This research work assessed the influence contaminated groundwater chemistry
(especially nitrate contamination) on the volume change behavior during consolidation for
a southwestern Nigerian clayey soil. 1-D Consolidation tests using deionized water and
various concentrations of nitrate solution as the saturation/inundation liquid were
performed on undisturbed clayey soil samples collected from Odi- Olowo Street (nitrate
contamination prone area) in Akure, the capital of Ondo state, Nigeria. The
compressibility/swell characteristics of the soil are influenced by nitrate contamination, as
shown by the variation in the values of the coefficient of permeability, coefficient of
consolidation, compression and swell indices (k, cv, Cc and Cs). This implies that the swell
potential, magnitude and rate of settlement are affected. These properties directly influence
the performance of shallow structural foundations. It was concluded that lack of chemical
analysis for soil and groundwater in a nitrate contamination prone area before construction
could lead to an overestimation of the swell and compressibility indices for the site.
Permeability of the clayey soil increased significantly with increase in nitrate
contamination, this portends the danger of emerging breakthrough of contaminants in the
shallow contaminated zone through the underlying clayey layer to deeper confined aquifers
being relied upon for portable drinking water
