Identification of Contaminated Zones Using Direct Current Resistivity Surveys in and Around Ash Ponds Near Kolaghat Thermal Power Plant, West Bengal, India

Lack of proper insulation at the bottom of the ash disposal ponds enhances the chances of groundwater contamination. In this study, direct current (dc) resistivity survey, employing Schlumberger configuration, was undertaken to identify the local subsurface and to estimate the depth of contamination around ash ponds near a thermal power plant in Eastern India. A continuous conductive zone with resistivity < 5 Ω m was identified throughout the studied region at a depth of about 2–10 m indicating the presence of water with higher ionic concentration. This can be due to the leached soluble species that percolate downwards with the slurry water in the form of leachate. The continuity of this zone from inland towards the river can pose a threat to the groundwater as well as the overall health of the river ecosystem. Geophysical method utilized in this study is fast, efficient and cost-effective in delineating the extent of the probable contamination zone(s).