Sulfide oxidation in pit-backfilled, waste-rock facilities

A conceptual model was developed to quantitatively estimate the amount of sulfate produced by sulfide oxidation in a pit-backfilled, waste-rock facility prior to groundwater flooding. The model includes three sulfate production mechanisms: 1) consumption of the initial pore-space oxygen, 2) oxygen diffusion at active construction faces, and 3) oxygen diffusion at inactive faces after backfilling is complete. Sulfate from each mechanism is calculated and summed, giving an average sulfate concentration for the waste-rock facility, which then can be used with kinetic testing data to estimate the mass of other constituents. This paper presents the conceptual model and gives an example of its application at a mine site. In addition, facility construction practices that can minimize the oxidation occurring during the active life of the waste-rock facility prior to groundwater flooding are presented.