WATER SUPPLY

Hauraki Plains Gazette, Volume XXXV, Issue 4745, 1 September 1924, Page 2

WATER SUPPLY

— o HAURAKI west AREA. A DETAILED REPORT. The following detailed report on the proposed water supply spheme for the Hauraki West area was presented by Mr E. F. Adams, civil engineer, to a committee of the Hauraki Plains County Council on Saturday last: It will be seen that the total cost is in excess of hte rough estimate supplied some time age, but it is obvious that the layout is more comprehensive. The amount of the. loan will have to be increased by a sum equal to the first year’s interest and sinking fun<K “The proposal is to take the from the.Waitakaruru Stream at the quarry reserve on the county boundary, Hauraki Plains, Waikato “It is recommended to deal witn the headworks as follows: (a) Construct dam 17ft high: (b) provide an intake chamber in concrete, with grating, valves, etc.; (c) provide blow-off pipe from the bottom of the" dam; (d) provide a flopd-water spillway. “The dam will raise the water level seventeen feet and take the whole of the available fall out of the stream above it. The. intended high level draw-off will leave an available storage of two and a half million gallons, and the long impounding basin allow sediment to deposit before reaching the mains. This deposit can be dealt with as it accumulates by the low level blow-off pipe already referred to. "The works are designed to convey 300,000 gallons of water during 24 hours to the western boundary of the water supply area. The attached schedule shows how it is proposed to allocate the water to the various parts of the area, and also furnishesThgs, dimensions and arrangement of the mains, etc., as designed to carry out the allocation. The object of detailing these matters in this report is to ensure that your Council is thoroughlj conversant with what is being recommended, and particularly that the supply is being distributed reasonably in terms of the “So far as those requirements concerned it is evident that the distribution should be in terms of the productiveness of the land. The supply is being furnished primarily in connection with the main'industry of the county, and dairy cows are particularly being catered for. Any other uses of the water must be considered as subsidiary to this. Reference is made in this report to matters which are now obvious because main issues are apt to be lost sight of as a scheme matures ; also because the time for criticism is before the money is laid out. The scheme would have no existence but for the need of water for dairy cows. Therefore, the amount of water to meet this need is the essential features of the require-J ment. “In my estimate, which, by the way, is derived from the .opinions of thej experienced farmers, and is subject to your Committee’s expert approval, the 17,000 acres of land within this water supply area is entitled on liberaLbasis to‘an average of 60 cow" per 100 acres. In fact, considering the’ large area of peat lands and unimproved land, thip estimate is supposed to look ahead for many years to come. , . “On the basis the cows of the area would number 10,200. The average supply of water for each cow is a difficult matter to arrive at. It is, however, in terms of the milk supply and the class of feeding. “The London County Council requirement is 12 gallons per cow per z 4 hours. This provides for stall feeding during the ‘dog days,’ and represente conditions probably more severe than midsummer ones in this district. “For the 10,200 cows as above referred tp the requirement would bo 122,400 gallons. It would appear, therefore, that the 300,000 gallons arranged for will give a reasonable margin for losses, wastage, and for tho conseivative use of the water in purposes other than the direct watering of cattle. “So far as the summer value of the Waitakaruru stream is concerned, the test taken in February last showed that 381,000 gallons passed' through the gauge. The weather conditions Of the test were in every way suitable for obtaining a reliable result; tht summer was hot jind dry, and the water supply streams in other parts of the district were very low. The actual flow in the stream at the of the test would be approximately 500,000 gallons per 24 hours. It will be seen, therefore, that every reasonable precaution has been taken to ensure that the supply is sufficient to meet the requirements of the.water supply area. Particularly is this so in the matter of catering for the most important industry of the area. “The matter of the purity of the supply is one of equal importance to : its sufficiency. The bacteriological and analytical tests made at the requests of your Council have fully investigated this. These tests show that at the point of intake the water is quite suitable for the purposes re-, quired of it. If used for domestic' purposes without previously being boiled it should be subjected to treatment with chlorine. This treatment is becoming almost universal for town supply, so that the water of the Waitakaruru Stream is not. exceptional in this respect. “In considering the distribution of the supply a basis of water pressure at the mains equivalent to forty feet of head has been taken as being the most suitable for the area. This representß a pressure of a little over 171 b to the square inch. In arriving at this basis the points which have been taken into consideration nre: “1. A working pressure sufficient to supply the back paddocks of a farm, through pipes of reasonable small dimension. “2. A pressure obtainable by use of economical mains. The initial head of water at the Intake is 90ft with a full dam, falling to 85ft should the two and a millions of storage water be drawn The supply of 300,000 gallons per M

