The dam will be constructed within an existing valley, abutting natural high topography and against an existing out-of-ground tailings facility. The tailings will be stored, initially by filling below grade in the existing mine pit and then above grade contained by the dam, which will be designed to form part of the closure landscape. The dam will be constructed with hydraulically placed and compacted tailings sand using the centerline construction technique. The dam will be founded on Pleistocene fluvial sands and glacial tills overlying the Upper McMurray Formation.
The design includes the geotechnical design of an above ground tailings dam with associated infrastructure and the design of surface water and seepage management systems. The geotechnical design establishes the upstream and downstream slopes based on the foundation conditions and also considers the closure requirements for the structure.
The surface water management system design includes the design of Process Affected Water (PAW) and Clean Water ditches. The dam will bury an existing watercourse, and therefore, a pipeline is being designed to withstand up to 27 m of dam fill loading together with an associated outlet structure. A fish and riparian habitat assessment for the existing watercourse has already been carried out.
The seepage water management system includes an internal drainage system and a cut-off wall which extends along the boundary of the project site. The design of the cut-off wall was based on a 3D hydrogeological model which was used to simulate flows of clean and PAW water in the vicinity of the tailings dam.
The infrastructure required to construct and operate the dam includes an access road designed for heavy hauler traffic, heavy hauler and light duty vehicle access ramps on the tailings dam and a sand borrow pit.
- Site investigations
- Fish and riparian habitat assessment
- Tailings dam design
- Surface water management design
- Borrow pit characterization
- Hydrogeological modelling
- Seepage management design
- Cut-off wall design
- Regulatory support
Sustainable Project Attributes
- Design of centreline dam to minimise footprint and fill volumes;
- Optimisation of starter dyke design to maximise use of local materials and reduce haul distances;
- Re-use of tailings line pipe for a temporary culvert crossing for an existing power line beneath an existing haul road to facilitate construction of the new access road and cut-off wall;
- Re-use of the existing haul road gravels elsewhere in the mine;
- Leaving the muskeg in-place beneath the access road which saves on fuel since no stripping efforts are required; and
- Re-use of existing reclamation material when tying into adjacent existing out-of-group tailings facility.