NEW PROBLEM CREATED

Poverty Bay Herald, Volume LV, Issue 17738, 26 March 1932, Page 8

NEW PROBLEM CREATED

OF ARAPUNI

WAIKATO RIVER FALLS

(}’er Press'Association.| HAMILTON, this day

Following tho filling of the Arapuni lake, the level of the Waikato River has fallen sft. below normal, and as a result Hamilton's water supply has been seriously a fleeted. The intakes at the pumping station arc now above water and the borough is relying' solely on the reservoir accommodation for the borough supply. At the request of the borough engineer 1500 msecs of water were released at Arapuni this morning to alleviate the situation. With the level of the river lints raised no further anxiety in this connection need be felt here.

With the appreciable drop in the level of ,tlie Waikato River at Hamilton, slioals and snags have appeared, rendering bathing on any stretch of the river fraught with considerable danger. Moth wharves of the House Shipping Company at Hamilton are high and dry, and all river transport here is suspended. The extent to which the water level has dropped can he gauged from the far) that it is possible at various poinls of the river at present to walk practically waist liigli from hank to hank.

The public, in the meantime, has been requested to exercise rigid economy in the use of water.

ARAPUNI RESTORED LAKE TO EE REFILLED GIGANTIC SCHEME COMPLETED ROWER EARLY NEXT MONTH After being dry for a year and 1,0 months, the re-filling of Arapuni Lake was commenced on Thursday, when the {gates in the diversion tunnel were partially closed. In a little over a fortnight; the great hydro-electric works will once more be in operation, generating electricity for the use of the entire Auckland Province, including the city of Auckland.

The re-entry of Arapuni info the active field of industry is an event of first importance. Upon it, the province depends for 45,000 kilowatts of electrical energy. This is the output of the three generators which were in operation when the power station was closed for repairs in June, 1950, and when tho fourth generator is working the capacity of the station will he 60.000 k.w. This will give it a larger output of power than any other hydroelectric station in the Dominion and will provide the provinco with industrial and domestic power on a scale not excelled in any part of the world and equalled by few of tho larger and older countries. MAGNITUDE OF TIIE TASK The engineering magnitude of Arapuni gives the scheme a nation-wide interest. It harnesses New Zealand’s largest and longest river, navigable for ICO miles along its 170-mile gourse from Lake Taupo, it boasts the most formidable artificial dam in the country, its electrical machinery and equipment are by far the most modern and elaborate so far imported, and engineering problems of a difficult and interesting nature were involved in the undertaking. It has been estimated that when fully developed the total cost, irrespective of the cost of repairs, will not .‘exceed £l3 15s per electrical horse-power of plant installed. This is believed to be a record under post-war conditions. A great deal of discussion has raged round tlm selection of tho site of the works in view of the. volcanic character of the surrounding country. It is interesting to recall, however, that long before the Government decided upon Arapuni Gorge as the, most suitable locality for the principal hydro-electric scheme iit t)ie Auckland Province, the identical site was considered as a likely proposition by the Wftihi Gold Mining Company, winch ultimately developed the lloraiiora scheme a little lower down file river. EARLY EXPLORATIONS The Government first explored the Arapuni site in 1914, when small groups of engineers camped beside the remote gorge and deep bores were sunk beneath the river-bed to test the nature of Llie country. A tunnel was driven under the river and u pilot tunnel was carried through the ground on the lino the diversion tunnel now takes. Galleries were driven deep into the cliffs on either side of the gorge and shafts were sunk on both sides of the dam site to a depth of 59ft. below the river level. Mr. Evan Parry’s plan for a chain of hydro-electric stations throughout the Dominion, together with a recommendation in favor of a Jam across the Waikato River at Arapuni Gorge, was adopted by the Government in 1918, and in July, \C2I, tjie expert commission's recommendations for the construction of the Arapuni scheme were approved. The contract was let to , Sir W. G. Armstrong, Whitworth and Company in 1924, the contract price being £1,170,891, and operations were commenced on September 14 of that year. Tho actual cost was £2.300,000j which includes the cost of the transmission lines. A BREAK IN THE COUNTRY Tho first unit came into operation in May, 1929, and on Juno 2 power from the station was first used in Auckland. It was delivered uninterruptedly to Auckland and the various power hoards throughout the province for over a year. Then, on June 7, 1930, a block of coonfry embracing the penstock tunnels, between the spillway and the powerhouse, developed a fracture along the front of the tunnels and up thp headrace. Water poured into the fissure, developing hydrostatic pressure, which tilted the block, including the powerhouse, toward the river. The bending movement occupied two days, yvhile the base of the cracks filled up with grit, allowing fuller development of tho pressure.

The fault in the country had nothing! to (jo with the, vibration that ocurred in the third generator; trouble had been experienced with that unit at least a month earlier. The diversion tunnel was immediately opened, relieving the pressure of water over the, spillway. ARRIVAL OF SWEDISH EXPERT The immediate effect was a movement of the block of land hack to nearly its original position and the leaks which occurred were reduced proportionately. It was obvious, however, that remedial measures of a comprehensive character would have to he undertaken. Tho works were closed on June 11. the lake was emptied, and a thorough inspection was made hv the engineers and the Minister of I’ublic Works. On August 27, 1930, Professor P. d. Ilornell, the doted Swedish civil engineer, arrived in Now Zealand under commission to the (lovernmeut to report on the unexpected development and suggest. the most satisfactory remedy, lie stated that the fracture was duo to the fact that iiii' headrace was not made a water-tight channel. Tie recommended that the headrace should he concreted and surface, cracks grouted, and suggested that, a more satisfactory job would be effected if the falls, over which tho

surplus water from the spillway weir escaped, were also concreted. COMPLETION OF THE WORK All these recommendations have now been carried out, the cost, as estimated at the time, being! £503,000. The entire cost of the scheme lias tlius been raised to £2,800,C00. Professor Howell's recommendations fully bore out the opinion already arrived at bv the Public Works engineers. Not only have all the measures suggested been carried put with great thoroughness, but steps have been taken to insert an additional valve in the diversion tunnel. The shaft is already in course of construction and will be completed when the tunnel is closed. Wlieti the dam was previously filled, in December, 1927, a month was occupied in the process, but at that time Auckland and llie province were dependent on ITorahora for electric current and Kuflieiout water passed through the tunnel at Arapuni to enable iloraliora. to continue operating. On ibis occasion Horahora will lie partially (dosed and power for nearly all re(jiiiremenls will be supplied from the King’s wharf station in Auckland. This coni-bn in ling station will close definitely as soon as Arapuni power is again available, the plant being retained purely as a stand-by.---Herald.