Pacific Gas and Electric Co. (PG&E) told California regulators in a report filed Tuesday that some of its natural gas pipeline segments had been operating at pressures above those authorized for their locations. As part of the larger revamping of its entire gas operations, PG&E said it has taken a number of steps to correct the violations of its own and industry standards.

The San Francisco-based combination utility said as part of the corrective actions it has adopted a “more conservative” approach than called for under current industry regulations. These latest revelations come as part of a report on the utility’s so-called “class location” review of 5,767 miles of pipeline (26,212 segments).

Nevertheless, Nick Stavropoulos, PG&E’s executive vice president for gas operations, reiterated that the utility’s past practices were “unacceptable,” and he promised they would not happen again. Over the past 16 months since the San Bruno pipeline rupture and explosion that killed eight people, PG&E has periodically divulged similar missteps and similarly promised the errors would not be repeated (see Daily GPI, Dec. 15, 2011).

“PG&E’s systemwide verification of its class locations has established that the designations today are at or above the appropriate level,” PG&E told the California Public Utilities Commission (CPUC) in its report. However, it also divulged that it “discovered that PG&E’s prior procedures and processes were not effective in maintaining accurate, up-to-date class location designations for all pipeline segments.”

It found 806 pipe segments with incorrect class location (1 through 4, depending on the level population and building densities) and that 48 of these were operating at pressure-stress levels too high for their class locations.

Having laid out the bad news, PG&E said the good news now is that steps have been taken to ensure “accurate, up-to-date class location designations for all pipeline segments.”

Among those steps are:

In reporting some 540 miles (9.4% of its transmission pipelines) and 2,960 segments whose class location designations were changed (one-third up; two-thirds down), PG&E said none of the differences affected the ill-fated transmission line in San Bruno (Line 132). More troublesome were the 48 segments (8.5 miles of pipe) that had maximum allowable operating pressures (MAOP) too high for their class locations.

“PG&E reduced pressure as necessary on all but one of these 48 segments and has completed hydro testing, replacement or other permanent mitigation on 28 of the segments,” PG&E said. “The remainder continue to operate at reduced pressure commensurate with their current class location pending action later this year.”

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