Composite Geoelectrical Investigation to Delineate Groundwater Feasibility in Hard Rock area of Raipur, Chhattisgarh, India.

In hard rock terrains, groundwater movement, migration, and storage occur through subsurface fractures. To assess the fractures and associated water, we carried integrated geophysical investigation with Wenner, (GRP), Schlumberger, and Pole-Dipole array in Indian State. The resistivity survey carried out using a CRM-500 resistivity meter. The analyzed results are also re-verified with the help of IPI2WIN software. Initially, lateral and surface variations of resistivity were plotted by using Wenner and Gradient Resistivity profiling array. Then the low resistivity points were investigated with Schlumberger and Pole-Dipole array. In interpretation, low resistive zones identified correspond to the possible fractured zones. The results allowed mapping of the weathering zone at depth 12 to 15 m, and deep fracture lies below depth 55.0 m depth. The present study validates that the integrated Geophysical survey is a powerful exploration technique to scrutinize and identify water-bearing fractures in the hard rock area.

Geophysical mapping of a classical Greek road network: A case study from the city of Elis, Peloponnese

Many ancient Greek cities are characterised by a regular orthogonal road network. These roads are ideal targets for geophysical investigation mainly due to their extensive geographic extent that makes them challenging to define by excavation. Geophysical mapping of these features will contribute to understanding ancient cities as it can provide considerable information about their geographic extent, spatial arrangement and urban dynamics. Large scale multisensor magnetic and electromagnetic induction methods have been used to map the ancient Greek city of Elis in the Peloponnese (Greece). This work complements other investigations that have been undertaken, employing other methods that include the interpretation of high-resolution satellite imagery (Donati and Sarris forthcoming).

Application of Electrical Resistivity Method to Site Characterisation for Construction Purposes at Institute of Agriculture Research and Training Moor Plantation Ibadan

This research was carried out within Institute of Agriculture Research and Training Moor Plantation Ibadan, Southwestern Nigeria, with the aim to ascertain suitability of the proposed site for building construction and usage. The geophysical investigation involved three electrical resistivity techniques; Vertical Electrical Sounding (VES) using the Schlumberger configuration, 2D ERT and 2-D electrical imaging using Dipole-dipole electrode configuration. Two traverses were established E–W direction cutting across geologic strike with a distance of 80 m and of varying inter-traverse spacing. Eight (8) VES stations were occupied covering the entire study area for layer stratification and geoelectric parameters. The results were qualitatively and quantitatively interpreted and are presented as sounding curves and geoelectric sections. The 2-D imaging gave information on the subsurface characteristic in the area with generally low apparent resistivity indicating low competence material. The results obtained from the VES delineate three geoelectric units which comprise of the topsoil, weathered layer and fresh basement. The results from the VES were used to determine the second order parameters. The entire results correlate well with one another showing that all the techniques used were complemented. This study has further justified the need for geophysical site investigation as pre-condition before any construction to avoid problems of differential settlement. In determining of foundation material, topography elevation, clay content and the depth of weak zones should be put into consideration, since the depth of the weak zone is appreciably high.

GEOTECHNICAL INVESTIGATION OF THE PROPOSED IFE DAM SITE AT KAJOLA VILLAGE, ILE-IFE, SOUTHWESTERN NIGERIA

Geological and geophysical investigations were conducted to assess the competence and structural integrity of the foundation site of the proposed Ife-dam at Kajola Village, Ile-Ife, Southwestern Nigeria. Geological investigation along the two (2) proposed dam axes revealed that the overburden material is loose to dense with angular shearing resistance (ɸ) of 27o to 41o. The soils are predominantly elastic silts; cohesive with considerable strength and stability. Geophysical investigation involving the Schlumberger Vertical Electrical Sounding delineated four (4) lithologies namely: topsoil with resistivity of 69 – 558 Ωm and thickness between 1.5 and 4.0 m; weathered sandy layer with resistivity from 123 – 586 Ωm and thickness between 6.5 and 20.4 m; partially weathered/ fractured basement with resistivity from 60 – 220 Ωm and thickness between 6.5 and 14.0 m; and the fresh basement rock with resistivity from 1337 – 10683 Ωm. There are indications of fractures at a depth of 32 m beneath Axis B extending to Axis A at a depth of 35 m. The subsurface materials are suitable to host a dam. Axis B is more appropriate for the dam axis, although the fracture zone should be factored into the design of the dam to prevent water seepage.

Evaluation of Groundwater in Udi L.G.A. in Enugu State, Nigeria

Groundwater has remained indispensable in Enugu state Nigeria owing to industrialization, lack of surface water, and significant depth to aquifer in the area. A geophysical investigation involving vertical electrical soundings was conducted in order to evaluate groundwater potential at some locations in the Udi Local Government Area of Enugu State. With the aid of resistivity instrument ABEM Terrameter, four (4) Vertical Electrical Sounding using Schlumberger configuration were conducted, and the data acquired was interpreted using WINRESIST software. Information obtains from the survey shows that the underlying geological formation in those areas has between 5 – 7 layers. The apparent resistivity obtained in all the layers of the locations ranges from 47.1 – 6956.8 Ωm, while the aquifer was interpreted to exist at a depth between 90 – 120m. Result obtained from this geophysical investigation has shown that the survey area possesses a good groundwater potential which will go a long way in cushioning the effect associated with water scarcity in the area if exploited.

Groundwater Quality Assessment of Abandoned Dumpsite in Osogbo Suburb, Nigeria: Hydrogeological and Geophysical Condition Six Years after Initial Study

In this paper, we describe the result of a recent hydrogeological and geophysical investigation carried out within and around Aduramigba - Onibu-Eja Estate dumpsite with the aim of detecting evidence of contamination as well as depths to contamination of the groundwater after a previous study six years ago. Twenty water samples from shallow water wells and boreholes were analyzed for their physico-chemical constituents while five vertical electrical soundings and five electromagnetic ground penetrating radar surveys were conducted. The result shows high concentrations of anions of nitrates (NO3-), bicarbonates (HCO3-), chloride (Cl-) and sulphate (SO42-) with values of 73.97 mg/l, 91.5 mg/l, 331.2 mg/l, 222.4 mg/l respectively, cations values of Mg2+, Fe2+, Na+, and K+ having value of 25.44 mg/l, 6.23 mg/l, 37.31 mg/l and 35.41 mg/l, respectively, which were far above the World Health Organization (WHO) and Nigeria Drinking Water Quality Standard (NDWS). Heavy metal components such as Lead, Zinc, Copper and Nickel were also observed to be on the high side, having been contributed from effluents from rust metallic materials cum chemicals dumped within the dumpsite. Detailed geophysical study reveal the depth to contamination at between 4.1 meters in VES 3 to 5.9 meters in VES 2 with resistivity as low as 5.12 Ωm in VES 2 to 7.12 Ωm in VES 3 while ground penetrating radar (GPR) revealed that the leachate has permeated to a depth of 3.5 – 5.25 meters in traverse 4 and 4.0 – 6.0 meters in traverse 3 which correspond to the depth to unconfined aquifer within the dumpsite. The study conclude that this would pose a greater threat to residents living in this vicinity and as such, this might have contributed to the closure of the dumpsite.