Health & safety
across the mining world – even if it doesn’t necessarily solve any of the underlying problems with tailings dams as a whole.
Dam control
From India to Peru, there are an estimated 3,500 tailings dams worldwide. This prevalence is easy to understand, especially if you know how much waste mining can spawn. Workers at a typical copper facility, for instance, might mine 270,000t of material each day – even if that results in a mere 1,750t of actual copper. All that excess has to go somewhere, and tailings dams offer an attractively flexible solution. That’s particularly true if operators opt for the ‘upstream’ approach, where the tailings themselves are used as a kind of self-fulfilling wall. Because these structures can always be raised – more tailings accommodate more tailings – upstream dams are alluringly cheap. But as Professor Stephen Grebby explains, upstream models are also dangerous. As the University of Nottingham academic puts it, “This type of dam is quite vulnerable to stability issues and is estimated to be associated with 75% of all dam failures.”
Top: MotionMonitor can accurately measure movement even in satellite images of rural areas.
Above: Researchers claimed that the system could have predicted the Brumadinho disaster in 2019.
3,500
Number of tailings dams worldwide in 2021.
The Economist 22
causes, from poor design to misadministration to the weather, the tailings themselves were undoubtedly fatal. After experts analysed the wreckage, they found that these artificial hillocks of water and mud had been unstable long before the summer rains had come. That is often the case elsewhere too. It was true, for instance, at Brumadinho in Brazil, where a landslide killed 270 people in 2019. Before it’s even been built, moreover, locals are already worried that a planned tailings dam in Indonesia will eventually collapse, drowning their village in muck. Given these structures are 100 times more likely to fail than water dams, their fears are probably justified. And though statistics are scarce – mines are frequently built in remote corners of less developed countries, and owners are reluctant to share bad news – one source counts 14 major accidents since 2018. In short, tailings dams are an environmental and humanitarian menace, even as they’ve become an accepted crutch for operators everywhere. Not that miners and their families are simply expected to twiddle their thumbs and expect the inevitable storm. Rather, operators have used sensors for years, typically embedded into a dam, to spot ground disturbances before they turn into full collapses. But if these platforms are far from useless, they also suffer from a number of technical and practical flaws – it’s small wonder why scientists have battled so hard for a solution. Instead of relying purely on ground sensors, they work to survey tailings from the sky, using satellite imagery to predict when and how tailings dams will fail. At its most sophisticated, this technology could have revolutionary consequences
Beyond investing in safer dams – for instance, ones with concrete barriers – mine operators have traditionally fought these vulnerabilities by checking tailings dams for structural faults. Apart from old- fashioned surveying, they’ve long relied on ground- based sensors. The idea is simple: the machines detect any movement in the dam, and engineers fix the issue before it causes a landslide. And as Dave Fox emphasises, this approach can provide “excellent data” if done properly. Unfortunately, the managing director at Geospatial Insight notes, this is not always true. If a mine is abandoned, for instance, vital sensors risk being forgotten. Maintenance is another issue – and even if they’re kept in action, sensors suffer from more basic flaws. “Although these techniques provide crucial information on the stability of dams,” says Grebby, “they only really provide discrete measurements at only several specific locations on the dam and tailings, which may make it difficult to spot signs of distress.” As the people of Brazil and Myanmar know only too well, “distress” can quickly lead to death and terror. That’s often shadowed by dire environmental consequences. The Brumadinho disaster, for instance, destroyed 125ha of forest. Another calamity, at the nearby Fundão dam, leaked around 50 million cubic metres of iron ore tailings. Despite being over 250 miles away, some of the sludge ultimately ended up in the Atlantic. To their credit, industry insiders are clearly not oblivious to these challenges. In an attempt to escape potentially unreliable ground sensors, scientists have adopted what’s known as ‘interferometric synthetic aperture radar’ (InSAR) technology. Put simply, this involves taking satellite photos of a tailings dam at different times, then
World Mining Frontiers /
www.nsenergybusiness.com
University of Nottingham
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