Much is being discussed today about the prevalence of PFAS (per- and polyfluoroalkyl substances) in groundwater, the potential health effects of exposure to PFAS in groundwater, and the development of groundwater cleanup standards by USEPA and state environmental protection departments. Less discussed (at least in the news media) is the subject of remediation. Notwithstanding the inference of the "forever" label, can these chemicals be effectively remediated, in-situ, in groundwater?

Answering this question may be aided by a remediation pilot study being undertaken at a PFAS site in East and West Rockhill Townships, Bucks County, Pennsylvania – the Ridge Run PFAS Site. Ridge Run became a state superfund site (under Pennsylvania's Hazardous Sites Cleanup Act ("HSCA"), 35 P.S. §§ 6020.102-6020.1303) in 2016 when a combined concentration of PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate) exceeding the United States Environmental Protection Agency's (EPA) then-applicable Health Advisory Level (HAL) (70 parts per trillion) was discovered in a public water supply well.

Although it has been reported that a source (if not the source) of PFAS at Ridge Run may have been the use of PFAS-containing firefighting foam to extinguish a local tire pile fire in 1986, the Pennsylvania Department of Environmental Protection (DEP) has not yet pursued enforcement against any alleged responsible parties. Accordingly, DEP has itself funded the investigation of soil and groundwater, and is funding both the installation and maintenance of filtration systems for private properties serviced by impacted drinking water wells. In addition, to the end of meeting its self-described responsibility under HSCA to select a remedy that is "protective of human health and the environment and complies with all statutory and regulatory requirements," DEP is funding a pilot project involving the injection of a Regenesis product known as PlumeStop® into the contaminated aquifer.

As described by PaDEP, the goal of the pilot study is to determine the effectiveness of PlumeStop® in creating "a permeable, underground barrier, which will allow groundwater to flow through it, but not PFOA and PFOS."

As described by Regenesis, PlumeStop® is a "liquid colloidal activated carbon" that "effectively converts the polluted aquifer itself into a purifying filter." In simplest terms, the product, after being injected into the aquifer, is designed to act as an in-ground sponge to which PFAS "sticks" as PFAS-contaminated groundwater moves through the injection area.

Perhaps most notably, EPA, when authorizing the injection of PlumeStop® at the Ridge Run Site, published what amounts to a near-endorsement of the product: "PlumeStop® Liquid Activated Carbon is an innovative groundwater remediation technology designed to rapidly remove and permanently degrade groundwater contaminants. Once contaminants are sorbed onto the regenerative matrix of PlumeStop®, biodegradation processes achieve complete remediation at an accelerated rate." EPA also stated, "Based on the information provided, we do not believe that the proposed injection will cause an adverse impact to the ground water."

PlumeStop® was injected into the groundwater at the Ridge Run Site in April, 2021. DEP has advised that "[t]he results of the post-injection sampling events show sustained and substantial reductions of PFOA and PFOS in monitoring wells within the study area." It adds, on its website for the Ridge Run Site (, "DEP and its contractors will continue to perform groundwater sampling to determine the success of the pilot study. Updates on the pilot study will continue to be posted on this website in the future."

As with all remediation treatment technologies, site-specific conditions, the design of the treatment approach, and a variety of other factors can affect the degree of success, both short-term and long-term. Ridge Run is not the first site at which PlumeStop® has been used, and other sites (as well as other products and technologies) will bear close watching. But given the maturity of the Ridge Run Pilot test (approaching two years since injection), this site should be instructive for those focused on remediation of PFAS-contaminated groundwater.

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