The Environmental Protection Agency (EPA) is approving revisions to Minnesota's State Implementation Plan (SIP) for sulfur dioxide (SO<INF>2</INF>) in Air Quality Control Region (AQCR) 131. The EPA's action is based upon a revision request submitted by the State of Minnesota on April 24, 1997, which amends two State Administrative Orders for two Northern States Power facilities: Inver Hills and Riverside. The Orders are included as part of Minnesota's approved SIP to attain and maintain the National Ambient Air Quality Standard for sulfur dioxide.