PG&E agrees to $5.9 million settlement over dumping of Diablo Canyon cooling water


PG&E reached a settlement with the Central Coast Regional Water Quality Control Board last month, requiring the utility to pay $5.9 million for allegedly failing to comply with regulations pertaining to how it discharges cooling water from Diablo Canyon Power Plant.

The nuclear power plant takes in water from the Pacific Ocean to condense steam after it passes through two electrical generators in a process called “once-through cooling.” Water is then released back into the ocean, and the cycle repeats. Environmentalists have argued the discharge of water into the ocean harms marine life. 

Regulators alleged releases of once-through cooling water from Diablo Canyon into the Pacific Ocean constituted violations of PG&E’s National Pollutant Discharge Elimination System permit. PG&E agreed to the settlement following a Central Coast water board investigation of alleged permit violations associated with the thermal component of the plant’s discharge since it first began releasing once-through cooling water in 1985.

The $5.9 million PG&E agreed to pay will be used for water quality projects that benefit the region, according to the water board.

Additionally, PG&E has been making annual payments to mitigate the impacts of its discharges and is expected to pay about $38 million in total for the plant operations between 2015 and 2025. The mitigation payments are used to support marine protected areas on the Central Coast.

PG&E will shut down Diablo Canyon in Aug. 2025.

“We take protecting water quality and marine habitat very seriously,” Central Coast Regional Water Quality Control Board Chair Dr. Jean-Pierre Wolff said in a statement. “This settlement demonstrates our commitment to safeguard and restore our region’s waters, and the board intends to apply the settlement funds toward high priority water quality projects in alignment with statewide priorities associated with environmental justice, public health, climate change, water supply resiliency or watershed functions that support healthy ecosystems.”