ARAPUNI TO CLOSE DOWN

Sun (Auckland), Volume IV, Issue 993, 9 June 1930, Page 1

ARAPUNI TO CLOSE DOWN

Engineers Hurry from Wellington EARTH FAULT GIVES ANXIETY Water Leaking Through Gorge Face THE SUN'S Special Reporter ARAPUNI, Today. ARAPUNI is to close down as a result of a serious earth fault which has developed in the country on the east side of the overflow channel. It is expected that the generators will cease running tomorrow. The huge lake will be lowered until the spillway is dry. Engineers will then be able to report on the exact cause and extent of the earth fault. Water will probably stop flowing over the spillway on Tuesday or Wednesday. Auckland’s supply of power will be obtained from the King’s Wharf station, which is ready for instant use, Horahora and Penrose.

r “There is no need for panic although, in the absence of a definite statement, I view the situation with a certain amount of concern,” Mr. R. H. Bartley, general manager of the Auckland Power Board, said this morning. When the fault was discovered in the early hours of Saturday morning, information was immediately sent to Wellington, and engineers hurried north in motor-cars. The serious aspect of the trouble can be gauged from the fact that the following officials are at Arapuni:—The Hon. W. B. Taverner, Minister of Public Works; Mr. P. W. Furkert, engineer in chief, Public Works Department; Mr. C. J. McKenzie, assistant chief engineer; Mr. F. T. M. Kissel, chief electrical engineer; Dr. J. Henderson, Government geologist; Mr. T. MacLennan, district electrical engineer; and Mr. A. D. Dlnnie, district engineer for Hawke's Bay and formerly chief of staff at Arapuni. As a result of the earth fault, three leaks have broken out In the face of the gorge, the concrete at the end of the penstock intake where it joins the weir has fractured, and the steel lining of a penstock tunnel has broken away slightly. The earth fault extends through the country and ends below the falls, which were caused by the water pouring over the spillway channel when the river wa.s diverted. Since the main fractures in the concrete were noticed, the engineers have measured them hourly, but no further movement has been noticed since they were discovered. The crack, where it leaves the concrete, is two inches wide, but soon reduces to a quarter of an Inch. It then runs across country like a hair, ending below the falls, where the erosion took place some time ago. It is believed that a slight earthquake shock might have caused the trouble. This theory is supported by the fact that yesterday engineers discovered that the steel lining of one of the penstock tunnels, which is not yet in use, had been torn away from the concrete at the intake. The movement here is very slight but indicates a fault somewhere. Two concrete steps have also parted from the wall in the pump-house to a distance of two inches. „ CABLES DISMANTLED The cables leading to the rheostat, an instrument which controls the flow of electric current, have been dismantled as a precautionary measure in case one of the towers should collapse. At 2 p.m. yesterday it was decided to open the diversion tunnel gates to lower the lake behind the main dam. These gates are controlled hydraulically and were raised slowly until the reading board showed an aperture of two feet. Water roared through the gates with terrific force and dashed against the opposite bank of the old river-bed in clouds of spray. It was a magnificent sight and was watched by large numbers of visitors from the road above. No one was allowed into the affected area yesterday, the roads being blocked by rows of oil drums, over which sentries stood guard. As the level of the huge lake behind the main dam is lowered the diversion tunnel gates will be opened still wider to keep the rate of discharge constant. Horahora will not be troubled by the extra water which is pouring from the dam, as the Waikato River is below normal. Since the diversion tunnel was strengthened with further steel plates last year there will be no anxiety on this occasion. Before that, however, there had been some erosion which disturbed the engineers. Last Christmas, after the additional steel plates had been added, the gates were opened partially for five days and gave every, satisfaction. When they were closed again and the tunnel inspected, everything was in order. There is no trouble with the main dam nor with the weir, both of which are as firm as they ever were. The leakage of water through the gorge face and the cracks in the concrete are the two disturbing factors. NO IMMEDIATE DANGER Although the spillway weir does not appear to be in any immediate danger, the leakage of water, increasing as it runs down through the hillside into the gorge, is causing great concern in view of the loose nature of the hillside, and particularly in view of the trouble that was experienced in finding suitable foundations for the power house, which is immediately below the seat of the trouble. The two generators are still working as there is sufficient water in the headrace for another two days. The headrace will then be dewatered and a thorough examination of the spillway weir made. The hill at the sub-station near the spillway is settling down at the rate of two inches in 24 hours. The mails, danger is that continual leakage

