Aquifer Characterization and Groundwater Potential Assessment of the Sedimentary Basin of Ondo State

The sedimentary basin of Ondo State, underlain by the Coastal Alluvium, Coastal Plain Sands, Imo Shale Group, Upper Coal Measures and Nkporo Shale, was investigated using integrated electrical resistivity and borehole lithologic logs with a view to characterizing the aquifer and assessing the groundwater potential. One hundred and four Vertical Electrical Soundings (VES) were quantitatively interpreted using the partial curve matching technique and computer assisted 1-D forward modeling. Fourteen (14) borehole lithologic logs were used to generate columnar sections from which aquifer units were delineated. Geoelectric sections were generated from the VES interpretation results, constrained by borehole lithological logs, for aquifer identification and geoelectric parameter determination. Depths to top and thicknesses of the aquifer units within each geologic unit were determined. Four aquifer units were identified within the Coastal Alluvium/Coastal Plain Sands. The depths to top/thicknesses of the aquifer units were 5–23 m (7–26 m); 7–80 m (6–67 m); 63-188 m (20-143) and 245–261 m (61–117 m) respectively. Within the Upper Coal Measures, two aquifer units were identified. The depths to the top/thicknesses of the aquifer units were 9.8 m (1.7 m) and 23 m (5.3 m) respectively. The Nkporo Shale had depth to top and thickness of the only identified aquifer unit as 10 m and 16 m respectively. The study concluded that the groundwater potential of the Coastal Alluvium and Coastal Plain Sands was high while the groundwater potential of the Imo Shale Group, the Upper Coal Measures and Nkporo Shale was adjudged low

Geophysical and geotechnical characterisation of foundation beds at Kuchiyaku, Kuje Area, Abuja, Nigeria

The geoelectrical and geotechnical parameters of foundation soils in Kuchiyaku, Kuje area, Abuja, Nigeria were determined. The exercise was aimed at evaluating the competence of near surface geomaterials to bear civil engineering loads. The study combined 20 Schlumberger Vertical Electrical Soundings (VES), in-situ tests involving 19 Standard Penetration Tests (SPT), 15 Cone Penetration Tests (CPT), and multiple Atterberg's laboratory tests (liquid and plastic limits). The VES interpretations delineated topsoil, weathered basement and the fractured/fresh bedrock within the study area. The layer resistivity ranges from 199 to 1947 Ohm-m for topsoil, 32 to 540 Ohm-m for weathered basement and 495 to 16986 Ohm-m for fresh/fractured bedrock. High resistivity values (>500 Ohm-m) suggest geotechnical competence. Maximum depth to bedrock is about 31m. The cone penetration probed maximum depth of 6.4m at CPT 13 and 10m depth was reached by the standard penetration test via sample holes. The geophysical interpretation results correlated well with the results of CPT, SPT and laboratory Atterberg's tests in the study area. High CPT and SPT values have direct correlation with high resistivity values where there is no much differential in soil fluid content, while areas with high liquid and plastic limits correlate with resistivity low zones, apparently suggesting high groundwater saturation. The Atterberg's limits observed from borehole samples revealed useful knowledge of the soils' engineering properties. The investigation reveals that the near surface foundation materials in the area is generally geotechnically competent