Aberdeen-based Rotech Subsea has concluded de-burial and post-lay trenching works on the London Array offshore wind farm.

According to Rotech, the work in the other Thames Estuary was completed for a ‘major’ marine services player.

A de-burial and post-lay trenching campaign of one kilometre of subsea cable at the offshore wind farm was carried out in Q3 2021.

The company deployed its controlled flow excavator TRS1LD tool using the vessel crane of the Forth Jouster for the de-burial phase of the cable, which was around 1.5 metres below the seabed. The cable was subsequently extracted, Rotech explained.

In the post-lay trenching phase, which took place in October, the tool was mobilised on the Nora B. The cable was buried to a minimum of 1.5 metres below the seabed.

A first pass excavated to 1.75-2.1-metre depth with a second survey pass confirming the cable had dropped to a 1.5-2.6-metre depth below the seabed.

“This London Array offshore wind assignment was another extremely successful deployment for our TRS1LD controlled flow excavator which is capable of delivering deep, narrow, precision trenches with speeds more than double that of competing mass flow excavation tools such as contact trenching systems and ploughs”, said Stephen Cochrane, Rotech Subsea director of Subsea.

Cochrane added that all operations were carried out at speeds of 2-4 metres/minute depending on the areas with each phase completed in two passes.

Most recently, Rotech wrapped up export cable de-burial and re-burial work at the Saint-Nazaire project, which is to become the first commercial offshore wind farm in France.

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