Central Coast Water Board adopts new water quality permits for Diablo Canyon Nuclear Power Plant

SAN LUIS OBISPO - The Central Coast Regional Water Quality Control Board today adopted two permits necessary to extend operations at the Diablo Canyon Nuclear Power Plant, as directed by Senate Bill 846 (2022).

Operated by Pacific Gas & Electric Company and located in San Luis Obispo County near Avila Beach, Diablo Canyon is California’s last operable nuclear power plant. The permits contain critical regulatory requirements for PG&E to continue operations following a state mandate to extend the plant’s operational timeline.

The two adopted permits are a National Pollutant Discharge Elimination System permit, which regulates how the plant discharges once-through cooling water, desalination brine and treated wastewater into the ocean, and a new Clean Water Act Section 401 water quality certification. Both permits are necessary for PG&E to continue its relicensing process with the federal Nuclear Regulatory Commission.

The Central Coast Water Board’s permit renewal process was focused on protecting water quality and ensuring that PG&E operates the plant in compliance with current water quality standards; other aspects of Diablo Canyon’s operations, such as electricity generation, fall outside of the regional board’s mandate and were not addressed.

“Today’s vote comes after an inclusive public process and marks the culmination of years of methodical work by staff to update permits issued decades ago,” said Jane Gray, chair of the Central Coast Water Board. “These permits aim to safeguard water quality by increasing monitoring to ensure that the plant’s cooling water and other wastewater discharges are protective of our coastal waters.”  

Staff comprehensively evaluated PG&E’s compliance with the plant’s current discharge requirements and incorporated new regulatory provisions in the permits. These revisions include new requirements that aim to reduce the harmful effects of the plant’s cooling water intakes on marine life, in compliance with the State Water Resources Control Board’s Once-Through Cooling Policy.

The regional board held a workshop last November and a 30-day public comment period to receive public input on the draft permits.

More information on the permitting process and access to related documents can be found on the regional board’s program page.

The Central Coast Water Board is responsible for protecting and restoring water quality in a 300-mile-long coastal region, from southern San Mateo and Santa Clara counties to the northern part of Ventura County. Protecting beneficial uses in streams, the ocean, and groundwater is essential to ensuring water quality and protecting the health of humans and wildlife.