Reservoir to be covered amid fears it could be a target of terrorist attack
Water accessed by 200,000 people living across south Dublin is at risk of contamination.
Irish Water is planning a €80m upgrade of the 150-year old Stillorgan Reservoir amid concerns that treated drinking water could be at risk of contamination from terrorists, wildlife, or vandalism.
The utility plans to build a covered reservoir that can store 160 million litres, which is around two days' supply.
Works will take up to two years to complete and will involve building three water storage cells in a flat-roofed building measuring 275 metres by 174 metres.
A control and treatment building will also be developed.
The company will today launch a six-week public consultation on the proposed new covered reservoir, prior to submitting a planning application to Dun Laoghaire-Rathdown County Council.
A similar project was given permission in 2002.
Irish Water said the covered reservoir was "essential" to safeguard the quality of the drinking water.
"Irish Water has already invested €3.4m in a new system to improve the disinfection of drinking water stored in the Stillorgan Reservoir," it said.
"Following this investment ... the long-term solution to upgrade the reservoir is now being progressed."
Submissions can be made up to September 14.
The Stillorgan Reservoir holds drinking water treated at Vartry before it is distributed across south Dublin.
It is considered "critical" to the continued supply and quality of water in the region, and the development is supported by the Environmental Protection Agency (EPA) and HSE.
It is one of only two uncovered reservoirs in the State, and the other one at Ballyboden will be replaced in 2017.
Head of major projects at Irish Water Geoff O'Sullivan said safeguarding the quality of drinking water was a "top priority" for the company.
"We have committed to investing €80m to ensure the upgrade to the reservoir provides the long-term solution that is required to secure the water supply," he said.
"This is part of a national investment plan that is being implemented on the basis of greatest need under our 25-year strategy, the Water Services Strategic Plan."
The EPA said for some time it had called for the reservoir to be covered.
"The open storage of treated water places the supply at direct risk of environmental (eg microbiological pollution from wildlife) or deliberate contamination (eg from unauthorised access, vandalism or terrorism)," it said.
"Previous EPA audits have found evidence of unauthorised access to the reservoir which puts the supply at risk.
"The EPA has been calling for the covering or replacement of the Stillorgan Reservoir at the earliest opportunity to address these concerns," the agency has said.