250
15 Risk-Informed Decision Making
Fig. 15.7 Annual probability of failure versus dams of the portfolio and benchmarking cases
(green). The annual probability of failure for each dam is displayed as an orange-red bar due
to the uncertainties. The longer the bar, the larger the uncertainties
• the min-max values of the world-wide p f portfolio based on historic records (Oboni
and Oboni 2013), represented by the green bar “World-wide decade around 1999”;
• the values of p f (“Dewatered and slurry and US”, green bar) obtained in Taguchi
(2014), which attempted a theoretical estimate of the annual p f of standard and
dewatered tailings.
The portfolio benchmarking in terms of the probability of failure shows that in
the considered case there are dams (1A, 1B, 2, 2 on 3) below the historic benchmark.
Dams 3 is above the historic benchmarks, although still significantly lower than the
Mount Polley or Samarco estimates made with available pre-failure data. Dam 4 is
an imminent catastrophe. Additional studies and information would make it possible
to reduce the uncertainties (length of the orange-red bars).
Mitigation would push the bar down, an aspect we will discuss later in this chapter.
Long term lack of maintenance and the effects of climate change will tend to push
the bars up, as has already occurred with Dam 4.
15 Risk-Informed Decision Making
Fig. 15.7 Annual probability of failure versus dams of the portfolio and benchmarking cases
(green). The annual probability of failure for each dam is displayed as an orange-red bar due
to the uncertainties. The longer the bar, the larger the uncertainties
• the min-max values of the world-wide p f portfolio based on historic records (Oboni
and Oboni 2013), represented by the green bar “World-wide decade around 1999”;
• the values of p f (“Dewatered and slurry and US”, green bar) obtained in Taguchi
(2014), which attempted a theoretical estimate of the annual p f of standard and
dewatered tailings.
The portfolio benchmarking in terms of the probability of failure shows that in
the considered case there are dams (1A, 1B, 2, 2 on 3) below the historic benchmark.
Dams 3 is above the historic benchmarks, although still significantly lower than the
Mount Polley or Samarco estimates made with available pre-failure data. Dam 4 is
an imminent catastrophe. Additional studies and information would make it possible
to reduce the uncertainties (length of the orange-red bars).
Mitigation would push the bar down, an aspect we will discuss later in this chapter.
Long term lack of maintenance and the effects of climate change will tend to push
the bars up, as has already occurred with Dam 4.