hours is, as our tests show, always available with a full head. The storage, however, is an additional precaution which may be very valuable should there be a season of extreme drought. “The difficulty in a fair distribution of water in all water supply propositions arises from the fact that those consumers receiving water under high pressure and having first draw on the mains become extravagant and wasteful. It is not possible to convey water through the mains in such a way that each of the consumers draws at the same pressure. In the design of the scheme, however, very careful consideration has been given tp effect somewhat of an equality of pressure throughout the area. As an illustration, the 300,000 gallons will reach the area , so this quantity will flow through the main under a head of 54ft. At the junction of Waitakaruru Road with Pouarua Road the flow will be under a head of 47ft. At the junction of Waitakaruru Road and Pipiroa Road the flow will be under the head of 40ft. At this point it is intended to instal a small centrifugal pump, which will take the supply to the Pipiroa area and to the area along the Pipiroa road to the southern boundary of the water supply area. The pump Will raise the head of water so that the Pipiroa township and at the Ngatea township the supply is delivered under the head of 50ft. The head of the water at the junction of Pipiroa Road with Hopai Road will be 63ft, and that at the junction of Pipiroa Road and Rawerawe. Road will he 's7ft. It will be seen, therefore, that the variations in head contemplated in the scheme are not sufficient to-place any section of the consumers under particularly advantageous conditions compared with the rest.

“The pumping plant recommended would consist of two units of electrically driven centrifugal pqmps specially designed for this class of work, pne unit to act as a stand-by, the plant to be arranged so that the quantity of water to be transferred at high pressure is delivered to the pump; the, delivery to be regulated by by-pass returning to the supply main to ensure that the supplf main . does-not suffer loss of head because of the pump’s suction. It is recommended that a stand-by oil machine engine .be provided for the use temporarily in the event of the failure of the electrical current. The consumption or power is estimated at 5 kilowatts, and the running cost for power would be less than £lOO per annum. ■ The experience here is that the cost for attendance on the electrically driven pumps in use is neglibible. In stating the running cost I am using the-rate per kilowatt furnished me by the chairman of the Thames Valley Power Board, under its flat rate. “It will be seen, therefore, that the use oijhe, pumps has the effect of equal .sing the pressure of the water in the mains. Their installation and i tinning costs will be well within a capital outlay of £3OOO ; that is to say; that for interest, and sinking fund on this amount tlie first cost of the pumps at work, together with their running cost, is fully provided for. To attain the same results by the use of large mains would entail an additional capital outlay of at least £lO,OOO.

“The matter of equality o£ pressure also determines to a great extent the position of the pumping plash, and the position recommended is without doubt the most suitable one for the purpose, and also for utilising electrical power.

“In view <rf the fact that, the present water, scheme, is the pioneer of the water schemes for other portions of your county, and that these water schemes will be in the future interconnected, it is inadvisable to lay the supply main to this water area to dimensions greater than actual requirements, For this reason the supply main had been fixed at a 9in diameter pipe. This furnished the supply at : the head given, and from this on the pipes are designed to a proportionate standard of requirement throughput. Of course, any main will furnish more water than the quantities stated in the schedule at .a less head, or, if a lesser quantity is drawn, at a greater head, both within reasonable limits.' The use of the pressure gauge on the smains will disclose whether any section is taking more water than its fair share, and the valves can be regulated accordingly. “So far as reticulation of the supply is- concerned, a pipe of lin diameter will supply a 100-apre farm. A 200-acre farm drawing by one pipe woujd receive its supply through a . I*4 in pipe under somewhat similar conditions or head, the dimensions to be modified in the distributing pipes in accordance with points oi concentrated use, long delivery, etc., which will occur in practise for each particular case. For instance, in an extreme case, with a bulk of water to be used on a farm at the point most distant from the mains, a larger supply pipe would be necessary, although the actual dimension of the connection to the main need not be increased These remarks are made to illustrate the necessity for an intelligent reticulation. It is obvious that as far as the actual connection at the main .is concerned this must be subject to (definite and effective control by your •Council. The most satisfactory way ; is tp obtain each ratepayer’s requirennents and put in the connection to meet them. •"As already stated to your Council, the present water scheme depends on a certain storage being made on the farms, etc,, to be supplied. The supply is being delivered continuously during the 24 hours, so that where the quantity is, required in, say half that time, there must be a storage .■equal to one half of the requirement. As thp farms are at the present time •provided with troughs, tanks, etc., -.this should not be a hardship, and there will be probably but few eases in which any special provision will have to be made. "It will be found absolutely necessary to insist on ball-cocks to all troughs and tanks, so that when the vessel is filled there will be, no waste. This, if carried out, will be found a

