THE ARAPUNI DAM.

Otago Witness, Issue 3803, 1 February 1927, Page 16

THE ARAPUNI DAM.

WORK NEARING COMPLETION., AUCKLAND, January 26. The colossal construction work at Arapuni has now entered its final phase. The engineers attached to the staff of the contractors (Sir W G. Armstrong, Whitworth, and Co-) are. no longer fighting the river god at the dam site. The victory has been theirs, and in the peace that h as followed all brains and hands are turned to the constructive tasks of building before the concrete can be poured in for the construction of the huge dam. The bed of the river has to be deepened •30 feet to carry, the foundations. This work has been partly completed, and the first few yards, of concrete mixture are being permitted to set, but a good deal of rock has still to be excavated before, the concreting can start in earnest. ■ At present the Waikato plunges through the diversion tunnel with no obstacle to its progress, but before long it will bo possible to shut or open the huge underground passage at. will. Control will be. effected by two gigantic sluice valves completely closing the tunnel when necessary and turning the river back into its old channel and heaping up the waters behind the dam. Sluice valves are situated about 100 feet inside the tunnel from the intake and will be operated from the surface through a shaft which has already been sunk and lined with concrete. It is a rectangular hole 38ft 6in by Bft. Workmen are now engaged fi converting it into two by the insertion of a concrete dividing wall down the middle. In each of the shafts-so formed hydraulic lifts will be installed working in cylinders for the purpose of lifting and lowering the gates into the diversion tunnel. : 'i ■■

The gates, of which there are two, each weigh 27 tons. They are of steel 2ft thick and measure 21ft 6in by- lift 9m. These weighty objects have already been, lowered in parts into the shaft ana. assembled, and" they now rest on steel girders 35ft above’ the water plunging thrdugh the tunnel. When the lifting gear is installed it will be possible to take, the weight off the girders and remove them, permitting the gates to be lowered, at will into the tunnel,, closing it completely, or partially, according to the depth to which they are allowed to descend. Then the . river waters will pile behind the dam and submit it to a test which will pronounce judgment on the work of years.