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Rotech Subsea wraps North Sea wind farm scope

By: Tom Russell 10/06/2020 Rotech Subsea

General Windfarms

Rotech Subsea (Rotech) has completed a three phase pit cleaning, cable lowering and de-burial scope at the Borssele and Triton Knoll offshore wind farms.

The project, which commenced in Q1 2020 and wrapped up in Q2 2020, saw Rotech Subsea contracted to provide TRS1 and TRS1LD Jet Trenching tools to carry out three major scopes of work: pit clearing and cable lowering at Borssele 1&2 in the Dutch North Sea as well as grout bag and cable de-burial at Triton Knoll, in English waters.

Phase 1 and 2 of the project saw Rotech provide its TRS1 tool for two pit cleaning operations. Rotech’s TRS1LD was also provided for phase 3, which consisted of post-lay cable trenching to a specification of 3.0m DOL, as well as cable de-burial.

The subsea spread of equipment was mobilised on the Zwerver III and deployed using the ship’s crane. Water depths ranged from 8m-55m LAT.

“All phases of the project were a great success,” said Rotech Subsea Director Stephen Cochrane. “The bellmouth pit excavation was approximately 30m x 50m x 4m and we successfully kept the pit open despite 1.5m of sand migration every 12 hours.

"The cable lowering was completed with ease, too, with some sections requiring 4.5m DOL.

“This was another great project for Rotech Subsea showcasing the unrivalled capabilities of the new TRS1 and TRS1LD Jet Trenching tools. For example, the TRS1LD sets itself apart from mass-flow excavation tools because its patented design produces narrower, higher pressure jets which are up to seven times more powerful than some other trenching systems. These attributes allowed our skilled operators to complete the scope extremely efficiently and on budget.”

Soil conditions varied at Borssele, ranging from a sandy bed nearshore to harder soils up to 85kPa UUS further out to sea, achieving an average progress rate of 2m/min. Approximately 100m of cable and grout bags were de-buried from 2.5m below MSBL, allowing the client to commence with cable removal operations.

For more information on offshore wind farms worldwide, click here.

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Rotech Subsea wraps North Sea wind farm scope

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