Pacific Gas and Electric Co. has been temporarily spiking pressure on major gas transmission lines since 2003, pushing levels to the legal limits on 10 lines in addition to the San Bruno pipeline that exploded less than two years after the last such surge, The Chronicle has learned.

Experts expressed concern that PG&E's intentional surge on the San Bruno pipe, as reported in The Chronicle last week, could have weakened the line before an accidental spike on Sept. 9 coincided with a fireball that killed eight people and destroyed 38 homes. They said the same danger exists on the 10 other transmission lines where PG&E now admits it pushed pressures beyond the levels at which the lines usually ran.

That danger is underscored by questions about whether PG&E's records for the 10 transmission lines are accurate or, as in the case of San Bruno, fail to show their true characteristics. Erroneous records could have led the utility to set maximum pressure levels higher than what the pipes could actually withstand.

San Bruno's representative in the House, Jackie Speier, denounced PG&E's practice as "Russian roulette" and said prosecutors have begun a "civil and criminal review" of events leading up to the San Bruno explosion.

"It's a gross irresponsibility to place ratepayers at that kind of risk," said Speier, D-Hillsborough. "This is all being taken very seriously."

San Mateo County District Attorney Steve Wagstaffe confirmed that prosecutors were looking at the circumstances surrounding the San Bruno disaster.

"We are looking at it with our eyes open to all possibilities," he said. "It could be civil or criminal, but at this stage it is too early to reach any conclusion."

PG&E says the increases were a "very safe" practice intended to preserve its "operational flexibility." But it announced last week that it had suspended the practice in light of the federal investigation into what caused the San Bruno explosion.

Examining pipelines

The utility acknowledged in response to a Chronicle query that it had at times elevated the pressure on the 10 lines in addition to the San Bruno pipe. But it would not identify the locations of those 10 lines.

Brian Swanson, a spokesman for the utility, said PG&E is still doing a "very thorough examination of records" to determine the circumstances and location of each of the pressure increases.

"We're continuing to verify how many times and when and which segments were involved," Swanson said. "We're still verifying records on all our other lines."

PG&E did say it had increased the pressure on the 11 lines a total of a dozen times since 2003, and that two of those were on the San Bruno line - the December 2008 spike reported by The Chronicle last week, and an additional surge in December 2003, shortly after a federal inspection law took effect that was based on pipelines' pressure caps.

Setting a cap

That 2002 law dictated how any pipeline designated as running under a "high-consequence area" - generally, a populated region - would be regulated, based in part on the peak pressure level at which it was run in the previous five years.

Once that five-year peak level was set for older lines that have not undergone rigorous, time-consuming and expensive water-pressure testing - which is the case for much of PG&E's urbanized network in Northern and Central California - the law requires those tests if a pipeline's pressure ever spikes above that level.

In the case of the 11 lines, the utility has said, their five-year peaks were normally lower than their legal maximum pressures because they were connected to weaker lines with lower caps.

As a result, some critics suspect, PG&E began pinching off the weaker lines for short stretches and spiking pressure on 11 lines to the legal limit, to establish a higher inspection threshold and avoid the need for the rigorous water-pressure tests should an accidental surge occur.

San Bruno spikes

On the San Bruno line, PG&E spiked the gas pressure to the legal maximum of 400 pounds per square inch in December 2003 - above the 375 pounds at which the line normally ran - then declared the line as being in a high-consequence area in 2004.

It spiked the pressure again to 400 pounds in 2008. When the pipeline exploded on Sept. 9, the pressure had surged to 386 pounds because of a malfunction, federal investigators found.

Richard Kuprewicz, a pipeline safety consultant in Redmond, Wash., said the utility's practice was "crazy."

"It's so backward in its thinking - you wouldn't think anybody would be that reckless," he said. "The overall intent of the (federal inspection) program was, you are not supposed to look for loopholes."

James Hall, a former chairman of the National Transportation Safety Board and a pipeline safety advocate, said PG&E's practices amounted to "gaming the system."

"It's difficult when the rule-making is impacted by the devious and the safety programs are run by the devious," Hall said. "Now we have seen the consequences."

Feds' concerns

Robert Eiber, a pipeline integrity consultant and researcher in Columbus, Ohio, said, "I have never heard anything like this. ... They were foolish to have done it."

The federal Pipeline and Hazardous Materials and Safety Administration issued a statement Friday related to PG&E's practice that said, "In some cases, raising the pressure on a line can heighten the risk of problems on the line. If so, the operator must take that pressure change into account as part of their management of that line."

In response to criticisms, PG&E's Swanson said raising pipeline pressures to legal maximums still provided for a "very wide margin of safety."

"Operators throughout the industry routinely increase and decrease pressure in pipelines for a variety of reasons, and are permitted to do so" under the law, Swanson said. "Increasing the pressure on a transmission line to full (maximum) is permitted by code and was part of PG&E's routine program to ensure operational flexibility."

What's in the ground?

Although the utility has suspended the practice, Swanson said PG&E "will continue to adjust pressure on its pipelines up to (the legal maximum) to meet customer demands." He did not elaborate.

Carl Weimer, head of the nonprofit Pipeline Safety Trust, said PG&E's actions were troubling because "they don't know what was in the ground, yet they were monkeying with the pressure anyway. That shows incompetence."

The National Transportation Safety Board, which is investigating the San Bruno blast, expressed alarm this month that PG&E's records for the pipeline showed it had been constructed without seams. In fact, federal investigators found, the ruptured portion of the line not only had seams, but was pieced together in several 4-foot-long sections that were constructed to unknown, potentially inferior, specifications.

Seeking PG&E records

The investigators said they were examining the quality of the welds on those seams. They have not reached conclusions about what caused the disaster.

At the urging of the federal agency, the California Public Utilities Commission ordered PG&E to produce records of all its transmission lines by March 15 to show they can operate at the levels the utility says they can. So far, the effort has been difficult.

Richard Clark, head of the commission's Consumer Protection and Safety Division, said records are "scattered about their (PG&E's) various district and division offices and yards" and may not be reliable.

Early estimates, Clark said, are that PG&E will have to shut down about 400 miles of pipeline in its transmission system to test it with high-pressure water - the only sure way to account for their strength and to expose defects in welds that can lead to ruptures.

Joe Molica, a PG&E spokesman, said such tests can force the utility to take a gas line out of service for as long as 10 days. The per-mile cost of the test is as much as $500,000, he said.