On 25 January, near Brumadinho in Brazil, Dam 1 at the Córrego de Feijão mine owned by Brazilian iron ore giant Vale S.A. collapsed, causing a toxic mudslide that has killed over 165 people, and left 147 more people still missing. Many of the deceased were Vale workers dining in the company’s cafeteria at the time of the collapse. The cafeteria was swept away in the mudslide and destroyed, along with many other buildings, houses and hotels. The Rio Paraopeba has been polluted – but the full extent of the environmental damage is not yet known and there are fears that the waste may enter the much larger Rio São Fransisco opening up the possibility of environmental damage across the five Brazilian states through which it runs.

The Brumadinho tragedy comes only three years after the November 2015 collapse of the Fundão dam in Mariana, 120km from Brumadinho. The collapse of that dam, operated by Samarco, a joint venture between Vale and BHP Billiton, unleashed 60 million cubic metres of toxic iron ore waste, killing 19 people, flattening the town of Bento Rodrigues and polluting the length of the Rio Doce river from Mariana in Minas Gerais to the Atlantic coast in Espirito Santo 600km away.

Warning signs that went unheeded

What makes these two disasters all the more tragic is that the companies were aware of the risk of these dams collapsing. The Guardian reported last year that internal Samarco documents show that six months prior to the collapse, the company carried out a worst-case assessment of the dam and predicted significant impact to the environment and up to $3.4bn damage in the event of a collapse.

An internal Vale document from October 2018 obtained by Reuters reportedly shows that the Córrego de Feijão dam was two times more likely to fail than the maximum risk level allowed under internal Vale guidelines. The dam was nevertheless certified as stable in September 2018 by German company Tüv Süd. At the time of writing, eight employees or executives from Vale and four from Tüv Süd have been arrested in connection with the dam collapse. Vale has lost a quarter of its market value since 25 January; that is, nearly $19bn.

Upstream dams are most likely to fail

What makes these tailings dams so problematic? Tailings dams are used to contain the thick muddy residue that is a byproduct of ore mining. In the case of Córrego de Feijão, Dam 1 was just one in a series of dams constructed upstream of the original dyke to hold ever increasing waste product from the mining operations, which rendered it more likely to fail.

In earthquake-prone Chile and Peru, upstream tailings dams have been banned. The walls of upstream tailings dams are generally constructed from mining slurry piled into embankments, rather than using a separate surface retaining structure to impound the tailings as is seen in conventional dams. This form of dam is especially vulnerable to a process called ‘liquefaction’, whereby the more solid waste material forming the embankments suddenly loses strength (often due to partial saturation by the liquid materials it is intended to contain). Collapses by liquefaction are sudden and catastrophic: the embankment disappears, releasing a surge of liquid waste downhill devastating everything in its path. Liquefaction was found to have caused the Samarco disaster and is believed to be the most likely cause of the collapse at Brumadinho.

Brazil is particularly at risk

The New York Times has reported Brazilian government figures showing that there are 88 upstream mining dams in Brazil built in the same way as the dam in Brumadinho, and all but four of the dams have been rated by the government with the same or worse safety rating as the Brumadinho dam.

What gives greater cause for concern is that at least 28 of these upstream dams are situated directly uphill from cities or towns, meaning that over 100,000 people are living in areas where a dam has a high risk of failing.

The state of Minas Gerais produces over half Brazil’s mining output, and, as such, the mining industry holds significant political sway. Mining companies are allowed to self-regulate – they hire inspectors to conduct safety checks based on reports provided by the companies themselves. In December 2018, the State Council on Mining Regulations held an extraordinary meeting to approve Vale’s proposal to expand operations at Córrego de Feijão. None of this bodes well for those living near unsafe tailings dams.

Preventing another tragedy

According to World Mine Tailings Failures, a database of accidents caused by mine tailings structures, between 2008 and 2017 there were 13 “very serious failures” around the world. Absent any significant change in industry practice or laws and regulations, another 19 very serious failures are predicted to occur between 2018 and 2027.

The 2018 Responsible Mining Index published by the Dutch-based Responsible Mining Foundation (RMF) found that over half of the 30 mining companies assessed were not adequately able to track how they were assessing and addressing the risks of dam failure and seepage. Moreover, none of these companies were publicly disclosing the measures that they had taken to address risks relating to tailings dams.

It is clear that the next tragedy is around the corner if mining companies do not adequately address these risks and rapidly change their practices. In Brazil, the need for companies and government to work together to prevent the next disaster is imperative.

After Samarco, Vale announced plans to decommission its 19 upstream dams. By the time of the Brumadinho disaster, 9 had been decommissioned, but the Córrego de Feijão dam had been inactive since 2016 pending authorization from the relevant authorities. Since Brumadinho, Vale has stated that it will accelerate the decommissioning process for the remaining 10 upstream dams.

It may not be enough. Two weeks after the collapse in Brumadinho, residents in two mining cities were ordered to evacuate their homes at dawn. In Barão de Cocais, 500 people living near the Upper South dam of the Gongo Soco mine, which also belongs to Vale, were ordered to leave their homes. In Itatiaiuçu, 200 residents also received evacuation orders because of the risk to the Serra Azul mine dam, which belongs to the steelmaker ArcelorMittal. Like the Córrego de Feijão dam, the Serra Azul tailings dam is upstream and has been inactive since October 2012.

Both companies have said the evacuations were preventive measures, after consultants refused to attest to the stability of the dams. Such is the unfortunate new reality in Brazil for the residents of villages lying downstream from tailings dams, who live in constant fear of the next collapse.