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Framework and methodology to evaluate post-deposition dewatering strategies at existing conventional surface tailings storage facilities to aid in achieving safe closure, A
Lammers, Heather N.
Lammers, Heather N.
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2023
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Abstract
A significant number of global tailings storage facilities (TSFs) are currently listed as in an active, inactive, and abandoned state. Many of these facilities pose an ongoing risk to human health and the environment due to their potential for failure. Recent failures have brought global attention to the mining industry’s tailings management practices and resulted in several initiatives to share knowledge and implement best practices. One area of interest that has broad influence on the risks associated with TSF failure is water management, particularly in reducing the amount of water or process fluid disposed with the tailings as a slurry.
The presence of process fluid within the tailings can prevent a TSF from achieving safe closure. Prior to deposition, tailings can be mechanically dewatered and subsequently placed in a facility that typically does not require a containment structure to retain the tailings. These dry stack facilities can be concurrently closed and reclaimed to conform with the surrounding environment. Conversely, a tailings slurry requires a containment structure to retain the tailings. Natural dewatering processes can occur after deposition of a tailings slurry, though the processes can be inefficient and lengthy, often extending in duration beyond the operating life of the facility. Advancements in post-deposition dewatering technologies have lagged the development and application of pre-deposition technologies. Process fluid can also remain entrained within the tailings slurry and will require additional measures to remove. Unfortunately, there is no single prescriptive post-deposition dewatering strategy that is widely applied with success to reduce the entrained process fluid at a greater rate than natural dewatering processes.
This research aims to present a framework for water management at a conventional surface TSF to achieve safe closure. The framework is intended to be used by practitioners to guide development of specific criteria for water management that must be met during closure of a TSF. The framework was developed using common themes identified through a comprehensive review of publicly available international guidance, standards, and regulations for TSF water management. A register of best industry practices for water management at a TSF was developed and included as an additional outcome of this research. This research also aims to present a methodology for identifying a preferred post-deposition dewatering strategy that can be applied to active, inactive, and abandoned conventional surface TSFs. The methodology is intended to be used by practitioners to guide the evaluation of available post-deposition dewatering strategies for application at a TSF. Available dewatering strategies were identified through a comprehensive review of publicly available documents describing post-deposition dewatering technologies and their successful application to reduce the amount of process fluid entrained in the tailings. Criteria to differentiate and evaluate the technologies were established using characteristics unique to each technology and form the basis for development of the methodology.
A case study TSF was used to demonstrate an application of the framework for water management and confirm alignment with current practices employed at the case study TSF. Reducing the amount of water and process fluid at the TSF was identified as a key consideration for the framework to achieve safe closure of the facility. While the literature review demonstrated that post-deposition tailings dewatering strategies have the potential to reduce the amount of process fluid entrained in the tailings, this research identified a need for additional applied field trials and advancement of post-deposition tailings dewatering technologies. The case study TSF was also used to demonstrate an application of the methodology to evaluate and identify a preferred post-deposition tailings dewatering strategy. Criteria were developed specific to the available dewatering technologies and the case study TSF, and the evaluation resulted in the identification of a preferred strategy to consider for implementation at the case study TSF.
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