208
14 Risk Assessment for the Twenty-First Century
• Mount Polley and Samarco annual p f evaluated with the ORE2_Tailngs methodology;
• the min-max values of the world-wide portfolio based on historic records (Oboni
and Oboni 2013);
• the values obtained by a Ph.D. Thesis (Taguchi 2014) at UBC which attempted a
theoretical estimate of the annual p f of standard and dewatered tailings.
The vertical axis indicates the annual p f . For each structure a yellow bar depicts the
uncertainty related to the probability estimate. The portfolio bench-marking shows
that in the considered case there are dams below the historic benchmark. Some overlap
the benchmarks limits and some are above the upper limit, but are, however, still
significantly lower than Mount Polley or Samarco estimates. We note the following:
• Additional studies and information would make it possible to narrow the uncertainties (length of the yellow bars).
• Mitigation on a specific dam would push the respective bar down.
• Long term lack of maintenance, climate change effects would tend to push the
bars up.
• The combination of this graph with the cost functions for each dam gives the risks
(Fig. 10.6). Interdependent dams can be analysed and their effect included in the
portfolio analysis.
The development of a portfolio-specific risk tolerance threshold (Chap. 13) allows
users to determine which risks actually really matter in a portfolio.
As a multidimensional consequence function is foreseen (consequences are generally multifaceted, see Sect. 7.6) it is possible to perform integrated comparison
of project execution, community, legal, environmental, financial, technical and H&S
risks (or whatever dimension the user may want to define). This convergent risk vision
fosters healthy discussions and helps organizations to build consensus on decisions
at the operational, tactical and strategic levels.
In Fig. 10.6 (in Sect. 10.2.2) various scenarios for “Dam 1” are displayed:
• Dam 1 mitigation shifts the risks downwards.
• Climate change effects increase the risks of the same structure.
• Lifts (also called raises in some cases) will also increase the risks, as losses will
also increase.
• Finally inter-dependency between Dams 1 and 2 will generate the largest losses,
but at a lower annual probability.
It is therefore possible to understand which are the most critical sources of threats
to the tailings dam or compare each tailings dam’s risks, e.g., which dam and hazard are loaded with the largest potential losses (split by type of loss: physical, BI,
environmental, etc.) in a portfolio.
14 Risk Assessment for the Twenty-First Century
• Mount Polley and Samarco annual p f evaluated with the ORE2_Tailngs methodology;
• the min-max values of the world-wide portfolio based on historic records (Oboni
and Oboni 2013);
• the values obtained by a Ph.D. Thesis (Taguchi 2014) at UBC which attempted a
theoretical estimate of the annual p f of standard and dewatered tailings.
The vertical axis indicates the annual p f . For each structure a yellow bar depicts the
uncertainty related to the probability estimate. The portfolio bench-marking shows
that in the considered case there are dams below the historic benchmark. Some overlap
the benchmarks limits and some are above the upper limit, but are, however, still
significantly lower than Mount Polley or Samarco estimates. We note the following:
• Additional studies and information would make it possible to narrow the uncertainties (length of the yellow bars).
• Mitigation on a specific dam would push the respective bar down.
• Long term lack of maintenance, climate change effects would tend to push the
bars up.
• The combination of this graph with the cost functions for each dam gives the risks
(Fig. 10.6). Interdependent dams can be analysed and their effect included in the
portfolio analysis.
The development of a portfolio-specific risk tolerance threshold (Chap. 13) allows
users to determine which risks actually really matter in a portfolio.
As a multidimensional consequence function is foreseen (consequences are generally multifaceted, see Sect. 7.6) it is possible to perform integrated comparison
of project execution, community, legal, environmental, financial, technical and H&S
risks (or whatever dimension the user may want to define). This convergent risk vision
fosters healthy discussions and helps organizations to build consensus on decisions
at the operational, tactical and strategic levels.
In Fig. 10.6 (in Sect. 10.2.2) various scenarios for “Dam 1” are displayed:
• Dam 1 mitigation shifts the risks downwards.
• Climate change effects increase the risks of the same structure.
• Lifts (also called raises in some cases) will also increase the risks, as losses will
also increase.
• Finally inter-dependency between Dams 1 and 2 will generate the largest losses,
but at a lower annual probability.
It is therefore possible to understand which are the most critical sources of threats
to the tailings dam or compare each tailings dam’s risks, e.g., which dam and hazard are loaded with the largest potential losses (split by type of loss: physical, BI,
environmental, etc.) in a portfolio.