Geophysical Investigation of Groundwater Contamination levels in Obiaruku Waste Dumpsite Using Vertical Electrical Sounding Method

Abstract

The geophysical well logs investigation of groundwater contamination level in waste dumpsites using vertical electrical sounding method in Obiaruku- Amai dumpsite in Ukwani Local Government Area of Delta State has been conducted. Five VES points were strategically mapped within and around the study area (dumpsite) using the Global Positioning System (GPS). The resistances of the soil profile where examined at the different VES marked points. The ABEM SAS 4000 Terameter with the Schlumberger array configuration approach was used and the resistivity values were recorded. A computer iteration techniques using Resist Version 1 was used to evaluate the curves type and to determine the numbers of layers. The raw data was subjected to computer iteration and smoothened. The interpreted data show that four geoelectric layers underlie the study area. The vertical electrical sounding curves shows AA, HK, AH, AA and HA types for VES I to VES V respectively. The average resistivity values obtain down the aquifer ranged from 234 Ωm to 3475.1 Ωm for VES I; 229.2 Ωm to 8817.2 Ωm for VES II;
1514.3 Ωm to 3864.8 Ωm for VES III; 115.6 Ωm to 3864.8 Ωm for VES IV; 36.8 Ωm to 3101.1 Ωm for VES V. Locations 3 was analyzed to have the be best aquifer where boreholes could be sited with aquifer thickness of 22.5 m, though the close proximity to the dump site call for further investigation. It was observed from the result that VES II (on the dumpsite) has a relatively low resistivity at the top of the soil profile, thus pollutants can emerge from the landfill top and migrate downwards to contaminate the water table. The results obtained indicate that the leachates from the dump sites have increased the conductivity of the soil, thereby lowering the resistivity. Considering the implications of this ground water source contamination and the health implications on the populace, recommendations were made.