Coega is again making history, with the casting of the biggest dolosse on the African continent.The first of the 26 500 thirty-ton dolosse that will be used on the two breakwaters for the deep-water harbour of Ngqura have already been made. According to Deon Retief, the partner responsible for the Nqura breakwater design at Prestedge Retief Dresner Wijnberg, the dolosse will form the top layer of the main breakwater which, at 2,5 kilometres long is the “largest by far” in Africa. The base of the massive breakwater, at its deepest end, is wider than the Newlands rugby field, while a temporary two-lane highway will be built on its crest to allow special transporters to carry the rock and dolosse that are being used in the construction. Two massive cranes tall and wide enough for two 40-ton tipper trucks to pass under will straddle the breakwater. Every one of the two storey high dolosse will be carefully put in place, with the crane driver being guided by a global positioning system (GPS) fitted at the end of the crane boom. “The operator will have an electronic printout in the cab which will give the specific co-ordinates for each dolos,” he says. The placing of the dolosse has been calculated using a scale model of the Coega port that was built at the CSIR in Stellenbosch. Covering about three tennis courts, the model has been used to simulate all weather conditions in Algoa Bay and at the Coega harbour. The Dolosse will be placed on a layer of protective rocks weighing between three and six tons each. They, in turn, will rest on a base of core material made up of rock graded from 5kg to 3 ton. Another first for the construction will be the placement of a giant 12 700 ton caisson at the end of the breakwater. The concrete caisson, which will be as wide as a rugby field and 20 metres high, will be cast on shore and floated into place, before it is filled with sand. Four smaller caissons will be used on a secondary breakwater for the harbour. According to Retief, a full production line with a dedicated batch mixing plant is being created at Coega in order to produce up to 52 of the giant dolosse a day. Vibrators will also be used to ensure that no air is trapped in the concrete while it is setting. He expects the placement of the dolosse on the breakwater wall to start soon.