Every Illinois SRP Site Affected: New Groundwater Rules Redraw Cleanup Boundaries
Authored by: Michael J. Hillebrenner, PE
On July 23, 2025, the Illinois Environmental Protection Agency (Illinois EPA) issued a pivotal clarification that reshapes how remediation objectives are applied across every site in its Site Remediation Program (SRP). This update follows amendments made earlier this year to the 35 Illinois Administrative Code (IAC) Part 620 Groundwater Quality Standards (GQS)—changes that now require cleanup efforts for sites within the SRP to meet the most conservative thresholds between existing and newly adopted standards. With 13 new chemicals added, 47 updated, and significant shifts in exposure risk calculations, the implications are sweeping. From the removal of permeameter testing to an expanded definition of Class I groundwater, these changes redefine what it means for a site to pose “no threat to human health and the environment”—a determination central to receiving a coveted No Further Remediation (NFR) letter.
How could this amendment delay issuance of an NFR letter?
Almost all active sites within the Illinois SRP will be impacted by this regulatory change, effective immediately. Currently, there are 848 listed active sites under investigation in the Illinois SRP. Many commonly found contaminants of concern, including 11 inorganics (metals), 44 organics, and five others, have newly defined Class I and/or Class II groundwater remediation objectives which may require further delineation and remediation prior to receiving an NFR letter for the site.
Additional changes include the following (see 35 Ill. Adm. Code 620.210(a)):
- The Non-TACO Class I and Class II Groundwater Objectives that the Illinois EPA has historically provided in a spreadsheet under “Resources” on the TACO webpage, also need to be compared to the Part 620 GQS and again, the most conservative value utilized as the cleanup objective. An updated spreadsheet is expected in August of 2025.
- The removal of the permeameter test as a valid method to determine hydraulic conductivity for the purposes of classifying groundwater, meaning the Illinois EPA no longer accepts permeameter tests (ex situ) for determination of hydraulic conductivity for any purpose.
- An expanded meaning of what constitutes Class I groundwater, which now includes:
- Phase I and phase II wellhead protection areas for community water supply wells/well fields.
- Designated maximum setback zones for community water supply wells/well fields.
Though the clarification was announced on July 23, this information can be found on the SRP Program page under April 11, 2025.
What can Roux do to help?
Roux’s team of Licensed Professional Engineers (PEs), Licensed Professional Geologists (PGs), and environmental professionals can assess how the new GQS affects impacted sites and evaluate the potential implications that these changes could have on project remediation status, site closures, long-term monitoring, costs, regulatory timeframes, and due diligence transactions.
While navigating these regulatory changes, Roux can assist with designing an approach tailored to site-specific objectives and goals utilizing Tier 2 and Tier 3 risk-based closure approaches. Please contact our team with any questions or concerns below.
