WATER AND DRAINAGE EXTENSION.

Wairarapa Age, Volume XXXI, Issue 9054, 1 April 1908, Page 5

WATER AND DRAINAGE EXTENSION.

MR LAING-MEASON'S REPORT. The report of Mr G. Laing-Meason, M. Inst., C.E., upon the extension of the water and sewerage systems of Masterton, was presented to the Borough Council yesterday evening. WATER SUPPLY WORKS. Mr Laing-Meason commences by stating that he made visit® to Masterton on January 14th, 28th and February 10th, spending about a week on each occasion in collecting information and in making a close ' and exhaustive examination of all the works and their possible extension and improvement. During the whole'of the time of his visits a persistent drought had prevailed, and he therefore had the advantage of seeing the river, creeks and subsoil water at their lowest levels. On the 28th February he paid a fourth visit, and although lie did not gauge the supply, he observed that it contipued to fall rapidly. Sources of Supply. Dealing with the sources of supply, he says he found the upper spring creek low and generally in a bad condition. Stock had free access to it at all points, ar>d refuge drainage from a farm-steading drained towards it. The water, though clear, had considerable odour and taste, and he had also observed this taste and smell in water drawn from the town mains. The lower intake creek appeared to be pure. The supply had diminished in volume in normal weather during the past few weeks, but he thought there might again be an increase in the volume of both creeks should favourable river conditions arise. A Danger.

The report proceeds to outline the existing works, and the engineer points out that there was evidence of roots of plants having insinuated themselves into the earthenware pipes. How far the mischief had developed he could not say, but that it would become serious unless remedal measures were taken there was little doubt. Not on'y was there danger of blockage and interruption of the supply, but also of pollution of the water by reason of the presence of vegetable matter in the pipes. He advised that twelve concrete inspection sumps should be constructed along the line of earthenware pipe, so that the pipe could' be thoroughly cleaned.

On the 14th January the inflow of water into the reservoir was 818,000 gallons, and this had fallen by 168,400 gallons on his visit on the 10th February—an interval of 27 clays between his first and final visits. Consumption per MeaC. The estimated number of consumers of water at present, Mr Laing-Meason estimated to be nearly 5,000. The daily draw off from the reservoir before the supply began to diminish very much was 750,000 gallons, and thus the consumption (waste and all causes included) amounted to 150 gallons per diem per head of the people on that date, and probably about the same amount left the mains daily during the preceding dry weather. Capacity of Pipes. The 10-inch main was capable of discharging at the rate of 920,000 gallons a day without lowering the pressure below 431b per square inch. When the pressure was reduced to 301bs, as frequently was the case during Mr Laing-Meason's visits, the draught on the mains was at the rate of 1,037,000 gallons. Mr Reynolds' scheme provided for a supply of 50 gallons per head for 12,000 people, and for a draught at the rate of 75 gallons per head during part of the day, or a maximum rate of discharge of 900,000 gallons. The pipes he provided were therefore equal to the task imposed on them. Mr Laing-Meason calculates that the ultimate capacity of every main is not less than one and a-half times the present demand, and that the great majority of them have at least twice that capacity. Accordingly none of the 6*inch, 4-inch, or 3-inch mains would require to be replaced by larger ones for a very considerable time. Waste of Water. After referring to the pressure in the mains, draw-off, and leakage, the Engineer states that of the very large amount of water leaving the night and day, probably the greatest part was used in watering gardens, lawns, shrubberies, and so on; but there was no doubt a great amount of waste was due to leaky taps, faulty ball-cocks on flush cisterns, as well as from carelessness. Condition of Pipes. Mr Laing-Meason found the galvanised iron pipes badly affected owing to the marked tendency of the water in the Waingawa River to corrode iron. Some of the pipes that had only been in use for three or four years had lost from one-third to half of their original bore by the formation of nodules, and all were much corroded. He recommended the substitution of lead for galvanised iron pipes, pointing to a method whereby the cost of replacement would not amount to more than £6OO.

The older cast-iron pipes which he examined exhibited bad casting and great irregularity in the thickness of metal, hut he could not say what proDortion of the pipes in the ground were thug faulty. Concluding Remarks. In closing his report, Mr LaingMeason states that by the prevention of leakage and careless waste, and with the addition of direct intake from the river, the existing system is capable of supplying the present population of Masterton with 150 gallons per head per day; at 8,000 the supply would be 100 gallons; and when the population is 12,000, 50 gallons per head. It is, continues the Engineer, a question for the ratepayers to decide whether they will consent to such a restricted, though certainly liberal, allowance of water, or whether they will sanction the necessary outlay to obtain a larger supply. The Two Schemes. In the event of it being decided not to increase the present volume

of supply, the following work will / be required:— Scheme No. I.—(a) The construction of a new intake direct from the river. (This work is in hand and well on to completion), (b) The construction of twelve inspection sumps, (c) The putting in of the additional sluice and scour valves. In the event of its being decided to acquire a larger supply, I make the following recommendations: — Scheme No. 2. —(a) The construction of a new intake frcm the river, as in Scheme No. 1. (b) The duplication of the pipes from present upper intake to reservoir, (c) The construction of twelve inspection sumps bet-veen intake and reservoir, (d) The duj lication of the 10-inch main from reservoir to town; and the laying of an 8-inch steel "main from Renall Street, along Chapel Street and Perry Street to Queen Street, (e) The additional sluice and scour valves, as in Scheme No. l.

