This week, under order from the California Public Utilities Commission, the company released a report, "Top 100 Segments," which identifies pipelines throughout its system that carry the greatest potential risk.
Palo Alto City Manager James Keene on Monday gave PG&E a deadline for providing accurate information on its gas mains that run through the city. He said Thursday morning PG&E officials have responded and arranged to meet with city staff.
Stanford University officials also met this week with PG&E personnel, following the disclosure that a 6,005-foot section of pipeline along Junipero Serra Boulevard is on the Top 100 list.
Palo Alto, which owns and operates its own utilities department, receives natural gas from PG&E and relies on three main transmission pipes, lines 101, 109 and 132. Line 132 is the same pipeline that exploded in San Bruno.
In his Monday letter, Keene requested the following information:
? A current map with precise locations of all PG&E high-pressure gas lines and other natural-gas facilities in Palo Alto
? Updated information on the condition of the city's PG&E natural-gas facilities
? Whether there are any high-risk gas-transmission facilities related to public safety in Palo Alto and where they are located
? Age of the pipelines and facilities
? Size of the pipelines
? Pressure at which PG&E typically operated the facilities
? Whether PG&E has reduced the operating pressure recently and what is the current operating pressure
? Scope and date of PG&E's most recent pipeline maintenance activities
? Frequency and nature of maintenance activities for all of PG&E natural-gas facilities in the city
Palo Alto utilities officials have taken pains to assure customers that the city-run natural-gas system is proactively maintained. In a statement on its website, the city described its "leak detection surveys, pipeline upgrades and replacements, pipeline corrosion control, 24/7 customer response, and promotion of gas safety awareness and education to residents and businesses in Palo Alto."
City personnel have also said that, while larger PG&E transmission lines such as Line 109 (22 inches in diameter) and Line 132 (24 inches in diameter) operate at between 100 and 400 pounds of pressure per square inch, smaller city-owner pipes distribute 25 pounds of pressure per square inch or less and are 2 to 12 inches in diameter.
Details have emerged about 54-year-old Line 132, which runs from Milpitas along California State Route 237 and Interstate 880, along the Peninsula, and ends in San Francisco at 23rd Avenue and Illinois Street.
In Palo Alto, Line 132 follows Page Mill Road to 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. (One stretch of the line along El Carmelo was "retired," a map from the federal Pipeline and Hazard Materials Safety Administration shows. A second, replacement line was installed along El Carmelo and currently is in use.)
The steel pipeline has not been replaced since its installation in 1956, PG&E spokeswoman Katie Romans said last Friday.
Line 132 is one of 10 aging PG&E pipelines scheduled for retrofit, since none currently can be inspected using the latest technology, called "smart pigging," according to a PG&E capital-improvements project report. 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.
Line 132 is slated for a $13 million retrofit and $1 million repair.
The last corrosion check on Line 132 was done in November 2009, and the last routine gas-leak surveys, which are above ground, were done in March 2010, Romans 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 Sept. 11, two days after the San Bruno explosion, to inspect the pipeline.
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.
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.
At Stanford, Larry Gibbs, associate vice provost for environmental health and safety, told the Stanford Report on Tuesday that staff is seeking to better understand the risks associated with Line 109, which was identified in the Top 100.
Several segments of the line along Junipero Serra are at risk of corrosion, according to the PG&E list. The utility conducted an analysis of the cathodic system (a process that protects the pipeline segment from corrosion) and adjusted that system for better protection. A subsequent 2009 analysis showed "marked improvement," and engineers will continue monitoring the segment.
Gibbs told the Stanford Report that PG&E monitors the pipeline both electronically and physically every two months.
"We will be working to better understand what work has been done on the pipeline, what will be done to ensure continued integrity of the pipeline and why the segments remain on PG&E's 'Top 100' list if no further action is contemplated at this time," he said.
In addition to Stanford's pipeline, an East Palo Alto segment appeared on the Top 100 — an 18-foot line near Dumbarton Avenue and Donohoe Street, west of U.S. Highway 101.
At a PG&E press conference Monday, several reporters questioned the Top 100 list's credibility, since the San Bruno segment that exploded did not show up at all as a "red flag."
PG&E President Christopher Johns said investigators' findings related to the explosion could help determine if present processes of evaluation for pipelines are good or not.
In response to an order by the California Public Utilities Commission, PG&E has nearly completed a resurvey of the three Peninsula pipelines, Johns said.
The pipelines in the Top 100 were evaluated against four criteria: potential for third-party damage during construction work; corrosion; ground movement; and physical design and characteristics of the pipe segment.
Concerned residents can call PG&E at 1-888-743-7431 to find out if their home or business is located within 500 feet of a gas-transmission line or if it is on the Top 100 list.
Managing Editor Jocelyn Dong, Editorial Intern Sally Schilling and Menlo Park Almanac Staff Writer Sandy Brundage contributed to this report.