Despite California regulatory approval to begin reinstituting higher operating pressures in its natural gas transmission pipeline system for the winter season, Pacific Gas and Electric still has 29 segments operating at reduced pressures, including its main Southwest supply line from the California-Arizona border (300 A-B), a spokesperson told NGI Thursday.

In total during 2011, PG&E reduced the maximum operating pressure (MOP) on about 46 different pipeline segments; 17 have had their MOP restored. “We report on this every two weeks to the California Public Utilities Commission [CPUC],” the spokesperson said. The numbers fluctuate as validation work uncovers segments needing repair or replacement.

At its final meeting for 2011, the CPUC approved a start at lifting pressure restrictions on some major transmission pipelines in the wake of last year’s San Bruno pipeline rupture and explosion (see Daily GPI, Dec. 19). In November PG&E requested increasing the MOP to 365 psig on three pipelines (Lines 101, 132A and 147), and it has done so, but ultimately it wants to raise the MOP a little more to 375 psig, according to the spokesperson.

“At this point, we are feeling confident that we will be able to meet winter demands,” the spokesperson said. “We’re continuing our MOP validation work which is part of our overriding commitment to operating a safe, reliable system. If we find anything [in the validation work] we may have to lower pressures again, but we are still confident that we’ll be able to meet winter demand.

The 29 segments still operating at lower-than-normal MOPs include five distribution feeder pipelines connected to the major transmission lines. Lines 101, 132A and 147 all have distribution feeders that need testing, so until those feeder lines are validated, the transmission line will not be raised to the full 375 psig MOP, the spokesperson said.

The hydrostatic testing and repair/replacement efforts completed on an accelerated basis in 2011 will continue in the new year, said the spokesperson. “A lot of the continuing reduced pressures are due to the validation work we have been doing, and we’ll continue to make sure our system is operating safely. We won’t restore pressures until we can validate that our system is operating safely and reliably.”

The pressures remain reduced on these many segments because of a variety of reasons, the spokesperson said, including hydrostatic tests, inline inspections and ongoing repair work. Validations do not always involve hydrostatic testing.

Some 24 different transmission pipelines have segments currently operating at below-normal MOPs, the spokesperson said. Those are Lines 57A, 101, 105A, 107, 109, 118, 131S, 131-30, 132. 132A, 142S, 147, 148, 151, 153, 167, 177A, 196, 220, 300A, 300B, 301A, 303N and 303S. Some of the segments had their pressures reduced by mandate from the CPUC, and others were done by the utility as a safety precaution.

“Pressure validations will continue through winter, but as I said earlier, we are confident we can meet winter demands. Assuring safety and reliability is our highest priority,” the spokesperson said.

It was a section of Line 132 in a residential neighborhood in San Bruno that had the rupture and explosion that killed eight people Sept. 9, 2010.

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