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The presence of Petroleum Hydrocarbons (PHCs) in hand-dug wells has become a concern to the residents of Ayetoro area, Osogbo. Consequently, the detection of PHCs was evaluated using, nine Vertical Electrical Soundings (VES) and 2D electrical resistivity tomography surveys. Soil samples collected were analyzed for porosity and permeability. Hand-dug well water samples were screened for PHCs. VES revealed that second layer had high apparent resistivity of 14415.0 Ωm, indicating presence of PHCs that had penetrated to maximum depth of 19.1 m. The highest resistivity of the control points was 48.0 Ωm, indicating absence of PHCs. The 2D resistivity revealed highest value of 3622 Ωm and had migrated to a depth of 10.0 m. The porosity (0.40) and permeability (6.87516 x 10–4 cm/s) were typical of silty clay which allowed passage of PHCs. Hydro-chemical analysis indicated presence of PHCs (0.50–11.00 mg/L). The study has established presence of PHCs in soils and hand-dug wells. Keywords: Petroleum Hydrocarbons, Soil, Groundwater, Electrical resistivity tomography

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Keywords:Leachate migration, Mathematical Model, Maximum Horizontal distance travelled by leachate This study was designed to determine Maximum Horizontal Distance (X MHD ) travelled by landfill leachate. Twenty -nine Schlumberger Vertical Electrical Soundings (VES) were conducted at 10.0m intervals away from four sides A, B, C and D of Lapite dumpsite. One VES point conducted outside the vicinity of the dumpsite served as a control. VES data were processed. Lowest resistivity values (Y) of VES points and the control point (Y c ) were extracted. Curves of Y against X fitted best to yield an equation. X MHD was determined from the generated equation when Y = Y c . The determined (X MHD ) on the four sides ranged from78.95m to 179.86m.

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