Water is as essential to life as the air we breathe. A wholesome supply is a first requirement for healthy living. Dublin is fortunate that water of the highest quality has been on tap for over 120 years, far in advance of most other cities. The development and operation of the Dublin water supply system is an ongoing process, requiring the skills of engineers, chemists, craftsmen and general operatives. It costs £25 million to deliver 150,000,000 cubic metres each year to the city.
BEGINNINGS
Dublin has had an organised system for water supply for almost 750 years. The medieval city was only 20 ha. in extent, and was built on the ridge of high ground between present-day Thomas Street and Dame Street, near the confluence of the Liffey and the Poddle Rivers. The Liffey was tidal far to the west and therefore unusable as a source of water and the Poddle served the needs of the early settlers. By the 13th century the supply was proving inadequate and the City Sheriff was mandated in 1244 to improve the supply. An agreement was made with the Priory of St. Thomas, which owned a weir on the Dodder at Balrothery, to divert water from the Dodder to the Poddle. Under this agreement the flow in the transfer channel would be increased by raising the weir and doing certain other works, for which a fine of 5 marks and an annual rent of 1 mark was to be paid to the monks.
The increased flow of the Poddle was divided at a point just south of present day Mount Argus by a construction known as the Tongue, one-third of its waters being brought in a canal around the Liberties to a cistern near the present Waterworks Headquarters at Marrowbone Lane. From here the water was taken in an open channel along Thomas Street, and then by the 'high pipe' wooden troughs and leaden pipes to a public 'conduit' or fountain near Christchurch.
About 1670 the old cistern at the terminus of the City Watercourse was replaced by a reservoir known as the City Basin, near St. James Gate. From Dolphin's Barn to the Basin, the watercourse was carried on a rampart of earth and stone, from which the area came to be known as 'The Back of the Pipes'.
There are numerous references in the ancient records of the city concerning the upkeep of these works, and in relation to litigation and grants of water to individuals. One of the earliest is a request from King Henry III in 1245 for a supply of water for the King's Hall. The lead pipe which carried this supply was uncovered in Cascade Street in 1787. The rebel followers of Silken Thomas in 1534, according to Hollinshed's Chronicles, "cut the pipes of the conduits whereby (the city) should be destitute of fresh water".
In 1721 the Corporation reconstructed and raised the level of the City Basin at St. James Gate. A 250mm lead pipe was laid to James Street from the Basin, and from this three lead pipes of 150mm diameter were laid into the city, with branches distributing water to about ninety streets. This was the final stage of the development of the Poddle supply.
The Balrothery Weir was reconstructed by Andrew Coffey in the early years of the last century, and the present sluice gates and by pass channels date from then. Following Hurricane Charlie in 1986 major repairs were made to the weir, and it is planned to have this historic structure completely restored as a feature of the Dodder Linear Park, which will also incorporate the reach of the city watercourse as far as Spawell.
By 1735 the supply from the Poddle could no longer meet the needs of the growing city. The Corporation acquired the mills and weirs at Islandbridge and constructed a 'powerful water-engine' to deliver water through two 150mm wooden water mains to the north city, and thereby relieve the supply situation south of the Liffey. No details remain of this interesting installation which, together with the City Basin, served a network of one hundred and eighty-five streets for about forty years.
CANAL SUPPLIES
With the completion of the Grand Canal, fed by the Morell River near Straffan and later the waters of the Pollardstown Fen, a new source of supply became available to the Corporation. The canal passed conveniently just to the south of the City Basin, to which water could be admitted by a sluice, as a supplementary supply. Later, as the canal was extended to Ringsend around the south city, a new basin was constructed at Portobello for the south-eastern area of the city. From here a 300mm main was laid in 1880 by Lord Ardilaun, at his own expense, to supply the water features in St. Stephen's Green and this is still in service.
A supply was taken in 1814 to a new basin at Blessington Street to service the north city area. This continued to supply the distillers at Smithfield until they ceased operations some years ago.
This was the era of wooden water mains, which were usually of elm or fir, and specimens of these still survive. In 1809 an Act of Parliament, known as the Metal Mains Act, authorised the Corporation to substitute iron pipes for the old wooden pipes and to levy a rate to pay for this work, which was completed during the following 10 years.
