US EPA has proposed to reclassify the Chicago-Naperville, Illinois-Indiana-Wisconsin (Chicago-Naperville, IL-IN-WI) ozone nonattainment area to Serious ozone nonattainment in early 2019. When this area is reclassified as Serious ozone nonattainment, any future projects that occur on or after the effective date of the reclassification will be required to use a nonattainment New Source Review (NNSR) major source threshold of 50 tons per year (tpy) of Nitrogen Oxides (NOx) or Volatile Organic Matter (VOM). In addition, the applicability threshold for a Title V (i.e., Clean Air Act Permit Program, CAAPP) Operating Permit will be 50 tpy NOx or VOM. The major source thresholds for NOx or VOM under both of these programs has been 100 tpy.

The Chicago-Naperville, IL-IN-WI ozone nonattainment area is currently classified as a Moderate ozone nonattainment area, under the 8-hour 2008 ozone national ambient air quality standard (NAAQS). The attainment date under the 2008 8-hour ozone NAAQS for Moderate ozone nonattainment areas was July 20, 2018. Per US EPA the Chicago-Naperville, IL-IN-WI area did not demonstrate attainment by the deadline; and the area is therefore, proposed to be reclassified to Serious (per the requirements of the Clean Air Act). Additional details are available in the November 14, 2018 Federal Register notice. The affected counties in Illinois include: Cook, DuPage, Kane, Lake, McHenry, Will and parts of Grundy and Kendall. The affected counties in Indiana include: Lake and Porter. The affected county in Wisconsin is part of Kenosha.

US EPA will accept written comments, identified with "Docket ID No. EPA-HQ-OAR-2018-0226" on the proposed rule on or before December 14, 2018.

If you have any questions regarding the ozone nonattainment status for the Chicago-Naperville, IL-IN-WI, please contact the Chicago office at (630) 495-1470.