When a solution reduces a risk as big as a tailings dam collapsing, it can be tempting to see it as a silver bullet, a seemingly simple answer to a complex issue. But on their own, technical fixes are rarely that straightforward. New technologies need people to unlock their full potential.
Filtered tailings emerged as a promising alternative to conventional tailings dams after catastrophic mining disasters in Brazil and South Africa – prompting a global reassessment of tailings management. Regulatory authorities and industry bodies introduced new standards like the Global Industry Standard on Tailings Management (GISTM) and the Consequence Classification System (CCS) – placing greater emphasis on risk reduction, accountability and transparency.
Instead of storing mine waste as liquid slurry, filtered tailings remove most of the water, so the soil-like material is dry enough to be transported and stacked in compacted layers on land. They can significantly lower the risk of devastating water flows and mudslides, protecting lives and long-term damage to livelihoods. But as a relatively new technology, filtered tailings come with their own unique challenges and opportunities.
While working on a filtered tailings project in South Africa, WSP tailings engineers Kiasha Naidoo and Veshania Balakistan saw an opportunity to help build industry knowledge around this developing solution.
“Our work is about responsibly managing mine waste so that operations can co-exist safely with people and the environment” explains Kiasha. Filtered tailings come with many advantages, but like any tailings management approach, they need to be carefully designed, operated and monitored to mitigate risk and enhance performance over time.”
So, Kiasha and Veshania built a targeted testing program to better understand filtered tailings in action – including how dry and compact layers need to be, how they can safely support construction traffic, how stacks settle and change over time, and how strong material is once placed.
Water management is key to performance
Unlike slurry facilities, where water management is integral to the design, controlling water content in filtered tailings can be a challenge. Too dry and material can be too hard to compact and generate excessive dust. Too wet and it can become unstable, difficult to transport, and flow like a liquid.
Without additional water management, filtered tailings can also be susceptible to rainfall – as unlike wet tailings storage facilities – they aren’t designed to retain water and have a minimal buffer for spill prevention. Even shallow dips in dry stacks can lead to ponding, infiltration and instability, softening compacted layers and raising internal water pressure.
“One surprise was just how sensitive filtered tailings are to small changes, especially when it comes to moisture content, says Veshania. “Our tests showed that slight increases in moisture content could reduce material strength by up to 20% in some test conditions. Another important learning curve is how moisture is defined and understood across engineering disciplines. If metallurgical and geotechnical definitions don’t align, it can have a potential knock-on effect from design through to operation.”
Their lab testing also showed the importance of compaction quality, and that atmospheric drying can work when thin layers are stacked slowly, enabling each one to drain and dry properly.
Kiasha and Veshania explored several industry case studies as part of their research. One showed that high internal water content and excessive height caused filtered tailings to flow rather than slump1, while another highlighted how increasing moisture content led to ponding, groundwater impacts and stability concerns2. Rigorous geotechnical assessment is vital too, with a dry ash disposal facility having to be redesigned and relocated after unknowingly being placed on clayey foundation soils3.
“Exploring how filtered tailings behave in practice will deepen the industry’s collective understanding of this emerging technology” says Kiasha. We need more research as well as adoption to optimize how facilities are designed, operated and monitored in different conditions.”
Climate change will shape future designs
The Global Industry Standard on Tailings Management (GISTM) calls for climate change to be considered at the design stage and Veshania believes it will increasingly shape how facilities of all kinds are designed, operated and monitored in dry and arid conditions. “Filtered tailings can go either way. Both heavier, more frequent rainfall and hotter, drier conditions can impact water management, while wind can increase the risk of dust, which will need to be controlled.”
Veshania continues: “Filtered tailings use a lot less water than slurry facilities, so they have a vital role to play in water conservation. They can also reduce the risk of groundwater seepage and contamination impacting local water sources. Beyond water use, there are more nuanced trade-offs to weigh up including the environmental footprint of deposition equipment. Slurry uses pumping and pipelines. Filtered tailings rely on trucking and conveyor systems.”
Where next?
Kiasha and Veshania are using their findings to answer vital questions about filtered tailings earlier in the project lifecycle – including their compactability, trafficability and transportability. Kiasha explains: “Now we know what tests matter, what parameters to focus on, and what results to look out for depending on how facilities are placed and handled. The most important thing is to design with variability in mind – so facilities can adapt as conditions change.”
Veshania concludes: “Ultimately, the choice between filtered and conventional tailings storage should be site-specific, informed by climate, material behaviour, water availability, operational capability and risk tolerance. No tailings solution is inherently safe – greater safety and sustainability can be achieved through careful planning, design, operation and monitoring.”
Read the research, originally presented at The Southern African Institute of Mining and Metallurgy (SAIMM) Tailings Conference 2026, to find out more.
- SSR Mining (2025) 'SSR review of Çöpler mine incident points to third-party design flaw'. Available at https://www.mining.com/ssr-review-of-copler-mine-incident-points-to-third-party-design-flaw/ (Accessed: 19 February 2025).
Eos (2024) 'The 13 February 2024 landslide at the Çöpler Mine in Turkey'. Available at: https://eos.org/thelandslideblog/copler-mine-1 (Accessed: 19 February 2025).
- Copeland, A., Daigle, V., & Strauss, A. (2023). Is Implementation of Dry Stacking for Tailings Storage Facilities Increasing? A Southern African Perspective. Paste 2023, 611-619. Available at: https://papers.acg.uwa.edu.au/p/2355_46_Copeland/
- Internal project, no published references.