further safeguard against waste and extravagance. “Apart from the design of the works, the next item of importance is the carrying out of the scheme at the lowest price compatible with good sound lasting material. In this, competition between pipe suppliers will ensuic that the mains and the submains come to hand at a reasonable figure. The competition for the supply oi pipes, valves, blow-offs, and spocia. castings on a, job of this size will be very keen, and whilst the valves and fittings will be confined to cast-iorn, bronze, galvanised iron, etc., the mains admit a fairly wide rangd of competition. “It is obvious to me that the greatest ei couragement must be given in the tenders called for the mains. These tenders may, however, be reasonably confined to the following:

"(1) Cast-iron pipes; (2) steel pipes with protective casing ; (3) rustless steel pipes with or vftthout protective casing; (4) concrete pipes, such as those of the Hume process. “AH the above are well tried out under various condiitons of soil and laying, and under certain substantial guarantees are worthy of consideration.. In my opinion the cast-iron pipes are the only ones which, if delivered to specification, need not be coveted by the substantial guarantee of performance referred to. At the same time tlie other classes of pipes have strong advocates, and have under conditions been proved to furnish at lower cost than cast-iron a lasting and satisfying layout.

“There is the greatest scope for competition over the most expensive portion of the mains between the intake and the junction of the Waitakaruru and Pipiroa roads. Here the greater diameter of the mains as well as the fewer connections give greater scope for the steel pipe and the concrete (Hume) pipe to compete with the cast-iron. That is another factor which induced the pump position at the latter point. .

“On the accompanying plan is showr a recommended system of mains and sub-mains which would furnish a distribution to a .higher standard than that laid out for most towns. The particular feature of outstanding merit is the almost complete circulation of the water in the system. A less expensive layout would do, but the water would not be as satisfactory in use and the inevitable dead-ends would entail constant blowing off of deposit at these points. The accompanying estimates are given for the layout as drawn on the plans. . If, however, the csot is found to be beyond what your Council may consider reasonable for the nvork the scheme may be modified. “There is one important point that this report has so far hot cleared up, namely, the alternative cost of the present value in supply with or without the pumping plant. This may be expressed as follows: “From intake to Orchard Road, by mains only: 5Y 2 miles of 12in main, at £3900 a mile, £21,450 ; 3Y 2 miles of lOin main, at £3030 a mile, £10,605 ; 4 miles 15 chains of 9in main, at £2600 a mile, £10,887 10S; total, £42,942 10s. 1 “From intake to Orchard Road by mains and pumps: 7% miles of 9in main, at £2600 a mile, £18,850 ; 1% miles ofi Bin main, at £2350 a mile, £4112 1.0 s; 205 chains of 6in main, at £1640 a mile, £4202 10s; 1.30 chains of sin main, at £1420 a mile, £230? 10s ; cost of pumps and running costs capitalised, £3OOO ; balance in favour of pumps, £10,470 : total, £42,942 10s. “The estimated cost of the works as illustrated on the accompanying plans is as follows: 7 miles 23 chains jf 9in main at £2600 a mile, £18.94'7 10S ; 1 mile 62 chains of Bin main at £2350 a mile, £4171 5s ; 2 miles 45 chains of 6in main at £1640 a mile, £4202 10S ; 1 mil,e 50 chains of sin mam at £1420 a mile £2307 10s ; 4' miles of 4in -main at £ll5O a mile, £4600 ; 8 miles 48 chains of 3in main at £lO4O a mile, £8944 12 miles 71 chains below 3in at an average of £6OO a mile, £7732 10s ; headworks, fittings, and pumping plant, £3500 ;.ten per cent, contingencies. £5440 : total. £59.846.

