UXO Risk Assessments for Geotechnical Projects

Geotechnical investigations are a critical early stage in any construction or infrastructure project, giving developers, engineers, and designers the ground data they need before work begins. On sites with a history of military activity, those investigations carry an additional hazard that has to be managed deliberately: unexploded ordnance (UXO). A UXO risk assessment is the foundation of that management, establishing whether a site is likely to be affected and what mitigation, if any, is needed before intrusive works proceed.

This guide sets out what a UXO risk assessment involves, why it matters for geotechnical work, and how the staged process fits into project planning.

Understanding the Link Between Geotechnical Work and UXO Risk

While the Second World War is the most recognised source of UXO in the UK, it is far from the only one. The country’s long and varied military history means UXO hazards can arise in many different contexts, not just in areas affected by wartime bombing. UXO risks can originate from former military training areas and firing ranges where live ammunition and explosives were used; historic defence sites and airfields where munitions were stored, handled, or disposed of; research, testing, and manufacturing facilities that produced or experimented with weaponry; coastal and marine environments where ordnance was dumped after conflicts or used for anti-invasion measures; and post-war disposal activities, where surplus munitions were buried or destroyed on land since repurposed for development.

As redevelopment continues to extend into land with these historical uses, intrusive ground investigation techniques such as boreholes, trial pits, and window sampling can reach depths where ordnance remains buried. Without an appropriate UXO risk assessment, those activities can expose personnel, equipment, and project schedules to avoidable risk. (For a fuller look at what is at stake when this risk goes unmanaged, see our article on the risks of ignoring UXO in geotechnical projects.)

Why a UXO Risk Assessment Is Essential

A UXO risk assessment identifies whether a site is likely to be affected by unexploded ordnance and determines the level of risk to planned geotechnical activities. It also provides the basis for any mitigation measures required before and during intrusive works.

The key benefits are:

• Protecting personnel and equipment by ensuring the safety of engineers, drillers, and site operatives
• Reducing project delays by identifying risks early rather than discovering them mid-works
• Ensuring compliance with recognised UXO risk management guidance such as CIRIA C681 and the Construction (Design and Management) Regulations 2015
• Supporting due diligence, since many clients, contractors, and insurers now require a UXO risk assessment before intrusive investigations take place

The UXO Risk Assessment Process

At Brimstone UXO, we follow a structured approach tailored to each project’s location, scope, and depth of investigation. The process typically involves three stages.

A Preliminary UXO Risk Assessment is a desk-based study reviewing historical bombing data, military records, and mapping to establish whether there is any potential for UXO contamination. A Detailed UXO Risk Assessment is a deeper analysis that considers site-specific factors such as past land use, recorded bomb strikes, depth of made ground, and the proposed geotechnical methods. Finally, mitigation recommendations depend on the findings and may include a non-intrusive or intrusive UXO survey, borehole support, or on-site engineer supervision during drilling.

This tiered approach ensures mitigation is proportionate to the level of risk and that resources are focused where they are most needed. The question of when to introduce each stage is covered in more detail in our guide on when to bring UXO expertise into a geotechnical project timeline.

Integrating UXO Risk Management into Geotechnical Planning

Incorporating UXO risk management early in a geotechnical project allows teams to plan investigations safely and efficiently. Our specialists work closely with geotechnical engineers to ensure that UXO considerations are integrated into the site investigation design and method statements.

UXO risk assessments commonly support geotechnical projects across a range of settings, from brownfield redevelopment sites with historic military use to city centre locations affected by wartime bombing. They are equally relevant on former airfields, ranges, and munitions storage sites, as well as in coastal or estuarine areas where wartime dumping or defensive activities took place.

Supporting Safe Ground Investigations

Whether you are carrying out a single borehole investigation or a large-scale ground investigation programme, managing UXO risk is a critical part of ensuring safety and maintaining project momentum. Brimstone UXO provides comprehensive UXO risk assessments and on-site support tailored to the specific needs of geotechnical projects, helping clients make informed decisions, plan safely, and progress with confidence.

If you are planning geotechnical investigations and need to understand your site’s UXO risk, get in touch to discuss your project, or learn more about our UXO risk assessment services.

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