WONDERS OF OTIRA TUNNEL.

Shannon News, 31 August 1928, Page 3

WONDERS OF OTIRA TUNNEL.

! LONGEST IN THE BRITISH EMPIRE. ADDRESS BY MR J. A. SMITH. Whatever the cost may have been, New Zealand has a monument of engineering skill in the Otira Tunnel. The description of it given by Mv J. A. Smith, A.M.1.E.8., engineer to the Horowhenua Power Board, in an address to the Levin Chamber of Commerce Lunch Club, in. the Oxford Tearooms Friday, was such as to arouse the sight-seeing instinct in no uncertain manner. Bare statistics relating to such a work would leave only, a momentary impression, unless repeatedly studied; but a personal narrative, illustrated by fine photographs, gave those\ assembled an excellent idea of the romance of a great enterprise, its strange setting in alpine country, and the almost infinite mental and physical resource that ensured its completion.

The attendance was one of the best recorded at local Lunch Club gatherings, and it drew special praise from the newlv elected president of the Chamber," Mr C. S. Keedwell, who presided. He said he hoped that the same willing support would be forthcoming for the Chamber itself, and it remained for the members to assist the executive in this way. Apologies for absence were received from Messrs P. Meyer, F. C. Parker, J. Har,vey and E. I. Parrington. In introducing the speaker for the dav, the chairman said that possibly ma'ny New Zealanders did not fully realise what a wonderful project had been carried out at Otira. and for which their fellow-countrymen were in the main responsible. THE COUNTRY DESCRIBED.

At the outset Mr Smith explained that the Otira tunnel is a connecting link between the east and west coast railway systems of ,the South Island, and he mentioned'that the Island is about 500 miles in length and* 120 miles wide, with a mountain range running from the top end to very near the bottom. No other railway but that which passed "through the Otira tunnel ran f/oni east to west of the South Island, and the old West Coast road was still the onlv one that crossed the Island. The road went from Springfield, on the Canterbury Plains, over Porter's Pass, thence to the Bealey and up over Arthur's Pass, 3000 feet high. From there it went down, the Otira Gorge and through to Kumara. Arthur's Pass was named after Arthur Dudley Dobson, who surveyed the Pass and laid out the road. The 'railway did not take exactly the same route as the old road, but it was close beside it for a considerable distance. |On the western side it started at Greymouth, followed the Grey River on the south bank to Stillwater, which was the junction for the line which ran to Reefton and which would eventually go to Nelson. Continuing, -the line to Canterbury followed the Arnold River, skirted the north-east shop of Lake Brunner, went through a natjhral depression and across %ts/ crossed. ;the Teremakau River, ran up the south bank and then followed a tributary, the Otira river, to the Otira station, three miles beyond which was the tunnel. On the eastern side of the tunnel was Arthur's Pass station, very close to the entrance. The line then ran down the Bealey Gorge and the Waimakariri River," coming out at Springfield, where the coaches used to leave the old railheadfor their journey to the West Coast. % Apart from the tunnel, the line had been a very hard one to build'in certain places. Between Arthur's Pass atad, Springfield, at Staircase Guilly, there was a length of nine miles in which there were 17 tunnels, the longest of which was about 2000 feet. Therewere also three very big steel viaducts, one of which was nearly 300 feet above the bottom of the gully that it crossed. EARLY RAILWAY OPERATIONS. The line was started, by the N.Z. Midland Railway Company, which constructed about 35 miles between 1880 and. 1895. The company built a line to Reefton and operated trains from Bruhnerton to Reefton, the old Gov-, eminent line being from Greymouth to Brunnerton. At length the company found that it had not enough money, and in 1895 the Government took ovei the enterprise. The original idea had been to cross right over the top of the Gorge by means of the Fell cen-tral-rail system, which was in use on the Kimutakri" Incline; but the Government, on investigating the matter, decided on a tunnel. Their proposed tunnel was one having a length of six miles and a grade of one in 37. An eminent engineer, Mr V. G. Bogues, was brought out from America in 1902, and he suggested a short summit tunnel with a grade of oik; in 32. When Mr Bogues had pronounced the tunnel project feasible, the Government/ vvent into the question again and finally decided on a tunnel in the present location, with a length of s:{ miles and a grade of one in 33. Surveys were then made in order to get the precise levels, and this work was very difficult on account of the nature of the country. At this stage Mr Smith exhibited some large pictures to show the locality of the tunnel, photographed from both sides of the range; and they gave a convincing impression of the difficulties that must have hampered both survey and transport. Notwithstanding the various disabilities encountered, however, the work was carried out very accurately. TUNNEL STARTED BY CONTRACTORS. Continuing, Mr Smith stated that a contract was let, in August, 1907, to J.'H. McLean and Sons, at £599,794. The Government of the day were evidently rather optimistic, as they only gave the contractors five years to complete the job. The work was commenced in April, 1908, Sir Joseph Ward firing the first shot, on the Otira side. In July, 1909, work was commenced on

