Assessment of groundwater below a contaminated soil landfill including modeling of vadose zone

This study aims at assessing the groundwater contamination underneath a waste yard that receives oily contaminated soil (CS). According to the collected samples from the study area, the groundwater underneath the CS site is brackish water (salinity > 40 mS/cm and TDS > 24,000 mg/L) with relatively neutral pH (7 to 7.4). Samples taken from upstream and downstream wells show high hardness (~6,000 mg/L as CaCO3), relatively low alkalinity (50 mg/L - 80 mg/L as CaCO3), and high sulphate content (>2,700 mg/L). The results did not show any heavy metal content. Furthermore, the amount of the different types of hydrocarbons in the groundwater samples were below detection limits of 0.01 mg/L. The infiltration of water and solute (dissolved hydrocarbons) transport have been evaluated through a one dimensional model. The computations were done using in-situ values of percolation rates and laboratory measured permeability values of compacted soils. The concentration of solute (dissolved hydrocarbons) was computed for a period of two years over a depth of 2 m below ground. The highest percolation rate observed at the dumping site was computed to be approximately 0.0007 mg/cm³ (i.e. 0.00007%). Therefore, the chances of the oil contamination reaching the water table are remote.