“These estimates provide for a complete water supply, of wjiich the mains and the sub-mains would run info 38 miles in length and give the circulation already referred to. “The submains below the 3in diameter are drawn on the plan in the one colour —the broken green lines are not detailed into dimensions. Very probably the Water Supply Committee of the Council will have many requiiements which would modify the arrangement and supply value of these sub-mains. "In regard to the class of dam to be Constructed, it is desirable, before -definitely designing this, to have excavations made on the site to ascertain its character. .Unless there is a sound rock formation throughout a concrete or masonry dam cannot be considered. There is no doubt, however, that a dam! of hardwood timber can be safely constructed on the site, and for this reason the necessity for trial excavation will not arise until the Council is ready to consider the actual construction. DISTRIBUTION SCHEDULE. "Commencing with 300,000 gallons at the Waitakaruru-Maukpro Canal, 30,000 gallons is taken along the Canal Road by a 4in main : 600 acres take 10,800 gallons, 700 acres take 8400 gallons, 600 acres take 6000 gallons, 600 acres take 4800 gallons. The total of 2500 acres take 30,000 gallons. The balance of 270,000 gallons is carried along Waitakaruru Road. Of this the township area of 120 acres .takes 3000 gallons, 1680 acres take 34.000* gallons, totalling 37,000 gallons for 1800 acres and leaving a balance of 233,000 gallons at the junction of the Waitakaruru and Pouarua roads. "Here a 4in branch supples 1100 acres on the east side of Pouarua Road with 17,000 gallons, 1172 acres on the west side bf Pouarua Road with 9000 gallons, totalling 26,000 gallons for 2272 acres and leaving a balance of 207,000' gallons to carry along the Waitakaruru road. "Between Pouarua Road and Piplroa Road 33,000 gallons will be distributed to 1600 acres, leaving an available balance at the junction of

the Waitakaruru and Pipiroa roads of 174,000 gallons.

“Thence along the Waitakaruru Road towards Pipiroa by 4in -main, distributing to 1340 acres on the north side and 670 acres on the south side an amount of 42,000 gallons, leaving an available balance to carry down Pipiroa Road by 6in main of 132,000 gallons. Distribute along Pipiroa Road to 244 acres on the east side and 447 acres on the west side 14,000 gallons. “Take off by 4in main along the H<pai Road 21,000 gallons, being for 636 acres on the north side and 410 acres on the south side, leaving a balance to be carried along Pipiroa Road by 6in main of 97,000 gallpns. Between Hopai and Rawerawe roads 15,000 gallons will be distributed to 240 acres on the east side and 520 acres on the west side. At Rawerawe Road a 4in main eastward to 100 acres on the north side and 440 acres on the south side, takes off 11,000 gallons ; and westward a 3in main to 800 acres on the south side will take off 8000 gallons, leaving a balance of 63,000 gallons to be carried by sin main along the Pipiroa Road. “Distribute 24,000 gallons to 700 acres on the east side and 500 acres on the west side, leaving an available balance of 39,000 gallons at the junction of Pipiroa Road and Orchard Road. Of this amount sections 18 and 19, Block 1., Waihou Survey District, and sections 1 and 2v, Waihou Survey District, 950 acres, take 7000 gallons. For a balance of 1000 acres allow 20,000 gallons. For general purposes, etc., available 12,000 gallons.” The report and the plan accompanying it were adopted by the committed.

The next step to be taken is to get the permission of the Governor-Gen-eral in Council to deposit the report and plan at a suitable place within the county for public inspection, so that objections, if any, may be made This the committee decided to have done.

Tlie next step would be to hold a poll of ratepayers on the proposal to borrow the money.

The committee also decided to ask Mr E. Fjfcdams for hfe advice on the best method of classifying land for rating purposes and on the best method of charging, for water supplied.

As it would undoubtedly be the means of saving ratepayers a great deal of expense, the, committee considered the advisability of having tenders called for the supply of tin or smaller service pipes. It was considered by the engineer that if the council indented these pipes the ratepayers would be assured of a firstclass article, and the price would possibly be fifty per cent, less than f the pipes were purchased in New Zealand. As the completion of the re--ticulaiion would take some time, the idea suggested was to utilise some of the loan money authorised to pay fo>’ the service >pipes and to sell the pipes to those connected for cash with order. By this means that portion of tho loan money utilised would be refunded. The committee decided to communicate with each ratepayer, in the area and ask if he would take advantage of this opportunity to get guaranteed good pipes at a cheap rate, and, if so, what his probable requirements would be