Environmental groups are calling for increased scrutiny of California’s oil and gas industry after learning that more than 50 million gallons of crude oil flowed out of the ground in an uncontrolled release near a Chevron facility in Kern County over the last 16 years.

Over the weekend the state Division of Oil, Gas and Geothermal Resources, or DOGGR, issued a notice of violation against the San Ramon-based oil company, ordering it to stop uncontrolled surface releases at a site in the Cymric oil field that began flowing in March 2003.

The flows at the site, and at others nearby, have apparently been triggered by Chevron’s steam injection operations — a method used to free oil trapped in underground rock formations — in the Cymric field.

“It’s shocking and utterly unacceptable that California oil regulators did nothing for years as the industry spilled millions of gallons of oil,” said Hollin Kretzmann, a staff attorney at the Center for Biological Diversity.

Kretzmann is calling on Gov. Gavin Newsom to order an outside investigation into the releases.

“It’s the predictable result of lax rules and a regulator unwilling to protect the public from the dangers of oil and gas. We can’t trust any investigation by DOGGR,” Kretzmann said.

A Kern County environmental activist said on Tuesday the episode, involving what regulators and industry call “surface expressions,” goes beyond regulators failing to do their job.

“This isn’t negligence. This is a cover-up,” said Gustavo Aguirre Jr., a Bakersfield project coordinator with the Central California Environmental Justice Network. “Negligence can’t explain 16 years of failing to tell a community what’s happening or doing something to stop it.”

Aguirre also criticized calling the uncontrolled releases “surface expressions,” a term he said obscures damage caused by oil spills.

“It is a nonsense word used to diminish the environmental mess it is,” he said. “If ‘surface expressions’ aren’t oil spills, let’s put some surface expressions in the middle of San Francisco County or Los Angeles County or Orange County and see how much locals use that term.”

Environmental groups have said the surface expressions and uncontrolled crude oil releases pose threats to workers, wildlife and water quality, and note that the incidents have taken place fewer than 5 miles from the nearest town, McKittrick, and agricultural operations. Chevron maintains the releases have had no impact on personnel, groundwater, surface water, wildlife or agriculture.

State regulators were aware of similar past releases but did not take action when they occurred.

Chevron spokeswoman Veronica Flores-Paniagua said the company made government officials aware of the spill at a site called Gauge Setting 5, or GS-5.

“Over the years, the appropriate regulatory agencies have been consulted regarding the seep and have been involved at all steps of the process in handling GS-5 fluids,” Flores-Paniagua said.

Briana Mordick, a senior scientist at the Natural Resources Defense Council, said the state should conduct a broad study of surface expressions in California that should focus not just on the massive GS-5 release but on the causes and consequences of the flows and ways to prevent them.

“Surface expressions have been an issue with oil and gas production in California for a long time. For most of that time, it was considered part of doing the business of getting the oil out of the ground,” Mordick said.

“This is a sign of poor and sloppy practices. It shouldn’t be allowed to continue,” she added.

DOGGR officials say the enforcement actions were prompted by a regulation that took effect in April, banning surface expressions.

“Underground injection projects shall not result in any surface expression,” the new rules state.

Well operators are now tasked with developing plans to prevent the releases. They are required to monitor and contain the flows and must report them to state regulators.

The uncontrolled releases gained attention in recent months after one began one near a damaged and abandoned Chevron well that dumped about 400,000 gallons of oil into a dry creek bed.

DOGGR issued two notices of violation against the company in connection with those releases, which began May 10 and ended earlier this month at a site called 1Y.

Over the weekend the agency issued a violation notice against Chevron for a a rapidly growing new spill near the GS-5 and 1Y sites.

A spokesman for the Department of Conservation, which oversees DOGGR, referred questions about the call for an independent investigation into the 16-year-long Chevron surface flows to Gov. Newsom’s office. The governor’s office directed questions about the issue to the California Natural Resources Agency, which runs the Department of Conservation.

The agency’s secretary, Wade Crowfoot, issued a statement emphasizing that DOGGR recently strengthened its regulations on the oil releases.

“All surface expressions are now prohibited. We are committed to ensuring maximum oversight and enforcement, and we will be consulting with independent experts as we continue to strengthen this oversight,” Crowfoot said.

DOGGR had previously said that it is launching an investigation into the Cymric oil field, a probe it says will be aided by independent experts, including staff from Lawrence Livermore and Lawrence Berkeley national laboratories.

Surface expressions are rare and do not occur under normal operations, according to Christine Ehlig-Economides, a professor of petroleum engineering at the University of Houston.

But in the case of the flows at site GS-5, Chevron has built infrastructure that allows it to direct flows from surface expressions to be collected for shipment and processing.

“We routinely collect the fluid from that seep into an engineered surface collection facility and then remove it by either pumping into a pipeline or vacuum truck for process and handling,” Flores-Paniagua said.