New York explosions expose nation's aging and dangerous gas mains
CNN/Stylemagazine.com Newswire | 3/17/2014, 9:30 a.m.
In East Harlem, the gas pipe serving the collapsed buildings included a cast iron section dating from 1887, city officials said.
A cold and dangerous trap
"Cast iron and frost don't mix well," McDonald said.
Con Edison officials said the utility received a call reporting a gas leak around 9:13 a.m. Wednesday from a resident at one of the newer buildings on Park Avenue. The utility dispatched a truck two minutes later, but it arrived after the explosion. The caller, as well as other residents on the block, reported smelling gas the night before but did not call the utility at the time.
McDonald and other experts said underground pipes are a major source of gas leaks, with the escaping gas typically traveling through the soil and dissipating into the air. During winter, however, soil is hardened by frost, which traps the gas and causes it to travel sideways.
With warmer weather, the frost thaws and the soil contracts. Earth movements caused by construction work or other environmental factors can also cause pipes to crack.
"That expansion and contraction can heave the cast iron pipes up, down, left, right," McDonald said. "Being old doesn't help, obviously. But cast iron is a very fragile material when you bend it or displace it... If a leaky main is close to a building, about 4 or 5 feet away, the gas can work its way into a building."
The future is in plastic
Con Edison and other utilities around the nation have stepped up efforts to replace cast iron pipelines with plastic ones.
The utility is replacing an average of 65 miles of gas mains each year, for the next three years, at a cost of approximately $110 million, Con Ed spokesman Bob McGee said. In addition, the company spends about $500 million a year maintaining and upgrading the natural gas infrastructure.
"Age alone does not tell you about the condition of the pipe," McGee said in a statement. "Cast iron pipes can be used for hundreds of years if the underpinning and the environment around the pipes is sound."
Still, experts said, the old iron pipes beneath many U.S. cities are too vulnerable.
"Gas companies have been very lucky over the years to not have this happen more," Bob Ackley, a natural gas consultant who runs Massachusetts-based Gas Safety USA, said of the East Harlem explosion. "For every gas company across the northern part of this country, whether it's Chicago, Detroit, Cleveland or Buffalo ... this is a critical time. They have hundreds of broken mains going on around the country now, and they are lucky to catch most."
The aging infrastructure of cities such as New York, Boston, Philadelphia and Chicago make them especially susceptible to leaks and explosions, experts said.
In January, a study published by researchers at Duke University and Boston University detected 5,893 leaks of methane, the main component of natural gas, rising from the streets of Washington. At 12 of the tested locations, the study found "potentially explosive" concentrations of underground methane -- about 10 times greater than the threshold at which explosions can occur.
"I see the industry slipping in my opinion in terms of vigilance and protecting the public," McDonald said. "It's comes down to what can we cut, what can we avoid doing?"
The U.S. Department of Transportation estimates that more than 30,000 miles of cast iron pipe are still being used to deliver gas throughout the nation. The highest percentage of cast-iron mains are in Philadelphia, Washington, Boston and New York City.
"Let's hope gas operators get through this winter without another incident," Ackley said. "Con Ed and other national gas companies are really nervous right now."