Strathcona Dam. BC Hydro photo

Strathcona Dam. BC Hydro photo

Strathcona Dam project overcomes design obstacle

BC Hydro aims to start construction on water discharge update project in 2025

BC Hydro’s Strathcona Dam Water Discharge Upgrade Project was progressing as planned until a physical water model in 2021 showed some strong water vortices that had potential to damage the new structure during operations.

Additional time was taken to refine the design and recent water modelling has shown the issue to be resolved.

“This is a large capital project for us, and it’s obviously important that we get the design right to pass high water flows through our proposed outlet channel beside the dam,” said BC Hydro spokesperson, Stephen Watson. “While the original design looked reasonable, a small-scale physical model of the design showed that vortices – or a swirling underwater column – formed at the water intake which could be capable of pulling down air or debris. Debris could damage the new works and equipment.

“We modified the design and built a new physical model this year to test the revised design. And we now have good results to enable us to safely pass the various water flow rates downstream. That’s good news.”

READ MORE: Dam upgrade on popular Campbell River lake won’t affect recreation

READ MORE: BC Hydro has to choose between a tunnel or a channel at Strathcona Dam

The Strathcona Dam holds back the water storage within the Upper Campbell Reservoir/Buttle Lake.

BC Hydro is designing a new channel and intake structure for a low-level outlet on the right side of the dam to provide full flexibility to lower the water level in the event of a major earthquake. The new channel will also provide for improved downstream water management for fish flows during dry weather periods, flood risk management, and maintenance work.

Excavated within rock, the new outlet channel may be up to about 15 metres wide at the base, 30 metres deep and about 330 metres long. This work includes constructing two gates in a concrete structure located within the channel.

The previous channel design showed vortices appearing as the water approached the water intake works within the channel. Several design changes were made to the upstream side of the intake works to eliminate the vortex effect.

“This was about due diligence to confirm the design with a 1:20 scale physical water model, where we discovered this vortex issue within the design phase,” said Watson. “It has taken longer to get through the design phase, but had we not gone through this level of analysis and proceeded to construct the original design, it would have been far more problematic. Sometimes the planning work takes extra time to ensure we get it right.”

Water releases from the proposed channel may range from a small water release to a maximum flow of about 1,120 cubic metres per second, or enough flow to fill an Olympic-sized swimming pool in just over two seconds.

The total cost of the project is estimated to be in the hundreds of millions of dollars. A cost range estimate will be provided when a project application is filed with the BC Utilities Commission around spring 2024.

The Strathcona Dam was built in the mid-1950s and went operational with its 64 megawatt powerhouse in 1958. The earthfill dam is 53 metres high and 500 metres long. The gross capacity of the reservoir is 580,500,000 cubic metres or the equivalent of over 230,000 Olympic-sized swimming pools. Another analogy is it would fill BC Place, located in Vancouver, 216 times.

For more information on the project go to BC Hydro has proposed seismic upgrades to the Ladore Dam and John Hart Dam on the Campbell River system. The three dam safety upgrade projects are about the ongoing protection of downstream public safety.

BC Hydro is working towards starting the Strathcona Dam Water Discharge Upgrade Project’s regulatory and procurement processes in early 2023 and starting construction in 2025.

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