San Onofre treatment plant problem leads to release of 7,000 gallons of partially treated sewage into ocean

A water treatment plant at the now-closed San Onofre Nuclear Generation Station released about 7,000 gallons of partially treated sewage into the Pacific Ocean on Wednesday, March 25.

In an alert to state regulators, Southern California Edison, which operates the power station, said an unexpected surge of wastewater led to an “upset” at the treatment plant that morning, triggering an alarm but allowing the sewage to flow through a 6,000-foot pipe out into the ocean before workers could turn off the pumps.

The sewage was diluted, but the facility couldn’t fully process the influx of water, said John Dobken, a spokesman for Edison.

The company was investigating what led to the surge of water. The release was “non-radiological,” Dobken said.

In the alert — sent to the California Governor’s Office of Emergency Services at just past 9 p.m. on Wednesday — workers said the influx of water “caused the partially treated sewage to get to the effluence.”

They said the sewage was “released into a tributary of the Pacific Ocean.” the workers wrote.

“The sewage treatment plant shut down all their pumps to ensure no more material is released,” the alert read. “The released material is unrecoverable.”

The sewage system was taken out of service while workers ensured it can be operated safely again.

While the system was offline, portable toilets with sinks were set up for employees to use the restroom. Employees could also still wash their hands at sinks in the power station’s bathrooms.

The San Onofre power plant has been closed since 2012. Spent fuel pools remain at the site, for years a source of concern for local activists and surfers.

Effluent from the plant with minuscule amounts of radiological material is periodically released through conduits emptying more than a mile into the ocean and 50 feet below the surface. Wednesday’s sewage spill was unrelated to the regular releases, Dobken said.

Though the plant is closed, workers tasked with fully decommissioning the facility are still there.

A complete tear down of the facility, which eventually will bring down the plant’s twin domes visible from the 5 Freeway, began in February as scheduled, Dobken said.

Some work was curtailed amid the outbreak of coronavirus this month. In a statement, Edison said its teams at the site were evaluating how much of its deconstruction activity could continue while still maintaining worker safety.

Edison cancelled non-essential meetings, and held others, including a public meeting last Thursday, through teleconferencing.

Changes also meant “practicing social distancing, hand-washing and limiting physical sharing of documents,” according to the statement.

Cleaning crews are wiping down stations before and after shift changes. Tours of the facility were suspended. And screening stations were set up at facility entrances for employees who might have the virus.