Pacific Gas and Electric Co. (PG&E) last Friday submitted more historical data to California regulators on the safety and maintenance of its natural gas transmission pipeline system. This supplements earlier information provided in the wake of last September’s pipeline rupture and explosion in San Bruno, CA.

The additional data from in 2007-2008 showed that 86% of those segments addressed have had their engineering or other identified work completed; for a more recent 2009 top 100 list, 56% of the identified segment work has been completed. The San Francisco-based combination utility has more than 20,000 pipeline segments in its gas transmission system.

PG&E’s segments typically are defined as lengths of pipe located between two valves that control flow and pressure. Segments range in size from four to 42 inches in diameter.

The pipelines typically operate at pressures between 100 and 1,040 psig (pounds per square inch gauge), the utility said. Federal limits for transmission pipelines such as the San Bruno pipeline that ruptured (Line 132) are set at 400 psi, and PG&E has used 375 psi as its operating limit. Since the San Bruno explosion, it has lowered pressures in San Bruno and other areas to 300 psi (see Daily GPI, Feb.4).

Both PG&E and the California Public Utilities Commission (CPUC) said last Friday they were placing the latest data, containing 36 pages of segment-by-segment listings, on their respective websites. The submittal by the utility was part of a safety phase that has been added to PG&E’s pending gas transmission rate case proceeding.

At issue in the rate case is how the CPUC intends to follow where and when the monies allocated for transmission pipeline integrity maintenance/safety programs are actually spent. “The CPUC may impose certain reporting requirements to track the funds spent on the capital expenditure projects listed on PG&E’s top 100 list,” a CPUC spokesperson said.

CPUC Commissioner Timothy Alan Simon said he wants to “know exactly how PG&E spends ratepayer dollars allocated by the CPUC for pipeline maintenance and repairs,” adding that the utility has flexibility in prioritizing funding that is allocated by the state regulators.

Simon emphasized that the “CPUC needs to monitor that spending to ensure PG&E is being effective and providing safe and reliable service. I hope through [the safety proceeding now ongoing] we can close that loop in our current regulatory process.”

In its latest data filing, PG&E stressed that “any issues identified as a threat to public safety are immediately addressed,” so its top 100 list includes segment issues of a less immediate concern — potential third-party damage from construction digging, corrosion and ground movement, along with physical design and characteristics of a particular portion of pipe. These factors are considered in relation to a given segment’s proximity to high-density populations and environmentally sensitive areas.

“Based on all of these factors the segments that warrant further evaluation, monitoring or other future action were included each year on a top 100 list to help in the development of future plans for work on our transmission pipelines,” said Brian Cherry, PG&E vice president for regulatory affairs, in a cover letter to the latest data to the CPUC.

The top 100 listing has been a regular part of the utility’s risk management program for its pipeline system, Cherry said. But since San Bruno, PG&E has also launched its Pipeline 2020 program (see Daily GPI, Oct. 14, 2010) that is focusing on what the utility has called “modernizing pipeline infrastructure, spurring development of the next generation pipeline inspection technologies, enhancing public safety awareness and emergency response planning, and developing industry-leading best practices.”

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