Old, leaky natural gas pipelines are “a danger hidden beneath the streets of New York City” and other cities, according to a recent article in the New York Times.

The newspaper reported that there are 6,302 miles of pipes transporting natural gas under the streets of New York City, and many of them are prone to leaks that can cause explosions like the one last month in Manhattan that killed eight people and destroyed two buildings.

Consolidated Edison, whose pipes supplied the two buildings leveled by the explosion, had the highest rate of leaks in the country among natural gas operators whose networks totaled at least 100 miles, according to the newspaper’s analysis of records collected by the U.S. Department of Transportation for 2012.

“In 2012 alone, Con Edison and National Grid, the other distributor of natural gas in the city, reported 9,906 leaks in their combined systems, which serve the city and Westchester County,” The Times reported. “More than half of them were considered hazardous because of the dangers they posed to people or property, federal records show.”

Most of the leaks in New York proved harmless, simply dissipating into the soil or air, the article stated. “But when gas finds an ignition source, the results can be deadly. Three separate episodes in Queens in recent years killed people, and a half-dozen others in the city left people injured, according to federal records dating back 10 years,” The Times wrote.

Elsewhere in the country, a rupture in a major pipeline in San Bruno, Calif., in 2010 caused an explosion that killed eight people. In 2011, a leak from an 83-year-old cast-iron main in Allentown, Pa., caused a blast that killed five people, The Times reported.

“Nearly half of the gas mains operated by Con Edison and National Grid were installed before 1940, according to federal records. More than half of the mains are made of cast iron, wrought iron, or unprotected steel — materials that are vulnerable to corrosion and cracking, especially in cold weather,” The Times wrote.

To replace all of the old mains in its network right now would cost as much as $10 billion, Con Edison estimates. Much of that expense would fall on the residents and businesses that use the gas for heating and cooking.

To read the New York Times article, click here.