Air Quality State Implementation Plans; Approvals and Promulgations: Montana; Columbia Falls, Kalispell and Libby PM10 Nonattainment Area Limited Maintenance Plan and Redesignation Request

The Environmental Protection Agency (EPA) is approving the Limited Maintenance Plan (LMP) for the Columbia Falls, Kalispell and Libby nonattainment areas (NAAs) and the State's request to redesignate the Columbia Falls, Kalispell and Libby NAAs from nonattainment to attainment for the 1987 24-hour particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM<INF>10</INF>) National Ambient Air Quality Standard (NAAQS). Additionally, the EPA is determining that the Libby and Kalispell NAAs have attained the PM<INF>10</INF> NAAQS based on monitoring data from calendar years 2016-2018. On January 31, 2011, the EPA determined that the Columbia Falls NAA attained the PM<INF>10</INF> NAAQS. The EPA is also approving the Columbia Falls, Kalispell and Libby LMP as meeting the appropriate transportation conformity requirements. The EPA is taking this action pursuant to the Clean Air Act (CAA).