Oil and gas companies will soon have to start telling U.S. EPA before they "frack" wells, a development that has caught many in the industry off-guard and rekindled some drillers' most potent fears about federal intrusion. The notification requirement is a little-known aspect of air rules for hydraulic fracturing finalized earlier this year by the agency. The hard-fought and better-known aspects of the rule don't kick in until January 2015. But the email notice requirement starts Monday.