Title:  The Irish Builder, xxxiv 102
Date:  1 May 1892
Place:  Kilmacanogue, Co. Wicklow

 

THE SEWAGE DISPOSAL OF ISOLATED DWELLINGS

The first works which it is proposed to describe are those at the Rathdown Union, Loughlinstown, Co. Dublin. For many years great difficulties had been experienced in the attempts to dispose of the workhouse sewage. The pail system had been adopted some time ago instead of water-closets, in order to reduce the quantity of sewage as far as practicable. The laundry water was conducted into a closed tank, from which it was pumped into a cart and carried up by horse labour to the land at the back of the building; it was here thrown into a large manure heap, where the closet pails were also emptied; this heap being always very offensive in summer. But the rest of the slop water had still to he disposed of, and this, as I have already stated, is just as foul and offensive as water-closet sewage; it was conducted formerly through a large stone drain into an open pond, between the river and the road, outside the walls of the workhouse. The liquid collected in this pond, and percolated through the adjoining gravel-pits, gradually making its way into the river. In reality the pond was nothing better than an open cesspool, which in warm weather emmitted an intolerable stench. Frequent complaints were made by residents in the neighbourhood and persons who had occasion to make use of the road, of the foul smells from this pond, and the rural sanitary authorities were, therefore, placed in a anomalous position of being guilty of the creation of a dangerous and offensive nuisance close to the doors of the boardroom where the guardians sat.

It is right to add that this flagrant breach of the Public Health Act by the guardians, who were supposed to administer it, was attributable to the difficulty which assailed them when they considered how this nuisance could be abated. No public sewer existed near the workhouse, into which the sewage could be conducted. The building is situated near the foot of the ground belonging to the union, which rises sharply behind it until it reaches the railway, so that any system of sewage disposal by gravitation over the land was impracticable.

Several attempts were made to obtain the necessary consent for the construction of a main outfall sewer to the sea, but all these efforts were strenuously opposed by the owners of property and the commissioners of the adjoining township. Eventually the guardians decided to consult Mr. Charles P. Cotton, M. Inst. C.E., Chief Engineer to the Local Government Board. Mr. Cotton recommended that the sewage should be conducted into a closed tank, and then pumped to the high land at the rere of the institution, and distributed over its surface. The guardians adopted his suggestion, and the writer was engaged to design and superintend the necessary works.

In this connection it may be mentioned that the water supply to the workhouse was obtained from the Vartry main by meter, at a cost of about £100 a-year. To save a portion of this heavy annual expenditure the guardians considered that it would be wise to make provision for storing and utilising the roof-water of the buildings. What is known as the “separate” system of drainage was, therefore, adopted, and two large rainwater tanks were constructed in the airing yards at the back of the institution. These tanks are 38 ft. square and 6 ft. deep, each tank containing 52,500 gallons. The total superficial area of the roofs is 3,850 square yards, so that one inch of rainfall represents about 18,000 gallons of water.

It should be mentioned that all the surface water from the yards is taken into the sewage drains, as the writer considered that the risk of pollution would be too great to take it into the rain water tanks. A gravel filter is constructed at the side of each tank, by which the water is filtered on its way to the tank. The water is pumped by a steam pump into storage tanks at suitable levels, and is used in the laundry and kitchen. A reduction in the consumption of Vartry water has been effected by the storage of the rain-water, which amounts to a saving of about £50 per annum.

The sewage drains are all laid, in accordance with modern practice, on concrete with water tight joints, in straight lines, with manholes at each change in direction. All the sewage, with the exception of that from the hospital, is conducted into two underground tanks, each measuring 15 ft. long, 10 ft. wide, 6 ft. deep, and containing 5,525 gallons. The object of duplicating the sewage receiving tanks is to enable one section to be cleaned out while the other is in use. Overflow pipes are taken from both sections, and conducted to the under drain from the irrigation ground, to which reference will he made hereafter. It was not thought prudent to take the hospital sewage into the tanks already described. It is therefore conducted into an independent tank, in order that it may be disinfected when necessary, so as to prevent the spread of infectious disease. Before the sewage enters the receiving tank, it is passed through strainers, so that the coarser particles and the suspended matter and other elements which are likely to choke the pumps are removed.

The dry weather flow of sewage is 30,000 gallons per week; it is pumped from the receiving tank four times a-week by a pair of small direct-acting steam pumps fixed in one of the back yards of the main building, and delivered into the distributing tank. This distributing tank is built of concrete plastered in cement, and situated overground at the summit level of the land near the railway. It is also made with a division wall, to facilitate cleansing. When the sewage has been pumped and one section of the distributing tank is filled, a sluice is opened and the sewage is conducted by a closed pipe carried in an embankment between the plots devoted to irrigation, to a central sluice chamber fitted with two sluices, by which the liquid can be conducted to either side. The distributing pipes run right and left from the centre chamber, and terminate at a pair of distributing chambers, each fitted with four sluices, and situated at the intersection of four of the plots devoted to irrigation. By opening one of the eight sluices in the distributing chambers, the liquid can be discharged into any one of the eight plots prepared to receive it. Each of these plots was accurately levelled, and at a depth of about 4 ft. beneath the surface a herring-bone system of agricultural drains was laid, discharging into a central main under drain connected with an outfall drain. These under drains are all provided with manhole chambers, to facilitate inspection and cleansing, and a sluice is also fixed on the outfall drains near the distributing tank. By closing the sluice, all the the under drains can be filled and flushed out, and this prevents them getting choked up. The main outfall under drain is carried down the hill past the hospital, receiving on its way the rain-water from the hospital buildings and also from the lodge buildings. As I have already stated, the overflows from the sewage receiving tanks are also conducted into this main drain. It is carried along inside the workhouse grounds in the front of the buildings for some distance, and it then crosses the road and delivers into the gravel-pits near the river.

It will be observed that this arrangement ensures that all the foul liquid shall be filtered through about 4 ft. of land before being discharged, and the effluent is found to be bright, clear, and free from smell. By sub-dividing the land into eight plots, and adopting the system of intermittent downward filtration, each of the plots receives its dose in succession, and then enjoys a long interval of rest, so that there is no fear of the land becoming sewage sick.

Part of the irrigation ground has been planted with osiers, which feed greatly upon the sewage, and flourish under the treatment. Italian rye-grass has also been grown. The master reports that during the year 1891, between eight and nine tons of prime hay were saved, which realised about £40, and a sum of £3 1s. was received for willows grown on the osier beds.

In practice it is found that the quantity of land devoted to irrigation — which is about three acres — is in excess of the requirements, so that, so far from the disposal of the sewage being any longer a difficulty, the only matter of regret with the master of the workhouse is, that there is not sewage enough for the successful cultivation of land set apart for the purpose.

It is probable that in the future the quantity of sewage will be largely increased if water-closets are substituted for the present pails, and it was with a view to this that a large area of land was laid out for irrigation. The works have now been in operation for some years, and have given great satisfaction, so that not only has a glaring breach of the Public Health Act been successfully cured, but the sewage and rain-water of the institution have been fully utilised. The fertilising value of the former, and the saving of Vartry water by the storage of the latter, have combined to yield a substantial pecuniary return more than sufficient to pay working expenses. The annual consumption of coal for pumping is twenty tons, and the cost in 1891 was £22. The attendant who has charge of the works has also other duties to perform, the estimated annual proportion of his wages chargeable to the sewage account is £40.

The total cost of the works was £3,100, and they were carried out, to the entire satisfaction of the writer and the Engineers of the Local Government Board, by Mr. John Pluck, of Kilmacanogue, County Wicklow.