The offence related to a poor quality discharge from a wastewater treatment plant at Ardee, Co Louth.
The River Dee rises near Bailieboro in Co Cavan and flows through Co Meath and Co Louth, where it enters the Irish Sea at the village of Annagassan.
Michaela Kirrane, senior fisheries environmental officer with Inland Fisheries Ireland (IFI), told Judge Coughlan that during a routine inspection of the river on the 25 May last year, it was noted that the river appeared to be in a poor condition downstream of the discharge point from Ardee Wastewater Treatment Plant.
A series of water samples were taken and analysis confirmed that the discharge from the treatment plant was having a deleterious impact on the quality of the River Dee, an important brown trout fishery.
Irish Water co-operated fully with IFI’s investigation and remediation works were carried out. Upgrade works are currently underway to increase capacity at the wastewater treatment plant.
Irish Water was fined €4,500 with costs and expenses awarded to IFI amounting to €4,381.61.