Approval and Promulgation of Implementation Plans; Montana; Thompson Falls PM10
The Environmental Protection Agency (EPA) is approving the Limited Maintenance Plan (LMP) submitted by the State of Montana to EPA on November 4, 2021, for the Thompson Falls Moderate nonattainment area (NAA) for particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM<INF>10</INF>) and concurrently redesignating the NAA to attainment for the 24-hour PM<INF>10</INF> National Ambient Air Quality Standard (NAAQS). In order to approve the LMP and redesignation, EPA determined that the Thompson Falls NAA has attained the 1987 24-hour PM<INF>10</INF> NAAQS of 150 [mu]g/m\3\. This determination is based upon monitored air quality data for the PM<INF>10</INF> NAAQS during the years 2015 through 2020. The EPA is taking this action pursuant to the Clean Air Act (CAA).