The EPA "remains concerned about the ability of Leixlip water treatment plant to maintain and sustain an appropriate level of performance", according to the latest audit of the facility published on Thursday.
The audit was conducted last week after a boil water notice was issued to 600,000 people in the greater Dublin area, including parts of Kildare and Meath, who receive their supply from the plant which extracts water from the river Liffey.
The notice imposed on November 4th, less than a fortnight after an earlier boil water notice was lifted, was blamed on heavy rain and cloudy water – known as “turbidity” – due to suspended particles in the source water which exceeded acceptable levels in the “old plant”.
“Until such time as the [water] filter upgrade works are complete, there is a risk of reoccurrence of this type of event where high turbidity levels in the raw water for a sustained period lead to operational difficulties at the old plant,” the EPA auditors found.
Their findings have been forwarded to Irish Water and Fingal County Council, which runs the plant on behalf of the utility.
They added: “Irish Water must notify the EPA and the HSE if the plant does not meet the level of performance required to provide adequate treatment to ensure safe water, which may necessitate Irish Water issuing further boil water notices in future, to protect consumers’ health.”
Reduced headroom
While the move by Irish Water to supplement the Leixlip supply with water produced at Ballymore Eustace water treatment plant was a welcome measure to allow for the acceleration of filter upgrade works at Leixlip, "it also means the available headroom for water supply to the greater Dublin area is reduced until these upgrade works have been completed," they noted – headroom refers to sufficient water to cater for current and future uncertainties in a supply area.
The EPA team also criticised the poor condition of clarifiers used to clear the water of solid materials; “the clarification process is not operating optimally and will reduce the effectiveness of the filter upgrades”. Accordingly, it recommends that damaged plates be replaced.
The report said Irish Water “should undertake daily monitoring of parasites cryptosporidium and giardia in the treated water until the filter upgrade works are complete”. If any oocysts or cysts, indicating the presence of the bugs, are detected during the monitoring programme, Irish Water “should immediately notify the HSE and EPA”.
The report confirms, however, the auditors were satisfied the “high turbidity event” which began on Sunday November 3rd, 2019, ended on Wednesday afternoon November 6th when turbidity levels returned to normal.
“The treatment plant appears to have been operating satisfactorily since then, with ongoing testing to verify that the treatment barriers at the plant are fully effective,” they added.
Vulnerable
The EPA also advised the findings and recommendations from this audit report should, where relevant, be addressed at all other treatment plants operated and managed by Irish Water.
Irish Water managing director Niall Gleeson acknowledged earlier this week that "the old plant at Leixlip remains vulnerable and Irish Water working with Fingal County Council will be working to minimise the risk of another boil water notice".
“If we could, we would shut down the old plant, take it off line and do all the refurbishment at once. This is not possible because 20 per cent of Dublin’s water supply comes from the old plant and we do not have the spare capacity to allow this to happen. We will continue to monitor the plant closely,” he added.
“The EPA will continue to work with Irish Water and will assess the situation further on receipt of Irish Water’s response to the EPA’s audit report on the October incident, which is due on November 30th,” an EPA spokeswoman confirmed .
The recommendations from the previous audit on October 24th remain to be addressed by Irish Water, the latest audit noted.
