Taihape’s Water Possibilities.

Taihape Daily Times, Volume XI, Issue 3346, 26 November 1919, Page 6

Taihape’s Water Possibilities.

' EXPERT’S PRELIMINARY V ‘it ~ REPORT. Mr H..F. Toogood, engineer. of Wellington, who {vas engageld, by the Borough Council to report upon the possibilities of water supply for the ‘Borough, present and prospective, has sent in the following report, dated November 11th 1919:- - _ On the 21st. and 22nd October, I visited Taihape for ‘the purpose iof making preliminary investigation into your water sirpply, I find thaxf. you at present have a pumping scheme with a large reservoir somt 280 feet to 300 feet above the Town Hall. EXISTING INFORMATION. E It is to be regretted that the original plans of the Water supply system are _not complete, and that I had to depend on aneroid barometer readingsfor the levels given ‘ in this report. These levels cannot be considered correct within 10 to 20 feet, but they will be sufficiently accurate for the purpose of this’ investigation. THE HIGH LEVEL RESERVOIR.

This reservoir is of considerable dimensions, and when full will hold 1,312,000 gallons, with one foot of freeboard. It is questioned, however, Whether or not the structure will stand the strain when full. There are several cracks, which may have been caused by contraction of the concrete or loading stress. The ‘tank contained six feet‘ of water at. the time of my visit, and I was unable to examine the bottom. From an examination of .the. plans, I should feel just-ified in filling the reservoir to ten feet, andlthen tes’c:fol' leakage. At ten »feet the reservoir will hold 937,000 gallons, or sufficient water for 1100 people for 20 days, on the basis of a consumption of 40 gallons per head per day. To make sure of the safety of the structure when quite full, the Council should increase the filling around the outside, in order to give further back—ing to the sides. It‘ leakage is proved‘ bitumen run in any cracks and painted 1 ‘over the leaking slll'f3.ce will be efi'ective. 1

THE PUMPING PLANT. You have two pumping plants, but only one is capable of lifting water to the '.reservoir. The 037.-er is a plungertype, working directly into the mains. From the view-point of ,_supervision, both pumps are badly located. Mr Mitchell is of the opinion that the high-lift pump has only a year’s useful life left after repains are carriefd out.’ If it. is to pump the Whole of the Water required, your-Council, therefore, will have to face the question of its renewal almost. rininiediatelly. The plunger pump is :1 temporary expedient,_ and is giving 3. large amount of trouble, owing "to its location and general lay-out. It should have been located in the powerhouse, so that proper supervision could be given it. I féel'jilslified in stating that no matter iivhat. action is taken to improve the I Borough mater‘ tsupplylz {the ‘existing pumps need not be seriously considered, as they will both have to be renewed or re—arrange‘.d if pumping is continued. THE RETICULATION AND MAINS. The Council has an adequate reticulation as far as it is laid, and I can suggestbut one alteration ‘to increase its -capacity for fire purposes, namely, the two six-inch ‘mains in Main Street should be joined at their ends near the Town Hall. It would be a further improvement if inter-connecb ing pipes were made between these two pipes at Kuku and Tui Streets. Théz future extensions of the 'reticul»a.ticn will take care of the other existing dead ends and weak places in the circuits. The 2111 pipes, which are merely temporary extensions will as a matter of course be lifted and replaced with mains zideqmte for fire fighting as eir(-.umstan_ces permit. (The extension of the reticulation will be referred to later. in this repo‘rt.) AVA_ILABLE POVVER FOR PUMPING.

If your Borough had adequate Electrical power at all times, there is no quesftion that pumping by motors is the cheapest mcums of supplying high pressure water: , The large reservoir, provided that it is proved- trustworthy, would enable the pumping to be ‘done at any time to suit the other loading in the powerhouse. and if the pumps were installed in the powerhouse the shift engineer could put the punips to workwhenever the occasion offered. This systeni would be excellent from 31; viewpoints. You have forwarded me extracts from the logbook, which show me that for some hours in times ofwdrought or low flow periods, the turbines have to depend on storage,“:and, in‘faet, 'hzlve to shut !down for want of water. If these periods of low flow here of short cluration, and the resert;_Y3oi*7‘\':‘:*.s kept. as full as possible on lpj;<~:lr_j‘h; ‘stvailable occlusion, so as to make ‘Kit ’unn'e'e.“~ssa.l'_\: to pump during times ‘pf-Ilmv flew. you would be‘ able to }:tir:?:zérr§rM '_o:fl {With :I.4re-arrangeinent of the lfipiiniips; {but When" an insuificicney of

powel'-water exists for a month, or longer, and the reservoir has to‘ be refilled during such time, there will be trouble. You are now inst’.-llling an 80 K.W. suction gas set,'Which will -be of great assistance during droughts, but it will not._ pay to run this engine when water power is available. You

