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West Duwamish Wet Weather Storage
King County’s plans to build a wet weather storage facility to hold stormwater and wastewater that currently overflows into the Duwamish River during large storms.
Project description
King County will build a 1.25-million-gallon underground storage tank near the intersection of Southwest Michigan Street and Second Avenue Southwest to hold stormwater and wastewater that currently overflows into the Duwamish River during large storms. The water in the storage tank will then flow to the West Point Treatment Plant for treatment before it is safely released into Puget Sound. This storage tank will reduce overflows and pollution into the Duwamish River. The County will also build supporting infrastructure underneath West Marginal Way Southwest.
The project design is nearly complete. Construction is anticipated to begin in 2025.
Project update
March 2025
Construction is coming soon!
Now that the design phase is almost done, King County is preparing for construction. We expect construction to start in late 2025 and continue until summer 2028.
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Stay in the loop as we prepare for construction! Subscribe for project updates by email or text to get updates, surveys, notices, and other information by email and/or text. You can unsubscribe anytime.
Previous project updates
- Post-design survey newsletter, December 2024
- Utility investigation work near First Avenue South Bridge beginning as soon as December 2, November 2024
- Find the King County team at community events this August to learn more about the project and what you can expect during construction, July 30, 2024
- Soil sampling work near First Avenue South Bridge beginning April 8, 2024, March 27, 2024
- Green Jobs Symposium and Career Fair - March 6, 2024, February 13, 2024
- Help shape art at the West Duwamish Wet Weather Storage Facility project by responding to this survey before January 26, 2024, December 12, 2023
- Upcoming opportunities to meet the West Duwamish Wet Weather Storage Facility team and learn about our efforts to reduce water pollution in the Duwamish River, October 2023
- Frequently asked questions, August 2023
- Potholing near 1st Ave S Bridge beginning May 25, May 2023
- Spring newsletter, March 2023
- Surveying near 1st Ave S Bridge beginning November 2, October 26, 2022
- Lane closure on 2nd Avenue SW - October 19 and 20, October 17, 2022
- West Duwamish Wet Weather Storage Facility Online Open House, September 30, 2022
- Design is progressing on the West Duwamish Wet Weather Storage Facility, July 2022
- Soil testing near 1st Avenue South Bridge starting week of May 16, May 2022
- New storage tank near SR 509 will reduce sewage and stormwater spills into the Duwamish River during big storms, November 2021
- West Duwamish CSO Control Project Environmental Review; Opportunity for community input in January, Fall 2021
- Soil sampling and groundwater testing near 1st Avenue South Bridge Week of May 7, May 1, 2018
- West Duwamish CSO Control Project Winter 2017 newsletter, November 2017
- Highland Park project update, October 2017
- Soil and groundwater sampling near 1st Avenue South Bridge Week of June 26, June 18, 2017
- Soil and groundwater sampling near 1st Avenue South Bridge May 30 through June 5, May 23, 2017
- West Duwamish CSO Control Project newsletter, July 2016
- South Park & Highland Park Green stormwater infrastructure newsletter, February 2014
- South Park: Well installation in your neighborhood beginning as early as February 6, February 3, 2014
- South Park: Well installation in your neighborhood beginning November 11, November 5, 2013
- Highland Park: Well installation in your neighborhood beginning November 11, November 4, 2013
- King County source control project in our Duwamish, (2MB), July 2013
Consultants, contractors & suppliers: learn about upcoming contract opportunities including the West Duwamish Wet Weather Storage Facility.