Design and Construction of the 45 MW Kokish River Hydroelectric Project in British Columbia, Canada

Design and Construction of the 45 MW Kokish River Hydroelectric Project in British Columbia, Canada

Author: Egbert J. Scherman, Sam R. Mottram
Conference: HydroVision International 2014
Date: July 22-25, 2014

This presentation will cover the design innovations and lessons learned from the detailed design and construction of the Kokish River Hydroelectric Project recently constructed in the northern part of Vancouver Island located in British Columbia, Canada. This hydroelectric facility is a private sector development by Kwagis Power, a limited partnership of Brookfield Renewable Energy Group and the ‘Namgis First Nation that was awarded an energy purchase agreement by BC Hydro in an open call for clean energy. The project will generate up to 45 MW of clean renewable energy that will be delivered to the British Columbia electrical grid, with an annual energy production capacity of roughly 140 GWh, enough electricity to power close to 13 000 homes.

The Kokish River Hydroelectric project is a run-of-river project with a maximum design generation flow of 25 m³/s and operating head of 238 m. Peter Kiewit Infrastructure Co. was awarded an EPC Contract for the design and construction of the project with Knight Piésold Ltd. appointed the Design Engineer for the project.

The terrain, climate and permitting constraints presented numerous challenges that were all overcome with some innovative design solutions and a close working relationship between the Owner, Contractor and Design Team. These included:

  • Dealing with migratory Salmon and Stealhead that are present throughout the diversion reach of the project, both during construction diversion and operation;
  •  A diversion weir with the world’s largest capacity Coanda screen capable of regulating water flow depth over the screen to ensure emerging salmon fry safe passage over the screens;
  • A 70 metre long vertical slotted fish ladder that allows continuous migration around the diversion weir for both resident trout populations and migrating salmon;
  • Hydraulic model testing of the entire diversion weir, intake structure and fish ladder;
  • A 1 474 m long buried HDPE low pressure penstock connected to a 7 703 m long
    buried, high pressure steel penstock, using soil restraint to eliminate expensive
    concrete anchor blocks;
  • A surface powerhouse housing four vertical axis six?jet Pelton type turbine-generator units capable of handling the long duration flow ramping rates associated with the project;
  • A Powerhouse tailrace channel fish fence, designed to prevent upstream migrating Salmon and Steelhead from entering the tailrace; and
  • A sophisticated in-stream flow measuring and flow ramping protocols.

 

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