PG&E has discovered 12 new gas leaks in Stonegate over the past month and a half, including six Grade 1 leaks along Lake Terrace Circle.
The utility company’s policy requires all Grade 1 leaks to be immediately repaired.
“Due to proximity of the leak or the severity, (Grade 1 leaks are) at a level that we deem to be repaired right away,” PG&E spokeswoman Brittany McKannay said Wednesday.
The newly discovered leaks — caused by failures in the plastic caps on the service tee lines where natural gas is piped to customers’ homes — pushes the total over the past five years in the West Davis neighborhood to 57.
In December, PG&E announced its plan to replace more than 2,000 feet of natural gas distribution line pipe in Stonegate, as well as 28 service lines that run to residents’ homes, in response to the deteriorating pipe and service tee caps that have been responsible for the majority of the leaks.
The pipe to be replaced runs along Marina Circle between Biscayne Bay Place and Secret Bay Place. PG&E also will switch out segments of main line pipe along Magellan Street, Secret Bay Place and Chesapeake Bay Avenue.
PG&E is targeting that part of the neighborhood because it has experienced the highest concentration of leaks.
The utility has declined to provide information about distribution lines under other Davis neighborhoods.
The new leaks have not prompted PG&E to alter its plan to replace only the 2,000 feet originally announced, McKannay said.
“At this point our replacement project remains the same,” she said. “These leaks were on the service tee caps. The replacement project that we’re doing is on the gas service main. After looking at the leak survey history, we felt it was important to replace the main line there.”
The chain of events began in November, when PG&E discovered six separate leaks in about a one-block radius on Marina Circle, after residents reported smelling gas.
PG&E crews then began performing biweekly gas leak surveys in selected areas throughout Stonegate and subsequently found a spate of new leaks, prompting the replacement plan.
However, last month, after residents in Stonegate again complained of smelling gas, the utility discovered six more leaks on Lake Terrace Circle and subsequently repaired them.
Lake Terrace Circle had not been part of the biweekly gas leak surveys PG&E had been performing over the past months.
The failure of the pipes once again call into question the reliability of Aldyl “A” pipe, which PG&E has confirmed makes up the majority of the distribution lines underneath Stonegate.
But Gene Palermo, a plastic pipe consultant who worked for Dupont in the Aldyl “A” polyethylene pipe business for natural gas distribution for about 30 years, said plastic pipe is the best material for the job.
He said any impinging rock or bending in the pipe does reduce the service life, however, his research shows the failure rate is low.
“The rate is about four leaks per 100 miles of pipe per year,” Palermo explained. “If you look at the other pipe material that’s used, such as metal, the rate is about 43 leaks per 100 miles, or 10 times more, because of corrosion.”
According to PG&E, about 4.7 miles of distribution line pipe runs underneath Stonegate. Using Palermo’s numbers, that should yield only one leak over the past five years.
“Those are statistics that the gas company should be considering replacing the pipe,” Palermo said. “That’s definitely a failure rate that’s higher than what I’ve seen.”
Beyond the 2,000-foot replacement project, PG&E also is working to develop a GIS program to provide more detail about Davis’ natural gas distribution system.
Meanwhile, the Davis Fire Department continues to work with the utility to monitor the process and the plan.
Fire Chief Bill Weisgerber reminds residents to call the Fire Department if they smell natural gas.
“PG&E is keeping us informed with their progress,” Weisgerber said. “It’s a rather involved undertaking and it’s going to take some time to execute this replacement project.
“By the same token, the Davis Fire Department is at the ready to respond. If people do think they smell gas, call us.”
— Reach Tom Sakash at firstname.lastname@example.org or (530) 747-8057. Follow him on Twitter @TomSakash