Environmental Forensic Investigation of PFAS Groundwater Contamination Using Hydrogeologic Evaluation, Environmental Forensics, and Fate and Transport Assessment
Project Overview
Per- and polyfluoroalkyl substances (PFAS) have emerged as one of the most significant classes of environmental contaminants investigated by environmental scientists, hydrogeologists, and regulatory agencies over the past several decades. Because these synthetic fluorinated compounds possess exceptional chemical stability and resistance to biological and environmental degradation, PFAS have been detected in groundwater, surface water, soils, sediments, drinking water supplies, and numerous industrial and commercial settings worldwide. Their widespread historical use in manufacturing operations, industrial processes, metal finishing, coatings, specialty chemical production, and consumer products has resulted in numerous environmental investigations requiring reconstruction of historical releases and evaluation of contaminant migration through complex hydrogeologic systems. Environmental forensic investigations involving PFAS frequently require integration of groundwater chemistry, hydrogeology, contaminant fate and transport, historical operational information, and long-term environmental monitoring data to characterize contaminant distribution and evaluate potential impacts to surrounding environmental receptors.
This environmental forensic investigation involved the technical evaluation of PFAS detected within groundwater surrounding an industrial facility using accepted principles of hydrogeology, environmental chemistry, contaminant fate and transport, groundwater monitoring, and environmental forensics. The investigation integrated historical groundwater monitoring data, environmental sampling results, hydrogeologic information, monitoring well networks, groundwater flow interpretation, and published scientific understanding of PFAS behavior to evaluate the distribution and migration of PFAS within the subsurface environment. Rather than relying upon a single dataset, the investigation considered multiple independent categories of technical evidence collected over several years to develop a scientifically supported understanding of groundwater conditions and the spatial distribution of PFAS throughout the investigation area.
The investigation was performed using accepted principles of environmental forensics, hydrogeology, groundwater investigation, environmental chemistry, contaminant transport analysis, and exposure assessment. Available technical documentation, groundwater analytical results, hydrogeologic interpretations, monitoring well data, and published scientific literature were evaluated collectively to characterize groundwater conditions and identify patterns of PFAS occurrence within multiple hydrostratigraphic intervals. Particular emphasis was placed on evaluating groundwater flow characteristics, temporal trends in groundwater concentrations, and the relationship between contaminant distribution and the underlying hydrogeologic framework. These approaches are widely recognized within environmental consulting and regulatory investigations for evaluating historical contaminant releases and supporting technically defensible environmental forensic investigations.
Because PFAS contamination frequently evolves over many years as groundwater migration continues under changing hydrogeologic conditions, the investigation also considered temporal changes in groundwater concentrations together with groundwater flow direction, hydraulic gradients, aquifer characteristics, and long-term monitoring results. Historical groundwater conditions were therefore evaluated within the broader context of contaminant transport processes and accepted hydrogeologic principles rather than relying solely upon individual sampling events. This multidisciplinary approach provides a scientifically reliable framework for reconstructing historical groundwater contamination, evaluating contaminant migration, and interpreting long-term monitoring data while remaining consistent with accepted principles of environmental forensics and groundwater science.
Chemicals of Concern
The primary chemicals of concern evaluated during this investigation were per- and polyfluoroalkyl substances (PFAS), with particular emphasis on perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Unlike many conventional environmental contaminants that degrade through biological, chemical, or photolytic processes, PFAS comprise a large family of synthetic fluorinated compounds characterized by exceptionally strong carbon-fluorine bonds that impart remarkable environmental persistence. These unique chemical properties have led to widespread industrial and commercial applications while simultaneously contributing to the long-term persistence of PFAS within soil, groundwater, surface water, and drinking water supplies following environmental release. As a result, environmental forensic investigations involving PFAS require careful evaluation of contaminant occurrence, hydrogeologic conditions, historical site operations, and groundwater migration using accepted principles of environmental chemistry and contaminant fate and transport.
