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Operation of the Multi-Intake Box Canyon Run-of-River Hydroelectric Project to Meet Environmental Commitments

Author: Toby Perkins
Conference: HydroVision 2017
Date: June 27-30, 2017

ABSTRACT
The Box Canyon Hydroelectric Project is a 16 MW run-of-river facility located in the McNab Creek watershed on the north side of Howe Sound, British Columbia, Canada. The Project includes intake structures on three of the tributaries to McNab Creek (Box Canyon, Marty and Cascara Creeks) as well as six minor tributary diversions, all of which feed into a single high pressure penstock to direct water to the powerhouse. With this arrangement, it may have the most hydraulically complex design of any run-of-river hydroelectric project in North America, if not the world. The powerhouse includes a single, multi-jet Pelton turbine and water is returned to McNab Creek. The Project is connected to the BC Hydro transmission system via a 2.8 km long, 138 kV transmission line.


Knight Piésold Ltd. was retained by the owner, Box Canyon Hydro Corporation (a subsidiary of Elemental Energy) to assist with 1) concept development, environmental assessment and permitting, 2) detailed design, and 3) operational monitoring of the facility. The Project was commissioned in early 2016.


Under the Project’s Water License, the Project has maximum allowable diversion rates, minimum instream flow requirements (IFR) and maximum flow ramping rates. These requirements are different for each intake and in McNab Creek, due to differences in hydrology, river morphology and fish species distribution.


The IFR requirement at each intake is controlled by the intake design to ensure that IFR is released as priority before water is able to be diverted for power generation. Similarly, the maximum diversion rate is controlled by the intake design, which passively limits the maximum amount of water that is able to enter the penstock. However, flow ramping must be controlled by plant operation. This paper will provide an overview of the Project’s key Water License commitments and how the Project was designed and is operated to meet these commitments.

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