CHRISTCHURCH WATER SUPPLY.

Globe, Volume XXIV, Issue 2515, 1 May 1882, Page 4

CHRISTCHURCH WATER SUPPLY.

The following report has been forwarded to us for publication by Mr D, A. McLeod, Christchurch : City Chambers, Hereford street, Christchurch, 3rd March, 1882. W. Vincent, Esq., Chairman of Waterworks committee. Sir, —I have now tho honor to submit for your consideration my scheme tor supplying Christchurch with water from the Waimakaxiri river by gravitation, and to report upon the whole question of a water supply in a general manner. The subject has already been so fully and ably investigated, that I feel congiderable delicacy in approaching it at all ; but, in doing so, however, I shall endeavor to lay my views before you as briefly as possible, compatibly with the importance of the question at issue, viz., the cast of a gravitation scheme such as will provide for present requirements, and be capable of any further future extension that might be found to be necessary. In dealing, therefore, with a supply for Christchurch, it must be taken into consideration that, at present, although tho population is only 15,000, it is reasonable to suppose that in the course of the next 1 decade it will increase to 20,000 ; and as the cost of supply will have in the first instance to be borne by the present population to a great extent, the first cost of works should be kept to the minimum, with tho proviso that the works should be capable of being extended to meet future requirements. It is not to be supposed that tho surrounding municipalities and townships will not want a water supply also. Eventually they will look to be supplied from the Christchurch mains. But in the meantime these municipalities and townships should not be taken into consideration further than in providing for possible extension of works to meet probable future requirements.

QUANTITY OT WAT EH REQUIRED YOBT)OMB8TIO, SANITARY, EIRE PREVENTION, TRADE, AND ORDINARY PURPOSES. The quantity of water consumed in this respect in different towns varies considerablyIn Europe the amount is from 20 to 50 gallons per day per head of the population. In American cities it is considerably more, ranging from 25 to 100 gallons per day. In England 30 gallons por head per day ia considered sufficient for all purposes. In America is reckoned to beamplc. The following table, however, shows the actual consumption in gallons per herd per

over 50 gallons, and in Dunedin it is well on to 100 gallons per day. It is however generally conceded 50 to 60 gallons ia a very liberal supply for all purposes, including ordinary trado and fire prevention, so that if I assume 80 gallons as a liberal standard, the works undertaken should be capable of providing this amount, not only for Christchurch city, but for extension to surrounding municipalities and townships, or for tho immediate use of a population of 15,000, with the view of gradual extension within the next ten years to meet the requirements of 60,000 inhabitants. It must not, however, bo > forgotten that there is a very large supply of artesian water of the purest quality at present readily available for domestic purposes, but in many cases necessitating more or less pumping power to get. Whilst for sanitary and fire extinction purposes considerable expense has to be incurred to comply barely with requirements. And as population increases these requirements will be more urgently needed. As it is at present, this artesian supply is used for all purposes, but now that the sewerage system ia all but complete, and in view of better sanitary arrangements being instituted, with compulsory house connections, and the water closet system adopted, a liberal water supply under pressure may be looked upon as an absolute necessity ; and us householders get used to having water under pressure in their houses, the great attendant conveniences will very soon recommend its use to them.

