BOROUGH DRAINAGE.

Wairarapa Age, Volume XXX, Issue 8475, 29 June 1907, Page 6

BOROUGH DRAINAGE.

THE ENGINEER'S REPORT

AN ESTIMATE OF THE COST. A special meeting ' of the Masterton Borough Council has been convened for Tuesday evening next, when the special report of the Borough Engineer (Mr Douglas Dobson) on the drainage system will be considered. The following letter was addressed by Dr. R.' H.Makgill, District Health Officer, to the Borough Council on August 16th lasjfc yaarl desire to draw the attention of the Borough Council to the need J'or reorganization of the drainage scheme of the borough. There are in the first place large areas of the town, notably in the Kuripuni iistrict. which cannot at present lve any advantage from the drain scheme owing to the levels bein ,o low to connect with the existin? wers. AH that part of the Boro .. ; h south of Cornwall and Bennington Streets and south-east of Worksop Road is in this unsatisfactory condition. I understand that some 300 houses are thus affected, and these are rapidly increasing in number. . The nightsoil service is Only a partial measure—the slop wastes remain to be disposed of, and these are just as likely to lead to trouble—outbreaks of diphtheria, typhoid, and other infectious diseases — as anything else when the area of land round each house is insufficient for sanitary methods of dealing with sewage. It is very necessary then for the Council to face this difficulty without waiting for these troubles to arise. Provision is, I believe, now being made for an extension of the water service. The only question is whether it will be better in the end to lay a separate system of sewerage for the parts of the Borough mentioned, leading to a new treatment tank, probably somewhere about the bank of the Waingawa River, or to convey it to pumping station, and so to the present outfall works. Against the latter proposal must be considered the cost of such pumping, and also the fact that the present tank installaton is not capable of dealing with the amount of. sewage already passing into it. This leads me on to a second and a very important question affecting the drainage of the town, and one which the Council must be prepared to take in hand as soon as possible. There is.no doubt that the present method of treating the sewage is a failure. Complaints have reached me from persons living further down the Ruamahanga River as to the pollution of the water, and after an inspection of the existing conditions 1 am bound to report that these complaints have tion. The trouble with the tank itself was shown last year to be partly or entirely due to the excessive amount of sewage, which was found to be far beyond its calculate powers of disposal. This excess may be to some extent caused by wastefulness on the part of householders, but also there is doubtless a great deal of ground water getting in from certain districts. There would then appear to be two remedies, either to increase the capacity of the tank, or to relay. the sewers—a very troublesome and costly business indeed. Stricter supervision of the taps and other service fixtures in the houses should, I think, be exercised in any case, and so help to keep down the flow. But beyond the matter of the capacity of the tank we must consider the treatment of the effluent before it passes to the river. At present thisj is being done by what can only be called a sort of apology for the land treatment. The area, however, is quite insufficient, and it seemn difficult to acquire the necessary space without encroaching uncomfortably near residential properties. The solution of this difficulty is to be found by substituting properly constructed aerating beds for land treatment if the fall to the river is sufficient. Unfortunately there seems to be evidence that this fall is not available; if not, to continue the works on the present site, involves one of two very costly remedies, i.e., acquiring a large area of land or pumping the whole effluent to the top of the filter beds. It is entirely an engineering question, and therefore one on which I am unable to advise. I can only emphasize the need for a complete reorganisation. To summarize the position:—There are two difficulties to overcome—(l) The

