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Incident response

Wastewater Treatment Division staff are prepared to respond to a variety of complaints and incidents related to the regional wastewater conveyance and treatment system including addressing odor complaints, sewer spills, storm-related problems and other incidents.

Incident response notifications

April 28, 2025

King County crews replacing fuse boxes at Vashon Treatment Plant that caused water that had been treated but not disinfected to be released into Puget Sound

The King County Wastewater Treatment Division is replacing the fuse boxes at the Vashon Treatment Plant after crews Friday, April 25, discovered that the disinfection system – the final stage of treatment – briefly malfunctioned.

An estimated 9,100 gallons of water that had been treated but not disinfected was released from an outfall pipe 2,700 feet off the eastern side of the island. Crews discovered the malfunction at about noon and by 1:30 had stopped all flow from leaving the plant. By 5 p.m., crews had restored the plant to normal operation, including the ultraviolet light (UV) system that disinfects the water before leaving the plant. 

The Wastewater Treatment Division immediately notified regulatory agencies Friday afternoon. Public Health – Seattle & King County determined that water sampling, signage, and beach closures were unnecessary due to the depth of the outfall pipes and the distance from the shoreline. 

The Wastewater Treatment Division will replace the aging equipment that caused the disinfection system to temporarily malfunction.

Vashon Treatment Plant cleans water through mechanical and biological processes and disinfects the effluent with a UV disinfection system before sending the water to Puget Sound. It serves about 1,150 people on the island. See how Vashon's treatment system works.

Past incident response notifications

Jan. 8, 2025

Beach closure lifted at Cove Park

King County conducted water sampling on Sunday and Monday. Public Health – Seattle & King County determined that there is low risk of people getting sick and lifted the beach closure at Cove Park Tuesday afternoon. This is the final update for this overflow event.

Jan. 6, 2025

King County crews respond to overflow in West Seattle due to electrical issue

A King County wastewater operator quickly stopped an overflow at a pump station due to an electrical issue on Jan. 5.

The King County Wastewater Treatment Division responded to an overflow at the Barton Street Pump Station in West Seattle on Sunday, Jan. 5.

At around 12:50 p.m., the pump station located in the 9000 block of Fauntleroy Way SW, just north of the Fauntleroy Ferry Terminal, overflowed after equipment inside the facility experienced an electrical issue. A King County wastewater operator reset the pumps and restored the pump station to normal operations. The overflow lasted approximately three minutes.

King County notified the Washington State Department of Ecology and Public Health - Seattle & King County on Sunday.

Because combined flow of stormwater and sewer was released into Puget Sound through an emergency outfall, King County is working with Public Health to monitor water quality in the area. King County posted closure signage at Cove Park on Monday. The beach at Cove Park is expected to be closed until water quality testing indicates it is safe. The public is urged to avoid contact with the water until the signage is removed.

King County’s priority is to protect public health and the environment.

Heathfield Pump Station Wastewater Overflow Response

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On August 15, 2024, crews were conducting maintenance at the Heathfield Pump Station in Bellevue. During the maintenance work, a check valve suddenly closed and caused over pressurization and rupture of one of two force main pipes, sending wastewater into Squibbs Creek (also known as Vasa Creek) and Lake Sammamish. (A force main is a pressurized sewer pipe that typically uses pump(s) to move wastewater uphill.)

The following is a summary of our response activities to date. We will continue to keep the community, jurisdictions, and agencies up to date.

Current status

Pipe repair and condition inspection

Initial inspection of the ruptured force main pipe started on Thursday, Aug. 22, and will continue in the coming days. We have determined that about 100 feet of additional pipe near the pump station needs to be replaced as soon as possible.

King County’s contractor will mobilize a construction crew at the pump station property as early as Monday, Aug. 26, to begin this work.

This phase of the repair work is expected to take 2-3 weeks.

Read the August 23 Update for more information.

Notifications

News releases

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