TUAPEKA RAILWAY.

Tuapeka Times, Volume III, Issue 199, 23 November 1871, Page 5

TUAPEKA RAILWAY.

THE PROVINCIAL ENGINEER'S REPORT. To the Secretary for Lands and Works,

Sir, — In accordance with yonr instructions, as per memo,, of number and date in margin, I have the honour to inform you that I have had parliamentary survey executed of the proposed railway between Tokomairiro and Tuapeka, and now beg to report upon the engineering ro'nts involved.

The line leaves the Otago Southern Trunk Kail way at 36 miles 6 furlongs from Dunedin, and adjoining the present main road from Tokomairiro to Tuapeka, and proceeds across the plain to the gorge through which the south branch of the Tokomairh'o river flows, proceeding xip it io the confluence of -the Talla Burn ; thence ascends the gully thereof to to the watershed, separating that water from the Manuka Creek. The summit of this saddle is 482 69 feet above the commencement of the line, and too high to be passed in open cutting ; consequently a tunnel of 670 yards is proposed through to the drainage ground of the Manuka Creek, at that part known as Gardner's Flat, Before fixing upon this line, I considered fully the question as to whether or not the gorge of the lower part of the Manuka Creek, up which the present main road runs, would be suitable for a railway ; but I found that owing to its rapid rise at that point, — being from 1 in 15 to 1 in 35, — and that the gradients could not be materially improved by commencing the ascent at any .distance back from the junction of the creek with the Tokomairiro river, except at an enormous outlay, and that moreover the works for nearly two miles would consist of rock cutting jthrough. a narrow, tortuous gorge, I came t to the conclusion that the line as surveyed .w.quld give a much better gradient, and \at less expense, than could be obtained .otherwise. The line, after passing through .the innnel, .continues up the Manuka Creek the ,whole way to the summit at ihe Round Hill saddle, where the ground is 714 feet above the beginning of the line ; and the formation of the railway is proposed to be 594 54 feet above the same point, in a distance of 9 miles 11^ chains. With the exception of 65 chains at the junction with the Southern Trunk, and at three-tenths to three-fortieths, which are level, the line is constantly rising towards the summit, so that nothing is lost by intermediate falls. The gradient on this part, which is undoubtedly the worst on the line, vanes from 1 in 325 to 1 in 46, the latter being the ruling gradient of the railway. The saddle at the Round Hill will be pierced by a tunnel 250 yards long, after which the line descends to the valley of the Waitahuna river. It will cross the stream upon a pile bridoje in 5 spans of 25 feet each, about 12 chains further down the river than that carrying the present main road ; after which it will continue up the valley of the Waitahuna river-io the first main gully leading northwards, up which it will keep at no great, distance from the present road, until it reaches the high land forming the watershed of the Waitahuna and Tuapeka rivers, where it attains an elevation of . 576 "11 feet above the starting point, or .within 19 43 feet of the height of the .saddle at the Round Hill! The ascent to this is, however, very easy, there being only a length of 1 mile 25 chains so steep as lin 46. This part will be in open cutting, a tunnel being unnecessary. At 18 miles 40 chains, the descent towards Tuapeka commences, and is accomplished in gradients of 1 in 4^ for l^mile, and the remainder to terminus is upon gradients of lin 90, lin 55, and level. The terminus adjoins the Athenaeum reserve in the town of Lawrence, in a convenient position as regards the business part of the town, and at a part of the Tuapeka valley fovourable for the continuation of the railway further towards the interior pf the country. The total length of the

line is 21 miles 24 chains.

