What are tailings? How to manage them using geosynthetics?

Tailings are the residual materials left after the extraction of valuable minerals from ore during mining processes, typically consisting of finely ground rock, water, and chemical reagents. In this post we want to talk about tailing management.

What are tailings?

If you want to know what are tailings we can say tailings are the leftover materials after the extraction of valuable minerals from ore during mining operations. These residues are a mix of finely ground rock, water, and chemicals used in the extraction process. Depending on the type of ore and the extraction method, tailings can contain harmful substances like heavy metals, sulfides, and chemical reagents. They are typically stored in tailings ponds or dams, where they can pose significant environmental and health risks if not managed properly, potentially leading to soil, water, and air contamination.

To mitigate these risks, tailings require careful management and disposal strategies. Modern practices include using lined and monitored storage facilities, dry stacking to reduce water content, and progressive rehabilitation of tailings areas. Reclamation projects aim to stabilize and restore closed or abandoned tailings sites, preventing further contamination and repurposing the land for natural or economic use. Effective tailings management is crucial to minimizing the environmental impact of mining activities.

What are the different types of tailings?

Tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore. The types of tailings can vary significantly based on the ore being processed, the extraction methods used, and the subsequent treatment of the tailings. Here are the primary types of tailings:

Sulphide Tailings

These tailings are produced from the processing of ores that contain sulphide minerals, such as pyrite, chalcopyrite, and galena. Sulphide tailings can be problematic due to their potential to generate acid mine drainage (AMD) when exposed to air and water.

Oxide Tailings

Generated from the processing of oxide ore bodies, these tailings generally contain minerals like hematite, magnetite, and cassiterite. They are typically less reactive than sulphide tailings but can still pose environmental challenges.

Slimes

Slimes are fine-grained tailings that are often produced from ore beneficiation processes, such as froth flotation. These tailings can contain a mixture of fine mineral particles and chemicals used during processing, and their fine nature can make them difficult to manage and contain.

Clay Tailings

Produced from the processing of ores that contain significant amounts of clay minerals, these tailings are characterized by their high plasticity and low permeability. Managing clay tailings can be challenging due to their tendency to retain water and form stable suspensions.

Sand Tailings

These tailings consist primarily of coarser particles and are often produced from the processing of sands and gravels. Sand tailings are usually easier to handle and can sometimes be repurposed for construction or land reclamation.

Paste Tailings

These tailings are dewatered to a thick consistency, reducing the amount of free water. Paste tailings can be more stable and easier to manage, as they are less likely to cause environmental contamination.

Filtered Tailings

Filtered tailings are produced by removing most of the water from the tailings, resulting in a dry, stackable material. This method can reduce the risk of dam failures and environmental contamination.

Radioactive Tailings

These tailings result from the extraction of radioactive ores, such as uranium or thorium. They require special handling and disposal methods to mitigate the risk of radiation exposure and environmental contamination.

Coal Tailings

Produced from coal washing and processing, these tailings can contain a mix of coal fines, clays, and other minerals. Coal tailings can pose environmental hazards due to their potential for spontaneous combustion and acid generation.

Oil Sands Tailings

Generated from the extraction of bitumen from oil sands, these tailings contain a mixture of water, sand, clay, and residual bitumen. Managing oil sands tailings is complex due to their large volume and the environmental impacts of tailings ponds.

Red Mud

A byproduct of the Bayer process for refining bauxite into alumina, red mud is highly alkaline and can contain various hazardous components. Safe disposal and management of red mud are critical to prevent environmental damage.

Phosphogypsum

A byproduct of the production of phosphoric acid from phosphate rock, phosphogypsum is slightly radioactive and can contain heavy metals. Its disposal poses significant environmental challenges.

The environmental impact of tailings

Tailings from mining operations can have significant environmental impacts. Here are some key considerations:

1. Water Contamination: Tailings often contain toxic substances such as heavy metals (e.g., lead, mercury, arsenic) and chemicals used in the extraction process. If not properly managed, these contaminants can leach into nearby water bodies, affecting aquatic ecosystems and human health.
2. Ecosystem Disruption: The disposal of tailings can disrupt natural habitats. Large tailings impoundments alter landscapes, displace wildlife, and destroy vegetation. Additionally, the release of acidic or alkaline tailings can harm soil quality.
3. Dust and Air Pollution: Dry tailings can generate dust, which may contain harmful particles. Wind can carry this dust over long distances, impacting air quality and human health.
4. Dam Failures: Tailings dams can fail, leading to catastrophic consequences. Dam breaches release massive volumes of tailings into rivers or surrounding areas, causing environmental devastation and loss of life.
5. Long-Term Legacy: Tailings remain in the environment for decades or even centuries. Proper management, reclamation, and monitoring are essential to mitigate long-term impacts.

