On March 7th, EPA proposed to change the attainment designation for the 1-hour SO2 National Ambient Air Quality Standard in Billings, Montana. A limited area surrounding the former PPL Corette power plant was designated as not attaining the 2010 1-hour SO2 NAAQS in August of 2013 following a recommendation by then-Governor Schwieitzer that all of Montana should be designated as attaining the standard.
Analyses conducted by the Montana Department of Environmental Quality indicated that high SO2 concentrations in the past had resulted primarily from a limited set of exceptional events and from emissions originating with the Corette coal-fired power plant, which had operated for nearly 50 years on the southern edge of Billings. The plant was closed and dismantled in 2015. Governor Bullock submitted a request in December of 2015 for redesignation of the nonattainment area to a designation of attainment.