Harrington, J, Cash, A, Mendoza, C, Straker, J, Iverson, M, Raizman, V & Leclair, M 2025, 'Five-year performance review of a mine rock stockpile cover trial in the Canadian Shield', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2515_98
(https://papers.acg.uwa.edu.au/p/2515_98_Cash/)
Abstract: Progressive reclamation during mine operations allows for the development and refinement of techniques over time. At the Detour Lake Mine in Canada (50°N, 80°W), the planned end land use for mine rock stockpiles is dense mature coniferous forest to re-establish pre-mine ecosystems. The site-specific reclamation design elements that would lead to better reclamation outcomes were initially unknown, so a 10-hectare cover trial was constructed to assess the relative performance of different cover and revegetation prescriptions toward achieving the planned end land use. The trial was divided into plots considering a range of slope angle, aspect, cover thickness, surface grading and revegetation prescriptions. 
This paper presents a review of the cover trial performance after five years of monitoring. Large-scale slope instabilities have not been observed in the silt-rich reclamation cover. Most erosional and depositional features are interpreted to have stabilised three to four years following construction. The primary factors influencing erosion are variability in surface water run-on from the upstream bench and surface grading on slopes, with lesser influence from slope angle and cover thickness. Erosion performance is improved by limiting surface water run-on to slopes by using a microtopography surface grading of offset hummocks and hollows plus rapidly establishing vegetation. The density of conifers is within the range required to achieve the planned end land use, although it is nearing the lower end of that range, with some ongoing mortality. Green alders are growing well and reaching heights greater than 2 m. The presence of peat was the key driver of seedling survival and vigour, where survival was approximately 25% higher in areas with increased peat. A 0.7 m cover thickness was suitable for promoting vegetation growth and managing erosion. Insights into operationalscale construction methods and the relative performance of cover characteristics are being applied to ongoing progressive reclamation activities.

Keywords: soil cover, peat, erosion, deposition, seedling survival, seedling vigour, run-on