T TOOK one storm in February to knock out two of the three pipelines to the John Hart Generating Station on Vancouver Island. Crews from BC Hydro – the Canadian electric utility in British Columbia-leapt into action. At any time that flows in the Campbell River drop, it’s a potentially dangerous situation for the salmon downstream. The river supports spawning grounds for all five species of Pacific Salmon, and both summer and winter runs of Steelhead.

In less than an hour that early February morning, water from the dam had been released to restore water levels. Before the decade is out, this scenario will be more avoidable once the estimated CAD 940M (USD 910M) John Hart Generating Station replacement project is completed. Construction on the project, expected to start later this year, includes replacing the current pipelines with a 2.1km-long tunnel.


Located within the City of Campbell River on Vancouver Island, the John Hart Generating Station has been operating since 1947 and is one of the oldest generating facilities in BC Hydro’s hydroelectric system-and one of the most important assets on Vancouver Island, according to the utility company. The Campbell River System comprises three power-generating stations. Upper Campbell Lake discharges through the 65 MW Strathcona Generating Station into Lower Campbell Lake. Lower Campbell Lake is the headpond for the 47MW Ladore Generating Station. And Ladore discharges into John Hart Lake, which is the reservoir for the 126MW John Hart Generating Station. Upper Campbell Lake is the storage reservoir for all four installations.

Currently the three 1.8km-long woodstave and steel pipelines built some 60 years ago carry water from the John Hart reservoir and Dam to the generating station. There are three main drivers for the project. One being the risk of a station shutdown and river flow reduction, which would have subsequent impacts to fish habitat, as seen just this spring. Secondly, the generating station and pipelines may not withstand a low to moderate earthquake. Finally, the six generating units are in poor condition and their capacity is declining.

"We were originally going to replace the three aboveground penstocks," explains Stephen Watson, John Hart communications lead for BC Hydro. "However, our site investigations and previous drill holes showed that while potentially possible to seismically prepare them by spiralling the ring-girders into the ground, they are ultimately sitting on soil and sand." He explains, "the structures could still liquefy during an earthquake and it was decided to be too great of risk for the investment. We then moved to the tunnel option through bedrock."

The 2.1km-long replacement tunnel will need to carry water at a rate of 124m3/s. Other construction in the project includes constructing a replacement water intake at the John Hart Spillway Dam, a replacement generating station next to the existing facility and a new water bypass.

Following an RFQ issued by BC Hydro in March 2012 the three consortia were shortlisted (see box) for the design, construction and partial financing of the John Hart Generating Station replacement project.

The exact placement of the new generating station and the tunnel design will be determined this fall. BC Hydro has a set date of August 30 for the final John Hart project proposals and financial submissions from the competing bidding teams. There will then be a roughly six-week review period before it announces the preferred team.

After that the two parties will then enter a period of final negotiation before the contract is ultimately signed towards the end of this year.

John Hart

The tunnel will be 60 to 100m below ground and up to 8m in diameter. Some lengths of the tunnel will be unlined while others are steel-lined, particularly where the alignment goes under the earthfill of the John Hart Dam.

"In case there are any fissures in the rock we would not want any upward water seepage," Watson says.

The tunnel will be mostly in relatively massive and unfractured igneous bedrock with hydraulic conductivity estimated to vary from less than 1 x 10-10m/s to about 1 x 10-8m/s. He explains, "Leakage rates over the full length of the tunnel are estimated at 6 litres/hr. There is the potential for some minor and major fracture zones but these are not expected to be extreme."

These zones will be sealed and leakage is considered to represent a negligible effect to groundwater. Elk Falls Canyon is very close to the John Hart site, and runs parallel to the BC Hydro property, which is surrounded by Elk Falls Provincial Park (a Class A park). The canyon has elevation drops of approximately 90m from top to bottom.

The groundwater would move toward the canyon, Watson explains. For the new intake, it will shift about 300m from the existing intake dam to the spillway dam, where the contractor will bore through the concrete dam and then go straight down into the bedrock.

"There is no exposed rock by the existing water intake so it is being moved over to get direct access to the rock. Most of the John Hart Dam is earthfill," he reiterates.

With the proposals process still underway as Tunnels went to press, the method of excavation, or how and where spoil will be removed from the site is to be determined. BC Hydro has calculated that about 290,000m3 (an Olympicsized swimming pool is 2,500m3, so 116 pools) of loose rock materials, primarily from the tunnel, will need to removed from the narrow site.

"One of the unique aspects of the tunnel work will be considerations for ground movement," Watson says. "The existing John Hart facility is very susceptible to ground movement with the dam intake gates that pass water from the reservoir and into the woodstave penstocks.

"To protect the facility these pressure and movement alarms that can shut down one or more penstocks.

"Therefore we would not want ground movement from the boring machine or controller blasting. That will be a significant construction technique challenge."

Looking back to February’s storm event for the existing facility to lose two units from equipment failure-or worstcase scenario up to all six units through such occurrences as a lightning strike- and if BC Hydro can’t get the units back online quickly, it must release water from the dam down Elk Falls Canyon.

"It takes about 45 minutes once the water is released from the dam to travel about 2km to the generating station area to restore the river flow. These kinds of unplanned flow reductions, on average once per year, can impact downstream fish habitat, Watson says.

"That’s why ground movement during construction because of penstock sensitivities will be so important." The project, which is scheduled to be complete by the end of 2018, will create 400 jobs and will see the removal of the original pipelines, letting wildlife and vegetation take over the area