Offshore wind gets first guidance for UXO and boulders geophysical surveying

The Carbon Trust’s Offshore Wind Accelerator (OWA) has published guidance for the geophysical surveying for unexploded ordnance (UXO) and boulders that is being carried out to support subsea cable installation at offshore wind farm sites.

Bibby Hydromap/Illustration

The new guidance is the first of its kind dedicated to the offshore wind industry, according to Carbon Trust.

“After an initial review of the technologies available and past issues with surveying it became clear the equipment was not the issue, but the design. By publishing this work we are providing industry with the tools to optimise this critical part of the planning process for offshore wind farms”, said Jan Matthiesen, director of the Carbon Trust’s offshore wind unit.

Faults in survey design can lead to the need to repeat surveys, or unexpected damage to equipment. Mitigating these risks is critical to minimise resulting project delays and increased costs, the Carbon Trust states.

The new guidance has been developed by building on the Cable Burial Risk Assessment (CBRA) Methodology, an OWA guidance for cable installation published in 2015, which provides a risk-based assessment to optimise the Depth of Lowering of subsea cables.

The Guidance for Geophysical Surveying for Unexploded Ordnance and Boulders Supporting Cable Installation was developed with support from Cathie UK, a geoscience and geotechnical consultancy and Ordtek, an unexploded ordnance specialists.