THE DRAINAGE SCHEME.

Stratford Evening Post, Volume XXXIV, Issue 73, 19 November 1912, Page 7

THE DRAINAGE SCHEME.

o THE ENGINEER’S REPOUT. COST £4-183. Messrs Robinson and Christopher’s report on the drainage proposals was submitted to the Borough Council hast night. The full report is as follows; “In accordance with your instructions we have gone into the matter of the drainage of a portion of the Stratford Borough, and have t.he_ honour to submit to you the following re-

port and estimate of cost in connection therewith. The portion of the Borough under consideration lies generally between Pembroke Road on the north, Regan and Rosalind streets' on the south and eastwards from Broadway. The report, generally deals with the drainage of tnis- area, only, but in designing tire required system, it would have been unreasonable and contrary to thoroughness and ultimate economy to absolutely ignore future possible extensions to other portions ol the Borough, hence brief mention and suggestion is made in connection with tins matter when it is feasible and worthy of consideration. SYSTEM OF DRAINAGE. '

Ihe system on which the drainageof the area dealt with is planned is that of simple gravitation, the sewage ultimately having its outfall into a septic or hydrolytic tank. In all cases the sewers have been figured and plotted at grades which will allow ol free flow' in the pipes without having recourse to special flushing. The question of locality of sewage outfall and tank may fairly be considered the most important in connection with the whok scheme, as on it depends the final satisfactory disposal of the sewage, and also the available area possible to be drained. We have therefore considered the matter very carefully in all its bearings and as a result are emphatically of the opinion that the sewage should be conducted to the Borough Reserve on the south bank of the Patea River, where the present tank is situated, and that the new tank should be situated in the said Reserve approximately in the position shown on plan number two. The reasons in support of the intention are as follows (1) With the exception of the Patea, River there is no stream of sufficieiii dimensions in any suitable position into which the effluent from tank and filtering chamber could bo safely discharged. (2) Should it be decided, tc place the tank on any of the small creeks at the eastern boundary of the Borough, the Council, i n addition to having to pay heavy compensation necessary to acquire sufficient land for the purpose, would in all probabilit', have to face litigation on account o. : prejudicing the value of adjacent- properties, etc. (3) The same difficulties would have to be faced if a system of open filtration and disposal of sewage by -irrigation were proposed, whilst the extent of land required for this in a

closely settled locality puts it out o! the question. (4) It is perfectly feasible, though the .work is admittedly heavier than the average to conduct the sewage along the entire length oi Swansea Road from Pembroke Road to Patea River. (5) By so doing, n main line of server would bo established along the whole of the lower side of the town to the Patea River, exclusive of the small portion east o' Swansea Road, and the said sewci would be capable of being utilised not only for the area dealt with in this report, but for lower Fenton Street (from Cordelia Street eastwards), and also, by extending the 9 inch sewer? in Pembroke Road and Seyton Street, for the drainage of the north-western portion of the Borough, should it be found that any extra capacity existing in the tank now in operation would be required for the extension of drainage in the southern portion of the Borough. (G) The discharge of sewage effluent after treatment in tanks and filtration chamber, through a pipe tc under water level in the Patea River, could have no possible ill effect, the average proportion of purified effluent to flow if the water in the river being less than } per cent. (7) (A, long main outfall sewer 'at any even grade is always the means of equalising the quantity and quality of the sewage, and oi considerably disintergrating it. (8) It will be at once apparent that at sue), times when it is necessary to flush the detritus of settling chambers or cleanse the tank, the value of adjacent river of considerable volume and velocity and subject to frequent flooding

is very great. It. will thus he seen that for the reasons given the site chosen is highly suitable, whilst no other site is adiliissable. The only drawback is the fact that the portion of the Borough lying eastward of Swansea Road cannot be included by means of simple gravitation. This difficulty can, however, he overcome by draining that area to a sump at the lower end of Regan Street and conducting it per medium of pumping hack to the manhole at junction of Regan Street and Swansea Road whence it would he taken to its destination by the main sewer of the system under consideration. This, however, we think should ho dealt with separately in a special report. We may mention, however, that we have taken levels along the Borough boundary from Regan Street to Patca River and have gone into the question in detail before the above recommendation.

CAPACITY OF TANK ETC. The tank, the general design of which is shown on plan number -‘1 lias been figured on the basis of being adequate for tire requirements of the system being dealt with, and shown on plan number 1 for the next ten years, allowing for probable increase of population. At the present time the total capacity of tank would not he required and moreover it would not ho advisable for reasons in connection with septic action to utilise it, therefore in the designing it has been made possible to increase the working capacity

of the tank at will by simply raising tlio height of weir from filtering to discharge chamber until the tank is working at. its full capacity. The present day and ultimate sewage levels are shown on sketch. The diameter of main sewer from tank and up Swansea Road has been largely decided by gradient, and, moreover, it is capable of dealing with all the requirements of the system under consideration, with allowance for increase of population over ten years, together with the disposal of sewage from the portion of Borough east of Swansea Road, and of that brought in by future possible extcns’ons to Northwestern portion of Borough, also with proper allowance, for increase; and should the tank proposed ire ultimately found insufficient, a duplication is perfectly feasible.

GENERAL ROUTE OF SEWERS. The conformation of the ground renders it necessary to drain generally north and south to a 9 inch diameter sewer in Seyton Street, arid north to a similar sewer in Pembroke Road. The latter sewer continues straight, to the main sewer in Swansea Road. The route of the former sewer after reaching the junction of Seyton and Cordelia Streets necessitated careful consideration. It was found impossible to bring it up along Cordelia Street to Regan Street and thence to Swansea Road, and therefore it became a question of deciding between taking it down a line representing the extension of Seyton ’Street, or bringig it south along Cordelia Street to the junction of Antonio Street and thence along Antonio Street and a line representing the extension of this street, to Swansea Road.

After considering the merits of the two lines w'c decided on taking this sewer via Antonio Street for the following reasons :—(1) The length of easements required through private property is less by over seven chains. (2) The point of junction on Swansea Road is preferable at Antonio Street extension to the corresponding point at. Seyton Street extension. (3) It being necessary to make provision for draining Antonio Street we found that it was not practicable to bring the sewage back to Cordelia Street,-so that, were the 9 inch diameter sewer to be taken down on a continuation of Seyton .Street, an easement would still be required on continuation of Antonio Street to take its sewage to Swansea Road.

The sewer in question has accordingly been taken on the Antonio Street route. In regard to the easement, required, if the position is properly placed before the property holders concerned, there should he hut little difficulty in obtaining it. On plan number 1 we have indicated a possible method of draining Falstaff Street (though this is not in the area being dealt with), per medium of an easement to Sylvia Street. ESTIMATE OF COST. The total estimate of cost is £4182 14s 7d. STREET GRADING. On profile plans numbers 7 5-14, the necessary amendments to present street levels to provide in places for adequate sewer cover has been shown in dotted lines. The cost of this work is not included in the estimate submitted, as we assume that it forms a portion of the streets improvement scheme now being drawn up by your borough overseer. We have the honour to be, gentlemen, your obedient servants, ROJ3IXSON and CHRISTOPHERS.