Approval and Promulgation of State Implementation Plans and Designation of Areas for Air Quality Planning Purposes: State of Oregon

The Environmental Protection Agency (EPA) is redesignating the Portland, Oregon nonattainment area to attainment for the carbon monoxide (CO) national ambient air quality standard (NAAQS) and approving a maintenance plan that will insure that the area remains in attainment. Under the Clean Air Act (CAA) as amended in 1990, designations can be revised if sufficient data is available to warrant such revisions. In this action, EPA is approving the Oregon Department of Environmental Quality's (DEQ's) request because it meets the redesignation requirements set forth in the CAA. As part of this action, EPA is approving two related State Implementation Plan (SIP) revisions: the 1990 base year emissions inventory, as meeting the requirements of section 187(a)(1) of the CAA; and the 1991 attainment year emissions inventory, as meeting the periodic inventory requirements of section 187(a)(5) of the CAA.