Overnight overflow in Duwamish River after West Seattle pump-station malfunction

(Port of Seattle file photo of park near outfall that overflowed)

The King County Wastewater Treatment Division disclosed this afternoon that a pump-station malfunction caused a combined-sewer overflow into the Duwamish River during heavy rain overnight:

King County crews this morning stopped a combined sewer overflow that occurred overnight, caused by an electrical malfunction at a pump station. Employees initiated a cleanup by mid-morning.

The electrical malfunction — (compounded) by the heavy rainfall — caused a mixture of stormwater and wastewater to back up from maintenance holes and into two local businesses and overflow into the Duwamish River. Staff from Seattle Public Utilities discovered the overflow and alerted King County.

Crews from King County Wastewater Treatment Division responded just after 2 a.m. to the West Marginal Pump Station (7119 West Marginal Way SW). Crews determined that electrical equipment had malfunctioned and prevented the system from operating normally, causing sewer backups and the release of combined stormwater and wastewater into the river.

The combined flow was released from an outfall located near t̓ałt̓ałucid Park and Shoreline Habitat — formerly 8th Avenue South End Park [map] — along the south bank of the Duwamish River. County employees are working to determine the amount of combined sewer that flowed in the river. King County is working to repair the pump station equipment and clean up any affected property in the area.

The Wastewater Treatment Division reported the overflow to the Washington State Department of Ecology and is coordinating with Public Health – Seattle and King County to determine the impacts to public health, based on water quality testing results along the river. It is generally recommended that people avoid contact with local water bodies near a combined sewer overflow outfall for 48 hours following a discharge event.

6 Replies to "Overnight overflow in Duwamish River after West Seattle pump-station malfunction"

  • 937 March 1, 2024 (12:21 pm)

    Fines? Nah…

    Organization held accountable? Nah…

    Anyone fired? Nope.

    ‘OMG another toilet overflowed at Harbor West!! Get the pitchforks!!!’

    • John March 1, 2024 (3:15 pm)

      That’s incorrect. The county does get fined. And does get sued by the tribe. The County is hampered by an aging infrastructure and by decisions made decades ago. The combined sewer system is a combination of sanitary waste and storm water. Unfortunately during storms that means tremendous stress in the system. Thankfully, it’s 90% rainwater that overflows during storm events, bad but not as bad as it could be.

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