Upstream view of the Strathcona Dam. (Supplied by BC Hydro)
BC Hydro continues to make progress on the water discharge upgrade designs to Strathcona Dam to enable a draw down the Upper Campbell Reservoir level after a severe earthquake.
The upgrades will also provide better downstream water management reliability for downstream fish habitat flows to flood risk management.
“For a few years now we have been meeting and consulting with First Nations, government agencies and stakeholders on the project as we continue to refine the design,” says BC Hydro spokesperson, Stephen Watson. “While day-to-day it is very safe, the Strathcona facility has deficiencies that may limit its ability to operate or cause it to fail following a severe earthquake. A new low-level outlet, which is a deep excavated channel, will allow us to lower the reservoir level after an earthquake to minimize risks to the dam. The final design will ultimately be developed and then we’ll go to the BC Utilities Commission for approval in around 2022.”
Strathcona Dam and a diagram of the proposed works to the right bank. It includes a deep excavated channel in bedrock, with improved water release facilities. (Supplied by BC Hydro)
For BC Hydro there are two main project objectives.
First, to excavate a deep channel in bedrock on the right bank of the dam, and then construct a new water release outlet structure to allow for a deep reservoir level drawdown. The new structure is planned to be about 32 m long, 17 m wide, and 29 m high.
The concrete structure will house two water discharge gates. The gates will allow the reservoir to be lowered below the normal operating level, which will reduce the risks to the dam. It will also provide downstream flood risk management operations. The channel length is about 330 metres.
Second, the project will remove the three 61-year-old spillway gates and hoist system and construct a new concrete passive overflow spillway. The crest of the spillway will be positioned so water only free-spills during large storm events.
The two new gates within the excavated low level out channel will provide improved water management flexibility for fish habitat flows, power generation and flood risk management.
Watson said there are currently no plans to lower the water level at Upper Campbell Reservoir/Buttle Lake during construction. Construction of the low-level outlet channel will take place downstream of a temporary rock plug, which is a portion of the channel at the upstream end that will be excavated last. Work on the overflow spillway will likely take place downstream of a temporary bulkhead or during low reservoir periods.
The project, when completed, will not change BC Hydro’s existing water license for storage levels or water release, though the utility will go through a Change of Works application to the Comptroller of Water Rights on the facilities modified configuration.
“We are looking to have funding approval and regulatory approvals, such as the BC Utilities Commission, by around late 2023,” said Watson. “The procurement process may also begin in 2022 and construction may begin in early 2024.”
Watson said the road across the dam will be temporarily closed for about three years during the construction period.
The existing Strathcona Dam Campground is planned to be permanently closed as early as late summer 2020, with the new Upper Campbell Reservoir Campground opening around the same time.