WAINUIOMATA WATER.

New Zealand Times, Volume XXXIV, Issue 5738, 20 August 1879, Page 3

WAINUIOMATA WATER.

TO THE EDITOR OP THE NEW ZEALAND TIMES. Sir, —In reply to two letters in your issues of 15th and 18th instant, I would submit that the estimates as given were in sufficient detail for all practical purposes. They of course were those of the City Engineer. _ This scheme, though au expensive one, is simple, and does not require any Heaven-born intelligence to undeistand. The estimates, from the nature of the works, ar« not likely to exceed the sums mentioned, much loss so than those connected with the present waterworks ; and it is a safe assertion that the estimates of the present reservoirs were not greatly exceeded in final settlement of accounts, certain alterations causing certain work to appear as extras ; but these alterations also necessitated allowances being made by the contractor in adjustment of accounts, so that extras bear only a small proportion as to total cost of works. Tho present scheme is to a great extent free from danger on this head, as will be seen from the following description. The works commence with a catchment dam, the stream having hard rooky sides available for this purpose ; estimated cost, £BOOO. This sum has a liberal margin, as the one part which might exceed the engineer’s estimate. Next comes the open race of one mile in length. A very difficult matter to estimate the cost of excavating an open drain, requiring great engineering skill from this point ; digging a ditch three miles long, and laying pipes, is another vast undertaking. Then we come te the tunnel through the hill, of a given length and size ; so many yards of clay and rock to be excavated, scarcely requiring a Brunei or Stephenson to undertake it, especially as we have a tunnel from the present reservoir of about the same length—to quote as a precedent as the lawyers do ; passing from this the Hue comes down the hill to the sea beach at the mouth of the Hutt River, crossing this on a narrow bridge. The pipes pass along the Petone beach about high water mark, with nothing but sand to excavate till the Hntt road is reached ; thence following the road on the outside to Pipitea Point, Wellington. No serious possible difficulty can arise, except in the mind of one wilfully prejudiced. The cost to this point being under £IOO,OOO, the £30,000 above this amount will be ample for carrying pipes through tho city, as it must be kept in view that an expensive part of the present system—viz., the junction of the houses with the street pipes, a work coating many thousand pounds, has to be excluded in this instance, as these pipes will be connected at short intervals with new pipes, so saving the cost of new connections. This will also always keep present supply in connection with the town in case of accident to pipes from Wainuiomata. The next question is as to the cost of the land that the pipes will pass through. The first mile and a half passes through Messrs. Sinclair’s property, and, from information received, to quote the policeman, the cost of this part will be small, or nil. Beyond this point, if any objections arise from owners of property, there is a public road available for the next three miles, excepting some few chains next the tunnel. On this, side of the hill it will pass through Dr. Grace’s property, but as the damage done cannot be of a serious nature no large claim is likely to he made by this gentleman. From here to Wellington it will run through public property. The element of the cost of pipes is a simple matter. Take a standard work on hydraulics —you first find that you require a pipe of a certain thickness, to stand a given pressure ; given the diameter and length of pipe, with thickness of iron, and you have the weight. Given the length of a pipe and the number of miles you have a multiplication and division sum ; result, number of pipes required, weighing so many tons, and at so much per ton, an appropriate exercise for our grammar schools. The writer in to-day issue quotes Mr. Marchant’s statement as to cost. Now, he admitted when he made the statements that it was guess work, not having been made from any data, as shown in my former letters, from the fact that quantity of pipes required to reach Pipitea was 4000 tons less than he estimated. Next, the price he placed on them was from £2 to £2 10s. in excess of market value ; therefore his statement may be put on one side, and without the slightest disrespect to Mr. Marchant, simply because he had not made calculations based on correct data. The same writer assumes that the present water supply is sufficient for 50,000 people. Let us test it. 50.000 inhabitants —supply 50 gals, per head, as given where it can be got in sewaged cities same receiving 80 gals., as Philadelphia, require 2.500.000 per day = 913,500,000 per annum. If all the available water from present watershed was saved it would give 405,000,000, not half the necessary quantity. The normal flow of the stream in summer is about 300,000 gals, per day, say average winter and summer 450,090 gals., the remainder being flood water; to secure this waste flood water new reservoirs capable of containing 200,009,000 gals, would be necessary, at a cost of £ ——. Our present dam holding, say, 50,000,000 cost £20,000 ; 4 times 20 = 80, With the South Makara stream brought in, the supply would be about one and a half millions per day, to meet a demand of two and a half millions, so that any increase from that source would only be a temporary relief.

The volume of the flow of the Wainuiomata stream was tested by Mr. Clark when here, also rough estimate of cost. This ought to be sufficient to meet the requirement of a second engineer’s opinion. Lastly, as to quality. The water above the present reservoir is pure enough in the summer, but the natural effect of rain washes down the steep hill-sides a plentiful supply of vegetable matter—with the washing of a sheep run ; these, deposited in an almost stagnant basin, cannot possibly result otherwise than at present, in the generation of animal life, which, introduced into the human system, produces fatal results. So let every one who values his own life, and that of his family, vote to-day for a plentiful and pure water supply, with no more stagnant sheep washings from Makara or elsewhere.—l am, &c., H. F. Logan.