WORK ON HOMER TUNNEL

Southland Times, Issue 24239, 24 September 1940, Page 4

WORK ON HOMER TUNNEL

DRILLING OPERATIONS HELD UP

NEW AVALANCHE SHELTER TO BE BUILT Good progress is being made on the Homer Tunnel, but the work of enlarging it to the full size is being delayed by a shortage of drilling steel. A particularly interesting stage has been reached in the project and a good idea of its magnitude can be gained from a tour of inspection at the present time. Since last week, when drilling was stopped, the 20 men who have been at work in the tunnel have been engaged in the alteration of the direction of the passage from a point about three chains from the western outlet. Enough drilling has befen done here for the sides to be chipped and the spoil taken out. A mechanical shovel, the motive power for which was supplied by compressed air, was taken down the tunnel during the week-end to be used in clearing away spoil. Trucks drawn by winch are being used in conjunction with the shovel, but it is expected that these will be replaced by diesel dump wagons.

When completed the tunnel will be 24 feet in height and 17 feet in width with concrete portals extending as far as the scree and ground-shift at both ends. The concreting has been completed at the eastern entrance, from which for about 700 feet the tunnel is now the full size. For <he remaining 3300 feet it is 14 feet in height and 10 feet in width. The water from springs and faults in the rock which caused so much trouble when the passage was being driven through now flows freely out the western end. From the eastern to the western side there is a fall of about six chains, there being a uniform grade of 1 in 10. About 1500 gallons of •water an hour flows out from a number of rock faults, but chiefly from one from which there is a flow of 1200 gallons an hour. The faults will later be concreted in, but except for these and for the entrances, concreting will not be necessary. DIFFICULTIES INVOLVED Some inkling of the difficulties involved in piercing the Homer Saddle can be gained from a tour of inspection of the tunnel. About 600 feet from the eastern entrance are the ventilating doors which were used to block the icy winds which swept through it. So cold was it at times that water dripping from the vault would freeze into stalactites. A little further down the tunnel narrows and at this point the holes which have been drilled preparatory to blasting may be seen. It was this work that was stopped by the shortage of drilling steel. A short distance, from the western slope of the saddle, the tunnel veers to the south. When it is fully enlarged the centre line will be a short distance further out than it would have been had it been kept straight according to the original plans, and a great mass of scree which would have had to be shifted will be avoided. The old heading can be seen some distance from the entrance.

The road down the Cleddau Valley from the western outlet will of necessity have to be winding, as the contour of the ground is difficult. It will lead out into a sharp U bend, turn back towards the tunnel, and then back again before continuing down to the Milford road-head, which is about two miles away. Milford is 10 miles distant.

On the Cleddau Valley side of tire tunnel, an avalanche cover similar to that built on the other side is to be built to protect the men. It will be about 400 feet in length, and a start on it will be made, according to present 'plans, before the end of the year. No repetition of the previous disaster which occurred is desired, for great avalanches could come down Mt. Bell as one did lon the Hollyford side of the tunnel three years ago. What remains of a small avalanche which came down Mt. Bell about a month ago can be seen below the tunnel outlet now.

HARDNESS OF ROCK The hardness of the rock has made the job of the men engaged on the drilling and blasting, particularly arduous. It is a job also that requires experienced men, and in view of this tunnellers were brought down from the north when the work started. Most of them have gone now, however, and the gang of 20 men at work inside the mountain is composed mainly of Southlanders. Mr J. Craig, manager at the tunnel for the contractors, Downer and Company, Ltd., thinks highly of them and considers the gang is the finest which has worked there.

Although the rock is not actually granite, it is something very much like it, and such is its hardness that the drills do not stand up to it for any great time. Constant tempering is necessary, but many snap nevertheless. The tempering is done in oil and a high degree of skill is required. That this difficult job is being carried out with the best possible results was proved when a drill was sent to the United States for inspection and testing. It was returned with the comment that the tempering was perfect.