Rotech Subsea completes cable de-burial and post-lay trenching at London Array

4C Offshore | Tom Russell
By: 03/12/2021 Rotech Subsea
Rotech Subsea has completed key de-burial and post-lay trenching works in the outer Thames Estuary for the London Array offshore wind farm.

In Q3, 2021, Rotech Subsea’s TRS1LD tool completed a de-burial and post-lay trenching campaign of 1,000m of subsea cable at London Array. Deployed using the vessel crane of the Forth Jouster, the TRS1LD carried out the de-burial phase of the cable, which was 1-1.5m below seabed, in two passes. The cable was subsequently extracted.

The TRS1LD excelled, operating in depths of 3-10m and soft sand soil conditions. Currents ranged from 0-2.2kts with General Sea States ranging from 1-1.5m Hs.

The subsequent post-lay trenching phase in October 2021 saw the TRS1LD mobilised on the Nora B with the cable buried to a minimum of 1.5m below seabed. A first pass excavated to 1.75-2.1m depth with a second survey pass confirming the cable had dropped to 1.5-2.6m depth below seabed.

Rotech Subsea Director of Subsea, Stephen Cochrane, commented: “This London Array OWF 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.

“All operations were carried out at speeds of 2-4m/min depending on the areas with each phase completed in two passes to the satisfaction of the client who we look forward to collaborating with again.”

London Array has been operational since since April 2013 and is situated 30km off the north Kent coast, in the Outer Thames Estuary. It has a capacity of 630 MW, supplying enough power for nearly 500,000 homes and reducing CO2 emissions by more than 925,000 tonnes a year. The wind farm features 175 Siemens Gamesa turbines, covering an area of 100km2. It is maintained and operated from the Port Ramsgate and owned by RWE (30%), CDPQ (25%), Ørsted (25%) and Masdar (20%).

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