ARAPUNI LEAK

New Zealand Herald, Volume LXIX, Issue 21251, 3 August 1932, Page 10

ARAPUNI LEAK

HEADRACE SEEPAGE DRAINAGE FUNCTIONING DIVER'S INVESTIGATION WATER LEVEL LOWERED STATION NOT AFFECTED [BY TELEGRAPH—SPECrAT, ItErOKTETI] ARAPUNI. Tuesday A leak, discharging sufficient water to fill a lOin. pipe, has developed in the headrace at Arapuni, and is giving rise to somo concern. Beneath the lined portion of tlie headrace there is a thick filterbed and an elaborate drainage system, the outlets of which are tunnels from the gorge to the bottom of shafts. The water is escaping by way of the tunnel driven behind the powerhouse.- From the tunnel entrance it is carried by a flume to the edge of the riverbed, where it drops a distance of 20ft. into the old channel. The leak was discovered on Thursday evening. It was then of small proportions. At 10 o'clock last evening the automatic alarm hell in the tunnel rang ominously, and, as one engineer put it this evening, this meant that the porous layer and drainage system which had been installed to take charge of any leakage that might occur, was functioning. The engineers spent an anxious time throughout last night watching the position. The services of a diver were requisitioned and he has been engaged exploring the floor of the headrace. Nothing definite has been discovered as yet. Neither has it been established whether a break has occurred in the lining of the headrace or whether the seepage has originated at a point along the unlined portion upstream from the cut-oft wall. Source of the Trouble The fact that the barge from which the diver was operating to-day was moored half a chain upstream from the cut-off wall where the lining ends, would suggest that the source of the leak is suspected to be in that vicinity. It was stated that the strength of the current was too great lower down to enable the diver to work, but all the visual evidence points to concentrated investigation around the cutoff wall. A further indication to that effect is supplied by the sinking of a shaft on the east side of the headrace close to the water's edge about half a chain down stream from the cut-off wall. During the remedial operations shafts were sunk on each side about this lire but some chains from the banks of the channel. Between them, it is understood, several galleries run at different levels for the purpose of catching water that might percolate beneath the cut-off wall which runs to a depth of 15ft. or 20ft. The escaping water is not discoloured to any extent. It is understood that it is all being collected by the one tunnel which runs to the bottom of a shaft sunk in the forebay close to the spillway weir.

This leads up to the end of the main drain that runs up the centre of the headrace as far as the lined surface goes. Tt is a cut about 6ft. deep with a pipe of large dimensions at the bottom. It is filled with rubble. Above is the thick filterbed upon which is the elaborate plastic lining surfaced with concrete blocks. Level of Water Reduced Water travelling from this drain into the shaft in the forebay could be collected at any point as far as the cut-off wall. In order to ease the pressure of the current in the headrace and to facilitate the work of the diver, the diversion tunnel gates were opened to one-eighth of their capacity this morning, or 1600 cusecs, and as a consequence the level of the water in the dam and headrace had fallen 2ft. by sun-

set this evening. The normal depth of the water in the headrace when filled is 20ft., where the lining; begins, and 25ft. at the spillway. The level of the water in the headrace could bo lowered 10ft. before the generation of power to tho full capacity of the machines would be affected. Investigations are still being carried out by tho engineers, but so far the source of the troublo has not been found, and consequently no remedial measures have been undertaken. Statement by Engineer When questioned about the position today, Mr. T. Rabone, engineer in charge at Arapuni, said that the trouble was by no means as serious as represented. "Tho

station is still in service," ho said, "and I see no prospect of it going out. A little seepage has occurred in the sides of the headrace and the diversion tunnel hits been opened to enable the water in the race to be lowered to permit of a full investigation to be made." In answer to inquiries made this evening a senior engineer said that the powerhouse was still generating at full pressure. Asked if it. was intended to dewator the headrace and closo down the powerhouse temporarily, he said ho did not know. It was hoped, lie added, that the station would not go out. of service. As u result of opening the diversion tunnel the Waikato River is heavily swollen, and is at least 2ft. above its level of yesterday. KING'S WHARF PLANT READY FOR EMERGENCY AMPLE WARNING PROMISED The Auckland Electric-Power Board is in readiness to put its steam plant at King's Wharf into operation within a few hours if the position at Arapuni makes this necessary. "Actually, it would take two or three days to un-water the hfadrace, if that course wore decided upon," said Mr. W. ,T. Holdsworlh, chairman of the board, last oveuing. "Accordingly, wc should roceivo two or threo days' notice if the Public Works Department decided to suspend operations, and it would bo only a matter of threo or four hours before King's Wharf could take over tho complete load. "There are plentiful supplies of coal at tho pQwer station at present. Naturally, if the King's Wharf plant has to bo" put into operation again, our previous contract for the supply of slack coal will automatically come into force. All we can do is to wait for word from tlie department.".