In this document, EPA is approving a December 19, 1994 request from the Governor of Wyoming to redesignate the Powder River Basin particulate matter attainment area in portions of Campbell and Converse Counties to exclude an area designated as the Kennecott/Puron Prevention of Significant Deterioration (PSD) Baseline area, pursuant to section 107 of the Clean Air Act (Act). EPA is designating the Kennecott/Puron PSD Baseline area as a separate particulate matter attainment area under section 107 of the Act. EPA is approving the State's redesignation request because the State has adequately followed the applicable Federal requirements and policy. Approval of the section 107 redesignation eliminates the minor source baseline date for particulate matter in the Powder River Basin area which was triggered by the submittal of a complete PSD permit application for the Kennecott/Puron facility.