BC Hydro completes construction on cavern for new billion-dollar generating station

After 13 months of excavation and nearly 500 rock-blasting detonations,BC Hydro has completed a giant cavern that willhouse a new power plantnear Campbell River.

It is the biggest component of the $1-billion John Hart Generating Station Replacement Project, whichbroke ground in 2014.

When completed in fall 2018, according to Hydro spokesman Stephen Watson,the facility will provide 132 megawatts of electricity, which is about sixper centof Vancouver Island'speak electricity demand enough to power up to 80,000 homes.

About 350 workers have been employed on the project.

"This project is dealing with seismic concerns and reliability issues,"Watson said in an interview withCBC Radio On the Island host Gregor Craigie.

"It's all in bedrock and it's very impressive to see."

BC Hydro blasted the new powerhouse cavern through solid rock after discoveringthe original dam, built in 1947, would not withstand even a moderate earthquake.

Another benefit of the new facilityisprotectingfish habitat in the Campbell River from "unplanned flow events,"Watson said.

"With the water bypass facility in place there, if the turbines do go offline you can quickly divert that water flow and maintain fish flows downstream," he said.

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An incident during construction in fall 2015underlined the need for improvements.BC Hydro saysblasting unexpectedly caused one generator to shut down and reduced water flows in the river below the minimum level of 80 cubic metres per second.

The Crown corporation stated that the generator was restartedwithin 30 minutes and flows restored, with "minimal to no impacts to fish."

Hydro's original plan was to replace the wood-stave-and-steel penstocks, which control the release of water from the dam, with steel and ring girders, but Watson said seismic concerns meant it would have been expensive.

"It became just as cost-effective to put it underground in rock," he said.

Project managers SNC-Lavalinalso came up with theplan to move thegenerating station, currently located along the river, below ground as well.

The excavation is eight metres wide,as deep as a 10-storey building, and 93 metres long the length of an NFL football field,Watson said.

"It's kind of like the project of a career. Even on Vancouver Island, it's rare to see a project of this size."

Above ground, Watson said the new facility will blend better with the adjoining Elk Falls Provincial Park.

Once the generating station is completed, BC Hydro expects to move on to upgrading the John Hart Dam itself, starting as early as 2019.

With files from On the Island.

To hear the interview, click on the link labelled: Billion-dollar Hydro project reaches milestone