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How big is the mining sector tailings dam problem?

Globally there are thought to be up to 18,000 “tailings” dams – but no one knows for sure.

The homepage of the website World Mine Tailings Failures shows in full-screen-terror the video footage of the dam bursting at Vale’s Córrego do Feijão mine near the city of Brumadinho, killing a confirmed 165 people with over 150 more presumed dead.
A previously tranquil hillside collapses. Employees and families eating in a canteen are wiped out by a deadly wave of toxic iron ore sludge.
The tragedy is compounded by the data backstory on the same page; depressingly familiar historical numbers. The problem has been worsening over the decades since ICOLD/UNEP began collecting statistics prompted by an increasing frequency of high-consequence tailings failure events post-1990.
But just how big is the problem of mine tailings?
In the same region of Minas Gerais as Brumadinho, Vale alone has built 105 of these huge pits to hold mining waste. Globally there are thought to be up to 18,000 “tailings” dams – but no one knows for sure.
And therein lies a big part of the problem. What we are observing is not an issue specific to Vale or Brazil, but a systemic issue for the whole industry. There’s little transparency on how companies are managing social and environmental risks, particularly at a site-specific level, and no comprehensive public or government database of where these tailings dams are – let alone whether they’re at risk of failing.Even the International Council on Mining and Metals (ICMM) – which brings together 27 mining and metals companies and over 30 national and regional associations – doesn’t have such a database for its member firms.
It’s not that so-called “upstream” dams – as in the Samarco and Brumadinho disasters – should be banned outright.
Geotechnical spokespeople from organisations such as the Australian National Committee on Large Dams (ANCOLD) maintain that they have the lowest initial cost and are the most popular in low-risk seismic areas and can be stable if properly designed within existing guidelines. Plus, how do you ban something that already exists to such a huge scale? Hazard classifications around tailings dams already exist and are fairly consistent (in principle at least) across the globe. But Lindsay Newland Bowker, Executive Director at World Mine Tailings Failures, says large gaps in practice arise not from evil or malpractice, but uncertainties that are inherent to the mining industry: “Once a mine has a permit and is in production, there’s nothing to stop it increasing capacity if the price turns favourable for the commodity. They’ll rush to produce more and grab deposition space for tailings.” Consequently, dams are often built up over time to hold more and more tailings. Such was the case in Brumadinho where the dam

reached heights of 87m, exceeding best practice recommendations by 37m. Its permit had been intact since Vale acquired the facility in 2001. Newland Bowker says: “That connection [of planning for dam capacity over time] does not exist in the process anywhere along the line – not with investors, not at the regulatory level. What happens to the tailings gets lost in the crunch for maximum production.” In addition, Over the last three decades, there’s been a shift within the mining industry to a preference for near-surface, lower grade ore – which produces much more in tailings.
In short, there’s no regime in place to try to counteract the burgeoning risk or the eventual clean-up.
The Córrego do Feijão dam had been inactive for about three years, and Vale said it was in the process of being decommissioned, i.e. being declassified as a dam and reintegrated into the environment.Just how many inactive dams have been decommissioned is uncertain; little surprise, given the lack of even basic aggregate information. But Bowker says the high costs associated with land rehabilitation have caused the industry to avoid dam closure.
Vale has estimated that investments of around R$5bn ($1.3bn) will be necessary to decommission its 10 upstream dams. But Dr Steven H Emerman, owner of Utah-based Malach Consulting, which specialises in evaluating the environmental impacts of mining on behalf of mining companies, says that Vale is grossly underestimating the cost of decommissioning, and that a more realistic estimate would be $1bn per tailings dam. “On this basis, Vale’s statement that they have set aside $1bn to decommission ten dams doesn’t go very far,” he says. “It sounds as if they would need more like $10bn at a minimum.”
Indeed, as ICMM says on its website: “Once a mineral deposit is exhausted, mining companies have a responsibility to work towards land rehabilitation. [This should] not be an afterthought only starting towards the end of an operation, but should instead be a continual activity.”

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