Coastline Surveys was awarded a contract to carry out the submarine asset survey including Multi beam bathymetry and Side Scan sonar, ROV Visual inspection and Cable Burial surveys for Wave Hub. Additional Geotechnical investigations were undertaken in test berth 4 to assess the seabed nature for future anchoring of proposed test devices.
The surveys for this important renewable energy site were successfully completed in July and August 2013. Not only is this an important renewable energy project with which to be involved, it is also located right on the doorstep of Coastlines’ Head Office in Falmouth.
The MV FlatHolm, Coastlines’ 24m fully equipped survey vessel was deployed from its base in Lowestoft and stationed in Newlyn harbour for the duration of the contract along with its full time crew and an in-house team of specialist hydrographic surveyors and geophysicists.
The scope of work included a complete bathymetric survey of the entire cable route to establish seabed and asset conditions. This was carried out with the high resolution R2Sonic 2024 Multi Beam Echo sounder together with a Klein 4200 dual frequency Side Scan Sonar. A Cable Burial survey was carried out on the inshore 8km of the cable. The cable Burial survey was completed with an Innovatum Smartrak cable detection system following a tone applied to the cable. The Smartrak system was mounted on a Cougar XT ROV which was also used for the Video inspection element of the works. Surface positioning was provided by a C-NAV 3050 GNSS System and subsurface was provided by a Nexus Easytrak USBL system. A combination of QPS QINSy, Fledermaus, EIVA Navipac and Innovatum software was used for acquiring and processing the survey.
The project was split into 3 phases to make the most of the MV FlatHolm’s unique capabilities to carry out all three elements of the scope of works. The Geotechnical investigation was carried out first – comprising Vibrocores at each of the proposed anchor locations in Berth 4. The vessel was then switched to Geophysical mode to complete phase 2 – the full cable length bathymetric survey. Phase 3 comprised the ROV operations including the Visual and Cable Burial surveys.
The biggest challenge to the project was the strong tidal streams on the site which restricted the window of operations for the ROV work. Using the more powerful Cougar XT was a benefit in being able to extend the window of operations. Excellent vessel handling skills by the dedicated Flatholm crew also maximized productivity during this phase of operations. The ability to remain on site for up to 7-10 days duration enabled maximum use of the working windows with minimal time lost for transit back to port.
By breaking down the project into phases Coastline was able to offer an efficient and cost effective solution with a platform that was able to complete the entire scope of work from very shallow inshore operations out to the offshore end of the project. All operations were completed within anticipated timescales on site whilst maintaining their enviable safety record.
Wave Hub is a grid-connected offshore facility in South West England for the large scale testing of technologies that generate electricity from the power of the waves. It is about 10 nautical miles offshore and is designed to help companies developing new wave energy devices. The UK has some of the largest wave and tidal energy resources in Europe which in the right circumstances could generate up to 1/6 of the UKs electricity consumption.
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Press release, November 20, 2013; Image: Coastline Surveys