Western HVDC Link: Post lay mattressing operation in the Irish Sea – May 2017

Mariners are advised that post lay mattressing works are planned for the Western Link HVDC cable following the burial works.  The location of the mattressing locations are given in a Notice to Mariners that can be downloaded here and which is summarised below.

Mattressing operations

Concrete mattresses are to be used to protect the Western Link HVDC cable where it crosses other cables and pipelines.  The cable is presently exposed at these locations, which are illustrated in the Notice to Mariners and listed  below:

  • Sirius North Cable 2: 55° 29.966’N 004° 54.815’W
  • Sirius North Cable 1: 55° 29.963’N 004° 54.810’W
  • Lanis 3 Cable: 55° 29.038’N 004° 53.526’W
  • Lanis 3 Cable (2): 55° 15.667’N 005° 13.090’W
  • Lanis 2 Cable: 55° 26.808’N 005° 13.459’W

The mattress installation work will be carried out by the vessel MPSV Argo I.  A pre-installation survey will be performed at each location prior to mattress installation to confirm the cable and crossing location.  Following the positive location of the crossing, a single layer of mattresses will be installed to construct and protect the crossing location.  A post installation survey will be carried out to confirm the mattresses have been positioned correctly.  Details of these operations are provided in the Notice to Mariners that can be downloaded here.

Vessel details

Mattress installation works will be carried out by the vessel MPSV Argo I, operated by Assodivers Ltd.  The details for this vessel, including a link to its present location are given below:-

The vessel will monitor VHF Channel 16 at all times.

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.

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 & 3 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:-

  • Post lay mattressing operations in the Irish Sea – this is the notice described above.  It 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.
  • Exposed cable locations: Update, Irish Sea North Channel, Firth of Clyde – this is the notice described above.  It was issued on 9th May 2017 and provides an update on exposed cable locations in these areas.  The notice can be downloaded here.
  • Western HVDC Link: Cable Installation Campaigns 4b (Firth of Clyde) and 5a (Irish Sea) – this notice was issued on 9th May 2017 and provides an update on proposed cable installation work in the Firth of Clyde and the Irish Sea.  It 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 Fishery Liaison, Western High Voltage DC Link, Western Link Undersea Cable

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