LANSDOWNE WATER SUPPLY

Wairarapa Age, Volume XXV, Issue 10713, 9 April 1913, Page 6

LANSDOWNE WATER SUPPLY

REPORT BY JVIIR G. LAINGMEASOiV. The Following report on the Lansdowjio water srupply has been received by tin Mnsterton County Council :rom Mr (i. Laing-Meason : j "1 regret that I have been unable to furnish my report sooner, but I havp been delayed in procuring prices and other information which were necossary. 1 "Concrete Pipes.—The nine-inch, concrete pipes which. conveyed the ■tear water supply to the dams were Said a few feet from, and approximately parallel to, the edge of Mauns?H's , iake. Outside the pipe line, and along the edg.» of the water, willow trees '.lad heen planted. Notwithstanding that the roots of these trees wer? , actually in the water of the lake, they J have apparently sought the running water in the pipes; and they have projected their roots away from the lake wntor. and penetrated into the pipes, which are now more or less ( choked wih masses of roots for a length of some 27 chains up stream from th l dam. The pipes were not uncovered at the time of visit, and ( I could not. therefore, examine them dose!v. But as I saw at some of the aerators that the roots had parsed right through six inches of solid concrete, it is probable that they . ha vc penetrated the pipes (which are , only about 1.1 inches, .thick) at very many points, and that probably the whole line is completely blocked up. I f this is; so, it would'be practically im*possible to clear out the pipes, and it would certainly be imwise toijebntinue their use where tliey are nsar willows. Up stream of this, 27 chains i I think, it will be found, on uncovering them, that the pipes are generally clear and efficient. ' Concrete Half-pipes.—l have given careful consideration to the suggestion that concrete half-pipes, forming' an open channel, should be used instead of whole pipes. Except from the point of view of cheapness in initial cost, this* proposal does not recommend itself to me. The objections to it are: The half-pipes must necessarily be laid on an accurate gradient from end to end. following the contour of ground exactly. Such a graded line would be much longer and more expensive to cut. Leaves and other rubbish would be blown or fall into the channel, entailing constant attention and cleaning out. A winding open channel would out up the ground and make severances, to which the landowners could reasonably object. The line would have to be fenced and wire netted on both sides to protect it from stock, dogs, etc., and, I be» lieve, the roots of willow and other trees would disturb and damage it in J have computed the discharge due to the available fall for half-pipes and I find that the diameter must be 18 inches to be equal to the existing 9-inch pipe. ' "Preliminary Work.—As a preliminary to definite action in regard to the pipes, it is necessary to examine and test the efficiency of the pipes for about 45 chains down stream from town intake. They should be uncovered where they are near any willow trees to ascertain if roots have entered them. They should also be tincovered at 3 or 4 places, and tested under a full head of water to see if they run full bore. "Suggestion in Respect of Pipes.— After the foregoing preliminary work has been done it will be known exactly what condition the line is in. Any inefficient or choked pipes would be removed and replaced if necessary by metal pipes. In regard to the balance 1 ., of the line to the dam, "which, as I have said, is about 27 chains, I do not think it would be worth the expense of taking them out. If the Department insists on carrying the water in pipes a l ] the way to the rams, then without doubt metal pipes must be used, and these could be laid over the concrete pipes and at just sufficient depth to cover them. For my part I am satisfied that it is not necessary to pipe all the way, and that practically as good results would be obtained, by turning the water into the lake at the end of the 45 chains, and drawing off at the lower end, as at present. At anyrate, before going to expense of laying metal pipes, my suggestion might be given a trial. Specimens of the water could be taken, periodically, from the dam, and from the service i reservoir and analysed. If the an- | alysis proved the water to be good no alteration need be made, and the cost to the ratepayers would be practically nil. If, on the other hand, the water was show to be bad, then imLprovement must b? effected. In tin; latter case, Jt would be much more satisfactory to resort to filtration (as I suggested when I designed the works) than to merely carry the water in pipes to the rams. If it is fourtd necessary to filter the water I would" advise the installation of what is known as mechanical filters, which have now almost entirely superseded the old sand filters. They cost less and give a higher degree of purifica-1 tion both in respect to the cliinination of ordinary impurities and micro- j organism. The cost of such an installation is shown in my estimates hereunder. "Health Officer's Memorandum.— I ha.ve read and carefully considered this report. The whole of the conditions mentioned in it were known to the Department before the works were undertaken. Dr Frengley, the D'strict Health Officer, accompanied by some of the settlers and myself, visited and examined every part of the race and works from the Ruamahanga

