Abstract

Geoelectric study of Abule Egba, Igando and Olushosun landfills within Lagos municipality has been undertaken to determine their hydrogeologic implications. The field technique involved vertical electrical soundings utilizing Schlumberger electrode array. At Abule Egba, landfill materials are defined by resistivity varying between 1.6 Ω-m at decomposed stage and 144 Ω-m within fresh dump. The Igando landfill is defined by resistivity varying between 2.5 Ω-m at decomposed stage and 26.1 Ω-m at fresh dump. Olushosun landfill is defined by resistivity varying between 2.4 Ω-m at decomposed stage and 51.5 Ω-m at fresh dump. Interpretation of sounding curves showed that Abule Egba is underlain by fairly thick column of clayey sand indicating an unconfined aquifer. Igando landfill is underlain by thick clay column indicating a confined aquifer. The northern flank of Olushosun landfill is overlain by thin refuse dump (4.4 m) while thick refuse dump (22.9 m) overlies the central area. The hydrogeologic system at Abule Egba is vulnerable to contamination. The impermeable geoelectric characteristics of materials underlying Igando landfill offer the hydrogeologic system some form of protection. At Olushosun landfill, materials of impermeable geoelectric characteristics in the northern flank offer hydrogeologic protection while fairly permeable materials in the south offer limited hydrogeologic protection.

Key words: Geoelectric, landfill, resistivity, contamination, hydrogeologic system, aquifer.