Indiana Ozone Nonattainment Sanctions Now Impose 2:1 Offsets on Lake and Porter County Expansion

IDEM issued its third consecutive Air Quality Action Day on July 14, covering Northwest, Central/East Central, and Western/West Central Indiana. The weather is temporary; the regulatory exposure underneath it is not. Lake and Porter Counties were reclassified from moderate to serious ozone nonattainment in December 2024, and Indiana missed the May 2025 SIP submission deadline to EPA.

That missed deadline is the consequence operators need to price in: any new or modified major source in Lake or Porter County now faces a 2:1 emissions offset requirement, you must retire two units of emissions for every one your project adds. That is a direct capital constraint on industrial expansion in Northwest Indiana. IDEM is also pulling ozone monitors out of the two counties in its 2026 plan, even as enforcement tightens. If you have a capital project or permit modification in the pipeline there, build the 2:1 offset into your cost model before you commit.