Air Plan Approvals; Indiana; Prong 4 (Visibility) for the 2015 Ozone National Ambient Air Quality Standard
- Published
- Sep 9, 2026
- Effective
- Oct 9, 2026
- Citation
- 91 FR 57262
- Docket
- EPA-R05-OAR-2018-0788, FRL-13249-02-R5
Final rule.
Summary
The Environmental Protection Agency (EPA) has issued a final rule that formally approves Indiana’s submission of a portion of its State Implementation Plan (SIP) that addresses “Prong 4” – the visibility protection requirements – for the 2015 ozone National Ambient Air Quality Standard. The rule confirms that Indiana’s plan contains the necessary measures to prevent emissions that would harm visibility in other states, thereby satisfying the Clean Air Act’s infrastructure obligations for the ozone standard. The action was taken by the EPA and applies to Indiana’s state‑level air‑quality program. It does not create new regulations for the public or industry; rather, it validates that Indiana’s existing provisions meet federal standards, allowing the state to continue implementing its approved visibility‑protection strategies. The rule was published in the Federal Register on September 9, 2026 (91 FR 57262) and became effective on October 9, 2026. The EPA had previously proposed the approval on April 10, 2026 and received no adverse comments, so the comment period closed without opposition. With the approval now final, the approved portion of Indiana’s SIP is officially part of the federal air‑quality framework, and the state can proceed with enforcement and any future updates needed to maintain compliance with the ozone standard.
AI-generated summary — verify against the Federal Register text.
Official abstract
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.
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