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Mapping High-TDS Groundwater Near Impoundments Using Ground and Waterborne Towed Electromagnetics
Piyoosh Jaysaval, Jonathan N Thomle1, Esteban J Bowles-Martinez1
1Pacific Northwest National Laboratory, Earth and Environmental Systems Division, Subsurface Science Group, 902 Battelle Boulevard, Richland, WA, 99352.
Ground Water
|December 30, 2025
Summary
Towed time-domain electromagnetic (TEM) surveys offer a non-invasive method to assess groundwater quality near industrial waste sites. This geophysical approach effectively maps potential leachate plumes by detecting electrical conductivity anomalies.
Area of Science:
- Environmental Geophysics
- Hydrogeology
- Geophysical Surveying
Background:
- Long-term monitoring of landfills and impoundments containing coal combustion products (CCPs) or industrial wastes is crucial for detecting leachate releases.
- Groundwater contamination plumes from such sites often exhibit elevated total dissolved solids (TDS), leading to increased electrical conductivity.
- Electromagnetic (EM) methods are suitable for detecting and monitoring these high-TDS plumes due to their sensitivity to electrical conductivity variations.
Purpose of the Study:
- To evaluate the effectiveness of towed time-domain electromagnetic (TEM) surveys for non-invasive and rapid assessment of groundwater quality near waste impoundments.
- To investigate the capability of TEM surveys in delineating geological structures and identifying potential leachate plumes with high TDS.
- To demonstrate the application of integrated ground-based and waterborne TEM surveys for characterizing sites with potential for leachate releases.
Main Methods:
- Conducted integrated ground-based and waterborne time-domain electromagnetic (TEM) surveys over a coal combustion product (CCP) complex adjacent to a river.
- Acquired over 20 line-kilometers of TEM data, employing advanced antennas towed by vehicles and boats.
- Utilized laterally constrained 2D and spatially constrained 3D inversions to process the acquired TEM data for subsurface imaging.
Main Results:
- Successfully collected high-quality TEM data despite challenging site conditions, including industrial infrastructure and power lines.
- Delineated geological boundaries and identified conductive anomalies consistent with elevated TDS, indicative of potential leachate plumes.
- Geophysical interpretations from TEM data showed strong agreement with existing water-quality data from monitoring wells.
Conclusions:
- Towed TEM surveys provide a rapid, non-invasive, and effective geophysical approach for assessing groundwater quality and mapping contamination plumes near industrial waste sites.
- Integrated ground-based and waterborne TEM surveys enable high-resolution characterization of subsurface conditions around CCP impoundments.
- This geophysical method offers a valuable tool for environmental monitoring and management of sites with potential for leachate releases.
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