In the matter of fire prevention or extinction, a liberal supply of water under sufficient pressure, and available for use at all times and in all places, must be looked upon as invaluable. In Christchurch, where there are so many wooden buildings, and more particularly in the centre of the town, should a fire take place under any unfavorable circumstances such as during a N. W. gale, the consequences would inevitably be disastrous in the extreme. Christchurch has, fortunately, hitherto en> joyed an immunity from such a catastrophe that is quite, so to speak, providential, but that is no reason why a conflagration of alarming extent should net take place at any moment, and that notwithstanding the efficiency of the present admirably organised fire brigade department, whose efforts are limited to a considerable extent to the power of the engines to absorb the available supply from tanks placed at intervals over the area of the town, and the supply from which is presumedly unfit for any case of extreme urgency. In this connection the matter of insurance may be taken into consideration, and Mr Blackwell, in his report of December, 1879, mentions that the value of the consumable properly in Christchurch amounts to £6,500,000, of which only £2,000,000 is covered by insurance, the amount of premiums on which represents £25,000 per annum, and that a reduction of 12£ per cent, on this sum would amount to £3125 per annum, a reduction moderately computed, but well worthy of consideration to those whom it would affect. And as I take it it would very materially affect ovary householder in the city. Moreover, a reduction of at least £SOO a year in the maintenance and renewals of the present mechanical appliances in use for fire extinction would be effected, representing a capital sum, at 7 per cent , of £7140. BTBEBT WATEEING, .FLUSHING BIDE CHANNELS AND SWEEPING. The present system costs for street watering £6OO a year, and for flushing, sweeping and scavengering, about £ISOO a year ; and the work absolutely required is only partially done, owing to the means at disposal for the purpose being limited. With a water supply under pressure the work could be effectually done all over the town at say 50 per cent, less cost, or for a saving of £IOOO per annnm, representing a capitalised sum, at 7 per cent., of £14,285. Again, in the matter of removal of night soil, the yearly coot is £2OOO. With the drainage scheme complete and the water closet system adopted, this outlay would be saved, representing a further sum of £28,570. WATBB POB TBADH PURPOSES AND MOTIVE POWBII. There can be little doubt but that a large quantity of water under pressure would be readily used for trade purposes in hotels, stores, breweries, bakeries, tanneries, and many other places. The quantity available, and the facility afforded by pressure for utilising it, would at once recommend its adoption over any existing system to consumers, and the railway department doubtless would use the water to a large extent. What the quantity so used would be. however, can only be problematically arrived at; but to begin with and fairly estimated, I believe 70,000 to 100,000 gallons per day (or from five to seven gallons per day per head of the population) would be absorbed in this way, at the ordinary price of la per 1000 gallons, aay, for the smaller quantity of 70,000 at Is, JB3 10s per day, or for 300 days at £llsO, say £llsO for the first year, and which sum at 7 per cent, represents £16,428, Further, in respect for water that might be used for motive power or for driving water motors for running machinery, it is fair to infer that a considerable quantity would be used for this purpose. Water pressure engines now are coming into very general use in all towns where any water pressure over 501 b to the square inch is available. I would not, however, count too much on the immediate revenue that would be derived from this scarce, and for this reason, viz.— That it would not be reasonable to suppose that the (team engines and gas engines, and

other plant at present in use, Involving so much sunk capital, would be superseded by any large water motors, ior some years to come at all events, although in the event o£ any new industries being started requiring motive power, this supposition not hold good. However, for light machinery purpose?, water moters from half h.p. to 4 h.p. would bo used, and that in considerable numbers, as they come to be appreciated. Whatever revenue would, therefore, be derived from this source would, in my opinion, be limited to begin with, but would be ever increasing so long as the motive power was available. The fairest and best way to charge for water supplied in this direction would be by a fixed minimum rate per 1000 gallons used, as ascertained by metres. In this way I would cot estimate the revenue to bo derived from this source the first year at more than £SOO, capitalised at 7 per cent, £7'42 ; but the scheme I propose would give revenue up to probably £2OOO per annum; capitalised, this sum would represent £28,572. I have stated in the earlier part of this report that 60 gallons per day per head of population is a liberal estimate for all ordinary purposes. I have also shown that a largo quantity of water may be used for motive power as exigencies may require ; and considering the great probability which exists that the Christchurch water supply will be extended to the surrounding municipalities and townships at an early date, it will be readily conceived that nuc only should the mains proper of this city be largo enough to admit of carryingj water for such future extension but that the i available supply should also bo adequate. The scheme that I would propose for your consideration is as follows, and for locality and other particulars I beg to refer you to the accompanying tracing :

