Arapuni Problems

Sun (Auckland), Volume II, Issue 342, 1 May 1928, Page 8

Arapuni Problems

PROGRESS AT POWERHOUSE Pump to Lower River-Level

SIX HUNDRED THOUSAND gallons of water are leaking dailv from the dam at Arapuni. The figure at first seems stupendous, but is ream ot no concern "in a job of such magnitude leakage is expected, and daily observations show that in tins case the flow is diminishing.

Most of the leakage from the bis structure at Arapuni is coming from the western side ot the dam. Ther... is a series of smaller trickles, on all of which the departmental engineers keep a close check. All records are tabulated, and the daily readings totalled, with the result that it is now possible to learn that the flow has diminished from 566 gallons a ™ in " ute, in January, to 407 gallons a minute at the present time. A small leakage under, the gates in the diversion tunnel is of even less concern, and could be stopped, if txus were thought necessary, by the dropping of “fines” consisting of sand and

door level of the immense streamlined tubes through which water wi.l pass from the turbines to the tailrace. In starting concrete work in the of the powerhouse site, the Public Works Department has reached an important mark in the history of Arapuni development. Excavation to desired level, 40ft below the floor of the preliminary excavation, was facilitated by an ingenious system oi cement grouting, hundreds of tons oi liquid cement being * under terrific pressure, into the crannies and interstices of the rock-wall dividing the the site from the riverbed. These operations have so far been eminent •> successful. The next phase will be work on tne tailrace. in the adjacent riverbed. To begin this the department will first have to lower the level of the water backed up from the junction, and it is preparing to do this with a pow erful electric pump. The installation of the necessary gear was begun four days ago. The plant is intended to keep the water 15ft below its present level, and when working it will lift water through a flume across the sandbank, and so into the running stream beyond. For the rest, the entire scheme awaits the construction of the powerhouse. Very little work remains to bo done at the transmission station, where Mr. Y. V. Overgaard. the Swedish engineer, still has a small staff at work applying the finishing touches to switchgear and other equipment The three completed penstock tunnels are fitted with gates, screens and a powerful half-submerged sweeper which, traversing the outside of the screens, runs on the trolley principle, like a tram. TESTS OF ROCK Below the spillway, where the diverted river crashes from serenity into turbulence, borings are being taken to test the rock structure. So far these tests have revealed bard rock, presumably patchy, as it is throughout the neighbourhood. Erosion has not yet ceased, and on Saturday there were falls of rock at the side of the main cataract, which has now a vertical drop of 100 ft. Such is the violence of the fall that it is permanently enveloped in spray. Down below, in the erie aisles of the uncovered forest, many ancient monarchs have fallen. They do not float, but apparently sink quickly to the bed of the river. Armstrong, Whitworths are keeping a skeleton staff on dismantling work, and No. 1 camp, with the works at the dam, has been broken up. Mr. F. W. A. Handman is still in charge, but several of his staff, and three members of his family, leave for England by the Aorangi on May 21. The Public Works Department has about 150 men at work on the powerhouse. Mr. A. Dinnie, engineer-in-charge, said yesterday that h© hoped it would not be necessary to re-divert the river, though was always the possibility. “We do not want to minimise our difficulties,” he said, “but so far we are very gratified with the progress made.”