World-wide ORE2_Tailings quantitative risk assessment experience

World-wide ORE2_Tailings quantitative risk assessment experience

Feb 23rd, 2022

Riskope’s world-wide ORE2_Tailings quantitative risk assessment experience can be summarized in one single graph we will show below.

ORE2_Tailings™ (©Riskope, 2014-*) is a subset of ORE (Optimum Risk Estimates) which is a “universal” platform for quantitative risk assessments, ERM we deploy for:

  • mining, i.e. tailings, open pits,
  • transportation,
  • forestry and finally
  • suppliers.

We have deployed ORE for hundreds of operations worldwide. Today we will focus on tailings storage facilities.

Sample portfolio for ORE2_Tailings™ performance summary

 We selected a sample portfolio encompassing 21 sites, with variable number of dams (between 1 and 9, to be precise). They are located in North and South America, Central and South East Asia, and finally in Europe. The sites are anonymized, their name replaced by the country followed by a cardinal number.

As it can be seen in the graph below, Canada has 11 sites, Brazil four sites, named Br 1 to Br 4, etc.

The dams are built following upstream, downstream, center-line types of cross-sections. The stored tailings are the result of base- and precious metals extraction.

The dams are active, inactive and in some cases closed. In some cases ORE2_Tailings™ was used to develop projections including raises, alterations and, of course, climate change effects. ORE2_Tailings™ is also being used to demonstrate ALARP mitigation in compliance with GISTM.

We aggregate each site’s dams by considering the extreme min-max scenarios for probability and consequences. This allows a “rectangle perimeter” display of the risks of the dams present at the site.

Oftentimes risks have significant inverse correlation between consequences and probability. As a result small consequences have high probabilities and larger consequences have a smaller probabilities, of a given hazard. A good example of this are car accidents: fender-bender are way more likely than full loss of the vehicle. However in the case of tailings one can assume that probability of catastrophic failure and their consequences are rather uncorrelated at least at the standard level of analysis that data allow. Indeed the consequences of a catastrophic failure are not dependent on the probability of the failure, but rather on the population density downstream (PAR, PLL), the topography, etc,

World-wide ORE2_Tailings quantitative risk assessment experience

Below is the “raw” risk landscape we generate based on our ORE2_Tailigs™ deployments experience. As one can see it delivers general information on ranges, but does not allow to make any risk informed decision making yet. We need to add information to increase its value.

riskope's World-wide ORE2_Tailings quantitative risk assessment experience

Probabilities: the range we see for this world-wide summary goes from 1E-06 to several percent, which is equivalent to saying that the studied dams varied from “the limit of credibility” to very near to pre-catastrophic levels.

Consequences: we use the ORE2_Tailings™ built-in consequence evaluator. This considers the additive nature of consequences and converts all components into monetary values. The dimensions cover: harm to people, environmental damages, physical losses, crisis and reputational aspects. More information is available in our book on tailings management. As one can see in the graph, consequences cover a very wide range, spanning from 10M$ up to over 10B$. Interestingly there are two strong concentrations in the sample portfolio, one of consequences around 100M$ and another consequences between 1B$ and 10B$.

Risks Benchmarking

Below we reproduce the same landscape with the world-wide benchmark thresholds we developed.

Indeed, if we look at the thresholds the landscape  starts to make more sense.

World-wide ORE2_Tailings quantitative risk assessment experience with worldwide benchmarks 2

Notice how many sites “straddled” the min-max world benchmark band, meaning that, after all, there is a sort of planetary convergence on the performance of tailings dams. This is not a surprise because engineers around the world designed their dams using similar factor of safety criteria. However, what comes as a surprise is the wide range of resulting probabilities. That range is the result of varying level of care, maintenance, governance, management from site to site.

This graph   enables to start a dialogue with the owner, the EoR.  But again, it not enough to really define a sensible roadmap to portfolio mitigation because it does not help discerning which sites/dams can really “hurt” the owners and the public. 

Risk triaging plan

The ICMM Tailings Management: Good practice guide ( includes the following definition of As low as reasonably practicable (ALARP):

ALARP requires to take all reasonable measures with respect to ‘tolerable’ or acceptable risks. The idea is to reduce them even further until the cost and other impacts of additional risk reduction are grossly disproportionate to the benefit. [based on the definition provided in the Standard]

and also Page 15…

One can then evaluate the acceptability of the risks considering the potential consequences for health and safety, social, environmental, financial and other factors that may occur (risk evaluation). Once one assesses the risks, it is time to develop risk management plans. The goal is to eliminate, reduce or mitigate, and communicate the risks.

We can see that following ICMM/GISTM tailings dam risk management must include the notion of tolerable risk. Thus we reproduce below once again the risk landscape adding a sample risk tolerance threshold we developed for a large mining company. We show it in red.

World-wide ORE2_Tailings quantitative risk assessment experience with corporate tolerance

Now  we can immediately say:

Risks: Many North American sites we studied fall into corporately tolerable territory for large companies (under the red curve) due to location, land use and topography. Note that the probabilities of failure of these sites can be quite high for some sites. This indicate poor conditions, standard of care, maintenance and monitoring. However a majority of sites in this portfolio fall in the intolerable territory (above and right of the red curve) even for large companies.

Armed with the risk landscape we can also swiftly evaluate which sites represent strategic, tactical risks and therefore require varying degrees of attention.

Focusing on the intolerable risk sites:

  • Sites like Can 4, US 1 are intolerable but partially manageable. Indeed mitigation can occur by reducing the probability of failure of some of their dams. Hence they represent tactical risks for they owners.
  • Sites like EU, BR x, etc. are mostly intolerable and unmanageable within the realm of credibility. Therefore they represent strategic risks and their mitigation requires strategic shifts such as for example, altering the system.

Risk tolerance roadmap

Another reason to consider risk and risk tolerance is that we can deliver a roadmap for large portfolio in a systematic and transparent manner.

World-wide ORE2_Tailings quantitative risk assessment experience with roadmap

By ranking the sites  by decreasing intolerable risks we deliver a clear prioritization roadmap for management . We will not delve into the details of road-mapping because of obvious space limitation of this blogpost.

Closing remarks

The selected portfolio indicates that, despite similar deterministic criteria were used during the design, significant ranges of probabilities arise due to varying standards of care, monitoring, and maintenance.

Prioritizing based on consequences-only can lead to wasting precious resources, time and address the “wrong dams”.

Tailings dam risk management must include tolerance/acceptable threshold to provide meaningful answers.

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Category: Consequences, Mitigations, Optimum Risk Estimates, ORE2_Tailings, Probabilities, Risk analysis, Risk management, Tolerance/Acceptability, Uncategorized

2 responses to “World-wide ORE2_Tailings quantitative risk assessment experience”

  1. john says:

    with the new focus in “the Guide” on Surveillance (whatever that means) what is the impact on survelled sites as opposed to non-surveilled?

  2. Franco says:

    Monitoring is one aspect out of many. Good monitoring is certainly a positive factor but it is not a “miracle pill”. Dams failure is generally the result of several deficiencies.

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