Geophysical Assessment of Leachate Migration and Aquifer Protective Capacity of Cassidy Dumpsite, Ojo, Lagos State, Nigeria

Abstract

Vertical electrical Station (VES) prospecting and two-dimensional (2d) resistivity imaging were used to assess the leachate displacement and aquifer protection potential at the Cassidy landfill in Lagos, Nigeria. Twenty–six VES and four 2D resistivity profiles were acquired. Leachate contamination was evaluated using the longitudinal conductivity (S) parameter derived from the apparent resistivity and thickness values. Analysis of VES and 2D resistivity data was done using WinResist and DIPROFWIN Software respectively.  Three to six geological layers derived from VES data include topsoil, clay, sand, clay-sand, sandy clay, and clay/leachate. The 2D resistivity configuration revealed that the lateral and vertical subsurface resistivity values were spanning from 6 Ωm to 138 Ωm. Three different aquifer protection potential zones were diagnosed with protection capacities of 36%, 52%, and 12%, respectively. Zones with adequate aquifer protection have good damping properties for contaminated liquids. Leachate Infiltration varies between 4.8 m and 17.0 m depth.  Protection capacity should not be neglected in planning areas for groundwater exploration, and zones with low vulnerability and moderate or high groundwater protection potential should be optimally used.