The scheme is practically the one known as “ White’s scheme," elaborated by Mr Blackwell and modified by mo, as being what I consider to bo the most practical scheme at a moderate first cost, and capable of any'future enlargement or extension for supplying Christchurch with water by gravitation. And although I have now the honor to bring it before rou in its present shope, the credit of originally conceiving the scheme ia due to Mr William White. SCHEME. At the Waimakariri, thirteen and a half miles or therebye from Christchurch, I propose sinking four cast iron ojlinders to tap iho artesian supply which is known to exist at that spot. To connect these ojlinders with an 18-inch diameter wrought iron pipe constructed of the best plate, coated, laid on the line shown rod on plan to Biooarton, there to construct certain suitable connection works ; from them to intersection of Colombo street and Tuam street to lay a 20 inch diameter cast iron pipe to join the general reticulation of the city. The total fall from the Waimakariri inlet cylinders to Colombo street junction is 280 feet, a little more or less, and tho length is, say thirteen and a half miles, and the minimum discharge of pipes would be 3.600,000 gallons for twenty-four hours. The total cost of works would be £85,000, including reticulation os previously estimated by other engineers, at £45,000. The estimate is made up as follows: — £ s. d. ■Four cylinders, at £3OO ... 1,200 0 0 Connections and contingencies 800 0 0 Eleven miles 18in. W.J. pipe ... 23,000 0 0 Land and works at Biccarton... 2,000 0 0 Two and a-half miles 20in. O.T. pipe ... ... ... ... 13,100 0 0 £IO,IOO 0 0 Reticulation' of city ae estimated by Mr Blackwell ... 45,000 0 0 £85,100 0 0 Engineering, supervise* >,clerical and other charges £4,200 Preliminary expenses... 1,000 Interest on £IOO.OOO tor one year, at 7 per cent. ... ... ... 7,000 Sundries and contingencies 2,700 Total ... £IOO,OOO 0 0 Total supply 3,600,000 gallons per day. An additional supply of 1,400,000 gallons per day can be got at any time for £30,000 more, and even more than that quantity for the same money, depending on the class of pipe used. As to the revenue that would be derived from the works for all purposes, from the figures I have given In this report your finance committee will bo able to form a more correct estimate of the actual results than I can. I have only to add that should you require any further information on this subject I shall be glad to give it to you. And I have the honor to be, sir, Your most obedient servant, D. W. McLeod, Civil Engineer, City Chambers, Hereford street, Christchurch, 4th March, 1881. W. Vincent, Esq., Chairman of Water Supply Committee, Christchurch. Dear Sir, —I have thought it advisable to supplement my report of yesterday’s date on the Christchurch water supply by a few explanatory remarks about some features of the scheme, which otherwise might appear to some extent anomalous. Ist. Head of pipe chosen 280 feet above Christchurch in preference to bead at height of present cylinder (360 ft). I have chosen this head of 280 feet for the reason that with eleven miles of 18in pipe, the discharge at the Biccarton junction will be practically tho same in quantity as the discharge from a similar pipe (laid from the cylinder) with 360 feet head. With this difference that the latter would entail tour miles additional piping at an additional oast of in wrought iron about £IO,OOO, and in coat iron £IB,OOO or so. And that in connection with Christchurch, any head whatever over 300 feet would not only be superfluous, but would tend to be injurious; of no value whatever, but rather on the contrary, 2nd. Beason why I propose to alter the size of piping at Biooarton, and to construct certain simple works there. The fall from the 280 feet hgad to junction is nearly twenty.three feet a mile. And the fall from the junction to Colombo street is only about seven and a-half feet a mile. And the site is eminently convenient for the construction of a suitable arrangement for regulating the pressure into town, and putting in a relieving pipe into the Avon by the cross road at tho junction. 3rd, I do not propose to use the Avon water at all in connection with supply, which will be entirely from the Waimakariri. I am, your obediently, D. W. McLeod, Civil Engineer. [The remainder of tho report will appear in a future issue.]

day: — America and Europe. Gals. Gals. Providence City.. 25 London ... ... 29 Lowell . 33 Liverpool ... ... 2 i Eoohester . 35 Edinburgh ... 33 Colombo . 43 Glasgow ... ... 50 St. Louis . 56 Lublin ... 25 Cleveland ... . 56 Paris ... 28 Philadelphia . 53 lours ... 22 Brooklyn 63 Toulouse ... ... 26 Montreal 69 Leghorn ... ... 30 Toronto ... 77 Hamburg... ... 33 Buffalo . 87 Berlin ... ... 20 Albany ... . 80 Newport... . 101) Detroit ... . 105 Chicago ... . 119: In Melbourne the consumption is rather