THE TUNNELLERS OF TAWA

Dominion, Volume 22, Issue 75, 21 December 1928, Page 9

THE TUNNELLERS OF TAWA

HOW THE CONSTRUCTION WORK IS PROCEEDING ENGINEERING NICETIES THE MEN AT THE FACES Except for a rampart of rubble slowly curving into tiie sea, there is little sign along the Hutt Road of the active burrowing above. Not even the whirr of pneumatic picks and similar implements beloved by tunnellers, breaks through the zip of tires on the road. But all the same, the tunnellers of Ngahauranga and of Tawa Flat are busy—very busy (writes E.A.A.) “This,” said the engineer in charge, as he shepherded me along a sheep track leading to au entrance in. the billside, reminiscent of those half-forgotten dugouts in France, “this is merely a side tunnel, connecting with the main tunnel inside the hill. When completed, it will facilitate work, and give an outlet for the disposal of the rubble.” Into the dim, half lights of this side tunnel, a collection of pipes of all sizes lost themselves in the long perspectives of wooden props. A little, muddy stream ran out along the floor; walking was unpleasant. Some eight chains inside, amid a heavy downpour of water trom the roof above, four men were working at the face. The staccato thuds of air-driven picks, the rustle of sliding earth, and the scrunch of shovels, filled the half-lit shadows with uncchoing noise. Everything dripped—water oozed from the side walls, springs gushed from lhe floor, and the air was humid. After making steady progress at the rate of some 90 feet a week, the tunnellers had struck a bad patch of spongy shale, full of underground water catches and springs; the tunnels, in an effort to avoid the worst patches, dodged and twisted, and progress had fallen to a bare five feet a week. The twists and turns, of course, did not matter, for no trains would' run along this side tunnel. “You can’t tell when you are going to strike water, and, consequently, it is almost impossible to say how long ling will take,” my guide told me. These difficulties were equally present in the main tunnel, only some three chains straight through the sponge of shale in front. Two Tunnels Being Driven. Altogether the Tawa Flat scheme will consist not of one long tunnel but of two: one three-quarters of a mile long from the sea to where the gorge dips deep towards the road, and the other tunnel onwards to Johnsonville some two and a half miles long. A bridge across the road links these tunnels. We entered the far entrance of the shorter tunnel that starts at the sea. Here there was more room, although the full 26 feet by 20 feet of the actual completed tunnel had yet to be done. Two lines of temporary rails ran inwards. I was glad of these rails, for little else showed above the water, and by a series of Blondin-like balancing feats it was possible to remajn tolerably dry shod. Strutted with New Zealand birch and white pine this tunnel pierced a straight line right into the hills. From afar there came a high metallic clanking that grew rapidly louder and an electric locomotive with a cargo of rubble pushed us to one side among the puddles, clanked drearily onwards towards the entrance, and was gone. Soon, however, the air was full of rather melancholy rhythmic thuds and heavy breathings not unlike city trams at rest, but slower. The song of the pumps, these sounds, driven by compressed air. These pumps have sung their song for six months now, and are likely to continue for another three or four months; all day, all night, all Sunday, too, the pumps are hard at work keeping the water under control and shooting it out through a six-inch pipe into the stream that runs beside the road. Sometimes so great is the flow from these internal springs that it is all the pumps can do to keep the water under control; fortunately it is not so bad now. • The tunnel branched off. the one to the left being the other end of the side tunnel we had first visited. The Tunnellers at Work.

At its face men worked in one huge puddle tliat filled again as fast as the pumps drained it; The tunnellers, experts—for all tunnelling work is done by experienced miners—tall, lean men, moved about quite unconcernedly, with the slow certainty that gets things done quickly. They had just blown in another

