Harnessing a Mighty River

Sun (Auckland), Volume III, Issue 914, 6 March 1930, Page 9

Harnessing a Mighty River

Arapuni—The Greatest Engineering Feat in New Zealand

Arapuni, the greatest electric- 1 : power scheme in New Zealand, had j cost the country £2,286,839 on March ! | 31, 1929. This vast undertaking is now re- 1 cognised as one of the greatest | j engineering feats of the Dominion. In I | six years a river has been diverted I and dammed to forma huge lake, mil- ; | lions of tons of rock have been moved, \ ! the whole countryside altered, roads and a village made, and 091 miles of overhead cable laid to Auckland. In 1921 a committee of experts visited the present site of Arapuni. Its members explored the country and walked the banks of the Waikato River. Down below that turbulent river

poured the waters from distant Take Taupo, through high -walls of rock. Standing among the bracken and heather of the cliffs those men looked down on what looked like a narrow ribbon of foam. Here was the place to build a giant dam; here was the spot from which Auckland and the surrounding country could be supplied with unlimited electric power. In 1924 the contract for the huge undertaking was let to "the English engineering firm of Sir William Armstrong, Whitworth and Company for £1.170,901. That price, however, later proved to be unsatisfactory and the work of finalising Arapuni was taken

over by the Public Works Department at over twice that amount. Soon the indistinct rumble of the Waikato through the Arapuni Gorge was drowned by the sounds of human industry. A village had to be built and 12s miles of road constructed to the nearest railhead. Putaruru. Thousands of tons of machinery were soon being transported to the site of the dam and by 1925 work was well under way. First of all the nature of the country had to be ascertained. A gallery was driven under the river at the dam site and a series of shafts and tunnels was driven into the cliffs on either side. Electric power was brought from Horahora and a scheme

| for carrying metal from Multu, nine i miles up the river, had been evolved. ; Men and materials and machinery were now pouring on to the site. Everything and everyone was busy. I First of all the waters of the Waikato j River had to be diverted so that the j huge dam could be built. This was a. ! dangerous and arduous undertaking. Tunnellers and engineers were soon | storming the rocky walls of the east- ; ern bank of the river. Concreting as i they went, they cut their diversion I tunnel in a curving line above and ; below the site for the dam. At the same time men were building a steel | suspension bridge across the chasm 1 and preparing an airway which would

L carry a cage back and forward high . above the mighty waters down below. 1 Preparations were also going ahead 2 in each cliff for the wing walls of the i ; dam. and a little further down the l > ' river thousands of tons of spoil were ; > l being removed for the power-house j - . site. t ; As soon as the diversion tunnel was i 3 | finished the ends, known as “dump- j :• ' lings,” were blown out with dynamite, j Part of the Waikato River rushed ; - , through it, but not all. A gabion dam i - j had to be constructed to force all the ' i I water through the tunnel and leave ‘ - j the bed of the river dry so that the j i | building of the dam could be pro- • s | ceeded with. After a great deal of j s i trouble this was done, and soon the !

f mighty Waikato poured through the I hole in its former bank. Now the mighty dam was to take shape, but only after months and months of toil in which men risked their lives night and day. More activity, more noise, more industry. Concrete poured down the chutes in never-ending streams and knitted together the vast network of steel: fussy little engine? brought sand from distant pits; compressed air drills ate away rock with a deafening roar. The dam appeared like magic. It. |is a huge wedge of concrete 170 ft i high, weighing 170,000 tons, fastened jto the banks of the river. Behind that

dam, where the Waikato formerly flowed as a turbulent torrent, is a huge lake extending for nearly 20 miles up the river. Before the diversion tunnel could be blocked and the lake tilled provision had to be made for the outlet of the water and its intake through the penstock tunnels to the generators in the power-house. Ages ago the Waikato had taken another course, slightly to one side of the one which was dammed. This was deepened and a gravity section dam 237 ft long and 33ft high was placed across it. The new course had to be enlarged and this was done by removing 100,000 cubic yards of earth and 10,000 cubic yards of rock.

Work went on day and night. At one time an army of 700 men was employed at Arapuni. It was a selfcontained community. By the end of 1927, the dam was ready to withstand the enormous weight of water. The diversion tun nel was closed and the lake began to form. On January 1, 1928, the lake rose and overflowed over the old course the river had traversed centuries before. No water could be taken into the penstock tunnels, so the whole of the river poured over the gravity dam, down over a giant water fall and out into its proper course again some miles below the dam. Further trouble came to bother the engineers. The force of water tumbling over the fails ate away so | much rock. that the engineers feared j for the safety of the gravity dam. | However, as the months passed, it i was found that all danger was over. I Now that much of the water is being ! absorbed to turn the turbines in the I power-house there is no longer any danger from the falls. But there was still a great deal of skilful work to be done before the electricity could be supplied to Auckland from Arapuni. There was a bitch over the power-house site; a difference of opinion regarding the strength of the foundations held up the work for months. Finally tha English firm withdrew, after protracted negotiations, and the job of completing the giant scheme was taken over by the New Zealand Public Works Department. Work on the power-house now went ahead with increasing rapidity. Auckland was crying out for a permanent and sufficient supply of electric power.

Work was again held up at the power-house because of water which soaked through when the river was diverted. This was eventually overcome by pouring into the site tons of j liquid cement. When this became j solid work went ahead without inter- j ruption. The erection of the first generator i went ahead quickly and by May 31, | 1929, it was supplying Auckland with j 15,000 kilowatts a da}’. The original j contract had provided for two units j to be working by July, 1927, but j delays were caused in many of the | departments and a strike also held 1 up the work for some time. Three units, each of 15,000 kilo- , watts, are now supplying Auckland j I with her electric power. ! And while men toiled at. Arapuni j | others were erecting the huge steel ' towers which were to support the j cables through which the power was ! to be carried to Auckland. Along j the route of 99i miles 527 of the steel j towers stood like spidery sentinels, of anything from 40 to 96ft in height. They clambered over river and railway, road and pasture and hill, almost in a direct line from Arapuni to Penrose, where the power is broken down j for distribution to the city and outer ; areas. Along those copper cables j there is always the enormous current i I of 110,000 volts. j Arapuni has been a giant scheme, ! : worthy of the men who harnessed a j great river. Nothing short of a violent upheaval can harm the scheme. 1 Auckland can remain secure in the j knowledge that she will always have ; a permanent and ever-increasing . supply of electric power.