Lithological Characterisation and Suitability of the Sub-Soils and Bedrocks Around Lapite Municipal Dumpsite as Liner Materials at Akinyele Area of Ibadan, Southwestern Nigeria

Dumpsites are land areas assigned for solid waste deposition and accumulation that are liable to contaminate the sub-surface environment and underground water, hence; the underlying soils and bedrocks in such areas should be impervious to leachates plume. In this regard, the present study applied a total of forty-one vertical electrical soundings (VES) geophysical resistivity method to characterize the lithology of the subsurface soils and bedrocks around the Lapite dumpsite at Akinyele area of Ibadan. The aim is to assess the worth of the underlying natural materials as suitable liners for the dumpsite and the vulnerability of the area to leachate contamination. From the results, the dominant VES curve across the study area are the 3-layer H and the 4 – layer KH types characterised by more conductive middle sub-soil layer. The overburden thickness varied widely between 1.5 to 42.3 m, which is considered thick enough as liner materials for the dumpsite. The bedrock resistivities were 10 – 12,962 Ωm Ωm and there are more permeable fractured and weathered bedrocks than the fresh basement. From the lithologic characterisation, 52% of the saprolite layers are predominantly clayey and compacted lateritic clays that are classified as good materials for dumpsite liners. However, the dominant permeable bedrocks of about 76% occurrence are major concern that can substantially permit percolation of leachate and contaminated water into the underground environment despite the favourable overburden thickness and fairly good saprolite lithology. These geo-electric results are not suitable for further extension of the dumpsite. There may be the need to evacuate the dumps or provide suitable liners either by modifying the sub-soils or by providing artificial liners for the area in order to safeguard the safety of the underground water for human. Keywords: Dumpsites, leachate, liner, saprolite, bedrock DOI: 10.7176/JEES/15-2-05 Publication date: March 30th 2025