Resume/ Abstract
Abstract: The closure strategy for the Manitou mine tailings storage facility (TSF) utilizes repurposed tailings from the Goldex mine and Eldorado mine. The repurposed tailings from the Goldex site were used to increase the elevation of the phreatic surface within the TSF to provide geochemical stability of the potentially acid generating (PAG) Manitou tailings. Within a portion of the TSF where the PAG tailings will remain above the phreatic surface a barrier cover system will be constructed. The cover system design includes water retention layer (WRL) constructed of Eldorado tailings. The objective of the cover system is to limit oxygen ingress and sulfide oxidation by retaining a high degree of saturation within the WRL under conditions of atmospheric forcing. Tailings sourced from the Eldorado Mine have been characterized as having high fines contents (<0.074 mm) and suitable for constructing a WRL. Numerical simulations were completed to enhance our understanding of key processes and material characteristics that influence the performance of the cover system and inform on engineering decisions to advance the design and mitigate performance risks, including:
- Assessment of Eldorado tailings particle size distribution (PSD) and development of hydraulic properties including water retention curves (WRC) and hydraulic conductivity functions (k-functions) to support numerical simulations; and
- Evaluation of the performance of the cover system to optimize the design in terms of maintaining a high degree of saturation in the WRL using a soil-atmosphere-plant (SPA) numerical model and 42-year historic climate database.
The results of the simulations showed that cover design configurations of all cases (Eldorado tailings with fines contents ≥ 70%) provide satisfactory performance in terms of maintaining high degrees of saturation (> 85%) in the WRL. A state-of-the-art monitoring system was designed and will be installed to verify that success criteria for the cover system are met.
Keywords: water retention layer, metal leaching acid rock drainage, oxygen ingress, closure design, water retention curve, tailings repurposing