A geophysical study was carried out at a proposed location for the construction of a structure along Ado-Afao road, Southwestern Nigeria. The aim of the study is to evaluate the electrical properties of the soil for Founding of Engineering structures. The geophysical investigation involved the Vertical Electrical Sounding (VES) technique using the Schlumberger configuration with a total of twenty-one (21) VES within the investigated area. The electrode separation varies from 1 to 100 m. The geoelectric sections identified three to five geoelectric/geologic subsurface layers along the traverses. The topsoil comprising of clay, clayey sand and sandy clay with the resistivity values range from 28 to 800 Ω-m with its thickness varying from 0.4 to 1.9 m. The second layer was found to be lateritic with resistivity ranging between 200 to 800 Ω-m and thickness ranges from 1 to 7.5 m while the weathered layer comprising of clay, clayey sand and sandy clay with resistivity varies from 30 to 220 Ω-m and its thickness varies from 1.2 to 54 m. The fractured basement with resistivity value of 763 Ωm and thickness value of 8m while the fresh basement has a resistivity value ranging from 365 to 2964 Ωm with depth to basement ranging from 8 to 58 m. The resistivity values of the topsoil are indicative of clay, sandy clay and clayey sand. This layer may not be of any special interest since topsoil is normally excavated. Hence, foundation of the proposed structures cannot be found on this layer. Based on the investigation, the subsurface of the study area can be generally classified as incompetent. There is a presence of lateral inhomogeneity of the subsurface layers and geologic features such as fractures and faults. The construction in the area should be founded on the lateritic layer or fresh basement layer coupled with pile foundation to ensure the stability of the building. The choice of foundation material, clay content and topography elevation should be put into consideration.

Lithology, elevation and four (4) geoelectric parameters were utilized in assessing the groundwater vulnerability at northwestern part of Akure, southwestern Nigeria. Vertical electrical sounding (VES) technique of electrical resistivity method was adopted for this work. A total of 224 VES data was acquired and interpreted both qualitatively and quantitatively. Three to five geo-electric layers were delineated across the area which corresponds to four geologic layers. The resistivity of the layers varies respectively from 6.9 - 550 Ohm-m, 60 - 2500 Ohm-m, 20 - 650 Ohm-m and 220 - 7900 Ohm-m in the topsoil, weathered layer, partially weathered basement/partially fractured basement and presumed fresh basement. Likewise, the layer thicknesses also vary respectively from 0.4 - 4.0 m, 0.7 - 19.0 m and 4.0 -60 m in the topsoil, weathered layer and partially weathered basement/partially fractured basement. The results were presented as topsoil (resistivity and thickness) and weathered layer (resistivity and thickness) maps. The six parameters consisting of lithology, elevation, topsoil (resistivity and thickness) and weathered layer (resistivity and thickness) were synthesized using an additive model in order to generate the aquifer vulnerability model map. The aquifer vulnerability model map shows that the area is of very low to moderate vulnerability with 5% of the area having very low vulnerability, 30% low vulnerability and 65% moderate vulnerability. This implies that the groundwater resources in the area are moderately safe.