California Department of Water Resources (DWR) are in the process of developing a sustainable and consistent periodic risk analysis (PRA) process for its entire State Water Project dam portfolio. The PRA process for Castaic, Crafton Hills and Perris Dam were developed based on the FERC guidelines (2016 and 2021) and DWR’s risk procedures (2021). Stantec supported DWR in developing a process for undertaking their first L2RAs for Castaic, Crafton Hills, and Perris Dams.
Castaic is a 425-foot-high zoned embankment dam that impounds Castaic Lake and provides emergency storage during a shutdown of the California Aqueduct and provides recreation for Southern California. Perris is a 130-foot-high embankment dam and Crafton Hills is a 95-foot-high zoned embankment dam, both of which provide water supply for the Los Angeles region.
Consequence evaluation was performed using LifeSim modeling to inform life safety risk and screening level downstream economic losses using the California Structure Inventory. The consequences evaluation estimated potential loss of life under various fair weather and flood-induced potential failure scenarios. Results were used to approximate the consequences of the probable failure modes (PFMs) identified during the PRAs. Each PFM evaluated was assigned an event likelihood category and life safety consequence category, along with degree of confidence based on the consequences evaluations. The completed PRAs portray the risk associated with the Castaic, Crafton Hills and Perris Dams and its appurtenant structures as a product of the likelihood of loading, the likelihood of failure occurring, and the consequences of that failure. Lessons learned when evaluating dam safety consequences for PRAs will be presented. This will include discussion of key information and sensitivity analysis and how the results of consequence evaluations performed in LifeSim helped the Dam Safety Risk Analysis within a risk-informed decision-making framework.
