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Publication(World Bank, Washington, DC, 2021-04-22) World BankThis Technical Note provides detailed information on the Brazilian risk classification system using the RI approach and the Indian RI system for the initial risk screening of a large portfolio of existing dams. Annex A provides basic information about the RI approach used in Quebec, Canada, for its dam classification system. These RIs are used for prioritization of required remedial works and other safety requirements. It should be noted, however, that RI is also a basic tool for preliminary level risk analyses for portfolios of dams and initial screening of risky dams, which may need to be supplemented by more advanced methods, depending on the type and potential risk of the dams. Because RI largely relies on visual inspection of the dams’ conditions, some critical failure modes could be missed. underestimated, or overestimated. In the higher risk cases, or whenever deemed appropriate, more detailed risk analyses, such as potential failure mode analysis (PFMA), can fill some of the gaps.
Publication(World Bank, Washington, DC, 2021-04-22) World BankPotential failure modes analysis (PFMA) is a process to systematically identify, describe, and evaluate the ways in which a dam and its appurtenant structures could fail under postulated loading conditions. Since 2002, PFMA has been introduced as part of five-year inspections under the U.S. Federal Energy Regulatory Commission (FERC) regulations for nonfederal hydropower dams in the United States. The PFMA is intended to provide an understanding of how and why dams fail by looking at how dams behave normally, learning to identify early signs that something is wrong, understanding the hazards and risks imposed by the dam, and being prepared for the unexpected behavior that leads to failure. The World Bank has assisted some countries in applying the PFMA for safety review of major existing dams and found that the tool is useful in prioritizing additional investigations needs and remedial works in coordination with key stakeholders, including owners, operators, and designers. This Technical Note contains guidance for preparing PFMA terms of reference for: (a) the FERC-based standard approach to PFMA; and (b) a simplified PFMA approach.