Utilities have been under pressure for years to better inspect and replace aging gas pipes - many of them laid years before the suburbs expanded over them and now are at risk of leaking or erupting.
But the effort has fallen short. Critics say the regulatory system is ripe for problems because the government largely leaves it up to the companies to do inspections, and utilities are reluctant to spend the money necessary to properly fix and replace decrepit pipelines.
"If this was the FAA and air travel we were talking about, I wouldn't get on a plane," said Rick Kessler, a former congressional staffer specializing in pipeline safety issues who now works for the Pipeline Safety Trust, an advocacy group based in Washington.
Investigators are still trying to figure out how the pipeline in San Bruno ruptured and ignited a gigantic fireball that torched one home after another in the neighborhood, killing at least four people. Pacific Gas & Electric Co., the pipeline's owner, said Monday it has set aside up to $100 million to help residents recover.
Experts say the California disaster epitomizes the risks that communities face with old gas lines. The pipe was more than 50 years old - right around the life expectancy for steel pipes. It was part of a transmission line that in one section had an "unacceptably high" risk of failure. And it was in a densely populated area.
The blast was the latest warning sign in a series of deadly infrastructure failures in recent years, including a bridge collapse in Minneapolis and a steam pipe explosion that tore open a Manhattan street in 2007. The steam pipe that ruptured was more than 80 years old.
Also on Monday, Rep. Maurice Hinchey told a federal hearing that the Environmental Protection Agency must regulate hydraulic fracturing, the natural gas extraction process that he said has contaminated water near drilling sites around the country.
The process, also known as fracking, blasts millions of gallons of water mixed with sand and chemicals, some of them carcinogens, deep into the earth to free gas from dense shale deposits. As a gas rush sweeps parts of the vast and lucrative Marcellus Shale region that underlies New York, Pennsylvania, Ohio and West Virginia, environmentalists are concerned for the watershed that provides drinking water for 17 million people from Philadelphia to New York City.
CBS News chief investigative correspondent Armen Keteyian reports the industry isn't required by law to disclose what potentially toxic chemicals are used in the drilling process. However, the EPA asked nine drilling companies last week for more information on exactly what's being pumped into the ground.
"There are numerous reports of water contamination related to hydraulic fracturing in states across the country," said Hinchey.
The section of pipeline that ruptured in San Bruno was built in 1956, back when the neighborhood contained only a handful of homes. It is a scenario that National Transportation Safety Board vice chairman Christopher Hart has seen play out throughout the nation, as suburbs have expanded.
"That's an issue we're going to have to look on a bigger scale - situations in which pipes of some age were put in before the dense population arrived and now the dense population is right over the pipe," he said.
Thousands of pipelines nationwide fit the same bill, and they frequently experience mishaps. 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."
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 precarious pipeline system.
Even when inspections are done and problems found, Kessler said, there is no requirement for companies to say if or what kind of repairs were made. And Weimer added industry lobbyists have since pushed to relax that provision of the law so inspections could occur once a decade or once every 15 years.
Other critics complain that the pipeline plans are drafted in secret with little opportunity for the public to speak out about the process.
The Pipeline and Hazardous Materials Safety Administration is the federal regulatory arm that enforces rules for the safe operation of the nation's pipeline system, and has direct authority over interstate pipelines. Most state public utility agencies have adopted the federal rules and carry out inspections and enforcement of pipelines running inside state boundaries.
Asked if it plans to step up oversight in response to the San Bruno accident, the PHMSA issued a statement saying it has investigators at the scene providing technical assistance to the California Public Utilities Commission and to the NTSB as they investigate the pipeline failure.
"We will evaluate what further action is necessary once we have complete information," the agency said.
But the system often relies on the pipeline operators like PG&E to survey their own gas lines and to decide which pipelines are high-risk.
The American Gas Association disputes the notion that it cuts any 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 ensuring federal pipeline safety is compounded by the sheer enormity of the nation's natural gas network. The Pipeline and Hazardous Materials Safety Administration says the U.S. has more than 2 million miles of pipelines - enough to circle the earth about 100 times.
The agency has only about 100 federal inspectors nationwide to ensure compliance, meaning there is no guarantee violators will be caught. "When you look at two-and-a-half million miles of pipeline with 100 inspectors, it's not reassuring," Weimer said. "To a grand degree the industry inspects and polices themselves."
Potential safety threats have grown as the pipeline network has expanded and age takes its toll on existing infrastructure. More than 60 percent of the nation's gas transmission lines are 40 years old or older.
Most of them are made of steel, with older varieties prone to corrosion. The more problematic pipes are made of cast-iron. A few places in Pennsylvania still had wooden gas pipes as of last year, according to officials there.
Pipelines in heavily populated locations like 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 roughly 21,000 miles of pipeline. The category has nothing to do with the safety of pipelines, and was created to put the greatest emphasis on the most populous regions.
Industry watchdogs have criticized utilities for not being willing to spend the money necessary to avoid explosions like the one in California. The cost to replace lengthy stretches of pipelines can exceed $30 million.
"They (PG&E) will prioritize and put off work to maintain their level of earnings," said Bill Marcus, a California attorney whose firm consults nationally with consumer protection agencies and nonprofits on gas rate cases. "To some extent that's not bad, but it is concerning when those decisions endanger public health or the environment."
PG&E said it has spent more than $100 million to improve its gas system in recent years, and routinely surveys its 5,724 miles of transmission and 42,142 miles of distribution lines for leaks. The utility speeded up surveys of its distribution lines in 2008 and expects to have completed checks in December, it said.
PG&E President Chris Johns said the pipe that ruptured was inspected twice in the past year - once for corrosion and once for leaks - and the checks turned up no problems.
A section of pipe connected to the line that exploded was built in 1948, and flagged as a problem by PG&E in a memo. PG&E submitted paperwork to regulators that said the section was within "the top 100 highest risk line sections" in the utility's service territory, the documents show.
The fact that it's in a heavily populated area that didn't exist when the pipe was built is emblematic of a bigger problem nationwide, experts say.
Meanwhile on Monday, U.S. Environmental Protection Agency officials said a leak from an oil pipeline outside Chicago had stopped.
WFLD-TV reported that a 1½-inch hole was found on the bottom of a 34-inch diameter pipe owned by Enbridge Energy Partners. Analysts said the leak caused a spike in gas prices across the region. Officials said repair of the pipe and cleanup are under way.
Enbridge also owns a pipeline that ruptured in Michigan in July and leaked at least 800,000 gallons of oil into a waterway there.