Monitoring and modelling unsaturated and saturated flow to evaluate performance of slurry walls in Rho (Italy)

A former chemical district close to Milan (Italy) is still source of contamination by chlorinated solvents in aquifers that supply drinking water, though slurry walls were built in the eighties to prevent spreading. An unsaturated-saturated numerical model was performed to assess overall performance of this physical confinement, and to infer hydraulic properties and estimated geometry of the barriers and the aquitard at this specific scale. Water leaking from the source and recharge of the aquifer under different scenario simulation were assumed as global performance indicators. Results showed that incidental material buried in the shallower portion of the investigated aquifer (bricks, waste material) dramatically affect the natural recharge of the encapsulated area. The decrease of ratio between leakage from lateral barriers and leakage from the bottom interface to the aquitard, from early stages of wet conditions (when saturated front is higher) to drought stages, was also computed.