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.
To put things in perspective:
• The old pipeline was held together from the day of installation with more than 150 seam welds so poorly done that they went only halfway through the pipe:
• PG&E’s inspector left the job site before the bursting project was completed and never reviewed the gas pipe before or after the pipe bursting project;
• There were more than 150 faulty seam welds in that area of the steel gas pipe dating back to 1956;
• PG&E had historically operated the pipeline in pressure ranges from 125 to 350 psi which in turn put constant stress on the faulty seam welds – stress that Nickell and other experts say could easily and most likely caused the explosion; and
• First and foremost, the pipe bursting contractor and city of San Bruno did nothing wrong. In fact, the contractor engaged precautionary measures due to the proximity of the gas line.
Thank goodness someone like Robert Nickell served on this state review panel. He had the scientific integrity to review new information and publically modify his earlier statements accordingly. A lesser person may not have had the professional and personal courage to dispute his own panel’s initial findings. Nickell apparently realizes the potential damaging impact of the panel’s earlier misguided conclusions. Blaming pipe bursting for the explosion could have had far-reach negative impacts for the entire industry.
We look forward to reviewing the NTSB’s final report. But it’s important to remember that with or without pipe bursting, this particular gas pipeline was going to fail.