1,000 1,000 2,000 FEET METHANE CONCENTRATION parts per million 2.6 2.1 Methane plume 10 miles south of Washington, Pa. Drilling tower Washington Monument(for scale) 2,000 PENNSYLVANIA MARCELLUS SHALE FRACKING SITES COAL BEDS Area surveyed June 20 and 21, 2012 Pittsburgh Washington Methane plume in diagram above The EPA does not directly regulate methane emissions from the country’s 68,000 fracking wells, but in 2015, new rules will require new fracking sites to capture gas that currently escapes into the air during a period called flowback, when fracking fluids and gas rush to the surface. The air samples from the 2012 survey, however, were collected BEFORE flowback operations at the sites.Methane plumes might be the result of drilling through coal beds, which are known to release large amounts of methane when mined. Fracking sites in the Marcellus Shale formation are commonly located over coal beds.Worse than coal?Natural gas as an energy source for electric-ity production is less of a contributor to global warming than coal only if less than 3.2 percent of methane escapes during production. Recent measurements estimate that between 2.3 percent and 17.3 percent of gas escapes. As a heat-trapping greenhouse gas, methane is about 30 times more powerful than carbon dioxide. (Methane concentrations become explosive at 50,000 parts per million.) Purdue University’s Airborne Laboratory for Atmospheric Research is a modified Beechcraft Duchess aircraft. The plane collected samples over southwestern Pennsylvania on June 20 and 21, 2012, identifying seven wells in the drilling stage that were releasing large amounts of methane. Fracking sends drills thousands of feet down, often passing through methane-rich coal beds. Methane and other volatile gases escape at the surface. Once the drill reaches the shale formation, it makes a horizontal turn, following the shale seam. High-pressure fluids fracture the shale, allowing methane gas to flow to the surface. Coal bed Marcellus Shale 50 0 MILES

SOURCE: Dana Caulton, Purdue University; Proceedings of the National Academy of Sciences; Environmental Protection Agency; FracFocus; Wolfram Alpha.