Swale export cable installation

We started works to connect the onshore substation at Cleve Hill to the two offshore substations at the wind farm site in 2011.  In total we’ll lay four export cables.  The first cable was installed at the end of 2011 and the second installed in early 2012.  The remaining two cables installed will be installed later this year.  The installation of each export cable will start in The Swale – as this is a busy area for sailing and shipping activities we’re working closely with sea users and the local community to make sure that disruption to planned activities in The Swale is minimised.

In advance of the export cable being installed the route had to be cleared of debris. This was done by a vessel dragging a grapnel hook (a modified anchor which penetrates the seabed) along the seabed. This work was completed in 2011.

We’re expecting to start the installation of the third export cable around June 2012, with the installation of the fourth and last cable following on from this.

Cable-laying offshore can be subject to unforeseen events with installation dates subject to change. We will keep this page updated with the latest schedule information.

Cable installation sequence

The installation of each cable will start in the inter-tidal area of The Swale.

• The cable laying vessel (CLV) will be moored in The Swale, approximately 1.5-1.8km offshore.
• A winch, installed at the onshore substation site, will pull the cable from the CLV through ductwork already installed under the sea wall.
• The cable will be floated over the mudflats using a buoyancy system.
• Trenches will be dug into the mudflats using amphibious excavators. The cable will be laid in the trenches and the trenches backfilled.  A displacement burial tool, aboard a small vessel, will also be used to bury the cable.
• From approximately 2.5km out to the offshore substations the cable will be laid and buried simultaneously using a plough deployed on the seabed.

Sea Users Local Liaison Committee (SULLC)

A local liaison group has been established with sea users which meets on a montly basis. We will provide updates and communications, and work with the SULLC to mitigate the impacts of the cable laying activity on users of The Swale.

Graveney Local Liaison Committee (LLC)

Updates on cable laying activities will be given to the LLC which meets on a monthly basis. The approved Traffic Management Plan (TMP) will remain in force throughout the export cable installation. No HGV movements will be permitted outside the currently agreed times.

The installation of the cables through the ductwork is tidal dependent and must be carried out on a continous basis until the cable has been installed and the ducts re-sealed. It is anticipated that 24 hour working over a period of six days, allowing for contingencies, will be required to install each cable.