Want to find out if gas pipelines near you are dangerous? It's not easy (© Tim Boyle/Getty Images)

© Tim Boyle/Getty Images

The huge natural-gas explosion that rocked a Northern California neighborhood last week alerted homeowners around the country to the risks posed by the nation's aging — and in some cases, ill-maintained — network of underground gas pipelines. It also underscored how little we know about the condition of pipes below us.

So how do you know if you might have a ticking time bomb in your backyard?

As it turns out, that's pretty tricky to pin down. Homeowners and buyers can find out about the safety record and location of gas pipelines in their area — and the operators that run them — on federal government websites, but it's difficult to pinpoint specific locations for accidents or find areas of pipeline tagged for repair or maintenance.

Finding pipelines near you
Local utilities will locate distribution pipes around your property in a few days if you dial the government's "811" call center from your home phone. But identifying so-called high-risk or damaged areas of pipelines near your house or a house you're considering buying can be much more difficult.

Read:  Your home's hidden environmental horrors

To get an idea of where a gas transmission line — the larger, high-pressure pipe that routes gas to your area — lies, you can use the Transportation Department's National Pipeline Mapping System Viewer and search by county. However, this does not show the smaller distribution lines that route gas from a transmission line to your house.

Uncovering problems
Every state except Alaska and Hawaii has a utility commission that regulates, inspects and enforces federal pipeline safety regulations. But, as with the California Public Utility Commission, these state agencies make it difficult for consumers to find information on the condition of pipeline, scheduled repairs or safety problems. The CPUC's website, for instance, posts its annual reports and proceedings online and urges consumers to request specific documents in writing (.PDF file) — if you know what you are looking for.

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The Transportation Department, which provides federal oversight of the nation's pipelines, provides links to mileage and "significant incident" reports for municipalities in each state through its Office of Pipeline Safety, as well as contacts for each region. It also provides enforcement data on pipeline operators in each area, including local utility companies.

And the National Transportation Safety Board releases public reports on pipeline accidents here.

The Utility Reform Network, or TURN, which is based in California, would like to see more transparency to homeowners about the pipes in their area. And it would like easier ways for consumers to report problems.

"We are advocating that the [California] PUC set up a dedicated phone line for consumers to call if they smell gas or have any reason to believe that there's something dangerous going on in their neighborhood," says Mindy Spatt, spokeswoman for TURN.

What homeowners weren't told before the California disaster
The 30-inch pipe that exploded in San Bruno, Calif., killing four people and destroying dozens of homes, was a transmission line, one that had been labeled high-risk and slated for repair in 2009. Its repair was then pushed back to 2013.

Pacific Gas & Electric, the utility operating the gas line in San Bruno, had identified that section of pipe as "high risk" in work papers submitted to the CPUC as early as 2007.

However, that PG&E report was not a public document and was released only this week by TURN. Here's an excerpt of what residents in San Bruno couldn't read about their neighborhood (View the complete documents here.):

"The pipe is 30-inch diameter pipe, has a potential impact radius of 415 feet and is located in a heavily urbanized area. If the replacement of this pipe does not occur, risks associated with this segment will not be reduced. Coupled with the consequences of failure of this section of pipeline, the likelihood of a failure makes the risk of a failure at this location unacceptably high."

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PG&E would not comment on these documents or provide public access to safety and risk data. The CPUC has ordered the utility to inspect its entire natural-gas system as a result of the explosion.

So far, no specific cause of the accident has been identified. The National Transportation Safety Board has launched an investigation, but the results won't be available for some time.

Residents in the area had reported smelling gas for weeks, although PG&E has no record of complaint calls and consumers can't track complaints in their area on its website.

How prevalent are gas pipeline accidents?
Over the past two decades, there have been 846 "significant" incidents from onshore gas transmission, resulting in 33 fatalities, 173 injuries and $757 million in property damage, according to the Transportation Department.

That's still a relatively low number, experts say, given that there are more than 300,000 miles of interstate and intrastate pipelines crisscrossing the country.

But as the country's pipeline infrastructure gets older — 60% of the country's gas transmission pipelines were built before 1970, according to federal data — state and federal agencies will need to provide better oversight of pipeline operators or risk more accidents similar to the San Bruno disaster.

"Customers are looking to their utility companies to assure them that this won't be happening in the future," says Spatt, pointing out that TURN doesn't believe PG&E properly inspects and maintains its pipes. "The system that has been in place so far has failed."

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