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WORLDWATCH DAMS Many commentators argue that, as the cheapest and least stable form of tailings dam, upstream technology is inherently problematic and should be scrapped altogether. Some engineers favour the downstream dam, in which successive loads of tailings are deposited downstream of the initial wall rather than upstream. Dr Barry Wills, senior partner of the journal Minerals Engineering International writes that: ‘Downstream dam building is the only method that permits design and construction of tailings dams to acceptable engineering standards.’ However, Durve disagrees and says that both types of structure can be stable or unstable depending on how they are constructed. ‘Instability will arise in either case if sufficient consideration is not paid to seepage and the position of the phreatic surface,’ he says. What’s essential, as he noted in 1985, is constant monitoring of the water pressure in the wall – something he claims is cheap and easy to do using water pressure monitors. In the aftermath of the disaster, Vale stated that there was no evidence of an imminent risk of collapse at Brumadinho and that it consistently monitored water pressure. But a string of media reports (along with the arrest of eight Vale employees) indicated that the company and one of its contractors knew of significant issues. On 11 February, Reuters stated that it had seen an internal Vale report dated October 2018 which classified the dam at Brumadinho as being two times more likely to fail than the maximum level of risk tolerated under internal guidelines. According to the Guardian, a September 2018 report by the German certifications contractor TÜV SÜD concluded that the Brumadinho dam was stable but highlighted drainage problems and recommended installing new water pressure monitors. Vale stated that ‘workers were fitting the new monitors on the day the dam burst’. Further reporting by the Wall Street Journal in February, based on police reports, court documents and arrest More tailings dam failures are predicted which will could to more loss of life and property 8 • Geographical

warrants, revealed that inspectors at TÜV SÜD had known of dangerous conditions for months but certified that the dam was safe anyway, ‘expressing worry about losing contracts with Vale’. Brazil has now ruled that all upstream dams (there are 88 according to the National Mine Association) must be decommissioned or removed by August 2021. In doing so it joins Chile and Peru as the only countries to ban this type of structure. It’s a move unlikely to provide much comfort to Andréa Zhouri, a professor in the Department of Anthropology and Archaeology at the Universidade Federal de Minas Gerais. Speaking at the British Academy on 23 February, Zhouri emphasised the importance of putting the Brumadinho disaster in the wider context of increasingly worrying environmental deregulation in Brazil. ‘The social and environmental governance package that was established between the 1980s and 1990s has undergone a gradual process of erosion,’ she said. ‘Shortly after the collapse of the Samarco dam in 2015, MPs from the state of Minas Gerais did not hesitate to approve a decree that reduces requirements for environmental assessment in order to speed up mining permits.’ All the evidence suggests that this unravelling will now accelerate under Brazilian president Jair Bolsonaro. For Zhouri this is linked to a wider problem in Brazil known-as ‘revolving doors’, which she says refers to a tight link between state actors and commercial mining companies. She points to a recent report by Brazilian newspaper O Tempo which claims that of the 130 federal and state deputies elected in Minas Gerais in 2014 (the last year private donations to political campaigns were allowed), 102 were funded by mining-related companies. When it comes to the specifics of upstream tailings dams, Zhouri is firmly on the side of those who view them as dangerous, referring to them as ‘cheap, old technology’. While there are no official figures for the total number of upstream dams worldwide, many large mining companies still utilise them (Anglo American, one of the world’s largest miners, has 32 upstream dams in its portfolio, while the RioTinto Group, the world’s second largest, has 21). What’s more, as Durve makes clear, it is not only upstream technology that can fail, especially if monitoring is weak. There are an estimated 3,500 tailings dams worldwide and WMTF predicts that without major changes to law and regulation, as well as new technology, 19 ‘very serious failures’ of tailings dam will occur between 2018 and 2027. While the engineering specifics of these structures may be complex, there is one simple thing most experts agree on – without sufficient monitoring and expertise, many more tailings dams are likely to collapse. l TAILINGS DAM INCIDENTS by Benjamin Hennig n The International Commission on Large Dams is an institution that maintains the World Register of Dams which contains more than 58,000 entries. Such sources suggest there may be approximately 3,500 tailings dams worldwide. Information about dam failures (tailings and other) is even more fragmented. According to UNEP statistics, the overall numbers of reported incidents has been rising steadily into the 1970s. A 2015 study also suggests that the number of tailings dam failures keeps increasing into the most recent decades. More specific comparisons of the various studies need to be treated with caution, so that the global picture presented in this cartogram relies on one of the attempts to address this topic from an academic perspective. The cartogram shows each country proportional to the number of tailing dam incidents that were recorded in a database compiled from detailed search and re-evaluation of the known historical cases of tailings dam failure published in the Journal of Hazardous Materials. The 147 cases of tailings dam disasters until 2008 were combined with records of the past ten years to complete this worldwide picture. This provides an insight into the spatial distribution of where these large structures constitute a significant environmental hazard but can also have an equally high negative socioeconomic impact (and not least also affect human lives and livelihoods). Benjamin Hennig (@geoviews) is Associate Professor of Geography at the University of Iceland and Honorary Research Associate in the School of Geography and the Environment at the University of Oxford. He is also involved in the Worldmapper project (Worldmapper.org). April 2019 • 9

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WORLDWATCH DAMS

Many commentators argue that, as the cheapest and least stable form of tailings dam, upstream technology is inherently problematic and should be scrapped altogether. Some engineers favour the downstream dam, in which successive loads of tailings are deposited downstream of the initial wall rather than upstream. Dr Barry Wills, senior partner of the journal Minerals Engineering International writes that: ‘Downstream dam building is the only method that permits design and construction of tailings dams to acceptable engineering standards.’

However, Durve disagrees and says that both types of structure can be stable or unstable depending on how they are constructed. ‘Instability will arise in either case if sufficient consideration is not paid to seepage and the position of the phreatic surface,’ he says. What’s essential, as he noted in 1985, is constant monitoring of the water pressure in the wall – something he claims is cheap and easy to do using water pressure monitors.

In the aftermath of the disaster, Vale stated that there was no evidence of an imminent risk of collapse at Brumadinho and that it consistently monitored water pressure. But a string of media reports (along with the arrest of eight Vale employees) indicated that the company and one of its contractors knew of significant issues. On 11

February, Reuters stated that it had seen an internal Vale report dated October 2018 which classified the dam at Brumadinho as being two times more likely to fail than the maximum level of risk tolerated under internal guidelines. According to the Guardian, a September 2018 report by the German certifications contractor TÜV SÜD concluded that the Brumadinho dam was stable but highlighted drainage problems and recommended installing new water pressure monitors. Vale stated that ‘workers were fitting the new monitors on the day the dam burst’.

Further reporting by the Wall Street Journal in February, based on police reports, court documents and arrest

More tailings dam failures are predicted which will could to more loss of life and property

8 • Geographical

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