The FERC RIDM…What's In It For Me?

The Federal Energy Regulatory Commission (FERC) began to publish guidelines for dam safety assessment using Risk Informed Decision Making (RIDM) in 2014. Risk analysis has been the subject of several presentations, most of which have discussed risk analysis from the regulatory and engineering perspective. This paper focuses on the owner’s perspective –specifically, why was risk analysis considered appropriate for these particular applications, and what are some of the benefits that have resulted from these studies.
The Chelan County Public Utility District (Chelan PUD) owns and operates three large hydroelectric projects (Projects) on the Columbia and Chelan Rivers (Rock Island, Rocky Reach, and Lake Chelan) in central Washington with a combined generating capacity of approximately 2000 MW. Chelan PUD has made diligent efforts to maintain reliable operations and public safety, and has invested significant resources to address the safety due to the PMF, which until recently was considered the principal dam safety concern for the Chelan PUDs Projects.
Recent advances in earthquake engineering have shown that the seismic hazard for central Washington is significantly greater than was historically realized, and now the seismic loads have become the principal safety issue for the Chelan PUD Projects. Using traditional dam deterministic safety methods and guidelines would require the Chelan PUD to evaluate the projects for revised maximum credible earthquake (MCE) seismic hazards, and if necessary, perform modification to enhance the safety of the projects to current standards.
In cooperation with the FERC, a Probabilistic Seismic Hazard Analysis (PSHA) was performed for central Washington. The PSHA estimates the potential seismic hazard based on return frequency. The PSHA was then used to perform a pilot seismic risk assessment of the Chelan PUD projects. The initial results from the pilot risk studies have been very encouraging for the Chelan PUD, regarding the current safety of the projects and the long-term reliability of the hydroelectric resource for their constituents.