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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

Aerial map displaying location of the new storage facility and associated structures (two underground structures and two outfall/overflows) next to the Duwamish River.

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 summer 2025.

Project update

November 2024

Utility investigation work near First Avenue Bridge beginning as soon as December 2

Starting as early as December 2, 2024, crews will spend up to three days potholing, or digging small holes, near the future storage tank site in preparation for upcoming construction. This work will help King County to better understand the locations and condition of existing utility lines.

Location of the work area near the future storage tank.
*Each dot on the map represents up to two potholing locations

What you can expect

  • Work hours 7:30 a.m. to 5 p.m. daily for up to three days, starting as early as Monday, December 2. Work on Highland Park Way SW may happen at night to avoid disrupting traffic.
  • Temporary lane closures with flaggers on site to assist vehicle and pedestrian movement.
  • One drill rig and up to four service vehicles on site.
  • Noise and slight vibrations during work hours, including engine noise and periodic hammering.
  • Occasional truck traffic accessing the site during work hours.

Please watch for equipment and signs in the area, travel slowly to stay safe and follow direction from flaggers.

Project design is nearing the finish line. Construction will start in 2025!

Explore our project newsletter and online open house to learn more about the West Duwamish Wet Weather Storage Facility project’s design progress, public art, work force development opportunities.

Read the newsletter and online open house: publicinput.com/westduwamishenglish

Leer el boletín y Jornada de puertas abiertas en línea: publicinput.com/westduwamishspanish

Đọc bản tin và Nhà mở trực tuyến: publicinput.com/westduwamishvietnamese

閱讀時事通訊 和 網上開放日: publicinput.com/westduwamishtraditionalchinese

阅读时事通讯 和 网上开放日 : publicinput.com/westduwamishsimplifiedchinese

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Consultants, contractors & suppliers: learn about upcoming contract opportunities including the West Duwamish Wet Weather Storage Facility.

Project location

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