Federal officials investigating the pipeline explosion that burned five buildings in San Francisco last week say it’s not the first time that crews at Pacific Gas and Electric Co. took several hours to cut off gas lines feeding large fires.
In at least four other pipeline fires in Northern California, PG&E crews took between 95 minutes and more than nine hours to shut off the gas, according to Jennifer Homendy, a National Transportation Safety Board member.
Such delays can mean that fires burn longer, potentially causing more damage to property and even the loss of life.
“We’ve had a number of recommendations. We’ve issued a number of studies on the need to shut down the flow of gas — quickly — to minimize impact,” Homendy said Saturday at a news conference at the site of last week’s pipeline fire in the Inner Richmond District.
PG&E officials have said that shutting off gas lines in accordance with state guidelines can require hand digging that takes time, as they say was the case in the recent explosion.
On Wednesday, PG&E took just over two hours to shut off gas that was fueling the blaze at Geary Boulevard and Parker Avenue. Earlier in the day, contract crews working for Verizon dug into the street and punctured a PG&E gas line, causing flames to shoot 40 feet into the air. Five residential and commercial buildings burned, including the popular Hong Kong Lounge II restaurant.
Nobody was injured, but federal officials said early in their investigation that they are concerned about how long it took utility workers to cut the gas. The NTSB routinely investigates transportation incidents including plane crashes and major vehicle collisions as well as pipeline explosions.
Homendy said the longest it has taken PG&E to cut off gas in a fire was nine hours and 10 minutes on Aug. 25, 1981. A PG&E contractor ruptured a 16-inch natural-gas main in San Francisco’s Financial District, according to a NTSB report.
After the incident, officials made “several recommendations” to PG&E, including to “train and equip company personnel who respond to emergency conditions in the operation of emergency shutdown valves,” according to the report.
In another incident in 2008, it took crews two hours and 47 minutes to shut off gas after a pipeline exploded on Christmas Eve outside a home in Rancho Cordova (Sacramento County), Homendy said.
In the destructive 2010 pipeline explosion in San Bruno, which killed eight people, crews took 95 minutes, she said.
The NTSB has not given utility companies a specific timeline for when gas flows should be shut off in the event of a fire. But Homendy said officials have repeatedly “stated that it needs to be a rapid shutdown.”
The investigators want to know whether PG&E heeded the safety board’s past recommendations for improved response.
PG&E officials have said that on Wednesday they could not have remotely shut off the gas because distribution lines like the one that ruptured do not have such capability.
Utility crews manually shut off the gas at six valves during the fire, according to PG&E. A company official said Wednesday that workers had to dig through asphalt to reach the valves, though on Saturday federal investigators said the six valves were located at street level and were not paved over. Homendy said PG&E turned the valves off and also dug “into their pipe” to clamp down on the broken gas line to stop the flow.
PG&E representatives said Saturday they could not immediately address the safety board’s claims, but sought to clarify the company’s actions during the fire.
“The planning team determined that these six valves were the best way to shut off gas without losing (service) to thousands of additional customers,” a PG&E representative said in an email.
Federal officials expect to release a preliminary report on the explosion within the next 10 to 14 days. A final report will follow.