Water and the Environment
The future of tailings-free mining
Mariana and Brumadinho were two of the most catastrophic industrial accidents in the history of Brazil. The Brumadinho disaster claimed 240 lives and left some 12 million cubic meters of waste material in water courses. For its part, the Mariana disaster claimed 19 lives and left approximately 60 million cubic meters of tailings in the Gualaxo do Norte, Carmo, and Doce rivers and in the Atlantic Ocean. The collapse of tailings piles can have a long-term negative impact on water quality and cause severe ecological damage and human health risks, as polluted particles can remain in the soil and water for years.
To date, the causes of the collapses are not fully understood. Some experts believe that it is very complicated to prevent dam collapse, and accidents involving dams are often considered natural disasters. In the case of Mariana, the increase in volume of waste material in the dam was a factor that could have affected the safety of the facility. At Brumadinho, on the other hand, the expert panel of experts commissioned by Vale to investigate the catastrophe concluded that there was no evidence of distress prior to the collapse. However, the high-water level and improper drainage may have caused the dam to break down.
Brazil is a key global player in the mining world, and the ramifications of the accidents were global. The Mariana and Brumadinho collapses were directly responsible for the creation of Global Industry Standard on Tailings Management (GISTM), developed by the ICMM, the UNEP, and the Principles for Responsible Investment. Rohitesh Dhawan, president of the ICMM, celebrated the steps forward: “ICMM members committed that for tailings dams with the highest consequence classifications, extreme or very high, they would disclose their levels of conformance by August of 2023. All members have done that, including our members who operate in Brazil.”
After the disasters, public debate focused on lax legislation on environmental, water and dams issues. In response, the government implemented a series of reforms and amendments to the National Dam Policy, the National Environment Fund Law, the National Water Resources Policy and the Mining Law to improve dams’ safety. Among the most notable changes is Law 14.066, which passed in 2020 and took effect in February 2022. This law prohibits the construction of dams using upstream methods. It also requires all companies to develop a dam safety plan and an action and emergency plan, register structures in the System for Safety Management of Mining Dams (SIGBM), and prepare a regular report on dam safety. These requirements have created high demand for engineering and consulting services. In terms of water management, some believe that Brazilian legislation still has weaknesses, especially when it comes to water management in the mining sector. Daniel Bertachini, executive director of MDGEO, explained: “Within the mining sector, there are specific issues in water resource management that deserve attention. At times, regulatory requirements can become cumbersome, leading to significant investments in studies that may not always yield practical risk mitigation insights.”
"Tailings dam footprints organically increase over the life of the mine and so do the associated environmental risks and impacts."
André Estêvão Silva, Managing Director, Huesker South America
Mining companies are considering more variables to ensure the safety of their tailings facilities and properly address environmental remediation in the event of spills. Mining companies not only focus on geotechnical factors, such as the stability of slopes and water levels to guarantee the safety of tailings facilities, but also consider other hydrogeological factors such as water quality, drainage and availability.
In this context, companies specializing in water management, geophysics and geoprocessing have seen an increasing demand for technologies such as data analytics and real-time monitoring to minimize the risk associated with tailings dams, as well as studies to ensure an alternative water supply in the event of a disaster.
It is vital that mines utilize tools such as dewatering technology to ensure that tailings dams are safe while maximizing their capacity. André Estêvão Silva, managing director of Huesker South America, a company that produces geomembranes, noted the importance of technology for tailings dam reduction: “When tailings dams reach their capacity, the common solution is to build a new tailings storage facility, but this creates environmental risks, increases capital outlay and has new permitting requirements.”
Geomembranes are a vital tool not just to reduce water waste, but also to meet regulatory requirements by reducing the risk of contamination. Leandro Dhein, commercial director of AzulPack TechGround, which produces geomembranes for use in tailings dams, noted: “Reducing environmental impact means preventing soil and groundwater contamination.”
Another important variable that mining companies are increasingly concerned about is chemical stability. To ensure chemical stability requires skilled analysis. Flávio Vasconcelos, CEO of Hidrogeo Engenharia, noted: “Chemical stability plays a critical role in the safety of tailings dams, as chemical compounds can alter the physical and mechanical properties of the tailings."
Technology is playing a critical role in addressing the environmental impacts of tailings dams. Eduardo Yassuda, president of Tetra Tech in South America, provided an example: “We developed a microseismic system, with microphones listening on a low frequency, that can determine if there is a change in the composition of the dam. For example, if there is more water in the tailing dam, the velocity of sound propagation changes.”
"The essential puzzle for the industry is how to extract minerals with the lowest possible environmental impact. Control of contaminants is essential in the mining industry."
Leandro Dhein, Commercial and Marketing Director, AzulPack TechGround
Tractebel is also applying new technologies to dealing with tailings dams’ risks. One example is combined tailings disposal that reduces acid rock drainage, which poses a significant threat of freshwater pollution. Cláudio Maia, CEO of Tractebel Latin America, said: “Many mining companies are shifting from traditional tailings dams’ structures in favor of alternative disposal methods such as combined disposal.”
Eugenio Singer, general manager at Ramboll, cited the recent use of hyper saturated oxygenation technology in a hyperbaric chamber to restore aquatic life in a contaminated river in São Paulo as an example of technology usage in remediation processes. “We see a lot of growth potential in environmental studies with a focus on ESG, such as climate change adaptation and biodiversity conservation studies,” explained Singer.
Progress tailings management has been made across the board, and companies are opting into standards even stricter than the regulations require. Indeed, it was Brumadinho and Mariana that inspired the ICMM to develop the Global Industry Standard on Tailings Management (GISTM), according to Dhawan of the ICMM, who affirmed that all ICMM members in Brazil have disclosed their conformance levels as of August of 2023.
This is part of a larger willingness within the industry to change how business is done, enthusiastically committing to improvements in operational practices and regulatory conformity. “The design, construction and operation investigation procedures are in the most advanced stage,” explained Joaquim Pimenta de Ávila, CEO of Pimenta de Ávila Consultoria. “There are excellent structures for sharing knowledge about tailings dams.”
Image courtesy of Equinox Gold