EPA is proposing amendments to the Standards of Performance for new, modified, and reconstructed stationary combustion turbines and stationary gas turbines. These amendments are based on a review of available control technologies aimed at limiting emissions of criteria air pollutants. The review of the NSPS is mandated by the CAA. As part of this review, the EPA proposes to create size-based subcategories for new, modified, and reconstructed stationary combustion turbines. These subcategories will also recognize differences in turbines that operate at varying loads or capacity factors and those using natural gas or non-natural gas fuels. The EPA proposes that the BSER for limiting NOX emissions from these turbines is the use of combustion controls along with post-combustion SCR, with some limited exceptions. Based on this BSER and updates in technical information, the EPA aims to lower the NOX standards for most stationary combustion turbines in this source category. Finally, the Agency is proposing amendments to address specific technical and editorial issues to clarify existing regulations. Comments must be received on or before 13 March 2025. POC is John Ashley tele: (919) 541-1458; and email: ashley.john@epa.gov. (Federal Register 13 December 2024 [Proposed Rule] Pages 101306-101356)