This action is required by the Clean Air Act under the authority of Section 111(b)(1)(B) and responds to a notice of intent to sue filed by Sierra Club and Environmental Defense Fund (EDF). The terms of a consent decree established a deadline of November 22, 2024, for signature of a proposed rule and November 12, 2025, for signature of a final rule. On December 13, 2024, the EPA published proposed amendments to the new source performance standards (NSPS) under 40 CFR part 60, subpart KKKKa based on the findings of this technology review that included an analysis of criteria pollutant emissions from stationary combustion turbines and available control technologies. The technology review proposed post-combustion selective catalytic reduction (SCR) to be the best system of emission reduction (BSER) for limiting nitrogen oxide (NOx) emissions from most new sources in this category whether firing natural gas or non-natural gas fuels. The EPA did not propose to amend the standards for sulfur dioxide (SO2) and did not propose to set standards for additional criteria pollutants. The results of this action could impact the operators of stationary combustion turbines across several industrial sectors.