few feet of virgin tunnel, and were busily shovelling the debris into au electricallydrawn hopper. I was told that whenever practicable nine boles were drilled in the face, gelignite inserted, and after discreetly retiring, the whole was exploded. This had just been doue, and after being taken to the tunnel entrance, and slid down a chute into lorries, the rubble would be carted to that ever-growing promontory beside the Hutt Road. Six hundred thousand tons of soil will be carted thus, burrowed from the bowels of the hills to make a little bit of land where once was sea. Pumps breathed with melancholy thuds, compressed air hissed and the muffled rattle of pick and shovel only added to a scene already weird. At intervals along, the tunnel electric lights vainly attempted to look bright, but only succeeded in making new shadows. It was just the same at the face of all the headings. At these headings men were busy working in eight-hour shifts gnawing their way through the hills towards another little band of toilers, perhaps a mile away through the earth; all slowly moving towards one another a few feet a day. Whilst the shorter tunnel is only being attacked from either end, the longer tunnel is being worked at no less than four places. To make this possible a shaft 130 feet deep has been sunk in a deep ravine a mile or less from the Johnsonville end. and calculated to be mathematically above the line of the tunnel when completed. At the bottom of the shaft more men are busy at two faces working away from one another, one lot tunnelling towards Tawa Flat, and the other towards Ngahauranga. “I suppose the pumps go all out down there?” I asked, for beside the shaft a stream rushed by from the hills beyond. “Oh, no,” said the engineer in charge, “it’s funny, but there isn’t a drop of water in the workings below, in spite of the stream; one cau never foretell these things.” At the Johnsonville end quite a business-like tunnel bas been completed. In fact, one could imagine the “Limited” tearing into its entrance with a roar and a whistle. But it would not get far even if there were suitable lines—only a few chains; then the passengers would find themselves among the tunnellers of Tawa Flat with their air compressors, their melancholy pumps, and their gelignite. Auxiliary Artisans.

Subsidiary to the tunnelling operations, a multitude of industries has sprung up. Blacksmiths weld and hammer, and shape the drills with modern, air-driven presses that, mould the red-hot rods to special shapes, suitable for drilling rock. Carpenters hare whole rows of sheds in which to plane and saw, whilst engineers are busy round the air compressors. I saw these air compressors. When completed, there will be three of them, driven by powerful electric motors, each of 160 h.p., capable of supplying all requirements. They are each capable of supplying 160 horse-power of compressed air. At Johnsonville and Khandallah. villages have sprung up, capable of housing the 380 workers who toil amongst the tunnels and its offshoots. All the plant, however, has not yet arrived, and the engineers await more electric locomotives, more mechanical excavators, and a hundred and one other things, before they really take off their coats and go all out. Co-operative System.

As far as the labour is concerned, the tunnelling is done on the co-operative system. A party of men under a head man. contract to do the tunnelling at so much a foot. Although the average price depends on the conditions at the face, such as the soil, difficulties regarding water disposal, and other factors, the price varies accordingly. . Once the price is settled, it is up to the party to make as much out of a day’s work as they like, and slacking brings with it less pay. Under this system, the rate of pay is on the whole considerably above the union rates, and the men are satisfied; the engineers are satisfied, too, for there is a strong incentive to get the work done. Explosives have to be provided by each party, and the head man, who works the day shift, sees that all the necessarv tools and stores are available. So far, in spite of the obvious difficulty of fixing a price, the scheme has proved very successful. On an average from three to five-feet a day is made good in the tunnelling, under this system. Engineering Niceties. No little skill ie required ou the part of the engineers to insure all these isolated tunnels joining up, particularly as the tunnels slope steadily towards the sea. Before the tunnelling started, a careful survey was made of the area. Posts were laid out behind the tunnels, and marked with lights, so that the straightness of the tunnels can be checked with theodilites, as the work proceeds. For instance, one check mark is over at Pipitea Wharf, and another behind the tunnel at Johnsonville, not to mention many other checks at different places m the hills. Perhaps one day, some three or four years hence, the Minister of Railways of the day, and the Mayor of Wellington, will break down the last remaining shovelful of earth, and shake hands in the approved style, and Wellington will have its very latest tunnel. Meanwhile, the melancholy throb of the pump, the rattle of pneumatic drills, the drip, drip, of new, tapped underground springs, and the shattering blast of gelignite, will hold sway far below the peaceful hilltops of Ngahauranga and Johnsonville.