Pacific Gas and Electric Co. (PG&E) has begun to reduce operating pressures on an additional 7.5 miles of natural gas transmission pipeline segments and in some cases gas-fired power generation plants could be impacted, according to a recent filing the utility made to state regulators. Separately, the utility's ongoing hydrostatic testing of pipe also may be impacted by the additional pressure drops.
As part of a nine-month records search project, the latest report to the California Public Utilities Commission (CPUC) identified small segments on the PG&E pipeline system that have been reclassified and are therefore out of compliance with federal limits on operating pressures given the density of the nearby population within a mile of the lines. More than 30 locations and a dozen counties are involved.
Records for an additional 100 miles of transmission pipeline segments (less than 2% of the overall system) are being "aggressively reviewed" because according to PG&E's geographic information system (GIS) database, they may be operating at pressures higher than their current class levels allow. "PG&E may make additional pressure reductions as that review progresses," the utility's latest report said.
Many of the locations for pressure drops have been deemed by the San Francisco-based combination utility to have no customer impact, but others are thought to impact electric generators, so PG&E said it is working with the California Independent System Operator (CAISO) to coordinate the pressure drops, and it told the CPUC that in some cases it will seek special permits to resume higher pressures in some cases, particularly in heat-related peak electrical demand situations.
"We're moving swiftly to implement these changes in ways that are completely safe and will minimize potential impacts to our customers," said Jane Yura, PG&E's vice president for gas engineering and operations. While the segments in question represent about 0.1% of the overall 5,700-mile PG&E gas transmission pipeline system, Yura acknowledged that some of the segments serve "critical areas."
"We recognize that resolving these issues is another important step in earning the confidence of our customers and the public," she said. "We're moving aggressively to get the job done."
Regulators are publicly expressing concerns about the utility's latest revelation and the need for more pressure drops, while PG&E continues to emphasize that even with the reclassification of pipeline segments that requires the lowering of maximum allowable operating pressures (MAOP), the level of safety of the pipe segments in question has not changed. In its CPUC submittal, PG&E maintained that safety levels have remained uncompromised.
"Even though we are reducing pressure, the system is and was safe," PG&E said in its 12-page Class Location Study Report submitted last Thursday to the CPUC. "A class change requires an operator to confirm or revise its MAOP, if more people live nearby [the pipeline segments]. But the strength of the steel in the ground and its ability to safely operate does not change when a class location changes.
"A pipeline that was safe to operate when in a Class 1 location [lightly populated] is not 'unsafe' now that a new house is built and it is a Class 2 location."
The additional 100 miles that is now being focused on needs to be validated in regard to the various segments' complete pressure test records, based on PG&E's GIS information for the pipe strength testing and the MAOP.
While CPUC Executive Director Paul Clanon told the San Jose Mercury News that the latest revelations by PG&E represent a "serious failure with serious safety repercussions," he added that he hoped the end of these types of revelations was nearing. In a filing last Friday to the Securities and Exchange Commission (SEC) PG&E said it could not predict how the latest report would affect the utility's ongoing regulatory proceedings and investigations, some of which have called for heavy fines and penalties for the utility.
"PG&E Corp. and the utility also are unable to predict whether the utility will incur significant third-party liability related to service disruptions caused by pressure reductions on natural gas transmission pipelines," PG&E said in the SEC filing.
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