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January 21, 2011

A government investigation into a gas pipe explosion last September that caused the death of eight people and destroyed 37 homes in a California neighborhood has found weld defects in pipeline recovered from the site.

The National Transportation Safety Board (NTSB) has released a report on the September 9, 2010 incident in which a 30-inch pipeline ruptured and later exploded in San Bruno, CA. The rupture left a crater 26 feet wide by 72 feet long. In total, the incident killed eight people, injured more than 50 people, destroyed 37 homes and damaged eight more.

Pacific Gas & Electric operates the pipeline. Shortly before the incident, the company was working on their uninterruptable power supply at a terminal some 39 miles away, which caused a fluctuation in the pressure in the pipeline.

USA Today reports that in dozens of instances, welds on the pipe were inadequate and poorly done. The thickness of the steel of the pipe was also too thin to meet standards in 1956, when first installed.

The NTSB also found discrepancy in PG&E records about the affected pipe, having noted it as a seamless pipe, when in fact it was of longitudinal seam-welded pipe. This type of record keeping error could cause the operator to operate the pipeline at a higher pressure than the pipe was built to withstand.

The NTSB issued three safety recommendations to PG&E, two of which the agency classified as urgent, asking the utility operator to do the following:

1) Conduct an intensive records search to identify all the gas transmission lines that had not previously undergone a testing regimen designed to validate a safe operating pressure (urgent recommendation);

2) Determine the maximum operating pressure based on the weakest section of pipeline or component identified in the records search referenced above (urgent recommendation); and

3) If unable to validate a safe operating pressure through the methods described above, determine a safe operating pressure by a specified testing regimen.

The NTSB is also concerned that other pipeline operators may have discrepancies in their records that could potentially compromise the safe operation of pipelines throughout the United States.

“While it may seem like a small paperwork error, if companies are basing operating pressures on inadequate or erroneous information contained in their records, safety may be compromised,” said NTSB Chairman Deborah A.P. Hersman. “We believe this safety-critical issue needs to be examined carefully to ensure that operators are accurately gauging their risk and that pipelines are being operated at pressures no higher than that for which they were built to withstand.”

The NTSB also made urgent recommendations to the California Public Utilities Commission (CPUC), which regulates PG&E’s pipeline operations as well as all intrastate pipeline operations within California, asking CPUC to:

1) ensure that PG&E "aggressively and diligently" search documents and records to determine which pipeline segments had not previously gone through a testing regimen to determine a safe operating pressure

2) provide oversight of any testing conducted by PG&E if the document and records search cannot be satisfactorily completed.

3) immediately inform California intrastate natural gas transmission operators of the circumstances of the San Bruno accident so these operators can likewise proactively implement any corrective measures for their pipeline systems.

“This accident has exposed issues that merit further attention and have implications for the pipeline infrastructure throughout the country,” said Chairman Hersman.

The NTSB is holding a public hearing on the investigation on March 1-2, 2011 at the NTSB’s Board Room and Conference Center, 429 L’Enfant Plaza, S.W., Washington, D.C. The hearing is open to the public and free with no reservation required. The NTSB will publish and agenda listing technical witnesses in the middle of February. The hearing can also be viewed via webcast at

“Today’s NTSB findings indicate there were faulty welds on the ruptured pipeline installed in 1956,” said Congresswoman Jackie Speier (D-San Francisco/San Mateo). “ I am profoundly disturbed by what I read today. Over the past several months experts have told me that welding flaws are detectable. We know that PG&E believed this pipe was seamless and that in 54 years it never once inspected the condition of the welds. The loss of life might have been prevented if PG&E had properly identified the risks it had underground in the Glenview neighborhood. The utility will have to answer for eight deaths, the suffering of burn victims and 38 destroyed homes.”

In response to the release of the NTSB report, PG&E released a statement from PG&E President Chris Johns

“Public safety is PG&E’s highest responsibility and highest priority,” said Johns. “With that as our focus, all pipelines in PG&E’s system that are of a size and vintage similar to the line in San Bruno are continuing to operate at pressures that have been reduced by 20 percent—a measure that builds a significant additional margin of safety into our current operating conditions.”

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