the Arthur's Pass side, and operations went on until 1912. M ,„ n , irrv oTr GOVERNMENT TAKES OVER WORK The contractors spent about £250,000 on plant and material, but were unable to complete the work in the time specified, and after negotiations with the Government it was taken over by the Public Works Department. At that time two and "one-third miles of the tunnel had been driven and If miles of it lined. Owing to the War and the consequent shortage of labour, the project was delayed considerably; but on 'May 7th, 1918, the workers at the Arthur's Pass side could hear the shots that were being fired by those at the other end. The gang was thus stimulated to great energy, afnd on June 29th the men on the western side could hear the rock drills working on the other side; the distance separating the parties being about 200 feet. The bottom headings met on July 20th of the same year. The lining of the tunnel was completed in August, 1921. When the gangs met they had driven 3 miles 68 chains 10 links from the Otira side and 1 mile 37 chains 40 links from the Arthur's Pass side. As showing the accuracy of the surveying, Mr Smith stated that the difference between the calculated and the actual length of the tunnel was 3(3 inches, the difference in; the level H inch, and the differ-encc in the alignment fin. In the famous Mont Cenis tunnel through 'the Alps—a tunnel with a length of 7-| miles—the difference between the calculated and the actual length was 15ft. between the levels 12in., and between the alignments nil. The actual length of the Otira tunnel was 5 miles 554 yards; it was the seventh longest in the world, and the longest in the British Empire. STRAIGHT FROM END TG END. A noteworthy feature of the Otira tunnel is that 'it is dead straight, and to demonstrate this, Mr Smith showed, iu a photograph taken inside the entrance, a white spot in the middle, representing the opposite mouth of the tunnel. He stated that, on a clear, sunny day, if one were riding on _ the engine he could see the'spot of light quite distinctly, but as. the journey was continued the light disappeared for a time owing to its being obscured by a haze which came down from the roof of the tunnel. The light reappeared when the observer was about half a mile from the outlet.

One of the photos was very interesting as proof of the severe cold experienced in the locality, great icicles being seen hanging from the roof, while , lumps of ice were shown on the permanent way, where they had fallen. The tunnel contains a single track. The height of the. structure is 15ft 6in., from the rails to the roof, and the maximum width is 15ft. NO GOLD DISCOVERED.

Mr Smith said that, when the driving of the tunnel was in its early stages, there was great speculation as to what might be met with in the heart of the mountain,' some expectations beingentertained of finding gold, which did not turn out to be the case. In the Otira river there was a warm spring, and when the Mont Cenis tunnel was being driven hot water was encountered, but nothing of the kind was found in the Otira tunnel. It was monotonously alike the whole way through, except that the consistency of the rock varied greatly. It changed very suddenly from very hard to medium or soft." Sometimes very slow progress would be made in drilling through a slatcy shale, after which there would be a quick transition to soft rock, in which the drills would work well. The rock was in layers that ran pretty well in the direction of the tunnel, a circumstance which made it fairly easy, for "shooting." It was all of a scaly character, and had to be temporarily timbered all the way until such time as the lining could be put on. A bottom heading was first driven, this being Bft high by 10ft wide. When this was sufficiently advanced, the top heading was brought in. This system allowed nearly twice as- many men to be at work as there would have been with onlv one face. One heading was kept, well ahead of the other, and -as it proceeded the men behind came up, broke down the remainder and cleaned if up for the lining. Ten-ton electric mininglocomotives were used for removing the spoil and coming back with material. A trolley wire was suspended from the top of the tunnel as far as the line went, and from that point an insulated training cable Was taken up to the face. In' some cases the workers had winches run by compressed air, which hauled the spoil out until the loeomdtives picked it up. FEATURES" OF CONSTRUCTION. The tunnel, Mr Smith added, was lined the whole way through. The sides and footings were of concrete, and the arch top was covered with concrete blocks manufactured outside the tunnel. Half the. rock-material needed for making the .concrete was obtained from tin- spoil taken out of the tunnel, and the balance of the metal was obtained from quarries at either end of the tunnel. Sand was not obtainable, owing to the altitude, and in lieu thereof the contractors had to utilise gravel from the river-bed, crushed fine. Most of the work on the tunnel was done from the western side, on the uphill grade, for the better handling of the material and to get rid of the water. There was no abnormal flow, but a fair '.amount of water all the time. T : r_' maximum was 3000 gallons a minute, put of one end. It ran out of the western side by gravity, but on the eastern side it had to be pumped out. Ventilation was an important item in such a long tunnel. At first the air used to be forced through pipes to the face, but in that case the foul air was blown back through the main tunnel; so the procedure was reversed, and 16in. pipes were used for blowing out th.j foul air from the face, while fresh air came in through the tunnel. GENERATING OF POWER Mr Smith went on to say that steam had to be used to generate power for working the main line, as there was not sufficient water in the rivers in winter at the altitude to run a large

