10 October 2010
Further insights into the failure mode of the Ajkai Timfoldgyar (Kolontar) tailings dam
Posted by Dave Petley
Thanks once again to Peter Diehl, the causes of failure of the Ajkai Timfoldgyar / Kolontar tailings dam are becoming clearer, and appear to support initial suspicions. There is an excellent gallery of images here, of which this is the most interesting in this context:
This is the damaged (cracked) section of the north side of the dam. Zooming into the cracks on the top of the dam shows this:
The pipeline running across the top of the dam is clear. Note that where it crosses the main (left side) crack the pipeline has been detached from the supports, which have moved forwards and downwards. A little further to the right the pipe has ruptured, and tailings have spilt across the dam surface. Thus, it is clear that the dam has moved forward and subsided at this location, which further supports (though does not confirm) the suggestion that the dam collapse was associated with failure of its foundations.
Interestingly, some suggestions are also emerging that this section of the dam had been leaking ahead of the collapse. WWF has an aerial image taken in June this June of the dam that appears to show a small leak:
However, this should be treated with some caution as there may be other explanations for this apparent spill of tailings on the downstream side of the dam. Finally, there is a gallery of image here that shows the state of the dam in 2005. These two give a pretty good idea of the general state of affairs at the dam:
Comparing a different WWF image (http://assets.panda.org/downloads/interspect_bako_gabor2.jpg) to an earlier image after the collapse (http://derstandard.at/1285200400578/Ansichtssache-Luftaufnahmen-des-Katastrophengebiets?_slideNumber=2&_seite=) it is clear that the crack halfway along this wall coincideds with the supposed WWF leak. (note the silver trees across from crack/leak)The speculated suggestion being that a leaking fault here caused movement on the foundations of the entire section of wall from the crack to the corner which, being a weak point, then resulted in the full breach.Its also interesting that the top surface of this wall has either had its grassed removed or additional material placed on top since June this year showing that work has taken place on this wall recently.
Is there any dimensional data available for the dam? I can't tell enough to "scale off" the dimensions – but if you had the diameter of the pipeline, it might be possible to get an estimate.It's an axiom that "the pressure on the dam is only proportional to the height of the water behind the dam" but in this case, it's not water. The pressure would be higher than for a water dam, because the fluid is heavier (denser), and actually the pressure is proportional to the density too, not just the height.
Functionally, this containment is a tank. For a tank, you need a "secondary containment." So really, there should be a second (empty) berm downstream of the primary containment, in case the wall of the primary containment ruptures.But, one often sees sumps/berms/containments/impoundments that functionally are tanks, but no secondary containment. Ironically, they are sometimes located right next to steel tanks which have berms around them.This is true even in California, where I live. CA is thought to have "strict" regulations, but I am aware of several impoundments (smaller than Kolotar) which do not have any secondary containment downstream. On the east side of the San Joaquin Valley, there are a number of these sumps that could drain rather directly into creeks that go through towns.
Note; this is not 'tailings', but red mud resulting from the Bayer process of producing alumina from bauxite ore.
Hello, I’d like permission to use the first photo in your article (cracked section of the north side of the dam) in an online course called the Tailings Manager Academy, developed by Glencore. Video link summarizing the course his here: https://www.youtube.com/watch?v=ZO22UG3g06g&t=1s
We would use the photo to show an example of a crack in a tailings dam.
Please let me know how to proceed with obtaining permissions.