ARAPUNI TUNNELS

Dominion, Volume 25, Issue 169, 13 April 1932, Page 11

ARAPUNI TUNNELS

Two Miles of Galleries CHECK ON LEAKAGES Gigantic Invisible Work A tour of the wonderful subterranean tunnels and galleries at Arapunl, bored deep under the spillway weir, headrace and falls as part of the remedial measures now brought to completion, was made by a “New Zealand Herald” representative recently. He walked below ground for two hours, seldom traversing the same tunnel twice, and covered two miles under the earth before he emerged once more dntb the fight of day. This journey through Arapuni’s extraordinary catacombs revealed the gigantic amount of invisible work which has been carried out in the country affected by the trouble in June, 1930. Who would guess, watching the diverted Waikato pouring over the spillway and falls, that 140 ft. beneath the surging water men were patrolling hidden galleries day and night, watching for the first sign of leakage, peering at V-notches embedded in the floors and recording their observations in little notebooks? Two miles of tunnels, deep down in the earth, ablaze with electric light, crossing and recrossing each other —a veritable witch’s maze! Donning gumboots and an overcoat, not always essential, for the tunnels are dry for the most part, the “Herald” representative was conducted on his tindergtound journey by an engineer. A guide was necessary, for the chances are a hundred to one that a stranger, once in the bowels of the earth, rvould lose himself in the baffling series of intersecting tunnels, and fail to find bis way out for a good many hours. An Eerie Silence. The first tunnel had its entrance in the gorge near the power house. Unlocking the padlock on the gate, the guide led the way into a brightlylighted cavern that penetrated the hill underneath the transformer station. After walking for a quarter of an hour in eerie silence, the roof or the cavern almost touching one’s head, a faint rumble was heard ahead. “We are under the spillway,” said the guide. Another tunnel junetioned to the left. This, it was explained, followed the entire length of the forebav and headrace and iuto it ran a scries of porous drainage channels. There was a considerable quantity Of water flowing through this tunnel under the headrace. “That is not . leakage through the tiles.” said the engineer, observing a questioning looic on his visitor’s face. “That is puiely seepage from the country on both sides of the headrace. We have deliberately set ourselves to catch that water by putting in porous shafts up to the surface/’ The journey proceeded ui an upstream direction directly below the crack that developed nearly two years ago. The gallery was perfectly dry, except in one place where a tiny trickle of water percolated through the breccia. . ... . "That,” said the engineer, is part of the crack. Switch on the torch and you will see the filling of concrete that was forced down under pressure from the surface. We are 140 ft. underground, .vet the. concrete has been forced down here all the way from the top. That trickle is nothing. It does not come from the beadrace, but from the surrounding country, which has been soaked by the recent rains. When it stops raining there will l»e no sign of a trickle.” Wonderful Gallery System. An opening aloft suddenly came in co view. Looking upward, a tiny circle of daylight gleamed out of the darkness. It was the opening of one of the two great shafts, .150 ft. deep, connecting an elaborate system of Inspection galleries which run at right angles to the headrace near the point where the headrace lining commences. Every 40ft. up a gallery branched away from the shaft,, enabling a. minute examination to be made, at varying depths, of an entire cross-section of the country beneath the headrace. With a “Watch your step!” the engineer commenced to climb the Iron rungs embedded in the concrete Jibing of the shaft which took the place of a ladder. It seemed like 10 minutes before the first gallery was reached. The bed was its dry as a drawingroom carpet. So was the bed of the gallery above, only 40ft. under the water. "That shows that not it drop of * water is coming through the tiles that line the headrace,” said the guide. “Now let's get back.” On the return several diversions were made tun! three limes Ibe travellers came out into daylight in the gorge through openings in the cliff. Under the falls the faintest rumble overhead indicated the spot where the water was tumbling over a crest—a somewhat forbidding sound to the visitor, but all in the day’s work for the engineer. On the way out they stopped to look nt. the glow-worms which are gradually making a new home for themselves in the tunnels. As the lock of the tunnel gate clicked behind him the guide consulted his watch. If was 3 p.m. The journey bad occupied over two hours.