According to a release by a group called Stonegate Citizens Safety Committee, the state’s Public Utilities Commission released two studies that paint a mixed picture about the large number of gas leaks in PG&E distribution lines in west Davis.
One study, released in May, attributed most of the problem to construction defects on “tee caps” – a part that sits above the section of pipe where the distribution line diverts to the service line to each home.
The report also stated that PG&E established an adequate system to obtain leak data and prioritize all its leak repairs based on a leak cluster methodology. West Davis has experienced a total of 96 gas leaks in PG&E’s distribution lines since 2006, up from a total of 90 by January 2013.
According to PG&E, most of the gas distribution pipe in the Stonegate subdivision is Aldyl A plastic, which is susceptible to brittle-like cracking and premature failures.
A second and more disturbing PUC report released in June, according to the group, about vintage Aldyl A gas lines, the type of pipe in west Davis, stated:
- “There could be different waves of failures unique to the operator in the oncoming decades. It is highly probable that the waves will occur sooner and with more intensity if the pipe is early vintage Aldyl A.”
- “The danger associated with slow crack growth on Aldyl A is that, although the failures develop slowly, when they do fail, they fail much more abruptly and rapidly than underground leaks on steel distribution pipes. Instead of small pin‐hole leaks developing slowly over a number of years, as is typical of steel pipes, leaks on Aldyl A are far more likely to be of a serious nature much more quickly. The 1996 San Juan (Puerto Rico) incident (where 33 people died) and the two 2011 California incidents are good examples of this abrupt failure characteristic.”
- “All…(utility) operators examined by us have a sizable quantity of pipes with unknown manufacturing dates, unknown resin types, unknown lot numbers, or even unknown manufacturer sources. Without more robust material traceability to know with a great degree of certainty what assets are in the ground, risk assessment and risk mitigation strategies will be at best enormously expensive and at worst ineffective.”
The Vanguard contacted PG&E to respond to these reports.
According to Brandi Ehlers, PG&E Corporate Relations Representative, “We continually monitor every foot of our gas distribution lines, including having crews walk every foot of distribution line in our system to perform a leak survey, deploying state-of-the-art vehicle mounted leak detection technology, among many other monitoring activities.”
“Due to our comprehensive leak detection approach we have been able to accelerate the repairs of even more minor, non-hazardous leaks that pose no threat to safety, and led to a 99 percent reduction in our leak backlog, from 12,500 to only 150 as of the end of 2013,” she said. “We are carefully examining the entire system and prioritizing the need for replacement or increased leak patrols through a review of leak history and repair record. This process will help us prioritize the needs for Aldyl-A replacement throughout our distribution system.”
She added, “Any time our customers smell gas and feel unsafe they need to call 9-1-1 and then PG&E. We’ll be sure to come out and do a full inspection inside and outside the house. Nothing is more important than the safety and peace of mind of the people we serve.”
“The safety of our customers, employees and the communities we serve is our top priority. We work hard every day to identify, fix and prevent natural gas leaks within our system,” stated Ms. Ehlers. “PG&E is committed to providing our customers with the safe and reliable gas service that they expect and desire.”
However, The June PUC report criticized California gas operators, including PG&E, for not acting on federal safety warnings about Aldyl A pipes in a timely fashion. The report concludes that slow crack growth on Aldyl A pipes fundamentally poses a high level of risk due to the abrupt nature of leaks created by this mode of failure, and more frequent leak surveys do not sufficiently mitigate the risk.
“These reports and the continued number of gas leaks confirm that we have a flawed system of distribution lines in west Davis. Gas pipes and tee caps made with vintage Aldyl A plastic are worse than we thought. We urge PG&E to do the right thing and replace these clearly unsafe gas lines, sooner rather than later. We plan to meet with PG&E representatives to discuss these concerns. Shareholder profits should never be placed ahead of neighborhood safety,” said David L. Johnson, a member of the Stonegate Citizens Safety Committee.
Although gas leaks have occurred throughout the entire Stonegate subdivision and other parts of west Davis, PG&E has replaced only about 2,000 feet of gas distribution lines and 28 service lines that lead to each home’s gas meter, or approximately 8% of the 4.7 miles of gas lines in Stonegate. The National Transportation Safety Board has recommended that all Aldyl A made through the early 1980s be replaced.
The June 11, 2014, California Public Utilities Commission report, Hazard Analysis & Mitigation Report On Aldyl A Polyethylene Gas Pipelines in California, can be found here.
The May 9, 2014, CPUC report, Report on Staff Investigation Of Leaks At Stonegate Subdivision, is found here.
—David M. Greenwald reporting