Approval and Promulgation of Implementation Plans; Montana; Butte PM10
The Environmental Protection Agency (EPA) is proposing to fully approve the Limited Maintenance Plan (LMP) submitted by the State of Montana to EPA on March 23, 2020, for the Butte 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 redesignate 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 is proposing to determine that the Butte, MT NAA has attained the 1987 24- hour PM<INF>10</INF> NAAQS of 150 [micro]g/m\3\. This determination is based upon monitored air quality data for the PM<INF>10</INF> NAAQS during the years 2014-2018. EPA is taking this action pursuant to the Clean Air Act (CAA).