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Marine Notice: Cable Lay and Post-Lay Operations Off South East Coast for Celtic Interconnector Project

30th July 2025
Celtic Interconnector

The Department of Transport has been advised by Nexans that Van Oord will be performing cable laying activities on its behalf for the Celtic Interconnector Designated Activity Company (CIDAC) as part of the Celtic Interconnector undersea cable project.

Vessels working on the project will arrive in the area on Friday 1 August, subject to operational and weather constraints.

The cable will be formed of a bundle of two cables and one fibre optic cable. Some 500 metres of fibre optic cable will be separated out within the project-approved corridor following the completion of cable laying.

The Department of Transport has also been advised that Sea Source Offshore will perform support vessel operations on behalf of Nexans as part of the above works. The
activities will be carried out along the entire planned route of the Celtic Interconnector offshore cable route off the South East Coast of Ireland for an expected duration of 17 weeks.

Additionally, the Department of Transport has been notified that Asso.subsea will perform post-lay burial cable protection, post-lay jetting and trenching on behalf of Nexans for the project.

These operations will begin on Sunday 10 August, and it is estimated that this section of the campaign will last until late December, subject to operational and weather constraints.

Further information, including coordinates and maps of the work areas, details of the work vessels and contact details, can be found in Marine Notices No 47 and No 48 of 2025, both of which are attached below.

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Published in Undersea Cables
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Undersea Cables

Undersea cables are vital to Ireland's connectivity, facilitating high-speed internet, telecommunications, and energy transmission. These cables traverse the Irish Sea, connecting Ireland to the United Kingdom and continental Europe, and play a crucial role in global communications.

Submarine Communications Cables:
Ireland is strategically positioned along major transatlantic communication routes. Approximately 75% of transatlantic cables pass near Irish waters, underscoring the nation's significance in global data transmission.
These cables are typically as wide as a garden hose, with the filaments that carry light signals being extremely thin—roughly the diameter of a human hair. They are sheathed in layers of insulation and protection, with cables laid nearer to shore using extra layers of armoring for enhanced protection.

Energy Interconnectors:
In addition to communication cables, undersea interconnectors are being developed to enhance energy security and support the transition to renewable energy sources. The UK has approved the construction of five new subsea interconnector cables to boost the grid's flexibility amidst rising renewable energy. These projects will link the UK with wind farms in Belgium and the Netherlands, and connect England with Germany, Wales with Ireland, and Scotland with Northern Ireland. The cables, with a combined 6GW capacity, are expected to be operational by 2032, increasing the UK's total interconnector capacity to 18GW.

Security Concerns:
The strategic importance of these undersea cables has raised security concerns. Incidents in the Baltics have heightened awareness about the potential risks to subsea infrastructure. Ireland's historical neutrality and limited defense resources have led to calls for enhanced maritime security and defense investments, including modern surveillance technology and international cooperation. The government's response includes participation in EU security projects and collaboration with neighboring countries on maritime security.

In November 2024, a Russian spy ship, the Yantar, was escorted out of the Irish Sea by the Irish navy after it was found patrolling an area with critical submarine pipelines and cables. The vessel's presence heightened concerns due to its proximity to interconnector cables vital for internet services linking Ireland to the UK, operated by major tech companies such as Google and Microsoft.

Regulatory and Policy Framework:
The protection and maintenance of undersea cables fall under the jurisdiction of national governments, with private companies often responsible for their security. In Ireland, the Department of Communications, Climate Action and Environment oversees the regulation of telecommunications infrastructure, including undersea cables. The Irish Naval Service plays a role in monitoring and protecting maritime infrastructure, including undersea cables. Internationally, the United Nations Convention on the Law of the Sea (UNCLOS) provides a framework for the laying and maintenance of submarine cables, recognizing the "freedom of the seas" and the rights of coastal states.

Conclusion:
Undersea cables are indispensable to Ireland's connectivity and economic infrastructure. Given their strategic importance, ongoing efforts are necessary to ensure their protection and resilience against potential threats. This includes enhancing security measures, international cooperation, and adherence to regulatory frameworks to safeguard these critical assets.