Fed Agencies Find Uneven Pipe Pressure Before San Bruno Explosion

By Published On: November 14, 2010

Shortly before a Pacific Gas & Electric natural gas pipeline exploded in San Bruno Sept. 9, the valve regulating the pressure malfunctioned, causing fluctuations in the pipeline pressure, according to a preliminary report by the federal agency investigating the matter. “Because of this anomaly, the electronic signal to the regulating line for Line 132 was lost,” reveals a National Transportation Safety Board Nov. 4 report. The pressure fluctuated between 390 pounds per square inch and 289 psig downstream of the rupture, between 5:45 PM and 6:11 PM, at the time of the accident. “The numbers are not wildly alarming,” said Mike Florio, The Utility Reform Network senior attorney. He noted the fluctuations “could be indicative of something else.” The Division of Ratepayer Advocates concurred. The pressure fluctuations at this time are not a significant concern but may point to a “potential issue,” added David Ashuckian, DRA deputy director of energy.

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