On May 1, 2012, the United States Environmental Protection Agency (EPA) announced final designations for the 2008 ground-level ozone standard. The 2008 ozone standard, which is 75 parts per billion (ppb) over an eight-hour period, strengthened the previous standard of 84 ppb.
EPA designated the entire state of Wisconsin, except for Sheboygan County, as being in attainment with the 2008 ozone standard (though a final decision will not be made for Kenosha County until the end of May 2012). According to the Wisconsin Department of Natural Resources, this is the smallest area of nonattainment in Wisconsin since EPA began the implementation of the ozone program more than 30 years ago - a testament to the significant decrease in ozone levels across the state over that period. The attainment designation across most of Wisconsin means an eased permitting and regulatory burden for sources subject to the Clean Air Act.
Sheboygan County was designated as "marginal nonattainment." Regulatory impacts of this designation include air emission inventory reporting, more stringent emissions controls for new sources and modifications to existing sources, requirements for sources to obtain VOC and NOx emissions offsets on a 1.1 to 1 basis from within the same nonattainment area, and consideration of reasonably available control measures (RACM).
A map of EPA's final ozone designations is available here: http://www.epa.gov/ozonedesignations/2008standards/final/region5f.htm
An issue to watch in coming years will be EPA's approach to developing and implementing an even stricter ozone standard, which, if promulgated, would require revisiting these ozone designations. EPA had been working on a stricter standard but suspended its efforts in September 2011.
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