Proposed rule · 2026-03936

Air Plan Approvals; Illinois; Regional Haze Plan for the Second Implementation Period; Interstate Transport of Air Pollution for the 2012 PM2.5 and 2015 Ozone NAAQS

The Environmental Protection Agency (EPA) is proposing to approve the regional haze State Implementation Plan (SIP) revision submitted by the Illinois Environmental Protection Agency (Illinois EPA) on June 3, 2024, as satisfying applicable requirements under the Clean Air Act (CAA) and the EPA's Regional Haze Rule for the program's second implementation period. The EPA proposes to find that Illinois' regional haze SIP submission fulfills the requirement that States must periodically revise their long-term strategies for making reasonable progress towards the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility in mandatory Class I Federal areas. The EPA is also proposing to approve portions of Illinois' September 29, 2017, and May 16, 2019, infrastructure SIP submissions for the 2012 fine particulate matter (PM<INF>2.5</INF>) and 2015 ozone National Ambient Air Quality Standards (NAAQS), respectively. The EPA is proposing that Illinois' infrastructure submissions fulfill 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.