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The Illinois Environmental Protection Agency (IEPA) is proposing changes to the State Administrative Codes that regulate groundwater quality throughout the state of Illinois, 35 Ill. Adm. Code 620.[1],[2] Many of the changes proposed by the IEPA are updates to exposure factors that are used to determine the toxicity thresholds for various chemical compounds to reflect the latest science and current federal guidance. The proposed changes also include the addition of nine chemicals that did not previously have Groundwater Quality Standards (GQS) in the state of Illinois, five of which are per and poly-fluoroalkyl substances (PFAS):

  • Aluminum
  • Lithium
  • Molybdenum
  • 1-Methylnaphthalene
  • Perfluorooctanoic acid (PFOA)
  • Perfluorooctanesulfonic acid (PFOS)
  • Perfluorononanoic acid (PFNA)
  • Perfluorohexanesulfonic acid (PFHxS)
  • Perfluorobutanesulfonic acid (PFBS) 

The proposed GQS values for PFAS are calculated to be the same for both Class I Waters: Potable Resource Groundwater and Class II Waters: General Resource Groundwater. The calculated GQS for PFAS are as follows:


GQS (ng/L[3] or PPT[4])

PFBS 1,200
PFHxS 77
PFOS 7.7


Should these GQS values be promulgated into rule, Illinois would join 17 other states with enforceable PFAS regulations pertaining to groundwater quality and/or groundwater used as drinking water. However, these limits would make Illinois the state with some of the strictest PFAS groundwater quality criteria. Illinois’s proposed PFOA standard, for example, would become the lowest in the Country for this organofluorine. Many states currently have no standards or rely at some level on the Federal Drinking Water Health Advisory Levels of 70 ppt for PFOA and PFOS that were published by the United States Environmental Protection Agency (USEPA) in 2016.[5]

What does this mean? 

A recognition that the occurrence of PFAS in environmental media may be widespread due to both local and non-point sources is strongly influencing the approach to characterize sites. Because several phases within the lifecycle of a project will be affected by these proposed GWQ standards, particularly sites where the potential for PFAS impacts are higher, having clarity on how to address this condition for diligence projects is critical to completing projects accurately and on-time to meet project deadlines. Just as with all other contaminants that are defined as hazardous by the State of Illinois, the PFAS ‘risk’ to a site or property would need to be evaluated in standard environmental due diligence assessments. ASTM E1527-13 Phase I standards do not presently provide guidance on how to assess a site for PFAS, and proposed changes to these standards, via ASTM E1527-21, suggest that ASTM will consider PFAS to be a non-scope item (Section 13.1.5) for sites located in states with agency regulations. For sites where the risk is apparent, and in states with existing PFAS regulation, an evaluation beyond the standard ASTM Phase I should be recommended. This will mean that PFAS will need to be factored into the site’s due diligence activities, to understand if historical site operations, chemical use, and disposal practices suggest or document the use and release of PFAS to the environment. In a forthcoming blog, we will discuss how due diligence activities can be performed and reported, beyond standard Phase I reports, to account for emerging concerns not regulated by CERCLA.

PFAS would also be added to groundwater remediation objectives, which will be incorporated into the Illinois’ Risk Based Cleanup Objectives, Tiered Approach to Corrective Action Objectives (TACO). Sites that are currently enrolled in the Site Remediation Program (SRP), or are in the process of entering the SRP, would need to evaluate the applicability of these five PFAS as potential contaminants of concern under TACO. This means PFAS --- including precursor transformation that could result in a terminal compound with a GWQ standard --- will need to be considered in site characterization and general investigations. 

Despite the lack of enforceable federal guidance or for this reason, Illinois is closer to having distinctive state-level standards for groundwater quality.


[1] https://www2.illinois.gov/epa/about-us/rules-regs/water/Pages/620-Groundwater-Quality.aspx

[2] The public comment period on the proposed rules expired on June 25th.

[3] nanograms per liter

[4] parts per trillion

[5] https://www.epa.gov/ground-water-and-drinking-water/drinking-water-health-advisories-pfoa-and-pfos

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