Hydrogeological monitoring of the Cerro del Lobo tailings storage facility using the geophysical method for sustainable groundwater flow detection and tailings management

Authors: Martínez-Moreno, FJ; Abreu, A; Baltazar-Soares, PA; Fernandes, J; Oliveira, M Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_22

Cite As:
Martínez-Moreno, FJ, Abreu, A, Baltazar-Soares, PA, Fernandes, J & Oliveira, M 2026, 'Hydrogeological monitoring of the Cerro del Lobo tailings storage facility using the geophysical method for sustainable groundwater flow detection and tailings management', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-11, https://doi.org/10.36487/ACG_repo/2655_22



Abstract:
The Neves-Corvo mine, located in Beja district (Lower Alentejo, Portugal), is a polymetallic mine primarily producing copper and zinc. In 1988, the Cerro del Lobo tailings and waste rock storage facility was constructed following the best available practices at the time. The facility is unlined at its base and rests directly on a bedrock of schists and greywackes. A major environmental concern is the potential migration of conductive groundwater beyond the facility’s perimeter. To assess this, the geophysical method of electrical resistivity tomography (ERT) has been applied in recent years along profiles around the Cerro do Lobo and in more distant areas where subsurface water flow is present. ERT involves injecting electrical current through a pair of electrodes and measuring the response with another pair, producing a subsurface resistivity pseudo-section. Combined with geological knowledge, this method allows the identification of subsurface structure and composition, detection of possible groundwater flow paths, and identification of low-resistivity zones, guiding the placement of additional monitoring points. Groundwater circulation is typically associated with tectonic structures (faults and thrusts). While infiltration is not evident at the base of the facility, it is detectable in the surrounding areas, gradually decreasing with distance. Chemical analyses from piezometers, installed based on geophysical results, have validated the method’s effectiveness. All geophysical information has been incorporated into hydrogeological studies, providing direct support for the mine closure plan. This study demonstrates that ERT is a powerful and practical tool for groundwater monitoring in tailings storage facilities, enabling improved understanding of subsurface flow and contributing to sustainable tailings management and environmental protection.

Keywords: tailings storage facility, geophysics, groundwater, subsurface resistivity, tectonic structures, environmental protection

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