Environmental Risk Assessment of Domestic Waste Leachate on Lateritic Soil Permeability and Subsurface Quality in Auchi Metropolis

Domestic waste leachate infiltration has become a growing environmental and geotechnical concern in rapidly urbanizing regions such as Auchi Metropolis. This study investigates the influence of domestic waste leachate on the geotechnical behavior of lateritic soils collected from Aviele, Jattu, and Uchi. Standard BS 1377 and ASTM laboratory procedures were used to evaluate soil index properties, compaction characteristics, permeability, and swell potential, alongside chemical and microbial characterization of the leachate. The soils were predominantly sandy (76–84%) and classified as A-2–4 to A-3 (AASHTO) and SP (USCS). Compaction tests showed similar optimum moisture contents of 14.36–14.40%, with maximum dry densities ranging from 1.65 g/cm 3 for Aviele and Jattu to 1.85 g/cm 3 for Uchi, indicating stronger load-bearing capacity at Uchi. Permeability coefficients ranged from 1.01 × 10 -7 m/s (Jattu) to 3.51 × 10 -7 m/s (Uchi), demonstrating low but variable hydraulic conductivity, while swell tests revealed minimal expansion, with Aviele recording 2.4% and both Jattu and Uchi showing 0%. Leachate analysis indicated acidic conditions and high organic and microbial loads, suggesting potential for chemical alteration and biological degradation of soil structure. Overall, results show that leachate exposure increases permeability, alters consistency limits, and may reduce long-term soil stability. The study emphasizes the need for improved waste management, engineered containment, and geotechnical monitoring to mitigate leachate-related environmental and structural risks in Auchi Metropolis.