Various types of landfills pose a direct threat to groundwater. Polluted groundwater is characterized by significantly reduced electrical resistivity. Geophysical methods – in particular DC-resistivity methods – are sensitive to this physical parameter. Applying these methods can allow for a spatial assessment of the groundwater quality near the landfills. The key with that approach is to recognize the geoelectrical structure of an area prior to the existence of a landfill. This information will allow for a geoelectrical background, which would most likely be an image of the natural and uncontaminated study area. Subsequent measurements will be more effective due to the possibility of comparing the current state of the area to the original state. This paper presents an example of such a study. Here, the research area of interest was located in the vicinity of an inactive tailings disposal site. In order to assess the pollution of the groundwater, a vertical electrical sounding method was applied. The results of modern measurements were compared with those from the reinterpretation of the data obtained several decades ago. The selected geoelectrical method proved to be effective, allowing for the determination of the range of contaminated groundwater in regions that were not covered by traditional hydrogeological monitoring by a piezometer network. Repetition of vertical electrical sounding in the future will allow for tracking the displacement of pollution within the aquifer.