the tunnel, the 1960 Quarries Act allowed a diesel engine fitted with scrubbers to be used and had no requirement for the workings to be open end to end. Having identified that it was more advantageous than digging from Lyttelton, Fletchers-Kaiser dug the tunnel from the Heathcote end. Fletcher-Kaiser employed Burnett Motors of Ashburton and Isaac Construction of Christchurch to excavate the 1¼ mile (2 km) long approach road to the tunnel from the nearest road at the bottom of the Heathcote valley. Work on digging the tunnel had been underway for a month with excavated by the time the ceremonial 'firing of the first shot' to officially signal work on the tunnel took place on 9 September 1961. Within a short time the tunnel was progressing at a rate of per day, working three shifts, six days a week. The tunnellers received a basic hourly wage of 7s −2d per hour. Despite the use of water exhaust scrubbers on the diesel-powered excavation equipment it was still found necessary improve the ventilation by locating near the rock face two 200 hp 5 ft 6 in diameter fans capable of exhausting 100,000 cubic feet per hour via a flexible diameter flexible plastic pipe to the portal. Although by the time the tunnel having reached the 60% point it was found that the clearing of flumes and smoke was becoming a problem. Despite the use of several auxiliary fans it was found necessary to drive a small by ventilation tunnel for the Lyttelton end to connect with the main heading. Once the connection had been made at the from the Heathcote end one of the main ventilation fans was moved to the Lyttelton end. Despite the cost of driving the ventilation tunnel, it was found that it speeded up the driving of the main tunnel by allowing a more effective cutting, reducing the amount of explosives being used and more quickly clearing the smoke and flumes after blasting. It was found necessary to support with steel framework only 8% of the tunnel due to unstable ground conditions. In all other areas, either rock bolts or a combination of steel mesh and sprayed concrete were used to restrain potential loose rock. A total of 1,400 rock bolts were used. Despite being delayed by wet weather at the start of the work the excavation of the tunnel was completed on 18 August 1962, within