intake to the town. laid down certain requir. ments in respect of the scheme, and all of these were given effect to in every particular. Your Council will remember that I proposed to draw the supply direct from the dam and pass the water through filters. The Department objected, .to filters, and insisted that the water should be carried round the edge or the lake in pipes, a distance of about 72 chains, and delivered without filtration to the rams ; the theory being that if this were done and if the race was fenced for a certain" disi tance above the pipes, the water would purify itself in that distance. It- is now suggested that the pipes may be discarded, the water being delivered directly into the head of , the. lake from the race; ard a numb.r cf Works are required to prevent any possible pollution of the race the whole way from the river' intake to the lake. | "I desire to point out that there is no more pollution to-day than there f was when the Department gave its approval and consent to the scheme; and if the water was tit .for eonsump- ' tion theni under the conditions im- ' posed by the Department, it is fit ' now under the same conditions. To re-establish these conditions in their entirety, the piping round the dam ! must reinstated. "As I have already stated,' I jim confident that- n:o better results will be obtained by merely carrying the j water round the lake in pipes. In- ' deed, I believe that a purer water will be gained bv drawing off from the surface of the lake at the dam end, for the reason that, . a.s the mass Water in the lake moves-' s]twly in that direction, a very large proportion of the impurities, including bacteria, are precipitated to the bottom. It seems to me that before any expensive work is underaken, itf is absolutely necessary to submit the water to analysis at the various?points I have indicated; and I canno£ advise your Council to enter upon any worn (other than the preliminaries I have referred to) until this is done. "Feed Pipes to Hydraulic Races. — I was very much astonished to find, on inspection, that apparent deterioration had set in near the top ends of two out of three of these pipes, which had been more or less holed for some ten or twelve ifeet just below the feed tank. It is much to be regretted that this was not reported to me Sooner, >so that the matter might have been considered sooner. The pipes in • question are of mild ateel, coated in the usual way, and were supplied by the makers of the jams. I have con-» suited with the local agents who supplied the pipes and ramg; and they express themselves" as unable to account for the failure. At my instigation, they have written to the makers asking for an explanation, and for remedial suggestions. As soon as the , reply reaches me, I will communicate with and advise you further. "Summary.—l. The concrete, pipes for 4,0 chains from iuta-ke should be uncovered as indicated, and tested to ascertain if they are sound and free from blockage. 2. That the water should be immediately' analysed, chemically and baeteriologically at (a) where it leaves the end of first 45 chains of concrete pipes; (b) neaT the dam, and (c) at service reservoir. 3. That no work should he undertaken until exact information regarding the water is obtained. I need scarcely add that no time - should be jlost in obtaining the analysis. If you 'desire it, I will, on receipt of a wire, see the Health Officer and explain the position to him,, and ask him to ' get samples taken without delay, j ''Estimates of. Costs.-MJncovering ! and examining 45 chains of; concrete] . pipes, 4 £2O; steel pipes, delivered at | Masterton Railway Station, 27 chains 'at £l6 l«s, £445 'lOs; carting, laying ' and. jointing 27 chains, at £1 10s, I £4O 10s ; contingencies, £10; total, 5 £496. Concrete half-pipes, 18-inch half-pipes, each 6ft long, No. 330, at 19s 9d, £178; excavaiing and grading trench, laving and jointing half-pipes, 30 chains'at 30s, £45; fencing, wire 'netting 60 chains at £ljv£6o; contingencies, £10; total, £293. Filters, I I pair No. 6 Bell ißros.' filters; cap- ! ablet of purifying 150,000 gallons ' daily, installed complete £970. ; "I. n! regard to the half pipes it will be seen that I have allowed for laying only from the end of the first 45 chains from the intake to; the dam. The length of the present pipe line is about 27 chains, but < the more sinuous line, which, the open channel would make, would probably amount to another 3 chains, making, say, 30 chains in all."