The Canal supplies were necessarily at low pressure due to the elevation of the basins. They gave water at street level, but could not reach the houses in the higher and outlying portions of the city. The concept of internal plumbing was still unknown, and water was simply carried from the street level to the point of use. A water supply continues to be drawn from the Grand Canal, formerly for the various brewers and distillers but now solely for Messrs. Guinness.
THE VARTRY SUPPLY
It had gradually come to be recognised that the water supply from the canals was inadequate and was also unsafe. Indeed, Dublin had been subject to periodic visitations of waterborne disease. A Royal Commissioner, appointed in 1860 to review the state of Dublin's Water Supply concluded that the Vartry was the best, albeit the most expensive source of water for the city. The project was promoted vigorously by the Chairman of the Waterworks committee, Sir John Gray, who has been deservedly honoured by a statue in O'Connell Street. The scheme was an outstanding success.
The Vartry Waterworks comprised an earthen dam 20m high, retaining 11 million cubic metres, slow sand filters and a clear water basin. The water was then conveyed through a 4km long tunnel and then by an 84cm cast-iron main to a large open service reservoir at Stillorgan. This scheme could deliver up to 85,000 cubic metres daily of pure water at high pressure to the city.
The increased supply coincided with the development of internal plumbing systems, water-borne sanitation and the sewering of the city, which brought modern sanitation and water supply to the more prosperous of Dublin citizens.
The system was further developed with the construction of increased storage at Roundwood, the completion of the Gray Reservoir at Stillorgan in 1923 and finally the construction of 4 additional filters at Roundwood in the early 1930's.
THE DODDER SUPPLY
Dissatisfaction in Rathmines with its supply of poor quality water at low pressure from the Grand Canal prompted the Town commissioners to find a better supply. Although Dublin Corporation was anxious to sell surplus water to Rathmines, the Commissioners decided to obtain a supply from the Dublin mountains. A reservoir was constructed at Bohernabreena to receive the relatively clear water from the local catchments, with a by-pass channel for the peat-stained waters of the Dodder River. A second reservoir was constructed to retain river water for release during dry periods, as compensation for the many mills then dependent on water power. The supply was piped to a filter plant at Ballyboden, and thence to the township.
THE POULAPHUCA SUPPLY
The rapid expansion of Dublin in the 1930's increased the demand for water. When the ESB began to harness the Liffey at Poulaphuca the Corporation acquired the right to a supply of 90,000 cubic metres per day, thereby doubling its water resources. The works were completed under the difficult conditions caused by the advent of World War 2. Because of the high colour of the water it was necessary to resort to physico-chemical treatment to clarify and sterilise the water in a treatment plant constructed at Ballymore Eustace. A notable feature of this scheme was the 23km (14 mile) long aqueduct, constructed of cast-in-situ concrete, employed to carry the water to a reservoir at Saggart en route to Dublin. Another innovation in this scheme was the use of bitumen-lined and sheathed steel mains, which are still in excellent condition.
THE NORTH REGIONAL WATER SUPPLY
Dublin County Council had a long-standing ambition to provide piped water for the north County villages and rural area, and to replace the obsolete installations at Swords, Rush, Donabate, Balbriggan and Skerries. Provision was made during the construction of the Leixlip Dam by the ESB for a supply for the reservoir for Dublin County Council. Construction of the treatment works and pumping plant at Leixlip commenced in 1966, and a l0km steel rising main and a 23,000 cubic metres service reservoir was constructed at Ballycoolen.
A basic trunk main and service reservoir system was first provided and the system later developed until virtually every road in the area was covered by the mid-seventies.
WATER TREATMENT
It is usually necessary to subject natural waters to some form of treatment to make them potable i.e. fit to drink and to meet the standards now required by an EC directive. Groundwater is often of very high purity and may only require precautionary sterilisation. Surface waters almost always contain impurities which must be removed by a suitable treatment process. They can be purified by slow passage through a bed of fine sand about 1m deep.
Organisms which grow on the sand surface remove bacteria and viruses, and can give a filtrate of very high quality. The process is attractive because it employs natural agencies, is simple, very reliable and has the attraction that no chemical reagents are employed. Usually it is followed by chlorination as a second line of defence and as a precaution against after-contamination in the mains system. Unfortunately there are few water sources which can meet the directive requirements with this form of treatment, because slow sand filtration is unsuited to waters which are turbid (muddy) and cannot remove colour.