of water may cause a greasy bank in the hillside, that is to say, a wet sandstone level in the hill, causing the weight imposed above to slip. ■ While the spillway is dewatered the danger is temporarily averted. “SERIOUS CONCERN” SEEPAGE HAS ENGINEERS WORRIED UNDERTAKING REVIEWED THE SUN’S Special Reporter ARAPUNI, Today. When engineers threw the 200 ft dam, classed among the most famous and the highest in the world, across the Waikato in order to harness its turbulent waters in the service of man, many people prophesied that serious difficulties would be met in restraining such a powerful element in such loose and difficult country. In part, these predictions have been fulfilled. Troubles have been overcome only for fresh difficulties to arise. The recent erosion below the spillway weir was countered; but a serious seepage of water down through the gorge below the power-house is causing serious concern. From the dam the water runs along the head-race at a high level above the old riverbed to the spillway weir, from the head of which the penstock tunnels carry the water down through a high cliff to the gorge below, where the powerhouse is situated. The first difficulties were experienced at the powerhouse site, where serious trouble and delay were caused through inability to find good foundations. This delay in the erection of the turbines meant that a greater volume of water than was anticipated was rushing daily over the spillway into the uncertain country below. As a result of last year’s discovery of serious erosion below the spillway, which was working back, threatening tho spillway-weir itself, extra penstocks (the seventh and eighth) were hurriedly driven to take some of the water and relieve the volume over the spillway, not yet completed. The latest development was the discovery early on Saturday morning of a serious seepage through the hill, where the diagonal road runs up from the powerhouse to the spillage. At the point where the intake structure joins the spillway-weir, a two-inch crack has developed, It is evident that in the hillside east of the spillway there has been a considerable earth movement. This crack is traceable for a distance of 20 chains to where it comes out near the lip of the old waterfall. Two other smaller cracks are across the decking above penstocks Nos. 1 and 2, one of these running up through the sub-station. MAIN FRACTURE Although a small fracture is apparent in the weir near a structural join, it is net thought that the weir itself is in any great danger. The main crack is in a structural join between the weir and the weir buttress. It opened out, leaving a gap of 2iu between the rheostat house and the concrete steps. It is apparent that if an earth movement had affected the weir, the thin concrete apron on the river side would also be cracked; but this is not so. The earth movement, with its consequent seepage of water down to the old river, is very serious. It will have to be stopped, and this question is now exercising the minds of enginMr. R. W. Holmes, civil engineer and prominent critic of the Arapuni scheme, stated in November, 1928, that it had been found by a bore sunk more than 200 feet deep that only sand and silt exist under the powerhouse. Quoting from the contract specifications, he also pointed out that the rock at the site of the powerhouse is ‘‘a tufa of volcanic origin, and of moderate hardness; but may include soft layers or pockets.” “SERIOUS DOUBTS” That the contractors, ArmstrongWhitworths, were at some variance with the Public Works Department as to the foundations at the power-house was evident early in the job. In fact, it is generally known that the contractors had serious doubts of the strength of the foundations to carry the heavy generating plant. There was a halt in the work when the time came to sink for foundations. A strip only 20 feet wide along the outer side of the site was in question. Here a bank of talus rested on a deep bed of pumice sand, and the contractors desired that the site should be shifted that distance cliff-ward, to avoid building on what they considered an uu-

stable portion. The Public Works Department declined to vary the contract, and eventually took over that section of the work itself, laying heavy horizontal reinforcing to relieve the transverse stresses, and thus distribute the weight above the sand area over the whole site. The Minister of Public Works, the Hon. W. B. Taverner, arrived here this morning, and with Mr. F. W. Furkert and his staff is inspecting the works. The diversion gates opened at two o’clock yesterday afternoon, and the head race is now not running over the weir, the old riverbed carrying the water. There is still 12 feet of water at the spillway above the penstock level. This will run the turbines for two more days. A Ministerial statement was expected this morning. IF SPILL,WAY COLLAPSES HAMILTON PREPARATIONS PUMPING PLANT REMOVED From Our Own Correspondent HAMILTON, Today. Emergency preparations on a large scale have been made at Hamilton in the event of a collapse of the spillway at Arapuni, which would result in flood conditions locally, it is estimated that the river would rise about 25 feet above its present level, and would completely submerge both the old pumping station and the station which has just been built. To avoid all risk, the borough authorities have removed one complete pumping set to the depot, so that it would not be damaged and could be reinstated at a moment’s notice. The recently installed pumping equipment for the new waterworks scheme has been dismantled and taken to a place of safety. Flood damage to this equipment would cause a loss of several thousands of pounds to the borough. “Should the worst happen and the spillway be carried away only eight houses in the low-lying areas would be affected at Hamilton,” said Mr. R. Worley, borough engineer, this morning. “We have made all arrangements for borough transport to be available to carry furniture and other household effects to safety.” He added that the flood would remain at a height of 25 feet for only about four hours, when it would gradually subside. Within two hours, the borough pumping equipment would be in operation and reservoirs would be replenished. There was absolutely no danger of shortage in the town water supply. Mr. Worley said he did not desire to comment on the position at Arapuni, other than to say that in his opinion it was extremely serious. SOURCES OF SUPPLY KING’S WHARF READY CONSUMERS MAY CO-OPERATE As soon as it was known that trouble had developed at Arapuni and that there might be a stoppage of power from that; plant, preparations were made throughout the province to organise the other various sources of supply. There will be no difficulty in carrying the required load. The following sources can supply power:—King’s Wharf, 26,000 kw.; Horahora, 12,000 kw.; Penrose, 3,000 kw.; Grand June-

tion Gold Mining Company, 3,000 kw.; and. McLaren’s Palls, Tauranga, 1,200 kw. The total power available from these sources is 46,000 kw. Mr. R. U. Bartley, general manager of the Auckland Power Board, stated this morning that the King’s Wharf station is in readiness to start operations at a, moment’s notice. As soon as information was received from Arapuni that trouble had developed, engineers were instructed to prepare the generators for use. This was done yesterday. One, of course, has been running for some time to lessen the load from Arapuni, when vibration trouble started in No. 1 unit some weeks ago. Since the King’s Wharf station was closed down some months ago the machinery was completely overhauled and a skeleton staff has been maintained. The Power Board has only sufficient coal in hand to last for three, or four weeks, and if any serious trouble developed at Arapuni it would be necessary to make fresh contracts for the supply of coal, as the old ones have expired. Last week the Power Board’s peak load passed 29,000 kw. for half an hour, but it is believed that this could be avoided with the co-operation of the largest users of power in the city. Mr. Bartley does not know yet whether any such measures will have to be taken and will await a report from Mr. Furkert at Arapuni. It is expected that the required information will be obtainable in the next two days.