The U.S. Environmental Protection Agency (EPA) will soon redesignate eleven ozone nonattainment areas from moderate to serious. Notice of the action was published in the August 23, 2019 edition of the Federal Register. The Chicago-Naperville (IL-IN-WI) ozone nonattainment area was included in the redesignation and will move from moderate to serious nonattainment status effective September 23, 2019.

The redesignation lowers the major source threshold for nitrogen oxides (NOx) and volatile organic material (VOM) - also known as Volatile Organic Compounds (VOCs) - from 100 tons per year (tpy) to 50 tpy. Newly installed emission units and modifications of existing units that emit NOx and VOM will be subject to the new threshold. As of September 23, 2019, new construction or modification of an emission unit at an existing major source is a major modification if the potential-to-emit (PTE) for the new unit, or net emissions increase for an existing unit, exceeds 25 tpy of NOx or VOM.

The Illinois Environmental Protection Agency (Illinois EPA) began mailing letters to facilities potentially impacted by the redesignation. These letters targeted facilities operating under Federally Enforceable State Operating Permits (FESOPs) and Lifetime Operating Permits (LOPs) whose PTE of NOx and/or VOM is between 50 tpy and 100 tpy. The same letter was also provided to facilities with PTE of NOx and/or VOM close to 50 tpy that could potentially exceed 50 tpy, if exempt emission units and fugitive emissions were included in emission calculations.

Sources operating with PTE of NOx and/or VOM greater than 50 tpy that were previously exempt from the requirement to obtain a major source permit under the Clean Air Act Permit Program (CAAPP) are now required to submit an application for a CAAPP permit no later than September 23, 2020. Alternatively, sources may submit an application for a FESOP (or revised FESOP) that limits the PTE of NOx and VOM below 50 tpy.

Sources evaluating NOx and VOM PTE should remember to include exempt emission units and fugitive emissions in PTE calculations. Normally fugitive emissions are only included for sources on the “list of 28” industries and processes subject to the originally promulgated group of New Source Performance Standards. However, fugitive emissions are required to be included for all sources located in serious, severe, or extreme nonattainment areas.

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