NEW PIPELINE FOR GISBORNE WILL COST £211,320 –

Gisborne Herald, Volume LXXV, Issue 22665, 16 June 1948, Page 4

NEW PIPELINE FOR GISBORNE WILL COST £211,320 -

BOROUGH ENGINEER’S REPORT

REPLACEMENT of the existing pipeline between Waingake and Gisborne, with pipes of a diameter of 20 inches and capable of delivering a supply of 2,350,000 gallons per day, will cost £211,320, according to a preliminary report submitted by the borough engineer, Mr. G. M. Beaumont, at last night’s meeting of the Gisborne Borough Council.

The plans under consideration will provide for the needs of an estimated population of 23,500, which the borough should reach about 1965 or 1970, according to the present rate of population increase. Mr. Beaumont’s report excluded reference to certain aspects of reticulation and distribution, which the engineer pointed out would be dealt with in another report. The present report was to be treated as an interim one only, but the reference to the main service reservoir had been included as it was a matter of some urgency affecting to some extent the route of the new pipeline.

Mr. Beaumont’s comments continued: —

SERVICE RESERVOIR

46HpIHS is dealt with first, as a I decision on this may effect, the pipeline route. With a new pipeline, the position would be that ample water would be available in storage at Mangapoike, at a point about 26 miles from the borough. "To reduce any danger of serious interruption to the supply of flood washouts and earthquakes, which danger would be present even with a new pipeline, modern practice is to have available in service reservoirs at least three days’ supply, at a point as close as possible to the reticulation. "When proposals now under construction or already authorised are complete, the amount of w ' ate f non able close to Gisborne will be 1,260,00 U gallons, of which 860,000 gallons will be in the Taumata reservoir, and 400,000 gallons beside the proposed booster pump. This amount is about 11 days summer supply at the present demand, and probably will be less than one day’s supply when the reticulation of the whole borough is complete. It is therefore advisable to provide further storage at some point near Gisborne. "Subject to detailed investigation, and provided proper precautions are taken during construction, it is believed that extensions to the Taumata reservoir will be quite safe. “It is proposed, therefore, to allow for the construction of extensions to this reservoir, with an increase in storage of approximately 5,000,000 gai“lf this proposal is approved, the most suitable route for the supply pipeline would leave the existing route at the saleyards corner at Matawhero, and proceed from there by the most direct route to the Taumata reservoir. “It should be noted that, if this route were adopted, the water supply to Makaraka would cease, unless a special pipe were laid to there, as the township would no longer be on the pipeline route. The extra cost of siting the route so that it would continue to pass through Makaraka would be about £2400. In order to fit in more conveniently with the final scheme, the shifting of the site of the _ proposed booster pump would be advisable. “The new site would be near the intersection of Lytton road and Ormond road. The operation of this new site of the booster pump, pending the completion of the proposals, would not be adversely affected.

PIPE LINE

present pipeline from I To Arai is in two main sections. The first section, from the intake to the Waingake settling tank, is approximately 31 miles long; and, of this length, about two miles is laid with 9in. diameter steel pipe and about 11 miles with 15in. diameter steel pipe. The larger section, from Waingake to the intersection of Lytton road and Gladstone road, is laid with 15in. diameter steel pipe. “This pipeline is too small to deliver a sufficient supply to Gisborne at a reasonable pressure, with the result that often the higher and outer areas of the borough have little or no water. “Proposals are in hand for the installation of a booster pump to increase the amount of water available, but this is looked on purely as a temporary emergency measure. . “Apart altogether from the insufficient capacity of the existing line, it is in a very bad state of preservation. The line was laid about 1907, and is, therefore, over 40 years old. Leaks, many of them serious ones, are continually occurring, and can be expected to increase in frequency as time goes on. During the past two years 105 leaks have been repaired, and 240 ft. of new pipe laid, as well as one deviation of about a quarter of a mile which was brought into service. “Certain portions of the line give more trouble than others, but generally the whole line is in poor condition, though it can be patched up for a short period. It will thus be seen _ that, even were the line of ample size to supply the demand, its replacement would still be a matter of urgency on account of its condition. In this connection, it should be noted that the phrase ‘duplication of the pipeline may be a misleading one, as the line is in no fit condition to carry even a portion of the demand without continual maintenance attention.

PIPELINE CAPACITY

aT , nE water consumption for I the past two years has * been 355,000,000 gallons per annum, or an average of 1,040,000 gallons per day. The heaviest weekly demand in the past summer was at the rate of 1,210,000 gallons per day in November. This figure was reached when the pressure was some 201 b below normal, owing to the lower Waingake intake being in use. "Had the pressure been normal, and no restrictions on hosing except that hoses be held in the hand or attended, it Is probable that the consumption would reach 1,300,000 gallons per day. This is equivalent to about 100 gallons per person per day, which is a figure somewhat above the average for New Zealand.

“In estimating the future demand, this figure has been used. When the outer areas of the borough are reticulated, the consumption is expected to reach a summer figure of up to 1,000.000 gallons per day; and, for a population of 20,000. to reach 2,000,000 gallons per day.

“An 18-inch diameter pipeline is capable of delivering into the Taumata reservoir about 1,800.000 gallons per day, while a 20in. line can deliver 2,350,000 gallons per day. “Estimates of population increase are difficult to make with any accuracy, but, if the same rate of increase as over the past 40 years be maintained. Gisborne can expect a population of 23.500 about the year 1965 or 1970. “A 20in. pipeline, at 100 gallons per head per day, could sunpfv a population of 23.500. By installing booster pumps at a later date. If required the capacity could be increased to supply 40,000 or more.

