Ocean Science Consulting Limited (OSC) has been working with Environmental Planning Specialists Inc. (EPS), part of the Montrose Environmental Group, to investigate environmental impacts of decommissioning operations and address associated environmental challenges. This exciting collaboration allows OSC’s clients to benefit from collaboration with a highly qualified group of experts who have pioneered the technique of Net Environmental Benefit Analysis-based Comparative Assessment (NEBA-CA) for decommissioning purposes.

Watch the video below for a brief introduction to NEBA-CA and its role in assessment of environmental consequences (both positive and negative) of decommissioning operations.

Within the next decade, hundreds of installations are scheduled to be decommissioned, with ca. 23 structures due to be decommissioned every year (Fowler et al., 2019; OGUK, 2019); however, marine species colonise these structures throughout their operational lives. This phenomenon has led to the development of the ‘Rigs-to-Reefs’ concept. Removal of obsolete installations, therefore, may damage habitats of potential importance. Here is when NEBA-CA becomes a valuable tool.


The NEBA-CA approach not only considers environmental, technical, financial, societal, and/or health and safety factors, but also includes quantified ecosystem service benefits over time to current and future generations. This method is quantitative, scientifically defendable, transparent, objective, and litigation-tested on a variety of metrics such as ecological habitat value, greenhouse gas emissions, technical removal risks, and ecological and human health risks.

‘The goal of a NEBA-CA is to MAXIMISE the ECOSYSTEM SERVICE BENEFITS to the public while managing site RISKS’,
Montrose Environmental (2020).

The NEBA-CA approach contrasts to standard comparative assessments by evaluating decommissioning projects on a case-by-case basis because ecosystem value can vary depending on a myriad of factors. ROV imagery analysis, for which OSC’s staff have substantial expertise, feeds into NEBA-CA, allowing for assessments of potential environmental benefits associated with different offshore structures. A study conducted by OSC’s staff – led by OSC’s Managing Director, Dr Victoria Todd – reported on marine megafauna around sub-sea infrastructure globally. It reported 67 taxa surrounding sub-sea infrastructure, 13 of which represented species of conservation interest believed to be attracted to the site by presence of the installations (Todd et al., 2020). Depth and location are significant drivers of species assemblage, with mid-depth platform sections believed to generate the greatest biodiversity (Bond et al., 2018); however, the interaction of artificial structures and the marine environment is not always straightforward, and NEBA-CA can help uncover it for each individual platform.

If you have any questions regarding decommissioning or the NEBA-CA approach, contact us here.


Bakke, T., Shepherd, J., de Leeuw, J., Wiltshire, K., and Brinkhuis, H. (2018): The influence of man-made structures in the North Sea (INSITE). Independent Scientific Advisory Board (ISAB). 1-25 pp.

Bond, T., Partridge, J.C., Taylor, M.D., Cooper, T.F., and McLean, D.L. (2018): The influence of depth and a subsea pipeline on fish assemblages and commercially fished species. PLoS One 13, e0207703.

Fowler, A.M., Jørgensen, A., Coolen, J.W., Jones, D.O., Svendsen, J.C., Brabant, R., Rumes, B., and Degraer, S. (2019): The ecology of infrastructure decommissioning in the North Sea: what we need to know and how to achieve it. ICES Journal of Marine Science.

OGUK (2019): Decommissioning Insight 2019. Oil & Gas UK.

Todd, V.L.G., Lazar, L., Williamson, L.D., Peters, I., Cox, S.E., Todd, I.B., Macreadie, P.I., and McLean, D.L. (2020): Underwater visual records of marine megafauna around offshore anthropogenic structures. Frontiers in Marine Science 7, 230.

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