PG&E proposes replacement of gas pipelines through Stanford
Two major gas transmission pipelines that run along Junipero Serra Boulevard adjacent to Stanford University are scheduled to be among the first segments updated under a plan by PG&E to test or replace pipelines statewide that are aging or of older fabrication. They plan to replace one by 2013 and the other by 2014.
Two major gas transmission pipelines that run along Junipero Serra Boulevard adjacent to Stanford University are scheduled to be among the first segments updated under a plan by PG&E to test or replace pipelines statewide that are aging or of older fabrication.
PG&E engineers told university officials at a meeting on campus May 9 that they are proposing to replace, and possibly relocate, nearly all of the two gas transmission lines that run for more than a mile through Stanford land. They plan to replace what is identified as Line 109 – originally installed in 1936 – by 2013, and Line 132 – originally installed in 1947 – by 2014. The proposal needs to be turned into a detailed design and is subject to approval from the California Public Utilities Commission (CPUC).
In the meantime, PG&E will conduct hydrostatic testing on most of Line 132 along Junipero Serra Boulevard by the end of 2011. The pressure testing, in which the lines are filled with water pressurized to 150 percent of rating, is being required by the CPUC. But PG&E engineers said that regardless of the outcome of the testing, the lines along Junipero Serra are among their highest priority for replacement.
PG&E officials said that both lines are currently operating safely at a reduced pressure of less than 300 psi, which is 80 percent of what the lines were operating at prior to the San Bruno explosion in September 2010.
"It was encouraging to hear that PG&E actually has a good understanding of the type of pipe and condition of the pipelines that traverse Stanford, and it is reassuring to know that these segments are a top priority for the utility," said Larry Gibbs, associate vice provost for Stanford's Office of Environmental Health and Safety. "Stanford officials will continue to work closely with PG&E on its testing and replacement work as well as ensure that important ongoing local projects in the vicinity of the pipelines are appropriately coordinated with the utility company."
The pipelines are targeted for replacement based on the date they were installed and the type of pipe that was used, PG&E engineers said. They added that they have complete documentation of the original installations of both Lines 109 and 132 through Stanford. Line 109 along Junipero Serra is a non-standard 22-inch diameter pipe and would be replaced with a standard size. Both new lines would be installed with the latest materials and designs, which would allow for internal inspections.
PG&E officials indicated they would like to hold an open house on campus in advance of the pressure testing of Line 132, to inform the community and respond to questions from residents of the areas closest to the pipelines. They also said that written notice would be provided to residents within 2,000 feet of the transmission pipelines before any testing would take place. Hydrostatic testing could take two weeks or more to complete.
The meeting between university staff and PG&E was the result of ongoing conversations that have been taking place since September, when the utility notified the university that pipeline segments along Junipero Serra Boulevard were on a "top 100" list for maintenance priority.
Stanford has been asking PG&E for detailed information about the condition and maintenance history of the gas lines. The university also has sought details about PG&E emergency response and readiness plans in the event of an earthquake or other emergency, and details about emergency shutoff valves.
PG&E representatives said that large gas pipelines have performed well in earthquakes and that Lines 109 and 132 through the campus should not be at risk because they are located in areas of lower ground movement and don't cross fault lines. They said that a greater risk from earthquake was at individual residences, where gas lines or lines to furnaces and water heaters are more likely to rupture.
The utility is in the process of developing detailed plans to install new automatic shutoff valves at various intervals along major pipelines statewide, including some on the lines in the vicinity of Stanford. They said they have been working with local fire and law enforcement officials to identify the locations of manual gas shutoff valves, so that the emergency responders can assist PG&E in gaining quicker access to the valves.
The pipeline engineers who met with Stanford officials are part of PG&E's Pipeline 2020 program, which is working to inspect and test the utility's nearly 6,000 miles of gas pipeline in California. As part of this effort, the utility is performing hydrostatic testing of 150 miles of pipeline and anticipating replacement of as much as 200 miles of pipeline, of which the Stanford segment is a small portion. The replacement efforts are being concentrated on older pipes in urban areas, they said.
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