RICHMOND -- Although safety concerns continued to prevent them from full access to the site of last week's massive Chevron refinery fire, federal investigators on Tuesday said a key focus would be the company's decision last fall to not replace an aging pipe that apparently sparked the blaze.

While investigators interviewed about 50 witnesses and requested thousands of pages of documents from the energy giant in recent days, the pipe where the leak originated is still beyond reach.

"The site remains, at this point, hazardous to human entry," said Daniel Horowitz, the U.S. Chemical Safety Board's managing director, adding that investigators must where protective respiratory equipment because of lingering hydrocarbons and can get no closer than 10 feet from the mangled pipes because of questionable structural integrity.

The investigation stems from the Aug. 6 fire at the refinery, which occurred after workers discovered an aging pipe leaking flammable "gas oil," Horowitz said.

They waited about two hours before deciding to remove the pipe's fiberglass insulation while the unit was still processing crude, according to federal investigators, causing the leak to accelerate and then ignite. The fire spewed black smoke into the air and, as of Tuesday morning, had sent more than 9,000 people to area hospitals.

While five refinery workers were treated for minor injuries, more than a dozen narrowly escaped severe injuries or death in what the CSB has called a "near disaster" for refinery personnel.


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Tuesday's news conference outside the refinery shed some light on the direction of the investigation. The director of the CSB's Western Regional Office, Don Holmstrom, said it was important not to rush to conclusions or have "tunnel vision" when assessing the origins of the fire.

But when asked by reporters whether workers may have exacerbated the situation by removing the pipe's insulation, CSB officials said that decision and its aftermath was not the investigation's "primary focus."

Speculation has also swirled about the leaky 8-inch pipe and its maintenance schedule, and whether Chevron officials should have replaced the pipe last fall. A 12-inch pipe adjacent to the leaky pipe was reportedly replaced during maintenance after it was found to be corroded.

Horowitz said several times that the pipe, its condition and past maintenance was a "key line of investigation."

"We are very much interested in that," Horowitz said, referring to the decision to not replace the pipe, which he said occurred in November.

Chevron spokeswoman Melissa Ritchie would not comment on a report in the San Francisco Chronicle on Tuesday that the company initially designated the leaky pipe for replacement last fall before changing its mind and deeming it fit for five more years.

"It is premature to speculate on the cause of the fire," Ritchie wrote in an email. "The investigation is still in its early stages, and close-up inspections of the equipment cannot occur until the area where the fire occurred is deemed safe and secure."

Horowitz said investigators will remove and analyze the 8-inch pipe once the area is safe from both structural weakness and hydrocarbon exposure, which could take weeks. Horowitz said that key questions to be answered will be the thickness of the pipe's walls and its rate of corrosion in circulating extremely hot, flammable liquids.

Holmstrom stressed the peril that a still-undetermined number of employees were under Aug. 6, narrowly avoiding serious injury or death.

"They were enveloped by a vapor cloud that later ignited," Holmstrom said.

Holmstrom and Horowitz said Chevron officials have cooperated with the investigation process.

Community and labor groups are also monitoring the situation closely, particularly concerned with public health and worker safety.

"It was a pretty frightening and unnerving experience," said Jeff Clark, a field representative for Steelworkers Local 5, who represents about 600 operators and mechanics at the Richmond plant. "A very close call."

Having upward of 15 people caught in a vapor cloud would raise some questions as to why so many were essential to the work, he said. Employees who removed the insulation would have done so by hand, putting them within inches of the leak.

"In a situation where there's a loss of control of hydrocarbons, anyone that's not absolutely essential to that operation should be removed from the danger zone," he said. "So, you'd look at the 12 or so who were there. Why were they there? Should they have been there?"

Communities for a Better Environment, a pollution watchdog group, said Tuesday that Contra Costa County and Richmond have agreed to measures to keep the public informed about the investigation.

Greg Karras, senior scientist with the group, said Richmond city officials have agreed to hire an independent expert to monitor the investigations and explain technical information about it to the public.

Staff writers Denis Cuff and Matthias Gafni contributed to this story. Contact Robert Rogers at 510-262-2726 or rrogers@bayareanewsgroup.com. Follow him at Twitter.com/roberthrogers