Western HVDC Link: Post-lay Mattressing Operation, Irish Sea

[Update – the information in this notice has been superseded by more recent notices.  The notice remains as part of the historical record of notices issued for this project.  Please refer to the most recent notice for an up-to-date record of the notices presently in place for this project.  This can be accessed via the project description page here.]

Mariners are advised that post-lay mattressing operations on the Western HVDC Link cable route are due to start at a location between Northern Ireland and the Isle of Man in the Irish Sea on the 26th July 2017.  A Notice to Mariners detailing the planned operations is summarised below and can be downloaded here.

Mattressing operations

The vessel MPSV Argo I is due to carry out mattress installation works at the point where the Western HVDC Link cable crosses the existing Manx-Northern Ireland Cable.  The use of mattresses at this location is a requirement for cable protection at the cable crossing, where it is not possible to safely bury the Western HVDC Link cable.

The cable crossing lies in 115m of water at a location approximately 25km east of Ballyhornan on the Northern Ireland coast and 31km west of Peel on the Isle of Man.  The coordinates for the crossing are given below:-

  • Manx-Northern Ireland Cable Crossing location: 54° 16.300’N 005° 10.408’W

The installation is expected to start on the 26th July 2017 and to be completed by the end of July (weather & sea conditions permitting).  The Argo I is due to carry out a pre-installation survey to confirm the position of the Western Link HVDC cable and the crossing location.  After this, mattresses will be laid in a single layer to protect the cable, working from north to south.  A post-installation survey will be carried out to confirm that the mattresses have been correctly positioned.

Details of the mattress installation methodology are provided in the Notice to Mariners which can be downloaded here.

Vessel details

Details of the vessels involved in these operations, along with their present location can be found on MarineTraffic.com via the links below:-

  • Argo I: Special vessel | Call sign SVAH9

This vessel will be monitoring VHF Channel 16 throughout the operations.

The vessel involved in this work will be restricted in its ability to manoeuvre and other vessels are reminded to pass at a safe speed and distance.  Fishing vessels are advised to remain a safe distance (approximately 1.5 nautical miles) from the free laid sections and the crossing sections.  Deployed Guard Vessels will monitor the exposed areas and advise of safe distances locally.

Exposed cable locations

Mariners are advised that all cable burial and protection works have been completed on Campaigns 4a & 4b (in the Firth of Clyde) and Campaigns 1 & 2 (in Liverpool Bay).

There are several sections of exposed cable along the cable route to the south and west of the Isle of Man (Campaigns 5a & 5b), and also Campaigns 3 & 6 (to the west of the Isle of Man running towards the North Channel.  These sections comprise crossings of existing cables & pipelines, areas of cable that will be jointed and buried, as well as some small exposures that are under review to reduce the need for rock protection on the cable route.

To assist all mariners, a consolidated list of exposed cable locations  (as of 30th June 2017) has been compiled.  This list is included in the notice to mariners that can be downloaded here.

Details of the vessels that will be involved in future protection work along the cable route will be provided in separate notices to mariners.

Guard vessels

Guard vessels have been stationed along the cable route during installation and burial to ensure the safety of marine users.  They will remain in position until cable protection  operations are completed to advise mariners of the location of exposed cable.

In areas where the cable crosses other cables and pipelines that are in service, the guard vessels will remain on station until cable protection has been completed in these locations (either through concrete mattressing or rock placement).

Vessels are requested to pass at a safe speed and distance and fishing vessels are advised to remain a safe distance (approximately 1.5 nautical miles) from the areas identified. Guard Vessels have been deployed at each location to aid in monitoring the exposed areas and advise of safe distances locally.

The locations of Guard Vessel areas and exposed sections are shown in Tables 1 & 2 of the Notice to Mariners which can be downloaded here.

Notices to Mariners

The Notices to Mariners that are presently in place for this project are:-

  • Western HVDC Link: Post-lay mattressing operations in the Irish Sea – this notice is described above.  It was issued on the 20th July 2017 and provides information about the installation of mattresses on a cable crossing to the west of the Isle of Man.  The notice can be downloaded here.
  • Western HVDC Link: Deep water cable installation, Irish Sea, July 2017 – this notice was issued on 13th July 2017 and provides an update on proposed cable installation and burial work in the Irish Sea to the south and west of the Isle of Man.  It can be downloaded here.
  • Exposed cable locations: Update, Irish Sea North Channel, Firth of Clyde – this notice was issued on 30th June 2017 and provides an update on exposed cable locations in these areas.  The notice can be downloaded here.
  • Shallow water survey work, Ardneil Bay & Leasowe – this notice was issued on the 29th June 2017 and describes the shallow water survey work that will be carried out at Ardneil Bay and Leasowe during July 2017.  The notice can be downloaded here.
  • Post lay mattressing operations in the Irish Sea – this notice was issued on the 11th May 2017 and describes the mattressing operations that will be carried out to protect the cable at service crossings in the Irish Sea and the Firth of Clyde.  The notice can be downloaded here.
  • Debris – this notice was issued on the 15th March 2017.  It informs mariners of the location of some debris that was found during the Pre Lay Grapnel Run along the cable route to the south of the Isle of Man.  The notice can be downloaded here.
  • Concrete mattressing – along the cable route concrete mattresses have been laid at crossings of existing cables and pipelines.  A notice to mariners about the mattressing campaign conducted in 2015 can be downloaded here.

Earlier notices are all rescinded.

Posted in AWJ Updates, Fishery Liaison, Western High Voltage DC Link, Western Link Undersea Cable

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