In this March 29, 2013 photo, a worker helps monitor water pumping pressure and temperature, at the site of a natural gas hydraulic fracturing and extraction operation run by Encana Oil & Gas (USA) ... more 
In this March 29, 2013 photo, a worker helps monitor water pumping pressure and temperature, at the site of a natural gas hydraulic fracturing and extraction operation run by Encana Oil & Gas (USA) Inc., outside Rifle, in western Colorado. Proponents of hydraulic fracturing point to the economic benefits from vast amounts of formerly inaccessible hydrocarbons the process can extract. Opponents point to potential environmental impacts, with some critics acknowledging that some fracking operations are far cleaner than others. (AP Photo/Brennan Linsley) less 
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Associated Press | Photo By Brennan Linsley
Thu, Apr 11, 2013 12:55 PM EDT