Award of Excellence: Kokish River Hydroelectric Project
Publication: Canadian Consulting Engineer
Issue: October/November 2015
Issue Title: 2015 Canadian Consulting Engineering Awards
The Kokish River Hydroelectric Project is a 45 MW run-of-river facility 15 km east of Port McNeill, on the north of Vancouver Island, B.C. Every step during the development process took into consideration the diversity of fish habitats in Kokish River. The project has unique and innovative details throughout the diversion reach designed to cater to this sensitive environment, and in particular the presence of steelhead trout and salmon. It has one of the largest capacity Coanda screen intakes in the world, together with one of the smallest Obermeyer crest gates in the world, a wrap-around vertical slot fish ladder, and a tailrace fish screen.
As the lead design engineer, Knight Piésold worked closely with the owner, Kwagis Power Limited Partnership, and the EPC Contractor, Peter Kiewit Infrastructure, to develop innovative and cost-effective solutions that more than met the stringent fisheries permitting requirements. The Knight Piésold team was involved throughout the project’s development.
“Fish first” design
The intake and diversion weir were designed to:
- Divert a portion of the natural stream flow to the water conveyance system, while excluding large sediment and debris to limit damage to the pipe and turbine generating equipment.
- Provide safe passage — for both adult and juvenile salmon and steelhead trout — past the intake and diversion weir, for upstream and downstream migration.
- Allow for precise control and realtime flow monitoring of the in-stream flow release downstream of the intake to maintain the natural aquatic ecology. The required in-stream flow releases varied by season and month from 3.4 m3/s to 12 m3/s.
- Allow passage of flood flows without damage to the structure.
The 9.3 km-long water conveyance system is unusually long for a high-head, run-of-river project in B.C. Its design had to be cost-effective, yet robust, because the penstock is exposed to hydraulic transient
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