drainage of the low-lying levels of the town. (2) The enlargement of the present tank and treatment beds. The solution would seem to be discoverable in one of the following proposals, but the choice must depend on the engineering possibilities involved:— (1) To find a site—probably on the Waingawa River—on which a tank and filter beds built on modern lines can be erected, and to which the whole of the sewage of the town can be conveyed by gravitation. The present work could then be abandoned, and the land ultimately used for other purposes. (2) To have two separate drainage areas—one dealing with the low levels and gravitating to new treatment works on the Waingawa River, the other leading as now to the present tank —which would require to be enlarged or the ground water excluded from the sewers, and (a) proper aerating beds constructed, dependent on fall available, or (b) more land acquired and regular land treatment adopted, or (c) whole tank effluent pumped to the aerating beds, if fall to river insufficient. (3) Present system and outfall works retained, subject to alterations as in the second scheme, with (a) a pumping station erected in such a position as will enable the low levels of the town to gravitate to a collecting tank, from which the sewage can be raised to the septic tank, or (b) the adoption of, the Shone system for raising the sewage from these low levels to the present sewers. Probably the first scheme, if it be practicable, will prove the most satisfactory, as the others depend [upon pumping systems, which involve a continuous source of exipense. Trusting the Council will appreciate the seriousness of the position. —I am, etc., R. H. Makgill, District Health Officer."

The Engineer's report is a a follows: —His Worship the Mayor, Masterton. Dear Sir,—ln accordance with your instructions to report on the extension of drainage and on the question of a new outfall, I beg to submit the following scheme :

SCHEME FOR.THE SEWERAGE OF THE WHOLE OF THE BOROUGH OF MASTERTON.

1. Preliminary Investigation.—As a preliminary investigation, surveys have been made and levels taken as followsOf about 13 miles of streets within the borough for the purpose of fixing grades of se.vers and the direction of flow of same when sewered, and to fix a [common outfall for the whole of such streets if possible; of these 101 miles are included in the area now to be sewered. Of a trial line from Herbert Street down the Kuripuni Creek to the Ruamahanga River. Of three trial lines from the Kuripuni Creek in S.W. direction to the Waingawa River. Of a trial line from the present outfall down the Ruamahaijga to McGregor's, being a total length of about 30 miles of which the traverses and sections have been plotted. Outfall selected. This investigation furnished the following information,, viz., that the outfall from Dixon Street, Bunny Street, Hogg Crescent and Sussex Street must discharge along Makora Creek to Columba Road. Michael Street, Chapel Street, and Dixon Street South, High Street, and South Road north of Cockburn Street must idischarge via Kuripuni Street to Columba Road. A further section of South Road north of Millard Avenue must (discharge via Cockburn Street to Columba Road. Herbert Street must also discharge on to Columba Road. That none of the sewage so discharged can be delivered to Johnston Street outfall except by mechanical means, whilst the whole of the sewage now discharging into Johnston Street sewer can be carried by gravitation along Columba Road to its lowest part, viz., Herbert Street, and thence by one outfall to the Manaia. Makora Road can alsojjbe drained into the same outfall. That all land available for outfall sites on the Ruamahanga River is liable tb floods and devoid of any special features or advantages for the treatment of sewage. That trial lines run S;W. to the Waingawa River showed no advantage over the Manaia route. That the trial line down the Kuripuni Creek, whilst giving the best .hydraulic gradient for an outfall leads to low ground not so suitable as the one selected. That a line crossing the Kuripuni Creejc in Tatham's and the Gladstone Road above Pond's will give a gravitation outfall with a good grade and leads to a table land on the banks of the Waingawa River near its confluence with the Ruamahanga River where the conformation of the land is better adapted for a sewage works tha i any other site inspected. After the foregoing investigation 1 have adi pted the last routo as the best available offering a good hydraulic grade and offering a gravitation outfall for the whole borlJugh and thereby saving all costs of pumping plant and maintenance of same, and also offering a site which I believe is the best avail able for the end in view. The outfall to the treatment of the site is a somewhat lengthy one but no better offers at less distance and the capital cost incurred therein will be compensated for in a measure by the entire saving of lifting the sewage to the present outfall in Johnston Street. As to whether this site be abandoned or not is a question for your consider- | ation but if not then the necessary amount of capital must be spent on it to provide for the treatment of j all the sewage of the borough and in addition plant be provided for pumping the sewage from the lower levels of the town to the Johnston 1 Street main and an annual expenditure for its maintenance. I am of the opinion that the Manaia route is the natural outlet for the town and that it would be wise to incur the extra expenditure entailed in going there now in lieu of on permanent works at Nursery Road. Extensions Proposed.—The extension of sewerage proposed will include the whole of Lincoln Road to the Butter Factory and Bentley and ! Villa Streets. Also Park Avenue, Archer, Elizabeth and Church Streets and the sewering of Hacker's Estate. The sewerage of Chapel Street from the Fish Ponds, Dixon Street, South Bunny Street, Hogg Crescent and Sussex Street to Columba Road. The extension of the present sewers in Kenall Street, and Cornwall Streets to the railway line, and the sewering of Pownall Street. The sewerage of part of Michael Street, Walton's Avenue, to High Street from Vivian Street, and South Road

