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West Point Treatment Plant, Suquamish Tribe
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King County explains how latest West Point spill happened

The West Point Treatment Plant neighbors Seattle's Discovery Park near the Magnolia neighborhood. (King County)

Another sewage spill at the West Point treatment plant at Discovery Park had millions of gallons of wastewater flowing into the Puget Sound.

During the power outages earlier this week, about 11 million gallons of untreated water flowed into the sound from West Point, of which about two million gallons were sewage.

Robert Waddle, operations manager for the county’s Wastewater Treatment Division, said the record rain caused water flows at the treatment’s maximum capacity. When the power went off, pumps temporarily shut down. It was about two hours until pumps worked at full capacity again.

“It was the perfect storm to cause an event like this — extremely high flow, combined with a power loss,” Waddle said.

Council, environmentalists seek answers in West Point sewage plant meltdown

When the power took the pumps offline, all that wastewater had nowhere to go except the sound. The only alternative to letting the water cascade into the bay was flooding the treatment plant with wastewater — which Waddle said not only would have been costly in damage, but could have threatened the safety of those working in the plant.

After the 2017 disaster that saw hundreds of millions of gallons of raw sewage spill into the sound, Waddle said they made recommended upgrades and implemented additional training for staff. However, he noted that these changes could not have prevented what happened this week because this storm was out of everyone’s control. The only way to get as close as possible to 100% guaranteeing no overflows, he said, would be extremely expensive.

“To make the system so it never has a failure, always meets permit, … we’re talking about sewer bills an order of magnitude higher than they are,” he said. “There are none of us who want sewer bills 10 times higher, and there are very few of us who could actually afford it.”

It’s a cost-benefit analysis, Waddle said. How much money does the county spend preparing for something that may only happen once in hundreds of years?

“We typically design things to say ‘a 100-year flood’ — the equivalent of the worst storm in 100 years, and that’s the volume that you say, ‘I want to be able to treat that,'” Waddle explained. “A situation like this, that might have been a 200-year flood, or a 500-year.”

He believes the amount spilled this time was not enough to damage the sound, and called it “a drop in an infinite bucket of water.” After the 2017 event, which spilled more than 250 million gallons — all of which was raw sewage — the county concluded no environmental damage had been done. Waddle pointed out that this was far less, especially the portion that actually comprised sewage.

King County Councilmember Jeanne Kohl-Welles, in whose district the West Point plant lies and who pushed for the post-2017 review of West Point that recommended the upgrades made, said she is dismayed to see another spill at the plant.

“We can’t continue like this,” she told KIRO Radio.

Following the 2017 spill, she had the county set aside funding for a study by NOAA to look at the effects of wastewater spills on salmon and the endangered orcas that rely on those salmon. That study has been postponed due to COVID-19.

Kohl-Welles believes the county’s sewer system, which is connected with those of local cities, needs to be redone. She will be pushing for that with her council colleagues.

“We really have to reevaluate our current sewer system, which obviously would likely require a significant amount of investment and a lot of collaboration,” Kohl-Welles said.

She fears high-flow situations will become the norm in the coming years.

“I believe in science, so I believe in climate change happening, and that we’re likely to get more and more of these events happening,” she said. “So we’ve got to be responsive.”

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