WELLINGTON and WAIRARAPA RAILWAY.

New Zealand Mail, Issue 27, 29 July 1871, Page 6

WELLINGTON and WAIRARAPA RAILWAY.

Mr O’Neill’s Report. Wellington, 20fch July, 1871. Sir, —In obedience to your instructions of the 30th May, to survey and report on proposed Wellington and Wairarapa railway, between Pakuratalii and Featherston, “ Whether it is feasible to carry the line along the Rimutaka Valley, with a tunnel through the saddle of the hill, and, if feasible, to state distance. length of tunnel, and estimate of cost,” &c.: I have now the honor to report that I have taken a careful section of the main road between Pakuratahi and Featherston (see drawing No. 1), and a section along the main creek on both sides (see drawing No. 2). I then measured the direct distance near the telegraph line from one of my bench marks in the creek at the foot of the spur near the roadmen’s houses, to a bench mark in the creek on the Featherston side of the range. The height of the ridge on this line I found approximately by the Aneroid. (See drawing No. 3 ) I have also sketched on road plan the position of the creeks, and the proposed line of tunnel. (See drawing No. 4.) In the third section (drawing No. 3) I found that the shortest line for a tunnel was gained, giving an easy gradient and a straight line — a most important consideration in the construction of a tunnel.

The length of the tunnel, as shown, is 130 chains, and the length of line along tin route from the Golden Fleece Hotel, Pakuratahi, to Featherston, is 8f miles. The distance between the same points, along the main creeks, is 9% miles. The length of road between the same points is Ilf miles. The datum I have adopted is 54 feet below the level of the floor of Abbot’s (Mr Shirley’s) Hotel, and the following are a few of the principal heights above datum Pakuratahi Hotel ... 615 36 Summit of road ... ••• 1723 62 Abbot’s Hoted ... 54 00 Tunnel (Pakuratahi side) ... 859 50 Tunnel (Featherston side) 665 00 COST OF TUNNEL. 130 chains (including brick lining) at £660 per chain £85,800 I have based my calculation of the cost of the tunnel on the following dimensions Height above rails ... 15 feet Breadth, 3ft 6in gauge ... 12 feet 6 inches and cased with brick work on sides and roof. The usual dimensions of a tunnel in England for a single line of railway, 4ft BJin gauge, are 20ft above rails, and 15ft greatest breadth. I consider the dimensions of tunnel proposed by me as quite sufficient for the railway, and the cost is considerably lessened. I believe the tunnel could be made without any serious difficulty. The excavation would be generally through rock from end to end. The depth being about 1000 feet below the ridge, the rock may be found solid ; although where it has been exposed to the effects of the air and rain, decomposition and disintegration have taken place, but I do not think rapidly. In the event of the tunnel being proceeded with, and the rock turning out as solid as I anticipate, very little brickwork, except near the ends, will be necessary, thereby causing a large reduction in the cost stated by me. GRADIENTS. Tunnel ... ... ... 1 40 Do to Featherston,.. ... lin 40 Do towards Pakuratahi ... lin 60 The last gradient may be altered, dependent upon the level of line near Mungaroa. In conclusion, I take the liberty of suggesting that in constructing the line from the tunnel on either side, a good portion of the work should be done on “ trestle work,” and as much as possible on the timber slopes of the hills, for I think it advisable, in this, country, to avoid as much as possible cutting into hills where slopes are very steep. —I have, &c., Charles O’Neill, C.E. The Hon. W. Fitzherbert, Superintendent, Wellington.