It is pointed out that the two 10inch mafns would discharge up to 1,800,000 gallons, which would give the present number of users 300 gallons per head per diem; with 8,000 people, 200 gallons; and with 12,000 people, about 100 gallons. With regard to the suggestion that it would be desirable to draw the town supply from the rock-bound river bed, some 2$ miles up stream of the present intake, a fatal objection was that the present pipes would not be able to stand the pressure. Estimates of Cost, The estimates of cost are given as follow: Scheme No. 1. —(a) New intake from river, £350; (b) 12 concrete inspection sumps, £130; (c) additional sluice and scour valves, £120; (d) engineering, supervision, and constructive contingencies, £300; total, £9OO. Scheme No. 2. —(a) New intake as in Scheme No. 1, £350; (b) duplication of pipes to reservoir, £2,400; (c) 12 enlarged inspection sumps, £180; (d) duplication of 10inch conveying main to junction of R<?nall and Queen Streets, £6,520; (e) 8-inch steel main along Chapp«, and Perry Streets to Queen Street, with hydrant valves, £390; (f) additional sluice and scour valves, as in Scheme No. 1, £120; (g) engineering, supervision and constructive contingencies, £900; total, £10,860. SEWERAGE.

The Existing System, . Having dealt exhaustively with the water supply, Mr Laing-Meason proceeds to report upon the proposed extension of the sewerage system. He states that he has made an exhaustive examination of the existing sewers and sewage disposal works. The area of the Borough at present sewered is about 450 acres. All the remaining part of the town to th« southward cannot be carried by gravitation to the site of the existing treatment works, and all the sewage from any extensions in that direction must, therefore, be lifted if the present site is retained. For some tine after the completion of the workF, Mr Laing-Meason says, the tark effluent was passed through filter bpds of the intermittent contact type, but for some reason these have been discarded and the beds dismantled, the concrete walls and some of the filtering medium only remaining. In Lincoln Road, Pine and Cole Streets the ground was originally a white pine swamp, and as a consequence great difficulty was experienced in jointing the pipes when they were laid, and there is no doubt that many of the joints are not water-tight. When Mr Laing-Meason saw them in extremely dry weather, it was evident that the sub-soil water was entering them at many points, and that they were acting more as water-drains than as sewers. If, he says, any biological action in the tank is to be expected , the whole of these pipes must be uncovered, al\ leaky joints made water-tight, and all faulty or inefficient pipes must be removed and replaced by sound, well burnt, and well glazed earthenware ones. He alsu observed signs of leakage in some of the manholes on these sewers. In the remaining sewers there is, he believes, very little leakage. When he examined the septic tank he estimated that at least two-thirds of its capacity was filled with sludge. With such a very reduced water space the sewage was, of course, traversing the tank very i rapidly, and as it was extremely attenuated (little mora than slightly dirty water) no bacteriological action whatever could have been taking place. The capacity of the tank, when clean, is about 122,000 gallons, or less than a day's supply from the present users at a dry weather flow of 30 gallons per herd, representing a "stay" in the tank of 22£ hours; but even if the entry of subsoil water into the pipes were stopped the dry weather flow would, the Engineer estimates, considerably exceied 30 gallons per head, and, would, probably, approximate to nearer 50 gallons, which would reduce the "stay" in the tank to 13J hours—a quite inadequate duration in his opinion. There should not be less than 22 to 24 hours duration. The capacity of the tank is thus too. small already, and as mors houses are built on the present drainage area, more tank space would have to be provided in the immediate future. After levels were taken, Mr Laing-Meason found that the available fall was hardly enough for intermittent contact bed filters, and certainly insufficient for the continuous filter, which was the best system. "Considtring these and the other objections 1 have mentioned," concludes the Engineer on this subject, "and having regard to all the. circumstance?, I am strongly of the opinion that the present site of the sewage disposal works, should be abandoned, and that new works should be established in a more suitable position."

