Franco Oboni & Cesar Oboni


Figure 8. Finding the “minimum ALARP” (intersection of the risk reduction (blue curve) vs. mitigative investment (orange curve). The pink area corresponds in this example to mitigation levels that are still intolerable from the harm to people point of view, i.e. FERC/ANCOLD intolerable


It is paramount to remember that, as it is expected that all mitigations may have side-effects, these should


be carefully studied before the final decisions are made. The ALARP process, as described above, is iterative and demands a nuanced evaluation that


balances risk reduction and constructability with cost considerations. By systematically analyzing each mitigation’s effectiveness and cost impact, the process ensures that the selected level of mitigation is both economically viable and aligned with safety objectives. As already mentioned, this approach allows stakeholders - owners, engineers, and regulatory bodies alike - to make informed, responsible decisions regarding dam safety. The model’s flexibility in adapting to new mitigation measures and evolving risk thresholds underscores its value in TSF management, providing a structured yet adaptable framework that upholds safety as system conditions change. The resulting ALARP assessment, when conducted transparently and in collaboration with the EoR and risk analysis teams, strengthens the decision-making process and facilitates an approach that is both justifiable and resilient over time.


8. Conclusions This paper presents a quantitative approach to tailings storage facilities risk assessment that integrates evolving hazards and human factors, bridging gaps left by traditional methodologies. The probabilistic causality model described in this paper quantitatively demonstrates the central role of human factors, underscoring how design choices, maintenance practices, and operational decisions influence risk in some cases more significantly than natural events alone. The comparative analysis of three dam cases – “Good,” “Bad,” and “Ugly” – highlights the robustness of the model in differentiating risk levels and in guiding practical mitigations. Indeed, the model effectively demonstrates its capacity to differentiate hazard and hence risk levels based on real-world operational variables. By enabling tailored risk assessment scripts and scenario planning, this approach offers a replicable framework that can support TSF owners, engineers, and stakeholders in pursuing a risk-informed


194 | Dam Engineering | Vol XXXIII Issue 3


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