4 October 2019
Nosso Senhora do Livramento: another tailings dam failure in Brazil
Posted by Dave Petley
Nosso Senhora do Livramento: another tailings dam failure in Brazil
On 1st October, another significant tailings dam failure occurred in Brazil, this time at Nosso Senhora do Livramento in Mato Grosso. Fortunately, in this case the scale of the failure, whilst not being trivial by any means, was not equivalent to the other two recent events in Brazil. However, two people have been injured.
The best image to provide an overview of this failure is, I think, this one from Isso E Noticia:-
The tailings dam failure at Nosso Senhora do Livramento in Brazil. Image via Isso E Noticia.
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So, it appears that one of the walls of the tailings dam has collapsed. The location is -15.958, -56.479 if you want to take a look. This is the Google Earth image of the site:-
Google Earth image of the site of the tailings dam failure at Nosso Senhora do Livramento in Brazil.
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This image was collected in June 2018. Planet Labs captured an image of the site on 1st October 2019, the day of the collapse:-
Planet Labs image of the site of the tailings dam failure at Nosso Senhora do Livramento in Brazil. Planet Labs PlanetScope image collected 1st October 2019, copyright Planet Labs, used with permission.
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It is not clear as to whether the failure was on-going when the image was captured, but at that point the extent of the inundation from the failure was quite contained. It is worth comparing the above image with the one below, which is the same site imaged on 7th July:-
Planet Labs image of the site of the tailings dam failure at Nosso Senhora do Livramento in Brazil. Planet Labs PlanetScope image collected 7th July 2019, copyright Planet Labs, used with permission.
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I think that there is clear evidence that there was considerable work going on at this site, including clearing of the area that was ultimately inundated. The images also suggest that the height of tailings dam has probably been increased over the last 15 months or so – this is a Planet Labs image from July 2018, when the dam walls appear to be significantly lower:-
Planet Labs image of the site of the tailings dam failure at Nosso Senhora do Livramento in Brazil. Planet Labs PlanetScope image collected 25th July 2018, copyright Planet Labs, used with permission.
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The thickness of the tailings dam walls has clearly increased, and at least superficially this raising appears to have occurred via the upstream method (can anyone comment on this?)? This raising of the height of the tailings dam walls might also be evident in the photograph at the top of the page.
There’s a good article (in Portuguese) about the failure in Estadao Ssustenabilidade. This notes that this was a registered gold mine; that the tailings dam was inspected in September 2018 and found to be low risk and low potential damage; and that the structure was 15 m high with a storage volume of 580,000 m³.
Whilst this was a comparatively contained failure, it once again highlights the utterly unacceptable rate of tailings dam collapses.
Reference
Planet Team (2019). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
It’s truly tragic that this keeps happening. The engineering principles are well understood; all these failures are preventable.
It appears that it was a relatively recently constructed facility; the entire cell/impoundment that collapsed didn’t exist in 2013.
Based on the vegetation on the lower slopes and the fact the road didn’t move, it was indeed raised in the upstream direction. The slope looks to be 2H:1V or steeper, that’s very steep for an upstream raised dam.
Also worth noting is that the failure occurred at the section of the dam where the supernatent pond is, which isn’t surprising. The pond increases the phreatic surface in that area, and upstream tailings dams typically rely on subaerial deposition to provide a strength increase in the tailings for the foundation of the subsequent raise.
What can we say a g a i n… monitor, monitoring, monitor, local data collection and dissemination… responsibility…..?
I would not call this upstream fill as the June, 2018 GE image shows the slope of the wall has increased significantly since June, 2017. The 2018 image in zoom shows clearly more than a dozen dump-loads placed atop the wall to the East of the section that failed.
They have too small a foot print so they had to go up to keep mining; the recipe for failure. The 2017 image also appears to show a section of wall that would fail to be differently colored, as if a small over-top event may have occurred. Curiously, there are 3 structures in the road directly below this section of wall. They are visible in 2018 too.
The inundation limit in the aerial photo is not as extensive as in the PlanetLabs imagery, indicating continued flow. Someone got into the air quickly. The intervening wall in the largest reservoir appears to have contained what could have been a much larger flood of tailings.
En climas de fuerte precipitaciones, las construcciones de Presas deben ser de otros métodos, más inversiones en las Relaveras, los métodos convencionales, Espesados o Filtrados son vulnerables al clima adverso.
Los relaves en pasta con pequeñas dosis de cemento y Zeolitas sintéticas es la tecnología del futuro para Relaves dispuestos en estos climas adversos.
Esperemos que las investigaciones sean transparentes y compartidas.
[Google translate: In climates with heavy rainfall, Dam constructions must be of other methods, more investments in the Tailings, conventional methods, Thickened or Filtered are vulnerable to adverse weather.
Paste tailings with small doses of cement and synthetic Zeolites is the technology of the future for tailings arranged in these adverse climates.
Hopefully the investigations are transparent and shared. D]