A natural gas drilling rig discharges waste fluid into a holding pond in Clearville, Pennsylvania April 23, 2009. U.S. energy companies rushing to exploit Pennsylvania's massive natural gas reserves have launched a public relations campaign to calm fears the bonanza is contaminating water with toxic chemicals. Picture taken April 23, 2009. To match feature -GAS/DRILLING REUTERS/Jon Hurdle (UNITED STATES ENVIRONMENT BUSINESS ENERGY)