Pacific Gas and Electric Co. (PG&E) experienced leaks and a resulting fire in its two-inch diameter plastic distribution main at the end of last month. As a result, it is facing the prospect of stepping up surveying and maintenance of its 40,000-mile distribution pipeline system. The company’s transmission pipelines have been under scrutiny following a deadly explosion one year ago.

The Aug. 31 incident occurred at a 420-unit townhouse development on the South Bay Peninsula in Cupertino, CA, about 40 miles south of San Francisco in Silicon Valley. It involved a certain type of pre-1973 plastic pipe called “Aldyl-A,” made at the time by DuPont, a PG&E spokesperson told NGI Monday.

There were no injuries, but fire consumed one of the town homes. A PG&E crew was on the scene in 20 minutes, pinched off the leak and made repairs, but in surveying the mains serving the rest of the residential complex six other similar cracks were found in tees connecting service pipes to the main distribution pipeline feeding the complex.

As a result, PG&E is now planning to check all 1,200 miles of Aldyl-A plastic distribution main that it has in its system dating back to pre-1973. For the Cupertino town home complex it will replace all 6,000 feet of main and 424 service pipes connecting the individual units, the spokesperson said.

PG&E reported the incident to the California Public Utilities Commission (CPUC), which sent a representative to the scene last Thursday, a day after the incident. The San Francisco-based combination utility also was contacted by the National Transportation Safety Board (NTSB), which only a couple days earlier had released its final report on PG&E’s fatal San Bruno transmission pipeline rupture and explosion a year ago (see Daily GPI, Aug. 31).

NTSB had a few questions, but was not pursuing anything further on the distribution pipeline incident, said the PG&E spokesperson, who did not know what further action might be forthcoming from the CPUC. There is no current proposal from the state regulators for PG&E to address its distribution pipelines with the same scrutiny now being placed on transmission lines following San Bruno, which resulted in eight people being killed Sept. 9, 2010.

“What we found was that there was a crack in the ‘tee’ connecting the main pipeline to a service line,” the utility spokesperson said. Gas migrated back into the town home, and what ignited the fire was still unknown. PG&E is waiting for the local fire department to make a determination on that aspect of the incident.

“After the fire was put out we did a leak survey of the entire complex and found six other leaks in service links between the town homes and the distribution main,” said the spokesperson, who said the development was built in 1973. Over time that type of plastic pipe gets brittle, he said.

Under California law, leak surveys of distribution pipelines are required every five years, and the pipelines serving the Cupertino complex had been surveyed in late April this year, and identified so-called Grade-2 and -3 leaks that do not require immediate attention by the utility, the PG&E spokesperson said.

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