Project Outline

Murphy Ireland have completed the Design, Build and Operate contract of the Stillorgan Reservoir Upgrade Project on behalf of Irish Water, replacing the existing open reservoirs, with a new covered reservoir. More than 200,000 Dubliners are benefiting from a safer and more secure water supply following commissioning of the new Stillorgan reservoir in September 2021.

The Stillorgan Reservoir site has a total plan area of approximately 16 hectares and was subdivided into three discrete water storage reservoirs, the Gray, Upper and Lower Reservoirs.  The Lower and Upper reservoirs were constructed first, as part of the Vartry Water Supply Scheme. The Gray Reservoir was built in 1885 following a period of severe water shortage in Dublin City.

The reservoirs originally contained water from the Vartry Supply Scheme alone; however, following construction of the Liffey Supply Scheme at Ballymore Eustace in the 1940s, a 24” main was laid between Saggart Reservoir and Stillorgan Reservoir to link the two supplies. An additional 1000mm diameter trunk main linking the supplies was constructed on a phased basis during the 1990s.

The Stillorgan Reservoir project removed the open storage that was in operation and replace it with a covered reservoir of 160ML storage capacity. This will ensure a long-term, secure and sustainable water supply to the region, meeting current and future regulatory requirements.

Scope of Works
  • Draindown of Gray reservoir
  • New 160 ML covered storage reservoir , consisting of three cells and internal baffle walls, constructed within footprint of the old Gray reservoir;
  • Manifold building (ca. 2,900 m2 area) for rationalisation of incoming pipework
  • Replacement of incoming & outgoing pipework (ca. 3 km length varying diameter 600 mm – 1600 mm)
  • New site entrance off St. Raphaela’s Road
  • On-Site-Electrolytic-Chlorination (OSEC) plant for secondary disinfection dosing at Stillorgan
  • Decommissioning Upper and Lower reservoirs following commissioning of new reservoir and disinfection dosing;
  • Internal road network;
  • Site drainage;
  • Site services;
  • Site Landscaping;
  • Operation of new reservoir and OSEC plant for a period of 3 months
Key Challenges

Community and Stakeholder Management – As project is located in an urban setting community management was key to the success of the job. Murphy’s project manager liaised directly with local residence to ensure their concerns were addressed and closed out efficiently. Murphy’s site team were able to accommodate and work with the residents through the project to try and minimise disturbance. This included moving work locations for short term periods if a particular resident had an exam or important meeting that they were attending at home.

Protecting Existing Water Infrastructure & Water Quality - Murphy were responsible for ensuring none of the works cause water quality issues during construction. This included protecting the Upper & Lower reservoirs, existing pipework and network. Throughout the construction period, no water quality issues arose because of the works. This was a major project success as the site conditions involved heavy civils work including rock breaking very hard granite rock with large machines (45ton excavators) in very close proximity to the existing reservoir embankments, cast iron pipework and existing Valve House. The existing Valve House chamber was an operational treatment plant that treated the water with UV light using UV bulbs which are particularly sensitive.

Project Commissioning – The commissioning of the Stillorgan reservoir upgrade proved to be a very efficient and successful process.  The Murphy & Nicholas O’Dwyer site teams worked hard in the months and years leading up to commissioning to ensure stakeholder engagement was successfully achieved. Bi-weekly meetings between the site team, Dublin City Council and Irish Water were organised to discuss in detail the commissioning works. This included the best possible sequence for connecting the new facility to the existing network to ensure water quality was never compromised. Murphy’s experience in commissioning plants of this nature was used to good effect with the plant operating as planned from day one of commissioning.

Project Programme - This project was delivered to schedule, despite huge external challenges posed by Covid-19 and Brexit, which we believe represents a major success, considering the scale of the project and those unprecedented external factors which effected everything from material & labour shortages, longer delivery lead times, slower production rates, etc.

Project Delivery & Innovations

The project aimed to deliver the 160ML reservoir, using the most environmentally sustainable and innovative construction techniques possible, while remaining at all times economical. Innovation included;

Baffle Walls: A significant innovative design step included replacing the concrete baffle walls within the cells of the new reservoir with geotextile curtains. Providing the same operational value with less construction time and at lower cost, these curtains represent a more sustainable solution.

Pipework:  The optimisation of pipework design ensured that there was no wastage or needless runs of pipe. Steel pipes were used ahead of the more commonly used ductile iron pipework for more versatility and more certainty when testing due to its welded joints. Murphy used our in-house expertise with installing large diameter welded pipelines.

Precast Columns & Roof: Pre-cast concrete was utilised to construct the roof over the reservoir cells. This method delivered a large saving on time.

Materials, labour and plant included:

  • 2,500 tonnes of steel reinforcement
  • Over 24,000m3 of concrete
  • Steel pipework for inlet and outlet water mains;
    • 1,029m of Ø600mm
    • 253m of Ø800mm
    • 491m of Ø1000mm
    • 679m of Ø1200mm
    • 542m of Ø1600mm
  • At its peak the project had over 100 operatives at any one time
  • Plant include 3+ crawler cranes working at any one time
  • Concrete base slab pours consisted of 18nr base pours with an average of 626m3 per pour. The largest base pour was 883m3.

More than 200,000 Dubliners have benefited from a safer and more secure water supply following completion of the new Stillorgan reservoir by Irish Water. The original reservoir in south Co Dublin – the largest treated water reservoir in the country – had supplied drinking water to the surrounding area for over 150 years. It was one of the last remaining uncovered treated water reservoirs in Europe.

John Prendeville, project manager with Irish Water, said it was a €50 million investment in providing a long-term solution “to safeguard this strategically important part of Dublin’s water supply for the future”.

It was delivered on time and to budget, Mr Prendeville said, through “a hugely collaborative effort between Irish Water, Dublin City Council, Nicholas O’Dwyer Ltd, Murphy International Ltd and of course, the local community, whose co-operation and patience have allowed these works to succeed.”


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