Raw sewage has been discharged into the Irish Sea for up to 26 hours because a malfunction went unnoticed at a treatment plant.
A member of the public on Balbriggan Beach in north Dublin raised the alarm on Tuesday afternoon when the waste water was washed back in with the tide.
Fingal County Council has closed the beach to swimmers and is awaiting results of water-quality samples from Balbriggan and nearby Barnageera and Skerries, which are due tomorrow.
“It is not possible to accurately measure the exact overflow volume discharged during the outages,” said a council spokeswoman. “We are treating this incident very seriously.”
Council chiefs said Isaac’s Bower pumping station in Balbriggan was out of action for 26 hours after extensive power interruptions in the area on Monday on Tuesday.
An automatic warning alarm was not activated as the power cuts also caused an item of the electrical control equipment to fail.
When the treatment plant filled with sewage it overflowed into the normal water drainage system and was then discharged into the sea, the council spokeswoman said.
“During this time there was extensive heavy rain in the area, adding to the volume of water being carried in our drainage network and the consequent overflow volume coming from the pumping station,” she said.
“This is what caused the sewage overflow on Balbriggan Beach yesterday afternoon.”
Visual inspections were carried out at Balbriggan, Barnageera and Skerries beaches on Tuesday.
“The initial effect of the overflow in Balbriggan is that the beach must remain closed to bathers until any clean-up is complete and water quality at the beach meets the European bathing water quality standard,” she said.
“Should any breach of water-quality standards happen at beaches other than Balbriggan, the public will be notified immediately.”
A major clean-up is due to get under way, which could involve removing sludge or any other material accumulated at the shoreline.
Fingal said waste overflowed from Isaac’s Bower again for half an hour in the early hours of this morning, blaming heavy rainfall, but that pumps carried the majority of wastewater to Barnageera for treatment.
Another overflow was reported for 40 minutes this morning.
“This was caused by a blockage of the pumps as a result of yesterdays pumping problems,” the council spokeswoman said. “The overflow has now stopped and the contractor is on site today repairing the pumps.”
Elsewhere, Rush Road pumping station in Skerries was also out for almost two hours on Tuesday morning but the warning alarm was activated.
Aecom operates and maintains Barnageeragh wastewater treatment plant and the Isaac’s Bower station on behalf of the council.
In a statement on its website, the Council said: "We apologise to citizens and in particular to users of the beach/bathing waters for the inconvenience caused."
Separately, Professor Fiona Regan called for increased water quality monitoring to avoid marine pollution such as that which was recently experienced in the seas off Cork and Galway, where beaches were also closed to swimmers.
The DCU academic said low-cost monitoring devices are needed.
“Devices should be deployed all around the country and we should monitor the quality of our water continuously, so that we can be informed in real-time when events like that in Cork happen,” she said.
“We don’t need sophisticated sensors everywhere, we just need the information at the right time.”
Brian Hosford, chairman of Reclaim Fingal Alliance which is campaigning against a giant sewage plant in the area, said the malfunction highlights problems with unreliable technology.
“If a monster sewage plant were built and a disaster like this happened, the consequences for the entire east coast would be catastrophic,” he said.
“While this may be manageable within a few days, a spill from a monster sewage plant has the ability to destroy the economy of Fingal, as well as its leisure and tourism sectors.”
Fingal County Council said larger plants, like the one proposed for the Greater Dublin Drainage project, have a significantly higher level of engineering resilience built into them given the much higher volume of wastewater they treat.