Franco Oboni & Cesar Oboni Again CCF has nefarious potential on this additional parallel subsystem. Adopting a very simplified


approach to CCF it was possible to assume that insufficient rigor, complacency, conflict of interest, common excessive audacious approach in M1, M2 could reduce the expected positive result of any mitigation to nil. Four levels of mitigation were studied. As it can be seen from Figure 2 the paper concluded that a dam sporting a probability of failure PoF of 10-3 could see it reduced to 2*10-4


by simply adding rigorous and unbiased peer review and detailed


inspections with swift follow-up without any changes to its geomechanical FoS or geomechanically derived PoF. Obviously this result was and is generic and should be integrated with all the dam-specific details of a candidate dam to be risk assessed: the devil is indeed always in the details! Based on the above and more experiences made in risk analyses, a number of features aiming at describing the “devils” were introduced in the methodology. A summary is delivered in the next section.


4. Root Causes, Underlying Hazards, Measures, Parent-of Summary A list of root causes (leftmost two columns) that appeared to cover the set of world-wide dams studied to date was introduced. The list is of course subject to changes in the future but represents in our eyes the minimum set that is absolutely necessary to deliver an image of the risks generated by a tailings dam.


As it can be seen in Table 2, there are many hazards that cover the entire system, and many common


“parents” within the system. Indeed governance, human errors and other “soft issues” have ubiquitous effects on a dam system and become “parents” to other hazards within the considered system. These constitute the Key Performance Indicators of the dam (KPIs)


186 | Dam Engineering | Vol XXXIII Issue 3


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