In this March 25, 2014 photo, a machine mixes sand and water, left, before it is pumped underground during a hydraulic fracturing operation at an Encana Corp. well pad near Mead, Colo. (AP Photo/Brennan Linsley)

A close-up look at fracking

Workers bustle at an oil and gas drilling site near Mead, Colo., a town of about 3,800 people north of Denver.