The investigation considered the occurrence of multiple PFAS compounds within groundwater because individual PFAS exhibit differing chemical characteristics that influence their environmental behavior, mobility, persistence, and transport within subsurface environments. PFOA and PFOS have historically been among the most extensively investigated PFAS due to their widespread historical use, environmental persistence, and frequent detection at industrial facilities and surrounding groundwater systems. Scientific literature has demonstrated that these compounds are highly resistant to degradation under typical environmental conditions and may remain within groundwater systems for extended periods following release. Their chemical stability allows dissolved PFAS to migrate with groundwater while interacting with soils, sediments, and aquifer materials in ways that influence long-term contaminant distribution and plume development.
The principal exposure pathway evaluated during this investigation was ingestion of groundwater containing dissolved PFAS. Unlike investigations involving airborne contaminants, groundwater investigations focus on the movement of dissolved chemicals through saturated subsurface materials and the potential for migration toward drinking water supplies or other environmental receptors. Consequently, evaluation of groundwater contamination requires integration of analytical chemistry, hydrogeology, groundwater flow characterization, and contaminant transport modeling to understand both the current distribution of contaminants and their potential future migration. Groundwater investigations therefore evaluate contaminant occurrence within multiple monitoring locations together with groundwater elevations, hydraulic gradients, aquifer characteristics, and long-term monitoring trends to characterize the extent of contamination.
An important component of environmental forensic evaluation involves understanding the behavior of PFAS following release into the subsurface environment. Once released, dissolved PFAS may migrate through soil into groundwater where contaminant movement becomes controlled primarily by groundwater flow, aquifer properties, and the chemical characteristics of individual PFAS compounds. Although PFAS generally exhibit relatively high mobility compared to many hydrophobic organic contaminants, migration rates may vary according to chain length, functional group chemistry, groundwater geochemistry, organic carbon content, and interactions with aquifer materials. Evaluation of these processes provides important scientific context for interpreting groundwater monitoring data and understanding the spatial distribution of contamination observed throughout a monitoring network.
The investigation also considered temporal changes in groundwater concentrations observed during multiple sampling events. Long-term groundwater monitoring provides valuable information regarding contaminant stability, plume migration, groundwater flow patterns, and changes in environmental conditions over time. Repeated sampling from monitoring wells completed within different hydrostratigraphic intervals allows environmental scientists to evaluate both horizontal and vertical contaminant migration while distinguishing between transient fluctuations and long-term contaminant trends. These temporal evaluations are particularly important during PFAS investigations because contaminant persistence often results in groundwater plumes that evolve over many years or decades following the original release.
Evaluation of the environmental significance of PFAS also considered the relationship between hydrogeology and contaminant transport. Groundwater flow direction, hydraulic conductivity, aquifer stratigraphy, recharge conditions, and subsurface heterogeneity all influence the movement of dissolved contaminants within groundwater systems. Consequently, interpretation of groundwater analytical results requires evaluation of both the measured PFAS concentrations and the hydrogeologic framework controlling contaminant migration. The environmental forensic approach employed during this investigation relied upon accepted scientific principles of groundwater hydrology, contaminant transport, environmental chemistry, and exposure science to evaluate historical groundwater conditions using available technical evidence rather than isolated sampling events or unsupported assumptions.
Finally, the investigation recognized that environmental evaluation of PFAS requires consideration of both contaminant chemistry and long-term groundwater behavior. Industrial releases of persistent contaminants frequently produce complex groundwater plumes influenced by historical operations, source characteristics, aquifer properties, and natural groundwater movement. Published scientific investigations consistently demonstrate that characterization of PFAS contamination requires integration of groundwater analytical results, hydrogeologic interpretation, long-term environmental monitoring, and accepted contaminant transport methodologies. Accordingly, reconstruction of historical groundwater contamination relies upon evaluation of monitoring data together with environmental chemistry and hydrogeologic principles to develop a scientifically supported understanding of contaminant migration and groundwater conditions while remaining consistent with accepted principles of environmental forensics, hydrogeology, and groundwater investigation.
