Clean Air Act Approval and Promulgation of State Implementation Plans; Prevention of Significant Deterioration; Designation of Areas for Air Quality Planning Purposes; Montana, North Dakota, South Dakota, Utah, and Wyoming

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In this document, the EPA is proposing approval of revisions to the State Implementation Plans (SIPs) submitted by the States of Montana, North Dakota, Utah, and Wyoming. The submittals included revisions to the prevention of significant deterioration (PSD) permitting rules of these States mainly to address the replacement of the total suspended particulate (TSP) increments with increments for PM-10 (particulate matter 10 micrometers or less in diameter), but also to address other changes in the Federal PSD permitting regulations and to make other minor revisions. EPA is also proposing to delete the TSP area designation tables and to revise and/or create PM-10 area designation tables in 40 CFR part 81 for these States as well as for the State of South Dakota (which has been delegated authority to implement the Federal PSD regulations in 40 CFR 52.21). In the final rules section of this Federal Register, the EPA is acting on the States' SIP submittals in a direct final rule without prior proposal because the Agency views these submittals as noncontroversial and anticipates no adverse comments. A detailed rationale for the approval is set forth in the direct final rule. If no adverse