Geotechnical and Hydraulic Characterization of Soils Underlying Municipal Solid Waste Dumpsites: A Case Study of Maduganari Dumpsite, North-Eastern Nigeria

Abstract

Municipal solid waste dumpsites remain major sources of environmental degradation and groundwater contamination in rapidly urbanizing regions of developing countries. This study investigated the geotechnical and hydraulic properties of soils underlying the Maduganari municipal solid waste dumpsite located behind the Sanda Kyarimi Zoo Park in Maiduguri, Northeastern Nigeria. The study aimed at evaluating the engineering behavior of the underlying soil formation and assessing its implications for contaminant migration, groundwater vulnerability, and environmental sustainability.
Field sampling and laboratory investigations were conducted on representative soil samples collected from different depths within the dumpsite using auger boring techniques. Laboratory analyses included determination of moisture content, specific gravity, bulk density, dry density, particle size distribution, Atterberg limits, porosity, void ratio, and hydraulic conductivity using standard geotechnical testing procedures. Results obtained from the investigation revealed that the underlying soil profile is predominantly composed of silty and fine sandy materials with approximately 95% of the soil particles passing through the 0.075 mm sieve size. Moisture content values ranged between 18.4% and 32.6%, indicating moderate water retention characteristics associated with the fine-grained nature of the soil. Specific gravity values ranged from 2.58 to 2.69, while dry density values varied between 1.32 g/cm3 and 1.61 g/cm3.
The hydraulic conductivity values generally ranged between 2.1 × 10^-5 cm/s and 7.4 × 10^-4 cm/s, indicating low to moderate permeability characteristics and relatively slow infiltration behavior within the subsurface environment. The Atterberg limits analysis revealed moderate plasticity behavior with plasticity index values ranging between 12% and 21%, suggesting the presence of cohesive fine fractions capable of partially retarding contaminant migration. Porosity values ranging from 36% to 49% further demonstrated moderate pore distribution and attenuation capacity within the soil system.
The results indicate that although the underlying soil formation exhibits some resistance against rapid contaminant transport due to its fine-grained texture and relatively low permeability, prolonged accumulation of municipal solid waste and sustained leachate generation may eventually compromise the protective capacity of the soil profile and result in groundwater contamination. The study therefore emphasizes the urgent need for engineered landfill systems, effective leachate management strategies, periodic groundwater monitoring, and improved environmental protection policies within rapidly growing urban centers in sub-Saharan Africa.

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