The U.S. Environmental Protection Agency (EPA) has approved Illinois’ revised Public Water System Supervision program for implementation of the federal 2024 PFAS National Primary Drinking Water Regulation (NPDWR), giving the state authority to enforce the federal requirements if the determination becomes final.

EPA announced the tentative approval Sept. 30, with a public hearing request period running through Oct. 30. If no qualifying hearing request is received, the determination will become final and effective Oct. 30.

Illinois adopted rules matching the federal PFAS drinking water standards earlier this year. Under the state requirements, community water systems must complete initial monitoring by April 25, 2027, begin ongoing compliance monitoring April 26, 2027 and comply with the applicable maximum contaminant levels (MCLs) beginning April 26, 2029.

The development comes as EPA works to modify portions of the 2024 federal PFAS regulation. In May, EPA proposed maintaining the MCLs for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) while allowing water systems to request an additional two years, through 2031, to comply with those standards. EPA also proposed rescinding federal standards for PFHxS, PFNA, HFPO-DA, commonly known as GenX chemicals, and the Hazard Index mixture covering those chemicals and PFBS.

EPA had encouraged states seeking PFAS primacy to request additional time to develop their applications while the federal rulemaking proceeds. However, Illinois has moved forward with its primacy package.

The situation could create uncertainty for Illinois water systems if federal compliance deadlines or PFAS standards change after state primacy is finalized. EPA’s proposed federal two-year extension specifically addresses PFOA and PFOS, while Illinois’ current regulations establish a broader set of PFAS requirements.