Clean Air Act Approval and Promulgation of State Implementation Plan for Montana; Butte; PMINF10 Contingency Measures and Revisions to the Attainment and Maintenance Demonstrations

EPA approves the State implementation plan (SIP) revisions submitted by the State of Montana with a letter dated August 26, 1994. This submittal addresses, for the Butte moderate PM<INF>10 nonattainment area, the Federal Clean Air Act requirement to submit contingency measures for particulate matter with an aerodynamic diameter less than or equal to a nominal [[Page 15057]] 10 micrometers (PM<INF>10) for areas designated as nonattainment for the PM<INF>10 National Ambient Air Quality Standards (NAAQS). This submittal also includes revisions to the attainment and maintenance demonstrations for the moderate PM<INF>10 nonattainment area SIP for Butte due to the inclusion of new emission limits in a revised air quality permit for Montana Resources, Inc. Since the SIP adequately addresses the requirement for contingency measures and, with the new emission limits for Montana Resources, Inc., still adequately demonstrates attainment and maintenance of the PM<INF>10 NAAQS in Butte, EPA approves these revisions.