New guidance for offshore wind industry on geophysical surveys for unexploded ordnance and boulders

Sea explosion

The Carbon Trust’s Offshore Wind Accelerator (OWA) has today published guidance  for the geophysical surveying for unexploded ordnance (UXO) and boulders, supporting subsea cable installation by improving the efficiency and effectiveness of surveys. 

The new guidance is the most comprehensive of its kind, and the first dedicated to the offshore wind industry. It aims to optimise surveys by equipping offshore wind developers and surveyors with information to facilitate the creation and utilisation of data according to best practise, a consistent structure and improved survey result documentation.

UXO and boulders present risks to subsea cables, as well as the operations and equipment required for their installation, maintenance, and decommissioning. Data generated by geophysical surveys undertaken in the planning stages of offshore wind farms form a key part of the knowledge base for risk evaluation and management of these operations - and can cost millions of pounds.
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 development of this guidance builds on  previous OWA guidance for cable installation, the Cable Burial Risk Assessment (CBRA) Methodology, published in 2015, which provides a risk-based assessment to optimise the Depth of Lowering of subsea cables. 
The guidance was developed with support from Cathie UK, a geoscience and geotechnical consultancy and Ordtek, unexploded ordnance specialists. 

Jan Matthiesen, director, offshore wind, the Carbon Trust, commented: 

“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.”


For further information please contact:
The Carbon Trust press office on +44 (0) 20 7170 7050 or

Notes to Editors

About the Offshore Wind Accelerator

The Offshore Wind Accelerator (OWA) is the Carbon Trust's flagship collaborative research, development and deployment programme. The joint initiative was set up between the Carbon Trust and nine offshore wind developers in 2008, with the aim to reduce the cost of offshore wind to be competitive with conventional energy generation, as well as provide insights regarding industry standard (and best practice) health and safety requirements. 

The current phase involves participation and funding from nine international energy companies: EnBW, Equinor, innogy, Ørsted, RWE, ScottishPower Renewables, Shell, SSE, and Vattenfall Wind Power, who collectively represent 75% of Europe’s installed offshore wind capacity. This project also received partial funding from the Scottish Government.

About the Carbon Trust

Established in 2001, the Carbon Trust works with businesses, governments and institutions around the world, helping them contribute to, and benefit from, a more sustainable future through carbon reduction, resource efficiency strategies, and commercialising low carbon businesses, systems and technologies.

The Carbon Trust:

  • works with corporates and governments, helping them to align their strategies with climate science and meet the goals of the Paris Agreement
  • provides expert advice and assurance, giving investors and financial institutions the confidence that green finance will have genuinely green outcomes
  • supports the development of low carbon technologies and solutions, building the foundations for the energy system of the future.

Headquartered in London, the Carbon Trust has a global team of 200 staff, representing over 30 nationalities based across five continents.

Related links

Offshore Wind Accelerator (OWA)

Learn more about our work in offshore wind

Guidance for geophysical surveying for unexploded ordnance and boulders supporting cable installation