Rotech Subsea has completed a three phase pit cleaning, cable lowering and de-burial scope at the Borssele and Triton Knoll offshore wind farms.
Rotech Subsea provided TRS1 and TRS1LD jet trenching tools to carry out three major scopes of work: pit clearing and cable lowering at Borssele offshore wind farm in the Dutch North Sea as well as grout bag and cable de-burial at Triton Knoll offshore wind farm in English waters.
The subsea spread of equipment was mobilized on the Zwerver III and deployed using the ship’s crane.
“All phases of the project were a great success. The bellmouth pit excavation was approximately 30m x 50m x 4m and we successfully kept the pit open despite 1.5 meters of sand migration every 12 hours. The cable lowering was completed with ease, too, with some sections requiring 4.5 meters DOL.
“This was another great project for Rotech Subsea showcasing the unrivaled 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.”Rotech Subsea director, Stephen Cochrane.
Soil conditions varied at Borssele project ranging from sandy conditions near shore to harder soils up to 85kPa UUS further out to sea, achieving an average progress rate of 2m/min. Approximately 100 meters of cable and grout bags were de-buried from 2.5 meters below MSBL, allowing the client to start with cable removal operations.