WAIKAREMOANA

Stratford Evening Post, Issue 5, 21 December 1928, Page 4

WAIKAREMOANA

POWER NEARLY READY AHEAD OF TIME. RELIEF FOR MANGAHAO. ' Within a foi*tnight the Lake WaiI karemqana hydro-electrical scheme, ■■'; the completion of which is practi- | cally the key of the success of the :< North , Island's hydtp-eiectrical schemes, will be in operation. Al- : though it will be some timo Before '■' 'it .is working-at its maximum capacity, the turning on of the Wai- ; karemoanacurrent, even to a lim~ '■■ ited extent, will mark a red-letter « day in hydro-electrical evelopment |of the Dominion, and will be of ; great assistance to Mangahao. I The official opening of the scheme will •probably take place early in * ; the New Year after a thorough try- ;' out.—Post. i Originally it was contracted to* have supplies available from Waikaremoana in June next, but owing to the overloading at Mangahao and the non-com-pletion of Arapuni, the work has been vigorously pushed ahead, so much so that the original time has been beaten by, 'some months. There was delay with the deliverv of plant from England, but splendid progress was made by the Public Works Department with the construction of the headworks and the

'pipe lines, so when the plant did finally arrive no time was lost in install- (,;, ing it, ( and most of the .necessary rei- tieulation was ready for its arrival.. From the point of view of hydro-elec-trical schemes there could hardly be ,; anything better than Lake Waikare- —. moana. The beautiful lake, one of New |, Zealand's finest scenic attractions, is /about 2000 feet above sea level. It has an area of some 13.000 acres, and a watershed of about 140 scfuare miles of mountainous bush country. The ■waters of the lake naturally escape from their mountain prison through ' the outlet at Onepoto. This outlet, ■'and'other leakages, form the Waikare- . te-heke River, a turbulent, dashing mountain stream, and in this stream lay •j ;the engineers' opportunity of utilising the everlasting and hitherto wast/j'eoT energy of the lake's Overflow. There ';' was, below the level of the big lake, and before man's interference with Nature came into evidence, aU insignifi- ' 'rant, little lake called Kaitawa. The '■' first, in the Waikaremoana hydroL electrical scheme was the diversion of ■ : - the; Waikare-te-heke River into this ■*, lake, which has taken on an importance i and a size it never possessed before. , From the enlarged lake the waters, now

at a height of about 1700 feet, have been taken by the engineers through a 12ft. tunnel, 770 feet in length, which leads into a huge surge chamber. From this chamber a double pipe lino leads clown to the power-house, and its generators 674 feet below. That, briefly, is the scheme which will develop 40,000 horse-power, and which can be extended to develop 100,000 horse-power. Certain preliminary works are already in hand to provide for such development. CONSTRUCTIONAL DETAILS.

The Waikaremoana scheme had certain initial advantages over Arapuni in that there was no necessity' to build any large and costly dam, Nature being kind in the topographical features of the area. The Waikare-te-beke River is diverted through a concrete-walled race about 3000 feet in length into Lake Kaitawa, the flow of water being regulated by a weir, which allows the surplus water to run into the old bed. .At the southern end of the lake an embankment provides for the raising of the lake's level. This little lake is no novice in hydro-electricity, for during the last ten years it has been the means of supplying the power for the Wairoa Electric Power Board, but in future this relatively small'function will be abandoned in favour of the big- '-(•• scheme. , From the lake to the surge chamber is the 12ft. tunnel 770 feet in lengthExcavation*.of this tunnel was difficult owing to the varying formations encountered. Over 4000 cubic yards had to be excavated, but finally a completely circular tunnel was completed and lined with 12 inches of concrete.

The surge chamber is a -most interesting work. Circular in shape, its massive concrete walls 30 feet high and 100 feet across give it a capacity of 1,500,000 .gallons. This chamber will have a cushion-like effect, and relieve irregularities of pressure from both the tunnel and the pipe line. Without this provision there would be great danger of cracking even the solid concrete shell in the tunnel by the tremendous weight of the imprisoned waters. The chamber has been fitted with a large screen extending the full depth to prevent foreign substances from entering the pipe line, while immediately behind it has been installed a remote gate for each pipe line.' Although only a double pipe fine has at present been laid, provision has been made at the chamber for a third line when the scheme is further developed. Opposite the intake_ in the surge chamber is the pipe line, which, with one angle near the top, has a straight run down hill to the power-house nearly 700 feet, below. In its long descent to Tuai the 3700 feet of pipe line has two distinct grades. This section or the scheme was constructed by contract by

the Dunedin Engineering and Steel Company. The great pipes, six feet in diameter, were rolled on the job, the company having a special plant at Tuai for that purpose. In this double pipe line no less than 1800 tons of steel were used. Each pipe is securely anchored on concrete trestles, and a unique engineering feature is that there are two quarter-mile stretches between anchor,!.

THE POWER-HOUSE. The central feature of the whole scheme is, of course, tlie power-house. Before construction of the power-house could be undertaken, the Kahatangaroa creek and another small stream had to be diverted well away from their original routes, which lay over v the site for the building. Owing to seepage, difficulties were met with in the foundation work, but with the aid of a powerful pump, that was in time overcome. The building, which is 196 feet long, is now completed,, with the exception of various finishing touches. Standing 60ft. high and built of reinforced concrete, it is a most imposing structure. On 30ft. concrete foundations are to rest two 20,000 k.v.a., 11,000 volt generators, the largest yet installed in New Zealand, but provision is made in the power-house for installing another similar generator to feed a third pipe line later. These generators are directly coupled to reaction, Francis-type turbines of 28,000 brake-horse-power made by Vickers, Armstrong and Co., England. A Lamer-Johnson 6ft. valve will control the flow from the pipe lines to the turbines. From the turbines large chutes convey the water out of the power-house into a channel nearby. One of the turbines is already installed, while the generator, which will develop as much power as the whole of Mangahao, is practically completed. No time is being lost in installing the second turbine and generator, and when this is done the first stage of the scheme mav be said to be complete. A MASS OF AERIAL GEAR. On a higher level than the powerhouse is what appears to the layman a bewildering mass of aerial gear. For the Gisborne line six small transformers have been installed to step the current up. to 50,000 volts, while for the Napier line an equal number of transformers, some 28 tons in weight, will step the current up to 110,000 voltsFrom the generators the current is conveyed through a tunnel which comes up under each transformer. After being stepped to the required'voltage, it passes through the lightning arrester to the switches which control the transmission lines. The outdoor station has been designed to provide for further de-

velopnient to deal with the completed scheme. The transmission lines both to "RedclifFe and to Gisborne have been completed, and are now ready for use- The line between Tuai and the Redcliffe sub-station at Taradale is nearly 60 miles iu length, necessitating the erection of about 300 steel towers to carry it over the rugged country between the two stations, and on this route a twin circuit has been provided. The Gisborne line, which is 50 miles in length and carried chiefly on poles, will form a single circuit. The transmission line from Waikaremoana to Napier is the one which will link up with Mangahao and relieve its burden, the other lines providing the East Coast districts with energy.