Using aerial time-domain electromagnetic surveys to quantify storage change in copper heap leach recovery.

Guy Wall¹, Chloe Codner¹ Iosif Xiradakis¹, Natalie Yurek¹, Neha Gupta², Stefano Nerozzi³, T.P.A. Ferré¹, Jacob Taylor³

¹Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ

²Arizona Institute for Resilience, University of Arizona, Tucson, AZ

³Department of Planetary Sciences, University of Arizona, Tucson, AZ

Heap leach recovery is a commonly used mining practice that layers low-grade ore on surficial leach pads where an acidic solution, “lixiviant,” can percolate and dissolve target metals along its flow path. Ore recovery and long-term reclamation outcomes are heavily dependent upon lixiviant flow efficiency. Prior studies have shown that flow behavior in leach pads is governed by structural design, variable hydrogeologic properties, and physiochemical reactions. These studies have used methods including both physical characterization and geophysical imaging. Electrical resistivity tomography (ERT) has been the primary geophysical tool applied to heap leach systems, delineating moisture distributions, perched zones, and preferential flow paths. However, time domain electromagnetic (TDEM) methods remain underutilized in heap leach monitoring despite having demonstrated success in more general hydrogeologic investigations.

This study evaluates the use of aerial TDEM surveys to quantify dewatering in a copper heap leach pad undergoing drainage through horizontal drains. Datasets spanning multiple years will be used to track temporal changes in subsurface conductivity as an indicator of evolving moisture content. This work demonstrates the potential of TDEM to identify and quantify storage change from features that induce preferential flow, seepage, and solute perching within heap leach stockpiles. The results position TDEM as a potential tool for monitoring heap leach performance, informing operational decisions, and optimizing ore recovery.