Methods
The investigation was conducted using established principles of environmental forensics, hydrogeology, groundwater investigation, environmental chemistry, contaminant fate and transport, and exposure assessment. Because groundwater contamination investigations frequently involve large environmental datasets collected over multiple years, the evaluation integrated numerous independent sources of technical information to characterize groundwater conditions using scientifically accepted methodologies. Rather than relying upon a single category of evidence, the investigation incorporated groundwater analytical data, monitoring well information, hydrogeologic interpretations, groundwater elevation data, historical sampling results, environmental site characterization, and published scientific literature to develop a comprehensive understanding of PFAS occurrence within the subsurface environment. This multidisciplinary approach is consistent with accepted environmental consulting practices for evaluating groundwater contamination and reconstructing historical contaminant migration.
A substantial component of the investigation involved review of historical groundwater monitoring records and environmental sampling data. Available groundwater analytical results were evaluated to characterize PFAS concentrations within monitoring wells completed at multiple depths throughout the investigation area. Historical monitoring results were reviewed together with hydrogeologic information to evaluate contaminant distribution, identify spatial trends, assess changes in groundwater concentrations over time, and characterize the overall extent of groundwater impacts. Long-term groundwater monitoring represents a fundamental component of environmental forensic investigations because repeated sampling provides important information regarding contaminant persistence, plume stability, and migration within the subsurface environment.
The investigation also included an extensive review of hydrogeologic conditions influencing groundwater flow and contaminant transport. Particular emphasis was placed on evaluating groundwater flow direction, hydraulic gradients, aquifer stratigraphy, and the relationship between contaminant occurrence and the underlying hydrogeologic framework. Monitoring wells completed within multiple hydrostratigraphic intervals were evaluated to characterize both horizontal and vertical contaminant distribution throughout the groundwater system. Interpretation of groundwater flow patterns together with analytical chemistry provides an important scientific basis for understanding the migration of dissolved PFAS and evaluating potential pathways through the subsurface environment.
Contaminant evaluation methods considered the relationship between groundwater chemistry and hydrogeologic conditions. Rather than evaluating individual monitoring wells independently, the investigation recognized that groundwater contamination reflects the combined influence of contaminant sources, groundwater flow, aquifer characteristics, and long-term transport processes. Consequently, accepted environmental forensic methodologies evaluate groundwater analytical results collectively while considering hydraulic connectivity, stratigraphic relationships, groundwater elevations, and temporal sampling trends. These approaches provide a more scientifically representative understanding of contaminant migration than interpretation of isolated analytical results obtained during individual sampling events.
The technical evaluation further incorporated accepted principles of contaminant fate and transport that are routinely applied within groundwater investigations. Historical groundwater monitoring data were evaluated together with hydrogeologic information to characterize contaminant migration within the groundwater system and assess the stability of observed groundwater concentrations over time. Evaluation of concentration distributions, plume geometry, groundwater flow characteristics, and temporal monitoring trends provides a scientifically supported framework for interpreting groundwater contamination because contaminant behavior within subsurface environments is influenced by both chemical properties and hydrogeologic conditions. Integration of these independent sources of information therefore represents an important component of environmental forensic groundwater investigations.
The investigation also included review of groundwater monitoring network design and environmental sampling practices. Available monitoring wells were evaluated to determine whether groundwater conditions had been characterized throughout multiple portions of the aquifer system and whether the monitoring program adequately represented the extent and distribution of PFAS within the investigation area. Consideration of monitoring frequency, well placement, screened intervals, analytical methodologies, and long-term sampling history is essential because groundwater contamination may vary substantially with depth and across different portions of an aquifer. Evaluation of these factors provides important context for interpreting groundwater analytical results and assessing the overall characterization of environmental conditions.
