This paper outlines layout and design considerations for reservoir filling at the Site C Clean Energy Project. The Site C Clean Energy Project is an 1,100 MW hydroelectric generating station with a 60 m high dam on the Peace River near Fort St. John, BC, Canada. The project includes two fully submerged diversion tunnels each 10.8 m in diameter with gated inlet structures. The capacity of the diversion tunnels needs to be reduced during reservoir filling to allow the reservoir to fill with normal inflows from upstream. The inlet closure gates are not capable of safely restricting flows, thus alternative methods of maintaining minimum downstream environmental flow releases of 390 m3/s and providing adequate energy dissipation during reservoir filling were examined. The selected alternative was to install a series of four in-line orifices in one of the diversion tunnels prior to reservoir filling. The orifice design is based on work in China on the Xiaolangdi project, as well as physical hydraulic modelling (PHM) and computational fluid dynamics (CFD) modelling.
Bruce, J., J. Croockevit, F Yusuf, J. Nunn and A. Watson. 2019. “Diversion Tunnel Orifices for Energy Dissipation During Reservoir Filling at Site C,” in Proceedings of the 87th Annual Meeting of International Commission on Large Dams (ICOLD), 9-14 June 2019. Ottawa, ON: Canadian Dam Association.