UXO in the marine environment: Zetica’s in-house marine geodatabase

Introduction

An estimated 100,000 tonnes of Unexploded Ordnance (UXO) lie in waters around the British Isles, the majority a legacy of World War One and World War Two – whether munitions that failed to detonate or ordnance deliberately disposed of at sea. The types present are wide-ranging, from sea mines, torpedoes, and depth charges to aerial bombs and artillery projectiles.

Understanding and managing UXO risk offshore – Zetica’s in-house marine geodatabase

Marine and intertidal environments are not static. Physical processes and human activity can cause UXO to migrate both horizontally and vertically, depending on its size, density, and the local conditions. This mobility, combined with the sheer volume of ordnance present in UK waters, creates significant challenges for offshore construction, port expansion, dredging, and with increasing urgency, the installation of renewable energy infrastructure such as offshore wind farms.

An unexpected UXO encounter can threaten lives, disturb marine ecosystems, and cause costly project delays. A structured approach to UXO risk management, as set out in CIRIA C754, is essential. This begins with a comprehensive risk assessment: identifying the types of UXO likely to be present, evaluating the probability of encounter, and developing mitigation strategies aligned with project objectives.

Effective risk assessment depends on the quality of the underlying data which is where Zetica offers a decisive advantage. We maintain an extensive, continually updated marine UXO geodatabase, built from a wide range of primary and secondary sources. These include historical mine maps, Admiralty diaries, ships’ logbooks, and air raid records, alongside offshore geophysical surveys, wreck data, and metocean datasets. The breadth and depth of this resource allows us to characterise UXO hazard with a level of confidence that generic or publicly available sources cannot match.

Drawing on the approximately 8,000 features so far mapped in UK coastal waters, our evidence-based marine UXO risk assessments consider a broad spectrum of military activities.  These include offshore munitions disposal, naval engagements, firing ranges, shipwrecks containing UXO, minelaying, aerial bombing and jettisoning events.

We also evaluate environmental processes which may have caused UXO to migrate onto a site.

Our detailed survey designs and mitigation strategies support clients in reducing UXO risk to As Low As Reasonably Practicable (ALARP).

Conclusion

Whether you are in the early design stage of an offshore project or approaching construction, effective UXO management is fundamental to ensuring the safety or your people, minimising delays, and protecting both people and marine environments, and the commercial viability of your project.

Zetica’s marine UXO geodatabase is one of the most comprehensive resources of its kind in the UK. To find out how it can support your project, get in touch with our UXO team and visit https://zeticauxo.com/home/marine-uxo/