Responsible tailings management is becoming increasingly critical for miners across the world as they try to meet growing demand for minerals while also improving the efficiency and sustainability of their operations.
There are numerous mitigation solutions to reduce or process mine tailings, which should be implemented within a comprehensive management strategy that details a mine closure approach and provides a transparent governance structure.
Maintenance and closure of tailings storage facilities is a complex, time-consuming and resource-intensive phase of the mining lifecycle, requiring extensive environmental assessments, long-term monitoring, rehabilitation, and strategies to manage safety, environmental impacts and social risks.
Earlier this year, the International Council on Mining and Metals (ICMM) updated two of its key resources, both relating to how mining companies plan and manage the closure of tailings storage facilities.
The second edition of ICMM’s Tailings Management Good Practice Guide and the third edition of Integrated Mine Closure Good Practice Guide introduce enhanced strategies for integrating tailings management and mine closure processes. They reflect the latest industry knowledge and help strengthen the governance and long-term stability of closed facilities.
The updates support miners by developing meaningful success criteria for closure of a tailings storage facility, setting clearer governance structures during closure and post-closure stages, and improving integration of closure considerations into tailings storage facility design and operation.
Dr Emma Gagen, Director at ICMM, explained that closure was a critical phase of every mining or metals processing operation, presenting an opportunity to strengthen environmental, social and economic resilience far beyond the mine’s lifecycle.
She said: “Achieving these positive outcomes hinges on early planning and progressive closure approaches – especially for tailings storage facilities, where risks can extend long after operations cease.
“ICMM’s updated tailings management and integrated mine closure guidance will help companies to continually learn and improve, raising the bar on safety and environmental stewardship across the sector for decades to come.”
In the wake of the catastrophic 2019 tailings dam failure at Vale’s Corrego do Feijão iron ore mine in Brazil, a global tailings review was conducted by a multi-disciplinary expert panel that included ICMM and the United Nations Environment Program, which subsequently established a new Global Industry Standard on Tailings Management (GISTM).
The Corrego do Feijão disaster released about 12 million cubic metres of tailings that completely engulfed the mine’s administrative area, burying hundreds of mine employees alive, before passing through a small nearby community to reach the Paraopeba River.
The initial review estimated there were approximately 18,000 tailings facilities worldwide, but only 3,500 of these were active, and the new standard does not cover the many inactive and abandoned facilities.
Underpinning the industry standard is an integrated approach to tailings management, which aims to prevent catastrophic failure as well as enhance the overall safety of mine tailings facilities.
Its core purpose is to provide a framework for safe tailings facility management, where the design, construction, operation, monitoring and closure of tailings facilities are required to be robust, in turn minimising the risk of harm to people and the environment.
One of the major technical differences between the GISTM and previous guidance is that the standard utilises a revised base classification, which over the facility’s lifecycle will upgrade the existing status to ‘extreme’.
The new standard and its provisions are generally more advanced than existing tailings management guidance, addressing issues such as public disclosure and transparency of information on tailings facilities.
ABOUT THREE MAJOR DAM FAILURES EXPECTED EVERY YEAR
Tailings dams are more susceptible to damage than other types of water storage structures, and their high failure rate has highlighted the need for effective maintenance strategies and better facility design.
Tailings dam design is highly dependent on the static and cyclic characteristics of the tailings used and the geological and hydrogeological conditions of the disposal site.
A study from last year examined iron ore dam failures over the last century, finding that 31.25 per cent collapsed due to slope instability, 18.75 per cent due to overtopping, and 6.25 per cent each to liquefaction-related instabilities, foundation failure, erosion, and structural failure.
There were 198 tailings dam failure events reported globally before 2000, 20 failure events between 2000 and 2010, and a further 11 failure events were reported from 2010 to 2015.
Based on the results from more than 18,000 mines worldwide, the tailings dam failure rate across the past century was estimated at 1.2 per cent, whereas the failure rate of traditional water storage dams has been 0.01 per cent. On average, three of the world’s 3,500 active tailings dams fail every year.
Despite the introduction of a new global tailings standard, another 19 incidents are predicted in the next decade based on a rate of two to five major failures and 35 minor failures every year.
Another study from 2022 reported 257 tailings dam failures since 1915, which collectively accounted for 2,650 fatalities and the release of 250 million cubic metres of tailings into the environment.
Nearly half of the total volume, about 115 million cubic metres, comes solely from post-2000 dam failures.
The authors explained that advances in mining technology over the past 100 years had made it economically feasible to mine lower grades of ore and increase excavated volumes.
They added: “On the other hand, until recently, there has been little change in practices related to management of the increased tailings volumes.
“The uncertainties on physical and chemical characteristics of tailings, together with dam management practices, are of growing concern.”
Climate change is also an exacerbating factor, with the study noting that heavy rainfall was thought to have triggered a quarter of global tailings dam failures and 35 per cent of failures across Europe.
