Innovative approaches to tailings dam rehabilitation: The importance of addressing environmental and structural risks
Ahmad Zarei, Senior Geotechnical Engineer, Cartledge Mining and Geotechnics
Tailings dam rehabilitation is a complex task requiring both technical expertise and innovative solutions. These large structures, holding millions of cubic metres of mining waste, present significant environmental and societal risks if not managed properly. Here, Senior Geotechnical Engineer, Ahmad Zarei delves into the evolving methods used to safely rehabilitate tailings dams, exploring cutting-edge approaches that balance environmental responsibility with long-term structural stability.
Tailings dams are critical for managing mining byproducts, but their scale and the risks they pose to communities and ecosystems are undeniable.
These vast structures, essential for storing waste minerals and runoffs of mining and excavations, often stretch across square kilometres and hold millions of cubic meters of waste. Yet, the potential risks they pose to the environment and nearby communities cannot be overstated. Inadequate design, earth movements, unusual weather conditions, or lapses in operational standards can lead to catastrophic failures. Past incidents have underscored the pressing need for modernised rehabilitation techniques that can mitigate these dangers while ensuring long-term environmental health.
Through Cartledge Mining and Geotechnics’ extensive global experience, we’ve seen firsthand how tailings dams can become a major environmental concern if not properly managed. The complexity of rehabilitating these structures lies in balancing the environmental factors, the sheer volume of tailings, and the dam's structural stability. This article explores the latest approaches to safely rehabilitate tailings dams and address the associated environmental challenges. As the mining industry evolves, so too must our strategies for managing the legacy of these structures, transforming them into assets for both people and nature.
The 400-metre failure section of the Newcrest Cadia tailings dam body, close view (top), far view (bottom).
Advancing rehabilitation methods
Recent developments in tailings dam rehabilitation have introduced a variety of innovative methods, each offering unique advantages and challenges.
One such method is dry stacking, which removes the water from tailings to produce a dry, stackable material. By significantly reducing water content, it reduces risk of dam failure and makes the tailings more resistant to seismic activity. Additionally, dry stacking enables continuous rehabilitation alongside ongoing mining operations. However, this method is not without its drawbacks—initial costs are high due to the need for specialised infrastructure and equipment, and it requires large land areas, which may not always be available. Its effectiveness can also be hindered by adverse climate conditions, particularly in regions prone to heavy rainfall.
Another technique, capping and covering, places a protective layer of inert material—such as soil or clay—over the tailings to prevent water and oxygen infiltration, which could lead to contaminant leaching. This method encourages vegetation growth, stabilising the tailings and reducing erosion. Synthetic liners, like geomembranes, are sometimes incorporated to enhance impermeability. Despite its versatility across various site conditions, capping requires regular maintenance to ensure long-term effectiveness. The cost of advanced materials can be high, particularly for larger sites, and the method is not always suitable for all types of tailings or climates.
In-situ stabilisation and solidification strengthen the mechanical properties of the dam by mixing tailings with materials such as lime, cement, or fly ash, preventing contaminants from leaching into the environment. This method is often more cost-effective than relocating tailings, but its success depends on the compatibility between the stabilising agents and the specific tailings materials. Long-term monitoring and careful selection of stabilising compounds are crucial, as improper use could introduce new environmental hazards.
Phytoremediation takes a more natural approach by using specific plants to absorb heavy metals and stabilise contaminated areas. This eco-friendly solution promotes biodiversity and is cost-effective compared to other methods. However, its success may take years or even decades, and the choice of plant species requires careful consideration, as not all are capable of absorbing harmful contaminants.
Similarly, bioremediation uses microorganisms to neutralise harmful elements in tailings. While particularly effective for organic contaminants and certain heavy metals, its efficacy can be influenced by external factors such as temperature, pH, and nutrient availability. The use of genetically modified organisms (GMOs) in this method also raises public and regulatory concerns.
