Air Plan Approval; Illinois; 2015 Ozone Moderate and Serious Reasonably Available Control Technology Update

The U.S. Environmental Protection Agency (EPA) is proposing to approve revisions to 35 Illinois Administrative Code (IAC) parts 217, 218, and 219 into the Illinois State Implementation Plan (SIP). The Illinois Environmental Protection Agency (Illinois or Illinois EPA) submitted these revisions on December 18, 2024, and May 12, 2025, supplemented their submittal on August 13, 2025, for Moderate Reasonably Available Control Technology (RACT). The EPA is proposing to approve 35 IAC parts 217, 218, and 219 as satisfying the Moderate Volatile Organic Compound (VOC) RACT and NO<INF>X</INF> RACT requirements as well as Serious NO<INF>X</INF> RACT requirements for the Chicago, IL (Cook County, DuPage County, Grundy County, Kane County, Kendall County, Lake County, McHenry County, and Will County) and Metro-East St. Louis (Madison County, Monroe County, and St. Clair County) nonattainment areas under the 2015 ozone National Ambient Air Quality Standard (NAAQS or standard).