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Thickened Tailings Deposition for Closure

Nicholas Thompson and Pepe Moreno
Friday, June 16, 2017
First presented: 
20th International Seminar on Paste and Thickened Tailings, Beijing, China
Published paper
Mine Waste

The strategic implementation of a thickened tailings system for an existing conventional TSF can be beneficial in terms of significantly reducing the required post-operational earthworks and the time to achieve final closure.

One of the most challenging aspects of the successful closure of a TSF is the long-term water management of the tailings surface. A typical concave-shaped, conventional paddock TSF could be transitioned to have a convex, thickened tailings surface towards the end of operations through modifying the tailings disposal strategy to create a water-shedding final landform, limiting the amount of surface re-shaping and borrow material required. This would also maximise the tailings storage capacity while generating a facility profile that would be significantly more amenable to closure.

Challenges that would need to be explored and assessed before implementing such a strategy relate to the change from conventional to thickened tailings deposition and include characterising the slurry, adjusting the disposal methodology to include central discharge, assessing the impact of depositing thicker tailings over the existing beach, and modifying the supernatant water management plan.

This paper discusses the concept of ‘deposition for closure’ using thickened tailings that is currently relatively uncommon worldwide; however, is becoming increasingly attractive due to more stringent closure requirements and enhanced thickening technology. The implementation of this concept is currently in the early stages for a TSF at a gold mine in Ghana, with the knowledge gained from this project used as the basis for presenting the potential advantages of such a strategy, as well as the likely issues and challenges encountered.

Feature Author

Pepe Moreno

Juan Moreno has more than 25 years of diversified professional experience in projects mainly associated with geotechnical/ geoenvironmental engineering for the mining and civil industries throughout the world. Pepe is typically involved as team leader conducting conceptual to detailed engineering for mine waste facilities, including design of tailings disposal systems using a wide range of dewatering levels, waste rock dumps, and effluents containment. His experience covers from site investigation to closure design including advanced modelling for dam break analyses and water balance and geotechnical design for tailings facilities, heap leach pads, ponds and waste rock dumps. Pepe provides expert review for tailings and waste management for due diligence and peer review projects for banks and potential investors.

Principal Consultant (Mine Waste)
Civil Eng, MIEAust, CPEng, RPEQ
SRK Perth
Nick Thompson

Nick is a geotechnical consultant with over seven years’ experience specialising in tailings, waste rock management and heap leach facility engineering.  He typically is involved with numerous desktop designs and site-based roles, including geotechnical site investigations, greenfield site selection, design (scoping through to detailed), numerical modelling, cost estimation, risk assessment, construction supervision, auditing and closure.  Nick has experience on a diverse range of projects covering a variety of commodities in both tropical and arid climates around the world, for both Australian and overseas clients.  He works on projects involving a broad scope of tailings management including thickened, dry stack, cyclone and co-disposal.  Nick also prepares construction documentation, including tender documents and technical specifications.  His recent experience includes the design of a 200 m-high copper TSF in Papua New Guinea, and CQA supervision and technical support of TSF construction at nickel and iron ore mines in Western Australia, a uranium mine in Namibia and a gold mine in Brazil.

Consultant (Mine Waste)
BEng Hons (Civil), MIEAust
SRK Perth
SRK North America