Chevron Says Flawed Electrical Diagram Triggered Major Flaring Incident

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View from a rocky shoreline across the bay to a refinery spewing a massive plume of smoke.
Flaring at Chevron's Richmond refinery as seen from Berkeley's César Chávez Park on Nov. 2, 2020. (Queena Kim/KQED)

Chevron says an incorrectly labeled electrical diagram caused a power outage at its Richmond refinery last November and led to a series of flaring incidents and the release of more than 100,000 pounds of toxic gases.

One of California's top air quality health experts says the electrical incident, which the company disclosed in a report to regional air regulators, amounts to a "Chevron screw-up" that could have triggered serious health effects for people living downwind of the refinery.

The series of events started Nov. 2, when the plant belched out a plume of black smoke that could be seen throughout the central Bay Area. Hours after the flaring began, Chevron said a power disruption to part of the massive facility had triggered the incident.

Refinery officials provided details of the mistake and subsequent problems at the refinery in a series of reports filed earlier this month with the Bay Area Air Quality Management District.

The company says the issues began as workers tested a communication system that uses acoustic signals to control valves at the plant. During the test, circuit breakers at two electrical substations tripped, causing a power outage to part of the refinery.

"This was due to an incorrectly labeled drawing that did not match the circuitry in the field," one of Chevron's reports says.

"It sounds like a routine maintenance check that went south," said Eric Smith, a Tulane University professor who specializes in refinery operations, and who read the company's reports.

The Nov. 2 outage led to gases being routed through several of the refinery's flares. The initial malfunction also affected other parts of the facility's operations, leading to further flaring over the following week.

"That sounds like a Chevron screw-up that should not have been beyond the reasonable control of Chevron," said John Balmes, a professor of medicine at UCSF who sits on the California Air Resources Board.

"It seems like it was a serious incident that led to a release of a large volume of climate forcing and toxic gases," Balmes said. "If an asthmatic patient was outside downwind from the SO2 (sulfur dioxide) release, they could have experienced an asthma attack."

Hours after the flaring started, the air district said it had received 20 complaints from people nearby who said they could see the smoke or smell an odor coming from the plant.

The Nov. 2 flaring operation lasted 17 hours, into the early hours of Nov. 3.


When the refinery began starting up parts of its hydrogen plant that afternoon, it sent more methane and non-methane hydrocarbons through its flares between Nov. 3 and Nov. 8.

On Nov. 9, as the refinery restarted several hydroprocessing units, its flare gas recovery system got overloaded and sent another round of pollutants, including sulfur dioxide, into the air.

In all, more than 100,000 pounds of sulfur dioxide, 8,000 pounds of methane and 9,000 pounds of non-methane hydrocarbons (this includes chemicals like propane and benzene, among others) were released in the three incidents, the company's reports say.

The amount of sulfur dioxide released following the early November outage was nearly equal to the total amount of the pollutant the refinery released in flaring operations in all of 2019, according to public data from the air district. It's also tens of thousands of pounds more than the total amount of sulfur dioxide that all other Bay Area refineries released during flaring that same year.

"That was a lot of very lengthy flaring," said Matt Krogh, oil and gas campaign director for the environmental group "Chevron should have better systems in place."

"If it was an emergency, it was a preventable emergency," Krogh said. "Chevron has been flaring excessively for years. Why can't they get a handle on what's flowing through their processing units?"

In 2018 and 2019, Chevron's Richmond refinery experienced a spike in flaring incidents.

Sulfur dioxide is a common chemical released during flaring operations, which are described by air regulators and the industry as safety techniques used to dispose of hydrocarbon gases safely. (You can learn more about refinery flaring on this air district webpage.)

Another environmental advocate, Matt Renner, who lives in Richmond and has consistently criticized the refinery for such episodes, said the November flaring raises significant concerns.

"This plant is not being operated safely," Renner said. "The fact that they admit that their own documentation is wrong and that they don't have procedures for restarting safely after an unplanned outage begs the question: If Chevron doesn't know how to operate this plant safely, who does?"

A Chevron representative declined to offer more specifics about the sequence of events that led to the mistaken circuitry drawings and outage but emphasized that the company has worked to reduce flaring at its refineries around the world and in Richmond.

"With the exception of flaring that occurred in 2019 as part of overcoming the challenges of integrating $1 billion of new, modernized equipment, Richmond has reduced the frequency and volume of flaring events over the last 10 years. We continue to focus efforts to both reduce flaring and facility down time," said Chevron spokeswoman Linsi Crain. 

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The company told the air district that it has updated diagrams for the electrical substations involved in the outage and is working on other changes to prevent a repeat.

"Chevron identified and employed preventative measures to protect against this type of power loss in the future," Crain said. "Similar to protections against mechanical failures, Chevron employs multiple layers of safeguards and systems to reduce human error."

"Importantly, air monitoring data during the incidents in question demonstrated no exceedances above health-based standards for the chemicals monitored," Crain said.

November's flaring incident is under investigation by the air district but not by the hazardous materials program at Contra Costa County Public Health Services. Officials at the health agency did not seek a 72-hour report on the incident.

The flaring operations were not deemed to be a major chemical accident or release so the refinery is not required by county officials to perform a root-cause analysis, according to Matt Kaufmann, director of the county's hazardous materials programs.

The November case was the second significant incident at the refinery in a matter of six months.

On Aug. 14, in the midst of a Bay Area heat wave, Chevron had a malfunction tied to the weather. According to a causal flare report filed with the air district, after it reached 90 degrees that day, one of the facility's fire suppression systems mistakenly activated. A steam unit tripped offline, causing pressure problems that prompted the refinery to send gas to its flares.

For comparison, that flaring led to the release of close to 630 pounds of sulfur dioxide.

On Jan. 16, there was another malfunction at the refinery. Other than Chevron's description of a "unit upset" at the facility, details about that incident have not been released. A causal report for that flaring operation is due by the end of March.

Earlier this month, a ruptured pipeline at Chevron's Long Wharf led to the release of up to 750 gallons of low sulfur diesel mixed with water into San Francisco Bay. That triggered a health advisory, the closure of a local beach, several investigations, a lawsuit from a local fishing group and a hearing before the Richmond City Council.