Refinements to a dual mound central deposition tailings facility

Authors: Accadia, D; O'Kane, P Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_62

Cite As:
Accadia, D & O'Kane, P 2026, 'Refinements to a dual mound central deposition tailings facility', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-12, https://doi.org/10.36487/ACG_repo/2655_62



Abstract:
Tailings facilities for central deposition of thickened tailings are formed with a central point or a series of central points for slurry deposition. Best practice is to develop a predicted tailings beach slope model for design of the facility, with the model informing the embankment layout, and tailings distribution and surface water management systems. Where the upstream raise method is allowed, designing for the life-of-mine layout is critical for the success of this raise method and the future closure of the landform. Updates to the design tailings beach model should be expected throughout operation based on review of beach slope performance and these updates should inform refinements to the facility layout, both during stage operation and for future raise layouts. Perimeter embankment and internal refinements (e.g. for causeways) are typical throughout the life of the facility, to achieve the target storage capacity, accommodate changes to the beach profile and surface drainage, and the state of the tailings deposit. The tailings deposition system may be modified to provide greater distribution of tailings deposition; reducing the volumetric flow rate from each outlet typically improves beach slope performance, in turn increasing storage capacity. The distribution system may also be modified to maximise use of available freeboard at the perimeter embankment. Achieving the design beach geometry is critical for surface water management. A single decant area with appropriate water removal measures is favoured to limit dam failure risks associated with multiple, uncontrolled ponds. Adoption of a gravity decant system provides for passive release of water and pipe penetrations can be managed with controls to address failure modes associated with these penetrations. A passive system typically removes flood water faster than a pump-out system. An emergency spillway sized for an extreme rain event minimises the risk of overtopping. Based on observations made over circa 19 years since the transition to central deposition and multiple stages of development, this paper describes design refinements made to a dual mounded central deposition tailings facility in a semiarid climate that have improved operational performance, facilitated upstream raise construction, and established a runoff shedding landform that can be transitioned with limited works for longterm closure. It discusses how integration of tailings deposition and construction sequencing is critical to the success of the upstream raise method for central deposition facilities, and how the resultant landforms address best practice for geotechnical stability and surface water management during operation and at closure.

Keywords: thickened tailings, central deposition, beach slopes, upstream raise, surface water, closure

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