Western United States

A utility company in the Western United States owns and operates two dams as part of a pumped storage project in a remote mountainous area. The pumped storage project consists of an upper reservoir, lower reservoir, and an underground powerhouse between the two reservoirs. The upper reservoir is impounded by a 315-foot-high concrete-faced rockfill dam with an ungated spillway, and the lower reservoir is impounded by a 260-foot-high concrete-faced rockfill dam with a spillway controlled by six radial gates. Both dams were constructed by the owner in the late 1950s. The pumped storage project has the unique ability to rapidly transfer water between the upper and lower reservoirs using the powerhouse, either in power generating mode (water flows from the upper reservoir through the powerhouse to the lower reservoir) or in pump-back mode (water is pumped uphill through the powerhouse from the lower reservoir to the upper reservoir). Both dams are classified as high hazard potential in accordance with the Federal Energy Regulatory Commission (FERC) Hazard Potential Classification guidelines. On April 11, 2022, FERC established new requirements for Part 12D inspections. A notable change to the guidelines is the development of two types of Part 12D inspections: periodic inspections and comprehensive assessments(CA)s, where the latter includes a Potential Failure Mode Analysis (PFMA) and Level 2 Risk Analysis (L2RA) workshop. The owner retained Geosyntec to conduct the 2024 FERC Part 12D CAs and facilitate the PFMA/L2RA workshops for both dams.