Information from King County

During a period of heavy rain and high tides, King County crews quickly responded when the Alki combined sewer overflow (CSO) treatment facility flooded with mixed stormwater and wastewater on Wednesday, Jan. 18.

During the storm, the County’s 63rd Avenue Pump Station sent high flows to the Alki Combined Sewer Overflow (CSO) treatment facility at 3380 Beach Dr. SW.

The pump station is designed to discharge treated stormwater and wastewater flows exceeding capacity through an outfall extending into Puget Sound. High tides can add to the flow going to the CSO treatment facility.

High flows from the pump station flooded the Alki CSO treatment facility, causing an overflow into a nearby storm drain that empties into Puget Sound. The volume and duration of the overflow have not yet been determined.

King County reported the overflow to health and regulatory agencies. A cleanup crew and vacuum truck removed remaining wastewater in the building. King County employees posted signs by the beach and employees with the County’s Environmental Lab conducted water quality monitoring.

Operations employees are investigating the equipment problem.