Second Massive Mine Tailings Dam Collapse in 3 Years

Brazil’s Worst Environmental Disaster and over 300 Dead

For the second time in three years, a mine tailings dam in Brazil holding millions of tons of mud and sludge has collapsed cascading its toxic contents into local towns, killing scores of people and devastating the local environment. The Waihi and nearby Waitekauri mining companies say their tailings dam are safe but might they too collapse in a large earthquake?

The previous collapse in 2015 of a tailings dam owned by the same mining company was then described as Brazil’s worst environmental disaster.  But now that has been topped by this latest catastrophic tailings dam collapse, and over 300 people are feared dead.

The previous dam collapse was triggered a very small earthquake but slack mining company management was likely also to blame.

If you take a look at this photo of yesterday’s tailings dam collapse in Brazil you can see the remains of the grassy slopes of the dam on each side, but with the rest of the dam structure completely destroyed. 

brasil dam collapse jan 2019

Remind you of somewhere?  Those lovely grass slopes of the Waihi tailings dam perhaps – so picturesque with cows grazing on them?  What could possibly go wrong?

Slopes of Waihi Tailings Dam

Whenever these mine dam collapses happen – and they happen with terrifying regularity – we always hear the cry from our local mining industry that nothing like that could ever occur in New Zealand.  We have much stronger regulation of dam structures and our engineers are “better”.  Which of course conveniently forgets that the tailings dam at the Waitekauri gold mine near Waihi came very close to collapsing in the late 1990s. 

The two Waihi dams have been built on the assumption that the area is of low/moderate earthquake risk.  But recent GNS Science studies of the nearby Kerepehi fault suggests the area is much more prone to more severe and frequent earthquakes than previously thought.workshop-map-ngatea-segment-6-7mw

Or, a “mega thrust” massive earthquake in the Hikurangi trench off the east coast of the North Island could very easily trigger a dam collapse at Waihi.  Not only would we have massive damage to property from the earthquake and possible tsunami, but a tailings dam collapse at Waihi would cause New Zealand’s greatest ever environmental disaster. Millions of tonnes of toxic mine sludge would be swept down the Ohinemuri river through the Karagahake gorge and out into the Firth of Thames and Hauraki Gulf.

Which all goes to show that we should never have allowed these tailings dams to be built in the first place, and we should certainly not be making them taller and even more vulnerable to collapse by adding more tailings from the Waihi mine or any other proposed new mines.