Last week, mining giants BHP (ASX:BHP) and Vale (NYSE:VALE) signed a 170 billion reais ($45 billion) compensation deal with Brazil over the 2015 Mariana tailings dam collapse that killed 19 people.
The incident at the iron ore mine owned by Samarco — a joint venture between BHP and Vale — left hundreds of people homeless, forests flooded, and the Doce River polluted up and down its length.
“The Samarco Fundão dam failure in 2015 was a terrible tragedy,” BHP chief Mike Henry said last week.
“It should never have happened and must never be forgotten.”
But if the Samarco disaster didn’t sufficiently raise the risks associated with tailings dams, the collapse at Brumadinho in early 2019, which killed 270 people, certainly did.
The two events formed a robust launchpad for change, and provided the impetus for the rollout of new standards and practices. But what, exactly, do those standards entail? And given the prevalence of tailings facilities around the world, how might the new guidelines affect the market more broadly?
A global problem
Used to store waste rock and other materials left over after processing, there are thought to be thousands of tailings dams at mine sites all over the world. They may consist of solid or liquid waste, and some contain elements that are toxic, such as arsenic and mercury.
According to a study published in Engineering Geology in 2022, a total of 257 tailings dam failures have been recorded since 1915, accounting for 2,650 fatalities and the release of 250 million cubic metres of contaminated waste into the environment. Notably, almost half of that waste — roughly 115 million cubic metres — has been released since 2000.
“The advances in mining technology over the past 100 years have made it economically feasible to mine lower grades of ore and to increase the excavated volumes,” the study said.
“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.”
This threat, the study added, is further complicated by the increased severity and frequency of major weather events due to climate change. Heavy rainfall is estimated to have triggered 25% of tailings dam failures globally, and 35% of collapses across Europe.
Embracing reform
It’s perhaps unsurprising, particularly in the aftermath of the Samarco and Brumadinho disasters, that conversations about addressing the innate risks of tailings dams have emerged.
In late 2019, the International Council on Mining & Metals (ICMM), the UN Environment Program (UNEP), and the Principles for Responsible Investment (PRI) convened a panel of experts and tasked them with conducting a global tailings review.
The result was the Global Industry Standard on Tailings Management, which, above all, “makes clear that extreme consequences to people and the environment from catastrophic tailings facility failures are unacceptable”.
“The catastrophic dam collapse at Vale’s Corrego de Feijao mine in Brumadinho was a human and environmental tragedy that demanded decisive and appropriate action to enhance the safety and strengthen the governance of tailings facilities across the globe,” Bruno Oberle, Chair of the Global Tailings Review, said in 2020.
“I am particularly pleased to deliver a document which reflects and addresses the complexity and multi-disciplinary nature of sound tailings management.
“It has been a privilege to lead this work and I now call on all mining companies, governments and investors to use the Standard and to continue to work together to improve the safety of tailings facilities globally.”
Oberle added that he hoped the Standard would be supported by an independent body, which could maintain its quality and further strengthen it over time.
The risk of ‘upstream’ tailings
One of the challenges faced by the new Global Industry Standard on Tailings Management is the unfortunate fact that not all tailings facilities are equal. Indeed, a key feature of both the Samarco and Brumadinho incidents was that they occurred in mountainous regions, where space for tailings facilities is limited.
This — as Bruce Adkins, a partner and head of Energy & Resources at Australian law firm Johnson Winter Slattery, explained in a recent article — required the construction of a certain type of structure, known as an ‘upstream’ tailings dam.
“A feature of this type of facility is that a wall or bund of earth and rock is constructed, and then a layer of tailings is placed behind (i.e. upstream of) the wall,” Adkins wrote.
“When the available space behind the wall has been filled, then another wall is built on top of the first layer, and a second layer of tailings is then deposited on top of the first layer. This process can be repeated as layer upon layer of tailings are deposited, one on top of another.”
It took a number of years, but researchers from ETH Zurich — a public research university in Switzerland — were able to outline the mechanism by which the Brumadinho incident occurred. In a study published in January this year, they explained how the catastrophe was driven solely by topographical ‘creep’ under a practically constant load, and that the disaster required no external trigger, such as heavy rainfall.
“This probably explains why there was no obvious deformation identified prior (to) the collapse,” the researchers wrote.
As a result, some countries, such as Brazil, Peru, and Chile, have outlawed the use of upstream tailings dams.
A durable solution or a new set of challenges?
While the new Standard has been welcomed as a necessary move, there is some speculation it could unfurl a fresh set of challenges, particularly in regions where upstream tailings dams had previously been deployed.
In order for the historical failings not to occur again, it’s likely that safer and more stable tailings facilities will cost more to build. Tighter controls on the placement of tailings facilities could also impose new limits on production levels, not to mention the broader challenges that may come later.
“The new standards have the potential to impact future investment in those parts of the world with challenging mining topographies, because the past approach to tailings management is no longer acceptable and new solutions will have to be implemented,” Adkins tells Mining.com.au.
“Where acceptable alternative solutions are available, they might be more expensive, and this could potentially impact on the viability of some projects. It is also possible that, in some locations, viable technical solutions for large scale tailings management might simply not be available.”
In a world gripped by the need for critical minerals to facilitate the ongoing global decarbonisation effort, this could be seen in some circles as troubling news.
Will companies adhere to the new Standard?
Nevertheless, the prevailing consensus seems to be that mining companies will do their bit to abide by the new Standard — if not because of the exposure to legal consequences, then perhaps for the potential reputational damage.
“Based on feedback from a contact of mine, I understand that (the Standard) is increasingly being accepted as the global benchmark to meet for tailings storage facilities around the world, and not just by the ICMM members who have formally committed to it,” Adkins explains to Mining.com.au.
He also notes that the Standard is being used to influence developments across a variety of national industries, such as Canada’s ‘Towards Sustainable Mining’ campaign, which aims to promote responsible mining practices, in particular the proper management of tailings facilities.
“This should hopefully lead to fewer dam failures in the future. At the same time, the mining industry is developing new ways of managing tailings that should result in safer tailings dams.”
One example Adkins points to is Anglo American’s (LSE:AAL) Hydraulic Dewatered Stacking (HDS) technology, which involves the concept of ‘desaturated’ — as opposed to wet — tailings storage.
“By dewatering the tailings and eliminating the surface pond, HDS improves the stability and safety of tailings storage, a key element of the Global Industry Standard on Tailings Management,” the London-based miner says.
“Meanwhile, in the event an HDS facility does fail, the lower interstitial water content and surface pond volume reduces the potential for flow, and thus the potential area of inundation. The dewatered tailings simply do not flow well, making the large-scale mudslides associated with previous tailings dam failures a thing of the past.”
Indeed, the new Global Industry Standard on Tailings Management is undeniably a necessary and important development. But change often requires support. For the new guidelines to deliver a net-positive impact on the state of global mining, governments and investors — particularly in emerging markets like South America and Asia — may need to steel themselves for a few short-term hurdles.
Write to Oliver Gray at Mining.com.au
Images: iStock, Communications Earth & Environment
