Determinations of Attainment of the 1997 Annual Fine Particulate Matter Standards for the Libby, Montana Nonattainment Area

The Environmental Protection Agency (EPA) is proposing to make two separate and independent determinations regarding the Libby, Montana nonattainment area for the 1997 annual fine particulate matter (PM2.5) National Ambient Air Quality Standard (NAAQS). First, EPA is proposing to determine that the Libby nonattainment area attained the 1997 annual PM2.5 NAAQS by the applicable attainment date, April 2010. This proposed determination is based on quality-assured and certified ambient air quality data for the 2007- 2009 monitoring period. Second, EPA is proposing that the Libby nonattainment area has continued to attain the 1997 annual PM2.5 NAAQS, based on quality-assured and certified ambient air quality data for the 2012-2014 monitoring period. Based on the second determination, EPA also proposes to suspend certain nonattainment area planning obligations. These determinations do not constitute a redesignation to attainment. The Libby nonattainment area will remain designated nonattainment for the 1997 annual PM2.5 NAAQS until such time as EPA determines that the Libby nonattainment area meets the Clean Air Act (CAA) requirements for redesignation to attainment, including an approved maintenance plan. These proposed actions are being taken under the CAA.