Montana Department of Environmental Quality About Us Permitting & Operator Assistance Public Participation

Plan and Rule Development 

Program Overview

The Analysis and Planning Section is responsible for developing comprehensive plans (also known as State Implementation Plans (SIPs)) to reduce air pollution, and developing rules that set requirements on air emissions for both individuals and industry in Montana.



Air Program Contacts

Planning - Administrative Rules and State Implementation Plan
(406) 444-9741

Meteorological Services & Smoke Forecasting
(406) 444-0283

Main line - (406)444-3490 


Montana State Implementation Plans (SIPs)

EPA Region 8 Approved SIPs


Although the 1990 Clean Air Act (Act) is a federal law covering the entire nation, state and local air pollution control agencies (Agency) do much of the work to fulfill the requirements of the Act. For example, an Agency would hold a local hearing on a permit application by a power or chemical plant or take the lead in assessing a penalty to a company for violating an air pollution standard. Additionally, an Agency would develop community air pollution control programs to address automobile emissions, outdoor burning, road dust, or similar sources of air pollution.

Under the Act, the U.S. Environmental Protection Agency (EPA) sets Standards for air pollutants. These Standards ensure that all Americans have the same basic level of health and environmental protection. EPA makes regulations to control sources of air pollution. The Act allows Agencies to adopt and enforce more protective air pollution regulations than EPA. However, Agencies are not allowed to have weaker air pollution regulations than those established by EPA.

Because air pollution control problems often require special understanding of such factors as local industries, geography, housing patterns, and economic constraints, Agencies are better suited to regulate sources of air pollution than EPA. The Act recognizes this fact and confers upon Agencies the primary responsibility for assuring that air pollution never exceeds the Standards.

Agencies develop and maintain air pollution control plans frequently referred to as State Implementation Plans, or 'SIPs'. These control plans explain how an Agency will protect against air pollution under the Act. When referring to a state's SIP in general, it is defined as the collection of programs, policies and rules that Agencies use to attain and maintain the primary and secondary National Ambient Air Quality Standards (Standards). EPA must approve each SIP, and if a SIP fails in some way to protect the Standards, EPA may reject an Agency's SIP and assume administration of any specific portion of the Act in that state and/or develop its own implementation plan for the state.

Nonattainment Area Maps:

The following files may be viewed using a PDF Viewer of your choice. Use the readers "Zoom Function" for a close up view. Some Files are large and may take time to download; as well as load into the reader.

Montana State PM-2.5 Nonattainment Area
Montana State PM-10 Nonattainment Areas
Montana Federal PM-10 Nonattainment Areas
Montana State Carbon Monoxide Nonattainment Areas
Montana State Lead Nonattainment Area
Montana State Sulfur Dioxide Nonattainment Areas

The links below take you to the specific statutes and rules that are used to regulate the air quality permitting program in Montana.

Administrative Rules of Montana

Administrative Rules of Montana - Title 17

Administrative Rulemaking Notices

  • ARM Title 17, Chapter 8, Air Quality
  • ARM Title 17, Chapter 74, Subchapters 3 and 4, Asbestos Control
  • ARM Title 17, Chapter 80, Air and Water Quality - Tax Certification

Regional Haze

The Federal Clean Air Act established a program of visibility protection in 156 national parks and wilderness areas across the United States. These are referred to as "Mandatory Class I Federal Areas." Montana is home to 12 Mandatory Class I Federal Areas, including Glacier National Park, the Bob Marshall Wilderness Area, and many others. These areas are managed by three different federal agencies, the U.S. Forest Service, Fish and Wildlife Service, and National Park Service.

The goal of visibility protection is to ensure that the number days with impaired visibility at Class I areas are declining over time, and to make sure the clearest days at Class I areas stay clear and don't degrade. The U.S. Environmental Protection Agency (EPA) published a set of regulations in the late-1990s that aim to reduce the amount of visibility-impairing particles in the air over time. This set of regulations is called the Regional Haze Rule (RHR). The RHR calls for state and federal agencies to work together to improve visibility in Mandatory Class I Federal Areas.

The RHR sets a goal of reducing haze in each Class I Area to a level that is considered natural, meaning no particles from man-made sources are contributing to haze, by the year 2064.

In order to track changes in visibility, EPA set a starting point, or baseline - the level of visibility in the years 2000-2004 - against which visibility improvements are measured. The regulations require gradual improvements in visibility over time such that each Class I Area will achieve its calculated natural visibility goal by the year 2064.

These projected improvements form a straight line, what is often referred to as a “glide path,” between the 2000-2004 baseline period and the 2064 natural conditions. Due to the unique conditions in different parts of the country, each Class I Area has a different baseline and a different estimate of natural visibility conditions.

Actions that Reduce Haze

To improve visibility, often states look to control emissions of the pollutants that contribute to haze. As described above, the particles that cause haze come from a wide variety of places. Reducing haze means reducing the total amount of particulate matter being emitted or formed in the air.

The RHR directed states to develop and implement plans to reduce particulate pollution. These plans are expected to contain specific control measures for emission sources that were determined to be causing or contributing to haze in Class I Areas.

Such measures might take the form of direct limits on the amount of emissions allowed from a particular source. For example, a manufacturing facility might be required to reduce its total tons of nitrogen dioxide (NOx) emissions. The facility could achieve the limit in a number of ways, including installing new technology designed to remove NOx. Pollution control technologies are always advancing and improving due to continual research and pressure from industries that need to comply with control measures or regulations. 

