The Department of Ecology is investigating a possible unauthorized discharge at two of King County’s sewage plants, one of which is in Renton.
The Renton South Wastewater Treatment Plant potentially discharged 1.54 million gallons of wastewater that wasn’t fully treated. Through the investigation the Department of Ecology will learn the full water quality impact.
It’s believed that the wastewater wasn’t fully treated with chlorine, the final step in the disinfection process, but did go through the rest of the water treatment, said Colleen Keltz, Department of Ecology Communications Manager.
“We’re still learning what happened,” Keltz said.
Keltz said the investigation will be a priority as they receive more information. If the failure is a violation of the permit, it could result in anything from action needed at the sewage plant to a fine.
At about 1:40 p.m. Thursday, July 18, a complete loss of power at the facility halted the chlorinating for 51 minutes, according to the Department of Ecology. Power loss reportedly impacted a valve and caused the chlorine feed to fail.
King County Wastewater Treatment Division Communication’s spokesperson Marie Fiore stated in an email the power outage happened during a planned upgrade project, leaving the water fully treated but only partially disinfected.
It was mixed with fully disinfected water in a pipe 11 miles long and almost eight feet wide, Fiore stated.
Water treated at the Renton plant discharges two miles offshore, and northwest of Duwamish Head in Seattle, into the Puget Sound. Fiore stated that the water discharges 600 feet deep and dilutes flow quickly and effectively in the Sound.
“Considering the ratio of this dilution, undetectable traces of bacteria would be present and would not result in a water test record,” Fiore stated.
The county reported this incident, and an incident July 19 at West Point Wastewater Treatment Plant in Seattle, to the Department of Ecology.
On Friday, an estimated 3 million gallons of untreated sewage discharged at West Point for approximately 27 minutes, after backup pumping systems failed during power disruptions at the plant. The system diverted incoming wastewater to an emergency outfall near North Beach in Discovery Park, according to Department of Ecology press release.
Ten beaches in King County, and three in Kitsap, closed due to the two sewage releases.
As of 3:30 p.m., Friday, July 19, only Discovery Park North and South beaches remained closed in King County due to the sewage release; Kitsap will keep Fay Bainbridge Park, Indianola Dock and Joel Pritchard Park closed until Monday, July 22.
Other beaches closed in King County are unrelated, including Gene Coulon Memorial Park Beach, which will continue to be closed until Thursday, July 25, due to high bacteria. Information on other closures are available at green2.kingcounty.gov/swimbeach.
In 2017, King County paid the state $361,000 for a West Point plant failure, which went to the eelgrass recovery project.
This story will be updated as more information is released from the Department of Ecology.