Regulatory review represented another important component of the investigation. Published guidance addressing PFAS investigation, groundwater monitoring, environmental site characterization, and contaminant fate and transport was reviewed to ensure that the evaluation remained consistent with accepted scientific principles and recognized environmental investigation practices. Regulatory agencies have increasingly emphasized comprehensive groundwater characterization, long-term monitoring, and hydrogeologic evaluation as essential components of PFAS investigations due to the persistent nature of these compounds and their potential for long-term migration within groundwater systems. Evaluation of these accepted methodologies provides additional confidence that the investigation reflects current scientific understanding of PFAS behavior within the environment.
Finally, the investigation employed accepted principles of uncertainty evaluation that are fundamental to environmental forensic science. Groundwater investigations inherently involve uncertainty because subsurface conditions cannot be directly observed throughout the entire aquifer and environmental sampling represents only discrete measurements collected over time and space. Rather than treating these limitations as barriers to scientific evaluation, accepted environmental consulting methodologies explicitly recognize uncertainty and address it through integration of multiple years of groundwater monitoring, hydrogeologic interpretation, analytical chemistry, historical site information, and accepted contaminant transport principles. The resulting evaluation therefore reflects a weight-of-evidence approach that synthesizes available scientific information into a technically supported reconstruction of historical groundwater contamination while remaining consistent with accepted principles of environmental forensics, hydrogeology, groundwater investigation, and contaminant fate and transport.
Results
Review of the available environmental documentation demonstrated that PFAS groundwater contamination could be evaluated using a scientifically defensible combination of groundwater analytical data, hydrogeologic interpretation, long-term environmental monitoring, and accepted contaminant fate and transport methodologies. Although individual groundwater sampling events provide only a snapshot of subsurface conditions at a particular point in time, the technical information reviewed included multiple years of groundwater monitoring from numerous monitoring locations completed within different portions of the aquifer system. Collectively, these data provided a substantial body of scientific evidence from which contaminant distribution, groundwater flow characteristics, and long-term concentration trends could be evaluated using established principles of environmental forensics and groundwater investigation.
One of the principal findings of the investigation was the consistency of PFAS detections across multiple groundwater monitoring events and hydrostratigraphic intervals. Evaluation of the available analytical data demonstrated that PFAS compounds were detected within groundwater throughout portions of the monitoring network over an extended period of investigation. Review of historical sampling results illustrated that groundwater monitoring conducted during multiple investigation phases provided a more comprehensive characterization of contaminant occurrence than could be obtained from any single sampling event. Integration of these independent monitoring datasets increased confidence in the interpretation of groundwater conditions and provided a scientifically supported basis for evaluating long-term contaminant distribution.
The investigation further demonstrated that contaminant concentrations varied among monitoring locations and groundwater intervals, reflecting the influence of hydrogeologic conditions on contaminant migration throughout the subsurface environment. Monitoring wells completed at different depths frequently exhibited differing concentration patterns, illustrating the importance of evaluating groundwater conditions within the context of the underlying hydrogeologic framework rather than interpreting individual analytical results in isolation. These observations are consistent with accepted groundwater investigation practices, which recognize that contaminant transport is influenced by aquifer stratigraphy, groundwater flow, hydraulic gradients, and subsurface heterogeneity.
Evaluation of the groundwater monitoring data also demonstrated the value of long-term environmental monitoring in characterizing PFAS contamination. Repeated sampling over multiple years allowed temporal trends in groundwater concentrations to be evaluated while reducing the uncertainty associated with isolated analytical measurements. Historical monitoring results provided important information regarding contaminant persistence, changes in groundwater concentrations over time, and the overall stability of the groundwater plume. This long-term perspective strengthened the environmental forensic evaluation by allowing groundwater conditions to be interpreted using multiple independent datasets collected under varying environmental conditions.
