At a former ordinance plant in Nebraska, an estimated 23 billion gallons of groundwater were contaminated with RDX and TCE above regulatory standards. The site’s extensive pump-and-treat system successfully contained the plume, but projections estimated it would need to operate for more than 125 years to lower the concentrations below standards. The project team agreed that more than a century was too long and recognized the need for a more efficient solution.
To identify a more effective path forward, ESTCP funded a pilot-scale ISCO test using permanganate injections. The problem? Twelve monitoring wells and eight direct-push profiles couldn’t show where the injected material traveled underground. Without directed delivery of the permanganate solution, the ISCO pilot was destined to fall short.
Enter Temporal Electrical Resistivity Imaging (TERI)—a game-changer for subsurface visibility. Unlike static imaging, TERI measures changes in electrical resistivity over time—before, during, and after injection. Because injected materials conduct electricity differently than the surrounding soil and groundwater, TERI can track their movement in remarkable detail.
In this project, TERI captured injection behavior with high-sensitivity down to 100 feet below ground surface (30 m). The images told a surprising story:
These insights provided by TERI were spot-on: later groundwater sampling confirmed the predictions of detection of injectate in one well (MW-13) and non-detection in another (MW-03), see the graphic below.
The takeaway? Injected materials rarely behave as expected. Continuous, high-resolution imaging can uncover hidden flowpaths, delineate radius of influence horizontally and vertically, and refine cleanup strategies that monitoring wells alone may miss.
Better visibility below ground leads to better remedial decisions, and faster progress, above it.
