RICHMOND -- A "flash fire" was extinguished about 10 minutes before a massive blaze erupted Aug. 6 at Chevron's refinery here, the company revealed in a 30-day report on the accident that it submitted to Contra Costa County officials Wednesday.
The revelation of the flash fire, which was not publicly known previously, is crucial to the investigation into the blaze caused by a leaking 8-inch pipe, said Contra Costa County Hazardous Materials Chief Randy Sawyer.
"There was a small fire that their fire department put out very quickly," Sawyer said. "That was a flash and warning in itself. What's key is to understand the thinking and decisions made in the three minutes between the little fire and the pipe failure."
Chevron's report also raised questions about the composition of a white cloud that formed minutes before a leaking pipe sparked the large fire. "A significant amount of water was being applied on scene and considerable steam was created," the report states. "Because the white cloud did not ignite, we have questions about its composition."
It was not immediately clear whether Chevron was referring to the vapor cloud that investigators with the U.S. Chemical Safety Board have said ignited the fire.
But Chevron spokeswoman Melissa Ritchie said late Wednesday early speculation by investigatory agencies into the cloud and the ignition source may have been premature.
"We have experts working on modeling the cloud
Between three and six minutes after the small flash fire was extinguished at 6:22 p.m., the crude unit was shut down when a leak from an 8-inch diesel oil pipe abruptly increased, Chevron said in the report.
The seven-page report highlighted several key areas of inquiry, including air-quality data, a timeline of the incident and emergency-response actions.
Chevron provided the following timeline of events that led to the fire:
Other new information in the report includes news that Chevron conducted monitoring for potential air contaminants at 19 locations in nearby communities on the night of Aug. 6.
"Our results were similar to (the Bay Area Air Quality Management District), with all concentrations below the reference exposure levels," according to Chevron, which also noted that it, like the air district, did not get readings of particulates, which public health officials believe played a major role in sending people to area hospitals.
The report noted that a "reportable quantity"of sulfur dioxide was released from the fire and flaring associated with the fire.
Chevron will provide updates every 30 days as the investigation continues, per city and county regulations, Sawyer said.
Another public meeting is scheduled for 6 p.m. Sept. 24 at the Richmond Memorial Auditorium, where investigators and local officials will update the public and take questions.
At least five agencies, including the Chemical Safety Board, Environmental Protection Agency and the state Division Occupational Safety and Health, are conducting a joint probe into the Aug. 6 fire.
"What happened between 6:22 p.m. and 6:25 p.m., that's a key question," Sawyer said.