EPA Supplemental Amendment for the Fourth Round of SO2 Area Designations

On April 8, 2021, the U.S. Environmental Protection Agency (EPA) modified one of its area designations for the 2010 sulfur dioxide (SO₂) primary National Ambient Air Quality Standard (NAAQS). Specifically, EPA changed the December 2020 nonattainment designation for portions of Outagamie County, Wisconsin to attainment/unclassifiable. The portions of Outagamie County affected by this cover Outagamie County except Oneida Township (which includes Oneida Reservation), Oneida Off-Reservation Trust Land, and noncontiguous portions of Seymour Township adjoining Oneida Nation Tribal Lands. This action supplements the fourth and final round of 2010 SO₂ NAAQS designations and is based on the most recent 3 consecutive years (i.e., 2018-2020) of quality assured, certified ambient air quality monitoring data.