In this action, EPA approves the State implementation plan (SIP) revisions submitted by the State of Montana on March 15, 1995 to satisfy the Federal Clean Air Act requirement to submit contingency measures for the Libby moderate PM<INF>10 (particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers) nonattainment area. The March 15, 1995 submittal also recodified the Lincoln County regulations. In addition, EPA is approving a SIP revision submitted by the Governor of Montana on May 13, 1996, which included revisions to the Lincoln County regulations regarding open burning and other minor administrative amendments. EPA is approving these SIP revisions because they are consistent with the applicable requirements of the Clean Air Act, as amended (Act), and EPA guidance.