Approval and Promulgation of Air Quality Implementation Plans; Montana; Attainment Plan for Libby, MT PM2.5 Nonattainment Area and PM10 State Implementation Plan Revisions

EPA is approving the State Implementation Plan (SIP) revision submitted by the State of Montana on March 26, 2008. Montana submitted this SIP revision to meet Clean Air Act requirements for attaining the 1997 annual fine Particulate Matter (PM<INF>2.5</INF>) national ambient air quality standard (NAAQS) for the Libby nonattainment area. The plan revision, herein called an "attainment plan," includes an attainment demonstration, an analysis of Reasonably Available Control Technology and Reasonably Available Control Measures (RACT/RACM), base-year and projection year emission inventories, and contingency measures. The requirement for a Reasonable Further Progress (RFP) plan is satisfied because Montana projected that attainment with the 1997 annual PM<INF>2.5</INF> NAAQS will occur in the Libby nonattainment area by April 2010. In addition, EPA is also approving revisions to the Lincoln County Air Pollution Control Program submitted by Montana on June 26, 2006, for inclusion into Libby's attainment plan for purposes of the 1987 PM<INF>10</INF> NAAQS. This submittal contains provisions, including contingency measures, for controlling both PM<INF>10</INF> and PM<INF>2.5</INF> emissions from woodstoves, road dust, and outdoor burning. Finally, EPA is finding on- road directly emitted PM<INF>2.5</INF> and oxides of nitrogen (NO<INF>X</INF>) in the Libby, Montana nonattainment area insignificant for regional transportation conformity purposes. As a result of this finding the Libby, Montana nonattainment area will not have to perform a regional emissions analysis for either direct PM<INF>2.5</INF> or NO<INF>X</INF> as part of future conformity determinations for the 1997 annual PM<INF>2.5</INF> NAAQS.