Proposed Extension—Mr Dobson's Scheme. The report proceeds:—"l have very carefully investigated the sewerage extension formulated by Mr Douglas Dobson, A.M. Inst., C.E., and I consider that his general arrangement cannot be improved upon. I have analysed and checked the sizes, lengths, and gradients of all the pipes suggested by him, and I find they are all quite suitable and correct. By his proposals 850J chains of pipe sewera are provided for sewering 34 streets, or portions of

streets, as well as for two lines of sewers which would cross private property. The whole of these proposed sewers are concentrated at the junction of Herbert Street with Colombo Road, where they discharge into the projected new outfall. I differ from Mr Dobson, however, in regard to the substitution of castiron for earthenware pipes in many places. With the exercise of precaution and care there is no reason why the joints of the earthenware pipes should not be made perfectly wate tight, notwithstanding the presence of subsoil water; and with tight joints good earthenware pipes are to be preferred, for they are not subject to contraction of bore as are the cast-iron pipes; and, besides, they cost only half as much and last much longer. Throughout all wet ground I have provided for laying, temporarily, field pipes at a little lower level than the pipe sewers to carry away the subsoil water while the sewers are being laid, which will allow the joints to be made perfectly water-tight. I consider the manholes shown by Mr Dobson are too few and too far apart for the proper inspection and control of the sewers. I have, therefore, provided for 39 additional ones." New Outfall Sewer. "I viewed the line of the proposed new outfall shown on the plan in the Council Chambers. This line commences at the foot of Herbert Street, and running in a generally southessterly direction, crosses the Manaia Road, and ends near the junction of the Waingawa and Ruamahunga rivers. Satisfactory gradients are obtained on this line, and the ground traversed is, for the most part, good. For the proper inspection and control of the outfall sewer, I consider that the number of man-holes should be increased from 12 to 23, and there should also be a like number of lampholes. With these few amendments I think the provisions made by Mr Dobson are all that is required." New Sewage Disposal Works. After visiting several places along the bank of the Ruamahanga river, and finding them objectionable, Mr Laing-Meason visited the proposed site near the junction of the Waingawa and Ruamahanga rivers. The proposed site is 18 feet or 20 feet high, and at the foot of the terrace is a large accumulation of fine shingle and sand which is excellently suited for sub-irrigation should it be required. The nearest house to this site is not less than half a mile to the south, and the nearest point of the Gladstone road is about the same distance to the eastward. Mr Laing-Meason proposes to place the tanks and filters in an excavation nine feet deep below the top of the terrace. The tanks would be of open type, and the object of placing them in an excavation is to protect the scum which forms on the surface of the sewage in the tank from disturbance by wind. There would be three tanks, each 110 feet by 35 feet and 6 feet deep; and each capable of holding 150,000 gallons of sewage. Thus at 50 gallons of sewage per head.

two of the tanks would serve a popu-

lation of 6,000 with a "stay" of 24 , hours in the tank, whilst the three tanks would similarly serve 9,000 people. Grit chambers, baffle walls, scum boards, screens, and all other accessories are provided for. The filters would have a surface area of 500 square yards, and a depth of six feet, which is sufficient to deal with the sewage of 10,000 people; and the tank effluent would be distributed over the filtering medium by Stoddart's patent distributors. These distributors are, the report states, most efficient, havf no mechanical parts, and require no attention beyond sweeping down once a fortnight with a broom. The filtrate would be discharged on to the sand accumulation; and after percolating through this would reach the river in a pure and perfectly inocuous condition. A thick plantation of pinus insignus and macrocarpa would be planted round three sides of the tanks and filters to protect them from the wind, and to absorb any slight odour they might give off. Mr Laing-Meason concludes this portion of his report:— "I have every confidence in recommending the adoption of this scheme to the Council. The tanks and filters I have provided for will serve a population of at least 9,000 people; and they would be so arranged that when it is required, they could be easily and cheaply extended. The site, for sewage? disposal purposes, is a perfect one. It is at least half a mile from any habitation or road, and there does not appear any likelihood of close settlement near the site in the future. The Cost. Mr Laing-Meason estimates the cost at £22,960, viz., reticulation, £12,235; outfall sewer, £5,310; sewage disposal works, £3,415; engineering and supervision and constructive contingencies, £2,000. Concluding Remarks. In his concluding remarks on both schemes, Mr Laing-Meason says:— "So far as the sewage is concerned, the problem admits of no other solution than the one I have detailed. The execution of the sewage disposal works cannot be long delayed, and the extension of the sewers to the southern part of the town is equally urgent. The expenditure on these works, amounting to the total of £22,980 is heavy but unavoidable. "On the other hand, no such appears to me to be necessary in respect to increasing the water supply. The present supply is a good and liberal one, giving an allowance per head of population, much in excess of the supply usually afforded. With the additions and improvements I recommend in Scheme No. 1 it will be still better, for the source of supply will be pure and unfailing; the conditions in the pipe between intake and reservoir will be much improved and relieved of any danger of blockage or contamination from vegetable growths in the pipe; and, in the town, the installation of the additional sluicj valves will ensure the immediate restitution of pressure at any point in case of firp.

"If the supply is augmented it would, in my opinion, be more of a luxury than a necessity, and the price of the luxury would be £IO,OOO. "The question is, of course, entirely one for the Council and ratepayers to decide, but my advice is to improve the existing works as I have suggested in Scheme No. 1, and to leave the duplica-

tion of the supply to stand over for a few years. If this is done, I am sure there will be no reasonable cause for complaint with the existing allowance, and the interest on capital saved during, say, six or eight years, would amount to a very substantial proportion of the cost of duplicating the system. "I have to thank the Town Clerk and other officials of the Council for the assistance they rendered me in the prosecution of my investiga- | tions."