hydro station. However, power that was used during the construction, for working the air compressors and the electric locomotives was generated by two sniali hydro plants. The mail, power station, which was situated at the Otira end, was furnished with three Babcoek and Wilcox marine type watertube boilers, supplying* steam to two horizonal turbines, each of 1200 k.w., generating direct current. The load came on and went off very suddenly, and the boilers had to be of a quick-steam-ing type. There were two steam-dri-vcre alternators, v/hich supplied the current for townships, for workshops, for lighting the tunnel, and for the signals down to Stillwater, on. the West Coast, and to Avoca, on the Canterbury side. In the tunnel there was a. lamp at every 82A feet. The water that supplied the condensers was taken from Goat Creek, 025 feet above the power-house, and by means of a Pelton wheel it drove an alternating current generator. The over-flow was brought down to the air extraction pumps, and the surplus from that went to a reservoir above the power-house to supply water for -the main condensers. ELECTRIC LOCOMOTIVES. Explaining the method of traction through the" tunnel, Mr Smith stated that there were 'live locomotives for hauling. They had eight, wheels and weighed 50 tons each. There were four driving axles, with a 170 b.h.p. motor on each axle, and the current went through one motor first and then through the. others, absorbing the 1500 volts that was on the main line. Usually two locomotives were run together, and they would draw 250 tons through the tunnel. The power required to take the train through was 1200 kilowatts, which was about equal to the maximum day-time load in the Horowhenua Power Board's district. The tunnel had an even grade of one in 33, equivalent to a rise of 2ft per chain, or 850 feet in the 5} miles. The train was pulled up this grade at a speed of 16 miles an hour, taking 20 minutes to pass through the tunnel, and 30 .minutes for the journey from Otira station to Arthur's Pass. On the return journey the train Avcnt, through the tunnel in* 17 minutes. No running power was used then, owing to the down grade, but the motors were turned into generators and they sent the current through a resistance which was variable and thus they provided a braking effect on the motors. With an ordinary train under these circumstances it 'was not necessary to. use the Wcstinghouse brake at all. The speed on the down journey was about 20 miles an hour. The maximum traffic through the tunnel in a day was eleven trains, with a tonnage of 2750, exclusive of passenger trains. The record for a week was 12,450 tons, from west to east, exclusive of passenger trains. The daily average at present was eight trains, with 2000 tons. The tunnel was opened in August, 1923. A COLD LOCALITY.

Speaking of the climate, Mr Smith said that it was fairly severe in the winter, the Otira station being 1260 ft and Arthur's Pass 2435 ft. above sea level. The 'average .annual ,rainfall was 195 in. After the completion of the tunnel and when the electrical installation was being made, a very severe winter was experienced. At the Otira end the record low temperature was lldeg. Fahr., and the highest 82 deg. There had been one period of 36 consecutive days when the thermometer did not rise above freezing point.

The address was listened to very appreciatively,' and at its conclusion a hearty vote of thanks was passed to Mr Smith, on the motion of Mr F. R, Stedman, Levin stationmaster. In the course of his remarks, 'Mr Stedman mentioned the rapidity with which the traveller could go from one part of the Dominion to another./He could leave Levin at 4.50 p.nw-'and be at Greymouth by 4.30 p.m. next day, travelling via Lyttelton and Christehurch, and leaving the latter place for Greymouth at 10.15 a.m. The first-class single fare from Christehurch to Greymouth was £1 2s sd. The completion of the Otira tunnel and the consequent link-ing-up of the east and west coasts' by rail had brought about an enormous saving in time and money. Grain was now hauled from Christehurch to Greymouth— 145 . miles—for*. 16s 6d a ton and a truck of stock would go across for less than £5.