Municipal solid waste landfill site selection: a geotechnical and geoenvironmental-based geospatial approach

This research is aimed at determining suitable areas within Akure metropolis with residual soils of excellent geotechnical properties as landfill liners and with considerable depth to groundwater table, along with other environmental factors, for siting municipal solid waste dumpsite. Field work, soil sampling, and laboratory geotechnical tests were carried out based on standards outlined in British Standards, BS 1377. The suitability of geotechnical parameters was evaluated using existing standards described in previous research works. The geotechnical conditions, along with lithologic, hydrologic, topographic, and land-use conditions, of the study area were allotted weightages, and respective maps were produced using fuzzy membership approach. The coefficient of permeability, plasticity index, fines percentage, and maximum dry density (MDD) values ranged from 2.66 × 10^–9 to 3.99 × 10^–3, 0 to 34.9%, 4.3 to 78.8%, and 1432  to 2113 kg/m³ respectively. Based upon the evaluation of the derived geotechnical parameters, about 307 km² of the study area (over 90% of the soils sampled) is highly suitable for landfill consideration. Based on the sites’ lithological conditions, the charnockite-derived soils are most suitable for landfill consideration. The land-use/land-cover criteria indicated that areas covered with dense vegetation, cropland, grassland, and/or derived savanna cover an area of about 188 km² and are rated most suitable for landfill. Based on topography, distance to drainage, and depth to groundwater table criteria, an average of about 78 km² of the land mass of Akure is rated averagely to very suitable. Based on the overlay of all the fuzzy members used as criteria, of the total land area of about 335 km² which Akure metropolis occupies, an area of 31.7 km² (9.5%) is most suitable and 133.73 km² (39.9%) is averagely suitable, while 169.73 km² (50.6%) is considered not suitable for siting solid waste landfill. This study ascertained that the integration of geotechnical, lithological, hydrological, and topographical factors, as well as land-use criteria, are important in the selection of appropriate municipal solid waste landfill sites with minimal environmental contamination potential or threat. It further proves that GIS is a genuine tool for making decisions regarding the planning, designing, and development of urban areas.