THE ARAPUNI TUNNEL

Waipa Post, Volume XXIV, Issue 1639, 9 May 1925, Page 5

THE ARAPUNI TUNNEL

OVER 500 FEET FROM OUTFALL,

The construction of the Arapuni hydro-electrical works is proceeding now at high pressure. Energy is being concentrated particularly on the driving of the river diversion tunnel, which is the most important preliminary to the erection of the Arapunfcdam. The Putaruru Press says the top half of the tunnel is now in over 500 feet from the outlet end and the bottom half is in oyer 100 feet from this end. From the intake end the top half is in about 10 feet or more. Wednesday of last week was a record day up till then for the amount of work done in the tunnel. Tiplers—a special kind of tip truck—have been purchased from the Taupiri mine and are being used for this job. Above the intake end of the tunnel a shaft is being driven into the cliff for the purpose of later blowing down the bluff to block the river and divert the water into the tunnel. This brings appreciably nearer the day when the tunnel will be completed and the river diverted into it. The method used will be to complete the tunnel with the exception of a few feet helow river level at each end. This Temaining barrier i s technically called “the dumpling.” It will be undermined in each case and blasted away with explosives. This, together with the temporary damming of the river by the blasting down of the bluff, will be responsible for turning the river into the tunnel and leaving the dam site dry. At a point 140 feet in from the intake valve comprising two water tight gates is to be installed in \.th© tunnel. This will be used for regulating the flow of the river through the tunnel and will be operated from the ground level 150 feet above. The necessary shaft from this level down to the valve site is now being sunk. A start has also been made with the •construction of the suspension bridge for pedestrians across the gorge to the powerhouse site, and the concrete i foundations for this bridge have been laid.