The U.S. Environmental Protection Agency (EPA, or Agency) is finalizing amendments to the new source performance standards (NSPS) for stationary combustion turbines and stationary gas turbines pursuant to a review required by the Clean Air Act (CAA). As a result of this review, the EPA is establishing subcategories for new, modified, or reconstructed stationary combustion turbines based on size, rates of utilization, design efficiency, and fuel type. The EPA determined that combustion controls are the best system of emission reduction (BSER) for nitrogen oxide (NO<INF>X</INF>) emissions for most new, modified, or reconstructed stationary combustion turbines. For one subcategory, the BSER for NO<INF>X</INF> is combustion controls with the addition of selective catalytic reduction (SCR). The EPA further determined that the BSER for sulfur dioxide (SO<INF>2</INF>) emissions has not changed since the last NSPS review. Based on these determinations, the Agency is promulgating standards of performance in a new subpart of the Code of Federal Regulations (CFR). The Agency is also adding a subcategory for stationary combustion turbines that are used in temporary applications, exempting certain sources from title V requirements, and finalizing other provisions. The EPA is finalizing amendments to existing regulations to address or clarify specific technical and editorial issues.