (CSO) sites will be fully operational by the end of the year.

Now that construction is complete, you may notice a few remaining activities in the area:

  • A permanent public art piece commissioned through the City of Seattle’s Percent-for-Art program will be installed in 2016.
  • Ongoing equipment testing at both sites and the diversion structure behind the Village West Apartments building.

Thank you for your patience during construction.

Project goals and benefits

The combined sewer overflow (CSO) tanks — one at the corner of Delridge and Orchard (CSO 2 fact sheet (pdf)) and the other at the corner of 22nd and Henderson (CSO 3 fact sheet (pdf)) — were built in the 1980s and, due to their age, did not operate as efficiently as originally designed.

SPU crews replaced the control systems at both CSO sites. Fixing these facilities will:

  • Improve the ability to monitor and control the amount of flow allowed into the sewer system.
  • Reduce the frequency and volumes of sewage overflows into Longfellow Creek.
  • Reduce maintenance costs.

Project documents


Tara Wong-Esteban, project manager
(206) 684-5903

Learn about the Delridge Natural Drainage System project