Where are New York City’s gas mains located?

The East Harlem explosion that left at least eight dead after two apartment buildings collapsed Wednesday morning is still under investigation, but the prime suspect is a natural gas leak from the main under the street.

So where are New York City’s gas mains located? In short: just about everywhere.

Gas mains like the one under Park Ave. stretch up and down nearly every block of the city, with pipes branching off into every building. This is the city’s gas distribution system, and it consists mostly of low-pressure pipelines, which are controlled by Con Edison in Manhattan, the Bronx and parts of Queens. The distribution system in Brooklyn, Staten Island and the rest of Queens is maintained by National Grid.

The gas distribution system is distinct from the higher-pressure, interstate “transmission” lines, which transport gas in large volume cross-country and into the city.

Con Edison spokesperson Bob Magee says there are no large transmission lines near the East Harlem block where the explosion occurred. “The main we’re talking about would be an 8-inch,” Magee said. “We’re talking about a low-pressure main that supplies that street and that building.”

A recent report from the Center for an Urban Future detailing the fragile state of much of the city’s aging infrastructure found the average age of a section of its 6,300 miles of gas mains is 56 years. Much of this piping is made of cast iron, which is highly susceptible to leaks and bursts.

Con Edison also operates some transmission lines of its own, 50 miles worth, according to the company’s website. This system transfers gas from the interstate pipelines to the company’s 4,300 miles of gas mains and 384,000 service pipes branching off to buildings in New York City and Westchester. But detailed maps of the gas system are not readily available to the public.

The closest the public can get to a picture of subterranean urban gas lines is a web search of the U.S. Department of Transportation’s National Pipeline Mapping System, which reveals the companies operating transmission lines in each Zip Code and shows a schematic view on a map.

“Security of both the gas and electrical system is obviously a matter of some concern in a post-9/11 world,” said Magee, who urges anyone who smells even a whiff of gas to call 311 or 1-800-75CONED immediately.

The high-volume, interstate transmission lines that carry gas to the city run under the Hudson River, where they are transferred to Con Ed’s system soon after entering Manhattan, explains Magee.

From there, the gas lines run underneath all of us.

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