On August 18, 2026, a unanimous D.C. Circuit panel denied every petition challenging the U.S. Environmental Protection Agency’s (EPA’s) rule designating perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) § 102(a). In doing so, the court held that uncertainty about future cleanup costs did not make the rule arbitrary and capricious, because, as explained in EPA’s Designation itself, “CERCLA response actions are discretionary, contingent, and site-specific determinations.”

This post analyzes how those site-specific determinations have been made and are likely to be made when closed sites are reviewed for potential contamination by PFOA/PFOS. The mechanism is the Five-Year Review (FYR), which is required wherever a site remedy leaves contamination in place above levels that allow unrestricted use. In the FYR process, PFOA/PFOS contamination may be assessed, at which point EPA may determine that further response action is needed to ensure the remedy selected for the site remains protective of public health and the environment—including with respect to any known or suspected PFOA/PFOS contamination. At settled sites, that determination can lead EPA to invoke a consent decree “reopener.”

Five-Year Reviews

Most CERCLA sites are subject to an FYR.  Under CERCLA §121(c), sites are required to conduct FYRs when, “[u]pon completion of the remedial action, hazardous substances, pollutants, or contaminants will remain on site” such that the site cannot be granted “unlimited use and unrestricted exposure” (UU/UE) status.  Some FYRs are also conducted as a matter of EPA policy, for example when a remedial action will not leave hazardous substances, pollutants, or materials on site but the remedy will take more than five years to complete.

The goal of an FYR is to assess whether a chosen remedy is or will be protective of human health and the environment. This is the so-called “protectiveness” determination, which the 2001 Comprehesive FYR Guidance explains should be based on data showing how a remedy has been implemented and how well it is performing. The National Contingency Plan (NCP) generally defines protectiveness in terms of the acceptable cancer risk range and the hazard index (HI).

Consent Decrees and Reopeners

Settlements for remedial action must be entered as consent decrees (CDs), typically before the remedial action begins. CERCLA § 122(f)(1) allows the government, at its discretion, to include in CDs a covenant not to sue for future liability “resulting from a release or threatened release of a hazardous substance addressed by a remedial action…” However, § 122(f)(6)(A) requires that this covenant not to sue include an exception for liability arising from conditions unknown at the time the remedial action is certified to be complete. A newly designated hazardous substance, such as PFOA/PFOS, discovered at a site where the remedy predates any sampling for that substance may be considered a previously unknown condition.

While minor changes in a remedy are fairly easy for EPA to make through a memo to the site file or similar administrative measure, making a significant change like adding PFOA/PFOS as a constituent of concern is not as easy. EPA would need to issue an Explanation of Significant Differences (ESD) or a new Record of Decision (ROD). Then EPA would have to either amend the CD by consent or invoke a reopener—or, if the new work is outside the CD’s covenant not to sue, EPA could issue a unilateral order. While the rest of this post focuses on the reopener method and what has occurred there to date, the agency is more likely to identify and evaluate previously unrecognized PFAS contamination that could trigger one of the above methods as EPA introduces and approves more tools for evaluating PFAS (e.g., the recently-approved addition of PFAS to the Leaching Environmental Assessment Framework (LEAF), which tests how contaminants leach from solid waste).

EPA Analysis at Federal Facility Superfund Sites

EPA’s approach to PFOA/PFOS contamination at federal facilities is becoming clearer, in part because so many of the facilities are already becoming well characterized for PFOA/PFOS contamination. Thanks in large part to the Department of War/Defense PFAS Task Force established in July 2019, the federal government has already taken steps to characterize PFOA/PFOS contamination at military bases and other federal facilities. As a result, EPA issued a Remedial Project Manager (RPM) Bulletin in April 2024 specifically to assist EPA RPMs reviewing how PFAS, including PFOA/PFOS, are addressed in FYRs for Federal Facility Superfund Sites. At federal facilities, the lead agency (such as the Department of War/Defense) conducts the FYR and makes a protectiveness determination. EPA then either concurs with that determination or makes its own.  EPA instructs RPMs to “[c]onsider the potential impacts of new and emerging chemicals on protectiveness determinations” and proposes four options to select from once a review is complete and PFAS are identified:

