A second surge tower at the defunct John Hart dam in Campbell River was knocked down on Thursday morning.
At around 9:24 a.m., explosives attached to some of the base girders of the centre John Hart surge tower were detonated.
The 90-metre tower was felled in the same way as the first tower on July 12. Some of the eight supporting girder legs were cut and then attached to linear shape charges, with kicker charges used to ensure full metal separation and displacement, to two other girder legs.
Leading up the blast, there was a 450-metre safety closure radius set up around the surge tower.
The third tower will remain at the dam due to its communications equipment, use as a visual aid to the local airport and heritage value.
The towers were in operation from 1947 to 2018 and protected the 1.8-kilometre long penstocks, which 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 conversely 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 in October 2018 and the final touches on the new underground hydroelectric facility are being completed.