PG&E records show pipeline that blew up had 33 previous leaks

In 2010, a massive deadly fire roared through a mostly residential neighborhood in San Bruno when a gas pipeline exploded. Pacific Gas and Electric Co. records in 2009 listed 33 past leaks with unknown causes on that same aging gas pipeline, a PG&E engineer told a federal court jury Friday. less In 2010, a massive deadly fire roared through a mostly residential neighborhood in San Bruno when a gas pipeline exploded. Pacific Gas and Electric Co. records in 2009 listed 33 past leaks with unknown causes ... more Photo: Paul Sakuma / Associated Press 2010 Photo: Paul Sakuma / Associated Press 2010 Image 1 of / 1 Caption Close PG&E records show pipeline that blew up had 33 previous leaks 1 / 1 Back to Gallery

Pacific Gas and Electric Co. records in 2009 listed 33 past leaks with unknown causes on the same aging gas pipeline that exploded in San Bruno in 2010, a PG&E engineer told a federal court jury Friday.

Called as a prosecution witness in PG&E’s trial on charges of criminal violations of pipeline-safety laws, David Aguiar testified that his job was to examine pipelines for external evidence of corrosion — a method that could not have detected internal welding defects that caused many leaks.

A flawed seam weld, on a line that company records had listed as seamless, ruptured in September 2010 in San Bruno, causing an explosion and fire that killed eight people and destroyed 38 homes. A subsequent federal investigation led to 12 felony charges that PG&E had failed to inspect and test its lines and keep accurate records, and a 13th charge that it had obstructed investigators by trying to conceal an alleged policy of exceeding legal limits on gas pressure in its pipelines.

Prosecutors contend PG&E sacrificed safety for profits by shunning high-pressure water testing of problematic gas lines in favor of cheaper detection methods, like the method used by Aguiar and his co-workers known as external corrosion direct assessment, or ECDA. He said he relies in part on the company’s computer database, and in part on staff reports, to identify areas that need inspection, and then checks to see whether pipes show signs of corrosion.

His account of PG&E’s response to a leak on another pipeline in 2006 appeared to illustrate the inspection system’s shortcomings. Aguiar, who has worked for PG&E since 1985, said he was asked to investigate the leak after it occurred, and concluded in a report in December 2008 that the cause was a weld failure that was unrelated to corrosion and could not have been spotted by ECDA.

When he told a supervisor, the supervisor replied, in an email displayed to the jury, that an inspection process that “walks right over active leaks” was “something I would not advertise too loudly.”

Aguiar replied by email that no one was “advertising” that ECDA could detect welding defects. The supervisor replied, in another message shown to the jury, “We are advertising that we’ve assessed the pipe and it’s fit for service. Failed girth welds are not minor.”

Prosecutors say PG&E didn’t reveal the gap in its inspections to federal regulators or the public.

Aguiar also said a November 2009 survey by his ECDA team recounted the history of the pipeline that runs from Milpitas to San Francisco. He said it had suffered 36 previous leaks — three from corrosion, the rest from unknown causes. That was the pipeline that ran through San Bruno, a fact that prosecutors and their witnesses aren’t allowed to mention, under orders from U.S. District Judge Thelton Henderson.

Asked by managers in 2009 about a recent leak in that pipeline in South San Francisco, Aguiar told them by email that “this seems to be happening more frequently,” most likely because of welding defects, but he would not describe it as a “systemic problem.”

Aguiar also summarized PG&E records of a 1988 leak on the same pipeline that required the removal of 12 feet of defective pipeline. The records contain no information on the cause of the leak, the type of weld, the year it was installed or the date it was repaired, Aguiar said.

The Chronicle has reported that other PG&E documents show the leak occurred in October 1988 near Crystal Springs Reservoir, in the Santa Cruz Mountains, and was caused by a “longitudinal weld defect,” the same flaw responsible for the San Bruno explosion. Experts told The Chronicle that those records, which were not turned over to federal regulators before the explosion, should have required PG&E to conduct high-pressure water testing that might have prevented the disaster.

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com Twitter: @egelko