HYDRO-ELECTRIC SCHEME.

Auckland Star, Volume L, Issue 201, 25 August 1919, Page 9

HYDRO-ELECTRIC SCHEME.

ARAPTJNI SCHEME. SATISFACTORY PROGRESS. "REPORT OF OPERATIONS. Good progress is "being made with the £ preliminary work connected with .the I Arapuni hydro-electric sclieme. With t regard to this Mr. S. J. Harbutt. preei- < dent of the Auckland Hydro-Electric 1 League, said this morning that'he had ! received a report giving an outline of the 1 progress of the work, he was satis- 1 tied that it wa s advancing steadily. All I that was needed now was to impress 1 upon members of Parliament the neees- < sity of seeing that no delay takes place i and that the scheme be pushed on to .; completion, Following is the report < received:— i i Tunnels and drives have been made i into the rocky cliffs at both sides of the river within the confines of the dam to : the length of from 50 to 120 feet.' In . every ease the rock en masse lias shown . itself quite able to stand the required i strain. One specimen sent to Wellington • was subjected to a pressure of IDS tons i to the square foot, or lb times that ! needed to bear the weight of the dam. t Test holes have been made over a fairly ) wide area on the eastern bank at the - top level, in every case proving satisfac- ] tory. On the western bank at the top , level, hard rock is nowhere more than a i few feet from the surface —a rock so j hard 'that it can be dealt with only by I explosives. At the lower level, on the ['western edge of the river, a shaft has i . been sunk to about 10ft below the sur- '. fate of the water, and has been found ; I quite free from soakage from the river. ! POROSITY TESTS. , I Half-inch pipes have been placed from the top of the cliffs to the interior of the walls of the tunnels below, water being ' i supplied to them from attached vessels on the cliff tops several hundred feet i above. This is to find out the porosity of the stone under the same conditions ■ las there will be when the dam is eonI structed—that is, under a pressure of about three atmospheres. In these ex- ' periments frost has proved a disturbing factor, bursting the pipes and causing . the replacing of hundreds of feet of piping up the sides of the perpendicular cliffs. To counteract this trouble a workman has been lowered over the face of the cliff and lagging lias been wrapped round the pipes. The porosity tests arc still in progress. j DEPTH SOUNDINGS. The river here runs at the rate of 15 io IS knots per hour, causing the taking of the soundings to be one of great dilli- " culty. A weight of 141b of metal floats on the surface when suspended from a rope. Large boulders lying in the bed ' of the river also interfere with the work, ° but it is believed that the depth is under 30ft. Sufficient soundings have been taken to give the required informal ion to permit a tunnel to be made, connect--5 ing perpendicular shaft; at either side near the river edge. Through the roof jof this drive upward borings can be made giving the exact depths of the river at regular intervals. SUPPLYING THE POWER. ' The Arapuni site is a wonderfully suitable one for hydro-electric works of great magnitude. The old river bed. at a level of 160 ft above the surface of tho ■ present stream, branches off at almost ) ' a right- angle immediately above the dam 3 site. This old course will discharge the ■ 1 water into the present river bed about a ' mile lower down the gorge. Several tun--5 nels a few chains iv length will convey " the desired volume of water to the 3 powerhouse plant. This body of water ' coursing through the tunnels will be c travelling at a great velocity, as it will -~ fall a distance of 100 ft in the length Vf c these short tunne'.s. At the mouth of h each tuitnel a turbine will work a gene | h rator larger than any in use in the Nia "c g-ara plant. When the scheme is eom--t pitted it will make the Arapuni hydron electric plant the most powerful south, ir of the Line, and second to Niagara in the it. whole world. In all, about ItiO.OOiT h.p.: ir will be developed. ° THE DAM. 'P - The dam will be horseshoe in shape, 'i about 15ft across the top 43ft at the base, and lliOft high, and will be constructed of ferroconcrete, the convex sur- , face pointing up-stream and the wings , let into the cliffs for many feet on both sides. The river will be dammed back so . that from the dam southwards will be a lake over 20 miles long and half-mile wide, supplying a splendid inland waterway for motor boats and barges and a ';', unique position for regattas, including ' sculling races. It has been estimated that live years hence electric power will be distributed from Arapuni. The cheapness and convenience of the power ie once realised by the public at large will cause all to insist on its early institution. A trifle of £5 per year will be all "" the cost to supply electric Dower for the " c 101 needs of a farm of 300 or 400 acres '* near the powerhouse. Some idea of the .. magnitude of the plant will be gathered '" when it is realised that the rotors will '<* each weigh GS tons in an indivisible part. lt - A corresponding machine in the IloralU hora plant weighs only 11 tons. j Hj SIMPLE RUT STUPENDOUS. j , s A necessity for the conveyance of the I(j material and machinery will be a rail- , e way from Putaruru to Arapuni, a dis- „ tancc of only nine miles. This line will lr cross the dam abreast of the main road to Te A.vamutu, to which town the, line { will doubtlessly be constructed, opening lup a vast area of agricultural land and ' shortening the distance from Wellington jto Rotorua by 4(1 miles, and from AuckIland to the same resort by 10 cr 12 miles. HORAHORA. In reference to the Government acquisition of the Horabora plant, the great- * est emphasis must be placed on the fol- ?* lowing: The Uorahora plant when developed to its utmost will leave only 12,500 h.p. for distribution outside of c Waihi, and beyond a 50-mile radius there c will bo a serious loss of power from so small a voltage, making the Horahora J " plant of little use beytmd Ngaruawahia. Before this step i_ made by the. Governa ment the utmost precaution should be ' c taken to prevent any possibility of the : ® shelving of the Arapuni scheme. Un- ~- doubtedly some will be only too ready ~ to say that when the Horahora -plant is *> acquired that Auckland province has its ;" hydro-electric corks. The public should = " jbe informed that Arapuni is only five I miles further up the river than Horahora ! and only 100 miles from Auckland in a '.direct line. The Government ownership a- of Horahora is highly desirable only if d. the above safeguards are made. Electric ;e power at prime cost would be available it for the Arapuni works and the electrifyid ing of the railway from Putaruru to c- Te Awarnutu. The" needs of the district "3 surrounding Arapuni vvould be supplied )r by Horahora, but of what use would the residue after local consumption of 12,500 th h.p. be to Auckland city, much less the ea Auckland province? No doubt exists as io to the future of the Arapuni scheme, al [ and every effort should be made for its , speedy completion.