As a further demonstration that it's a more transparent world for natural gas pipeline operations in California, Sempra Energy's San Diego Gas and Electric Co. (SDG&E) on Thursday outlined efforts to step up safety and maintenance following the pipeline explosion in San Bruno, CA, last year.
The five-member California Public Utilities Commission (CPUC) later in June is expected to require all California operators of intrastate natural gas transmission pipelines to prepare implementation plans to pressure test or replace all pipeline segments that have not been tested or lack sufficient records verifying such tests (see Daily GPI, May 16). Regulators are expected to adopt a proposed decision released last month by Administrative Law Judge (ALJ) Maribeth Bushey.
In the meantime, SDG&E said it has begun retrofitting segments of a 51-mile transmission pipeline that stretches from Rainbow to San Diego's Miramar area in north-central San Diego County. "This retrofit will include installing pipe supports, fittings and valves that will enable a sophisticated sensor to traverse the pipeline's interior," a Sempra utility spokesperson said.
The work is expected to encompass about nine months, stretching into March next year. SDG&E is planning major excavations in six locations in the northern and southern parts of San Diego County.
Sempra's other California utility, Southern California Gas Co. (SoCalGas), the nation's largest gas distributor, has been doing similar work on its transmission system, according to a spokesperson. The work involves retrofitting major transmission lines with equipment needed to allow for inline inspections, or smart pigging of the lines.
"[SoCalGas] retrofitting of pipelines to make them piggable has been going on since 2003," said the spokesperson, noting that the work involves replacing existing valves and fittings that don't accommodate the smart pig. "We have a pipeline right now that we are retrofitting to allow for inline inspection."
While expanding SDG&E's customer reminders regarding precautions in digging around gas pipelines and calling with reports of gas odors, the utility said it was developing a new distribution pipeline integrity management program to include:
The latter is called a "crossbore," and SDG&E said its occurrence is rare, but the utility has started a five-year safety inspection program in areas that would be most likely to experience this phenomenon. SDG&E said it estimates crossbores could potentially impact about 6% of its 850,000 gas utility customer base.
"Crossbores are an emerging issue for the nation's gas utilities, and SDG&E is one of several utilities nationwide to initiate an aggressive inspection program," said the spokesperson, noting that the construction methods leading to crossbores: horizontal directional drilling and pneumatic boring first occurred in the 1970s. "In the process a plastic or metal natural gas pipeline might have bored through sewer pipelines, which are made of clay and other porous materials."
It creates a safety risk when a plumber or homeowner attempts work using a mechanical snake machine on a sewer line that has a gas pipeline crossbore. "These machines could sever a gas pipeline and cause a gas leak, which could result in a dangerous situation," the spokesperson said.
SDG&E said it was taking "extra proactive steps" to ensure customer safety and draw attention to the situation, despite having found only one plastic gas pipeline crossbore in the utility's history.
Technology improvements and construction practices have all reduced the possibility of crossbores, SDG&E said. In 2008 the utility said it began installing safety devices that restrict gas flow in the event that a service line is severed. Advanced video equipment also is used now to inspect sewer lines before and after installing another utility pipeline.
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