On May 23, 2023, under section 111 of the CAA, the EPA proposed greenhouse gas (GHG) standards and emission guidelines for new and existing fossil fuel-fired electric generating units (EGUs), and repeal of the Affordable Clean Energy (ACE) Rule. As a part of that action, EPA proposed GHG emission guidelines for a subcategory of existing combustion turbine EGUs. On April 24, 2024, the EPA finalized the other components of that action, but did not finalize the emission guidelines for the existing combustion turbine EGUs. EPA is now undertaking a new rulemaking to establish GHG emission guidelines for existing fossil fuel-fired combustion turbine EGUs under CAA section 111(d). Consistent with the charge to expand public participation in rulemaking in OIRA’s July 19, 2023 memo on Broadening Public Participation and Community Engagement in the Regulatory Process, EPA is pursuing a robust stakeholder engagement process, consulting with energy workers, communities with environmental justice concerns, environmental justice leaders, industry, grid operators, and all interested parties to help develop these proposals. EPA opened a non-regulatory docket and issued framing questions on March 26, 2024 and held a public forum on May 17, 2024, to gather input on ways to design greenhouse gas emissions regulation for existing combustion turbine EGUs; the docket was closed on May 28, 2024.