The aging natural-gas pipeline under investigation in the Sept. 9 San Bruno explosion and fire also runs through Palo Alto, according to a 2008 map from the California Energy Commission.
Known as Line 132, the 54-year-old pipeline runs down the Peninsula from San Francisco along the Interstate 280-Junipero Serra Boulevard corridor.
The line has not been replaced since its installation, PG&E spokeswoman Katie Romans said Friday.
Romans said the 30-inch steel pipeline was installed in 1956. The entire 51.5-mile gas line runs from Milpitas along California State Route 237 and Interstate 880 and ends in San Francisco at 23rd Avenue and Illinois Street, she said.
A 31.9-mile segment of Line 132 has been identified as needing retrofitting as part of PG&E's In-Line Inspection major capital-improvements projects for 2012, according to a PG&E report. It was not immediately clear if the Palo Alto segment is included in the 31.9 miles.
Line 132 is one of 10 aging pipelines scheduled for a retrofit, none of which currently can be inspected using the latest technology, called "smart pigging." Pigging is an industry term referring to the process by which a data-gathering instrument travels within a pipeline to accurately assess steel-pipe wall thickness and look for weakened metal due to corrosion and damage, according to a PG&E report.
Two other gas-transmission lines also run through Palo Alto, Menlo Park and Mountain View: Line 101 and Line 109, Romans said.
Line 109 is also located in the Highway 280-Junipero Serra corridor, and Line 101 runs near the U.S. Highway 101, according to a California Department of Conservation map.
The lines change diameter along the route, with a maximum of 30 inches, she said. She declined to give exact locations of lines 101 or 109, citing security concerns.
In Palo Alto, Line 132 runs along Page Mill Road and Oregon Expressway. It turns south on Alma Street, goes left onto El Carmelo Avenue, jogs south onto Waverley Street, then goes eastward on Loma Verde Avenue. It proceeds south on Cowper Street and heads east on Ashton Avenue, then continues south along Middlefield Road through Mountain View.
The last corrosion check on the pipeline was done in November 2009 and the last routine gas-leak surveys, which are above ground, were done on March 2010, she said.
Residents who live on the north side of Ashton in Midtown, in whose back yards PG&E Line 132 is buried, said PG&E and City of Palo Alto Utilities workers showed up as early as last Saturday (Sept. 11), two days after the San Bruno explosion, to inspect the pipeline.
A PG&E inspector used a machine to search for gas leaks in Cindy Campbell's yard but found none, she said. She asked if she could buy a similar detection machine, but the worker said they cost about as much as a small car. City utilities workers also stopped by on Wednesday, she said.
She said the pipe diameter is 24 inches along Ashton.
Residents expressed varying degrees of concern about the risk of a gas explosion in their neighborhood.
"It's a thing not likely to happen. I'm not that concerned. It hasn't been a problem before," said Jane Volpe, a Realtor, adding that both the city and PG&E had also visited her property.
But neighbor Judith Dvorak said she feels uneasy. There are a number of homes that are built too close to the PG&E gas-transfer line, she said.
When she and her husband planned to remodel their house in 1990, extending it into the back yard, they were told by PG&E that their remodel would not work due to the home's proposed proximity to the pipeline, she said. So the Dvoraks changed their plans.
But other neighbors have since rebuilt their homes nearer to the pipes, she said.
"I feel very uneasy especially because of the houses that are too close to the line," Dvorak said. "It's a sore point for us."
Another resident, who asked not to be identified, said that nothing has changed for her because of the San Bruno incident.
"What can I do? It's always been there," she said, referring to the pipeline.
But Campbell wants to use the San Bruno incident as a springboard for ensuring her neighborhood is safe. At an upcoming Ashton block party, Campbell plans on handing out the utilities department's "Gas Pipeline Safety Awareness" brochures and opening up a discussion with her neighbors about the topic.