Design considerations for impounding at Site C, Canada

This paper outlines layout and design considerations for reservoir impounding at the Site C Clean Energy Project. The diversion scheme includes two fully submerged 10.8 m-diameter diversion tunnels with gated inlet structures. The capacity of the diversion tunnels needs to be reduced prior to impoundement to allow the reservoir to fill with normal inflows from upstream. The inlet closure gates are not capable of safely restricting flows, so methods of maintaining minimum downstream environmental flow releases of 390 m3/s and providing adequate energy dissipation during reservoir filling were examined.