As of March 16, 2017, millions of gallons of raw sewage and untreated runoff have poured into the United States’ second-largest estuary since a massive sewage treatment plant experienced equipment failures that forced it to stop fully treating Seattle’s waste. The county-run facility has been hobbling along at about half-capacity since a Feb. 9 electrical failure resulted in catastrophic flooding that damaged an underground network of pumps, motors, electric panels and other gear.
The sewage treatment plant — Washington state’s largest — is only partially treating dirty water that goes down Seattle toilets and washes off roofs and roads before discharging it into Puget Sound. It’s likely to face fines for violating federal clean-water laws. “It has been a disaster, and we’re not out of it yet. We still don’t know really what went wrong,” said Jeanne Kohl-Welles, a King County councilwoman whose district includes the 32-acre West Point Treatment Plant, on the shores of Puget Sound next to Seattle’s largest public park. County officials say crews have been working around the clock to repair about $25 million in flood-related damages and bring the plant to full operations by the end of April.
The sewage spill is a potential black eye for a region that prides itself on its environmental consciousness. Years of work have gone into trying to clean up the nation’s second-largest estuary, a vast inlet where water from the Pacific Ocean mixes with water draining from thousands of streams and rivers. One recent effort banned boats from dumping raw or partially treated sewage. In all, about 30 million gallons of raw sewage have poured into Puget Sound — during the initial breakdown and on two other occasions.
Wastewater moving through the plant is getting primary treatment. Dirty water is screened to remove trash and debris, with some solids settling out, before it’s disinfected, de-chlorinated and released through a 300-foot-deep emergency pipe designed to diffuse the waste into rapid currents. Since Feb. 9, there has been no secondary treatment, a process that relies on beneficial organisms to clean the waste and is required by federal clean-water laws.
Events unfolded quickly in the early hours of Feb. 9. Power went out to two sets of pumps that discharge treated wastewater into Puget Sound. Float switches designed to detect high water levels inside the tanks also failed, allowing water to top over and flood surrounding areas. Crews worked fast to divert the flows to bypass the plant and go directly into the sound, but the flooding damage was done. While rain did not cause the electrical failure that set problems in motion, it certainly exacerbated it, said Robert Waddle, plant operations manager. The facility typically handles about 90 million gallons a day, but it was near peak with 440 million gallons because of heavy rain.