This research was conducted with an aim of mapping the extent of subsoil and ground water contamination within the area. The contamination was as a result of an oil pipeline leakage that had gone undetected for some time and whose effects were evident on human and animal health, and crop yield. The leakage was more pronounced at possible recharge zones i.e. in thick sediments of volcanic origin (olivine basalts) and river sands to a depth of about 5m within the shallow aquifer as observed in the existing hand dug wells and trenches.
An integrated geophysical survey involving Geo-electrical Resistivity and Gravity Survey was conducted. In geo-electrical resistivity survey, Horizontal Electrical profiling, HEP and Vertical Electrical Sounding, VES were utilized. The resistivity lows from the HEP contour map were interpreted as shallow aquifer zones and hence likely contaminated while the VES curves showed the aquifer depth (13-25m).
With the Gravity method, 177 survey stations were established and the data obtained was utilized in generating a gravity contour map. Consistency was observed in both gravity and resistivity contour maps and a region of interest was identified at (391289E, 9723864S). It was discovered that in this region the oil product had percolated down to a depth of about 13 meters, extending to 100metres width approximately.
Keywords: resistivity, oil –pollution, Kenya pipeline, Hydrocarbons, gravity