Pacific Gas and Electric Co. knew of more than two dozen previous, unexplained leaks in one of its natural-gas pipelines when it certified that the pipe was free of seam-weld leaks months before it exploded, the San Francisco Chronicle reports.
PG&E workers recorded at least 26 leaks of unknown origin on the Milpitas-to-San Francisco pipeline from 1951 to 2009, according to a November 2009 report, the Chronicle reported Sunday (Oct. 23) after reviewing utility inspection reports and other documents.
100+ Leaks Unaccounted For
The Chronicle’s review of PG&E inspection reports for other lines in its urban gas system “found that a dozen had a total of more than 100 leaks that the company never accounted for,” the newspaper reported. “None, however, had more unexplained leaks in its history than Line 132.”
|A National Transportation Safety Board investigator cleans a fractured surface of a pipeline section that ruptured Sept. 9, 2010.|
At issue is the type of inspection method PG&E used on Line 132, the 30-inch-diameter pipe that catastrophically ruptured Sept. 9, 2010, in a residential area in San Bruno, CA. The 28-foot-long rupture produced a 72-by-26-foot crater, destroyed 38 homes, killed eight people, and injured many more.
PG&E records released after the disaster described the line as seamless when, in fact, it contained numerous welds. Now, the Chronicle reports, many of those previously undisclosed welds also had a history of leaks whose causes were never investigated.
And by law, such lines require high-pressure-water testing, not just corrosion inspection.
Evidence that PG&E knew of 26 unexplained leaks over 58 years was found on computer-generated survey forms included in a November 2009 inspection report, the Chronicle reported.
The report was created to certify that the line was free of seam-weld problems and thus appropriate for corrosion-only inspection, the newspaper said.
|NTSB reported that the pipeline asphalt coating was dripping and sagging in some areas.|
Such forms have spaces to note critical details on each leak, but none of the forms for the 26 leaks cited on the San Bruno line had a tracking number or other details to help find the original documentation.
In each case, the paper said, “the cause of the leak is shown simply as ‘unknown.’”
Another document in the same report “refers to 33 leaks that PG&E crews had found on the San Bruno line with ‘no causes given’” and no time frame noted, the newspaper said.
Yet another document referred to the cause of a 1998 leak on the same line as “unknown.” But the National Transportation Safety Board, which investigated the disaster, discovered after the blast “that PG&E had documentation listing the actual cause [of the 1998 leak] as a defective longitudinal seam weld,” the Chronicle reported.
“It is probable that additional longitudinal seam weld defects have remained in service since 1948,” NTSB found.
‘Cheaper, Less Burdensome’ Testing
Federal law required PG&E to consider previous longitudinal seam failures or leaks when it picked a pipe inspection method, but “there is no evidence the company ever found original documentation to rule out bad seam welds as a cause of any of the San Bruno line’s leaks,” the paper said.
“Instead, it relied on computerized records with scant information that were loaded onto a database starting in the 1990s.”
San Bruno Fire Department
|Flames billow over San Bruno, CA, after a natural-gas explosion killed eight people and leveled homes.|
“PG&E never conducted an inspection that could detect such [weld] problems before another flawed weld ruptured on the San Bruno line in September 2010,” the paper noted.
Had PG&E disclosed one seam weld leak, the utility “would have been required to check the San Bruno line for other such problems using high-pressure water—a test the company seldom used on any line,” the newspaper reported.
Instead, “PG&E inspected most of its lines, including the one in San Bruno, with a cheaper, less burdensome method best suited at finding corrosion.”
‘Integrity Management without Integrity’
NTSB concluded in August that PG&E was responsible for the disaster, citing what its chairwoman called “poor record keeping, inadequate inspection programs, and an integrity management program without integrity.”
The report found three main causes for the disaster:
• Use in the line of a “substandard and poorly welded pipe section with a visible seam weld flaw that, over time, grew to a critical size”;
• An “inadequate pipeline integrity management program, which failed to detect and repair or remove the defective pipe section”; and
• Exemptions granted to existing pipelines from the regulatory requirement for pressure testing, “which likely would have detected the installation defects.”
Earlier, NTSB also noted coatings irregularities along the ruptured line.
Even small pipeline leaks can lead to an explosion, Robert Bea, an engineering professor at UC Berkeley who has been following the San Bruno case, told the Chronicle.
“In that case, the standard of care is guilty until proven innocent: You stop operations and find out whether the condition is posing an unacceptable risk,” he said.
“You should have zero tolerance for leaks.”
‘Junked’ Pipe Denial
Last week, PG&E objected to state regulators' suggestion that the company installed “junked” pipe in its gas-transmission system in the 1940s and '50s, “saying its use of properly reconditioned pipe at the time was perfectly safe and challenging officials to prove otherwise,” the Chronicle reported.
A filing by the California Public Utilities Commission said regulators had found utility documents indicating that the company used “salvaged or junked” pipe decades ago on gas lines that are still in service.
In its response, PG&E attorneys wrote: “The reuse of salvaged (not 'junked,' as legal division's motion suggests) pipe was a common practice throughout the industry at least through the 1950s. Reused pipe would be cleaned, inspected, and, if in satisfactory condition, recoated prior to use.”