From the brief description I have given of the main points of the proposed railway, its general character will be perceived. *This, like all other railways proceeding from the coast towards the interior, has to surmount the general rise of the country, besides whatever ridges are encountered in its course. The water level at the terminus is 317 feet above the water level at the eommencemeni, ancl the three main drainage systems of the Tokomairiro, the Waitahuna, and the Tuapeka are traversed, causing a crossing of two mam watersheds, besides the secondary one between the Talla Burn and. the Manuka Creek. Under these circumstances, the ruling gradient of 1 in 46 may be considered extremely favourable ; but, if necessary, this could be flattened considerably, though I have deemed it prudent to avoid the expensive works which such would necessitate. The works are comparatively light, the most costly being the tunnels, which will be through schist roxjk ; but fortunately their ag^r > gate length is only about half a mile.

The sharpest curves upon the line are of 10 chains radius ; but by the adoption of less radius, — which could, be done in the detailed survey, — the earthworks might be reduced in some few cases. The limited time at disposal, owing to the late period at which the survey was commenced, precluded my entering upon this and other details so minutely as I could have wished ; but the information contained in the plans and sections is sufficient for closely approximating the probable cost of the works.

In the following estimate I have provided for the road bridges in most cases being of stone abutments, with iron girders, and the river bridges, with stone foundations would be too difficult and expensive, I would recommend being of timber throughout. For this purpose I would also reeonuYiencl native iimber, ancl especially totara ; for, judging from the durability of some bridges of that wood erected twelve or fourteen years ago in this province, I have every confidence in its durability when properly selected and treated.

In road crossings, where practicable, the line will be carried upon the level of the roads, and gates will be dispensed with. Cattle will be prevented from straying along the. line by trenches or "cowpits" dug across the railway, such as have been in use for many years upon mineral lines in Scotland, and also upon the Southland railways in this province.

I need not enter further into the proposed details of construction, as the dimensions anil general nature of the different parts will appear noted in the estimate. In forming that I have been guided in the rates for the various works by the prices which have been paid for similar works by this Department, and to a certain extent in that district, so that I have every confidence in offering it as a reliable approximation to the- probable cost.

As regards the materials for construction, I may state generally that the priiv cipal ones can be conveniently obtained, and especially ballast, which can be gathered on or alongside the line throughout the whole distance. Stone sufficient for the bridges and culverts cau be got within easy distances of the works, while the timber for bridges and sleepers can be derived from Inch Clutha, Waipori, and Tapanni.

The line passes through a good Agricultural and mining district for its full length, and would also be of great advantage to the interior Goldfields, in so far as rendering facilities for communication with Dunedin.

The land throughout six miles of its length is still Crown property, and the remainder could be obtained on very moderate terms.

It will be observed from the following estimate that the cost of the railway will be within LSOOO per mile, even including the price of land, though it will exceed it if the price of the rolling stock.be added. Bearing in mind, however, that this is to be worked in connection with the Otago Southern Trunk Railway, I have had some doubt as to the propriety of providing for even the small quantity enumerated below, seeing that probably the amount ordered for the main line will for several years be sufficient for the requirements of this also. The list I have furnished, however, may be useful in showing the maximum which can possibly be required even to meet very large demands upon the working capacities of both railways.

The following is a summary of Mr. Barr's estimate cost of line :—: — Excavations - - - £29.168 6 8 Side cuttings and tunnels - 23.681 7 8 Alteration in sirllings and roads 2,280 0 0 Bridges and culverts - - 3,473 0 0 Fencing and ditches - - 2,540 0 0 Ballast .... 5,870 14 0 Sleepers .... 5,225 5 0 Rails - - - • - 15,851 12 0 Laying rails, stations, &c, - 4.077 0 0 Contingencies -. - - 9,216 0 0 Ergineering ... 4,608 0 0 £105.991 o 4 Rolling stock— l locomotive, 2 - passenger carriages, and 6 goods waggons - - 3.200 0 0 Land, 96 acres, @£5 - - 480 0 0 £109,671 5 4 Bates per mile. Works and engineering - - £4,976 2 3 do. and rolling stock - 5,126 7 0 do. do. . and land - 5,148 17 7 Works and land - ' - - 4,998 23 0