Ecosse Subsea Systems (ESS) has completed a £4.7 million boulder clearing and pre-lay trenching project, which it claims has been one of the most successful in the wind energy sector.
As subcontractor to Siem Offshore Contractors (SOC), the Banchory-based subsea specialist completed 86 boulder clearing passes followed by 172 first and multi-passes over a 90km route.
This was during a 13-week boulder clearing and trenching campaign on the EnBW Baltic 2 offshore wind farm project.
Several thousand boulders, ranging up to 4m in size, were cleared from the individual cable routes and ESS performed 260 individual route passes in varying and sometimes challenging soil conditions.
ESS managing director, Mike Wilson, said: “We created a lot of firsts on EnBW Baltic 2. It was our largest contract to date, our first non-UK trenching workscope and our first project for a German offshore wind farm project."
Mobilisation on the 86 cable route workscope started in Gdansk, Poland, with ESS transporting its SCAR ploughing technology by road from Aberdeen.
Installation onboard the SOC operated DP-2 anchor handling tug and supply vessel AHTS Siem Topaz, including a combined ROV and survey spread, took 48 hours, with demobilisation taking place in Sassnitz, Germany, and being completed in only 12 hours.
ESS deployed a seven-man trenching crew plus a 10-man ROV and survey personnel,.
EnBW Baltic 2 is an 80-turbine development 32km north of Rügen island in the German exclusive economic zone of the Baltic Sea. It is owned by German utility company EnBW. The 27sq km site spans water depths from 20-45m and has a wide array of soil conditions from fine sands to glacial tilt with areas of gravels and cobbles with numerous boulders.