Report: Gas leaking into idled flare system caused Richmond’s rotten egg smell

Chevron says hydrogen sulfide-containing hydrocarbon gas leaked into part of its Richmond refinery’s flare system, causing the rotten-egg odor that spread across Richmond last week.

The section of the flare system had been shut down and isolated for scheduled maintenance, according to a 72-hour report Chevron filed with Contra Costa Health. The company identified the likely source Friday.

Odor across Richmond and San Pablo traced to Chevron refinery

A smell drifted across Richmond and San Pablo Thursday night, with residents describing it as anything from rotten eggs and sulfur to sewage. Today, the Bay Area Air District traced the hydrogen sulfide odor to an area of the Chevron refinery just downwind of its flares. The district’s incident

Grandview IndependentSoren Hemmila

Chevron spokesperson Caitlin Powell said the company identified and isolated a path that allowed gas containing hydrogen sulfide to reach the flare.

“Crews took immediate steps to identify the failure and mitigate the release,” the 72-hour report says. “Chevron continues to monitor the system to make sure it stays isolated.”

According to the report, the released gas contained hydrogen sulfide and ammonia. Chevron believes the release exceeded the reportable quantity of 100 pounds per day for each substance, but the amounts are still being calculated. The refinery also reached the daily 500,000 standard cubic feet threshold for vent gas to a flare under Air District rules on October 22 and 23. A 30-day follow-up report will provide more detailed information.

Portable monitors measured hydrogen sulfide concentrations of up to 4 parts per million on refinery property. Chevron’s Castro Street monitor peaked at about 491 parts per billion.

In the North and East neighborhood, Bradley Scarborough posted on NextDoor that the smell came into his home even with everything shut.

“It penetrated my place. Windows and doors were closed. You could feel it breathing in,” Scarborough said. He called for the incident to be investigated and for consequences.

Desiree Hubbs said that she noticed the smell early in the evening and wasn’t sure where it was coming from.

“I’ve been smelling it really bad since around 5 p.m. I thought the rain might be causing it. And I even was thinking maybe since they’re doing all the work on the streets and doing pipe work and maybe that’s why it smells. I don’t know, but it sure does stink,” Hubbs wrote.

Chevron issued a Community Warning System alert at 12:19 a.m. Friday. The alert listed the release as beginning at 12:10 a.m., but the Air District began receiving odor complaints at 6:09 p.m. Thursday and said complaints and staff observations indicated the release began hours earlier.

Chevron apologized for the disruption and worry the odor caused and acknowledged residents’ questions about the source, notification timing, and air monitoring data. The company said it would share the results of its investigation and any steps taken to help prevent a similar incident.

Both Chevron’s and the Air District’s investigations are ongoing.