Wildfires damage, threaten power facilities in northern California

Two out-of-control wildfires have forced the deenergizing of at least one Pacific Gas and Electric (PG&E) power line, are threatening other power lines and a major water reservoir in northern California, and have caused Gov. Jerry Brown (D) to declare a state of emergency for San Francisco, some 150 miles away.

The Rim Fire, which had burned nearly 150,000 acres of land, including a portion of Yosemite National Park as of midday Aug. 26, has forced the shutdown of two of three generating facilities at the Hetch Hetchy Reservoir and caused PG&E to take lines out of service.

“PG&E did de-energize a power line at the request of the fire incident command to help ensure firefighter and public safety,” a PG&E spokesperson told TransmissionHub Aug. 26. “We do know the potential to de-energize other lines does exist, as the Rim Fire is only [15%] contained at this point.”

Further, the fire has caused physical damage to some PG&E facilities.

“There has been some damage to PG&E infrastructure; however, we cannot access the equipment to assess the damage at this time as it’s not yet safe for PG&E crews or firefighters,” the spokesperson said.

In addition, the fire burned approximately 12 miles of 230-kV transmission lines leading from the Holm and Kirkwook powerhouses on the Hetch Hetchy power system, forcing those San Francisco Public Utilities Commission’s (SFPUC) facilities out of service, an SFPUC spokesperson told TransmissionHub Aug. 26. Crews are performing a preliminary damage assessment but have no additional details about when those lines might be rebuilt and returned to service.

Meanwhile, the Moccasin powerhouse is still generating hydroelectric power. San Francisco is making up the difference by accessing power in an existing power bank and purchasing power on the open market, according to the SFPUC website.

The three powerhouses comprise the Hetch Hetchy Power system and have a total generating capacity of approximately 380 MW, the SFPUC spokesperson said. The Moccasin and Holm powerhouses have two generating units each, with total generation capacity of 100 MW and 160 MW, respectively. The Kirkwood powerhouse has three generating units with a combined capacity of approximately 120 MW. The power is transmitted to San Francisco along city-owned transmission lines and is distributed to the city’s municipal facilities and retail customers, retail city tenants, residences and businesses.

In declaring the state of emergency, Brown said the fires “have caused damage to electrical infrastructure serving the City and County of San Francisco, and … the San Francisco Public Utilities Commission has been forced to shut down transmission lines with the result that the City and County is affected by the wildfires in the County of Tuolumne and is likely to be further affected.”

The SFPUC provides hydroelectric and solar power to San Francisco’s municipal departments as well as retail drinking water and wastewater services to San Francisco, and wholesale water to three Bay Area counties.

The Rim Fire has destroyed at least 16 structures and caused one injury as it burned in the Stanislaus National Forest, Yosemite National Park, Bureau of Land Management and State responsibility land, according to an incident report.

While the California ISO (Cal-ISO) said the Rim Fire is not threatening the ISO’s high-voltage grid, a spokesperson said ISO officials are watching the Deer Fire, which is running parallel to the California AC Intertie, two 500-kV power lines that serve 15 Western states.

The Deer Fire, which was 45% contained as of midday Aug. 26, had burned more than 10,000 acres near Deer Creek in Tehama County, Calif., approximately 12 miles east of Los Molinos, Calif.

PG&E is a subsidiary of PG&E Corporation (NYSE:PCG)