EPA Greenlights Montana's Plan to Clear Hazy National Park Skies
Published Date: 11/28/2025
Rule
Summary
The EPA is giving a thumbs-up to Montana’s updated plan to clear up regional haze and improve air quality for the next few years. This means cleaner skies for everyone in Montana, with rules kicking in by December 29, 2025. The plan also includes steps to keep ozone pollution in check, helping protect health without extra costs for businesses or residents.
Analyzed Economic Effects
4 provisions identified: 4 benefits, 0 costs, 0 mixed.
Montana Approved Regional Haze Plan
If you live in Montana, the EPA approved Montana’s regional haze State Implementation Plan to improve visibility and air quality in Class I Federal areas. The approval is final and takes effect on December 29, 2025, and covers pollutants including particulate matter (PM) and precursors like SO2 and NOX.
Ozone Visibility (Prong 4) Approval
If you live in Montana, the EPA approved the prong 4 visibility portion of Montana’s October 1, 2018, Infrastructure SIP for the 2015 ozone standard to help keep ozone pollution in check. This approval is effective December 29, 2025, and the EPA states it helps protect health without imposing extra costs on businesses or residents.
No New Federal Costs for Small Businesses
If you run a small business or are self-employed in Montana, EPA approved the SIP and certified that this action does not impose additional Federal requirements beyond state law and does not have a significant economic impact on a substantial number of small entities. The rule is effective December 29, 2025.
No SIP Approval on Indian Reservation Lands
The EPA’s approval does not apply on any Indian reservation land or other areas where a Tribe has demonstrated jurisdiction. In those tribal areas, the rule will not impose substantial direct costs on Tribal governments or preempt Tribal law.
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