SAN FRANCISCO (AP) — An audit of Pacific Gas and Electric Co. pipelines that was performed four months before September’s deadly explosion near San Francisco suggests the utility took shortcuts during its inspections of its high-pressure natural gas lines.

The San Francisco Chronicle reports that the audit, conducted in May, was performed to determine how well PG&E was complying with a 2002 federal law requiring inspections of all natural gas transmission pipelines in urban areas.

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In an article in its Sunday edition, the newspaper said the audit it obtained under the Federal Freedom of Information Act, was conducted by four California Public Utilities Commission inspectors.

The Chronicle reports that the utility had used a method called direct assessment on about three-fourths of the gas pipeline mileage tested so far, including the section of pipeline in San Bruno that later exploded.

The method of testing involves running an electric current through a pipeline and having workers on the ground monitor for indications of weakness. Workers then dig holes along the line to verify the findings.

But the newspaper said federal law allows two other main types of inspections — high-pressure water testing and ultrasonic testing by an automated device known as a smart pig, or pipeline inspection gauge.

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Both are approved for detecting weak welds, while direct assessment is not.

Because of direct assessment’s limitations, under federal law PG&E must rule out the risk of weld failure on a pipe before it performs that type of inspection.

The method cannot detect some problems in pipelines, including weakness in welds, according to the Chronicle.

An interim report by the National Transportation Safety Board on the blast, released last week, said PG&E had submitted documents showing it was unaware that the pipeline even had the type of welds that investigators are now examining in their search for a cause for the explosion.

The utility released a 34-page report Thursday defending the method of inspections and disputing some of the findings in the audit.

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PG&E spokesman J.D. Guidi told The Associated Press on Sunday that he did not have the information on the audit and was not authorized to speak on the topic.
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