Tailings dams have failed too often and for too long, with shocking consequences for human life and the environment. The devastating collapse of the Brumadinho tailings dam in Brazil in 2019 is a recent example in a very long history of major tailings storage failures worldwide. However, out of the tragedy has come an important development for the international mining industry: the Global Industry Standard on Tailings Management (GISTM), published in August 2020 by the International Council on Mining and Metals (ICMM), the United Nations Environment Programme (UNEP), and the Principles for Responsible Investment (PRI).
As an international champion for safer and more sustainable mining, WSP regards the launch of the GISTM as a milestone in the industry, with most major mine owners adopting the standard as a key component of their governance. The standard arises from the societal expectation that the mining industry needs to do more to achieve the goal of zero catastrophic failures. Through the use of six topics, the GISTM sets out a framework for prioritizing safety throughout the life of a tailings facility, including design, operation, closure, and post-closure.
Building on the GISTM, discussions with industry leadership, and experience as an Engineer of Record, we view four areas as key to future success in tailings management.
1. Design must be robust, flexible, and resilient and must identify all credible failure modes
Good design saves lives. When the design is robust, resilient and redundant, we plan for and seek to engineer away, to the extent practicable, the potential for failure. Topic III of the GISTM sets out a detailed framework for design, construction, operation, and monitoring of a tailings storage facility and identifies the need to consider all credible failure modes, as this is where many of the problems with tailings dams arise.
To minimize, as far as is reasonably practical, the potential for a failure to occur, it is essential to have identified the range of potential failure modes and to have a design defense and strong control in place for each credible failure mode, with clear links between failure mode, design defense, and monitoring. The need for a robust design is often at odds with the desire to minimize costs. Generally, a robust design may be perceived to add non-essential cost, but cost-cutting is a sure path to disaster. The safety of communities and the environment must never be compromised, and the costs of a failure far outweigh the incremental cost of robust design.
Technology will keep improving, so it is also important to consider all available options. We need to keep the door open to incorporating new technologies rather than locking in a particular concept that is unchangeable. For instance, as filter technology improves there will be opportunities to use filtering to dewater tailings at higher production rates, enabling a reduction in the volume of tailings stored in above-ground wet facilities.
However, changing the technology is not without challenges. There will be cost implications, other failure mechanisms to manage, and different requirements for closure. Removing water, particularly a surface pond, will certainly reduce the extent to which a flow failure could occur and how far a flow failure can travel. However, even though a filtered tailings system reduces the risk to human life, it will require special measures to manage dust, control oxidation of reactive sulphides and leaching of metals, and mitigate the effects of rainfall, and therefore can still have significant implications for the environment, the community, and reputation.
2. Education is needed across the industry
With the GISTM’s increased requirement for designated engineering positions, technical reviewers, accountable executives and skilled operators, there will be a significant need for education and training, upskilling and knowledge sharing throughout the industry. Global best practices will need to be disseminated not only to clients, but also to consultants, regulators, and stakeholders.
As an industry, we cannot continue to do only what we’ve done before. In some jurisdictions, new options aren’t taken on board because they haven’t yet been proven. It is time to draw on our global experience to adopt the best of what is available and proven in other parts of the world. We also need to cross-train and upskill our people to be able to implement these technologies and methods, and to strengthen the industry mindset towards managing credible failure modes. If managing credible failure modes could be as important a KPI as being ahead of schedule or under budget, we would build a safer industry. Mistakes happen when costs are the main focus or when rushing to meet a schedule.
The best way for us, as an industry, to learn is by deeply examining what has failed before — and why it failed. We must revisit the failure modes that haven’t been adequately considered in historical failures and learn these lessons from the past. With this insight, we can build a robust approach to understanding how tailings facilities fail and put the appropriate design defenses and controls in place to mitigate risk.
3. Governance in the operational stage is critical
Governance is a fundamental component of a safer tailings facility. Topic IV of the GISTM sets out the need for an accountable executive, a Responsible Tailings Facility Engineer, an Engineer of Record, and ongoing, regular risk management and safety reviews. It is also essential to have the right people involved both in design and in operations, including not only the technical (design) people, but also the operators, environmental and water specialists, mine planners and other stakeholders. A holistic view allows us to take advantage of opportunities as they arise (e.g., using mine waste to construct embankments, or using part of the tailings stream for underground backfill) and enables deviations from the design to be identified well ahead of time (e.g., a change in process), enabling implementation of corrective measures.
Implementing a detailed, stringent, regular process of risk assessment is the essential counterpoint to the design flexibility discussed earlier. Once the facility is in operation, change is inevitable. The plant will change and there is likely to be at least some variance in processing rates, throughputs, methods, grinds, water demands and, more broadly, regional hydrogeology, and climatic patterns. Therefore, it is critical that the assumptions made during the design are continuously reviewed and assessed in the light of actual conditions.
4. Design with closure in mind
Tailings storage facilities stay in place for a very, very long time – many will be there forever. Both in the design stage and during operations we should always be thinking about what will be left behind for the local community when the operational life of the mine comes to its inevitable end. Will our projects leave a positive legacy, or will we simply walk away, leaving the community with a perpetual risk?
There are many opportunities to shift the paradigm of mine closure by applying innovative, sustainable solutions that will maximize community benefits. Tailings can be used to support a community industry (e.g., creating bricks) or deliver additional value (e.g., generating renewable energy by installing solar panels on the dam).
To mitigate the long-term ongoing risk to the community and the environment, credible failure modes must be carried through and reviewed regularly in perpetuity, so that there’s always a deep understanding of how things could go wrong and how all the controls are working to prevent failure.
This is what it all comes down to: the goal of managing tailings for zero harm to people and the environment with zero tolerance for human fatalities. The GISTM is a very significant step in the right direction towards safer and more sustainable tailings management, and WSP stands ready to support its implementation across the world.
About the Author
Peter Chapman is a Principal Tailings Engineer based in WSP‘s Perth office. Peter has more than 18 years of experience in civil engineering, specializing in tailings and heap leach design. His main role is lead engineer/project director on tailings projects ranging from scoping studies to feasibility studies and detailed engineering, supervision and direction of design analyses, supervision of specialist tailings test work programs and closure planning. Peter is Engineer of Record for multiple sites and a leader in WSP’s global mining business