California orders intensified inspections of PG&E’s natural gas pipelines

State regulators Thursday ordered intensified inspections of natural gas pipelines operated by Northern California utility giant Pacific Gas & Electric, two days after federal investigators raised questions about seam welds in a line that exploded in a deadly inferno in September.

California Public Utilities Commission Executive Director Paul Clanon issued the order, citing a new National Transportation Safety Board finding that welds were inconsistent on the transmission line that ruptured in San Bruno, killing eight and destroying dozens of homes.

The PUC directive calls for internal, X-ray or liquid pressure tests to ensure the integrity of lines not previously examined that are similar in size and age to the pipeline that blew. That line was 30 inches in diameter and more than half a century old. The utility also is required to drop pressure in such lines until the inspections are completed.

PG&E said two large gas supply lines in the East Bay, one from Oakland to Fremont and another from Fremont to Milpitas, are affected. Immediate steps are being taken to comply with the pressure reductions, Vice President Kirk Johnson said.

“As part of our commitment to reassuring our customers, PG&E has been examining other pipelines of similar size and vintage to the segments in San Bruno to determine whether pressure could be reduced without impacting our customers,” he said. Pressure reductions in the line south of Oakland began last week, he said.

It was not immediately clear when and how the inspections would be completed, PG&E spokesman Denny Boyles said.

Investigators found the San Bruno line had some seams that were welded only on the outside and others that were welded on both the inside and outside. The agency said it was looking into the reasons for the variances. But it stressed that the cause of the Sept. 9 blast in the hillside suburban community south of San Francisco remains under investigation.

The incident, which ignited a firestorm that burned down 37 homes and damaged 18 others, is one of the worst gas pipeline disasters in recent U.S. history. PG&E has reported nearly $250 million in property damage, personal injury and other costs tied to the tragedy.

The NTSB also disclosed this week that it found discrepancies in PG&E records on how the San Bruno line was built. Surveys and charts showed pipe sections were seamless steel. But after the explosion, which blew a 28-foot section of pipe out of the ground, it became clear that some sections were constructed of steel that was formed into a circle and welded. PG&E acknowledged the discrepancy is serious and said it is conducting an “exhaustive” review of the matter.

rich.connell@latimes.com