Expanding Hydro-Geotechnical Considerations in Eia Studies: A Case Study of Ogorode – Sapele, Delta State, Nigeria

Abstract

Hydro-geotechnical mapping of the study area, which lies within the Sombreiro – Warri deltaic plain in the Niger Delta area, comprised the drilling of representative boreholes as monitoring wells. Three (3) boreholes were sunk in the area with soil and water samples collected for laboratory analyses according to Department of Petroleum Resources (DPR) and international standards. The physical properties of the soils were determined and used as indices of their infiltration capacity and classification. Water quality analysis was for physicochemical and microbiological parameters. Boreholes logged to the maximum – drilled depth of 10m, revealed fine – grained, high plasticity clay and medium to coarse –grained sands with fines of silt and clay overlying the aquifer. Static water levels were in the range of 1.2 to 2.0m below ground elevation. The aquifer was determined to be confined in one area but was mostly semi – confined (leaky) and this condition may permit gradual infiltration of pollutants into the upper aquifer. Environmental hazards that may occur in the area may include sheet erosion and flooding. It is recommended that the provision of dedicated flow lines will ensure a flood free environment.