Abstract
Deconstruction of a Tailings Storage Facility (TSF) is often evaluated by mine owners as an alternative in their risk management strategy for dams that do not meet international standards. However, the limited experience in these construction projects, large material uncertainties and potential risks associated with the deconstruction of soft tailings and upstream raises make this a less appealing choice. The TSF presented in this paper was partially raised upstream and was assessed as very high risk. Due to its location next to a creek and short distance to the downstream community the preferred mitigation strategy was to proceed with the TSF deconstruction.
This paper presents the project design and execution for deconstruction of the TSF involving the removal and relocation of approximately 145,000 m3 of tailings. This case study provides a real example of staged deconstruction planning and implementation, and monitoring and surveillance to manage potential risks and unknowns. The project design phase included building a “digital twin” of the TSF for planning and technical evaluation. The absence of as-built drawings and construction records prompted the creation of this model using data from field investigations. This model facilitated the recreation of the dam geometry, identification of deconstruction risks, safe staged deconstruction methodology, planning of a monitoring system, and a final configuration that is stable and adaptable for future excavation or closure. During the deconstruction process, site engineers continuously monitored the dam performance and worked collaboratively with the client and contractor to adapt the deconstruction methods to safely remove the tailings as conditions changed with depth. Challenges and adaptations during the deconstruction process are also discussed, including the accuracy of predictions in terms of shape, monitoring results, equipment types, and material relocation rates.
