The Site C Clean Energy Project is a 1,100 MW hydroelectric generating station with a 60 m high dam on the Peace River near Fort St. John, BC, Canada. During earthfill dam construction, the Peace River was diverted through two concrete lined diversion tunnels; each 10.8 m in diameter with gated inlet structures. Upon completion of the diversion period, the tunnels needed to be used to pass minimum flow downstream during the initial phases of the reservoir filling process with reduced flow capacity. The selected alternative was to install a series of four in-line orifices in one of the diversion tunnels to dissipate the energy in the inflow. The in-line orifices were designed and modeled after a successful precedent project in China but this is the first application in North America that the design team was aware of. Physical hydraulic modelling (PHM) was conducted at the Lasalle|NHC Laboratory in Montreal. Two different scales of physical model were constructed and tested to refine and optimize the design of the energy dissipation solution; 1/22.7 and 1/42.5. Complementary computational fluid dynamics (CFD) modelling was also utilized. The orifice installation was successfully completed on site in Summer 2024 and reservoir filling was successfully completed in Fall 2024. The design team had the opportunity to inspect the tunnel after it was dewatered to investigate the conditions of the orifices and surrounding tunnel liner so the final topic will outline the key observations from the post-operation inspection which confirmed the success of this innovative design.