Final rule · 2026-18334

Air Plan Approvals; Indiana; Prong 4 (Visibility) for the 2015 Ozone National Ambient Air Quality Standard

The U.S. Environmental Protection Agency (EPA) is approving a portion of Indiana's State Implementation Plan (SIP) submission regarding the infrastructure requirements in Clean Air Act (CAA) section 110 for the 2015 ozone National Ambient Air Quality Standards (NAAQS). The infrastructure requirements are designed to ensure that the structural components of each State's air quality management program are adequate to meet the State's responsibilities under the CAA. The EPA finds that Indiana's infrastructure submission fulfills CAA requirements for a State's SIP to contain adequate provisions prohibiting emissions that will interfere with required visibility protection measures in any other State's SIP. The EPA proposed to approve this action on April 10, 2026, and received no adverse comments.