A sophisticated safety inspection device required for many large natural gas pipelines couldn't be used in the San Bruno line that exploded last week because of design issues. However, the utility that owns the line said Monday it had complied with all federal testing requirements.
Pacific Gas & Electric Co. officials, seeking to reassure customers, said the steel pipeline that exploded Thursday, killing at least four people, was inspected regularly. Among the tests were a comprehensive external assessment for corrosion performed in November and a leak survey that was completed in March.
But an in-line device known as a pig, which can run inside a large gas transmission line, could not be used in the 51.5-mile section from Milpitas to San Francisco because of bends and changes in the pipe's diameter, PG&E President Chris Johns told reporters at a news conference.
The testing methods used by the utility, however, do not "have any less capability," Johns said. "These are proven methods."
Also on Monday, California's U.S. senators called on federal regulators to order inspections of all interstate natural gas pipelines in the state, with a priority on those that run near residential areas.
Federal regulations require pigs to be used in gas transmission lines wherever possible because they are superior to other forms of testing, said Cesar de Leon, a former head of the federal Pipeline and Hazardous Materials Safety Administration.
"It's the best way to test," said De Leon, now a pipeline safety consultant. Other tests "can miss things that the pigs would not miss" including, he said, "tiny, tiny losses" in the thickness of pipeline wall material.
By law, new pipelines must accommodate the devices, but many older lines cannot and owners are not required to replace them because it would be enormously expensive, De Leon said. The ruptured pipeline was installed in 1956.
PG&E stressed that, in addition to the recent corrosion and leak testing, it patrols gas transmission lines on foot once a year to look for issues that could cause damage, such as construction, and uses helicopters four times a year to fly over the pipelines to look for evidence of leaks, such as dying vegetation.
Late Monday, federal investigators said they examined a 28-foot section of pipeline that was ejected in Thursday's explosion and found no signs of damage from recent construction activity on nearby sewer lines.
"The initial observations don't show any physical damage," said Christopher Hart, vice chairman of the National Transportation Safety Board, which is leading the probe.
The sewer and water lines run underneath and perpendicular to the gas pipeline.
"We're looking at all previous projects that could affect this pipeline," Hart said.
Hart said the damaged section and two 10-foot sections from each side have been crated up and will be driven to a metallurgy lab in Washington, D.C.
NTSB investigators and the utility also have found no evidence that any customers called the utility to complain about gas odors in the days before the explosion, Hart said, which is at odds with claims made by some residents.
The NTSB's final conclusions on the blast are not expected for more than a year, but a preliminary report will be released by early October.
The utility announced a relief fund Monday of up to $100 million for residents displaced by the disaster.
Gas company officials said they expect to distribute checks by the end of the week of up to $50,000 for immediate daily needs. Money from the fund will also be paid to the city to help rebuild streets, parks and sidewalks.
"I realize money can't return lives; it can't heal scars; it can't replace memories," Johns said.
In their letter to the administrator of the Pipeline and Hazardous Materials Safety Administration, Sens. Barbara Boxer and Dianne Feinstein said it is imperative that Californians feel confident that their communities are safe and that "regulatory agencies responsible for maintaining natural gas pipelines are doing everything possible to guarantee their safety." They also said the public needs to be reassured that "utilities are held accountable for the safety of their pipelines."
The senators noted that California has 1,508 miles of interstate natural gas pipelines under the jurisdiction of federal regulators.
Boxer and Feinstein, who have toured the heavily damaged San Bruno neighborhood, asked federal pipeline regulators to provide a list of cities and counties in California where these pipelines run, give their dates of installation and explain if any have been upgraded.
PG&E launched an assessment of its gas transmission lines a decade ago, assigning a risk number to each segment based on the likelihood that it would fail and on the damage that could result.