Waters with high colour and/or heavy turbidity can be easily clarified by the addition of coagulants, which cause the impurities to aggregate into floes which can be separated from the water, removing not only the impurities but also the chemicals applied in the treatment process. There are a number of variants of this process related to the design of the separation units. After clarification the water may still contain bacteria and viruses, and must be sterilised, usually by a small dose of chlorine. As stated above, a residue of chlorine must be maintained in the distribution system to counter any accidental after-contamination. Occasionally this trace dose can give rise to complaints about bad tastes in the water
Very heavily contaminated waters may require multi-stage treatment to remove odours and tastes or specific contaminants, such as nitrates or other residues of upstream contamination. These processes may involve the use of ozone for oxidation, activated carbon for absorption of organics, aeration for the removal of iron or sulphur, etc.
The basic elements of water treatment are chemical coagulation - settlement - sand filtration - sterilisation. This system is still widely used but innovative techniques can be employed to treat the water more efficiently. Prominent among these is the use of lamellae plates in the settlement tanks. There are simple sheets of corrugated plastic sloped at 60 degrees which have the effect of increasing the surface area for settlement thus reducing tank sizes.
Adsorption clarifiers are also used in settlement and buoyant granular material traps and removes the coagulated particles. This method too reduces the settlement tank sizes.
Should the water contain trace contaminants or other odour/ taste imparting elements like phenols, pesticides, etc., activated carbon is a useful addition to the water treatment process.
Chlorine in gaseous form has been the standard sterilant for many years and will continue on smaller plants for the foreseeable future. Chlorine gas can be a serious health hazard if not strictly controlled. It is heavier than air and so will not be easily dispersed in the atmosphere. tending to remain at ground level.
However, in the expansion of the Ballymore Eustace Works the sterilant proposed is sodium hypochlorite. This is manufactured on site by passing a mixture of common salt and water (brine) through an electrolyser which converts in solution to sodium hypochlorite and hydrogen gas which is discharged to the atmosphere. This system is called OSEC (On Site Electrolytic Chlorination).
COMBATTING WATER SHORTAGE - SUPPLY AND DEMAND
For at least forty years the water supply of Dublin has been inadequate in some respects. Investment in new works has always tended to lag behind increasing water usage. The distribution system was extended on an ad hoc basis, without corresponding provision for developing the source works and trunk mains. However the basic water resources of the city in the storage reservoirs have always been adequate.
A new emphasis on long-range planning was introduced with the Development Plans required by the Planning Acts. These Development Plans were of enormous assistance in the forward planning of the water supply of the Metropolitan Region. Nevertheless as a result of the explosive rate of development in the 70's, coupled with the long lead-in time for new works, demand constantly outstripped supply, even though the delivery of water doubled over a relatively brief period of years.
Development of the new western towns and redevelopment in the city area increased the projected water requirement to more than double the supply available in 1970. The Liffey was the only existing source capable of yielding this quantity. It was decided to develop the upper Liffey source at Poulaphuca for the needs of the city and the urban area south of the Liffey, while a river abstraction at Leixlip would yield the requirements of Blanchardstown, the north County and the north City. This was the starting point for the many projects undertaken since 1971 to increase the capacity of the source works and to expand the trunk main system. These have been executed in sequence, dictated by the requirement to provide increased supplies where most urgently needed, within the constraint of available finance.
Dublin Water Strategy Study
A major strategic study of the demand for and supply of water in the greater Dublin region began in February 1995. The study is being carried out by consultants and was commissioned by the Department of the Environment with financial support from the European Union Cohesion Fund. This study will examine the present system of water production and supply, the manner in which it meets the various day to day requirements, and make recommendations as to how the system should be improved to provide a higher level of service and meet future demands. The study was completed in early 1996.
HEADWORKS DEVELOPMENTS
Leixlip
The Leixlip works was duplicated in the early seventies and further expanded in 1984/85, to bring the output to 104,000 cubic metres a day.
This plant is now operating at its capacity of 104,000 cubic metres per day. A major upgrading is now in progress to expand the production to 170,000 cubic metres per day. This will provide water for the expanding conurbations of Blanchardstown, Swords and the North City fringe and also for industry in the Leixlip area.