The investigation additionally demonstrated the importance of integrating groundwater analytical chemistry with hydrogeologic interpretation. Groundwater elevations, monitoring well locations, and hydrostratigraphic relationships provided essential scientific context for interpreting the observed distribution of PFAS throughout the investigation area. Evaluation of groundwater flow characteristics together with analytical chemistry demonstrated that contaminant occurrence was closely associated with the hydrogeologic framework governing groundwater movement. These findings reinforce the importance of evaluating groundwater chemistry and hydrogeology collectively when reconstructing historical contaminant migration and assessing the extent of environmental impacts.
Review of the available documentation further demonstrated that characterization of PFAS contamination requires evaluation of both horizontal and vertical groundwater migration. Monitoring wells completed within multiple groundwater intervals provided valuable information regarding contaminant occurrence throughout different portions of the aquifer system and allowed evaluation of potential migration pathways within the subsurface environment. Consideration of these vertical and horizontal distribution patterns represents a fundamental component of environmental forensic groundwater investigations because contaminant movement is influenced by both groundwater flow direction and the physical characteristics of individual hydrostratigraphic units.
Another important finding involved the integration of environmental chemistry, hydrogeology, groundwater monitoring, contaminant fate and transport, and environmental forensics into a unified scientific framework. No single monitoring event or analytical dataset independently characterizes the complexity of PFAS contamination within groundwater systems. However, when historical groundwater monitoring data, hydrogeologic interpretation, analytical chemistry, long-term environmental sampling, and accepted contaminant transport methodologies are evaluated collectively, they provide a technically supported basis for reconstructing historical groundwater contamination and evaluating contaminant migration. This multidisciplinary, weight-of-evidence approach represents a fundamental principle of environmental forensic investigations involving persistent groundwater contaminants and provides a scientifically reliable framework for evaluating PFAS occurrence within complex hydrogeologic environments.
Conclusions
The available technical documentation provides a comprehensive scientific foundation for evaluating PFAS groundwater contamination using accepted principles of environmental forensics, hydrogeology, environmental chemistry, contaminant fate and transport, and groundwater investigation. Although groundwater investigations frequently involve environmental data collected over many years from numerous monitoring locations, the integration of analytical chemistry, hydrogeologic interpretation, historical groundwater monitoring, and accepted environmental investigation methodologies provides a scientifically reliable framework for reconstructing contaminant migration and evaluating groundwater conditions. This multidisciplinary approach allows environmental professionals to characterize groundwater contamination using methods that are consistent with accepted scientific practice and widely recognized within the environmental consulting profession.
The investigation demonstrated that groundwater contamination is most reliably characterized when groundwater analytical results, hydrogeologic information, monitoring well data, historical sampling events, and contaminant transport principles are evaluated collectively rather than independently. This weight-of-evidence approach reduces uncertainty by integrating complementary sources of technical information and allows environmental scientists to evaluate contaminant distribution using methodologies that are both scientifically rigorous and consistent with accepted environmental forensic practice. Long-term groundwater monitoring, together with hydrogeologic interpretation and environmental chemistry, provides a technically supported basis for evaluating historical contaminant migration while recognizing the natural complexity of subsurface groundwater systems.
Review of the supporting documentation also illustrates the importance of evaluating groundwater contamination within the context of the underlying hydrogeologic framework. Groundwater flow direction, aquifer stratigraphy, hydraulic gradients, monitoring well placement, and contaminant chemistry all influence the movement and persistence of PFAS within subsurface environments. Environmental forensic investigations that incorporate these factors provide a more technically accurate understanding of groundwater contamination than evaluations based solely upon isolated analytical measurements or individual sampling events. Consideration of both temporal monitoring trends and hydrogeologic conditions is therefore essential for developing scientifically defensible interpretations of historical groundwater contamination.
The investigation further demonstrated the value of comprehensive groundwater monitoring programs in characterizing persistent environmental contaminants. Repeated sampling conducted over multiple years provides important scientific information regarding plume stability, contaminant persistence, and long-term groundwater conditions while reducing uncertainty associated with individual sampling events. Evaluation of groundwater monitoring data collected from multiple hydrostratigraphic intervals also improves understanding of both horizontal and vertical contaminant migration, thereby providing a more complete characterization of groundwater conditions than could be achieved through a limited monitoring network or short-term investigation.