have now installed two sets, each 450

‘K.W. capacity, but you anticipate a peak of 110 K.W. next winter; It will not be economical to run the suction gas engine"~To cover the peak load when ample water is available, and if there is sufficient Water for eight or nine months of the year to run another 25 K.\V. hydro set, it woulfd be wise to install it. It may also be found « that eificiency in the present turbines is so low at half load that a similar turbine with much greater efliciency would be a sound investment on that account. This can only be determined by taking weir measurements in the‘ ‘tail race,‘ and comparing the water consumption with the current. generated at various loads. Care should be, taken to see that the silting up of the dam does not encroach on the stonage capacity. An additional storage capacity of 1000 cubic Yards. will give, at a level of 25 feet. sufficicnt Water for one hour for 16 11.15. Any storage capacity’ below this level will be of less value. It is, therefore, important, in view of the fact that s'toragc is depended on, to see that the top end and sides of the dam are not encroach‘ed upon_by silting. If it is found that lsuiiicient wa.‘t._e,r is available for eight to nine months to drive an additional small turbine of high efficiency so as to economise water as far as possible, I believe it will be fountd, even with the shortage of water, that pumping will be quite satisfactory now that a stand—by suction gas engine is available. All pumping plant must, however, be installed in the powerhouse, so that the fullest use can be made of all..favourable opportunities. It has been suggested tha‘t. a special turbine, or other machine, should be installed _ elsewhere on the river for the sole purpose of lifting water. This is not worth considering until all other means have proved unsuitable, as it I would mean the erections of costly head-works and machinery for the sole purpose ofpumping, while the Borough Council could do very well with the! power such machinery could ‘develop’ for electrical gcne_ration. It would be better to put all such expenditure into raising the existing dam,

EXTENSION OF RETICULATION

Irrespective of any scheme to be adopted your town now requires vapproximately 360 chains of further reticulation to cover the high levels and the portion of the flat not yet served, and includes those streets now laid with 2in pipes. From the inspection. made, and by sealing the lengths from the lithe, I believe £BOOO will be required to‘ serve all these streets, inchtding specials, valves, wand 200 house services. This estimate allows for the lzeticulejtion {to {be lezsitlended in '6-in mains, excepting ‘those streets of a total length of S 0 chains, which can easily be served with 4in mains. If the whole of the mains were Gin, the extra cost would be £320, »and if the whole were 4in the deduction would be £ll2O. The estimate is -based on using steel pipes as quoted some mon‘ths ago’; Thg ptrides used twill need to -be confirmed, and 3. complete survey ma.‘:le of the whole of the streets in question, before 3. closer estimate e.an_be given. FUTURE IMPROVEMENTS LOWV LEVEL SERVICE TANK. The existing reservoir is well placed to serve tile whole Borough. including the high levelsrbut as the greater use of water telces pl'3'ce on the low levels an economy might be effected by reducing the pumping head. To do this a Service Tank at a lower level would be necessary. This tank should hold

- 120,000 gallons, or one day's Supply , for 3,000 people, using 40 gallons per ‘_ head per day, and it-iS.“h-Ollld be placed _ about 160 feet. above the street level -, at the Town ‘Hall. With the maximum , expected domestic draw off, a mini- ; mum pressure of 60lbs. should be attainable with youl' ample recticulation If a Service ‘Tank were so placed it would be 120 feet belownthe present reservoir, and a suitable site could be !found on the Recreation Reserve ‘Hill No. 35. . ' . Assuming a consumption of 120,000 {gallons per (day, the reduction in pump- 1 ‘ing head by adopting a low level Scr-l vice Tank, and doing the whole of ‘thei pumping in twelve spurs, shouldl amount to 10 B.H.P. The Council should place Ia value on this power. taking into consideration that for a certain period of the year when the river is low, it will have to be made up by the use of the ‘Suction ‘Gas Plant. D There are, however, other advant-. 'agos in favour of a low level Service; Tank, and I propose to give an approximate estimate of the cost of it, together with -the pumps and mains required. , A low level Service-Tank calls for the following new work:—New pump a‘t. power-‘house, preferably in Iduplicate and each unit to be capable of delivering 150 gallons per minute against a head of 300 feet aproximately. I I Rising main from pump to Service , 3 Tank of about 40 chains in length{ A‘ and (Sin. in diameter. _ ' . Service Tanli 011' the Rec.rexa:tioll Reserve Hill of 120,000 gallons capacity, connected to-the present recticulation by a 9in. main. , The cost of. this new work would be approximately £4,200, with one pump, and £7OO extra if the pump is duplicated. The saving in pumping head would be over 120 feet on the present rough ‘figures, but after furtlier investigvation it may be found 'th'.a.t even a greater ‘saving may be secured. I would like to emphasise that if your Borough had ample electricall power and did not rely on storage oft water for your turbines in time of low I flow, and the high lift pump was -effi-i cient, the question of saving pump: head would not be worth considering, l as you woulid be able to do all your! puming over night without any em-5 barrassment to your peak load. l The high level Reservoir would be suppliefd from the high lift pump until it became beyond repair. When this pump renached such a state a new one would have to be installed. The duty to be done by this pump on ac— I count of supplying ‘the lim.ited high level area only would be reduced to! 9, small amount, and its life correspondingly increased. Tho Jdraw offl from the high level Reservoir would? be confined to the high level zone of consumption, occasional fire use, and to replenish the low level Service Tank, when the water in the river was dirty, or the low level pump was out of use. (To be continued.) .