Tactical and strategic planning for dam portfolio using ORE2_Tailings
Jun 30th, 2021
Tactical and strategic planning for dam portfolio using ORE2_Tailings is the third of a series of blogposts explaining how to use ORE2_Tailings™ results. Indeed it follows:
We use the same figures we have developed in those prior discussions.
Summary of the portfolio ORE2_Tailings™ results
With respect to probability of failure
The portfolio of ten dams is made of two “bad apple” dams (AA2, BB6), three dams (BB1, BB2, BB3) that are above world-wide benchmark and a balance of five dams (AA1, AA3, AA4, BB4, BB5) that are straddling or below the word-wide benchmark.
The first two groups display great potential for mitigation provided mitigation of ancillary water management issues.
With respect to risk
By introducing the multi-dimensional consequences of failure we evaluated the risks and got the following graph for the considered portfolio:
The graph tells us the highest risks are generated by dam AA2, then BB1, BB2, BB6 and the rest are “negligible”. Interestingly, the “bad apple” BB6 which has a similar probability of failure than AA2 has only the fourth ranking risk due to its low consequences. One would be tempted to split mitigative funds proportionally to the dams’ risks, but is this the best planning? Read further for the answer.
With respect to tolerance
We then reported (graph below) the same dams on a annualized probability of failure-consequence (pf-C) graph with two tolerances:
- corporate and finally
- the world-wide benchmarks.
In this example, no dam shows up below the operation’s tolerance (yellow curve). Hence all the risks are corporate (brown curve). We also noticed that dams BB3, BB5 and BB6 are corporately tolerable. All the other dams are corporately intolerable! The prioritization of the risk from top to bottom misleads its users on dam BB6 quite badly as it actually generates a tolerable risk.
Looking at the part of intolerable risk generated by the various intolerable dams, we got the figure below which shows that dams AA2, BB1, BB2 have the largest corporately intolerable risks. Thus we stated they should receive mitigative budget proportionally to their intolerable risk. The conclusion was that the money allotted by the top-down approach to BB6 and the “minor risk dams” would be misallocated. As a result of the misallocation, the AA2, BB1 and BB2 dams would be left overexposed.
In many cases we have seen the “misleading results” are even more significant, and the hands-on everything “fix-it-all” approach to lead to misguided planning.
The next step in ORE2_Tailings™ results interpretation
Definition of tactical and strategic risk dams and their mitigation principles
As we can see in our glossary tactical and strategic risks obey to rigorous definition. An intolerable risk is a tactical risk if one can sustainably and economically mitigate it by reducing its probability of failure. Mitigation examples could be:
- reinforcement of the dam itself, and/or
- enhancements of the ancillary water management, and finally
- reduction of liquefaction potential, etc.
A strategic risk requires a system change in order to shift under tolerance. That means for example reducing consequences by reducing volume/height, moving people away from the flood zone, etc.
Application to the considered portfolio
Now, the interest of this example is that one could consider at first sight AA2 and AA4 to be tactical risks. Indeed if we include all possible mitigation those risks could slide down toward tolerance at credibility threshold (1.00E-06). The question then is: can the probability of failure of a dam be mitigated in a sustainable and economic way to such a low level ? However, one could start, for instance, by bettering the ancillary water management system and reducing the probability of failure of AA2, hence reducing its contribution to intolerable risks. This would be a partial mitigation of AA2.
BB1, BB2 on the other hand are clearly and will remain strategic risks. Indeed, no matter how much you reduce the probability of failure, they remain “outside of tolerance” down to credibility threshold.
The pie diagram below displays the intolerable risk inventory with the dam AA2 partially mitigated (see above). We can see that BB1 and BB2 would then become the new main focus.
Dam Intolerable Risks with only AA2 partially mitigated.
Furthermore, if we look at a what-if scenario with every structure partially mitigated in terms of water management we see significant changes in the portfolio’s intolerable risk landscape.
Dam Intolerable Risks with every structure partially mitigated.
In other words: a dam portfolio overall risk landscape changes as one decides dams mitigation implementations. Thus the outmost care is necessary to ensure rational, efficient, sustainable and balanced approaches.
Closing remarks on tactical and strategic planning for dam portfolio using ORE2_Tailings
ORE2_Tailings™ allows to simulate alternative mitigation planning including tactical and strategic options. The goal is to find good balance and efficiency.
Thus it become possible to justify risk management actions and to allocate mitigative capex in the best possible way considering the various constraints, including of course the:
- true nature of consequences and all their dimensions,
- sustainability of the implementation,
- costs of the mitigation and finally
- optimization and ethics of the expected results.
These are the reasons why only a dynamic and integrated approach can bring the proper answers to managers of dams portfolios. Allowing what-if scenario and the measurement of the effectiveness of the mitigations and related investments is paramount.
Tagged with: GISTM, intolerable risks, probability of failure, risk tolerance, tactical and strategic risk, Tailings Dam
Category: Consequences, Hazard, Mitigations, Probabilities, Risk analysis, Risk management, Tolerance/Acceptability, Uncategorized