Publication: Canadian Consulting Engineer
Issue: October/November 2017
Issue Title: 2017 Canadian Consulting Engineering Awards
The 16 MW Box Canyon Hydroelectric project may have the most hydraulically complex design of any run-of-river hydroelectric project in North America, if not the world. It has nine intake structures on different creeks and tributaries, all feeding into a single, high-pressure penstock that directs water to the powerhouse containing a six jet vertical axis Pelton turbine generating unit.
The project has three main intakes and six tributary intakes that address the unique hydrology, river morphology, and fish species distribution along McNab Creek and its tributaries. It has an 8.6-km-long water conveyance system of interconnecting pipelines and high-pressure penstocks that handles varying intake elevations and flow contributions, requiring the addition and design of surge facilities and check valves.
The project design also takes into account the complex hydraulic transient pressures (water hammer), and provides unique ecological flow releases at each of the diversion weirs. Knight Piésold Ltd. assisted Box Canyon Hydro Corp. in project development, from concept development through to operational monitoring.
The original project concept was a 7 MW facility with a single intake on Box Canyon Creek. Knight Piésold optimized the design to the current 16 MW facility with multiple intakes, addressing complexities not typical in a single intake, run-of-river hydroelectric project.
The water conveyance system includes open channel sections, which divert water from the tributary intake to the main intakes. Given the steep terrain, all penstock branches were installed below surface to overcome challenging construction and design conditions that were encountered at several sections of its length.
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