Per- and Polyfluoroalkyl Substances (PFAS)

Aqueous Film Forming Foam used for fire suppression contains PFAS Aqueous Film Forming Foam used for fire suppression contains PFAS

PFAS are challenging contaminants because most PFAS constituents cannot be detected using conventional analytical techniques. Remediation options that may address one PFAS constituent may not work for others, and only partial treatment may be achievable. Byproducts of treatment may not be detected and thus their risk is unknown. Risk-based standards for PFAS in soil and water are extremely low. Investigation and management of PFAS sites require an innovative, adaptable and educated team, actively involved in (not just aware of) current research, and capable of developing and optimizing new approaches in response to policy updates and technological advances.

What are PFAS?

PFAS, formerly known as "perfluorinated compounds" (PFCs), are emerging compounds of increasing importance for a broad spectrum of industrial sites and waterways. PFAS are a family of organic substances whose molecular structures contain multiple fluorine (F) atoms in place of hydrogen (H) atoms. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are the two most widely-recognized, environmentally-relevant PFAS, although there are hundreds of PFAS of potential significance, and little is known about these compounds.

Why are PFAS so Challenging?

The sources of PFAS in the environment (e.g., Aqueous Film Forming Foam [AFFF] or misting for electroplating) are typically comprised of complex mixtures of hundreds of individual PFAS constituents. The majority of PFAS constituents cannot be detected using conventional analytical techniques. Progress is being made towards developing analytical techniques to improve the detection of these constituents, including recent research by Geosyntec and partners developing nuclear magnetic resonance (NMR)-based analytical techniques and total fluoride field screening, but it may be years before comprehensive site characterization is achievable. The behavior of PFAS constituents in the environment can also vary widely depending on the composition of the PFAS mixture, the presence of co-contaminants, the introduction of oxidants or reductants into the environment. Maintaining fluoride mass balance while monitoring byproducts of degradation reactions is critical to understanding remedial success, but is currently difficult to achieve. As such, it is essential that knowledgeable practitioners, who fundamentally understand the limitations and challenges associated with PFAS, direct investigation and remediation efforts to achieve successful mitigation of risk at PFAS sites.

Our experts look at the “bigger picture” using rigorous and fundamental scientific principles. We utilize various tools in appropriate and defensible ways for client advocacy in regulatory negotiations, property transactions, claim disputes, and smart site management.


Site-Specific Technical Reviews and Investigation Strategies

U.S. Air Force Civil Engineer Center, Multiple Confidential Clients
  • Critically reviewed site-specific data, conceptual site models, and identified data gaps
  • Prepared scientifically-rigorous PFAS data collection plans and work plans

In-Situ Treatment to Enhance PFAS Removal and Destruction

SERDP/ESTCP, Navy, University of California at Berkeley
  • Conducted baseline site characterization and site-specific treatability studies
  • Demonstrated at field-scale a two-step thermally-enhanced low-pH persulfate oxidation and GAC sorption for PFAS mass removal and degradation

Development of Real-Time PFAS Analytical Methods

Geosyntec Internal R&D, Collaboration with Eurofins Eaton Analytical
  • Funded development of a mobile analytical instrument for real-time PFAS analysis in the field
  • Developed a Nuclear Magnetic Resonance technique for full spectrum PFAS characterization

Human Health Risk, Fate, and Chemical Liability Assessment

Minneapolis-St. Paul, Minnesota
  • Evaluated human health risks due to bioaccumulation of PFAS in fish
  • Assessed Total Maximum Daily Load (TMDL)
  • Liability analysis, litigation support and stakeholder communications

Community Outreach and Regulatory Policy Adherence

Issaquah Valley Aquifer, King County Washington
  • Managed the operational, public and regulatory issues associated with the revision of EPA's PFOS advisory limit downward to 0.07 ug/L
  • Initiated discussions with surrounding water purveyors and state regulatory agencies on future management of the aquifer system

Expert Panel Regarding PFAS Regulation

RAAF Base Williamtown, Australia
  • Technical support advising expert panel on PFAS regulation
  • Critical review and data gap analysis of conceptual site model
  • Peer review and advice for sampling and data interpretation

Catalyzing Knowledge Transfer Among Key Stakeholders

SERDP/ESTCP, Collaboration with Oregon State University
  • Authored peer-reviewed publications and keynote presentations at internationally- renowned conferences
  • Prepared up-to-date reference documents, frequently asked questions (FAQs), and online videos on PFAS chemistry, fate and transport, and site management options

