Three years of state-federal negotiations aimed at making sure that oil and gas drilling rigs in federal waters meet the same strict or comparable air pollution emission standards imposed onshore have ended in a stalemate, the Department of Interior announced. The discussions "found a lot of common ground, but the parties could not agree on technical details," said Tom DeRocco, a department spokesman. Instead, the department said it would unilaterally propose its own rules, but declined to discuss them. DeRocco said only that the rules would reflect concerns raised during the negotiations. California state and local officials have long complained that federal regulations require states to impose tough emission controls on motor vehicles and stationary sources onshore, while no similar requirements are required for drilling rigs in federal waters.