FILE - In this June 25, 2012 file photo, a crew works on a gas drilling rig at a well site for shale based natural gas in Zelienople, Pa. Hydraulic fracturing to drill for oil and natural gas poses a risk to drinking water in some circumstances, but a lack of information precludes a definitive statement on how severe the risk is, the Environmental Protection Agency says in a new report that raises more questions than answers. (AP Photo/Keith Srakocic, File)
