In a series of SO2 NAAQS preliminary decisions issued to various states on Feb. 16, the U.S. Environmental Protection Agency said in the Wisconsin decision that SO2 scrubbers on Wisconsin Power and Light‘s Columbia coal plant have allowed the area around the plant to be declared in attainment.
EPA must designate areas as either “unclassifiable,” “attainment,” or “nonattainment” for the 2010 one-hour sulfur dioxide (SO2) primary national ambient air quality standard (NAAQS). The CAA defines a nonattainment area as one that does not meet the NAAQS or that contributes to a violation in a nearby area. An attainment area is defined as any area other than a nonattainment area that meets the NAAQS. Unclassifiable areas are defined as those that cannot be classified on the basis of available information as meeting or not meeting the NAAQS.
Wisconsin submitted updated recommendations in September 2015, ahead of a July 2, 2016, deadline for EPA to designate certain areas established by the U.S. District Court for the Northern District of California. This deadline is the first of three deadlines established by the court for EPA to complete area designations for the 2010 SO2 NAAQS.
Columbia County, Wisconsin, contains a stationary source that according to EPA’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO2 or more than 2,600 tons of SO2 and had an annual average emission rate of at least 0.45 pounds of SO2 per one million British thermal units (lbs SO2/MMBTU). As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement,” which would exclude it from consideration.
Specifically, in 2012 the Wisconsin Power and Light’s Columbia Energy Center (WPL-Columbia) emitted 24,599 tons of SO2, and had an emissions rate of 0.60 lbs SO2/MMBTU. Pursuant to the March 2015 court-ordered schedule, EPA must designate the area surrounding the facility by July 2, 2016.
WPL-Columbia has two coal-fired boilers. As of Jan, 1, 2015, the facility’s SO2 emissions are controlled by dry flue gas desulfurization and the facility is subject to a federally enforceable limit of 3,286 tons per year (tpy) and 0.075 lb/MMBTU on a 30-day rolling average. Wisconsin performed its Columbia County SO2 analysis with emissions based on these controls and limits.
“In its submission, Wisconsin recommended that the area surrounding WPL-Columbia, specifically the entirety of Columbia County, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area of analysis where maximum concentrations of SO2 are expected,” said EPA. “This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD, analyzing maximum potential emissions. After careful review of the state’s assessment, supporting documentation, and all available data, EPA agrees that the area is attaining the standard, and intends to designate Columbia County as unclassifiable/attainment.”