Work starts on Saggart water plant as demand for water surges

New reservoir is part of €5.2bn Irish Water plan to secure future supply for Dublin

Mayor of South Dublin County Council Peter Kavanagh, Irish Water’s Stephen Seymour and Deputy Lord Mayor of Dublin Joe Costello prepare to turn the sod on Thursday on the construction of the Saggart reservoir. Photograph: Naoise Culhane

Irish Water turned the sod on works to build a new reservoir for Dublin’s population on Thursday – part of a plan to spend €5.2 billion to secure drinking water supplies for the years ahead.

Saggart, which will hold 100 million litres of water supplied from Irish Water’s Ballymore Eustace water treatment plant – equal to 40 Olympic-sized swimming pools – will be ready in three years’ time. It cannot come too soon.

Earlier rains during the year mean that water supplies in Dublin and the wider eastern region are not currently at critical levels; nevertheless, average daily demand is within 6 per cent of what the water utility can supply.

Such margins leave the wider Dublin region vulnerable to demand surges such as heatwaves. In 2019, the average daily demand for water in the Greater Dublin Area, the last normal year before the pandemic, was 572 million litres a day.


However, Irish Water’s current “sustainable operational capacity” is limited to 610 litres per day, leaving just approximately 40 million litres per day (6 per cent of total supply) on average, as a buffer .

Sometimes, the margin falls to just 15 million litres per day, it said. When that happens, the buffer between having enough water and restricting supply is just 2.5 per cent of total supply.

“ This leaves us limited capacity to deal with any issues, such as a burst main on the network or the requirement to reduce capacity at a plant for maintenance works,” said a spokesman.


The vulnerabilities were illustrated recently when Greater Dublin Area demand rose from 535 million litres on Sunday July 11th to 595 million litres on Tuesday July 20th – equal to the average daily consumption of more than 450,000 people.

The supply problems facing Irish Water are compounded by a race to replace a literally crumbling network, some of which is up to 150 years old, dating back to Victorian times.

Irish Water provides 1.7 billion litres of drinking water every day to homes and businesses all around Ireland, but up to 40 per cent of that disappears because of leaks.

On Thursday the Irish Water website listed some 83 burst water mains in various states of being repaired. Some of the larger cement and asbestos water mains date from the 1950s and, in dry weather, when the ground shifts, these rigid pipes tend to break at the joints. The website also listed other “repairs” to 30 more major water pipes, alongside dozens more “essential”, “conservation” or “rehabilitation” works. In addition, some 45 drinking water treatment plants were this year named by the Environmental Protection Agency (EPA), including the Leixlip plant that failed in 2019. Leixlip was added to the action list after two “boil water” notices to householders had to be issued, highlighting deficiencies in the treatment works at the plant.


So far, filters in the plant have been upgraded and UV disinfection units were installed by March of this year, while the final chapter of the remedial works – known as “pH correction” – should be done by late 2023.

An EPA audit in March of this year on the Vartry reservoir in Co Wicklow, which supplies drinking water to 200,000 people in south Dublin and north Wicklow, raised concerns about the 150-year-old reservoir.

The audit was carried out in response to a significant increase in the number of detections of the germ giardia, a tiny parasite that causes the diarrhoeal disease giardiasis.

The audit noted, however, that the treatment plant at the Wicklow reservoir is “at the end of its life” and a new treatment plant built alongside it is due to open this year.

The €5.2 billion that will be spent on capital investment by Irish Water between 2020 and 2034 will secure the needs of its customers, the utility told The Irish Times.

Tim O'Brien

Tim O'Brien

Tim O'Brien is an Irish Times journalist