MOUNTAIN TUNNEL

Waikato Times, Volume 125, Issue 20887, 19 August 1939, Page 5

MOUNTAIN TUNNEL

HOMER SADDLE WORK THROUGH GRANITE-LIKE ROCK Progress made on the Homer tunnel, 4000 feet long, being driven underneath a tangled mass of mountain ridges that lie across the route of the new motor road between Te Anau : and Milford Sound, was described by Mr A. F. Downer, of Downer and Co., contractors for tlm tunnel, jn an interview with the Evening Post, Wellington. He said that 900 feet remained to 'be pierced and it was expected that the heading would be through early in the New Year. This will by no means mark completion of the job, because the hole through the mountains will then have to be enlarged to the full size of 24 feet wide and 17 feet high—sufficient to provide a two-way traffic route. The completed tunnel will be the longest traffic tunnel in New Zealand. The tunnel, which is situated 14 miles from the head of Milford Sound, has a grade of one in ten from the Milford end to the eastern portal and is approximately 3000 feet above sealevel. in the heart of bare, rocky mountains above the bush line. Normally an inclined tunnel of this kind would be tackled from the lower end so that use would be made of gravity to remove material and water, but because of the inaccessibility of the western end driving had to be commenced downhill, which has involved special problems. Electrical Gear Electrically - operated pumps work ! night and day to cope with the water, continuous fans control ventilation, , and electric haulage has to be used to bring material from the face to the portal. This is also the reason why the whole area of the tunnel is not being taken out in one operation, for once an opening has been made through to the lower end it will be possible to deal with the remainder of the material and water by gravity. At I present a section of rock nine feet high is being removed. The tunnel is being pierced through solid rock of a granite-like nature and is so hard that when the pneumatic drills begin to bite into it the drillpoints bring forth a shower of sparks. Explosives have to be used all the way, and for most of this shooting one of the most powerful blasting agents procurable is being used. Work has now been proceeding 18 months, and this winter, thanks to the measures taken by the Public Works Department to protect the men from avalanches, it has been possible to continue operations throughout. Mr Downer said that during the winter months only one shift is being worked because of the danger, but during the summer the job will go on continuously again. He added that the covering provided by the Public Works Department to protect the men on their way to the tunnel, and other safety measures, have been very sucj cesaful. Avalanche Danger Mr Downer said that the most dangerous type of avalanche comes down i during the winter months when the i snow is falling. Huge masses of ice I and snow carry everything before I them and in their fall set up a powerj ful gust of wind that is strong enough jto do considerable damage. Work was | recently held up for a fortnight when ! an avalanche wrecked the power lines | between the tunnel and the Public ! Works Department powerhouse four i miles away. The avalanche itself did | not strike the lines, hut the wind set j up by it was strong enough to wreck la number of power poles. ! During the recent heavy snowstorm six feet of snow fell at the tunnel and j the Department's Diesel-driven snow | ploughs were faced with a big job to j clear the roads. Mr Downer said that during a normal winter the snow j ploughs are required to keep open | about six miles of road, but this I winter because of abnormal conditions,! ploughs have been required on 120 miles of road as far along the route as Mossburn. There are at present 30 men employed on the job, ten of whom constitute a shift. Even at this time of the year the completed section of road from Te ! Anau to the tunnel carries a considerable amount of lorry traffic required to bring supplies from the railhead, but Mr Downer said there would be a tremendous volume of tourist traffic during the coming summer. Mr Downer, who makes periodic visits to the job, returned to Wellington on Saturday after a fortnight's stay at the tunnel.