US: According to a study published in the journal Environmental Science & Technology, there are nearly 6,000 natural gas leaks under the streets of Washington DC. Scientists from Duke University and Boston University say that they have discovered more than 5,893 leaks from aging natural gas pipelines under DC. Dozens of these leaks could pose an explosion risk, and some manholes have methane concentrations as high as 500,000 parts per million, which is about 10 times more than the threshold at which explosions occur, according to the team.
The team mapped out gas leaks under all 1,500 miles of road within DC using a high-precision Picarro G2301 Cavity Ring-Down Spectrometer installed in a car. Tests confirmed that the isotopic chemical signatures of methane and ethane found in the survey closely matched that of pipeline gas. According to the study, the average methane concentration in the Washington leaks was about 2.5 times higher than in background air samples collected in the city. Methane levels in some leaks were as high as 89 parts per million, which is about 45 times higher than normal levels. “Methane emissions from these four leaks ranged from 9,200 to 38,200 liters per day for each leak – that’s comparable to the amount of natural gas used by between 2 and 7 homes,” said Adrian Down, Duke PhD student Adrian Down.