Some of Pennsylvania's natural gas pipelines are 120 years old. Portions of lines also date to the 1800s in Massachusetts. And hundreds of miles in New York state are made of leak-prone cast iron.
Tens of thousands of miles of pipelines that run beneath communities nationwide are old or decaying, and an Associated Press survey found that no states in the parts of the country with the greatest concentration of people and pipes have ordered a safety review in the week since a deadly explosion in California raised public awareness of potential problems.
Officials from Massachusetts to Texas say their inspections are adequate, and they are waiting for federal investigators to determine the cause of the Sept. 9 gas line explosion that killed four in San Bruno, Calif., before deciding what to do.
Consumer advocates and plaintiffs' lawyers say the response fits a familiar pattern: Utilities and customers won't pay the millions of dollars needed to replace corroded pipes, the lines fail and regulators act only after a disaster.
Massachusetts is ahead of most states, in part because it reviewed its system after several natural gas explosions during the winter of 2008-09.
About one-third of the state's 21,000 miles of distribution lines are cast iron or bare steel. The cast-iron pipes were laid from the late 1800s to the 1940s and the bare steel between the 1930s to the 1960s.
Other states, however, are not acting as swiftly.
In Pennsylvania, the oldest pipes are 120 years old, and about 25 percent of its gas pipelines — including some serving Philadelphia — is made of unprotected cast iron and bare steel.
The system to replace them is inefficient and fraught with delays. Gas companies have to front the money to replace the pipes, and then petition state regulators for reimbursement. The process then gets bogged down.
To speed replacement projects, utility regulators are pressing state lawmakers to allow gas companies to charge customers more quickly. These charges would still require regulators' approval.
In New York, where parts of its 50,000 miles of gas pipeline still include leak-prone cast iron, gas companies are on track to replace about 310 miles of the worst sections this year, state regulators say.
"It would be great if it could all be replaced immediately, but it is very expensive and would cause rates to rise dramatically," spokesman James Denn said.
The AP also surveyed Texas, Michigan, Illinois, Florida, North Carolina, Connecticut and Louisiana.
There are more than 2 million miles of pipelines across the United States, and upgrading them is an enormous task, starting with determining the worst sections. Because regulators rely heavily on reports from utility companies themselves, critics say, it is impossible to gain an accurate picture of just how decrepit the system has become.
On Wednesday, after the Obama administration called for tougher oversight of the nation's pipelines, the head of the National Transportation Safety Board said federal regulators are too accepting of industry assurances.
Chris Hogan, a spokesman for the American Gas Association, the industry trade group, said that utility companies already spend billions every year to keep the network of gas pipes safe, and that more inspectors and harsher fines won't improve safety.
The last significant reforms for the industry came in 2002 — and only after several high-profile accidents in Texas, Washington and New Mexico killed a combined 17 people. That's when mandatory inspections were first required for transmission lines that go through densely populated areas.
Federal inspectors are responsible for interstate pipelines. Local regulators oversee intrastate lines and in most cases leave inspections to utilities. Regulators monitor and ensure that companies are keeping up with maintenance and identifying of old pipes.
Utilities usually pass on those costs to customers through increases in their monthly bills.
"The audits and inspections are designed to make sure that they're keeping up with the repairs, despite the fact that they have a financial incentive to put it off," California Public Utilities Commission spokeswoman Julie Halligan said.
A lawyer representing victims of the San Bruno blast has a name for it: "running to failure."
Mike Danko, who won a case against Pacific Gas & Electric after a deadly gas line explosion in 1992 in Santa Rosa, said utilities use equipment until it fails because its cheaper than preemptively replacing miles of pipes.
"They run the equipment until it fails and then deal with it," he said. "That high pressure gas line in San Bruno was 60 years old. Do you have to be an engineer to figure out it needs to be replaced?
"They're concerned about profits and they're going to run to failure, and that's the opposite of a company having a culture of safety."
PG&E says it is committed to conducting the inspections and maintenance required to assure the safety of its transmission system.
When the gas companies do inspect the lines for any corrosion — the second most common cause of pipeline incidents behind excavation — they send a robot, called a "pig," into the pipe.
The robot ranges in size from several feet to more than 10 feet long and comes in a variety of diameters to fit different sized pipes. It is propelled by the oil or gas streaming past. Data is then analyzed.
"Pigging" is cheaper and faster than other approved methods, such as excavating dirt to perform eyeball checks.
The high-tech methods can be particularly useful in the East, where utilities don't have to dig up streets in densely packed towns and cities to get access to the pipelines.
In San Bruno, the pipeline was laid years before the neighborhood was settled. PG&E crews could not "pig" the segment of the 30-inch diameter steel pipe that exploded because the robot could not navigate a curved stretch.
Instead, last November, PG&E used a method where a low electrical charge is pulsed through the pipe and corrosion is identified by changes in the signal.
The company did not release the test results because they are part of the NTSB investigation, but it has said there was no indication before the explosion of any problems with the pipe.
While federal investigators determine whether corrosion or something that could have been missed by PG&E inspectors played any role in the blast, other states are holding fast to their system.
Brent Campbell, director of Louisiana's Pipeline Safety Division, said regulators there would assess their system after the NTSB determines a cause in California.
"Right now, we have a very thorough inspection process and we'll continue with that," he said.
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