“An alternative to the installation of booster bumps to increase the supply when the population passes 23,500 would be the adoption of universal metering. This, by encouraging thrift

in the use of water, usually results in a marked reduction in the consumption per head of population. "It is considered that it would bo more economical to instal a 20in. pipeline. of which the capacity may be increased at a later date by booster pumps, than to instal a larger pipe line at once- Accordingly, provision has been made for a pipe-line of this much steeper grade, and consequently a smaller pipeline can carry the required flow. On this section, a 12in. pipe is capable of carrying as much as a 20inch on the Waingake-Taumata section, and provision has been made for a line of this size. Provision has also been made for connecting the Mangapoike pipeline to this line at a point about 30 chains from the intake. “The proposed 20in. pipeline route will cross Ormond road at Hansen road. In order to allow of the by-pass-ing of the Taumata reservoir if necessary at any time, and to allow of direct supply to the Lytton road pump if required, provision has been made for a 12in. main along Ormond road from Hansen road to Lytton road, a distance of about 65 chains.

RECOMMENDATIONS

HE following recommen--1 dations, with estimates of cost, are made : £ 1. Approx. 3.25 miles of 12in. pipeline, intake of Waingake 18,060 2. Valves, meters, & general improvements at Waingake 3. Approx. 18.33 miles of 20in. pipeline, Waingake to Taumata • 156,200 4. Approx. 8.82 miles of 12in. by-pass in Ormond road .. 5,000 5. Concrete service reservoir at Taumata, 5,000,000 gallons.. 31,180 Total £211,320 “If the above proposals are approved, it is also recommended that the site of the proposed Lytton road pump be shifted to a point near the intersection of Lytton road and Ormond road. These estimates are to be treated as preliminary only. Much of the field work has been very approximate, and before detailed proposals are brought down it is advisable that full surveys be made. “It cannot be too strongly emphasised that money spent on reasonably detailed investigations will always give a return in the form of decreased construction costs and increased efficiency. If at all possible, the sum of £IOOO to be expended over a period of two financial yeai-s, should be set aside for investigations. “A direction Is also requested as to whether the route through Makaraka is to be followed, involving an extra cost of about £2400.

PARTIAL ALTERNATIVE

ajiyiß. F. G. Clapcott has IVS su Sß’ested a partial alterA A native at the Gisborne end of the pipeline. In this proposal, the new pipeline would follow the route of the existing pipeline to Lytton road. The pipeline size would be 20in. diameter as far as the borough boundary, but from there to Lytton road, a distance of about half a mile, reconditioned 15in. pipes from the old line would be used. A service reservoir of 2,000,000 gallons capacity would be built on the flat ground near the intersection of Lytton and Gladstone roads, and pumps installed to pump water as required from the service reservoir into the mains. “The existing service reservoir on Taumata Hill would remain and be used purely a s a balancing tank to maintain a uniform pressure in the reticulation, only at such times as may be necessary. The saving in capital ex-penditure-after modifying the first proposal to allow for a 2,000 000 gallon service reservoir, in order to put the two schemes on a comparable basis—would be about £IO,OOO.

BUILDING BY SECTIONS

UI F the above proposals were 1 approved, and financed wholly by means of a loan, the annual charges, on a 30-year table mortgage loan at 3 1-4 per cent, would be £II.OBO. The total amount repaid over the period would be £332.000, or 57 per cent more than the actual cost of the work. On the other hand, if the whole work could be financed out of revenue, the total cost would be only £211.320. “If it were possible to meet some. of the cost out of revenue, the saving would be 57 per cent of the actual amount expended. “By doing the pipeline work piecemeal, and replacing the worst portions of the existing pipeline first, the annual maintenance costs on the existing line could be kept down; and, as the line was graduallv replaced by larger pipes, the actual delivery capaocitv would increase as the work proceeded. Under such conditions, it might be possible to prolong the life of portions at least of the existing pipeline for as much as another 15 years. “Of course, if this procedure were adopted, there would be a minimum amount of annual replacement, to go below which would not be economical. This length is estimated at about half a mile per annum, at a cost of about £4,300 per annum. On the other hand. If £ 14.200 per annum could be made available, the work would be completed In 15 years, and it should be possible to do the whole work out of revenue, provided a commencement could be made in the near future. “The effects on the rates, on the present rateable value of the whole borough, of the above suggestions would be: —£4,300 p.a.—A rate of 0.9 d in the £l, or an increase of 5.4 per cent on the existing rate; £14,200 p.a.— a rate of 3d in the £l. or an increase of 17 per cent on the existing rate; £II,OBO p.a.—a rate of 2s 3d in the £l. or an increase of 14 per cent on the existing rate. “In connection with this suggestion, it should be noted that the estimated cost of an adequate main service xeservoir is £31.180. In order to reduce difficulties of maintenance on the existing line, and to allow of easier construction of a new fine, it would be advisable to proceed with the construction of this reservoir compaiatively early in the scheme. “As it would be uneconomical to spread the construction over a period much longer than two years, this would require the provision, *of fairly large

annual sums, either by loan or frHm revenue, for the work. “An alternative suggestion would be to construct the reservoir in, say, four sections, each a unit in itself, seoarately constructed, and each costing about £B,OOO. “The scheme as outlined is thus extremely flexible, in that it could be initiated for an annual expenditure of about £4,300, or could be carried to completion in a period of about two vears for an annual outlay of £105,000, provided materials were available. In any case, the urgency of the work ys such that it should be begun as soon a s mavbe. and should be completed within the next 10 years if possible—certainly within 15 years."