Irish Water – Cork Harbour

The Cork Lower Harbour Main Drainage Project was carried out on behalf of the client Irish Water, and aims to provide enhanced wastewater treatment through the development of new wastewater treatment infrastructure which will service the areas of Cobh, Carrigaline, Crosshaven, Passage West/Monkstown and Ringaskiddy

In 2015, the equivalent of 40,000 wheelie bins of raw sewage was discharged into Cork harbour every day. This figure was substantially reduced through the construction of a new wastewater treatment plant, and this will further reduce upon completion of all works associated with this main drainage project.

The purpose of the overall project was to improve the quality of the environment for receiving waters and terrestrial areas in the project catchment, by providing a sewage collection network which complies with the requirements and standards of the Urban Wastewater Treatment Directive, the EU Water Framework Directive.

The overall project was split into separate individual contracts, which in summary consists of:

• A new Wastewater Treatment Plant (WwTP)
• 15 new pumping stations
• Upgrading of 4 existing pumping stations
• Approximately 30km of new sewers
• HDD Estuary Crossing

Scope of Works

The works required to deliver the contract can be summarised as:

• The detailed design, procurement, construction, testing and commissioning of:
• 2 no. 500mm OD SDR9 estuary crossing pipelines approximately 1,100m long each installed under the River Lee estuary between Cobh (Cork Dockyard) and Monkstown using HDD methods
• 2 no. 500mm OD SDR 17 rising main pipelines
• A discharge chamber to facilitate connection to the existing sewer network
• Utility diversions (Glen Road, Monkstown) to divert all existing OHL’s into a fully ducted underground system

Estuary Crossing

The estuary crossing pipeline comprises 2 no. 500mm OD rising main pipelines capable of transferring 426 l/s.

The two estuary crossing pipelines, each approximately 1010m long, are installed within two Horizontal Directionally Drilled bores under the River Lee estuary, from the Launch Site in Cork Dockyard to the drill exit point in the Reception Site at Glen Road, Monkstown.

To facilitate the HDD element of the works, we controlled 2 separate work fronts, separated by the estuary crossing, as illustrated above.

The HDD Entry point was located within an industrial area with ample room, so the project office compound was set up in this area which consisted of full welfare and office set up for the OCU and Client project teams, plus an additional separate office and welfare set-up for the HDD site team.