Use of the electrical resistivity method in the investigation of the axis of a small earth dam, angware area, jos plateau, northcentral nigeria

An engineering geophysical investigation of the site of the proposed Jarawa Kogi small earth dam, located in Joseast Local Government Area (L. G. A), Plateau State, Nigeria, was carried out. The investigation involved the electrical resistivity method which utilized the Schaumberg array. A total of twelve (12) vertical electrical sounding (VES) stations were occupied along the proposed dam axis. Four subsurface layers were delineated. These include, from top to bottom, the topsoil, a laterite layer, a weathered basement layer and the bedrock. Overburden thickness along the axis is quite significant, with depth to the competent bedrock in the range of 4.9 - 39.3 m. Generally, the Basement slopes onto the current position of the river channel. This disposition will aid base flow into the river channel from the shoulders. The bedrock is characterized by two major depressions and two minor depressions. These depressions act as receptacles for thick accumulation of alluvium. The fracture zone delineated in the bedrock is limited, so that it may not pose serious problem to the integrity of the proposed dam. The bedrock is directly overlain by a thick layer thought to be weathered material. This material may not help prevent water seepage through the foundation of the dam embankment. Also, all metallic objects to be buried underground must be treated against corrosion.