MAKING ARAPUNI SAFE.

New Zealand Herald, Volume LXVII, Issue 20615, 14 July 1930, Page 12

MAKING ARAPUNI SAFE.

Sir, —A few weeks ago tho Arapuni "scare" became the main topic for conversation throughout this Dominion. Governments at the conception, birth and infancy of Arapuni and their engineers were blamed for what was termed the grand fiasco. Criticism regarding Arapuni up to the present has been 99 per cent, destructive. In the Herald of July 3, there appeared tho views of an engineer that formed most pleasant reading: a brilliant light began to appear through this pessimistic fog. The securing of electricity from Arapuni has been tho greatest hydro-electric engineering feat ever attempted in this country. It is difficult, if not nigh impossible, to overcome Nature, and, to my mind, the complete diversion of the river from its natural course has been tho whole cause of the present trouble. When one considers the enormous weight of water in motion between the dam and the penstocks, coupled with the vibration thus created and the weakness from tlie other side caused through the power-house, excavations, it is surprising that the present trouble had not arisen sooner. Add to these another agent, so manifest below the spillway, viz., erosion, and it seems clear that tho day was not far distant when the liver wo' ld have again returned to her natural bed beside the dam. Tho solution offered bv the engineer in the | Herald of July 3 had occurred to mo ; during a visit to Arapuni a few weeks | ago, with the exception that I did not ! consider steel tunnelling necessary. The ! two problems to be solved are: (a) Tho I taking of sufficient water to the penstocks to drive the generators; (b) the disposing of surplus water at the dam. 1 beg permission to offer the following solutions:— (1) Construct a miniature dam immediately below tho bridge that spans the diverted river at sufficient height to prevent an overflow from the lake and, at tho samo time, allow the tunnel or tunnels required for the generators to penetrate; tho tunnel or tunnels to rest freely on tho bed of tho diversion in concaved formation. No permanent union or construction should exist between tunnels and bed: this will permit of slight oscillation in time of earthquake shocks or disturbances. Thon construct a concrete wall from the spillway, parallel to penstocks to form a reservoir so as to ensure evenness of pressure. The above immediately disposes of two agents that have caused the trouble, viz., erosion and vibration, and minimises the third, viz., weight of water. (2) I disapprove of suggestion to put a lip in tho dam and a deposit of large rocks to break the fall. I suggest tunnelling the dam in several places for one set purpose, viz., to keep water at penstocks even. A lip in the dam would be a disfigurement and rocks to break tin fall would be immaterial unless x raised at a considerable height, which would be another disfigurement. T suggest tunnelling the dam at required height, then terrace off. 1 further suggest, the placing of lights (varied colours) on each terrace. An ordinary stairs will help as an illustration: verticals glassed in, electric lights at back of verticals 'the water coming over said terraces or steps will fonn a most attractive sight, especially if lights are coloured, and at night time the sight would bo one of enchanting beauty Then these steps or terraces formed into the face of the dam will break the water and preserve for all time the dam itself. 1 have seen similar tricks in Russia, Serbia. Austria and Germany, and the effort is most attractive. The above two solu j tions will save: (a) Concreting beyond (he spillway, and anxiety regarding powerhouse, which is already secure provided that no undue pressure is brought to bear. I have thoroughly gone into the matter and 1 fail to see how it can be what sonio think: a great fiasco. Auckland Province requires electricity; therefore, it is up to every man to use his brains and see that she gets it. Let us work not for the destructive, but a constructive. policy, and those who have nothing to offer in advancement should remain silent. The time is not now when we can afford to blame anyone. We are in a crisis, and in a crisis the motto is: "help each other." Ivan Black. Matamata.