The newly revealed spill has been flowing off and on since May and has again stopped, Chevron spokeswoman Veronica Flores-Paniagua said. She and California officials said the spill is not near any waterway and has not significantly affected wildlife. The last flow was Tuesday.
Chevron reported that 794,000 gallons (about 3 million liters) of oil and water have leaked out of the ground where it uses steam injection to extract oil in the large Cymric Oil Field about 35 miles (56 kilometers) west of Bakersfield. The steam softens the thick crude so it can flow more readily and is a different process from fracking, which breaks up underground layers of rock.
The state has issued Chevron a notice of violation ordering it to stop steam injections around the spill. The company also increased its production of oil from wells in the area. Both actions are intended to relieve underground pressure that may be forcing the mix of oil and water to the surface.
Chevron will pay for the cleanup, though the state will oversee the process, said Steve Gonzalez, a spokesman for the California Department of Fish and Wildlife's Office of Spill Prevention and Response.
The cleanup and the investigation into what caused the oil flow were somewhat delayed as officials ensured there are no dangerous fumes or sinkholes that could trap workers or heavy equipment, he said.
"At this point, they have it dammed off and they're sucking it out, sucking the oil out," Gonzalez said.
Environmental groups said the Chevron spill is another sign of weakened regulations under an embattled California agency. Gov. Gavin Newsom this week fired the head of the state's oil and gas division over a recent increase in hydraulic fracturing permits and amid a conflict-of-interest investigation of other division employees.
The Last Chance Alliance, which opposes California's oil and gas industry, said the state's Division of Oil, Gas and Geothermal Resources adopted weaker restrictions on steam injection earlier this year, "making these operations even more dangerous."
The group said state regulators and the U.S. Environmental Protection Agency last year approved an exemption that removed protections from an aquifer in the Cymric Oil Field at the request of Chevron and other oil companies.
"California's industry-friendly oil regulator continues to provide about as much protection as a screen door on a submarine," Hollin Kretzmann, a senior attorney at the Center for Biological Diversity and member of the Last Chance Alliance, said in a statement.
Neither Chevron nor division spokesman Don Drysdale commented on the criticism.
About 70% of the fluid is water, Chevron said, meaning about 240,000 gallons (908,472 liters) of the mixture is oil.
The spill, which was first reported by KQED News, comes after a judge earlier this year fined Plains All American Pipeline nearly $3.35 million for causing what had been the worst California coastal spill in 25 years.
A corroded pipeline spilled 140,000 gallons (529,942 liters) of crude oil in 2015 onto Refugio State Beach in Santa Barbara County, northwest of Los Angeles, tarring popular beaches for miles, killing wildlife and harming tourism and fishing.
In 2007, the container ship Cosco Busan leaked nearly 54,000 gallons (204,406 liters) of heavy fuel oil into San Francisco Bay after the ship hit the San Francisco-Oakland Bay Bridge in thick fog.
The state's worst spill was the 1969 Santa Barbara oil spill that leaked at least 80,000 barrels of crude oil into the Santa Barbara Channel. Each barrel is 42 gallons (159 liters).
But the effect of this year's Chevron spill on birds and wildlife appears minimal, Gonzalez said. Chevron said the spill flowed into a dry stream bed, and Gonzalez noted that it is unlikely to rain anytime soon.
"There's no active waterway that it's nearby, so that's the good news," he said.