An explosion destroyed two buildings and killed at least seven people in the Harlem neighborhood of New York City on Wednesday morning, and many are attributing the tragedy to natural gas. Federal investigators are proceeding on the assumption that a gas pipeline leaked, and the ensuing buildup of methane combusted when ignited by an unknown trigger.

The size of the explosion and the impact it had on its surroundings put the downside of natural gas into the spotlight, once again raising an important question: Is our increasing reliance on natural gas too dangerous for America?

Source: Wikimedia Commons.

Our aging infrastructure
Statistically speaking, pipelines are the safest way to move natural gas. And quite frankly, when it comes to heating buildings and fueling appliances, there really isn't any other way to transport it. That said, as the nation's pipeline infrastructure continues to age, events similar to Wednesday's incident may become more and more common. The gas main at the center of this particular investigation is said to be 127 years old.

A pipeline dating to 1887 is not that uncommon in older cities like New York, Chicago, or Boston. Comparatively speaking, across most of the country the rest of our pipelines are not quite that old. But they're not that young, either: More than 60% of our country's natural gas lines were laid before 1970, while 37% are from the 1950s or earlier. Despite their age, though, these pipes are safe as long as they are inspected and maintained regularly.

Data from the Pipeline and Hazardous Materials Safety Administration, or PHMSA, the agency responsible for pipeline safety regulation and oversight, shows that since 1986 there has been no real meaningful change in the overall annual number of significant pipeline incidents, and the rate of deaths and injuries caused by pipeline failures has more or less declined.

However, the percentage of incidents caused by "material weld equipment failure" has increased significantly.

Beginning in 1986 and running through 2002, there wasn't a single year that experienced more than 16% of its incidents because of material weld equipment failures. After 2002, there wasn't a single year where that type of failure accounted for fewer than 20% of all incidents. In 2010, 2011, and 2012 material weld equipment failure incidents accounted for 30%, 31%, and 32% of all failures.

Many of these failures can be detected and prevented with proper oversight. That was the case with the 2010 tragedy in California, when a PG&E pipeline exploded and killed eight people and incinerated nearby houses. The city of San Francisco sued the PHMSA for doing an inadequate job enforcing the federal Pipeline Safety Act. The lawsuit followed a report by the National Transportation Safety Board that blamed PHMSA for having blind faith in pipeline operators and failing to identify and correct problems at PG&E for decades. The accident occurred because welding defects weakened the pipeline. 

More tragedies ahead?
There is no way of knowing whether the next natural gas pipeline leak will result in repair or devastation, but our infrastructure needs must be addressed. The American Society of Civil Engineers gives our national energy infrastructure the unimpressive grade of "D+," given its increasing age and limited maintenance .

On top of that, recent studies by researchers at Duke University and Boston University found more than 3,000 gas leaks under the city of Boston, and close to 6,000 in Washington, D.C. Though these studies weren't originally intended to assess explosion risks in the cities' pipeline system, researchers did identify multiple locations in both cities where concentrations of gas exceeded safety thresholds.

The Boston study found that the leaks were distributed evenly across neighborhoods and were largely associated with old cast-iron pipes. If our infrastructure needs aren't addressed, Wednesday's tragedy may become all too familiar.

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