Mine dam collapse - Jagersfontein

SA has about 250 Tailings Facilities in the Global Tailings Consequence Classification Database published as part of the new Global Industry Standard on Tailings Management (the GISTM). Unfortunately, this does not include legacy tailings such as Jagersfontein and many junior miners. The lack of stewardship of these abandoned facilities is a high risk.

In terms of risk management of the abandoned tailings, and dumps, there are relatively cheap methods for

1. Site Characterisation using airborne / satellite hyperspectral data to gain insight into geotechnical and hydrogeological conditions and the general structure of the dam.

2. InSAR (Interferometric Synthetic Aperture Radar) satellite data for monitoring deformation. Lower resolution InSAR has been freely available since 2014. The investigation will most likely include an analysis of that data to access the deformations of the dam. It will likely find there were warning signs.

1 & 2 are low-hanging fruit and low-cost methods for risk management of abandoned structures and integrating these into the GISTM for stakeholder transparency and oversight.

3. The results from 1&2 above should be integrated into a Consequence (Exposure) Risk-Based rating which will then inform the level of effort required for each site with respect to remedial measures and surveillance.

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Not the first time.

en.wikipedia.org

Merriespruit tailings dam disaster - Wikipedia

en.wikipedia.org en.wikipedia.org

Separate investigations were carried out by the owner, operator, and the State.
A joint inquest/inquiry was run, with a judge appointed by the Minister of Justice. The State conducted investigations including looking at eyewitness accounts, weather and hydrological data, laboratory and in situ tailings testing, satellite imagery, and overtopping studies using a scale model. The mine and the contractor managing the tailings were found responsible for the disaster. The inquiry led to the introduction of a new Code of Practice for Mine Residue Deposits.[3]

The judge described the dam as a time bomb waiting to explode.[2]

The owner, operator and six of their employees were found guilty of negligence and heavy fines were imposed. It was discovered that economic pressure had led to a reduction in personnel related to the tailings dam, the metallurgical manager's direct management of the dam was reduced due to time constraints, and personnel had been promoted to positions for which they did not have adequate experience.[2]

The South African government appointed the Council for Scientific and Industrial Research to investigate, which confirmed the conclusions reached; as a result the 1995 Draft Code of Practice for the Design, Operation, and Closure of Tailings Dams was introduced.[2]
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dlk001 said:
SA has about 250 Tailings Facilities in the Global Tailings Consequence Classification Database published as part of the new Global Industry Standard on Tailings Management (the GISTM). Unfortunately, this does not include legacy tailings such as Jagersfontein and many junior miners. The lack of stewardship of these abandoned facilities is a high risk.

In terms of risk management of the abandoned tailings, and dumps, there are relatively cheap methods for

1. Site Characterisation using airborne / satellite hyperspectral data to gain insight into geotechnical and hydrogeological conditions and the general structure of the dam.

2. InSAR (Interferometric Synthetic Aperture Radar) satellite data for monitoring deformation. Lower resolution InSAR has been freely available since 2014. The investigation will most likely include an analysis of that data to access the deformations of the dam. It will likely find there were warning signs.

1 & 2 are low-hanging fruit and low-cost methods for risk management of abandoned structures and integrating these into the GISTM for stakeholder transparency and oversight.

3. The results from 1&2 above should be integrated into a Consequence (Exposure) Risk-Based rating which will then inform the level of effort required for each site with respect to remedial measures and surveillance.
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Interesting to see. The big Brazilian disaster showed little deformation until sudden collapse. It is all about porewater pressures imho. Not easy to monitor externally.
 
buka001 said:
Sooooo ... They took advantage of a gap in HSE regulation and now we have an accident. Colour me surprised.

Mmmm

Imagine we relaxed the regulations in the nuclear construction industry ...
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Well, in this case it was because the regulations were badly written and unclear.

Regulations should be fit for purpose. A PWR reactor has a completely different safety model to a passively cooled SMR, or the PBMR.
 
dlk001 said:
The purpose of the dam is to store slimes generated from the beneficiation process. The chemical quality of the slimes differs depending on the mineralogy of the rocks, mining method and beneficiation process. Some contain hazardous substances and others are non-hazardous.

Mines around the world are looking at more environmentally sustainable ways of slimes disposal (where possible) including backfilling the old pits which is what this operation intended to do. However, the common method of disposal of mining waste is waste rock dumps and tailings dams.
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As far as I can tell many Sa rock types that are diamond bearing can contain some pretty hardcore heavy metals, uranium etc. I’d be surprised if the rock formations from that mine are completely free of nasties?
 
Oldfut said:
Interesting to see. The big Brazilian disaster showed little deformation until sudden collapse. It is all about porewater pressures imho. Not easy to monitor externally.
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That is what they claimed but like I said, there are always warning signs as this paper revealed. 1663056744339.png

Here we present the Intermittent Small Baseline Subset (ISBAS) technique on satellite-based interferometric synthetic aperture radar (InSAR) data to assess the course of events. We find that parts of the dam wall and tailings were experiencing deformation not consistent with consolidation settlement preceding the collapse. Furthermore, we show that the timing of the dam collapse would have been foreseeable based on this observed precursory deformation. We conclude that satellite-based monitoring techniques may help mitigate similar catastrophes in the future.
 
airborne said:
As far as I can tell many Sa rock types that are diamond bearing can contain some pretty hardcore heavy metals, uranium etc. I’d be surprised if the rock formations from that mine are completely free of nasties?
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Uranium naturally occurs in Gold reefs but can occur in PGMs host rocks too.

