Proposed rule · 2026-23026

Approval and Promulgation of Air Quality Implementation Plans; Michigan; Withdrawal of the Federal Implementation Plan for the Detroit Sulfur Dioxide Area

The U.S. Environmental Protection Agency (EPA) is proposing to withdraw the Federal Implementation Plan (FIP), promulgated on October 12, 2022 (the "2022 FIP"), for attaining the 2010 1-hour primary sulfur dioxide (SO<INF>2</INF>) National Ambient Air Quality Standard (NAAQS) in the Detroit area. On May 19, 2025, the EPA approved a revision to Michigan's State Implementation Plan (SIP) for attaining the 2010 1-hour primary SO<INF>2</INF> NAAQS in the Detroit area, rendering the 2022 FIP duplicative. The EPA is proposing this action pursuant to Clean Air Act (CAA) section 110.