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Successful completion of Ireland's longest-ever underwater directional drill marks major milestone in Cork Lower Harbour project

Cork Lower Harbour project completes installation of two pipes underneath Lee estuary- the longest such directional drills in Ireland.

Uisce Éireann, in partnership with Cork County Council, is working to end the decades-long practice of discharging raw sewage directly into Cork Lower Harbour with the Cork Lower Harbour Main Drainage Project.  

Uisce Éireann this week completed the installation of the sewer pipe in the second and final drilled bore extending for over 1km under the Lee Estuary between Cobh and Monkstown. This landmark engineering feat includes two of the longest such horizontal directional drills ever carried out in Ireland.

What is involved?

This successful installation completes the works under the estuary as part of the Cork Lower Harbour Project, creating the vital connection between Cobh and Monkstown. This connection will allow the raw sewage from Cobh town to be transferred for treatment, once work on the Cobh Town Networks contract are complete in 2021.  

Déaglán Healy, Project Manager for Cork Lower Harbour Main Drainage Project, said "We are delighted to have successfully and safely completed the drill and pipe installation works for this contract.  These works could not have been completed without the patience and cooperation of the local community, particularly in the challenging times we currently find ourselves in."

"We'd like to thank them for working with our contractor for the works, O'Connor Utilities, who have worked tirelessly, in partnership with Long O'Donnell, Nicholas O'Dwyer and our own Uisce Éireann Project team, to ensure the safe completion of these works while minimising the impact on the local community as much as possible. They will now put these efforts into returning Monkstown Park to the community."

What are the next steps?

Works to connect the sewer pipes under the estuary to the network on the Monkstown side is continuing on Glen Road and the reinstatement of Monkstown Park and basketball court will commence in the coming weeks. It is expected that these works will be completed in the Summer. 

Work is also progressing well on the Cobh Sewer Networks, with approximately 2.4 kilometres of the total seven kilometres of sewer pipes laid to date as well as work started on the construction of two of the five pumping stations. When works in Cobh are complete in 2021, the raw sewage from Cobh town will be collected and transferred for treatment via the Cobh to Monkstown Estuary Crossing to Monkstown pumping station, from where it will be pumped to Shanbally Wastewater Treatment Plant for treatment before its safe discharge to the harbour. 

Information on all these works is available from our project team at and on our Cork Lower Harbour project page.

Why is this needed?

When construction on the Cork Lower Harbour Main Drainage Project commenced in 2015, the equivalent of 40,000 wheelie bins of raw sewage was discharging into the Harbour every day. We are now treating the equivalent of 30,000 of those 40,000 wheelie bins by completing the Shanbally Wastewater Treatment Plant and pipelines and pumping stations on the south side of the harbour so that wastewater from Ringaskiddy, Crosshaven, Carrigaline, Passage West and Monkstown is now being treated.

When all the Cork Lower Harbour Main Drainage works are complete in 2021, the project will, in compliance with the Urban Waste Water Treatment Directive, treat all wastewater from the agglomerations of:

  • Ringaskiddy-Crosshaven-Carrigaline
  • Ringaskiddy village
  • Passage West-Monkstown
  • Cobh town

This means 20,000 homes and businesses will be connected to the new scheme and that raw sewage from these areas will no longer be discharged into the harbour, positively impacting the local economy and greatly improving the amenity value of the Cork Lower Harbour for the surrounding communities.

Uisce Éireann is working at this time, with our local authority partners, contractors and others to ensure that the safety and well-being of all staff is safeguarded and to ensure the continuity of supply of public drinking water and wastewater services.

More information

For more information on the project, information days and works information please contact the project team at or see our project page on our website at Cork Lower Harbour.