Environmental and Tailings Management

Issues such as water use and tailings disposal are growing incrementally

In the wake of the Brumadinho tragedy in 2019, the International Council on Mining and Metals (ICMM) conducted a multi-stakeholder review with investors and the United Nations Environment Programme (UNEP) that resulted in the Global Industry Standard on Tailings Management, launched in August 2020.

The investigation led by the Investor Mining & Tailings Safety Initiative revealed that around a tenth of tailings dams – 166 of the 1,635 dams studied — have had safety issues in the past. Considering there are over 3,500 tailings dams globally, the challenge at hand will require buy-in from all parties, and not just the major ICMM members. Rohitesh Dhawan, CEO of the ICMM, affirmed that the Council’s main priority is to continue enabling the global industry to take up the new Global Industry Standard on Tailings Management, for which a Good Practice Guide as well as Conformance Protocols have been launched in 2021. “Our ambitious goal is to find solutions that will significantly reduce or directly eliminate tailings in the first place,” he added.

The Investor Mining & Tailings Safety Initiative was established by a group of asset owners and fund managers including the Church of England Pensions Fund, the New Zealand Superannuation (NZ Super), as well as Swedish and Dutch pension funds. The current group now controls over US$24 trillion in assets, according to Adam Matthews, investment team director for the Church of England Pensions Board, and co-chair of the Investor Mining & Tailings Safety Initiative. He stressed that “investors do not invest in a vacuum” and sector-wide reform is necessary if mining companies expect to retain investment.

At the forefront of this reform are the engineering firms and services related to mining waste. Dan Etheredge, general manager of Klohn Crippen Berger’s (KCB) South American office in Lima, revealed that 2020 was one of the most active years ever for the engineering firm that specializes in tailings management, and credited the Global Tailings Standard for generating more awareness on the subject. Etheredge commented that the bulk of KCB South America’s projects are tailings related, such as seismic hazard assessment updates and site selection studies, and commented on how clients have started taking a more long-term approach in their thinking.

“For example, they have 10 years capacity left on their existing facility and want to know what their options are moving forward – do I go to a new facility, or do I raise the dam of the existing facility?,” said Etheredge, adding: “Thoughts are also moving more towards lowering risks profiles – instead of having one massive structure with an extreme consequence classification, analyzing the impact of a couple of smaller structures with lesser classifications.”

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“Tailing dams suffer a lot from pore pressure and the soil can become extremely saturated. Drainage geocomposites, in conjunction with other geosynthetics, line the bottom of the dam to reduce any pore pressure which could affect the stability of the structure. The Brumadinho dam disaster in Brazil is the best case to promote this solution, as the main fault that occurred was a lack of proper drainage.”

Francisco Pizarro, Composites Commercial Director – Latin America, Elydan

Peruvian mining contractor Pevoex has also seen an uptick in demand for tailings work, particularly for tailings dam expansion projects, according to general manager Rómulo Mucho. “These projects are highly technical as they involve a critical facility with associated risks, as seen with the dam failures in Brazil in recent years,” said Mucho, who spoke of the strict criteria for projects including Quellaveco, for which Pevoex is a subcontractor of the company building the tailings dam.

Mucho added that the industry is adopting solutions like filtered tailings, for instance at Cerro Lindo, but the cost of such solutions make them more applicable to projects with lower volumes.

When it comes to the design of modern tailings facilities or upgrades to existing facilities, water use is at the crux of the matter. The previous mainstream method of tailings management, subaqueous deposition as used at Brumadinho, is being replaced by dry stacking, a method which permits the recovery of the maximum amount of recycled water but requires more capex.

Amphos21, the Spanish company acquired by RSK Group on December 28th, 2020, covers a wide range of services inside the water cycle including environmental studies and how water is integrated throughout the life of a mine.

Eduardo Ruiz, general manager of Amphos21, expanded on a number of the long-term projects the company is currently involved in in Peru: “We are working in dewatering activities for Antamina, in tailings reuse, and in the dewatering process of Minsur’s tailings facility. Not only do we work in consulting and engineering, but also in the design of solutions so we can provide engineering, procurement, and construction for clients.”

Amphos21 recently won the Smart Catalonia Challenge competition for using technology based on machine learning to improve the management of water quality, noted Ruiz, remarking that the company is currently applying this type of technology in a similar project in Peru.

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The issue of mining waste is growing incrementally as mines increasingly extract lower grade ore. Such a large-scale problem requires cross-industry R&D to generate solutions. French company Elydan, with broad experience in providing solutions for landfills across Europe and Latin America, is now bringing its experience to the mining industry, according to Francisco Pizarro, Elydan’s composites commercial director for Latin America. Pizarro explained how Elydan’s drainage geocomposites can replace part of the soil or rocks that are used for drainage in tailings dams, leach pads or any solid structure that can suffer from saturation, with a thin but efficient product. “Tailing dams suffer a lot from pore pressure and the soil can become extremely saturated. Drainage geocomposites from Elydan, in conjunction with other geosynthetics, line the bottom of the dam to reduce any pore pressure which could affect the stability of the structure.”

Using the example of Brumadinho, where the main fault that occurred was due to a lack of proper drainage, Pizarro emphasized the value of geosynthetics to solidify mining sites structures. He revealed that Elydan is currently doing a year-long test trail of 1,000 square meters of drainage for a tailings dam in Chile, with the possibility to install 100,000 square meters of the solution once the trial has been successful.

Image courtesy of Amphos21