The role of Geosynthetic materials in tailings management

A geosynthetic product play a crucial role in tailings management by providing solutions that enhance the stability, environmental protection, and efficiency of tailings storage facilities. Here are the key roles of geosynthetics in tailings management:

1. Lining Systems: Geosynthetic liners, such as geomembrane sheets, are used to line tailings ponds and storage facilities. These liners create a barrier that prevents contaminants from leaching into the ground and groundwater, thus protecting the surrounding environment from pollution. They are often used in conjunction with clay or other natural materials to create composite lining systems that enhance overall impermeability.
2. Filtration and Drainage: Geotextiles and geocomposites are used to facilitate proper drainage and filtration within tailings facilities. These materials help manage the flow of water, preventing the buildup of excess pore water pressure which can lead to instability and failure of tailings dams. They ensure that water is efficiently drained away from the tailings, reducing the risk of dam failure and promoting safer storage.
3. Reinforcement and Stabilization: Geogrids and geocells are used to reinforce and stabilize the slopes and embankments of tailings storage facilities. These materials provide additional strength and support, helping to prevent erosion and slippage. This reinforcement is particularly important for maintaining the structural integrity of tailings dams and preventing catastrophic failures.
4. Erosion Control: Geosynthetic erosion control products, such as erosion control blankets and turf reinforcement mats, are used to protect the surface of tailings storage areas from wind and water erosion. These products help establish vegetation and stabilize the surface, reducing the spread of tailings dust and minimizing environmental contamination.
5. Capping and Closure: Geosynthetics are used in the capping and closure of tailings facilities. Geomembranes, geotextiles, and other geosynthetic products can be used to cap the surface of closed tailings storage areas, preventing water infiltration and minimizing the potential for acid mine drainage. This helps to secure the tailings in place and allows for the reclamation and rehabilitation of the land.

Types of Geosynthetics used for tailings management

Several types of geosynthetic products are used in tailings management to address various engineering and environmental challenges. Here are the main types:

1. Geomembranes: These are impermeable liners typically made from polymers such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), or polyvinyl chloride (PVC). Geomembranes are used as barriers to prevent leachate from contaminating the surrounding environment, making them essential for lining tailings ponds and storage facilities.
2. Geotextiles: These are permeable fabrics made from synthetic fibers, such as polyester or polypropylene. Geotextiles are used for filtration, separation, and reinforcement. They help manage water flow and prevent the migration of fine particles, ensuring stability and drainage within tailings storage facilities.
3. Geogrids: These are grid-like structures made from polymers such as polyethylene or polypropylene. Geogrids are used to reinforce and stabilize the slopes and embankments of tailings storage facilities. They provide tensile strength, preventing erosion and enhancing the structural integrity of the storage facility.
4. Geocells: These are three-dimensional, honeycomb-like structures made from polymer sheets. Geocells are used for soil stabilization and erosion control on slopes and embankments. They confine and stabilize the infill material, reducing surface erosion and improving the load-bearing capacity of the soil.
5. Geocomposites: These are hybrid materials that combine different types of geosynthetics, such as geomembranes, geotextiles, and geonets. geocomposite sheets are used to provide multiple functions, such as drainage, filtration, and barrier protection, in a single product. They are particularly useful in complex tailings management scenarios where multiple issues need to be addressed simultaneously.
6. Geonets and Geospacers: These are net-like materials used primarily for drainage. Geonets provide a planar drainage pathway within tailings storage facilities, facilitating the removal of excess water and reducing pore water pressure. Geospacers are similar but designed to maintain space for drainage flow.
7. Erosion Control Blankets and Turf Reinforcement Mats: These are used to protect the surface of tailings storage areas from wind and water erosion. Erosion control blankets are biodegradable or synthetic mats that provide immediate protection and promote vegetation growth. Turf reinforcement mats are synthetic products that offer long-term erosion control and soil stabilization.
8. Geosynthetic Clay Liners (GCLs): These are composite materials consisting of a layer of bentonite clay sandwiched between geotextiles or geomembranes. GCLs are used as hydraulic barriers in tailings ponds and storage facilities, offering an additional layer of protection against leachate migration.

