AEHS West 2025 Presentations
Targeting PFAS Remediation
via Electrical Hydrogeology
Samantha Frandsen (Presenter) - Aestus, LLC
Todd Halihan - Oklahoma State University
Stuart W. McDonald - Aestus, LLC
Kyle W. Spears - Aestus, LLC
It is difficult for environmental professionals to adequately characterize the extent and transport of PFAS and other emerging contaminants in the subsurface. Because approximately 90-percent of groundwater flow and contaminant flux typically occurs in discrete flowpaths, having the ability to adequately characterize these zones dramatically reduces the scope and cost of remedial treatment. Industry data demonstrates these discrete targets are virtually impossible to identify and adequately characterize with monitoring wells alone.
Surface-deployed electrical hydrogeology mapping techniques (i.e., electrical resistivity imaging [ERI]) can be leveraged to target drilling and remediation within the relatively small volume of these systems where the majority of contaminant flux is occurring. The use of dedicated temporal electrical subsurface monitoring systems (temporal ERI [TERI]) offers additional accuracy and remediation system refinement by collecting data on regular intervals to isolate zones of flux based on statistical variability of electrical changes.
This approach offers project stakeholders the opportunity to apply remediation techniques with more precision: monitoring wells and remediation can then be targeted in these high-flux zones where the majority of PFAS is migrating. The use of these ultra-high-resolution datasets facilitates more cost-effective outcomes and avoids potential failed remediation scenarios due to inadequate conceptual site models (CSMs).
Electrical Hydrogeology:
Managing Groundwater Resources with More Certainty
Kyle W. Spears (Presenter) - Aestus, LLC
Stuart W. McDonald - Aestus, LLC
Samantha Frandsen - Aestus, LLC
Todd Halihan - Oklahoma State University
Understanding of groundwater systems has been traditionally based on observations at the ground surface, as well as interpolation of limited single point data from boreholes and wells. In recent years, advanced computing tools have been used to visualize data in 3D and perform sophisticated data interpolations. However, the accuracy of 3D modelling outputs for understanding aquifers is often limited given most of the 3D domain shows interpolated graphical representations, which are generally not well constrained by actual field data points.
Modern subsurface electrical scanning technologies provide much higher data density over larger areas as input to 3D visualization software to output more accurate depictions of flow and transport in aquifers. Specifically, airborne electromagnetic (AEM) surveys provide large-scale coverage of aquifers to detect regional scale flow paths and dominant geologic structures. The use of ground-surface deployed electrical resistivity imaging (ERI) provides even higher resolution targeting of potential drilling locations identified by AEM to optimize characterization of aquifer hydrogeologic parameters in key locations. Additionally, temporal electrical resistivity imaging (TERI) provides high resolution monitoring of aquifer changes over time due to recharge, pumping effects, and/or salinity issues across a continuous 2D domain versus traditional monitoring which only measures changes over time at a single point.
This presentation will review AEM, ERI, and TERI datasets from a site in Oklahoma to characterize the groundwater system and evaluate potential for enhanced aquifer recharge. Data from the various scanning techniques were visualized in 3D to better understand geologic structures, preferential pathways, and aquifer characteristics with more certainty at both the regional and site scales. The resulting conceptual site model (CSM) gave project stakeholders confidence in understanding a complicated fractured carbonate bedrock groundwater system and is providing the basis for further research regarding potential enhanced aquifer recharge to augment water supply for nearby landowners and municipalities.