TUNNELLERS RESUME

Sun (Auckland), Volume IV, Issue 1005, 23 June 1930, Page 10

TUNNELLERS RESUME

OPERATIONS ON ARAPUNI INSPECTION TUNNEL MR. R. SEMPLE’S VIEWS From Our Oxen Correspondent ARAPUNI, Sunday. Operations on the Arapuni inspection tunnel, on which work -was stopped by the Government following a claim made by the conference of the Xew Zealand Workers’ Union that it was unsafe, are to be resumed by the tunnellers this evening. This decision followed upon an inspection made on Saturday by Mr. R. Semple, M.P., who claimed to be acting with the authority of the New Zealand Workers’ Union and the Minister of Public Works, and who later gave an assurance that the Inspection tunnel was quite safe, since the water pressure had been removed. Mr. Semple, who was accompanied by Messrs. W. Lee Martin and R. MeKeen, M.P.’s, also held that there was no danger in the penstock tunnel, which was being steel-lined. A precautionary measure suggested by Mr. Semple for operations in the exploration tunnel was that a 12ft bore should be kept ahead of the face to tap any water cavities that might exist. This plan Mr. T. Rabone, engineer in charge, promised to communicate to the Public Works Department. A FIASCO? As a miner of 27 years’ tunnelling experience and a student of mining, Mr. Semple declared bis conviction had been strengthened that the whole scheme was a fiasco. He advised the undertaking of a complete investigation, and announced his intention of recommending that Parliament set up a special committee, with power to make full inquiries and to obtain the assistance of eminent outside engineers. From the outset, Mr. Semple said lie had held the opinion that the scheme was a gigantic blunder and waste of public money. On inspecting the country with a view to tendering for the tunnelling for Armstrong, Whitworth, he declared he had condemned the scheme and declined to enter for the contract. At the invitation of the English firm, when he went to Arapuni to drive a diversion tunnel, he formed the impression that it was disturbed country, largely of volcanic ash. The real danger, in his opinion, was not at the dam, but laj in the strip of land that separated the headrace from the old river bed, and which had been proved to be a saddle of land lying either on its original foundation or had been built up by floods. He held the view that it was sheer madness to build a powerhouse and transformer station on this strip, which was composed partly of a soft, sugary strata of pipe clay and mud, which was distined to allow water to pass through from higher levels to the old bed. EARTH MOVEMENT

An explanation of the earth movement was offered by Mr. Semple. Continual and persistent blasting shocks had weakened the land opening up the strata, he said. The ventilation thus caused had resulted in the softening of the strata, and the pressure of water had set up a certain vibration. These factors, combined with the breathing action of the penstocks under the load, had set up the earth movement, this rendering water saturation easy. Mr. Semple contended that the way the water was coming through the cracks confirmed his opinion that the works were built on a shifting morass". The falls bed had eroded considerably in the past year, he said, and had now only seven chains to go to reach the weir. The river seemed to be eating back to the old riverbed more quickly than anticipated. In Mr. Semple’s opinion the suggested concreting of the falls was stupid in the extreme, because no amount of concrete would withstand the terrific force of water in flood times.