CT terminal upgrade – it’s a blast!

IN PREPARATION for a larger generation of vessels, huge quantities of explosive are being used to blast hard rock from the container terminal basin in Cape Town, it was revealed last week. The blasting will be mandatory in order to effect a new depth of 15.5 metres at berths 602, 603 and 604, and according to Canadian engineer John Simmonet, “a lot of blasting using quite a lot of explosive”, has been going on since February. Probably the only reason Transnet National Ports Authority has not been flooded with angry calls about the noise factor is because there is none. “Underwater blasts are quiet,” explains Simmonet, the berth deepening project manager from Hatch, an international engineering company sub-contracted by Transnet Mega Projects. How the operation, kickstarted last December, works is that a suction dredger ‘inhales’ softs, such as sand silt and clay, while a backhoe dredger takes care of hard material, for discharge at a predetermined 40-metre deep dumping ground northwest of Mouille Point lighthouse. Maintaining its position in the container terminal basin is a local barge, equipped with three drills suspended over the side, each of which prepares three holes. Once they are completed, the barge is held fast by anchors while divers place explosive charges within the holes. The vessel then moves approximately 60 metres away before the explosives are electronically detonated from the vessel.