TOWN WATER SUPPLY

Southland Times, Issue 16786, 14 July 1911, Page 3

TOWN WATER SUPPLY

THE DUESDAIiE SCHEME. Mr clapcott’s estimate. The Town Engineer (Air G. E. Clap-, cotl) . submitted to the Town Council last night the following detailed report on the Dtinsdale Water Supply scheme. Air Clapcott said : Since submitting my last report on a supply from this source, I have gone verv carefully into the Question of cost, and also the'class of water main most .suitable for the purpose, combined with economy and durability. Riparian Rights. Regarding the matter of riparian rights, I have no hesitation in stating, that without providing storage at the intake, farmers holding land adjoining the stream lower down wilt have more than ample water for all stock and farm purposes for many years to come. If storage is provided at the intake, there will be practically no appreciable difference in the present flow of water. Proposed Route for Water Main, From Gladstone going north, the main will follow the North Road to the terminus near the Makarewa River, from here it crosses the Makarewa some fifty chains above the bridge, and continues through farm land to Grove Bush. The proposed line (70 chains) through the bush passes through Crown Reserve, and this will be the most expensive portion of the main to lay. But as most of the bush is light and the ground free from swamps, the only difficulties are clearing the line and trenching : ample provision Is made in the estimate for this work. To avoid the bush would necessitate following a line which would increase the total distance by a mile ; an extra to be avoided if possible. After leaving the bush, the line, with the exception of a mile of road, passes through tussock and agricultural land, principally to its intersection with the main Invercargill - Hedgehope Road. Traversing tins road for thirty chains, the line again continues through private land as far as the Dunsdale road, at the junction of the bush tram line ; from here on to the intake the main will follow the public road and bank of stream. I have inspected the whole route as described, and the country passed through is all flat, and easily trenched with the one exception mentioned. There should be no difficulty in having material carted along any portion of the line from the different service roads intersecting. Two short inexpensive pipe bridges will be required over the Makarewa. In regard to that portion of the line that passed through private property, I would suggest that arrangements be made with the various owners to reserve a narrow strip of land along the pipe line, which will not be cultivated, and will provide free access for inspection purposes, without interfering with growing crops. I have written to most of the owners through whose land the main will be laid, but replies have not yet come to hand. Several I interviewed, and they had no objections to offer, providing that compensation was paid in the event of damage to crops, etc. These are matters that would be embodied in the necessary agreement between the various owners and the Corporation. Head Works. Levels have been taken as far as the waterfall, the level here being 308 feet, and the distance from the reservoir site 52 chains. Allowing for extra length of main, the cost of providing an intake here would be less than the site lower down, providing an equal head of water. But with the limited field information obtained respecting this site, I am not prepared to recommend an intake here, in preference to constructing a dam at the site as originally proposed, which will Impound a large area of water, and this will permit of suspended matter settling before reaching the outlet pipe in the time of flood, and provision, if found necessary, can also be readily made here for filtering the water, but it is .very improbable that this will require to'be done, with such an extensive settling basin provided. Estimates. The total length of the main Is 24 miles, and as this is the principal item of cost in connection with the scheme, T submit estimates for various classes of pipe having an internal diameter of eighteen inches. Included in the estimates are cost of head works, and all other charges in connection with the installation ; Cast Iron Pipes .. £96,000 Lapwelded Steel, .. £74,000 Wood .. .. £72,000 Spiral Steel .. .. £64,000 The pipe I recommend to be adopted is a Spiral Steel main from the intake to within eight miles of town, and from here lapwelded steel main. Possibly coneerete pipes could he used for the first two or three miles down, where the uresstire te moderate, but until I have had an opportunity of testing this class of pipe under hydraulic pressure, I cannot advise, but if proved satisfactory there would be a saving approximately of £2500 on the undermentioned estimate. In recommending the lapwelded pipe for the lower portion of the main, I prefer this pipe for the reason that it is a heavier type than spiral, and in my opinion the joint is preferable for this oortion of the main. In regard to the life of steel pipes, this depends almost entirely on the protective coating. Provided every care is taken in laying the main, and any damage to protective material made good before the pipe is covered, the life of these pipes should be equal to cast Iron. In Victoria many miles of steel pipe have been used in connection with the Melbourne water supply, varying in size from 54-inch diameter, down. Some of these pipes were laid twenty-six years ago, and are still quite satisfactory. Owing to their great weight, and transit charges, cast iron mains are prohibitive in such a scheme as this. Regarding wood pipes, these have only been used extensively in some of the American towns, and possibly the cost there is considerably less than for steel or iron, and warrants their adoption on this score. Retailed Estimate. The following is a detailed estimate for the scheme as recommended : 24 miles XS-lnch main . . £47,900 Head Works .. . . 4,500 Trenching, including 70 chains through bush .. 2,800 Laying and jointing .. 1,570 Railage and Cartage .. 1,130 Valves and specials .. 500 Surveys and Lands .. 300 Road and Telephone .. 200 Standby Pump at Water Tower, motor driven, and repairs to large reservoir 700 Caretaker’s House .. .. 400 £60,000 10 per cent, contingencies on £12,000 1,200 5 per cent, on £47,900, cost of pipes .. .. .. 2,490 £63,690 Hirst year’s interest out of X-ioan, at’ 4 per cent. . . 2,540 £66,230 Say : £66,000. Annual Expenditure. Interest on £66,000, at 4 per cent. . . . . . . £2,640 Sinking Fund, £66,000, at 1 per cent. . . . . . . 660 Labour 250 Rent AVater Reserve .. 50 Maintenance Buildings and I’ump.s . . . . . . 40 Insurance and Office expenses .. .. . . CO £3,700 My estimates are based on quotations received from contractors for cartage of material, also for trucking, and a substantial amount provided In excess of quotations given. In regard to the price of pipes, close estimates have been submitted by manufacturers for these, and allowances have been made bore also ; so that I feel fairly confident in saying that the cost of the work completed should not exceed the estimate.