Pacific Gas and Electric Co. (PG&E) on Monday filed a final report on its reclassification of its pipelines, but it said validating operating pressures will take more time. As result of the latest effort, nearly 10% of the utility’s natural gas transmission pipelines (544 miles, or 2,837 segments) had classifications changed.

As part of one of three major California Public Utilities Commission (CPUC) proceedings following the San Bruno transmission pipeline rupture in September 2010, the latest report summarizes PG&E’s efforts to ensure every pipeline segment within its 6,000-mile transmission system is accurately classified.

“PG&E’s entire gas transmission system is now currently operating at an appropriate level of pressure for its class designation, and we are also in the middle of an unprecedented effort to validate the maximum allowable operating pressure [MAOP] of all of our transmission pipelines,” a San Francisco-based PG&E utility spokesperson told NGI late Monday.

This is supposed to give more assurance that the utility pipeline system is operating safely and reliably, the spokesperson said. While there is still a lot of MAOP validation work to complete, the combination utility has now validated the operating pressure on all of its transmission pipelines passing through highly populated areas, such as the residential neighborhood in San Bruno where a 30-inch diameter transmission line failed.

In its final report PG&E said it has completed the review of 5,767 miles of transmission pipelines, or 26,184 segments. Classification changes occurred on 9.4%, or 544 miles of pipe with about one-third of that total having classifications raised and two-thirds being lowered. Of the 159 miles of high-pressure pipeline that were raised in classification, a vast majority of the segments had been misclassified by the utility geographic information system (GIS).

In a separate initiative on record-keeping, PG&E is in the process of building an entirely new GIS system as one of the outcomes of the current regulatory proceedings (see Daily GPI, April 3).

As part of the PG&E classification effort, in late January the staff instructor from the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) conducted a training program on class location issues for PG&E’s staff at the CPUC Consumer Protection and Safety Administration. The trainer also is the co-founder of a digital database used by PHMSA for guidance and industry documents.

PG&E said it has completed and documented the new class locations for all 277 segments that went up in class and has an MAOP greater than 40% of its specified minimum yield strength.

It also repeated a report from earlier in the year that its classification review had led to identification of 58 segments, or a little more than nine miles of pipe, that were operating at pressure not appropriate for their class designations. “PG&E has taken action to make each of these segments commensurate with their current class location,” according to the utility filing. Some 14 segments, or 2.8 miles, did not have their class location increased but nevertheless had been operating for years with inappropriate MAOPs, PG&E said.

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