Several alarms at the Leixlip Water plant “were not responded to”, leading to the country's largest-ever boil water notice last month, TDs will be told tomorrow.
It comes as a boil water notice was re-issued as a precaution for consumers who rely on the Leixlip Water Treatment Plant because of heavy rain.
The Oireachtas Housing Committee will tomorrow hear evidence from Irish Water, the Environmental Protection Agency (EPA) and Fingal County Council as to how the catastrophic failure first occurred last month.
Despite the incident occurring the day before, Irish Water was only first notified of the incident at the old plant by Fingal County Council at 9.45am on Tuesday, October 22.
The water utility immediately contacted the HSE and EPA.
Irish Water will say that on Monday, October 21, a mechanical failure occurred on a piece of equipment at the old plant at Leixlip.
In evidence, Niall Gleeson Managing Director of Irish Water will say that at 3.15pm a blockage occurred in a chemical delivery line leading to a failure of a pressure release valve. No pump alarm activated as the failure point was downstream of the pumps.
At 5pm turbidity levels in filtered water started to increase as a result of the delivery line failure.
Turbidity is cloudiness in water due to suspended particles.
At 6.16pm increasing turbidity in filtered water triggered an on-site alarm and sent an SMS text alert.
“The alarm was not responded to and turbidity continued to rise," the Committee will hear.
At 7.07pm an on-site high turbidity alarm was activated on the clarified water.
“The alarm was not responded to and turbidity continued to rise”, Mr Gleeson will say.
Then at 9.15pm an off-site plant manager who had logged-on remotely to the Leixlip plant noticed the activation of turbidity alarms and the lack of response on site.
The alarm was investigated and a contractor was called to clear the pipe blockage and carry out a temporary repair to the pressure release valve, the Irish Water boss will say.
From 10.15pm to 11.30pm the repair was completed.
A decision was taken to temporarily shut down the old plant to allow the treatment process to stabilise.
Between 11.30pm and 5am on Tuesday October 22, the old plant was gradually brought back into operation.
The automatic plant shut off did not happen when the alarms were not responded to as this facility was not yet in place at the old plant.
Mr Gleeson will also acknowledge shortcomings in Irish Water's communications strategy, particularly difficulties members of the public had in accessing its website.
In its statement, the EPA's Dr Tom Ryan will say the elevated turbidity levels in treated water indicated a significant risk to the safety of the water supply because of the treatment barrier for removal of Cryptosporidium and Giardia was compromised, and there was a risk of breakthrough of microscopic parasites into the water supply.
Due to heavy rain, turbidity (cloudy water due to suspended particles) in the source water for the old Leixlip Plant exceeded acceptable levels. Plant operators reacted quickly before alarms were activated and shut down the old plant to stop this water entering the network.— Irish Water (@IrishWater) November 4, 2019
This evening, Irish Water said following consultation with the HSE, Irish Water and Fingal County Council, a Boil Water Notice to protect the health of customers supplied by Leixlip Water Treatment Plant has been put in place for a second time.
The utility said that due to heavy rain, turbidity in the source water for the old Leixlip Plant exceeded acceptable levels and that plant operators reacted quickly before alarms were activated and shut down the old plant to stop this water entering the network.
Eamon Gallen, Irish Water’s General Manager said: "We are very disappointed that a Boil Water Notice has to be imposed again but as we outlined the last time, our number one priority is the public health and the safety and well-being of our customers."
The Boil Water Notice impacts the same areas as previously; parts of Fingal, areas in Dublin City Council, parts of South Dublin County Council, parts of Kildare and Dunboyne in Meath.
Housing Committee chairman Noel Rock told the Irish Examiner: “600,000 people are being hit again by this, and its naturally causing stress and disturbance for people.
"Those 600,000 people deserve answers and I intend to ask the questions that will get them when Irish Water appear at my invitation before our Committee tomorrow."