ARTESIAN WATER

Dominion, Volume 29, Issue 216, 9 June 1936, Page 2

ARTESIAN WATER

Wellington’s Auxiliary

Supply

SATISFACTORY TRIAL

Alternative to Costlier Akatarawa Scheme

The new electric pumping units (five in number) installed by the Wellington City Council to force water from the 21 80-feet. artesian wells at Gear Island,. Lower Hutt, into the city mains have been run at intervals during the past, two months. On Thursday last there was a four-hour trial with the Wainui water ent off entirely and artesian water taking its place. It was then seen that all was as it should be with the plant and that Wellington now has a most valuable and dependable alternative source of water supply.

How Wellington came to resort to artesian supplies is now history. Fifteen years ago it was decided that the city must have a supply supplementary to that from Wainui and Orongorongo. As both these mountain streams were apt to dry up at the same time it was considered that further storage was necessary, and an attempt was made to find foundations for a big dam below the two already in existence at Wainui. Failing to find a firm bottom for such a dam, it was decided by the authorities that a new source of supply must be sought. This was found at Akatarawa and Pukeratahi, and a report on a comprehensive scheme for the whole of the Hutt Valley and Wellington city was prepared by Jlr. E. R. McKillop, water and drainage engineer # to the City Council. This report was presented to the then newly-formed Wellington and Suburban Water Board, but as soon as it was disclosed what this scheme was to cost suburban bodies, the Lower Hutt and Petone Borough Councils withdrew from the board, declaring they could get all the water they required very much cheaper by tapping their artesian supplies. They were right. That decision, however, caused the abandonment, for the time being at all events, of the big gravity water scheme, as Wellington alone could not bear the whole burden of such a big scheme. Still, Wellington had to have its auxiliary supply, 8-rtd found on inquiry that it could not do better than emulate the example of the Lower Hutt and Petone Borough Councils and secure a reinforcement of water from the artesian supplies of Eastern Hutt. They owned an acre' of land at the southern end of Gear Island (near the pipe bridge), and there some 21 wells were sunk and pumps were imported to force the water into the Wainui mains which pass the location of the wells after leaving the western end of the pipe bridge. This work was commenced last year, and the plant was ready for any emergency a month ago. _ Mayoral Statement. In a statement made yesterday, the Mavor of Wellington, Mr. T. C. A. Hislop,’ said that the tests, which concluded last week, had been in every way satisfactory and the results corresponded closely with the assumptions under which the plant was designed. “The estimated cost of the work was £20.350,” said Mr. Hislop, “and the expenditure to date, with one or two minor items still to come, is £17,851, which is less than the interest, on a gravity development for one year. , “Provision has been made at Gear Island for the installation of a standby unit (a fifth) later when this becomes necessary. The well system extends across the lower end of GearIsland in two rows, the water being delivered to an automatically operated pumping station from which it is pumped through an existing.2lin. castiron main into a balancing tank along the Hutt Road. From this tank it gravitates to a main pumping station at Thorndon, whence it can be boosted either into reticulation or into the Bell Road reservoir. This form of development ensures that excessive pressures are kept off the old 21-incli castiron main, the protection of which has given the engineers sonic concern. The main is further protected by special reflux and pressure relief valves in the event of the-pressure rising above a certain pre-determined safe value.” The city engineer (Mr. K. 14. Luke) stated that all hough the present, development. of the artesian supply had quickly aud very economically filled the present deficit In the city’s water supply, a major gravity development would probably have to be considered within the next few years. The artesian development just completed should have been in operation several years ago to cover the water supply deficiency in a season of maximum dryness. When allowance was made for the increase in population which had taken place, and for the increase expected to take plnee in the immediate future, it would seem that a -major development should soon be considered, as even after the form of this development was settled, four or five years would probably elapse before such a supply could be made available to the city. The matter was one of population growth, and (he anticipated increase in building activity must be kept in mind. An Amazing Supply. The present development supplies over three million gallons of water per day. The quality of Hie water has been regularly tested both b.v the corporation's own chemist ami by the Health Department. It has been found to be of unusually gqod quality, colourless. and bacterially sterile. One of the most interesting sights’ at Gear Island, visited yesterday by a "Dominion" reporter, is to see Hie actual body of waler these wells produce naturally at ground level. That is imide possible by the provision of a measuring concrete tank let. in the earth, about 22 feet in length, 4 feet in

breadth, and some 4 feet 6 inches in denth. At ono end is the mouth of an IS-incb concrete pipe connected with the well system. Each well, or series of wells, has a valve, and as these were opened up the water began to pour out of the pipe-mouth into tiie tank. Gradually as the wives were opened the stream grew bigger and swifter, until it ran full bore, as though under considerable pressure. Near the opposite end of the tank is a steel weir, and it is b.v taking the depth of the overflow that the flow is measured. Beyond the weir is a great drain pipe, which conveys the flor to the river. The Dell Road Basin. When Wainui tails it is this supply that would be pumped into the mains, passing through the balancing-tank one mile south of Petone on the hillside (Hutt Roa;l). From there it will flow through the pumping station on Thorndon Quay. where two electrically-driv-en pumps larger than those at Ixiwer Hutt will give the water a further impetus. driving it through the city and up to (be Bell Road reservoir, <>■ the Brooklyn Road. That reservoir, in a key position almost in the centre of the eity, has a capacity of 2.600.000 gallons, and acts as a distributing basin. The level of the water at Bell Road is recorded at the Thorndon pumping station, and there are automatic devices for cutting the water off when it is no longer needed, and turning it on when there is a deficiency. At Thorndoii. too, there is a telephone with which to communicate with other stations and officers. Owing to the hum of the motors the telephone has had to be provided with a box (a small room), lined with Inch-thick sound-proof material. Such is the smoothness and efficiency of the new plant that probably no one will bo the wiser when the Wainui .supply is cut off and artesian water fills the cit-v mains.