3 April 2020
Finding a consensus view on the Luming Mine tailings accident
Many thanks to all of you who have contacted me about the Luming Mine tailings accident over the last few days, and for the comments about the accident posted to this site too (I’m not sure why some of the comments are not showing – this appears to be a glitch with WordPress). I appreciate the hard work that many of you have put into this problem.
I thought it would be useful to summarise the consensus view of the accident, which makes use of the amazing knowledge that lies in the wider community. I shall make reference to the Planet Labs image again:-
The strong consensus is that the origin of the Luning Mine tailings accident is the depression that has formed in the centre east side the above image. The tension cracks and the formation of a new erosional gully in this area indicate that there has been a substantial loss of material. Some have suggested that there might have been flow over the southern abutment of the southern starter dam. I have also wondered about this, but I think the similarity of that area to the northern abutment of the northern starter dam makes this unlikely. I would welcome thoughts.
There is an image of the depression online on another Chinese news website – it describes this area as “No. 4 overflow shaft”.
The discharge of the tailings appears to be the area of the blue hut just to west of the foot of the abutment of the southern starter dam, which line us with the failure point in the tailings pond. After a trawl of Chinese news websites I found the following image, which was posted to a website called fjsuchi. I don’t know much about this image as my PC will not allow me to access the site itself due to a security warning, and so I won’t post a link. But it appears to show the likely discharge point of the tailings and polluted water at the foot of the dam:-
That then raises the question of what was happening at the point of failure in the tailings pond. Two hypotheses have been proposed in the comments. One is that this was a decant tower, a structure constructed to dewater the tailings. In a good primer on tailings facilities construction it is noted that:-
Inadequate decant design has caused major dam failures. Many older dams used decant towers with discharge lines running through the base of the dam to a downstream pump-house. Failures of such structures were common due to the high pressures exerted on the pipelines, leading to uncontrolled losses of fluids and tailings downstream.
If this was indeed a decant facility then could it be argued that this relatively new tailings facility is using out of date technology? That might be reinforced by the fact that the tailings dam approach to construction is clearly the upstream method.
The alternative possibility is that this is a reclaim system. In this case the water is extracted from the tailings and reused in the mill rather than being discharged into the river.
The Google Earth image of the failure area, taken in 2018, shows a structure:-
I invite those with expertise to comment on what this structure might be. In his comment yesterday, James Turner notes that:-
You can use Google Earth Pro Windows’ satellite image history you can follow the starter dam construction as well as the standpipe boring.
If you place pins at drill site pads in several locations they track standpipe discharge points in later photo at the shoreline, opposite the portal outlet by the blue pump station. Start with the Aug and Oct 2013 images and there are a chain of drill sites working back East where the pond shore would later be. In one image you can see a drill frame. A Sept 28 2015 image shows standpipe locations along the now flooded shore. One of the standpipes that was at the shore but later drowned seems to be the leak source.
Take a look – the location is 47.346, 128.569. The key might be this Google Earth image from October 2013:-
This is the same site as in the previous image. There was clearly site preparation work at this location.
So, the question to those of you with expertise in this area (and there are many of you), what does the evidence from the apparent discharge point in the second image in this post, the structure in the third image and the site preparation in the fourth image indicate was happening at this site prior to failure?
And, of course, what does this tell us about the quality of tailings management leading up to the Luming Mine tailings accident?
Over to you.
Reference and acknowledgement
Planet Team (2020). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/
Thanks to all of you for your fantastic insight to this problem. It reminds me of the way that we solved the mystery of the 2012 Seti River rock avalanche in Nepal.