via Kuripuni Street to Columba Road, also Herbert Street. In the drainage of all waterlogged ground or ground charged with spring water, I would suggest that cast-iron mains be used, as being cheapest in ultimate cost, and that several lengths of 4in castiron pipe be used at every connection with main. As the infiltration of subsoil water to the present sewers in Lincoln Road and Pine Street is excessive, I would i*ecommend that such parts of these mains as are proved to be admitting water be made good either with castiron mains or concrete around the present pipes. For the rest of the system, I propose using first-class quality earthenware pipes. Outfall Station. —From the outfall main the sewage will pass into detirtus tanks, where any heavy particles will deposit, and it will be screened, before reaching open septic tanks designed to work either as one tank or in series, and provision will be made for discharging sludge from the bottom of the tank to sludge beds by gravitation if the confirmation of the site will permit of it. Adequate aerobic filter beds are provided for continuing the biological process from the tank before discharging the effluent on to the land or to the rivor. In addition, I propose that 10 acres of land shall be levelled and under-drained so as to permit the intermittent downward filtration for down sub-irrigation. Provision will be made in the design of the plant for passing any or all the tanks and also the filters and the ground prepared for irrigation will be so arranged as to receive this effluent from the tanks or filter beds, or temporarily from the sewer direct. By this provision the station will be adequately provided for the effectual treatment of sewage so that no nuisance will exist therefrom. In the estimates furnished no provision has been made for acquiring the land required— along the outfall I would suggest that an easement onty be acquired, giving the outfall the right to construct the sewer and to repair the same at any time—but at the outfall a large area of land should be acquired and a right-of-way into the same. It will be necessary to provide quarters at the outfall station for one permanent hand, it being much better to keep one regular hand regularly employed in managing the outfall than to depend on casual attendance, and the biological plant will, in addition, want constant attention. This work is accompanied by 21 sheets of plans and sections, a detailed list of the sewers in the reticulation proposed and an estimate of the proposed works. The detailed plans of the outfall station, septic tank, and filter beds are not yet completed. —Yours, etc., Douglas Dobson, Borough Engineer. MASTERTON DRAINAGE

EXTENSIONS—ESTIMATES OF COST. Reticulation.—Six-inch earthenware sewer, laid 342 chains, £2,565; 6-inch castiron sewer, laid 159 chains, £2,326; 9-inch earthenware sewer, laid 165 chains, £1,485; 9-inch castiron sewer, laid 145 chains, £3,480; 15-inch earthenware sewer, laid 40 chains, £600; 63 manholes, £756; 28 flushtanks, £420; 112 lamp-holes, £224; 400 house connections, £1,000; allowance for further work required in Lincoln Road and Pine Street. £1,200. Outfall—ls- - earthenware f-main, 240 chains, £3,840; 12 manholes, £144; 25 lampholes, £SO; 6 25ft foul-air vents, £SO; allowance for concrete in wet ground, £I,OOO. Outfall Works—2 detritus tanks, 20 x 10, and 4 septic tanks, say, 60 x 40 each, £1,500; excavation, £250; fittings and pipe conduits, £250; filter beds, 300 yds concrete, £6O; filling 2,500 yds at 2s, £250; levelling 10 acres of land and subdraining same, £500; cottage and fencing, etc., £300; contingencies, £2,310; engineering, £1,275; total, £26,775. To which must be added cost of land, etc., right-of-way for outfall main. DOUGLAS DOBSON, /

Borough Engineer.-