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Hidden beneath Boston lies a vast network of aging iron and steel pipes that leak natural gas from thousands of points under the city. A small number of these leaks emit large volumes of methane, a potent greenhouse gas, while others pose an immediate explosion hazard, according to a recent peer-reviewed study published in the journal Environmental Pollution.
Study of 100 randomly selected pipeline leaks revealed the existence of ‘superemitters’ and potential explosion hazards.
By Phil McKenna Mar 31, 2016
The study looked at 100 randomly selected leaks from leak-prone cast iron pipes, the oldest of which had been in service since 1893. Fifteen out of 100 leaks measured in 2012 and 2014 were found to be Grade 1—leaks presenting an immediate explosion hazard—and were reported right away to the local utility company for repair. Of all 100 leaks measured, seven, known as “superemitters,” accounted for 50 percent of the emissions.
“We’re at a point, in the Northeast in particular, where we haven’t been able to revitalize infrastructure as quickly as perhaps we should,” said lead author Margaret Hendrick, a Ph.D. candidate in Boston University’s Earth & Environment department. “This is a problem that is not specific to natural gas pipes. We see this in our roads, our bridges, even our electric grid.”
Nationwide, 15 percent of remaining, aging leak-prone natural gas mains have been replaced since 2010, according to the study. Local utilities across the country, however, still rely on nearly 30,000 miles of cast and wrought iron mains to distribute natural gas to consumers. On average, 110 gas distribution pipeline incidents occur each year. The majority of the aging pipes are located in older cities in the Northeast, Hendrick said.
A 2012 study led by Hendrick’s advisor, Boston University professor Nathan Phillips, found 3,356 gas leaks under Boston, some of which had been leaking for decades. Subsequent studies have shown a consistent pattern, identifying similar numbers of leaks in Washington, D.C., and Manhattan.
Measuring the rate at which the methane is spewing from individual leaks, however, is difficult. Hendrick and colleagues used plastic buckets, large Tupperware containers and the plastic cover from a sandbox to create custom-built chambers. The devices, which they weighed down with gravel-filled tubes of burlap, were used to capture and record the volume of gas emanating from manhole covers, sidewalk gaps, and pavement fissures.
Global Climate Change