Construction of a new 100 million litre reservoir, to secure water supplies across Dublin city and south Co Dublin, will begin next month, Irish Water has said.

The equivalent of 40 Olympic-sized swimming pools of treated drinking water, from the Ballymore Eustace water treatment plant, will be stored in the new covered reservoir at the existing reservoir site in Saggart.

The upgrade marks the first significant investment in the existing Saggart waterworks since it was built in the 1950s. The project will see the current waterworks replaced with a new reservoir that will provide treated drinking water to help to safeguard the water supply to homes and businesses in the greater Dublin area (GDA), Brian Sheehan, head of asset delivery with Irish Water, said.

“This particular project will provide strategic treated water storage capability at Saggart which is needed to support the building of houses and schools; to attract new industry and to allow companies to expand and grow across the GDA.”

The project was part of a “ multi-billion programme of investment” to improve water infrastructure, he said.

“In terms of size and scale, the new reservoir can store enough water to supply almost 300,000 homes with the water they need for one day. It is one of a portfolio of water projects that we are delivering to safeguard the water supply to homes and businesses.”

Minister for Housing and Local Government Darragh O’Brien said Irish Water was working with Dublin City Council and South Dublin County Council to deliver the new facility.

“The delivery of this project will support existing and future residential and commercial development in the greater Dublin area and is one of a portfolio of water projects being delivered by Irish Water.”

The construction of the facility, by Coffey Construction Ireland Ltd, is expected to be completed within three years.