In this March 29, 2013, photo, a worker uses a dipstick to check water levels and temperatures in a series of tanks for a hydraulic fracturing operation at an Encana Oil & Gas (USA) Inc. gas drilling ... more 
In this March 29, 2013, photo, a worker uses a dipstick to check water levels and temperatures in a series of tanks for a hydraulic fracturing operation at an Encana Oil & Gas (USA) Inc. gas drilling site outside Rifle, Colo. Hydraulic fracturing, or “fracking,” can greatly increase the productivity of an oil or gas well by splitting open rock with water pumped underground at high pressure. The process typically requires several million gallons of water per well. In western Colorado, Encana says it goes to great lenghts to recycle over 95 percent of the water it uses for fracking to save money and limit use of local water supplies. (AP Photo/Brennan Linsley) less 
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Associated Press | Photo By Brennan Linsley
Thu, Apr 11, 2013 5:33 PM EDT