Laboratory and Numerical Study of the Hydraulic Barriers on ContaminantTransport

In this study, contaminant transport from surface pollutant source to groundwater source through a hydraulic system consisting of three layers of soil is considered by using laboratory models and a numerical model. Three soil layers included two fine-grained layers and one coarse-grained layer between them. Arrangement from top to bottom consisted of a contamination tank containing sodium chloride solution as a source of contaminant, a clay layer with a physical barrier, a sand layer with a hydraulic barrier and a bottom placed clay layer as natural land and ultimately a fresh water tank as the groundwater source, receiving contamination. To study the performance of the hydraulic barrier, the physical and hydraulic properties of the used materials were calibrated in the CTRAN / W model. Then the calibrated model was validated using observational data with the extra conducted testes. Finally, hydraulic barrier performance at different hydraulic gradients and pressures was evaluated by numerical model. The results showed that the performance of hydraulic barrier is in the best condition when there is no gradient in the upper clay layer. Comparison revealed the hydraulic barrier efficiency is almost seventy percent better than the regular compacted liners without a hydraulic barrier. The studies also showed that the transmission of contamination to the receiving reservoir under positive gradient (downstream flow in the clay layer) was more in comparison to the negative gradient (upstream flow in the clay layer).