Reactive Transport Modeling of AMD Release and Attenuation at the Fault Lake Tailings Area, Falconbridge, Ontario

Abstract

Numerical simulations of the Fault Lake Tailings were conducted to assess the long-term impact of AMD-generation on downgradient receptors. The effects of impoundment geometry, contrasting permeability, water content, and mineralogy of tailings and native sediments were considered. Simulation results suggest that over a time period of 1,000 years only the top three meters of tailings become oxidized and that AMD is preferentially released at the periphery of the impoundment. Although the permeability of the tailings is lower than that of the aquifer and groundwater flow is deflected around the deep saturated tailings mass, AMD is not inhibited from percolating into the aquifer, because the bulk of the tailings are located within the vadose zone. The carbonate content of the underlying material likely provides sufficient buffering capacity to attenuate most metals and neutralize pH over the long-term.