Officials with PG&E have reached their conclusion about what caused a natural-gas pipeline to explode in San Bruno last September. And they have concluded the event was not the utility’s fault.
Federal investigators asked PG&E, the agency that regulates it, the city of San Bruno and other parties to submit analyses about what caused and contributed to the San Bruno disaster, which took eight lives and decimated a neighborhood.
A document prepared by PG&E, filed with investigators in June and released this week completed a narrative that company officials have been advancing for months: that the pipeline explosion was caused by a 1954 manufacturing defect rather than any actions taken by the utility. PG&E officials concluded the utility-caused spike in natural-gas pressure that preceded the explosion “would not have damaged” a properly welded pipe, and that their emergency response was “timely and reasonable.”
In comparison, the city of San Bruno and safety officials with the California Public Utilities Commission cited factors such as PG&E’s poor record-keeping practices, its use of nonrigorous testing methods, decisions by its management, and the utility’s inadequate pipeline safety practices as possibly contributing to the disaster.
When asked why PG&E omitted such factors from its own narrative, utility spokesman Brian Swanson said the company has taken actions to improve its natural-gas system since the accident and acknowledged that its record-keeping practices “were not where they should be.”
Swanson also pointed to the introduction of PG&E’s 13-page assessment, in which the utility struck a humble tone.
“PG&E does not want the narrowness of this focus to suggest that it has not learned a broader lesson from this tragic accident,” the introduction stated.
Ultimately, however, the document identified the probable cause of the disaster as a poor weld along the pipeline that exploded, which it indicated was “completed at a mill by a manufacturer” and not PG&E.
The utility also concluded that pre-rupture actions of PG&E personnel “were timely and reasonable” and did not contribute to nor exacerbate the damage caused by the explosion.
Likewise, the document concluded that the company’s actions after the rupture on Sept. 9 were similarly “timely and reasonable.”
PG&E’s emergency response has been widely and acutely criticized, because the company was unable to shut off the gas flow for about 90 minutes after the rupture, leading to an expansion of the fire that consumed the Crestmoor neighborhood.
Mindy Spatt, a spokeswoman for The Utility Reform Network, said she was hardly surprised that PG&E would reject responsibility for the accident even after it issuing a public apology.
“This is why we have regulatory agencies, because it’s predictable that PG&E would say ‘not our fault,’” Spatt said.
“Consumers are much more interested in hearing what independent bodies conclude than they are in hearing what PG&E concludes.”
On June 17, PG&E filed a document with federal investigators about what it believes caused the San Bruno natural-gas pipeline rupture. These are the company’s major findings:
The probable cause of the rupture was a defective seam weld, which weakened over time before rupturing Sept. 9. That flawed seam was welded “at a mill by a manufacturer.”
Although problems with power at a Milpitas terminal did increase the pipeline’s pressure, it did not spike above the maximum allowed, and “would not have damaged an otherwise properly welded pipe.”
The actions by PG&E workers before the rupture were timely and reasonable and did not contribute to the rupture.
While PG&E “recognizes that the response in any emergency situation might be improved,” its workers’ actions after the disaster were “timely and reasonable and did not exacerbate the damage caused by the rupture or impede emergency response to the accident.”
More investigation must be done to know if there are any other contributing causes.
Source: National Transportation Safety Board