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Rotech Subsea completes cable works Saint-Nazaire project

By: Tom Russell 29/11/2021 Rotech Subsea

General Windfarms

Rotech Subsea has completed an export cable de-burial and re-burial scope of work on the Saint-Nazaire offshore wind farm off France’s Guérande peninsula.

Having mobilised in Q2, 2021, Rotech Subsea deployed its RS2 controlled flow excavator (CFE) to work on the export cables. The project comprised de-burying cables C1 and C2 situated at 2m below MSBL, with the cables re-buried to the same depth following jointing operations by the client. Rotech Subsea’s state-of-the-art RS2 controlled flow excavator was selected due to its high flow capabilities which deliver excellent de-burial performances. The ability to use varying nozzle sizes on the tool results in extremely efficient burial operations, whilst maintaining a narrow trench.

The subsea spread of equipment was mobilised for Saint-Nazaire on the Zwerver 1 in Q2, 2021. It was deployed via crane to operate in water depths of between 8-30m LAT, experiencing soil conditions including dense sands with a hard layer present at 2m.

The RS2 de-burying was executed according to client spec with 1 pass at progress rates of between 2-3m/min. Burial depth was achieved in 1 pass at a rate of 1-2m/min with the client requesting a second flushing pass as a contingency.

Rotech Subsea Director of Subsea, Stephen Cochrane, commented: “It was a privilege to have been selected to work with this leading submarine cable player on this scope of work and to deliver an extremely successful project. The performance capabilities of our RS2 meant the project was completed exceptionally efficiently, leading to a saving on total project costs. With the client delighted with the RS2’s exceptional performance, Rotech Subsea looks forward to future collaborations.

“With another successful high profile contract completed on time and on budget Rotech Subsea’s CFE suite of tools is firmly established as the method of choice for cable trenching in Europe and beyond. The enhanced capabilities of our Suspended Jet Trencher RS tools mean they can provide deeper and narrower trenches than ever before, with trenching speeds more than double that of competing older Mass Flow Excavation tools such as contact trenching systems and ploughs.”

The 480 MW Saint-Nazaire wind farm, currently owned by EDF (50%), Enbridge (25.5%) and CPP (24.5%), is expected to be fully commissioned by the end of 2022. It is located between 12 and 20 kilometres off the Loire-Atlantique coast. It will consist of 80 GE Haliade 150-6MW wind turbines. According to GE, each Haliade turbine powers 5,000 homes; the project is expected to generate the equivalent of 20% of the Loire-Atlantique’s electricity consumption.

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Rotech Subsea completes cable works Saint-Nazaire project

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