Irish Water been cleared by the state’s independent planning agency, An Bord Pleanála, to proceed with a €200m upgrade of the 150-year-old water treatment plant at the Vartry reservoir in Co Wicklow.
Water treated at Vartry supplies more than 200,000 people in north Wicklow and south Dublin, but has had no significant upgrade since it was built in the 1860s.
The Environmental Protection Agency had identified the plant as at risk of failing to meet national drinking water standards, particularly in the case of treatment against both cryptosporidium and trihalomethanes.
The upgrade project was approved by Wicklow County Council in 2016 but fishery interests appealed that decision to the agency because of concern over the impact of the scheme on the local river.
As part of the project, Irish Water has committed to significant measures to protect the ecology of the River Vartry, particularly during drought periods.