THE TANIWHA'S TAIL.

New Zealand Herald, Volume LXV, Issue 19857, 30 January 1928, Page 10

THE TANIWHA'S TAIL.

ARAPUNI EXPERIENCES. EPISODES OF THE JOB. E'ROSION AND THE FUTURE. WHERE WATER DOES NOT COUNT. In every torrent there is a taniwha which is liable to lash its tail when man comes along with his mathematics to impose mastery. The taniwha of the Waikato at Arapuni is no mythical monster, and it has lashed its tail with some violence on several occasions. Ono of the first furies flooded the uncompleted tunnel and caused delays of a far-reaching character. Then, when the barriers between the river and the tunnel portals were removed by remarkably efficient blasting, the taniwha, still very much alive, lashed again and again and so kept, the violent torrent in the old bed. How it was slowly diverted into the tunnel is part of the groat work of Messrs. Armstrong Whitworth and Company, which is not generally known because the operation lacked spectacular features to all except Mr. Lush, the engineer directly in charge of it, and his men. It was decided to drop gabions—masses of stone in wire-netting "parcels," weighing five tons —into the narrow channel to partially block it and throw the current into the tunnel. Although these gabions were anchored by wire rope into blocks of concrete ; n the cliff, the force of the current was so great that the "mooring" lines snapped and they were carried down, st ream. Over the Spillway. Eventually several of these gabions were dropped in at 0110 time, all being strongly moored, and thus by arduous, pa,tient effort a barrier was raised and more or less sealed by the dropping of large quantities of earth and grit into the water, to fill up the chinks in the gabion filling. When this operation, one of the many fine achievements of Messrs. Armstrong Whitworth and Company, succeeded, the way was cleared for building a tight coffer dam below the barrier and the excavation of the dam foundations behind it. But the turning of the river into the tunnel did not end the reign of the taniwha, nor indeed, the completion of the dam, which rapidly rose to a height of 220 ft. above the bottom of the foundations, to hold back with its dead weight of 200,000 tons a lake of 18 miles. Tiie taniwha lashed again when the river, finding release over the spillway, tore its way through Waiteti Flat and in a few days cut a wide and deep channel representing at least 4,000,000 cubic feet of soil and sand. The Horahora power station a few miles down the river is still fighting the remarkable effects of its fury. Booms caught all the larger debris, but the fibrous stuff—roots, grass and the like—and light pumice floated into the headrace to block the screens through which the water must go to drop into the turbines. Constant labour, manual and mechanical, has been unable to cope with the matter and two or three short stoppages have been necessary, caused in the older machines by pumice passing through the screens and entering them. Horahora's Troubles. The work of coping . with the trouble outside the iforahora headrace gates is going on. The old weir still exists above tho dam that was built later. In this dam there is o section which lias a gate designed to carry away debris, but the old weir has had the effect of holding a lot of it from this overflow. The demolition of the end of this impeding weir is now taking place and'there is*not likely to be any cessation of such precautionary effort, because the taniwha is far from dead and may yet wag its wicked tail to cause more erosion upstream. Until a fresh comes in the river it is not likely that further erosion of the banks of the new channel on Waiteti Flat will take place, but although the ■river downstream is steadily becoming clearer, a great quantity of heavy silt is being carried down from the deep silt bed at tho new confluence. For several miles between Arapuni and Horahora the river is four or fivo feet above normal, because this silt has raised the bed, and there is a possibility of further erosion taking place in the lofty banks at bends where the current attacks their base. A fresh would certainly bring this about and add greatly to the amount of silt already in suspension. The ■ troubles of Horahora, therefore, are not likely to be over for some time, and Hamilton may have to use "thick" water after a fresh on several occasions yet. The taniwha is not yet subdued. Tho Ropeway. One feature of the working equipment of Arapuni, however, must be discouraging to the worst of taniwhas. It is the ropeway stretching nine miles across hill and gnlly to tho Muku quarry. This air transportation highway, ia which there are two circuits, between which the buckets pass automatically, delivered all the crushed metal required for the concrete of the dam, and it is now conveying the huge amount of metal required for the power-house and its foundations. Hundreds of buckets, each holding nearly a cubic yard, are constantly travelling along the ropeway, and one of the most remarkable sights in a launch trip up tlio Jake is the slow passage of an unbroken procession of buckets across it at a point where throe of the wooden towers are now standing in deep water. They travel slowly but they never tire, and thus huge mounds of metal of varying grade# are quickly built up in readiness for tho concrete mixing. Occasionally a man travels from the quarry to the dam in a bucket, and, provided ho is assured that his particular vehicle will not drop off, as buckets occasionally do, above some ravine, he has a wonderful opportunity for calmly contemplating t.lie scenery. It is the duty of one mail to travel the whole circuit each day and oil tho wheels on each tower. Confident and sure footed, he disembarks from a moving bucket at each tower and, screwing down the greasecaps, embarks again on another bucket. His' iob is probably the most unusual in the Dominion: He is a kind of travelling hermit. Ho has no chance, of meeting a soul, except at the terminals. As ' soon as plant at the dam site is dismantled Ihe Public Works Department will, form the road approaches to tho darn, which will then become part of the highway, The department will run a tram track across it and down the road to the power-house site for the delivery of the inetal now bciinr tipped on the east side of the dam. The taniwha can have no influence upon ropeway or tram track.