Southern California Edison officials are investigating the release of about 7,000 gallons of partially treated wastewater into the Pacific Ocean on Wednesday from the San Onofre Nuclear Generating Station.
A sudden surge of water "basically flooded the sewage treatment plant, it didn't overflow but it flooded a different basin inside the plant and then pumps kicked on and continued to pump the water out to the ocean," Ron Pontes, the plant's environmental decommissioning manager, said at a virtual community meeting Thursday night, the San Diego Union-Tribune reported.
"Now we're investigating where did this large slug of water come from," Pontes said. "Once we figure that out, we will restore the (sewage treatment) plant and make sure it's operating properly and place it back in service."
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The sewage was a "non-radiological release," the officials said.
SCE operates the plant, which shut down as an active nuclear power plant in 2012. The utility is in the process of moving the plant's canisters of nuclear waste from their current location in a wet storage facility to dry storage, which will allow the company to begin dismantling the plant.
SCE said earlier this week that it will continue to transfer the canisters to a newly constructed dry storage facility on the north end of the plant, despite the ongoing coronavirus pandemic.
The Nuclear Regulatory Commission, the San Diego Department of Environmental Health, the water board and California State Parks have been notified about the release, plant officials said.