THE TIMARU WAXES SUPPLY.

Lyttelton Times, Volume LVI, Issue 6488, 13 December 1881, Page 5

THE TIMARU WAXES SUPPLY.

The formal opening of the works for sap* plying Timara with water will take place on Friday next, and in view of that event, a brief sketch of the work in question may not be uninteresting to our readers. It may be premised that the scheme is of such an ex* tensive character, that no attempt can be made, within ordinary limits, to give anything more than a general idea of the whole; detailed description is out of the question. The water is brought through hilly and undulating country from the river Fareora, about 17 miles to the south-west of Timara. At this spot die river rushes through a gorge, overhung by lofty precipices of a kind of slate. The lower end of this gorge has been dosed with e concrete dam, in die form of an obtuse angle, about 130 ft in length, and rising to a height of 12ft above the original water-level of the river, so as to make the basin or reservoir from which the supply is derived. This dam, which lies north-east and south-west, is an enlargement of the one which was constructed for a similar purpose some few years ago, and which was rendered useless by the rush of the river, having been both undermined and outflanked by the water. This old dam was lengthened 21ft at the end which the water came round, and the portion undermined was filled in with concrete in such a manner as to completely remove the danger of its being undermined a second time. In order to prevent the foundations being worn away by the water rushing over the face of the dam, a wall of masonry on a concrete foundation has been built across the stream about 100yds lower down. This wall is 163 ft long, and rises some Oft above the old water level. By this means a large pond is formed, which acts as a *' water-cushion, and prevents the torrent pouring over the main dam from scouring away the bed of the stream underneath.

Two great difficulties were found to exist in the way of conducting the water into the race. One was the choking up of the channel by tho crumbling of the slate rooks of the gorge, and tho other was the silting up of tho outlet bv the shingle brought down by the ttroam. Both these difficulties have been overcome by ii plan at once simple and effective. -The central portion of the dam, for a width ol 44ft. is constructed one foot lower than the remainder. The top of this lower portion is covered with bluestone masonry for a width of three feet. This stonework is two feet thick, and is rounded towards the face of the dam, with a curve carefully calculated to allow the water to flow over in an unbroken sheet, without even a ripple Besting on the conorete at the back of the stonework is a perforated pipe of cast iron, closed at one end and secured by iron brackets. The perforations are, of course, small enough to exclude the shingle. This pipe communicates with a concrete culvert, 85ft long, constructed m the dam. and which conducts the water past the place whore the cliffs are crumbling. The top of this culvert is well pitched with large stones. The water is then received in an open race, by which it is conducted towards Timaru. In some places the channel is contoured to. a grade of from three to five feet in a mile, and is merely an open water course on the hill sides. In other places the water is carried through spurs by moans of small tunnels, provided with stone fronts and concrete inverts. Whore tho ground will not allow of open races, the stream flows through 18-inch stoneware pipes. Three of the valleys on the course are crossed by moans of cast-iron syphons, with concrete inlets and outlets, and with air vessels in thecentreof each valley. The syphon pipes are carried across the bottom of the valleys in stone weirs, which have apertures to allow of the passage of what litt e water flows down them in summer. These weirs do nob extend from bank to bank, so that in case of flood they would notaotasa dam, and be in danger of being swept away. Tho water would merely flowaroundand o them Fifteen other valleys are, as it were, hridgsdby wrought-irou flumes supportedon timber trestles. In some places conorot» piers are substituted for trestles, and tb latter are firmly fixed in concrete foundations.

The whole of the flumes rest on concrete beds, carried on timber work, and provided with water tight india-rubber joints. After being brought through hills and valleys in the several manners above do* scribed, the water is received in the large service reservoir, which is of an oblong shape, and is situated about two miles from Timara. It is conducted from this reservoir in an 18in pipe, with a flap valve at the entrance, through a tunnel 196 ft Gin long to the valve well, from which it flows along a concrete culvert about 220yds in length to the pipe head, in which it passes through three strainers of very fine wire gauze into the main leading to the town. Arrangements are made for drawing for this main from either the service reservoir, or direct from the race at pleasure. Some little distance above where the race empties itself into the reservoir, a channel taps it, and leads around the reservoir to the pipe head. Sluice gates of simple construction are provided, by means of which the water can be conducted along this channel when required. From the pipe head the water goes to the town in a cast iron 14in main, which crosses the Otipua creek with a syphon, embedded in a stone weir, and provided with a large relieving valve, to relieve the main of the pressure which might occur from the sadden shutting of any of the valves. The water enters limaru at the end of North street, and is distributed through the streets by mains varying from 14in to.3in in diameter, according to tho pressure of the water in the different localities, and also toe quantity of water required to be supplied. There are altogether nearly 13 miles of mains. One, lOin in diameter, is conducted right through the town to tho railway station. The connections with the houses are made by means of galvanised iron pipes, which are laid by the Corporation as far as the building line. Each connecting pipe is furnished with a small stop cock and service box fixed in the pavement. Fire plugs are put in at intervals of five chains along tho whole of the mains. It is anticipated that the normal pressure in the lower parts of tho town will be 801bs to the square inch. All the work in connection with the system has been done in very good style, and, on the whole, for several hundreds pounds less than the Engineer’s estimate. The Corporation have still a balance of the waterworks loan in hand amounting to over £IO,OOO, which it is proposed to expend in extending tte system to the suburbs, as soon as tho question of levying water rates on the residents therein shall have been settled. The Engineers for the present scheme are Messrs Dobson and Son, of Chridcburch. When these gentlemen took np the work, after the failure of a previous scheme, there was a considerable quantity of material in hand, and the completion of a successful system was estimated to cost about £30,000. As was said before, this limit has not been reached. It may be mentioned that the ad* ditional cast iron pipes required were imported from Glasgow. The additional valvea were supplied by Messrs Burt, of Dunedin; the Irregular castings, such as curves and connections, by Messrs B. Sparrow and Co., of Dunedin. The galvanized iron service Kfor connecting with the houses, and the work, were made by Messrs Anderson and Morrison, Dunedin, and the stoneware pipes by Messrs Ford and Ogdon, and Austin and Fork, of Christchurch.