Federal investigators are grilling PG&E officials Tuesday morning on the company’s response to the Sept. 9 gas pipeline explosion in San Bruno, its risk management programs, and the impact automatic or remote shut-off valves could have had on reducing the damage.
In the first day of National Transportation Safety Board hearings into the incident, federal officials peppered a PG&E risk management official with questions about whether the valves could have helped in the disaster, which killed eight people.
PG&E Senior Consulting Gas Engineer Chih-hung Lee was questioned about a 2006 internal memo released Tuesday in which he wrote that using automatic or remote shutoff valves in a high-consequence area has “little or no effect on increasing human safety or protecting properties.”
Lee testified that he based the memo on industry studies stating that most of the damage from a pipeline rupture happens shortly after a break.
It took PG&E workers 89 minutes from the time of the San Bruno explosion to close manual valves and stop the flow of the gas.
Investigator Bob Trainor asked how much more quickly the gas could have been shut off if remote or automatic shut-off valves had been in place near San Bruno.
Lee avoided directly answering, but conceded it would likely take less than 30 minutes for a remote or automatic valve to close.
Asked by Trainor whether the impact to the community would be greater with the longer release of gas, Lee replied, “I don’t know. According to the industry study most of the damage happens within a very short period of time.”
“Would it have made a difference to the community of San Bruno if firefighters had been able to get into that scene in 15 minutes as opposed to 90 minutes?” Trainor asked.
“I wasn’t involved in the case study,” Lee replied. “I don’t know.”
NTSB investigators drew a contrast to a 1999 report from the U.S. Department of Transportation, which found remote shut-off valves can help “in reducing the risk from certain ruptured pipelines and thereby minimizing the consequences of certain gas pipeline ruptures.”
“At many locations, there is significant risk as long as gas is being supplied to a rupture site, and operators lack the ability to quickly close existing manual valves,” according to the department’s report. “Any fire would be of greater intensity and would have greater potential for damaging surrounding infrastructure if it is constantly replenished with gas. The degree of disruption in heavily populated and commercial areas would be in direct proportion to the duration of the fire.”
Lee said his report was based on only industry studies.
PG&E Senior Vice President Edward Salas then jumped in, saying the utility could have activated such valves if they had been in place, but said it’s not yet clear what impact that would have had on reducing damage.
Check back throughout the day for the latest updates.
Watch the hearing online here.