Growing concerns around water scarcity, dam safety, and environmental performance are driving operators to consider large-scale dewatered tailings solutions. Industry evaluations often default to cost-focused comparisons, typically capital and operating cost of the process equipment, tailings transportation system, or material handling fleets. While these metrics are important, they tend to obscure other influential long-term drivers such as tailings storage facility (TSF) stability, water recovery potential, environmental risk, and operational reliability.
This article highlights the need for a holistic, systems-based approach that integrates technical, environmental, and operational drivers from the dewatering plant through to the TSF.
Moving Beyond Cost-Driven Decisions
Traditional business cases for tailings projects tend to be led by capital and operating cost comparisons. However, effective evaluations must also consider:
- Physical and chemical stability of the tailings landform
- Water recovery potential and reuse options
- Environmental and long-term sustainability impacts
This wider lens helps engineers and managers balance performance and cost while minimising long-term risk.
Designing from the TSF Backwards
An alternative proposal is to design tailings systems starting from the TSF rather than the dewatering plant.
Instead of targeting a specific solids concentration or moisture content at the outset, the process begins with defining the desired final landform geometry, including geotechnical and chemical stability requirements. These downstream requirements determine the tailings rheology and tailings moisture allowance, which in turn inform the selection and sizing of thickening, filtration, pumping, conveying, and stacking systems. This ‘backwards’ approach avoids over-specification with low filtered tailings cake moisture targets and ensures that the dewatering system produces tailings characteristics that are both technically sufficient and operationally practical at the commercial scale.
This ‘reverse-engineering’ method helps ensure that the chosen technology supports long-term stability, optimised material handling, and effective water recovery.
Water Savings as a Core Driver
Water scarcity remains one of the strongest motivators for pursuing dewatered tailings systems.
Copper operations typically consume 0.5–0.7 m³ of water per tonne of ore processed. In regions such as northern Chile, where desalinated water can cost up to ten times more than groundwater, efficient water recovery through slurry transport and filtration becomes critical.
By integrating filtered or partially filtered tailings into existing systems, operators can potentially achieve 25–37% reductions in water consumption, depending on the level of filtration and moisture content achieved.
Importantly, water recovery occurs both at the dewatering plant and within the TSF itself. Optimising this balance is critical to minimising capital and operating costs while maintaining system reliability.
Stability and Landform Performance
Beyond water efficiency, alternative dewatered tailings systems can deliver a more stable landform compared to conventional slurry facilities. Filtered and thickened tailings generally exhibit improved strength, reduced saturation, and lower risk of catastrophic failure.
Combining mechanical dewatering, controlled compaction, and evaporative drying can enhance both physical and chemical stability. These methods also minimise seepage, support concurrent rehabilitation, and limit the potential for acid rock drainage.
However, relying solely on evaporative drying can restrict stack heights, underscoring the need for engineered compaction and careful rate-of-rise control to manage transient pore pressures.
Integrated Stacking and Material Handling
The transition to large-scale dewatered tailings systems introduces new challenges for stacking and material transport. Examples show that effective design requires early collaboration among tailings engineers, materials handling specialists, and operations teams.
Key considerations include:
- Lift thickness and compaction requirements must be aligned with equipment capabilities and landform design.
- Reducing or removing trucks from the system in favour of conveyors or stackers can improve safety and lower operating costs.
- Staged implementation allows operators to manage learning curves and integrate technology improvements over time.
Innovative hybrid approaches, combining filtered and thickened tailings, or mechanical and hydraulic deposition, can often deliver the best balance between cost, performance, and operational risk.
Dewatering Process Efficiency and Yield Stress Control
For high-density thickened tailings, defining a target yield stress range rather than a single value can greatly improve design flexibility. In one case study, a range of 60–100 Pa allowed operators to balance water recovery, transport efficiency, and achievable beaching behaviour.
This approach emphasises the importance of open communication between dewatering plant designers and TSF engineers. A rigid moisture or solids target imposed in isolation can result in uneconomic designs, whereas a flexible performance window enables optimisation across the full system.
Building a Stronger Business Case
The holistic framework also incorporates multi-criteria decision analysis (MCDA) to evaluate technical performance, economic (such as water cost) and risk-based factors. This structured process supports transparent, defensible decisions that extend beyond simple cost comparison.
Interestingly, while the net present values (NPVs) of several dewatered tailings alternatives are often similar, the distribution of costs differ, for example, some options shift expenditure from operating costs to capital or vice versa. This reinforces the importance of considering long-term operational benefits, such as reduced water dependency and improved stability, when assessing the overall value of a solution.
In Summary
- Cost alone cannot determine the best tailings management option—multiple drivers must be balanced.
- Water cost and availability can significantly influence the economic viability of dewatered systems.
- Similar stability outcomes can be achieved through various technologies, provided rate-of-rise, density, and pore pressure are carefully managed.
- Reducing truck usage and improving integration between dewatering, transport, and stacking design offers both economic and safety advantages.
- A successful implementation depends on close collaboration between design, operations, and engineering teams throughout commissioning and early operation.
Towards the Mine of the Future
As the mining sector continues to navigate environmental, social, and regulatory challenges, the adoption of holistic tailings management represents a critical step forward.
By viewing the tailings system as an integrated whole—from water recovery and material handling to long-term landform stability—operators can achieve safer, more efficient, and sustainable outcomes.
Paterson & Cooke brings deep expertise in material dewatering and test result interpretation, enabling us to apply the most effective technologies and solutions to solve complex dewatering challenges.
Find out more about how we can solve your unique Tailings & Mine Waste challenges.
MPhil Met Engineering, B.Eng Mat
Rachel joined Paterson & Cooke in 2012 and is a senior process engineer and tailings manager for our North American practice, focusing on tailings dewatering and alternative tailings technologies. She is based in our Denver, Colorado office.
Rachel has extensive experience in mineral processing within various roles, including metallurgical engineering, consulting, and laboratory management. She has field experience in South Africa, Turkey, Indonesia, Mexico, Brazil, and Australia.