How they knocked down the second tower at John Hart Dam
The second of three surge towers at the John Hart Dam was knocked down on Thursday morning using explosives.
It’s part of decommissioning efforts for the 70-year-old power station near Campbell River, which has been replaced with a $1.1-billion generating station.
The 90-metre tower was felled at 9:24 a.m., when explosives attached to some of the base girders of the centre John Hart surge tower were detonated.
A 450-metre safety radius was created around the surge towers to block public or worker access leading up to the blast, said B.C. Hydro spokesman Stephen Watson.
The decommissioning is being done by contractor InPower B.C. , with FMI/ASL-JV and subcontractor Pacific Blasting and Demolition leading the surge tower removals.
The felling included cutting some of the eight supporting girder legs and then attaching linear shape charges, with kicker charges used to ensure full metal separation and displacement, to two other girder legs.
Watson said the third tower, while not part of the new hydroelectric facilities, is in good condition and is expected to stay in place, since it contains communications equipment, has heritage value and is a visual aid to the local airport.
The white towers were in operation from 1947 to 2018, and protected the 1.8-kilometre-long penstocks that led from the dam to the generating station from short-duration water-pressure changes that occur when the flow velocity is increased or decreased. They do this by allowing the water to go up, or come down.
The surge tanks were half-filled with water and at the same elevation as the upstream John Hart Reservoir.
The old John Hart facility was officially shut down last fall and replaced with a new and improved underground hydroelectric facility that’s expected to better withstand an earthquake.
Steel from the towers is expected to be recycled.
