Pavements, foundations and underground constructions face many geotechnical problems related to wastewater diffusion seepage into underlying soils. The interaction processes between soil particles, pore liquids and chemical constitutive of wastewater are affecting geotechnical properties of underlying soil. The consolidation properties of wastewater-contaminated clayey soil was investigated and presented in this paper. A series of consolidation tests was carried out on natural contaminated soil samples at variant exposure period of wastewater and variant distances from contamination source. The results show harmful effects of wastewater on geotechnical properties of underlying clayey soil. Also, the underlying soil properties changed into undesirable properties.