The reprocessing of tailings is another method gaining traction, which involves returning tailings to processing plants to extract valuable minerals, reducing the overall tailings volume while generating revenue. This approach is becoming more economically viable due to technological advancements, but its success hinges on the value of the extracted minerals and market conditions. The process is demanding on resources and complex, requiring advanced technologies and expertise. The leftover material also requires secure management or disposal, posing a continued challenge.
Constructed wetlands, which leverage natural processes to treat contaminated water, offer a low-cost solution that enhances biodiversity. They are effective in reducing pollution and provide wildlife habitats. However, they require careful design tailored to specific environmental conditions and need time to become fully operational.
Lastly, geotechnical engineering plays a critical role in ensuring the stability of rehabilitated tailings dams. Techniques such as slope stabilisation, reinforcement, and improved drainage systems are vital to preventing future failures. Advances in geosynthetics—such as geotextiles and geogrids—have further enhanced these methods by improving soil stability and the structural integrity of dams.
Each of these methods represents a step forward in addressing the environmental and structural challenges posed by tailings dams, but their success depends on careful planning, ongoing monitoring, and adapting solutions to site-specific conditions.
Case Studies and Success Stories
Rum Jungle Mine, Australia: Located in the Northern Territory, Rum Jungle is a former uranium mine that was abandoned in the 1970s due to severe contamination in the eastern branch of the Finniss River. Since then, several rehabilitation initiatives have been implemented, including sealing, bioremediation, and the creation of constructed wetlands. These efforts aim to mitigate contamination risks and restore the ecosystem. Currently, the project is in its third phase, which commenced in early 2022.
Mount Polley Mine, Canada: The catastrophic failure of the Mount Polley tailings dam in August 2014 prompted an emergency rehabilitation plan. The plan incorporated dry stacking, capping, and tailings reprocessing, all aimed at preventing further environmental damage. As a result, the site has shown significant environmental recovery, with improved water quality and successful revegetation, highlighting the effectiveness of these rehabilitation techniques.
Brumadinho Dam, Brazil: In January 2019, the collapse of the Brumadinho tailings dam at the Córrego do Feijão iron ore mine led to one of the worst mining disasters, causing 272 fatalities. The rehabilitation efforts have since focused on a combination of in-situ stabilisation and bioremediation. Through the use of native plant species for phytoremediation, the site has seen stabilised sediments and a marked reduction in contaminant levels, demonstrating the potential of ecological rehabilitation approaches.
Overcoming challenges
Despite significant advances in tailings dam rehabilitation, numerous challenges remain. One of the primary hurdles lies in the technical complexities of addressing the variability in tailings composition, geological conditions, and environmental factors between different mine sites. These differences often necessitate tailored, site-specific solutions, complicating the rehabilitation process and extending project timelines.
Another key challenge is the high cost associated with rehabilitation efforts. Securing long-term funding for these projects can be difficult, particularly when budgets are tight. Furthermore, regulatory environments vary widely across regions, creating additional hurdles when implementing innovative rehabilitation strategies, especially when they must comply with a range of legal and administrative requirements.
Looking ahead, research and development must focus on cost-effective yet high-quality solutions for tailings dam rehabilitation. Enhanced monitoring technologies, such as drones and remote sensing, offer the potential to provide real-time data on dam conditions and track rehabilitation progress, improving safety and efficiency.
Innovative solutions for a sustainable future
To ensure tailings dams are safer and more eco-friendly, innovative approaches are essential. Techniques like dry stacking, capping, phytoremediation, bioremediation, in-situ stabilisation, reprocessing, and constructed wetlands all hold promise. While challenges persist, ongoing research, technological advancements, and collaborative efforts can pave the way for safer and more sustainable tailings management.
The future of tailings dam rehabilitation lies in continued innovation and adaptation. To transform these dams from environmental liabilities into assets that benefit both communities and ecosystems, the mining industry must evolve its strategies and embrace new ideas in managing the legacy of tailings dams.
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