Stay out of the water near the west mouth of the Duwamish River. That’s the health alert from Public Health Seattle and King County because of a combined-sewer overflow reported by the King County Wastewater Treatment Division:
As rainfall hit the region, the King County Wastewater Treatment Division had an unpermitted overflow of combined wastewater and stormwater near the Duwamish West Waterway on Wednesday night, Sept. 25.
At around 7:50 p.m., the Harbor Avenue Regulator Station at 3432 Harbor Ave. SW in West Seattle malfunctioned and released a mixture of stormwater and wastewater from a <strong>combined sewer overflow (CSO) outfall near Chelan Avenue Southwest, an industrial area by the Port of Seattle’s Terminal 5. CSO outfalls are specific relief points into nearby bodies of water to prevent backups into homes and businesses. The regulator station, which controls flow between sewer lines, has resumed normal operations. We are looking into the cause of the equipment malfunction.
The overflow stopped within 12 minutes as levels in the system went down. Early estimates show approximately 58,000 gallons of combined flow were released into the Duwamish Waterway. This water typically contains about 90% stormwater and 10% wastewater.
We reported the overflow to the Washington State Department of Ecology and are notifying nearby businesses. We are also working with Public Health – Seattle & King County (PHSKC) and are following its guidance. As a precaution, PHSKC advises the public to avoid contact with the water in the Duwamish West Waterway and Elliott Bay (east of Jack Block Park View Point) for seven days (until Wednesday, Oct. 2, at 8:05 p.m.).
A county document (page 10) explains what the regulator station does: “The Harbor Avenue regulator station regulates flow from the north and northeast areas of West Seattle into Delridge trunk. Wastewater flows directly through the station into the trunk. High flows can also be sent to West Seattle pump station.”
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