SUIT ABILITY ANALYSIS FOR SOLID WASTE LANDFILL IN A GEOSPATIAL TECHNOLOGICAL ENVIRONMENT FOR IBADAN METROPOLIS, OYO STATE, NIGERIA

Municipal solid waste landfill is an important part of the urban infrastructure that ensures the protection of environment and human health. Landfill selection problem for municipal solid waste involves many factors, criteria and regulations. The aim of this study is to access suitable site for an engineered solid waste landfill, ·with specific objectives of site determination based on UNEP criteria and carrying out both geophysical and geotechnical evaluation of the site. The study area is Ibadan metropolis. Geographical Information System (GIS) based methodology was applied in order to identifj; and select potential suitable sites. The initial step of the methodology comprises a GIS application and analysis that exclude all areas unsuitable for any waste disposal facility. Using the GIS spatial analytic model different constraint map layers were overlaid to obtain a potential suitability map. The output suitability map represents possible potential sites that are suitable for landfill sites. Geophysical and geotechnical survey were carried out on one of the site for the purpose of sub-surface characteristic of the site and the strength of the soil as a foundational material to be used for landfill design. Vertical Electrical Soundings (VES) with electrode spacing of J 00. OOm apart were executed to obtain subsuiface information on depth to bedrock and ground water table. The VES results indicate there are four geo-electric layers with depths of bedrock to basement rock to between 18. Om and 55. Om which represents potential ground water accumulation. Disturbed and undisturbed soil samples were collected at vertical interval of 0.5m up to a depth of 4. OOm. The soil samples were subjected to geotechnical parameter namely grain size distribution, consistency limit test, and permeability test. The soils possessed amount of fine materials (1 3.1 - 73. 0 %) and clay content (4. 3 - 38. 7 %) that are within the minimum 30 % and 10 % respectively considered adequate for a landfill site. Furthermore, they are well-graded exhibiting low to medium plasticity with plasticity index of 2. 9 to 20. 3 % and low leakage potential of 2. 7 x 10· 3 to 9. 26x 10- 3 cm/s within the depth of 4m. Permeability coefficient (k) rangedjrom 4. 7 X J o-B to J. 9 X 10- 6 cm/s and was within the range of 1 o-B to 10- 6 cm/s which fa/ls within the optimum permeability range for leachate retenti