EPA is partially approving and partially disapproving State Implementation Plan (SIP) revisions submitted by the State of South Dakota on May 6, 1999 and June 30, 2000. The revisions modify the State's air quality rules so they are consistent with federal rules and clarify existing provisions. EPA is also removing from the SIP or not approving into the SIP, certain provisions of the State's air quality rules because they are not related to attainment or maintenance of the National Ambient Air Quality Standards (NAAQS) and are not appropriate for inclusion in the SIP. This action is being taken under section 110 of the Clean Air Act.