The benefits of using geosynthetic for tailings

Using geosynthetics for tailings management offers numerous benefits, contributing to safer, more efficient, and environmentally friendly mining operations. Here are the key benefits:

1. Environmental Protection: Geosynthetics, such as geomembranes and geosynthetic clay liners (GCLs), provide effective barriers that prevent contaminants from leaching into the soil and groundwater. This containment reduces the risk of environmental pollution, protecting ecosystems and water resources.
2. Enhanced Stability: Geogrids and geocells reinforce the slopes and embankments of tailings storage facilities, enhancing their structural integrity. This reinforcement reduces the risk of slope failure and erosion, ensuring the long-term stability of the storage facility.
3. Efficient Water Management: Geotextiles, geonets, and geocomposites facilitate efficient drainage and filtration within tailings facilities. Proper water management reduces excess pore water pressure, preventing dam failures and maintaining the stability of the tailings structure.
4. Erosion Control: Erosion control blankets and turf reinforcement mats protect the surface of tailings storage areas from wind and water erosion. These materials help establish vegetation and stabilize the surface, reducing the spread of tailings dust and minimizing environmental contamination.
5. Cost-Effectiveness: Geosynthetics often offer a cost-effective alternative to traditional materials and methods. They can reduce the need for large quantities of natural materials (like clay or gravel) and decrease the labor and time required for construction and maintenance.
6. Versatility and Adaptability: Geosynthetics are versatile and can be adapted to various site conditions and design requirements. They can be used in different combinations to address specific challenges in tailings management, providing customized solutions.
7. Improved Longevity: The use of geosynthetics can extend the lifespan of tailings storage facilities. By preventing leaks, controlling erosion, and enhancing stability, geosynthetics contribute to the durability and long-term performance of these facilities.
8. Facilitation of Rehabilitation: Geosynthetics play a crucial role in the closure and rehabilitation of tailings storage areas. They help cap and seal the tailings, preventing water infiltration and promoting vegetation growth, which is essential for restoring the land to a natural or economically usable state.
9. Regulatory Compliance: The use of geosynthetics helps mining operations comply with environmental regulations and standards. Properly managed tailings storage facilities with geosynthetics are more likely to meet regulatory requirements, reducing the risk of fines and legal issues.
10. Safety Improvement: By enhancing the structural stability and reducing the risk of environmental contamination, geosynthetics contribute to the overall safety of mining operations. This not only protects the environment and public health but also safeguards the workforce and surrounding communities.

What causes tailings storage facilities to fail?

Tailings storage facilities (TSFs) can fail due to various factors, often resulting from a combination of design flaws, operational issues, and environmental conditions. Here are the primary causes of TSF failures:

1. Structural Instability: Poor design or construction can lead to structural instability in TSFs. Factors such as inadequate slope angles, insufficient compaction, and lack of reinforcement can cause embankment or dam failures.
2. Excess Pore Water Pressure: Improper water management can result in excess pore water pressure within the tailings, reducing the material’s shear strength and leading to liquefaction or slope failure. Inadequate drainage systems and excessive water infiltration can exacerbate this issue.
3. Seismic Activity: Earthquakes or seismic events can induce vibrations and stress within the tailings and the storage facility, potentially leading to liquefaction, cracking, and failure of the dam or embankment.
4. Foundation Issues: Weak or unstable foundations beneath the tailings storage facility can cause settlement or differential movement, leading to structural failure. Inadequate geotechnical investigations and foundation preparations are common contributors to this issue.
5. Construction and Maintenance Errors: Errors during construction, such as poor quality control, use of substandard materials, or deviation from design specifications, can compromise the integrity of the TSF. Lack of regular maintenance and monitoring can also lead to unnoticed deterioration and eventual failure.
6. Extreme Weather Events: Heavy rainfall, flooding, and rapid snowmelt can overwhelm the drainage capacity of a TSF, leading to overtopping and erosion of the embankment. Climate change and unpredictable weather patterns have increased the frequency and intensity of such events.
7. Operational Mismanagement: Improper operation of the TSF, such as overfilling, rapid deposition rates, and inadequate supervision, can lead to instability. Tailings deposition practices that do not account for the facility’s capacity and design parameters can exacerbate risks.
8. Chemical Reactions: Certain chemical reactions within the tailings, such as acid mine drainage (AMD) resulting from the oxidation of sulfide minerals, can weaken the material and lead to structural degradation over time.
9. Inadequate Monitoring and Early Warning Systems: A lack of comprehensive monitoring systems and early warning mechanisms can prevent the timely detection of issues like excessive deformation, increased pore water pressure, or seepage. Without these systems, early intervention to prevent failure becomes difficult.
10. Human Error and Negligence: Human factors, such as insufficient training, poor decision-making, and lack of adherence to safety protocols, can contribute significantly to TSF failures. Organizational and management failures, including inadequate risk assessments and emergency preparedness, also play a role.

