EPA has signed a final rule revising new source performance standards (NSPS) under the Clean Air Act for stationary diesel and gas-fired engines. The final rule is the result of a 2009 settlement between EPA and the American Petroleum Institute in which the agency agreed to limit operation and maintenance (O&M) requirements in the rule to emissions-related O&M and to allow owners and operators to use and maintain their engines so long as they are in compliance with the rule. Am. Petroleum Inst. v. EPA, No. 06-1321 (D.C. Cir. 6/4/09).

The final rule revises emissions limits for nitrogen oxides, particulate matter and hydrocarbons from large, stationary diesel engines—specifically compressionignition engines with a displacement of 10 to 30 liters per cylinder—to the same levels required by EPA regulations for similar size non-road diesel engines used in marine applications. The rule also revises the standards for large, stationary compression-ignition engines with a displacement greater than 30 liters per cylinder to align them with standards for similar mobile source marine engines. The final rule will be effective 60 days after it is published in the Federal Register.