The Environmental Protection Agency (EPA) is proposing to approve, under the Clean Air Act (CAA), a revision to the Ohio State Implementation Plan (SIP) intended to provide for attainment of the 2010 primary, health-based 1-hour sulfur dioxide (SO<INF>2</INF>) national ambient air quality standard (NAAQS or standard) for the Muskingum River SO<INF>2</INF> nonattainment area. This SIP revision (hereinafter referred to as Ohio's Muskingum River SO<INF>2</INF> attainment plan or plan) includes Ohio's attainment demonstration and other attainment planning elements required under the CAA. EPA proposes to find that Ohio has appropriately demonstrated that the plan provides for attainment of the 2010 1-hour primary SO<INF>2</INF> NAAQS in the Muskingum River, Ohio nonattainment area and that the plan meets the other applicable requirements under the CAA. EPA is also proposing to incorporate by reference Ohio's Director's Final Findings and Orders (DFFOs), issued on May 23, 2023, into the Ohio SIP. The DFFOs set forth additional requirements at Globe Metallurgical (Globe) to verify appropriate source characterization for modeling purposes.