As the new generating station at the John Hart comes together, what used to be a 40 metre deep hole in the ground is slowly being filled with the supporting platforms made of rebar, wooden frames and concrete.
The cavern that is as tall as a 10 storey building and as long as a football field, according to Stephen Watson stakeholder engagement advisor with BC Hydro, was completed in May. The primary access tunnel was completed in August, but the work is nowhere near over.
It took 13 months and 485 blasts to fully excavate the cavern, Watson said. 60,000 cubic metres of rock was removed from the site.
“It takes a long time to do everything when it is underground,” said Paul Sawyer, CEO of InPower BC the contractor for the project.
For example, getting concrete down into the cavern is a multi-step process. Sawyer said that the cement is unloaded into buckets, and lowered to the work site with the crane. The empty buckets are sent back up and the process begins all over again.
But one of the most time consuming parts of the project is the construction of the tunnels. Sawyer said they can only be built five or six metres at a time, as the equipment operators are not allowed to progress into areas that are not secured. The crew drilled into the rock and inserted explosives. The rubble would be removed, shotcrete applied and reinforcements added, and then the workers and equipment could advance and start the process all over again.
Sawyer said one five or six metre section can be completed a day.
Considering there is a 1,575 metre power tunnel from the reservoir to the powerhouse, a 520 metre tailrace tunnel, a 384 metre main access tunnel and a 116 metre service tunnel, it is no wonder the project is expectded to take four years and cost $1.093 billion.
Watson said there are around 350 people working on the project in Campbell River.
Everyone working and visiting the underground facilities carries a self-rescuer.
If there is ever an event underground that produces carbon monoxide, workers can breathe through the rescuer while they head to the surface. The device converts dangerous carbon monoxide to breathable carbon dioxide.
Everyone entering the tunnels also wears a tracker that indicates when entering and leaving the project site instead of physically signing in and out. Ear plugs are also required as the air ventilation system is quite loud.