EPA is proposing five separate actions under section 111 of the CAA addressing GHG emissions from fossil fuel-fired electric generating units (EGUs). The EPA is proposing revised new source performance standards (NSPS), first for GHG emissions from new fossil fuel-fired stationary combustion turbine EGUs and second for GHG emissions from fossil fuel-fired steam generating units that undertake a large modification, based upon the 8-year review required by the CAA. Third, the EPA is proposing emission guidelines for GHG emissions from existing fossil fuel-fired steam generating EGUs, which include both coal-fired and oil/gas-fired steam generating EGUs. Fourth, the EPA is proposing emission guidelines for GHG emissions from the largest, most frequently operated existing stationary combustion turbines and is soliciting comment on approaches for emission guidelines for GHG emissions for the remainder of the existing combustion turbine category. Finally, the EPA is proposing to repeal the Affordable Clean Energy (ACE) Rule. Comments must be received on or before 24 July 2023. POC is Christian Fellner, Sector Policies and Programs Division (D243–02), Office of Air Quality Planning and Standards, EPA, Research Triangle Park, North Carolina 27711; tele: (919) 541–4003; and email: fellner.christian@epa.gov. (Federal Register 23 May 2023 [Proposed Rule] Pages 33240-33420)