Cash, A & Paszkowski, D 2024, 'Design constraints of a closure design basis and cover options assessment for a gold mine tailings facility in the Canadian Shield', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2024: Proceedings of the 17th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 861-872, https://doi.org/10.36487/ACG_repo/2415_61
(https://papers.acg.uwa.edu.au/p/2415_61_Cash/)
Abstract: A design basis was developed to guide closure design decisions for a tailings facility at an operating underground gold mine in the Canadian Shield of Ontario, Canada. An interdisciplinary design team made up of subject matter experts in geotechnical engineering, groundwater and surface water hydrology, geochemistry and ecology collaborated with site personnel through a series of workshops to develop the design basis, which was subsequently used to inform a structured screening-level options assessment for alternate closure cover scenarios. Various end land uses were considered in developing the design basis, which resulted in 19 site-specific closure goals organised within six overarching focus areas: 1) geotechnical performance; 2) geochemical performance; 3) surface water; 4) groundwater; 5) land use and ecology; and 6) earthworks, landform design and active care. Design constraints identified in the design basis included a limited appetite for disturbing new areas for borrow material, a preference for a dry landform, and the desire to limit net percolation in a humid continental climate, lower groundwater levels in the tailings and curtail degradation of groundwater quality. Regulatory guidelines, the expectations of local communities and First Nations people, economic feasibility and land capability were also recognised as potential constraints. A range of conceptual cover designs were developed within the identified constraints, incorporating modelling of projected post-closure ecosystems. A qualitative options assessment framework was used to provide relative rating of the cover options based on their technical merits in relation to the design goals set out in the closure design basis. The screening-level options assessment highlighted the need for the closure design to balance the potentially competing demands of a low-permeability cover system with the desire to minimise land disturbance and use of borrow materials.

Keywords: tailings management area, closure goals, end land use, cover systems, options assessment, boreal ecosystem, Ontario