Approval and Promulgation of Air Quality Implementation Plans; Montana; Billings/Laurel Sulfur Dioxide State Implementation Plan

EPA is proposing to partially approve, conditionally approve and partially disapprove the Billings/Laurel sulfur dioxide (SO2) State Implementation Plan (SIP) revisions submitted by the State of Montana in response to a SIP Call. EPA is also proposing a regulatory scheme for sanctions. The SIP revisions establish, and require seven sources to meet and monitor compliance with, emission limitations for SO2 emissions in the Billings/Laurel area. The intended effect of this action is to make federally enforceable those provisions that EPA is proposing to approve, to conditionally approve those provisions that the State has committed to correct, to disapprove those provisions that are not approvable, and to establish the sequence of sanctions if EPA's proposed disapproval becomes a final action. EPA is taking this action under sections 110 and 179 of the Clean Air Act (Act).