Practical demonstration of slow leakage from a tailings impoundment

Percolation from an unlined tailings impoundment in the Robinson District, east-central Nevada, was investigated by soil borings into the impoundment and adjacent background soils. The data obtained demonstrated the extent of water percolation and solute transport into the subsurface. After approximately 1 year of operation, water had percolated approximately 3 feet into the soil, and a solute front was detected at a depth of 2 feet. The depths of the wetting and solute fronts were incorporated into fate and transport modeling to determine potential impacts to groundwater of the solute transport from the impoundment. The field measurements of the wetting and solute fronts agreed well with the theoretical water balance derived for the impoundment and with known hydraulic properties of the background soil. Hence, the borings validated the fate and transport model’s prediction of the extent of solute transport through the vadose zone to the water table.