SCIENCE TRIUMPHS

Shannon News, 14 August 1923, Page 3

SCIENCE TRIUMPHS

In the Heart of the Bush PANORAMA OF MANGAII AO. Up in the hills and valleys above Shannon, away from the wonted paths of civilisation, amid the primeval uush, one of the greatest engineering propositions that has been undertaken in New Zealand is rapidly proceeding towards completion. The small army of workers on the Mangahao hydroelectric scheme, after many months of unremitting toil have at last< brought their task to its final stages, but much yet remains to be dono. The prediction that “juice” will be available by June appears to be in a fair way to being realised, provided that Nature does not present any further obstacles to the engineers. Accompanied by Messrs W. A. Waters and K. Eglinton, of the Mana-watu-Oroua Power Board, a “Times” reporter paid a visit this week t'o Mangaliao, where the work of harnessing the river god is now at a most interesting stage. The two great tunnels have been pierced, and the construction of the dams at* Mangahao and Arapeti has been commenced. Soon the huge concrete ramparts will be erected, the by-pass tunnel which now diverts the stream from its normal course will be blocked, the dams will fill up and the power will be ready!

Shall we ? THE POWER-HOUSE AREA.

On arrival at Mangaore, the party was given its first indication of the magnitude of tho undertaking. The power-house that is to convert the water into heat and power is rearing up it's walls, and already 7000 yards of concrete have been used in the floor and water chambers alone. Five engines, three generating 6000 h.p. and two 3000 hp, will be installed when the shell is complete, together with an exciter.

The pipe line, which will convey the water from tho surge chamber 900 feet above the power-house, is now being laid, the pipes being three feet in diameter. Difficulty in the matter of supplies has kept this work back

somewhat, but it should be completed according to schedule. A simple illustration {if the enormous power that lies latent in a small quantity of water was supplied by Mr Waters to our representative. An oil drum containing 5 gallons of 60lb

weight, with a fall of 900 feet, will 1 generate one horsepower for a minute. I The journey to the Arapeti camp is I still dangerous, especially in wet I weather, and all the thrills of the 1 Wonderland switchback are provided i as the motor car mounts spirally, with

J deep, precipitous gullies on the one I hand ..nd towering cliffs on the other. I The he n vy traffic makes maintenance ‘ work difficult, and considering the number and sharpness o.f the. “hairpin” bends on the road, which in some instances have to be negotiated by degrees, surprisingly few accidents ( have occurred.

A TREACHEROUS ROAD. At one part of the road, however, the chassis of a motor lorry bears mute witness to a recent smash, and a glance down the side of the hill reveals the broken body—a pile of matchwood. The driver of this vehicle escaped miraculously with a bruised hip. There was something for congratulation on the day of this accident, however, by tho people of the camp. The children, who live at some distance from tho school, which is held in the Y M.C.A. hut, are every morning and evening given a lift by the driver. On this occasion, however, he had been forestalled by another truck which preceded him. if the ten children who usually travelled by it had been in the ill-fated vehicle, the camp may have had to mourn another tragedy, even more poignant than that of the tunnel, in which 3even men lost their lives. On another occasion, a party of four was proceeding from Arapeti when the car slipped, for several seconds being posed on the brink of a cliff about 100 feet high. Another car coming behind raced recklessly to the rescue, but too late. On e of the occupants of the rear seat, who turns the scale at 14 stone, jumped clear at a bound, and the releasing of this weight on the rear wheels was sufficient to send the car hurtling down on to the section of the road below. Here, again, however, there was a miraculous escape, the three remaining members of tho party who "went down with the ship" esaap-

ing with sundry cuts and bruises. With ] the relating of such incidents, (told, perhaps for a specific purpose, it is little wonder that the visitor heaves a sigh of relief when the track has been successfully negotiated. WORKERS’ SETTLEMENTS. Since a previous visit, nearly twa years ago, the reporter noticed that many improvements had been made in the housing of the workers and their wives and families. The canvas huts had been replaced .by substantial wooden structures,. which are very cosy, and as convenient as

