On July 19, a minor power hiccup shut down stormwater pumps at the West Point Treatment Plant, sending 2.1 million gallons of water and sewage spilling into Puget Sound. King County and Seattle City Light are working together to understand how to prevent future releases.
Power to the plant remained on, but for less than a second, it was providing less power than was required by several of the plant’s pumps. In the aftermath of the spill, the county reviewed the situation and has turned its attention to figuring out ways to prevent future situations, said Christie True, director of the county’s Department of Natural Resources and Parks.
“We do believe our employees followed the protocols as they should have to prevent flooding,” True said during an Oct. 21 briefing of the county’s Board of Health.
Around 1 a.m. July 19, the power fluctuated and shut off pumps at the treatment plant, located next to Discovery Park in Seattle. This caused operators to open emergency bypasses around 1:38 a.m., which sent the 2.1 million gallons of water into Puget Sound. Roughly 80% was stormwater and the rest was sewage. Around 30 minutes later, the pumps were operating at full capacity again and the overflow was closed.
On that day, the plant was treating some 300 million gallons of water, around six times what it would normally treat during that point on a regular summer day. And while 2.1 million gallons is a large spill, it was dwarfed by a 2017 disaster that flooded the plant, reduced service for three months — and dumped 235 million gallons of wastewater into Puget Sound.
According to the county, the plant treats wastewater from homes and businesses in Seattle as well as north King County and parts of south Snohomish County.
Mike Haynes, Seattle City Light’s COO, said they were working with the county to figure out ways to better understand the effects of power disruption to the plant.
“We’re never going to eliminate the risks of power dips or outages,” he said.
Recommendations are being developed by a consultant for the treatment plant. The report is due by January.
King County Council member Jeanne Kohl-Welles asked whether backup generators at the plant could prevent similar situations in the future.
However, Christie True of the Department of Natural Resources and Parks said the plant would require a large generator capable of providing 10 megawatts of energy. Additionally, there would still be time needed to switch from system power to generators, which would still shut down pumps.
Following the July dump, the county monitored water quality surrounding Discovery Park and shut down several beaches. All three consecutive days met water quality standards, and the beaches were later opened. True said there wasn’t as much concern about exposing people to potentially toxic materials at West Point because it empties into Puget Sound. Shellfish in the area are also regularly tested for toxins.
True said following the 2017 spill, the county implemented a number of improvements, including improving its control systems, updating emergency protocols and providing more employee training. The Washington State Department of Ecology that year fined King County $361,000 and ordered the county to make more than $1 million in investments to improve the condition of the plant.