  • Short-term protective. EPA identifies PFAS but concludes no current human exposure exists, typically coupled with additional investigation obligations. The 2024 FYR for the NASA Goddard Wallops Flight Facility is an example. See page 4-9.
  • Deferred. EPA finds characterization of PFAS is insufficient and protectiveness cannot yet be determined. For example, EPA deferred a protectiveness determination for two operable units in the 2024 FYR for the Sharpe Army Depot because elevated PFAS concentrations had been identified in potable-water supply wells and off-post private wells. It was unclear, however, if this water was also being used as drinking water. See EPA Independent Determination Letter, pages 1-2.
  • Not protective. EPA identifies PFAS exposures that remain insufficiently controlled. Although this is included as a possible option in the April 2024 Bulletin, we were not able to locate any FYRs that made a “not protective” determination based on the presence or likely presence of PFAS at the site. Instead, protectiveness was deferred. EPA notes in the above-referenced Independent Determination Letter that “a protectiveness determination of ‘not protective’ could be applicable if an immediate threat is present and it is reasonably likely that unacceptable exposures are occurring.”
  • An independent EPA finding. EPA reaches its own protectiveness conclusion when it disagrees with the lead agency that performs the FYR. Similar to the 2024 Letter referenced above, in 2023, EPA issued an independent protectiveness determination of “short term protective”—instead of the Air Force’s “protective” determination—explicitly because PFAS contamination at the Fairchild Air Force Base had already been confirmed, preventing the site from achieving a UU/UE status.

The RPM’s protectiveness determination is site-specific and hinges on what is known about the nature and extent of PFAS contamination as well as the potential for current and future exposures. It must be supported by adequate evidence. Nevertheless, this bulletin has given federally-owned sites guidelines on what to expect from EPA during each site’s FYRs. The same is not true for non-federal sites.

Practical Implications for Non-Federal Superfund Sites.

Among the recent non-federal FYRs reviewed, the emerging pattern is for reviewers to deem the remedy “protective” but require Potentially Responsible Parties (PRPs) to test extensively for PFAS.

Landfill Superfund sites appear to be the front-runners in having PFOA/PFOS addressed in FYRs. Earlier this year, EPA urged PRPs at a landfill site in Stark County, Ohio to continue conducting extensive testing of PFAS on the site. In the FYR, EPA recommended the site continue its earlier-ordered supplemental remedial investigation and human health risk assessment with a focused feasibility study to follow. Despite recommending the evaluations continue and suggesting a different remedy may be selected in the future, EPA ultimately found the remedy in place remained protective.

EPA took a similar tack at a landfill Superfund site in Wisconsin, even though PFAS had not been identified in groundwater. Rather, solely on the basis that PFAS was found at similar landfill sites with volatile organic compound contamination, EPA “recommend[ed]” the PRP “evaluate historical information and records regarding past waste management practices and the potential for past disposal of PFAS… and submit a summary of findings [and] repair and implement a work plan to assess the presence and distribution of these compounds in groundwater at the Site.”

Finally, at a landfill Superfund site in La Porte County, Indiana, EPA found the remedy protective but nonetheless required PFAS sampling by the PRP group because “PFAS-containing waste was potentially disposed of in the unlined landfill during periods of operation consistent with the widespread use of PFAS in commercial, industrial, and household products.”

Taken together, these FYRs illustrate that the evidentiary threshold for requiring further investigation appears relatively low. In some instances, the rationale was not site-specific at all but relied simply on the broader observation that PFAS has been discovered at comparable sites. We are not aware of any challenges to the sufficiency of that basis for requiring additional investigation obligations.

To further complicate matters for non-federal sites, EPA has not issued RPM guidance like the April 2024 Bulletin issued for federal facilities. And while FYRs at non-federal sites may find a remedy remains protective for a given operable unit, EPA may nonetheless “recommend” additional remedial investigation, which can be costly and time-consuming for private PRPs.

Action Items for Private Parties

Should your business circumstances demand some need to perform a PRP PFAS risk analysis, you may want to consider: (1) assessing whether specific historical site operations create a plausible PFAS nexus; (2) determining whether PFAS sampling has already occurred at or near the site (e.g., at nearby sites, as part of a municipal sampling program, or the like); and (3) if PFAS may be present, evaluating whether the current remedy would effectively manage or contain PFAS, reviewing the CD and reopener language, and considering whether it may be possible to link the PFAS at the site to the conduct of another entity.

Please reach out to a member of the CERCLA team at Squire Patton Boggs if you have any questions or would like to discuss a site-specific issue.