COMPLAINTS from locals about a stench in the air resulted in city chiefs admitting to another problem at Ringsend sewage treatment plant.
A member of the public contacted the Environmental Protection Agency (EPA) about the latest difficulty and they got on to Dublin City Council.
It came after a stink was noticed by householders in the Sandymount, Ringsend and Irishtown area, leading to a series of complaints.
The €300m wastewater treatment facility had been beset by odour problems in earlier years but significant upgrades seemed to have solved the problem.
The council told the Herald it carried out an investigation after being contacted by the EPA last week.
"The council investigation of the matter found that the flow of wastewater was temporarily diverted to storm tanks to rectify a maintenance issue," a spokesman said.
"This is a normal routine maintenance procedure and should not have given rise to any odour issues beyond the site boundary," he insisted.
"The matter was rectified in a matter of hours and the diverted wastewater was returned to the works for full treatment. There was no discharge of wastewater to the river," the spokesman said.
The council apologised for any inconvenience caused.
However, environmental activist Damien Cassidy told the Herald the stink in the area was "toxic" last Thursday when the "break down" occurred.
He added it was not the only day that there was a problem.
Mr Cassidy received several complaints about the smell.
The plant opened in July 2003 to process sewage from 1.7m homes around Dublin, bringing an end to the dumping of 40 million gallons of raw sewage into Dublin Bay.
It was developed in a public-private partnership with ABA consortium, involving Ascon, sewerage specialists Black & Veatch and Anglian Water.
In the early years of its operation, residents living in the Ringsend, Sandymount and Irishtown areas experienced foul smells from the plant, but significant odour alleviation measures were undertaken.
The smell was particularly bad in summer and residents had been forced to keep their doors and windows shut.