Edmonds treatment plant receiving extra sewage flows following damage to Seattle’s West Point plant

Seattle’s West Point Treatment Plant. (Photo courtesy King County)

The City of Edmonds has been doing its part to assist King County in managing extra wastewater flows following major rain-related damage to Seattle’s West Point Treatment Plant, said Edmonds Public Works Director Phil Williams.

According to Williams, Edmonds for many years has had a “flow swap arrangement” with King County to manage wastewater flows out of the Lake Ballinger pump station, which is located at the King County/Snohomish County border. Under that arrangement, Edmonds treats wastewater from Richmond Beach in exchange for an equal amount of Lake Ballinger area flow that is sent to the King County treatment system.

Edmonds agreed to also accept the wastewater from the Lake Ballinger pump station to assist with the problems that King County is facing at West Point, which suffered catastrophic damage during a Feb. 9 rainstorm, Williams said. As a result of the plant failure, 260 million gallons of raw sewage was discharged into Puget Sound, according to our online news partner The Seattle Times.

According to Williams, both King County and the State Department of Ecology approached Edmonds “to see if we could accept this additional flow to help mitigate the impacts occurring to water quality in Puget Sound.”

Edmonds did not accept additional wastewater from King County until last week’s heavy rains subsided, to ensure that the Edmonds plant could handle its own flows, Williams said. The city, which treats an average of 6 million gallons of sewage daily, is now receiving an average additional 3.1 million gallons daily that would normally go to King County through the Ballinger Pump station.

“This does help to reduce the size of the problem they are dealing with at West Point at least a little bit,” Williams said.

City of Edmonds wastewater treatment plant.

Edmonds will stop accepting the additional flow from King County if heavy rain returns, Williams said. “We can’t let their problem create a problem for us,” he said.

The Times reported on Thursday that King County has stopped discharging raw sewage for now, but will likely start again when rainy weather returns. Officials say the plant will not resume regular service for many weeks. King County’s Wastewater Treatment Division serves about 1.7 million people within a 424-square-mile service area, which includes most urban areas of King County and parts of south Snohomish County and northeast Pierce County.

According to The Times article, the West Point plant normally provides secondary treatment of up to 450 million gallons per day of sewage, wastewater and stormwater. The plant currently is operating at half capacity and is treating stormwater and raw sewage flowing to the plant with primary treatment only. That means solids are screened and settled out, and the rest is disinfected with chlorine, then dechlorinated before discharging the water offshore of the beach at West Point to Puget Sound.

Currents in Puget Sound dissipate the pollution, and large amounts of stormwater in the effluent also mean the sewage is greatly diluted. Williams said that it’s unlikely that Edmonds would be directly affected by raw sewage discharge.

Beaches at nearby Discovery Park are closed, with no date yet for reopening. King County is providing regular updates on the situation here.

 

  1. In 2002 when Edmonds was facing the possible siting of Brightwater on the former site of the storage tanks citizens recommended that West Point separate their sewage from the flow of rain water.
    Is there any talk of doing that in Seattle to help prevent the impact of heavy rains?

  2. Hi Barbara:

    Great question. In the early 20th century, household wastewater and stormwater runoff from streets used to flow in a single pipe to the nearest waterbody because there were no treatment plants. That’s called a combined system, and it’s been many decades since sewers were designed like that. Combined sewer pipes still exist in older parts of Seattle, and today those flows end up at West Point Treatment Plant.

    West Point was engineered to managed these wet-weather flows because sewer separation would be astronomically expensive, and come with massive construction costs and impacts in densely populated neighborhoods. Some separation work took place in the early 1970s under the Forward Thrust grants, and today we’re working to control the amount of runoff that gets into the combined system by building large storage tanks to hold runoff, and offering incentives to residents and businesses in combined system neighborhoods to install rain gardens and cisterns to capture and control this runoff. These efforts will help in the future to control combined sewer overflows and to direct stored runoff to the plant when rains stop and the plant isn’t overwhelmed.

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