​EPA’s New Source Review (NSR) program remains a significant obstacle for power plant operators that are considering plant maintenance and repairs to impove unit reliability, increase efficiency, and reduce pollution. NSR is a federal air quality pre-construction permit program that was established under the Clean Air Act over 40 years ago. It requires EPA review of new power plants and major modifications to existing electric generating facilties. Although routine maintenance, repair, and replacement are excluded from the definition of major modifications, what qualifies as "routine" often changes due to shifting EPA interpretations.