FILE – In this March 29, 2013 file photo, workers tend to a well head during a hydraulic fracturing operation at an Encana Oil & Gas (USA) Inc. gas well outside Rifle, in western Colorado. The Obama administration is proposing a rule that would require companies that drill for oil and natural gas on federal lands to publicly disclose chemicals used in hydraulic fracturing operations. The new “fracking” rule replaces a draft proposed last year that was withdrawn amid industry complaints that federal regulation could hinder an ongoing boom in natural gas production. (AP Photo/ Brennan Linsley, File)