Growing concerns about U.S. aging gas pipeline network

right over the pipe,” he said.

Thousands of pipelines across the United States fit the bill, and serious incidents are not infrequent. Federal officials have recorded 2,840 significant gas pipeline accidents since 1990, more than a third causing deaths and significant injuries.

“In reality, there is a major pipeline incident every other day in this country,” said Carl Weimer, Pipeline Safety Trust’s executive director. “Luckily, most of them don’t happen in populated areas, but you still see too many failures to think something like this wasn’t going to happen sooner or later.”

Burke and Dearen write that Congress passed a law in 2002 that required utilities for the first time to inspect pipelines that run through heavily populated areas. In the first five years, more than 3,000 problems were identified, a figure Weimer said underscores the precariousness of the pipeline system.

When inspections are done and problems found, Kessler said, companies are not required to say whether or what kind of repairs were made. Weimer said industry lobbyists have pushed to relax the inspection provision so regular inspections could occur once a decade or once every 15 years instead of on a seven-year cycle.

Other critics complain that the pipeline plans are drafted in secret with little opportunity for the public to speak out.

The Pipeline & Hazardous Materials Safety Administration is the federal agency that enforces rules for the safe operation of the nation’s pipeline system. State public utility agencies have adopted the federal rules and carry out inspections and enforcement.

The system, though, often relies on pipeline operators such as Pacific Gas and Electric to survey their gas lines and to decide which pipelines are high-risk.

The American Gas Association disputes the idea that the industry cuts corners and says the industry is subjected to stringent state and federal regulations.

“Safety is unequivocally the No. 1 priority for the natural gas transmission and distribution industry and always will be,” spokesman Chris Hogan said. “The industry spends billions each year to ensure the safety and reliability of the natural gas infrastructure.”

The challenge of making pipelines safe is compounded by the size of the nation’s natural gas network. The Pipeline and Hazardous Materials Safety Administration says the United States has more than 2.5 million miles of pipelines, enough to circle the Earth about 150 times.

The federal agency has about 100 inspectors nationwide to enforce compliance, meaning there is no guarantee violators will be caught. “When you look at 21/2 million miles of pipeline with 100 inspectors, it’s not reassuring,” Weimer said. “To a grand degree, the industry inspects and polices themselves.”

p>Safety threats have grown as the pipeline network has expanded and as age has taken its toll on the infrastructure. More than 60 percent of the nation’s gas transmission lines are forty years old or older.

Most of them are made of steel, and older varieties are prone to corrosion. More problematic are pipes made of cast iron. A few places in Pennsylvania still had wooden gas pipes as of last year, officials there said.

Pipelines in heavily populated locations such as San Bruno fall into a category the industry refers to as “high-consequence areas.”

Those areas contain about 7 percent of the 300,000 miles of gas transmission lines in the country, or about 21,000 miles of pipeline.

Industry watchdogs have criticized utilities for not being willing to spend the money necessary to avoid explosions such as the one in California. The cost of replacing lengthy stretches of pipelines can exceed $30 million.

“They will prioritize and put off work to maintain their level of earnings,” said Bill Marcus, a lawyer whose firm consults on gas rate cases with consumer protection agencies and nonprofit groups across the nation. “To some extent that’s not bad, but it is concerning when those decisions endanger public health or the environment.”

PG&E said that it has spent more than $100 million to improve its gas system in recent years and that it routinely surveys its 5,724 miles of transmission and 42,142 miles of distribution lines for leaks. The utility said it speeded up surveys of distribution lines in 2008 and should have checks done by December.

The risk created by population growth over the pipeline is part of a national problem, experts say.

“People have been waiting for a while for this type of disaster to happen because of expanded construction near pipeline right of ways without adequate prevention,” said Paul Blackburn, a public interest lawyer in Vermillion, South Dakota.