VANCOUVER -- Fifty-odd years ago when the provincial government wanted to build the massive W.A.C. Bennett Dam, the regulatory process was a "day and a half of hearings, then the shovel went into the ground," said BC Hydro's Susan Yurkovich.
Such haste to use the rubber stamp and get things going wouldn't work these days. So far, the oversight process for the proposed $8-billion Site C dam in northeast B.C. has been grinding on since August 2011 and it could be another six months before the environmental assessment review runs its course.
"It was a different world back then," said Yurkovich, the utility's executive vice-president. "Today it's a very different process. People want to make sure the project has gone through a rigorous environmental assessment and they want to make sure (effected) communities are consulted."
Public discussions involving the dam have been underway for more than seven years, she said.
If Site C clears all the regulatory hurdles, the first shovel to strike the ground will be next year and the largest civil engineering project undertaken by Hydro since the completion of the Revelstoke Dam in 1984 will begin.
At that point, Andrew Watson, BC Hydro's engineering division manager, and John Nunn, the chief project engineer for Site C, can get to work turning their blueprints into the fourth-largest dam in B.C.
Site C would complete the network of dams on the Peace River, making it the third on the river along with the W.A.C. Bennett Dam and the Peace Canyon Dam and would use up the last of the river's potential to generate power. The proposed site is near Fort St. John and could be operating by 2024.
"It will be the last dam on that river," said Nunn.
Both Watson and Nunn were part of the team that designed Site C.
"The design has a long history and we have the benefit of the investigations that have happened over that time and are able to incorporate the results into a modern design," said Watson.
Sitting in an enormous laboratory in Montreal is a scale model of Site C with its miniature dam, spillway, reservoir, approach channels and a portion of the upstream river. It allows Hydro's engineers to run water through it and check flow velocities and compare the results to computer-generated data to make sure the design of the all-important spillway is correct.
The spillway is there to protect the dam in the eventuality of levels of flooding significantly greater than has been recorded on the Peace River and will allow flood water to exit around it.
The dam will be about one kilometre in length and 60 metres high -- about a third of the height of the W.A.C. Bennett Dam.
It will be an earth-filled dam whose powerhouse will produce 5,100 gigawatt hours of energy a year, enough to serve the needs of 450,000 homes.
The biggest engineering challenges involve the spillway and the sheer scale of moving 26 million cubic metres of rock and soil around the site.
"It's more like a mining project in a sense that you are moving vast quantities of material, overburden and rock. From a construction perspective, the logistics will be a challenge," said Nunn.
The first phase involves the excavation and construction of two 10.8-metre-diameter concrete-lined tunnels -- 700-metres long -- and two coffer dams that will divert the river's flow into those tunnels.
This will move the river away from the area where the dam, spillway and the powerhouse will be built.
The spillway and powerhouse will be built on roller-compacted concrete foundations in which the concrete is set in place using trucks, bulldozers and large vibrators to compact and improve its seismic withstand, said Watson.
"Once the earth-filled dam is complete, the powerhouse and the spillway complete, we'll go through the sequences of reservoir filling where we will sequentially close the diversion tunnels, allowing riparian flows to continue downstream," said Watson.
"We will make sure we are not harming the fish in the process as any changes in water pressure could give them the bends. We will then bring the reservoir up in stages and then commission the unit and finish the project," he said.
The spillway will be the largest in the province.
"It's a rare opportunity to design such a large one. The hydraulic design of these structures is always interesting because they are always unique. It's got a number of redundancy features. It's got an auxiliary overflow spillway and so if all else fails in our main gated spillway we can safely pass floods through the overflow," said Watson.
There will be six massive turbines in the powerhouse, each 12-storeys high, said Nunn.
The pipes carrying the water to these turbines could hold a three-storey house inside.
"What I find fascinating is when you get inside a powerhouse and erect these very large machines, the shaft between the turbine and the generator, I couldn't put my arms around it. It would take three people all stretching to do that," said Nunn.
"They build these machines to very exacting tolerances -- we are talking about thousands of an inch -- but that's where the rubber hits the road; it's where the water creates the energy," said Nunn.
Site C dam: The facts
Type: Earthfill dam
Height: 60 metres above the riverbed
Length: 1,050 metres
Energy: 5,100 gigawatt hours/year
Capacity: 1,100 megawatts
Reservoir:
Total surface area: 9,330 hectares
Total land flooded: 5,550 hectares
Length: 83 kilometres
Width: two-to-three times size of current river
Source: BC Hydro
