About this project


Irish Water is progressing with works on the construction of a new covered storage reservoir as part of the Stillorgan Reservoir Upgrade. This is a priority project for Irish Water and necessary to ensure a secure and sustainable supply of water to over 200,000 people in south Dublin.  After almost 150 years serving the community, the Stillorgan Reservoir will be modernised to adequately meet current requirements and the needs of future generations.

Irish Water has already invested €3.4 million in a new system to improve the disinfection of drinking water stored in the Stillorgan Reservoir.  Following this investment, the environmental Protection Agency (EPA) removed the Stillorgan Reservoir from the Remedial Action List (RAL).  The long term solution to upgrade the reservoir is now being progressed. 

What is happening now?

Construction on the new covered Stillogran Reservoir commenced in November 2018 following An Bord Pleanála approval of the planning application to ensure Irish Water will retain the entire site for this future development.

The new covered reservoir is now structurally complete, with testing and landscaping ongoing, it will be operational in the third quarter (Q3) of 2021.

Work on the construction of new covered reservoir at Stillorgan (August 2020)
Stillorgan, Co. Dublin
In Progress
Not Applicable
Stillorgan Reservoir

Project background

The reservoir was originally constructed as part of the Vartry Water Supply Scheme which also includes two impounding reservoirs at Roundwood, County Wicklow, a water treatment plant, a four kilometre long tunnel under Callowhill and 40 kilometres of trunk mains to deliver water to the Stillorgan Reservoir. The reservoir has also been supplied from the water treatment plant at Ballymore Eustace in County Kildare since the 1950’s.

The Vartry Scheme commenced construction in the 1860s and was an amazing feat of engineering at the time. This work was particularly important as it helped to greatly improve living conditions and public health in Dublin city. It improved sanitation and helped reduce outbreaks of cholera, typhus and other diseases associated with contaminated water.
It is a testament to the success of the project that the reservoir still provides drinking water to around 15% of the Greater Dublin Area.

What will this project involve?

The Stillorgan Reservoir Upgrade Project includes:

  • Draining the Gray Reservoir and constructing a new covered reservoir and control building.
  • Once the new covered reservoir is operational the Upper and Lower Reservoirs will be drained and decommissioned. The decommissioned areas will be reserved for future water services facilities.
  • Landscaping the decommissioned reservoir areas in accordance with a landscape masterplan.
  • Pipeline modifications within the reservoir site.

Construction commenced in November 2018. The new covered reservoir is now structurally complete, with testing and landscaping ongoing, it will be operational in the third quarter (Q3) of 2021.

Once the new covered storage is fully commissioned, the existing Upper and Lower Reservoirs will be decommissioned and the site will be landscaped. It is expected that this will take approximately twelve months.

The site will remain an active water supply site and contains high pressure pipes and valves. As a consequence the use of the site for publicly accessible open space is not feasible.

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