Vartry
Since this source is almost fully exploited, the only development here has been the installation of lime dosing to correct the excessive acidity of this water At the same time modern chlorination, fluoridation and metering equipment has been installed. The filters have been resanded and sand washing facilities have been installed within the last year.
Ballyboden
A modernisation programme to achieve better water quality from the treatment plant was recently completed. No change in output was involved, due to source limitations
Ballymore-Eustace
Waste water from sedimentation and filter washing had been discharged to the Liffey via lagoons of limited retention capacity at Ballymore Eustace. To eliminate this polluting discharge and provide for an increased future output, the first stage of a new sludge treatment plant was commissioned.
The recently completed works at Ballymore-Eustace can produce 230,000 cubic metres per day of high quality potable water. Kildare County Council takes 22,000 cubic metres per day and the rest is used by Dublin Corporation and South Dublin County Council.
There are plans for expansion of the works to a production capacity of 315,000 cubic metres per day.
There are also advanced plans for connecting the Ballymore Eustace supply to the Vartry system at Stillorgan. This entails the laying of a watermain from Ballyboden treatment plant to Stillorgan reservoir. This will ensure security of supply to the south eastern suburbs should the Vartry supply be curtailed for reasons of drought or contamination.
A trunk main from Dorset Street serving the Fairview and Ballymun areas is now complete. This will improve both quantity and pressure in these areas. Further stages of the project will bring watermains out towards Kilbarrack.
Dun Laoghaire/Rathdown County Council are now engaged on a major water works programme. New trunk mains including a tunnel section will be laid from Stillorgan reservoir into the heart of the Dun Laoghaire area. A number of reservoirs will be constructed. This will provide much needed water for the area. Further projects for relaying and rehabilitating old distribution mains are at an advanced stage of planning.
DEVELOPMENT OF THE TRUNK MAIN SYSTEM
With the decision to obtain the bulk of the water needed for the growing urban area from Poulaphuca, a key project was the provision of a new trunk main from the Ballymore-Eustace works to operate in parallel with the existing aqueduct. This second aqueduct was completed in 1981. A new service reservoir at Belgard, Tallaght, provides storage for the new towns of Tallaght and Clondalkin.
There are approximately 2,700 km of watermain serving Dublin City. Of this 40% are over 50 years old and their water tightness is in doubt. Old lead services are prone to leakage and plumbo solvency. Potable water costs money and the less that leaks or is wasted then the more economical and efficient the system becomes. Dublin Corporation is making strenuous efforts to curb water leakage and has a number of proposals for relaying mains throughout the city. In this context, the currently ongoing Dublin Water Strategy Study will examine existing methods of demand management and leakage control to assess their effectiveness and to make recommendations for improvements as necessary. While the Corporation produces and provides water to the tap, the householder is responsible for the internal plumbing out as far as the stop cock. To ensure "unaccounted" water is kept to a minimum both the supplier and the user must exercise care and attention.
FURTHER READING
The Glib Water and Voleman's Brook. Valentine Jackson. Dublin Historical Record. Vol. II, No. 1, 1949-50.
Reports of the Vartry Water. Charles A. Cameron, City Analyst, Dublin, 1868 (City Archives).
A Description of the Dublin Corporation Waterworks. Parke Neville, City Engineer, 1875 (City Archives).
Report on the General State of Public Works in the City of Dublin. Parke Neville, City Engineer, Dublin, 1869.
Report of the City Engineer re Rathmines and Rathgar Waterworks Bill 1880. Dublin Corporation Reports 1880, No. 122.
Report of the City Engineer on relative advantages of Vartry and Canal water for supply of the Township (Rathmines). Dublin Corporation Reports 1877, No. 48.
The Water Supply of Greater Dublin. Michael Moynihan, City Engineer. Proc. Inst. of Municipal and County Engineers 1952.
Recent Developments in the Water Supply to the City of Dublin. G. A. Cremins, Trans. ICEI, Vol. 80, 1954.
Dublin's Water Supply. K. O'Donnell, ICEI, 1987.
The Rivers of Dublin. Clair L. Sweeney, Dublin Corporation, 1991.
A significant portion of this leaflet is based an the text of a Resource Leaflet originally prepared by Kevin O'Donnell and produced by the Department of Environmental Studies, University College Dublin.