Case studies and success stories of tailings

Here are some notable case studies and success stories in tailings management, showcasing how innovative approaches and best practices can lead to effective management and even repurposing of mine tailings.

BHP Billiton’s Olympic Dam Tailings Storage Facility (Australia)

BHP Billiton’s Olympic Dam operation in South Australia is one of the world’s largest underground mines. The company has implemented advanced tailings management practices, including:

• Thickened Tailings Technology: BHP uses thickened tailings technology to reduce water content, leading to more stable tailings.
• Progressive Rehabilitation: The company undertakes progressive rehabilitation of tailings storage facilities, covering them with layers of soil and vegetation to prevent dust and erosion.

Teck Resources’ Red Dog Mine (Alaska, USA)

Teck Resources operates the Red Dog Mine in Alaska, one of the world’s largest zinc mines. The mine has been praised for its environmental management, particularly regarding tailings:

• Water Treatment: Teck has implemented extensive water treatment systems to ensure that water discharged from the tailings facility meets strict environmental standards.
• Community Involvement: The company works closely with local indigenous communities to monitor environmental impacts and ensure sustainable practices.

Barrick Gold’s Cortez Hills Mine (Nevada, USA)

Barrick Gold’s Cortez Hills Mine in Nevada employs innovative tailings management techniques:

• Dry Stacking: The mine uses dry stacking of filtered tailings, which significantly reduces water usage and the risk of dam failures.
• Reclamation: Barrick has a comprehensive reclamation plan that includes re-vegetation and landscape restoration, ensuring that areas impacted by mining are returned to a natural state.

Newmont’s Boddington Gold Mine (Australia)

Newmont’s Boddington Gold Mine in Western Australia has implemented several successful tailings management strategies:

• Thickened Tailings Disposal: The mine uses thickened tailings disposal, which reduces the volume and footprint of tailings storage facilities.
• Water Recycling: Newmont has established systems to recycle water from tailings, reducing the mine’s overall water consumption.

Vale’s Samarco Mine (Brazil)

Following the tragic tailings dam failure in 2015, Samarco, a joint venture between Vale and BHP, has undertaken significant measures to improve tailings management:

• Filtered Tailings: Samarco has shifted to using filtered tailings technology, allowing tailings to be stacked dry, reducing the risk of dam failures.
• Restoration Projects: Extensive efforts have been made to restore the environment affected by the tailings spill, including reforestation and water quality improvement projects.

Anglo American’s Quellaveco Project (Peru)

The Quellaveco copper project in Peru, operated by Anglo American, is a notable example of modern tailings management:

• Integrated Waste Management: The project uses an integrated waste management approach, combining tailings and waste rock to improve stability and reduce environmental impact.
• Community Engagement: Anglo American has engaged local communities in tailings management planning, ensuring transparency and addressing community concerns.

Rio Tinto’s Kennecott Utah Copper (USA)

Rio Tinto’s Kennecott Utah Copper operation has implemented several tailings management innovations:

• Tailings Reprocessing: Kennecott reprocesses tailings to extract additional valuable minerals, reducing waste and generating additional revenue.
• Environmental Monitoring: The operation includes comprehensive environmental monitoring systems to track the impact of tailings and ensure compliance with environmental standards.

Hudbay Minerals’ Constancia Mine (Peru)

Hudbay Minerals’ Constancia Mine in Peru has been recognized for its responsible tailings management practices:

• Thickened Tailings: The mine uses thickened tailings technology to reduce water usage and improve tailings stability.
• Progressive Rehabilitation: Hudbay has implemented a progressive rehabilitation program, ensuring that areas impacted by tailings are restored over the life of the mine.

Conclusion

Finally understanding and managing tailings responsibly is crucial for sustainable mining operations and environmental stewardship.