BC Hydro continues to work on the design of the proposed John Hart Dam Seismic Upgrade Project though a few more answers need to be clarified to allow for design advancement. Site drilling, starting the week of July 10, will fill those data gaps. The work will begin on the John Hart reservoir and take place over about a month. The drilling activities will then move onto the dam and surrounding land area for about two months.
“This project is to seismically upgrade the various components of the dam so it can withstand a 1-in-10,000 year earthquake,” said BC Hydro’s Stephen Watson. “It is a comprehensive upgrade to the over 800-metre-long dam that’s made of earthfill and concrete sections, including the spillway dam.”
The planned strengthening upgrades include upstream and downstream earthen berms on the middle earthfill dam and the north earthfill dam, and a downstream berm on the old water intake dam where the existing penstocks are located.
“The purpose of this summer’s drilling program is to confirm the subsoil conditions,” said Watson. “That will then confirm the treatment method for the foundation beneath the proposed upstream berms. The biggest footprint expansion is the upstream berm near the middle of the dam that will go well into the reservoir. We need to confirm the reservoir bottom conditions so we know exactly how the foundation soils need to be dealt with before we begin to place material during the construction phase.”
The Environmental Management Plan for the drilling work has been shared and reviewed by government agencies, First Nations and the City of Campbell River.
A barge with the drill rig works will be used for the reservoir drilling. The methodology is to place a hollow steel pile vertically into the reservoir from the surface into the lake bottom sediments, to a depth that is adequate to achieve a secure seal between the casing, the hole and the reservoir bottom. The drilling work will then be conducted within that steel pile to isolate any water turbidity and protect water quality. The completed drilling work results will be incorporated into the project design.
There are no anticipated road closures across the dam during the drilling work, with the potential for some intermittent and short-term alternating single-lane road traffic.
The dam upgrade project also includes a new overflow spillway under the road deck at the spillway section of the dam, upgrades to the concrete dam such as the deck-pier connections, and a complete replacement of the spillway gate works, including gates and the hoist tower structure. Completion of project’s feasibility design is targeted for early 2019. Hydro will eventually go to the BC Utilities Commission for project approval. Pending funding and regulatory approvals, the project may begin as early as 2021.
“BC Hydro has been working with a Technical Advisory Board for the project, and the board has endorsed the technical solutions for the upgrades,” said Watson.
In other project work, fish and wildlife studies were awarded in January 2018 for assessing potential reservoir drawdown effects on fish and wildlife in and around the John Hart Reservoir during the construction period. That work will happen this summer. BC Hydro continues to work with the City of Campbell River on domestic water supply water quality considerations and mitigation work. BC Hydro will likely need a reservoir drawdown of up to 10 metres during the construction phase to complete the upgrade work. Hydro recently had a project update meeting with the two-dozen members of their community liaison committee.
The John Hart Generating Station Replacement Project is replacing the old aboveground penstocks and generating station with a new underground tunnel and powerhouse. With that work downstream of the dam nearing completion, including a much lower water intake into the reservoir, it will allow BC Hydro to focus on seismically upgrading the John Hart dam.