FIRST TUNNEL

Otago Daily Times, Issue 27521, 16 October 1950, Page 6

FIRST TUNNEL

Work On New Waipori Stations

EARLY COMPLETION LIKELY The final shots of explosive to pierce the No. 4 tunnel for one of 4 the two new hydro-electric power stations at Waipori may be fired before Christmas, and the 3650 ft long, Bft wide tunnel will be completed to the stage where concreting inside it can begin. A statement that this possibility existed provided that the present rate of tunnelling of about 100 ft a week continued and no unforeseen circumstances arose was made to the Daily Times by the works engineer for contractors, Mr A. Kellar, in the course of a visit to the works for the new stations by members of the City Council and departmental officers on Saturday.

The No. 4 tunnel has been driven for 2550 ft, and only approximately one-third of its length—loooft—remains to be drilled, blown, and gouged out mechanically.

The tunnel to serve the No. 3 station has been driven 2850 ft, and 1200 ft remains to be pierced. A start has been made on driving the shaft 30ft into the other end of the tunnel as one of the preparations necessary before the final blasting stage is reached.

While the tunnelling at the No. 4 station is' in progress for 24 hours a day, six days a week, preparations are being made for the construction of a dam below the tunnel in the Waipori Gorge. Trial holes have been sunk there to test the foundations, and an access road to the site of the proposed power station and the dam has been excavated and is being metalled with spoil from the tunnel. The visiting party from the City Corporation saw the tunnellers at work at the face of the No. 4 tunnel after they had travelled into the shaft on a trailer attached to the electric storage engine. They sa<v the JaySullivan hydraulic drill jib in action, sending steel bits Seep into the face of the rock to allow explosives to be inserted for firing, and also the installations outside the tunnel which enable the work inside to continue—the compressors sending air to the machines and drawing contaminated air from the face, the workshop in whicn the drill rigs are serviced and drills are sharpened for use again in suitably soft formations, and the wide scarf of spoil poured down the hillside after .excavation from the tunnel. They were told that the actual excavation work done by the contractors for all purposes—to establish roads, camp sites, and levels for new surge tanks Eftid stations, as. well as from the tunnels—totalled 80,000 cubic yards, of ■ which 30,000 yards was for the actual project, and the remainder was to facilitate progress with the works. The contractors told the Daily Times that it was hoped that the No. 4 dam, which is to hold stored water to a level of 60ft, would be completed before the end of next winter, and the No. 3 dam would probably be completed before the end of next year. At the No. 4 station site, the councilors saw a mechanical grab shifting boulders from the bed of the Waipori River to clear the way for the construction of the dam, and also saw the trial hole which had been sunk to prove the foundations.

When the tunnels have been bored, the next task will be the concreting of the interior, using steel moulds. These are placed in position inside the

tunnel, and concrete is blown with compressed air guns between the tunnel and the metal. When the cement is set to the required standard, the moulds are moved and the process is repeated. The concreting of the tunnels is expected to take about six months.

The members of the City Council who made the trip to Waipori on Saturday were the chairman of the Electricity Committee and Deputy Mayor, Cr Wright, and Crs Hayward, Barr, E. J. Anderson, and Smith. Cr Smith was the only councillor present who is not a member of the Electricity Committee. The departmental officers present were „the city electrical engineer, Mr G. T. Edgar, his deputy, Mr A. H. Dickson, the town clerk, Mr J C Lucas, the deputy town clerk, Mr F. R. Grindley, the superintendent of reserves, Mr M. R. Skipworth, and Mr K. Morrison, records clerk. The party was met at the No. 4 station site by the district manager for the contractors, Mr F. J. Handcock, Mr Kellar, the engineer at Waipori, Mr F. Collins, and members of the staff at Waipori. The inspecting engineer for Lancaster and Vickermann, Mr M. Peerles, was also with the party. After inspecting the new works, the visitors saw through the existing No. 2 station before returning to Dunedin. i