had been completed to a stage that a firm date of 1 July had been selected to attempt the diversion the flow had increased to . Extra bulldozers were allocated to the attempt as the steady increased to and then . If the diversion couldn't be completed before the peak winter flows the project would have incurred a delay of between nine and twelve months. Despite studies that had indicated that the conditions were less than optimum Arnold Downer made the decision to go ahead. Using twelve bulldozers sufficient accumulated earth and rocks was moved at a rate of over twelve hours on 1 July 1954 to successfully divert the river into the diversion channel. With the river diverted, cofferdams were constructed upstream and downstream of the dam and the water pumped out between them. The upstream cofferdam consumed of material, while the downstream cofferdam consumed of material. There were expectations that gold would be found in the exposed river bed, but despite the MOW taking out a mining licence and employing two experienced gold miners, the results were disappointing. Once free of water work commenced on the excavation of the foundations for the main block of the dam. A large gravel filled hole was discovered in the centre channel or "gullet" of the river bed. This gullet which was deep and varied in width from 50 ft to was dug out and filled with a mix of pozzolana (fly ash) and cement under the dam while under the powerhouse Prepakt concrete was used as this reduced demand on the batching plant which was fully occupied supplying concrete for the dam blocks. In July 1954 Downer replaced 20 senior contractor staff that he had inherited with people of this choosing, many from Morrison–Knudsen Co. A significant appointment was that of A. I. Smithies, a very experienced hydro construction engineer from Morrison-Knudsen as construction superintendent. With management in place the workfare was able to be reduced from the 1,107 when Downers took over, to 850. Under Downer's management the pace of construction increased with the weekly concrete pour rapidly improving. In the first week of October 1954 of concrete was poured, which had increased to poured over the course of the next week. By May 1955 the project was meeting its target dates with work on the powerhouse six months ahead of schedule. The dam was constructed in wide concrete blocks