Pacific Gas and Electric Co. (PG&E) told California regulators in a report last week that some of its natural gas pipeline segments had been operating at pressures above those authorized for their locations and it is taking steps to correct the situation.

The San Francisco-based combination utility’s latest revelations were part of a report on its so-called “class location” review of 5,767 miles of pipeline (26,212 segments).

PG&E’s Nick Stavropoulos, executive vice president for gas operations, reiterated that the utility’s past practices were “unacceptable,” and he promised they would not happen again. Since the San Bruno, CA, pipeline rupture and explosion in September 2010 PG&E has periodically divulged similar missteps (see NGI, Dec.19, 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 said in its report to the California Public Utilities Commission (CPUC). However, it also divulged that “prior procedures and processes were not effective in maintaining accurate, up-to-date class location designations for all pipeline segments.”

According to the report, PG&E 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.

PG&E said steps have been taken to ensure “accurate, up-to-date class location designations for all pipeline segments” that include designating the utility’s Gas Transmission Engineering and Design director with ownership of and accountability for class location designations and keeping them current; revamping procedures for both pipeline patrolling and surveillance of class location to better define responsibilities; increasing training procedures; and providing an annual systemwide review of class location designations, which would be provided to CPUC’s Consumer Protection and Safety Division.

In reporting nearly 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 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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