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. (AP Photo/Keith Srakocic, File)
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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. (AP Photo/Keith Srakocic, File)
