California regulators on Tuesday ordered Pacific Gas and Electric Co. (PG&E) to keep its Line 147 transmission pipeline lateral closed until staff can verify that the 24-inch diameter, 3.8-mile pipe that runs through San Carlos south of San Francisco is safe.

The California Public Utility Commission (CPUC) investigation by the Safety and Enforcement Division will determine whether "any immediate safety concerns are posed by the pipeline." A California Superior Court judge ordered PG&E to shut the line (see Daily GPIOct. 9). PG&E has asked the court to vacate its temporary injunction, citing California law that gives the CPUC exclusive jurisdiction in gas pipeline matters.

PG&E maintains the line has been inspected and its safety validated.

CPUC Commissioner Mike Florio also ordered PG&E to submit by Friday an updated safety certification for Line 147, which would incorporate any new information about Line 147's integrity and the safe operation of the line. Regulators said the latest investigation will result in public findings and required corrective action, if necessary, along with citations for any violations of law or regulation. "PG&E is not authorized to re-energize the pipeline until the investigation is complete and the CPUC staff determines the line may be operated safely," a spokesperson said.

PG&E said it will validate that it has completed safety related work on Line 147 in San Mateo communities, where San Carlos is, that has included verifying records and pressurizing the line with high-pressure water (hydrostatic testing) to confirm the pipeline's integrity, along with foot and air checks of the line.

"Customers in these communities can be assured that Line 147 is safe, and we look forward to the opportunity to document all the work that has gone into maintaining and operating this line safely," said Executive Vice President Nick Stavropoulos, who is responsible for the natural gas system. The 20- and 24-inch diameter segments that make up the short lateral connecting larger north-south transmission pipelines need to be checked to ensure they are available for service in the upcoming winter heating season, he added.

Florio said the CPUC is equally committed to ensuring that PG&E is "operating pipelines safely; we will not compromise safety."

As part of PG&E's safety/maintenance work last October, a leak was found on Line 147 and a contractor subsequently discovered discrepancies in the original information supporting the pipeline's maximum allowable operating pressure (MAOP) and the physical characteristics of the line. The information was reported to the CPUC (see Daily GPISept. 6). According to the utility, it removed the section of Line 147 where the leak occurred and determined through mechanical and metallurgical testing that the leak did not occur on a weld.

"There was no evidence of crack growth during service or hydro testing detected," PG&E said. In addition, Line 147 in the past two years has been MAOP validated, had its integrity confirmed, had a new 20-inch valve installed to allow stoppage quickly of the lateral's gas flow if necessary, and has been part of regular maintenance include a leak survey this past April.