(a) Approval. On April 21, 1997, the Iowa Department of Natural Resources (IDNR) submitted a maintenance plan and redesignation request for the Muscatine County nonattainment area for the 1971 SO2 national ambient air quality standard (NAAQS). The maintenance plan and redesignation request satisfy all applicable requirements of the Clean Air Act.

(b) Determination of attainment by the attainment date. As of May 9, 2022, the EPA has determined that the Muscatine, Iowa SO2 nonattainment area has attained the 2010 1-hour SO2 primary NAAQS by the applicable attainment date of October 4, 2018.