Uisce Éireann is fined after Mayo fish kill

Uisce Éireann has been fined €4000 for its role in a fish kill in a well-known Mayo lake. 

Inland Fisheries Ireland (IFI) brought the case against Uisce Éireann at Castlebar District Court for causing deleterious matter, namely effluent discharge from the Mayfield pumping station, to enter Clare Lake in Claremorris.

David Harrington, Senior Fisheries Environmental Officer at IFI, gave evidence of receiving a report of a fish kill and water pollution at the lake on April 26, 2024, which he said was a high-value public amenity and a popular angling location. There had been a discharge from the pumping station at this location following a spell of heavy rain.

Mr Harrington took three samples from three locations within the lake for further analysis.

The first sample came from near the site of the discharge where the officer observed noxious conditions such as bubbles of gas indicating a lack of oxygen and the growth of sewerage fungus. There were nutrients present that simulated the growth of plant life such as algae but this had a negative impact upon the fish, said Mr Harrington.

Another sample came from a location that again had excessive nutrients and the presence of sewerage fungus and was devoid of aquatic life. The third sample came from further upstream and had clearer water clarity and aquatic life present.

The samples taken near the site of the discharge had elevated levels under the four parameters that Mr Harrington was examining: biological oxygen demand, ammonia, phosphorous and orthophosphate.

The consequence of this was a significant fish kill with 945 fish, such as roach, perch and bream hybrids, recovered by IFI staff over the course of the next two weeks.

Mr Harrington said it was the "worst case scenario" from his view as an environmental officer and it could take between five and ten years for the fish population to recover naturally. He added that IFI is not restocking the lake.

Mr Harrington told the court that Uisce Éireann was fully cooperative with the investigation and has taken mitigating steps. He added that no further fish kill has occurred at this location since, and while angling has been significantly reduced at Clare Lake, it still attracts local fishers on a regular basis.

Solicitor for IFI, Jonathan Moore with Fieldfisher LLP, said that Uisce Éireann has had 15 previous convictions nationally arising from IFI prosecutions under this same act since 2019.

Aoife Sheehan BL, representing Uisce Éireann, said her client took over all wastewater infrastructure in Ireland in 2014 and is actively working to upgrade systems around the country. She said a spell of bad weather put the system at the Mayfield site under pressure.

Ms Sheehan said works had been already underway to address infiltration issues at the pumping station and Uisce Éireann has committed "significant resources" and an expenditure of €1.5 million to address the root cause of the issues at Clare Lake.

Judge Fiona Lydon imposed a fine of €4,000.

In a statement issued after the court case, Uisce Éireann said it is "committed to safeguarding public health and protecting the environment in all our activities". 

"Following an overflow incident in April 2024 which regretfully resulted in a fish kill in the Clare Lake, Claremorris, we put in place a number of measures to reduce overflows at Clare Lake and ensure such an incident does not recur."

Referring to the investment of €1.5 million in infiltration works, the utility company said these included:

• Rehabilitation of 2km of sewer pipelines in Claremorris town to reduce the volume of ground water entering Mayfield pumping station.

• Replacement of foul pumps to increase throughput at Mayfield Pumping Station.

• Improvements to telemetry and monitoring at Mayfield and connection to the INTS (National Telemetry system).

The company added: "In addition, Uisce Éireann also recently completed works to reconstruct a section of sewer near Mayfield where significant ground water infiltration was occurring. Reinstatement works on site will be completed shortly."