Montana’s environmental regulatory landscape remains stable for 2026 with some updates from the state agencies to refine climate evaluation procedures, clarify permitting frameworks, and adjust to changing federal priorities. For Montana facilities, understanding these dynamics is essential to maintaining compliance and anticipating future regulatory impacts.
Montana Regulatory Hot Topics
Montana Environmental Policy Act (MEPA) Greenhouse Gas Assessment Guidance and Its Implications
Montana issued final MEPA Greenhouse Gas Assessment Guidance to assist state agencies in carrying out new greenhouse gas (GHG) evaluation requirements. The guidance outlines when state agencies must evaluate GHG emissions and provide consistent technical methods for doing so. Projects involving fossil fuel activities (i.e. coal mining, oil and gas drilling, production, compression, or combustion) are now explicitly required to include a GHG assessment. Other types of projects may also require GHG consideration when emissions or ecological impacts are potentially significant. Learn more about these updates in our recent article, “DEQ Issues Final Greenhouse Gas Assessment Guidance”.
Treatment of Startup, Shutdown, and Maintenance (SSM) Emissions
The Montana Department of Environmental Quality (DEQ) is aligning more closely with federal interpretations of the Clean Air Act regarding Startup, Shutdown, and Maintenance (SSM) emissions. Historically, some permit conditions allowed for exemptions from compliance when units were not in steady state operation, but federal courts have clarified that emission limits must apply at all times. In response, the DEQ now encourages facilities to include detailed SSM plans in their permit applications, documenting how emissions during these periods will be minimized and monitored.
This shift makes SSM considerations integral to future permit renewals and modifications. A well‑developed SSM plan strengthens a facility’s compliance position and creates a more defensible permit record.
Clarifying Incinerator Permitting Under Montana Statutes
Montana maintains unique statutory requirements for incinerators under MCA 75‑2‑215, mandating air permits for any incinerator and requiring accompanying health risk assessments. Incinerators include medical waste units, crematoriums, thermal oxidizers, and similar equipment that uses combustion to reduce the amount of a waste product. While the statute exempts certain industrial flares, DEQ has historically required the incinerator permitting processes for most flares regardless of the exemption language.
To address years of inconsistent interpretation, DEQ is preparing updated guidance defining what qualifies as an incinerator and when risk assessments are required. This clarity will be particularly important for facilities using portable thermal oxidizers or industrial flares.
PM2.5 Standard Changes and Montana’s Nonattainment Picture
The EPA lowered the annual fine particulate matter (PM2.5) National Ambient Air Quality Standard (NAAQS) from 12 micrograms per cubic meter (µg/m³) to 9 µg/m³ in 2024, prompting Montana to submit revised area designations. The Libby region remains an area of concern due to longstanding wintertime PM2.5 challenges from topographical trapping of emissions. Although the EPA has since announced plans to rescind the 9 µg/m³ standard, the rule remains in effect until official action is taken. Future PM2.5 rulemaking is uncertain, but facilities conducting air dispersion modeling, particularly major stationary sources, should expect continued scrutiny. Permitting challenges may arise as background concentrations, meteorological conditions, and cumulative impacts remain at the forefront of regulatory review.
Affirmative Defense Reinstated at Federal Level, Still Unsettled in Montana
In 2025, the D.C. Circuit Court reinstated the Title V affirmative defense for emergency exceedances, concluding that the EPA’s prior rescission was unjustified. While the defense protects facilities from penalties during qualified emergencies, it does not permit emissions exceedances; it merely provides a shield if strict documentation requirements are met.
Montana had already removed affirmative defense language from its own rules, and the DEQ has not yet reinserted it. Until the state completes rulemaking, or determines an alternate approach, the DEQ has indicated it will consider emergency defense claims on a case‑by‑case basis, increasing the importance of thorough recordkeeping.
Regional Haze Program Developments
Montana received final approval of its Regional Haze State Implementation Plan (SIP) in November 2025. Meanwhile, the EPA continues exploring broad revisions to the national Regional Haze Rule in an effort to simplify requirements and address inconsistencies across states. Litigation is ongoing in multiple circuits, meaning national SIP guidance may continue to evolve. Montana facilities potentially affected by visibility considerations should watch for future updates to federal implementation strategies.
Montana Reporting Updates and Reminders
Annual Emissions Inventory (February 15)
Montana requires registered and permitted sources to submit an Annual Air Emissions Inventory by February 15. Submissions occur through the Air Emission Inventory Entry System, and the DEQ has temporarily paused its planned transition to a new platform. Portable facilities must also report annual production data.
Annual Hazardous Waste Reporting (March 1)
Unlike the federal biennial reporting requirement, Montana mandates annual hazardous waste reports for both Large Quantity Generators (LQGs) and Small Quantity Generators (SQGs). Reports must include generator identification details, off‑site shipment information, transporter data, waste descriptions, hazard classifications, reduction efforts, and certified signatures. The state maintains its own hazardous waste fees, with online payment options and facility‑specific form submission requirements.