More broadly, this investigation demonstrates how modern environmental consulting integrates hydrogeology, environmental chemistry, contaminant fate and transport, groundwater monitoring, exposure science, and environmental forensics to address complex groundwater contamination investigations. These multidisciplinary evaluations provide scientifically supported assessments of historical environmental conditions while remaining grounded in accepted hydrogeologic principles, published scientific literature, long-term environmental monitoring, and objective technical analysis. By combining groundwater analytical data with hydrogeologic interpretation and accepted contaminant transport methodologies, environmental forensic investigations are able to develop reliable evaluations of PFAS groundwater contamination that are consistent with recognized scientific practice and contemporary environmental investigation methodologies.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist, environmental forensic expert, and exposure assessment specialist with more than twenty-five years of experience evaluating groundwater contamination, environmental chemistry, contaminant fate and transport, hydrogeology, and human health risk. Throughout his career, Dr. Rosenfeld has conducted investigations involving per- and polyfluoroalkyl substances (PFAS), chlorinated solvents, petroleum hydrocarbons, pesticides, heavy metals, volatile organic compounds, polycyclic aromatic hydrocarbons, asbestos, radionuclides, and numerous other environmental contaminants affecting groundwater resources, drinking water supplies, occupational environments, and surrounding communities. His professional experience includes groundwater investigations, contaminant transport evaluation, environmental site characterization, exposure assessment, quantitative risk assessment, regulatory review, and expert witness testimony involving complex environmental contamination matters.
References
Agency for Toxic Substances and Disease Registry. (2021). Toxicological Profile for Perfluoroalkyls. U.S. Department of Health and Human Services.
Anderson, R. H., Long, G. C., Porter, R. C., & Anderson, J. K. (2016). Occurrence of select perfluoroalkyl substances at U.S. Air Force aqueous film-forming foam release sites other than fire-training areas: Field-validation of critical fate and transport properties. Chemosphere, 150, 678–685.
Interstate Technology & Regulatory Council (ITRC). (2023). PFAS Technical and Regulatory Guidance Document and Fact Sheets. Interstate Technology & Regulatory Council.
International Agency for Research on Cancer. (2024). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. International Agency for Research on Cancer.
National Academies of Sciences, Engineering, and Medicine. (2022). Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. National Academies Press.
Post, G. B., Cohn, P. D., & Cooper, K. R. (2012). Perfluorooctanoic acid (PFOA), an emerging drinking water contaminant: A critical review of recent literature. Environmental Research, 116, 93–117.
U.S. Environmental Protection Agency. (2024). PFAS Analytical Tools. Office of Water.
U.S. Environmental Protection Agency. (2024). Technical Fact Sheet – Perfluorooctanoic Acid (PFOA). Office of Land and Emergency Management.
U.S. Environmental Protection Agency. (2024). Technical Fact Sheet – Perfluorooctane Sulfonate (PFOS). Office of Land and Emergency Management.
U.S. Environmental Protection Agency. (2024). Regional Screening Levels (RSLs) for Chemical Contaminants. Office of Land and Emergency Management.
U.S. Environmental Protection Agency. (2024). Integrated Risk Information System (IRIS). Office of Research and Development.
U.S. Geological Survey. (2023). Per- and Polyfluoroalkyl Substances (PFAS) in Groundwater. U.S. Geological Survey.
Washington, J. W., Ellington, J. J., Jenkins, T. M., & Evans, J. J. (2009). Analysis of perfluorinated carboxylic acids in soils: Detection and environmental implications. Journal of Chromatography A, 1216, 4013–4018.
Xiao, F. (2017). Emerging poly- and perfluoroalkyl substances in the aquatic environment: A review of current literature. Water Research, 124, 482–495.