Assessment of Aquifer Propensity to Degradation around Dumpsites in Port Harcourt, Nigeria Using Vertical Electrical Sounding

Dumpsites are associated with contaminants. If unprotected, the contaminants have tendency to flow or percolate into the subsoil thereby polluting shallow ground water. Vertical Electrical sounding method was employed in this investigation to evaluate the vulnerability of aquifers to contamination by leachate produces by a mass of decomposing waste. The VES survey results as interpreted with WIN RESIST version 1 show curve types ranging from H, KH, HKA, AQH, and KHK to HKA. The result was used to calculate the longitudinal conductance of the layers and consequently its prospective capacity/vulnerability of the aquifer at the VES stations. 92% of the dumpsites have poor protective layer with conductivity less than critical value of 1.0 Siemens. Sites toward the northern part of the study area (Eliozu, Eneka and Rumueme) have poor protective capacity while the southern section (Rivers State University and Rumuolumeni) have enough clay to protect groundwater against contamination. Generally, 62% of sites investigated are not safe, 15% have weak to moderate protection while 8% of the sites are properly protected. The results also revealed the geology and lithological sequence as comprising Top soil, clay/silt, lateritic soil, sand, fine sand, coarse sand and gravel. It is therefore recommended that detailed geophysical investigation of the underlying subsurface strata be carried out before a site is approved as a dumpsite and even drilling of water supply boreholes.