 Featured in the documentary film Gasland, the Pennsylvania village of Dimock has been at the center of a fierce debate over drilling, in particular, the process of hydraulic fracturing or fracking. The process involves injecting a mixture of water and chemicals deep underground to free trapped natural gas so it can be brought to the surface. And critics have long claimed this has contaminated Dimock's drinking water. Now comes an authoritative study by the EPA investigating the matter. And what did they find?