HUGE TUNNEL

Auckland Star, Volume LXXV, Issue 57, 8 March 1944, Page 6

HUGE TUNNEL

KARAPIRO SCHEME

START ON DAM SOON

(0.C.) HAMILTON, this day. Approximately 500 men are employed on the huge hydro-electric undertaking at Karapiro, on the Waikato River, six miles from Cambridge, and the work is progressing as fast as possible with the amount of manpower and material available.

The principal task that has been engaging attention recently is the de-watering of a length of the river bed that has been drained by diverting the water through a huge tunnel which extends over 1000 ft.

Coffer dams have been built in the old river bed opposite the tunnel intake and at the outlet, and major leaks have been plugged. Powerful suction pumps were fitted to pump the water out, sealing being carried out as the water was displaced. Today there is very little water seeping in, except from near the lower coffer dam. Here the water comes in at about 2500 gallons an hour, and the objective is to reduce this inrush to not more than 1000 gallons hourly.

With the river bed practically dry, work will be concentrated shortly on the construction of the huge dam, which is estimated to require a quarter of a million cubic yards of concrete, with many hundreds of tons of steel reinforcement.

The Karapiro diversion tunnel differs in shape from all the other diversion tunnels in the Dominion's hydro-electricity schemes. It resembles the outline of an egg standing on its narrow base and has been described as U-shaped, but actually its greatest width is at about twothirds of its height. It then tapers gradually to the base.

IVJanpower has been, declared by the authorities to be the greatest difficulty to-day, but inquiry on the job confirms the opinion that it is not so much a matter of manpower as of selected manpower. Very few more unskilled men are needed at the present stage of progress, but more men skilled in such work as operating winches, driving bulldozers and trucks, handling popper drills are wanted. Probably up to a hundred more men could be usefully employed if the work is to proceed according to schedule.

Karapiro's Output

All the men from the engineer in charge, Mr. I. T. Gilkison, right down the roll of skilled men to those who are not even skilled with pick and shovel, seem keen to help in bringing the job to completion.

The Karapiro plant will be capable of producing at least two-thirds of the total output of Arapuni, which produces 110,000 kilowatts with six units: Two additional units at Arapuni will complete that station at 150,000 k.w. It was hoped that one of these new units would be in operation by next winter, but the latest indications are that this hope was optimistic.

No date has been set for commencing the delivery of power from Karapiro, as there are many obstacles, manpower and the shortage of materials from overseas being the principal ones. Officials of the Works Department are intent on making electric power available from Karapiro by the end of 1946.

The most modern machinery obtainable in the Dominion, some of it unique, has been and is being installed. A feature on the landscape is the huge plant for mixing cement, sand and metal into concrete and delivering the finished product in a continuous stream so that when the actual construction work starts on the dam there will be no avoidable delay.

As construction proceeds work will also be hurried along on. the erection of the power house and the housing for the huge turbines.