Site-Specific Technical Reviews and Investigation Strategies

United States Air Force, Ahtna
  • Reviewed existing PFAS site data and developed a data gap assessment for PFAS transport to potential receptors
  • Conducted field drilling and analyzed soil, groundwater, and surface water samples
  • Validated PFAS data per Department of Defense (DoD) quality requirements
  • Developing a 3D conceptual site model and groundwater flow model to evaluate PFAS transport

Large-Scale Multi-Media PFAS Assessment

Confidential Client, Florida
  • Developed Standard Operating Procedures (SOPs) for PFAS sampling in soil, groundwater, surface water, and more
  • Identified AFFF storage and application areas and potential sample locations, based on document review, site reconnaissance, and site interviews
  • Developed multi-media sampling program and finalized sampling plan
  • Collected over 450 groundwater samples using direct push technology (DPT) from multiple locations and depths, monitoring well and surface water samples
  • Validated PFAS data to determine the defensibility and usability of the sample results in supporting the data quality objectives
  • Evaluated PFAS analytical results to identify PFAS source zones

PFAS Source Assessment and Regulatory Compliance Support

Confidential Industrial Clients, New England
  • Characterized PFAS release mechanisms and transport pathways, with a focus on airborne deposition from industrial processes and subsequent transport via roof runoff, impacts to groundwater and/or drinking water supplies
  • Identified potential PFAS sources, including fire training facilities, industrial discharges, septic discharges and wastewater treatment plant residuals
  • Sampled groundwater, stormwater, surface water, drinking water, soil and sediment
  • Developed conceptual site model by synthesizing field and laboratory data and conducting a forensic analysis of PFAS mixtures, including branched isomers to assess PFAS origin
  • Conducted community outreach and coordination with state and municipal agencies affected by PFAS in drinking water
  • Adapted investigation and regulatory compliance approach in response to a rapidly evolving regulatory framework for PFAS

Site-Specific Review and Strategy Development

Confidential Client, California
  • Critically reviewed site specific data, conducted quality assurance/quality control, developed data collection SOPs and database management
  • Evaluating effect of PFAS on treatment of other contaminants of concern using traditional treatment technologies (e.g., ion exchange, ultraviolet treatment)

Fire Training Area Assessments

Confidential Client, Florida
  • Identified and categorized unused AFFF in drums and totes and coordinated removal, proper off-site disposal, and incineration of materials
  • Conducted site reconnaissance and conducted site interviews to identify potential AFFF storage and application areas
  • Developed work plans to perform multi-media sampling (groundwater, surface water, soil, and sediments) for PFAS at multiple Florida fire training facilities
  • Implemented work plans and evaluated data to determine the presence or absence of PFAS-affected media and guide future activities

Groundwater Modeling to Evaluate PFAS Fate and Transport

Eielson Air Force Base, Alaska
  • Compiled and reviewed available information on lithology, hydrogeology and chemistry
  • Documented local pumping wells to understand groundwater withdrawal and sinks
  • Collected stable isotope samples to evaluate permafrost distribution and its effect on groundwater flow paths
  • Revised site conceptual site model, including distribution of permafrost in the subsurface
  • Developed a preliminary base-wide groundwater flow model using Modflow-USG
  • Refined and calibrated model will be used to evaluate PFAS flow paths in relation to known groundwater use receptors

Smouldering Combustion Treatment of PFAS-Impacted Materials

SERDP Project, Savron
  • Evaluate the effectiveness of stormwater best management practices (BMP) for treating PFAS and other emerging contaminants
  • Evaluate the risk of sediment recontamination from stormwater discharges

PFAS Stormwater BMPs

SERDP Program, Texas Tech, Stanford University
  • Critically reviewed site specific data, conducted quality assurance/quality control, developed data collection SOPs and database management
  • Evaluating effect of PFAS on treatment of other contaminants of concern using traditional treatment technologies (e.g., ion exchange, ultraviolet treatment)

PFAS Stormwater Drywell Guidance

SERDP Program, California State Water Resources Control Board
  • Analyzing published data to develop new statewide guidance for stormwater drywells which may be a pathway for contaminants to groundwater
  • Developing a risk-based framework for drywell siting and design to reduce stormwater as a potential source, including potential risks of PFAS groundwater contamination from stormwater infiltration


Geosyntec Consultants
Geosyntec is a consulting and engineering firm that works with private and public sector clients to address new ventures and complex problems involving our environment, natural resources, and civil infrastructure.

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