27 January 2019
The scale of the tailings dam collapse at Feijão mine in Brumadinho, Brazil
The disastrous and tragic tailings dam collapse at Feijão mine in Brumadinho, Brazil is already fading from the attention of the international media, despite about 300 fatalities and a global-scale scandal. I will come back to the latter point below, but it is worth first examining the scale of the collapse at Feijão mine. The tailings dam that collapsed so dramatically is the one shown below, from Google Earth:-
This view appears to support the reports that the tailings pond was not in use at the time of the collapse – the vegetated pond shown above would seem to imply that tipping had ceased. As an aside, the second structure that is now considered to be at risk is shown in the centre left of the image.
The scale of the collapse is breathtaking. The image below was tweeted by John O’Leary:-
This is clearly a complete collapse of the retaining structure, which was tall and steep, with most of the tailings having been mobilised into a high velocity flow. Note the complete destruction of the various buildings in the Google Earth image above, presumably accounting for the large numbers of fatalities.
The tweet by John O’Leary also shows the second dam that is considered to have a high potential for failure. This dam has been badly damaged, and the risk appears to be high:-
There is a presentation online showing the various tailings structures owned by Vale in this area, published in 2016. The tailings dam at Feijão mine in Brumadinho that collapsed is Slide 44 in the presentation:-
This assessment appears to indicate that the potential losses were assessed as being high should the dam collapse, but that the potential for this to occur was considered to be low. Clearly that was not correct, even though the assessment appears to post-date Samarco.
The presentation indicates that the dam was 87 m high, impounding almost 13 million cubic metres of waste.
But this event is indicative of a much larger global issue. The impacts of tailings dam collapses on people and the environment can be catastrophic, as this event illustrates. As such it must be incumbent upon operators to ensure that collapses cannot and do not occur under any foreseeable circumstances. But we repeatedly experience tailings dam failures – recent examples include Cadia in Australia (2018), Mishor Rotem in Israel (2017), Henan Xiangjiang Wanji in China (2016), Samarco in Brazil (2015), Mount Polley in Canada (2014), Xichuan Minjiang in China (2011) and Kolontor in Hungary (2010), amongst many, many others. No other area of geotechnical engineering would tolerate a failure rate like this, and no other area of geotechnical area would be allowed to operate in the area of the risk / consequence matrix occupied by tailings dams. That this situation is allowed to continue is an absolute disgrace.
And Vale themselves have had two major tailings dam failures in Brazil in four years. I do not need to comment further.
Thanks to reader Raphael, who found the Vale presentation on the risk associated with their tailings dams.