Professional Evaluation of Solid Waste Landfill Sites Using Geophysical Methods in Kaduna State, North West Nigeria

Kaduna State generates over 1,800 tonnes of municipal solid waste daily, and the selection of environmentally suitable landfill sites requires rigorous geophysical site investigation to ensure that natural geological barriers provide adequate protection to groundwater resources. This professional study evaluates three candidate landfill sites in Kaduna metropolis using electrical resistivity tomography, electromagnetic profiling, and seismic refraction to assess their geological suitability based on the Federal Ministry of Environment guidelines for landfill siting. ERT profiles of 400 metres were acquired at each site along orthogonal directions. EM34 profiling at coil separations of 10 and 40 metres provided rapid preliminary conductivity screening. Seismic refraction traverses characterised the depth to fresh bedrock and the velocity structure of the overburden. Site A, in Kabala West, shows the most favourable characteristics: a continuous clay-rich weathered layer of 8 to 14 metres thickness with measured resistivities of less than 20 ohm-metres consistent with low hydraulic conductivity, overlying fresh granite. Site B in Rigasa lacks an adequate clay barrier, with resistivities exceeding 80 ohm-metres throughout the profile, indicating sandy permeable overburden. Site C has an adequate clay layer in its western half but is underlain by a mapped fault that could act as a contaminant bypass pathway. The study recommends Site A as the geophysically most suitable candidate and provides a leachate migration risk assessment for regulatory review. Keywords: landfill siting, ERT, clay barrier, Kaduna, solid waste