Unraveling Flow Pathways in Fractured Basalt under Challenging Environmental Conditions: A Synergistic Approach of Electrical Resistivity Tomography and Seismic Refraction Imaging

Abstract The understanding of the site conceptual flow model in fractured-controlled aquifers near landfills and open dumpsites is a challenge for monitoring groundwater pollution as it answers several key issues related to environmental processes. In such hazardous environments, it is essential to define the hydrogeological processes and identify the potential pathways for contamination migration near the dumping sites. Thus, the understanding of fractured basalt characterization with suitable spatial resolution is one of the interesting issues and still open areas of research. This study investigates the potential of combining Electrical Resistivity Tomography (ERT) and Seismic Refraction Imaging (SRI) techniques for understanding a site conceptual flow model in fractured basalt under a hazardous environment. The research was conducted in an area with a history of environmental contamination, where fractured basalt serves as a major pathway for the migration of pollutants. In the considered case study, the SRI identifies a shallow water table and attests that the contact of the saturated fractured basalt (1200–1850 m/s) and the massive basalts (>3000m/s) is highly heterogeneous. In addition, the presence of NW conductive and interflow zones (5-10 Ωm) at depths of 5 to 12 m, which could provide a vertical hydraulic connection with the lower aquifer, allows the local percolation of the leachate in the area around the dumpsites. These results show the advantage of the applied approach for delineating the strikes of the prevailing fracture patterns and clarifying the pollution situation at typical composite landfills worldwide. Accordingly, the site conceptual flow model is critical for improving the understanding of hydrogeological and transport processes in such hazardous environments to achieve sustainable management of groundwater resources, as well as for the monitoring of remediation performance.