Understanding Unexploded Ordnance and Its Hidden Risks

Hidden beneath seemingly safe land across the UK lies a potentially unexpected danger that all surveyors, developers and land owners must be aware of, viz. unexploded ordnance (UXO). These remnants of past conflicts and military training pose serious risks, capable of causing damage to infrastructure, endangering lives and incurring significant business interruption costs.

Understanding UXO risks is about far more than just regulatory compliance, it’s essential for site safety and project success.

This article offers a clear overview of unexploded ordnance, covering what it is, why it remains a threat today, and how to manage its risks effectively. By understanding UXO risk management, you can take proactive measures to safeguard your team, assets, and projects from these hidden hazards and the significant costs they entail when encountered.

What Is UXO?

UXO is an abbreviation for Unexploded Ordnance. The term refers to any type of explosive weapon that was used but failed to detonate as intended. These munitions can remain live and highly volatile for decades, even centuries, after their deployment. UXO poses a severe risk to health, safety, and property because its internal mechanisms may be in an armed state, and the explosive chemicals can become unstable over time.

Examples of unexploded ordnance include:

Aerial Bombs
Artillery projectiles
Mortars

Land and naval mines
Rockets
Grenades

Any encounter with a suspected UXO must be treated with extreme seriousness. The area should be secured immediately, and the relevant authorities must be informed without delay.

Is UXO Present Across the UK?

The majority of UXO contamination in the United Kingdom originates from the Second World War. During the Blitz, thousands of tonnes of ordnance was dropped on cities, industrial centres, and coastal areas. It is estimated that a significant percentage of these bombs failed to explode upon impact.

In addition to enemy action, vast areas of the UK were used for Allied military training, defensive actions, and the manufacture and storage of munitions, all of which contributed to the presence of unexploded ordnance.

While post-war clearance efforts were extensive, they were not exhaustive. Many items of UXOs were buried deep underground, located in areas that were difficult to access or missed altogether. As a result, regions with a history of intense bombing or significant military activity still present a considerable risk of UXO encounters during any intrusive groundworks.

Is UXO Still a Risk in the UK?

Decades after the end of WWII, unexploded ordnance remains a persistent and dangerous threat. The longevity of these devices is a key factor; their explosive components can remain active for over a century. Environmental factors such as corrosion, ground movement, and water ingress can further increase their instability, making them more susceptible to detonation from shock or impact.

For developers and construction professionals, the risks are most acute during activities that disturb the ground. These risk scenarios include:

Mechanical Excavation and Piling: Foundation work for new buildings can easily disturb buried ordnance.
Dredging: Port and waterway developments often uncover naval mines and other submerged munitions.
Coastal Works: Construction of sea defences or offshore wind farms can interact with UXOs in coastal and marine environments.
Infrastructure Projects: Road and rail construction can cut through large areas of previously undisturbed land, increasing the likelihood of an encounter.

Recent finds continue to highlight the urgency of the issue. The discovery of a 500kg WWII bomb in Plymouth in February 2024 led to one of the largest peacetime evacuation operations in the UK, demonstrating the significant disruption and danger these devices still pose.

Assessing UXO Risk on Your Site

Determining whether a site is at risk from UXO contamination is a specialised process that should not be left to chance. Relying on generic, free online risk maps is insufficient, as these typically only show WWII bombing density and fail to account for other critical factors like military land use or post-war development.

A formal UXO risk assessment is the only reliable way to evaluate the potential threat. This process is conducted in progressive stages, in line with industry best practice as outlined in CIRIA C681 - 'A guide for the construction industry'.

Stage 1: Preliminary Risk Assessment (PRA) - This is a desktop study that provides an initial screening of the site. It involves systematic historical research to assess four primary factors: wartime bombing in the area, military land use, post-war development, and the nature of the planned intrusive works. For many sites across the UK, an inexpensive PRA can quickly and effectively rule out the need for further action.
Stage 2: Detailed Risk Assessment (DRA) - If a PRA identifies a potential risk, a more comprehensive DRA is conducted. This stage involves in-depth research using sources like local archives, WWII bomb census maps, and aerial photography to create a detailed risk profile of the site. The DRA quantifies the risk and forms the basis for a mitigation strategy.

These assessments utilise a range of digital tools, including GIS mapping and analysis of historical archives, to provide a robust and evidence-based evaluation.

How Artios Can Help

Managing the threat of unexploded ordnance requires specialist expertise. Artios Global provides comprehensive UXO risk management services, covering Stages 1 to 4 of the CIRIA C681 framework. Our services include Preliminary Risk Assessments (PRA), Detailed Risk Assessments (DRA), the development of tailored Risk Mitigation Plans, and On-site mitigation services (Stage 4).

Our commitment is to provide clarity, confidence, and compliance, allowing you to proceed safely and without unnecessary delays or costs.

Secure Your Site Today

The risks of unexploded ordnance are too significant to ignore. A professional UXO risk management approach is essential to in safeguard your project, your staff, and the public. By taking a proactive approach, you can manage these risks in a cost efficient manner to ensure your project's success.

Book Your UXO Risk Assessment