ARTESIAN SUPPLY

Evening Post, Volume CXXI, Issue 134, 8 June 1936, Page 10

ARTESIAN SUPPLY

SYSTEM COMPLETED

COST UNDER £18,000

TO MEET SUMMER NV4EDS

The artesian water supply i system from Gear Island is now complete and is available to meet any position in' regard to water which the city in likely to face in the near future, sai'.d the . Mayor, Mr. T. C. A. Hislop, today. The , cost of the system, £17,857, added. Mr. Hislop, was well below the cstivr.iated cost, £20,350, and was actually h Dlow what would have been the as.nual capital charges upon a large gravity system development, so that though later it would be necessary to emjoark upon such a gravity supply, from surface waters, the cost of the Gear Island wells pumping plant, the i dditional short lengths of mains required, valves, etc., would be more \ han saved. It is not intended to oparate the artesian supply continuously, ;;aid the Mayor, for it is designed as an auxiliary system of supply, to be brought into operation when dry «-onditions result in a reduction in the stream flow in the Wainui and Ora-ng-orongo Valleys. ; . ; The wells and plant have been, installed and have been ready to run under emergency conditions for seva ral months, said Mr. Hislop, but on -account of the wet weather and the mo. even remote likelihood of any shortage of supply from Wainui and Oronjtorongo, the tests were not hurried a-ad were carried out to suit the conyetruence of the power authorities and fine waterworks department. , > WATER OF EXCELLENT QUALITY. "The water," Mr. Hislop said, "lias been regularly tested by both the Corporation and the Health Departments chemists and has been found to be''« excellent quality, colourless, and ba cterially sterile. In some respects, >lin fact the water from the wells is ot much better quality than that at.tiroes drawn from the Orongorongo and Wsliinui systems, for these are surface supplies and are therefore affected lj7 floods and at times carry vegeteg e matter in suspension from the: wau. - sheds Even so the quality of the city water is high, but surface water cannqt be of the remarkable clearness of waterr which has passed through extensive filter beds, as is so in this artesian suj}piy." j THREE MILLION GALLONS DAILE. The development of Geat Island wiIE enable an auxiliary supply of ow three million gallons per day to u<pumped into the city system. Frow; the two lines of wells across the , island the water is collected and ttovrs to the first pumping station near live wells. From here it is pumped to a balancing tank above the Hut; Roa-d. between Ngahauranga and Petone, and from the tank flows by gravity to thie second pumping station at Thorndoii, where it is placed under higher pre - sure and pumped either to the Bell Road reservoir or direct into the cit.y reticulation. By employing two pumping stations and the balancing tank high pressures in the main length o I the old 21in cast-iron main are avoided. The outer pumping station can bes automatically controlled, but thai 1 Thorndon station is manually operated An important feature of theu • system is a double valve of special ■ design, near the foot of Molesworlhl 1 Street, by which provision is made tO ( safeguard the mains and pumping l I plant against the effect of a shut-down , of electrical power. NEEDS OF THE FUTURE. "This development should have • been completed several years ago to ! meet the city requirements in years t of maximum progress," continued I Mr. Hislop, "and, having regard to the increase in population during that period and the increase which may be expected to take place in the immediate future, it is not considered that a major gravity development can be deferred for any long period—the matter is one of population growth and building activity. In the meantime, however, the artesian supply will meet the position very economically, as the total cost has been less than would be the interest and other charges on a large surface supply development for one year."