As of September 4, 2020, Illinois has responsibility for direct administration of the Prevention of Significant Deterioration (PSD) permitting program under state regulations, including federal Clean Air Act (CAA) requirements under authority delegated by the U.S. Environmental Protection Agency (EPA). In doing so, Illinois joins 46 other states that have elected to administer the PSD program directly.  State PSD regulations, added as Part 204 of the Illinois air quality pollution rules, 35 Ill. Adm. Code Part 204, were published in the Illinois Register on September 19, 2020.

New Source Review (NSR) requires that geographic areas be designated as in attainment or nonattainment based on National Ambient Air Quality Standards (NAAQS), which are based on air quality for the criteria pollutants ozone, carbon monoxide, sulfur dioxide, particulate matter (PM10 and PM2.5), lead, and nitrogen dioxide, on a pollutant-by-pollutant basis. The PSD program applies in all areas where one or more of these criteria pollutants are within attainment levels.

Any new major source of air pollution in an area that meets NAAQS must obtain a PSD permit. An existing major source must obtain a PSD permit when a physical or operational change results in significant new emissions. Smaller sources and non-major modifications at major sources may be required to obtain PSD permits under certain circumstances, as specified by state regulations.

Previously, the Illinois Environmental Protection Agency (IEPA) implemented PSD permits through authority delegated by EPA based on federal programmatic requirements. Now, IEPA has direct enforcement authority. The most significant change under the new state regulations is that permit appeals will no longer be reviewed by the federal Environmental Appeals Board. Once Illinois’ PSD program goes into effect, IEPA determinations regarding PSD permit applicability and compliance will be reviewed by the Illinois Pollution Control Board under state regulations.

No economic analysis was conducted for the change in PSD implementation, presumably because, absent any substantive regulatory change, it is unlikely that a shift in administration alone will impose any significant new costs. IEPA has argued that the proposed state regulations will benefit regulated entities; going forward, all construction requirements, including PSD compliance requirements, will be consolidated into in a single construction permit application and addressed in a single state-issued permit.

IEPA may initiate rulemaking to make changes in the future. States implementing the PSD program have the authority to develop tailored requirements and procedures so long as they are at least as stringent as the EPA requirements.

Troutman Pepper will be providing regular updates and alerts on Illinois air quality regulations, including the pending state-implemented PSD program. For more information, please contact Kevin Desharnais at or Louise Dyble at