Modeling the water flow in unsaturated waste rock pile: an important step in the overall closure planning of the first uranium mining site in Brazil

Release of acid drainage from mining-waste disposal areas is a problem found in many mine sites all around the world. An understanding of waster flow and the geochemical processes within mining-waste is important to the long-term prediction of contaminant loading to the environment. This is the first of two papers and describes the water flow in one of the waste rock piles of the first uranium-mining site in Brazil by the use of the numerical model HYDRUS-2D. The obtained results indicated that a steady state condition is achieved after 500 days of simulation. The average flow inside the pile was about 0.4 cm/d. The outflow estimated by the model was in good agreement with the measured values. However, it must be emphasized that result only improved when the flux through the macropores was taken into account.