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Twists In The San Bruno Saga
The search for the cause of the San Bruno gas pipeline explosion in 2009 that killed eight people has taken a new twist. On June 9, the California Public Utilities Commission issued a report from their hand-picked Independent Review Panel. This was a group the CPUC assembled ostensibly to get to the bottom of the San Bruno explosion.
That report was critical of a pipe bursting project that crossed the 30-inch PG&E gas pipeline about two years before the explosion. Fortunately for the pipe bursting industry, an expert had the integrity to change his mind when presented with relevant facts and has now drawn other conclusions that do not include bursting.
Initially, the CPUC’s Review Panel said that the pipe bursting project “most likely” caused increased stress on the PG&E gas line and weakened faulty seam welds by causing “earth shaking,” and somehow two years later caused the explosion.
However, the National Transportation Safety Board’s (NTSB) preliminary report did not indicate that pipe bursting could have caused the welds to crack to the point of explosion. Rather, the NTSB cites failure of the seam welds (more than 150) as the most likely cause.
The CPUC admits that determining the official cause of the steel gas pipe explosion is the responsibility of the NTSB. That report is due sometime in the fall. However, the CPUC believed it still important to authorize their own study (read politically astute) and release it before the NTSB’s findings are made public. The NTSB is still reviewing data before their final report is issued.
For the CPUC, the report’s credibility collapsed in late June when the principal expert that served on the CPUC panel, Robert Nickell, changed his mind about the cause of the pipeline failure once he had an opportunity to review additional data provided by PG&E.
Nickell said that information contained in thousands of PG&E documents released in mid-June made him reconsider his earlier conclusion. He said the revelation that PG&E normally operated the pipeline at pressures ranging from 125 to 350 psi could definitely have caused the faulty seam welds to fail and result in the explosion. Initially, Nickell said, the state panel assumed that PG&E had operated the line with a narrow range of 350 to 400 psi. That type of fluctuation wouldn’t have caused enough stress to cause the failure of a faulty weld. His new conclusions seemed consistent with the preliminary NTSB findings.