Explosion sparks fire, chemical spill at Sonoma County geothermal plant near Cloverdale

Sonoma County officials are investigating what caused a transformer to explode and a fire to break out Saturday night at a geothermal power plant in The Geysers east of Cloverdale, not far from the energy facilities where October’s destructive Kincade fire started.

The extent of the damage from a fire that consumed a transformer and a generator, but didn’t harm any of the workers on site, is still being determined.

Fire crews from Cal Fire and Lake County responded to a thermal plant near Geysers Resort and Big Sulphur Creek roads about 10:55 p.m. after receiving reports that hazardous material was leaking due to an ongoing fire, said Cal Fire Capt. Cody Parks.

Hazardous material teams from Sonoma County and Santa Rosa were called in to evaluate the seeping chemical before suppression efforts could begin, he said.

“They wanted to make sure it wasn’t toxic and it wasn’t harmful to the crews,” Parks said of the leakage.

After specialists determined it was safe, firefighters extinguished the blaze using foam and water. They cleared the property by 4 a.m. Sunday.

Sonoma County fire inspector Charles Rivers identified the substance as mineral oil, which is often used as an electrical insulator in generators.

Rivers said the leaked mineral oil spread to a nearby generator, and the heat was so intense that the generator then ignited.

The generator leaked diesel fuel that also caught fire, Rivers said. No other structures or property were damaged.

Officials credited overnight rains and damp ground for helping keep the fire in check.

“It didn’t spread farther than that area,” Parks said. “It stayed contained within the commercial building.”

Cal Fire officials were unsure whose property caught fire. Calpine, the country’s largest geothermal and natural gas electricity provider, operates facilities in the area. A phone message left with Calpine was not immediately returned.

The Kincade fire, which burned nearly 78,000 acres during two weeks in late October and early November, is believed to have started when a PG&E transmission line failed near The Geysers, at another geothermal plant that is roughly 6 miles southeast of Saturday night’s incident.

“It’s within same general area, but not the specific origin area,” Parks said.

You can reach Staff Writer Yousef Baig at

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