Sustainable reuse of mine tailings and waste rock as water-balance covers

Abstract

The focus of this study was to evaluate the potential reuse of mixed mine tailings and waste rock in water-balance covers (WBCs). Reuse of mine waste in geoengineering applications can provide an economic advantage via offsetting raw material requirements and reducing waste volumes to manage. Water-balance covers are designed to minimize percolation and/or oxygen ingress into underlying waste via moisture retention while also providing resistance against slope failure and erosion of cover materials. Water-balance simulations were conducted using a variably-saturated one-dimensional numerical model to assess hydrologic behavior of an actual WBC as well as hypothetical mixed mine waste WBCs. The actual water balance cover included a 1.22-m-thick silty-sand storage layer and a 0.15-m-thick topsoil layer. Three scenarios were evaluated via hydrologic modeling that focused on replacing the actual storage layer with a layer of mine waste: (1) storage layers were simulated as 1.22-m-thick layers of pure mine tailings (i.e., copper, gold, coal, and oil sand tailings); (2) storage layers were simulated as 1.22-m-thick layers of mixed mine tailings and waste rock; and (3) mixed mine tailings and waste rock storage layer thicknesses were redesigned to yield comparable percolation rates as the actual cover.