Tier II Chemical Inventory Reporting (March 1)
Montana requires Tier II emergency planning reports to be submitted through E‑Plan. While the state does not require additional fees, facilities must check whether local LEPCs or fire departments request direct submissions. Facilities should be aware of updated hazard categories under OSHA’s 2024 Hazard Communication Standard that take effect for the RY2026 reports due in 2027, significantly expanding the number of hazard classifications. Early review of updated SDSs is highly recommended.
Refrigerant Management and Chronic Leaker Reporting (March 1)
The EPA’s Refrigerant Management Rule continues to require reporting for regulated appliances containing at least 50 pounds of Class I or II ODS if leaks exceed 125% of full charge in a year. Beginning in 2027, similar chronic leak reporting will apply to HFCs and substitutes with global warming potential above 53, for leaks occurring in 2026.
Additional Air and Multi‑Media Submittals
Facilities must also track a variety of ongoing reporting and renewal deadlines throughout the year, including:
- Title V annual compliance certifications
- Title V semiannual monitoring reports
- NSPS and NESHAP periodic reports
- Stormwater Discharge Monitoring Reports
- SPCC reviews every five years
- Risk Management Program (RMP) resubmittals every five years
Because semiannual periods vary by permit, facilities should verify reporting windows in their individual permits.
Federal Updates Snapshot
EPA Enforcement Declines and Focus Shifts
EPA enforcement activity has dropped significantly in the past year, with only a single compliance advisory released in 2025 and historically low levels of litigation. Current priorities focus on imminent public health risks, illegal HFC imports, and select waste‑related concerns. Enforcement tied to methane emissions, environmental justice, or expanded oversight has been deemphasized by the current EPA administration.
Federal Deregulatory Efforts Intensify
EPA has initiated more than 30 deregulatory actions impacting oil and gas standards, electric power rules, wastewater effluent guidelines, and GHG reporting programs. Several methane rule compliance dates, originally set under NSPS OOOOb and OOOOc, have already been delayed until 2027 or later.
GHG Reporting and the Endangerment Finding Under Review
The federal GHG Reporting Program may be significantly scaled back. A 2025 proposal would eliminate reporting for nearly all source categories after reporting year 2024 and suspend Subpart W reporting until 2034. Additionally, EPA announced on February 12, 2026, a final rule that rescinds the 2009 GHG Endangerment Finding, a move that fundamentally affects greenhouse gas regulation nationwide. Litigation is virtually guaranteed on this action.
PFAS Oversight Continues to Expand
While many federal programs face rollback, PFAS or “forever chemicals” regulation remains an area of ongoing development. TRI reporting thresholds now cover more than 200 PFAS, CERCLA continues to classify PFOA and PFOS as hazardous substances, and stormwater and wastewater programs are incorporating new PFAS monitoring requirements. Drinking water rules have narrowed their scope but extended compliance timelines, reducing immediate burdens while maintaining long‑term expectations.
HFC Management Rule Now in Effect
Under 40 CFR Part 84, hydrofluorocarbons (HFCs) and refrigerant substitutes with global warming potential above 53 are now regulated with a January 1, 2026, effective date for most requirements. The rule is similar to the requirements for ODS appliances under 40 CFR Part 82, Subpart F, with some differences, including a lower capacity threshold of 15 pounds for leak repair requirements. For more information on refrigerant management, see our Refrigerant Management Services (ODS and HFC) webpage.
Key Takeaways
Montana’s 2026 regulatory outlook includes targeted developments that affect certain facilities. GHG evaluations under MEPA are now required for fossil fuel activities and may also apply to other projects at DEQ’s discretion if there are sources of GHG emissions. Additional areas of focus include continuous compliance with permit conditions during startup, shutdown, and maintenance activities, as well as clarifying policy about when incinerator permitting requirements are triggered. Montana has acted to align its rules with recent federal court decisions and EPA actions related to affirmative defense and PM₂.₅ planning, though continued federal litigation and evolving policy direction may require additional state refinement.
At the federal level, facilities face a landscape defined by deregulatory momentum, uncertain climate policy, and reduced enforcement, tempered by continued activity in PFAS, refrigerant management, and methane rule reconsiderations. For Montana operators, maintaining current reporting programs and staying aware of evolving regulatory requirements will be key to navigating the year ahead and positioning for future regulatory cycles.
Resources
- To stay current on our Montana reporting requirements, download a copy of the Montana annual reporting compliance calendar.
- For a copy of our slide deck from our recent presentation on 2026 Annual Compliance Reporting and Hot Topics in Montana reach out to Zoe Stone.
- For support with your upcoming reporting requirements or questions on regulatory changes in Montana, reach out to Ed Warner with Trinity’s Montana office.
