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

Air Quality | SIP Proposed Update - Whitefish PM10 Limited Maintenance Plan | Comment period ends October 11, 2026

  • September 10 2026

Montana Department of Environmental Quality (DEQ) is inviting comments on its proposal to update the State Implementation Plan (SIP) to reference the revised Whitefish PM10 Limited Maintenance Plan.

The Whitefish PM10 Limited Maintenance Plan (LMP) has been revised to allow the decommission of an aging monitor that no longer meets site criteria. There has not been an exceedance of the National Ambient Air Quality Standard (NAAQS) for particulate matter with an aerodynamic diameter of 10 micrometers (PM10) in the Flathead Valley in over 30 years. The current action is to refer to the updated LMP in the SIP.

Public comments will be accepted from Thursday, September 10th until 5:00 p.m. October 11, 2026. If DEQ receives a request for public hearing, a public hearing on this matter will be scheduled, the time for that hearing will be announced, and an additional 30-day time period for submitting comments will be scheduled. All comments received will be included when the SIP revision is reviewed and submitted to the EPA.

  

Associated Materials: 

 

Comment Period Ends:

  • Sunday October 11, 2026, at 5:00 p.m. 

 

Send Comments To:

  • Mail to :
    • DEQ Air Quality Bureau Planning Section
      P.O. Box 200901
      Helena, Montana 59620-0901

OR

 

DEQ will make reasonable accommodations for people with disabilities who wish to participate in this SIP revision process or need an alternative accessible format of this notice. If you require accommodation, contact the department no later than 5:00 p.m. on October 5, 2026, to advise us of the nature of the accommodation that you need. Please contact the Department of Environmental Quality at P.O. Box 200901, Helena, Montana 59620-0901; phone (406) 444-3490; or e-mail deqair@mt.gov .

Tags: Public Comment and Air