WATER SUPPLY

Manawatu Standard, Volume LXI, Issue 126, 29 April 1941, Page 2

WATER SUPPLY

To the Borough Council yesterday, the engineer (Mr T. K. Hay) submitted a icport un liio wator supply dealing witti various schemes whereby an improvement may result, and detailing particulars of tlio difficulties confronting the council in its selection of any of tno schemes as a solution to the problem ot providing clear water.

I In searching for some satisfactory method oi providing a clean supply, the following present themselves tor consideration, Hie report .stated: A tettliug basin, additional icsclvoiis, mechanical niters, tlic Jxi-witea Stream as u source ot tupply, an artesian supply, soak wells on or near to ttie ri\or bed. flic construction of a settling basin to hold 4 : WO,0OO gallons would pruwde a further ten days' supply (with tue rcscrvniis, a total ol 14 days' supply). Ly dividing the basin in half cacli would have, alter tilling, three days lor settlement, permitting tho heavier paiticlcs to settle but this would be insufficient to overcome discoloration. To obtain tlio same lfsciilt as by tho settling basins, two reservoirs womd be required and tho same chemical treatment would bo required to remove discolouration. Owing to tho huge quantities of silt and sand in suspension when the river is in flcod, sedimentation would be necessary before passing the water through hlteis. Except for tins silt and discolouration, the waior as disclosed by putt analysis is of satisfactory quality tor potable- and domestic use so that filtration would be required only to remove sediment and discoloration. 1 have not investigated the Kiwitca Stream as a source of supply, but understand it was investigated befoto the Oroua as a source ot supply was adopted, and was not considered satisfactory. The construction of hcadworks and pipeline to the reservoirs would be a most expensive undertaking. Artesian supply : Unless such a supply could be found near to or within piping distance of the reservoirs, it would be necessary to pump the water to a reservoir on some elevated part c{ the town to obtain the necessary pressure. While there are a number of boics m various parts of the district at various depths up lo 450 feet, no data, are available to indicate that there would be sufficient water for our purpose. This method is liable to become a very expensive experiment and there is always the possibility that the characteristics of tho water may be such that treatment is neeesscry. Soak wells: Isy this method, a well v.ould be sunk on or close to the river bod to a dopth sufficient to maintain the required flow. If the quantity could fcc obtained and maintained, this wouid be quite a satisfactory method for an auxiliary supply and would ensure clean water at all times. In ilie meantime, I am investigating this method and a well is being sunk near the intake and adjacent lo the pipeline, ff proved satisfactory, this method v.ould be tho least expensive and would save the cost of expensive works lor clarifying the water. If unsuccessful, the expenditure will bo small.

In considering the various methods, the first, for consideration are those which aim at dealing with the existing supply. This brings forward tho settling basin, reservoirs, filters and soak wells. In a letter to the council dated December 29. 1924, dealing with the water supply, Messrs Holmes and Son stated : "If the borough wants a supply of pure clear water, then it is necessary to construct settling basins as soon as funds arc available, and most likely filters when the watershed above tho intnkc is more closely settled." Settling basins would be a definite improvement and possibly lead to a cure of the present trouble, permitting settlement and enabling discoloured wator to be treated before entering the reservoirs. The question of reservoirs versus settling basins must, t think, go in favour of tho settling basin. Bringing tons of silt five miles to settle in tho reservoir is not to be commended.

With tlio tilt question satisfactorily dealt with, the report ndded, and with the coinplot ion of the scheme partially carried out in 1926, the town could bo assured of an efficient and satisfactory supply for many years to come. The. maximum consumption in the summer is equal to. and on occasions exceeds, tlio flow in amounting to 600.0C0 gnlions per day. With the completion of the scheme, the supply will bo increased to approximately 800.000 gallons per day. Approximate costs are: (1) 141 chains of new main from the reservoir on the now line. £6000: (2) oSi chains of 9in pipe between J2in sections, replace with 12in pipes, £2500: (3) settling basin, divided into two basins, each holding 2.000.CC0 gallons. £9000: (4) surveying onsomenfs. etc.. £250: (5) reservoir to hold 2.000.000 gallons. £8500: (6) soak well. including pump and engine, £BSO.