one could expect in such circumstances. They axe gathered together in little colonies wherever a section of the scheme is under way, and the fact that it was washing day gave them an air of homeliness that was not discounted either by the heavy, brooding forest on the one hand, or by the insistent echo of a steam hammer on the o cher, THE AKAPETI DAM. Practically all the labour at Arapell is now concentrated on the construction of the great dam, which will have a capacity of 300,000,000 gallons. As wai me case with the Mangahao dam, much difficulty was experienced in - finding a solid rock face in which the walls of the reservoir will be set, and both sides of the hill have had to be cut back, one about 400 feet and the other about 100 feet. A wooden flume, supported by concrete piers that will eventually form part of the wall of the dam, carries the water across the gully, while underneath the rock surface, having been thoroughly washed of all loose dirt and rubble preparatory to the laying down of the concrete, is now rapidly disappearing as the final part of the construction work is begun. In a few weeks, the great rampart, about 100 feet thick at the base and 300 yards long, will be ready to hold the enormous pressure of water which will flood, perhaps, for all time, the valley which is now the home of this division of the Public Works’ army of Mangahao. A short journey along one of the enormous tramlines brings one to the tunnel which connects up with Mangahao, while the longer tunnel to the surge chamber above the power house, is some distance to the right. The concreting of these is being pushed on with all speed, as fast as the cement arrives. ON THE MANGAHAO. Leaving Arapeti behind, another journey over an even more execrable part of the road, brings one to the hill overlooking the last great link in this gigantic chain —the Mangahao catchment area. The'steep descent to the valley is made by a narrow bush track. Roadmaking further than the top of the cliff was plainly impossible, so the famous jigger line was install* ed aud by this all goods are let down and hauled up on a gradient so steep that from the opposite side of the valley it looks perpendicular. Joyriding on the “jig” is strictly forbidden, which some dare-devil spirits regretted, Only sick men unable to negotiate the arduous track are perTHE COMING OF HYDROELECTRICITY.

permitted this thrill and then, of course, they are 'in no mood to appreciate it.

“Only once in 2J years,” so said a Public Works’ man, “has the jigger broken loose. On that occasion, the rope broke and the down truck weighing a ton, dropped into the

stream. No! nobobdy was near at the time, fortunately.” DIVERTING THE STREAM. Two suspension bridges, one a very substantial affair, have been constructed over the stream, but before leaving the near side of the valley, a visit must be paid to the other mouth of the tunnel that connects in a straight line, with Arapeti. It is a mile long, and eight feet in diameter. An interesting object is the boiler which generates the power. This weighs ten tons and the problem of transporting it was a ticklish one — but not beyond the resources and ingenuity of the engineers. Just underneath the first bridge the stream has been dammed and the water diverted through the by-pass tunnel, the construction of which took a year, and was a most, expensive, but necessary, part of the programme. Some water, however,

still percolates through the fascine, and a “naval brigade,” on a large armed with a powerful steam hammer, is engaged in driving four lines of steel piles to hold the water at bay should heavy rain bring a. torrent swirling down, which, avoiding the legitimate outlet, will endeavour to rob the engineers of the fruits of. their victory over Nature before the foundations of the upper dam can be laid. Up to the present, however, very little difficulty has been experienced with floods. RATNFALL IS HEAVY. While we are on the subject of floods, some statistics relating to the rainfall will be apropos. In 1921 the fall totalled 109.49 inches; in 1922 it amounted to 89.28 inches, while that for the present year bids fair to eclipse both. From January to July the amount that fell was 64.15 inches; 45.51 inches fell for the corresponding period last year. It ;s to be noted that the actual fall in the catchment area is probably heavier than those figures denote, as the records were taken in a comparatively sheltered spot.

DIFFICULTIES CONQUERED. As mentioned above, the same difficulty in finding - a solid l’ock face has been exeprienced at the Mangahao dam as at Arapeti. The contractors disco-.reed, to their c. si. tha! what had appeared to be a solid rock face was but 20 feet thick and beyond that in the hill-sid'e was an old bed of the stream, which had silted up in the course of countless ages as the river wore out a new bed to the 1 eft. The' hill has been pierced to a distance of 200 feet on the one side, and 6 feet on the other. One large wing- wall of the dam lias already been built, and when completed it will be 90 feet thick at the base, 10,0 feet across at the bottom, and th<s water will be 90 feet deep, or 55 feet above the mouth of the tunnel, This reservoir will have a capacity of 500,000,000 gallons. As the plan indicates, provision has been made for the construction of another storage reservoir to hold 650,000,000 gallons against periods of drought, but it is probable that this will not be found necessary, at any rate, for present needs, as the potential power has been underestimated. TRANSPORT HEAVY ITEM. Transpoit Is one of the heaviest items of expenditure in connection wilh this undertaking, as may readily be reckoned when it is stated that it cost the department about 26/by a steam shovel as fast as for eevry ton transported to Mangahao, and 17/- for every similar load as far as Arapeti. Consequently every effort has been made to use what materials are at hand. The hard blue stone from the tunnels has been sayed and crushers ar e now utilising this in connection with the construction of the dams. At Mangahao, too, a fresh brings down quantities of fine sand which are scooped up it piles up against a bend of the river. Every penny so saved is a penny earned, but seems to be a mere drop in the ocean when one contemplates the ultimate cost of this mighty engineering feat.

The manner in which the great engineering difficulties have been faced and conquered is a magnificent tribute to the engineers who will soon be instrumental in bringing the “juice” to our homes, farms and factories.

Another large shipment of poles for the Manawatu-Oroua Electric Power Board is now being unloaded from s.s. Omana at Castlecliff, while the s.s. Ihumata was expected to arrive at Wanganui last night with a further quantity.