You can read the following Impact Assessment Report if you are curious about environmental risks at Jagersfontein operation.

 
dlk001 said:
That is what they claimed but like I said, there are always warning signs as this paper revealed. View attachment 1381841

Here we present the Intermittent Small Baseline Subset (ISBAS) technique on satellite-based interferometric synthetic aperture radar (InSAR) data to assess the course of events. We find that parts of the dam wall and tailings were experiencing deformation not consistent with consolidation settlement preceding the collapse. Furthermore, we show that the timing of the dam collapse would have been foreseeable based on this observed precursory deformation. We conclude that satellite-based monitoring techniques may help mitigate similar catastrophes in the future.
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Hindsight is a great science but without reading the article "deformation not consistent with consolidation settlement" would require quite a bit of analysis to determine (I have looked at many slope failures etc). Also, the satellite images would have to be available and able to be analysed very quickly, almost in real time to prevent a disaster. PWP's on the other hand can be monitored remotely at short time intervals with borehole instrumentation and checked against design guidelines allowing quick action to be taken (but what sure?). If deformation was a good guide, inclinometers etc would be installed BUT these cannot be monitored remotely or continuously (or at least last I used them); you need to run the trolley. Finally, "techniques may help" is not too positive. Monitoring PWP's will help.
 
I see Gweezy is wasting the important peoples time while they have meetings with him and brief him on shyte that he doesn't understand.
 
Oldfut said:
Hindsight is a great science but without reading the article "deformation not consistent with consolidation settlement" would require quite a bit of analysis to determine (I have looked at many slope failures etc). Also, the satellite images would have to be available and able to be analysed very quickly, almost in real time to prevent a disaster. PWP's on the other hand can be monitored remotely at short time intervals with borehole instrumentation and checked against design guidelines allowing quick action to be taken (but what sure?). If deformation was a good guide, inclinometers etc would be installed BUT these cannot be monitored remotely or continuously (or at least last I used them); you need to run the trolley. Finally, "techniques may help" is not too positive. Monitoring PWP's will help.
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Yes, hindsight is a great science and it has helped us to learn and use available resources to better manage geotechnical risks. There is no one magic monitoring tool but you must implement a monitoring strategy that is risk-based and use a combination of monitoring tools. The objective of a monitoring strategy is not only to detect the failure but also to validate design assumptions for early risk mitigation and design optimisation.

At my mining company, at all sites around the world, we monitor tailings and dumps remotely using a combination of satellite and ground-based monitoring tools. The level of the surveillance effort (monitoring instruments, frequency, redundancy, oversight) depends on the consequence classification of the infrastructure.

I must also add that this applies to active and post-closure monitoring.
 
ToxicBunny said:
I see Gweezy is wasting the important peoples time while they have meetings with him and brief him on shyte that he doesn't understand.
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He is just thinking about how much they can pull out of De Beers...
And naturally, dinner...possibly his third or fourth one for the day...
 
konfab said:
Someone should tell him that they get hazenile from the tailings dam.
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He's over the hazenile craze now... he is all about the electric boats these days, they're more lucrative for his retirement fund.
 
dlk001 said:
Yes, hindsight is a great science and it has helped us to learn and use available resources to better manage geotechnical risks. There is no one magic monitoring tool but you must implement a monitoring strategy that is risk-based and use a combination of monitoring tools. The objective of a monitoring strategy is not only to detect the failure but also to validate design assumptions for early risk mitigation and design optimisation.

At my mining company, at all sites around the world, we monitor tailings and dumps remotely using a combination of satellite and ground-based monitoring tools. The level of the surveillance effort (monitoring instruments, frequency, redundancy, oversight) depends on the consequence classification of the infrastructure.

I must also add that this applies to active and post-closure monitoring.
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Ah sure and I'm sure there are really good tools to do this. Mud this type of "mudflow" collapse, hmmm. Basically it is the same failure mechanism as probably caused half the deaths in the recent KZN floods; a sudden and total loss of material shear strength due to saturation (no satellite going to see that in time - these slides took place over about 6 hours at night). The mudflow material in the KZN floods was not dissimilar to slimes (IMHO) being a fine grained silty sand overlying the residual bedrock. Once this layer became saturated and, on the lower slopes, the hydraulic head exceeded the material mass, the game was on, the soil became a fluid and took everything with it. Disclaimer; we do not get directly involved with slimes dams, mainly looking at rock slope stability, including in mines; not many in SA, also unfortunately.
 
As I said in my previous post, the preliminary low-resolution InSAR data is showing there were warning signs. It also corroborates with the stories backdating to 2019 when the first warning signs of increased risks started including poor design implementation.

This report is just the beginning. I have seen a lot more from my geotechnical colleagues but unfortunately, it's legally privileged reports. What I can say is just like the Brazilian failure, there is nowhere to hide. This was not a "safe" structure, there were poor decisions, and it was not a catastrophic failure without warnings.

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@dlk001 It sounds like this is an area that you have expertise in and I was wondering if you have any idea of the validity of the following comment on Daily Maverick (main article here)

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Do you know if it is true that the fine residue tailings dams have always been (and are still) regulated by the DWA? Would the course residue tailings dumps still be regulated by the DMRC even though they are the assets of the mine owners that can be bought and sold at will?
 
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