Other control measures may take the form of state or federal regulations that contribute to a general reduction of haze-causing pollutants across an entire sector. For example, when EPA revises a National Ambient Air Quality Standard, many facilities across the country must evaluate how best to reduce their emissions. Another such example is federal standards for automobile fuel efficiency. These fuel efficiency standards contribute to decreasing NOx emissions from cars and trucks.

Emission reductions can also come in the form of source shutdowns and retirements, as industries decline and sources reach the end of their lifespan. 

Second Implementation Period

States show progress toward the 2064 goal by creating regional haze plans every 10 years. Montana is currently analyzing haze in our state in the 'second implementation period', or the second 10-year phase. To start, we have to know how much pollution is impacting Class I Areas and where that pollution may be coming from.

Special ambient air monitors placed near Class I Areas are used to measure the amount of haze-causing particles present. This data is used as a starting point in planning, and in our case, Montana has determined that emissions of oxides of nitrogen (NOx) and sulfur dioxide (SO2) continue to impact our Class I Areas.  Using atmospheric modeling tools, we can trace the emissions back to a source or set of sources. This information helps us to formulate a plan that may require emission controls on sources to help reduce haze-causing pollution over time. 

The second implementation period is from 2018 - 2028. Montana must show that progress toward natural conditions is being made. This is accomplished through implementing a long-term strategy that ensures reasonable progress by 2028 will be met. The plan must include:

  • Ambient data analysis - identify the 20% most anthropogenically impaired days and the 20% clearest days and determine baseline (2000-2004), current, and natural visibility conditions for each Class I Area within the Montana
  • Determination of Affected Class I Areas in Other States - Determine which Class I Area(s) in other states may be affected by Montana's emissions
  • Selection of sources for analysis - Select the emission sources for which an analysis of emission control measures will be completed in the second implementation period
  • Characterization of factors for emission control measures - Identify potential emission control measures for the selected sources, develop data on the four statutory factors and on visibility benefits if they will be considered
  • Decisions on what control measures are necessary to make reasonable progress - Consider the four statutory factors, the five required factors listed in section 51.308(f)(2)(iv), and optionally, visibility benefits, and decide on emission controls for incorporation into the Long Term Strategy (LTS). Consider measures adopted by other contributing state, including all measures that have been agreed upon through interstate consultation
  • Regional scale modeling of the LTS to set the reasonable progress goals for 2028 - Determine the visibility conditions in 2028 that will result from implementation of the LTS and other enforceable measures to set the reasonable progress goals for 2028. 
  • Progress, degradation, and glidepath checks  - Demonstrate that there will be an improvement in visibility (and no degradation of visibility) as a result of the LTS
  • Glidepath check for out-of state Class I Areas that Montana sources may reasonably be anticipated to contribute to visibility impairment

Montana 'screened in' seventeen industrial sources for further analysis. Sixteen sources provided Montana with the statutorily-required four factor reports. 

Talen Montana LLC - Colstrip Steam Electric Station  •  Weyerhaeuser NR Columbia Falls  •  Weyerhaeuser NR Kalispell  •  Ash Grove Cement  •  GCC Trident, Inc.  •  Yellowstone Energy Limited Partnership  •  Roseburg Forest Products  •  Colstrip Energy Ltd Partnership  •  Graymont Western US  •  Montana Sulphur & Chemical •  Phillips 66 – Billings Refinery  •  ExxonMobil – Billings Refinery  •  CHS, Inc. - Laurel Refinery  •  F.H. Stoltze Land & Lumber  •  Sidney Sugars Inc.  •  Northern Border Pipeline Co.  •  Montana-Dakota Utilities - Lewis and Clark Station

Montana's 2017 Progress Report

Montana submitted a progress report to the EPA in 2017. This document evaluates visibility progress in Montana since the baseline years of 2000-2004 and, more specifically, progress since the Montana FIP was published in 2012. It provides a 5-year update on the current status of visibility at the Class I Areas affected by emissions from Montana sources of air pollution

2017 Montana Progress Report

2012 Regional Haze FIP

For a variety of reasons, including available staff time and the cost of performing the required technical analyses, Montana told EPA the state would not submit a plan to comply with the rule. As a result, EPA published a Federal Implementation Plan or "FIP" for Montana in 2012.

Proposed 2012 Regional Haze FIP

Final 2012 Regional Haze FIP

Upcoming Activities

Montana has posted the Draft Regional Haze State Implementation Plan (RH SIP) for the Second Planning Period for public review and comment. The comment period begins on Thursday, February 3, 2022 and ends Monday, March 21, 2022. 

Interested persons may view the proposed SIP revisions on DEQ's Public Comment page ( or may call DEQ at 444-5287 to have copies made available for their inspection. 

Please submit written comments on the RH SIP to DEQ by:

  • addressing them to Rhonda Payne, MT DEQ AQB, 1520 E 6th Avenue, Helena, MT 59620-0901;
  • faxing them to 406-444-1499; or
  • sending them via email addressed to

In addition, DEQ will hold a Public Hearing on the RH SIP on March 18, 2022. The meeting will be hybrid, with both in-person and online attendance options.  

In-person: Room 40 of the Montana DEQ – Lee Metcalf Building (1520 E. 6th Avenue, Helena, MT 59601) from 1:30 p.m. to 3:00 p.m.


Microsoft Teams meeting

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+1 406-318-5487,,687809787#   United States, Billings
Phone Conference ID: 687 809 787#


UPDATE 3/1/22: Montana's Draft RH SIP includes federal land manager (FLM) comments received after the required FLM comment period. Since the end of that review period, Montana has received initial feedback from EPA on Montana's Draft RH SIP. Official EPA comments will be received during the public comment period. However, this initial feedback may be helpful for public reviewers during the public comment period. 

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