Safe & Sustainable Tailings Management Safe and Sustainable Tailings Management, Compliant Mining

Tailings production is inherent to mining and metals processing. Ensuring their safe and sustainable management should be viewed as a burden, but a benefit in the bigger scheme of things - compliance with Environment, Social and Governance (ESG). Thankfully, with clarity, the global standard on tailings management provides the scope of key elements to be adopted and implemented.

Catastrophic tailings dam failures at Brumadinho (Brazil) in 2019, Samarco (Brazil) in 2015 and Mount Polley (Canada) in 2014 and similar ones that have occurred in the past few years typify what can go wrong when best practice in tailings management is ignored or neglected in mining operations. Brutally, the accidents exposed inherent systemic gaps in how mining companies approach tailings management.

As expected, following the events, there is an increased obligation on mining companies to ensure safe and sustainable tailings management. There is more emphasis on best practice in tailings storage facilities, as well as water-use reduction and water storage.

The question is: How can mining companies achieve safe and sustainable tailings management through tailings storage facilities, water-use reduction, and water storage?

Global Industry Standard on Tailings Management

The Global Industry Standard on Tailings Management (the Standard) provides guidelines for mining companies to reference. It was developed by the United Nations Environment Programme (UNEP), Principles for Responsible Investment (PRI) and International Council on Mining and Metals (ICMM through an independent process – the Global Tailings Review (GTR).

The Standard applies to existing and future tailings facilities, wherever they are and whoever operates them. Specifically, it is aimed at strengthening current practices in the mining industry. It embodies social, environmental, local economic and technical considerations.

No stone unturned

The Standard leaves no stone unturned. It calls for tailings management to be effective throughout the life of an operation (the entire tailings facility lifecycle) - from site selection, design and construction, through management

Spotlight on Sustainable Mining - Best Practices in the Safe and Sustainable Management of Tailings and Mine Residue

Weall need mining by-products in the world in which we, and with every mine, the extraction of the metals and minerals results in a process residue or tailings. However, there is more and more pressure being placed on the industry to minimise mine residue, and/or their impacts. Sustainable mining must either put the mine residues back where they came from, find a market/use for it, and/or create a land-use equal or better than was in place prior to mining. This typically requires a waste hierarchy approach of avoidance, conversion to a new use, minimisation, re-use or storage. Such practical examples include;

• Traditional surface “disposal” in tailings storage facilities (TSFs), which should be strongly challenged at the design stage to evaluate alternatives, and if surface storage is selected, it must be designed such that it does not pose a threat during operation or post-closure. New technology in this field revolves around dewatering of the tailings using filtration and then dry stacking it, or co-disposing it with overburden material. These options do little to minimise waste, but rather try to reduce the footprint, failure and closure risks.

• Re-processing of old TSFs is common practice as they have become resources as processing technology has improved. However, this processed tailings has to be stacked somewhere, unless a new use can be found for it, such as in construction materials. The benefit of reprocessing is that multiple TSFs can be re-mined and combined into one new TSF, with overall smaller impact, provided rehabilitation of the old footprints and the new TSF can be done sustainably.

• In-pit disposal of tailings is also common practice, but is only possible once the orebody has been mined out, and any remaining ore is not considered feasible and can be sterilised. Surface and in-pit TSFs will be needed in this case.

• Backfilling of underground mines is good practice, and can be done simultaneously with mining, either for support and strata control, or simply to fill voids. This can however only account for about 45% of the tonnage due to the loose state the tailings is placed compared to the density of rock.

• Ore and waste sorting is a method that can be used to minimise the volume of ore that is crushed and processed, using various density, magnetics, X-ray or other technologies to separate it out. This may not reduce the overall volume of waste, but does reduce energy and water consumption for processing, and land area occupied by TSFs.

• Robotic mining that only extracts the ore, or ore with as little waste as possible. Some mining methods and equipment already target this approach, but many are not as selective.

• In-situ mining or processing, by leaching the minerals in-situ and abstracting the metal/mineral rich solution. However this can leave behind a contaminated “depleted orebody” due to the reagent used to leach the ore, and must be rehabilitated in-situ.

Knight Piésold can offer a full range of design capabilities for the safe management of the surface TSF options to achieve the most sustainable solution. The location of each mine affects the optimal solution, as well as the type and depth of the orebody, and the mining and processing method. More and more mining companies are considering new technologies and safer TSFs than before, not only because of the consequences associated with hydraulic deposition, but because of the need to design for closure, and to secure licences to operate.