POSITION AT ARAPUNI

New Zealand Herald, Volume LXIX, Issue 21253, 5 August 1932, Page 12

POSITION AT ARAPUNI

SUPPLY CONTINUES REMEDIAL MEASURES SAG IN BANK LINING DISPLACEMENT OF SLABS CONSEQUENCE OF SEEPAGE [nv TELEGRAPH. —SPECIAL REPORTER] ARAPUNI, Thursday The latest development at Arapuni was tho discovery this morning of a partial collapse of a portion of the lining on the east bank of the headrace. A considerable number of concrete slabs are affected and through tho fractures a small quantity of water is percolating. It is clear that this sagging of the surfaco is not tho original cause of tiie leak, which has been puzzling tho engineers, for it had not occurred when the diver mado his examination of the lining on Tuesday. On tho contrary, it is a secondary fault brought about last night, it is presumed, by tho water that is percolating through a weakness or fissure a little further up tho headrace, finding its way under tho cut-off wall, and undermining a portion of tho lining before boing collected by tho drainago system and guided through tho man-made tunnels to the gorge. Remedy Without Stopping Although this development adds another problem to bo dealt with, tho engineers are hopeful that tho leak in the tiles can be permanently sealed without stopping tho generation of power. The engineers explained this evening that the water in the headrace will have to be still further lowered in order to effect repairs, and this may mean that a reduced head of water will be passing through tho penstocks to tho turbines. This, it is expected, will not greatly hinder tho generation of power. Already temporary measures to block the leak have been taken, canvas blankets being spread over the section affected to prevent the inroad of water. At the same time efforts to locale the original leak which is tho primary cause of the trouble are being continued, several bores being put down during the day. As soon as tho news of tho fresh development in tho headrace lining was received this morning, Mr. F. W. Furkert, engineer-in-chief of tho Public Works Department, and Mr. F. T. M. Kissell, chief electrical enginecr s left Wellington by aeroplane for Te Awarnutu, arriving at Arapuni by motor-car at 4 p.m. They mado a personal inspection of tho works in company with Mr. T. Kabono, engineer in charge at Arapuni, Mr. Furkert expressing approval of the steps taken to meet the situation. Water Pushes Through Lining The bending of the lining was observed first thing this morning, tho distortion of tiles being distinctly visible from tho bank. Tho application of green dye to the water proved that Seepage was occurring through the tiles at this spot, the colour, ing being clearly noticeable in samples of water collected from tho central underground drain at the spillway 1500 ft. distant. From observations made at the surface and a subterranean examination by the diver, it would appear that tho bank of the headrace built up with spoil during the repair operations, just inside the cut-off wall, has partly collapsed, a section of tiles bending downward. Tho bed of the channel is not affected, only portion of tho sloping side showing tho evidence of a wash-out beneath. While this development is annoying, it actually serves to confirm the observations already made as to the character and location of tho leak higher up, and the engineers aro now inoro than ever convinced that they aro on tho right track in locating the trouble. The well-boring machine, which arrived yesterday, was assembled this morning and was busy boring holes in tile bank of the headraco both above and below tho cut-off wall. This work will bo continued to-morrow in the hope of striking the route of tho seepago from tho original leak. Canvas Sheets Over Area Interest was naturally transferred today from the sector where the leak is supposed to bo to the concrete lining itself, and a dozen men were engaged lowering the canvas blankets. Tho pro- | cedure was to fasten heavy weights to tho corners of the sheets and lower them into the water from the punfc moored in mid-channel. Ropes attached to tho sheets were thrown on shore, whero they were hauled until the fabric was in tho correct position. Then tho diver would go over tho side and spread it evenly over tho tiles. Three largo sheota were thus spread, all on the sloping side. A bitterly cold southerly wind mado work anything but pleasant. An icy blast blew, and at times it was an effort to stand upright against it. Thero is no shelter from southcrlios anywhere along the banks of the headrace. The diver who had to spend a great part of tho day under water had no enviablo task, for, although ho was encased in a diving suit, his hands woro free and tho water seemed to be of a freezing temperaturo. Less Leakage Owing to tho lowering of tho water level tho current was not so powerful as during the earlier under-water operations. Nevertheless, the only way tho diver could walk upstream was to haul vigorously on a guiding rope lowered into tho water. As a result of a further opening of tho diversion tunnel gates, tho water in tho headrace lias fallen Bft. This, it is satisfactory to noto, has had tho effect of reducing tho volume of seepago from tho original leak by 50 per cent. It is now realised that there is little chance of serious damage being caused to tho neighbouring country such as might have happened had tho seepago increased instead of diminished in volume.