Applied Geophysics To Investigate Groundwater Pollution Flow Paths Along A Fault System In An Industrial Environment

A fault system may form preferential flow paths for groundwater along fault planes. In an industrial and mining environment, such geological structures pose a geohydrological challenge when delineating and managing groundwater pollution. A geophysical investigation, employing electric resistivity tomography (ERT) and electromagnetics (EM), was conducted along a section of a graben system to improve the geological understanding, define groundwater flow paths and pollution distribution in a mining and industrial setting. Additionally, the geophysical survey assisted in the siting of monitoring boreholes to gain an understanding of the geohydrological properties within the fault system. A total of 35 profiles were completed along a 12 km section of the graben including a refined grid around a water-filled quarry with elevated salinity. The geophysical results confirmed the presence of faults and indicated zones of lower apparent resistivity along the graben. Areas of elevated conductivity were modelled near industrial and mining operations, such as ash tailings, discard dumps and mine-water dams, suggesting that leachate could potentially seep into the underlying aquifers. A refined ERT model around the quarry indicated areas of high conductivity at dolerite contacts, fault planes and within a backfilled area which could form preferential groundwater flow paths from and to the quarry. This study showed that a fault system underlying industrial and mining activities with high conductivity zones could distribute seepage along secondary geological structures but could also aid as a barrier between different aquifer systems. An outstanding groundwater chemistry analysis is expected to provide further insight whether the detected groundwater flow paths along the fault planes contribute to the distribution of pollutants across the industrial site. Overall, the geophysical survey and consequent siting of monitoring boreholes were useful tools to identify groundwater flow paths for pollutants across a large scale structure to implement future water management plans.