Water tests are being carried out at eight Dublin beaches after an overflow at the Ringsend treatment plant sent sewerage flowing into Dublin Bay.
A week-long swimming ban was issued for all beaches in the Dún Laoghaire-Rathdown area yesterday after the overflow was announced.
It affects a number of popular swimming spots including Seapoint, Killiney, Sandycove and the Forty Foot.
Experts say it will be Monday before the results will show whether or not the water quality has returned to safe levels.
Irish Water has blamed the overflow at the Ringsend plant on this week’s heavy rains.
It said the plant "operated as designed" insisting that is not possible to “build a plant that can cope with every single rainfall event that ever occurs” and said the planned upgrades will make overflow events “far less regular.”
The utility said the scale of the leak is almost unprecedented and has insisted it is planning €400m worth of upgrades to prevent it happening at the plant in future.
It said there is no long-term risk to the public – with the sewerage being steadily removed by the tides.
We have been made aware of a sewerage wastewater overflow at the Irish Water operated Ringsend wastewater treatment plant during the recent yellow weather warning.
This means that there is no swimming at all our beaches for the next 7 days. Read more: https://t.co/jefknjza4z pic.twitter.com/xziODa9kAR
— Dún Laoghaire-Rathdown County Council (@dlrcc) June 6, 2019
Damien Cassidy, chair of the Ringsend, Irishtown and Sandymount Environmental Group, said the plant has been causing trouble for years.
“It is a horror story,” he said. “Nothing short of that.”
“We always worried that the entire bay would be compromised by this plant – we were not wrong.
“We have been fighting it since 1993. I haven’t been able to have a swim there for the last 20 years.
“We want our facilities back the way they were.”
A number of beaches in the north of the city have also put temporary bathing bans in place.
These locals at Dollymount Strand said Irish facilities should be built to handle Irish rain.
“It is like the floods in winter,” said one resident. “You would imagine at this stage that we know the Irish weather; we know a deluge is possible any day of the week.
“We should have systems in place to deal with that.”