"East Harlem Explosion Highlights Risk of Natural Gas Leaks"

"The deadly explosion that ripped apart two buildings in New York's East Harlem on Wednesday morning brings new attention to a risk experts have been warning is especially great beneath the oldest U.S. cities: natural gas leaks.

Con Edison, the utility that services New York, said via Twitter that it was on the scene responding to a gas leak just before the explosion at about 9:40 a.m. The blast was so violent that it sent people "flying out the window," according to reporting by the New York Daily News. ...

The explosion comes at a time when utility companies in many parts of the United States are grappling with a difficult problem: what to do about aging natural gas mains, many of them in difficult-to-access locations in older urban areas, which have deteriorated and are prone to leaking. The gas mains that are cause for most concern are made of cast iron, many of them dating back to before World War II. (See related quiz: What You Don't Know About Natural Gas.)"

Patrick J. Kiger reports for National Geographic March 12, 2014.