Sessional_Paper_1908 — Page 130

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Formation Tunnels.

The progress of the work under this sub-head is not quite as much as was expected. This is due to the unexpected difficulties met with in the nature of the material through which the long tunnel under Beacon Hill is being driven and also to the fact that great delays were experienced at home in getting delivery of the Plant required for working the tunnel owing to the workshops generally being very full up of orders.

There are five tunnels on the line but four of these can be neglected as far as expend- iture and progress during 1907 is concerned.

On a large tunnel as compared with earthwork the reverse is the case as regards expenditure and progress during the first year of construction. In the case of a long tunnel a very large amount of material and plant has to be collected and erected before a proper start can be made. This increases the expenditure per lineal foot of tunnel during the first year and it would not be right to multiply out the completion of the tunnel at the same rates as the first lengths.

Up to the end of 1907 the following had been done at Beacon Hill Tunnel :-

South Side.

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The heading had been driven 1,075 feet from the face, and a shaft sunk about 90 ft. deep. This shaft is now thrown out of use but its construction added greatly to the length of heading driven. 345 ft. of heading had been widened and fully lined.

North Side.

The heading from the open was driven 952 ft. during the year. It was started during the first week in January 1907. A shaft was also sunk 270 it. between January 3rd and October 24th and 115 ft. of heading driven towards the South and 100 ft. towards the North. These headings are in extremely hard compact rock which I hope will not require any lining of brickwork. On 31st December there was 120 ft. of lining completed.

The Plant at both sides is similar. There has been erected a complete double set of Electric Lighting Dynamos and also a double set of air compressors for driving the rock drills. These compressors are at present used for ventilating as well as driving the drills, a triplicate set of compressors are on order for ventilating when the headings get further into the hill. A great part of the expenditure up to date on the tunnel has been for the erection of this Plant and the housing of the staff which will not I hope occur this year.

Hardly of the heading has been completed and the cost per lineal foot is slightly in excess of the estimate and about 's of the widening has been executed. This widening is costing considerably more than the estimate and may result in an excess of $300,000 being required. This is due to the large amount of explosives required and the cost of the labour generally being under-estimated in the first instance through unforeseen difficulties.

As regards Brick-lining it is difficult to say how the estimate will work out. One thousand feet was estimated as requiring to be fully lined at each end. This will be exceed- ed at the South side as the decomposed granite is extending much deeper into the hill at this side than was expected. At the North side the rock got harder and compact much more quickly and the distance estimated to be fully lined will not be exceeded. The balance of the tunnel was estimated as requiring only an arch overhead to keep chips of stone from shaking out and falling on passing trains. Parts of the tunnel will not require even this so there may be a saving in the lining.

A very large amount of material is at site in the shape of bricks and timber which makes the figures for expenditure look large compared with the progress and makes diagrams and figures very deceptive.

The minor tunnels will all be built within the estimate. The expenditure during the past year chiefly consisted of the cost of materials at the site of works.

Formation Roads.

No expenditure was undertaken under this sub-head.