A Screening Level Model for Estimation of Vadose Zone Leaching and Saturated Zone Mixing: VLEACHSM

A screening level computer model has been developed for the evaluation of pollutant migration through the vadose zone and subsequent mixing within the saturated zone. The model, called VLEACHSM, consists of a one-dimensional finite difference scheme for solving the vadose zone leaching and a mass-balance technique for calculating mixing in the aquifer. The vadose zone module of VLEACHSM simulates the transport precess including liquid-phase advection, liquid- and vapor-phase dispersion, linear sorption, and decay of contaminants. The saturated zone module estimates the concentration of contaminants following the mixing of leachate from the vadose zone with ground water. The leachate penetration in the aquifer is estimated using a relationship between the vertical infiltration velocity, size of the source in the soil column, dispersivity, ground-water velocity, and the aquifer thickness.