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Frequently Asked Questions

What does UXO mean?

Defined as Unexploded ordnance (UXO) is explosive ordnance that has been primed, fused, armed, or otherwise prepared for use and used in an armed conflict. It may have been fired, dropped, launched or projected and should have exploded but has failed to do so.

UXO also includes explosive ordnance that has not been used during an armed conflict but has been left behind or deliberately discarded. Abandoned explosive ordnance may or may not have been primed, fused, armed or otherwise prepared for use.

What types of UXO are there?

UXO can range in size from small arms ammunition to large unexploded bombs weighing more than 2000 kg (unexploded air delivered bombs are often referred to as unexploded bombs or UXBs). All have the potential to cause significant harm to those who encounter them. They can be found on the surface but are more usually buried underground.

Where does UXO come from?

In the UK UXO can originate from:

  • Ordnance resulting from wartime activities including enemy bombing events during WWI and WWII, long range shelling, munitions deliberately placed as a means of area denial (mine fields, pipe mines etc) and munitions from other home defence activities (anti-aircraft batteries, coastal artillery emplacements, etc).
  • Munitions used as part of military training exercises.
  • Munitions discard after a military training exercise.
  • Munitions dumped as part of a deliberate act, accidental disposal or disposed of ineffectively due to poor working practices during munitions storage and manufacture.
  • Time expired / excess munitions discarded after World War 1 and World War 2.

Is my site at risk from UXO?

It all depends on where your site is located, its history and the likelihood of finding an item of unexploded ordnance. A preliminary desktop risk assessment is the best way to determine if you require a physical site survey. 

For example, if your site is located in a town or city that was bombed during the WWI or WWII, a Detailed UXO Risk Assessment, (can this be linked to the appropriate area in the website) may identify a potential risk from UXO such as UXB’s or incendiary devices, with further appropriate UXO risk mitigation measures required. If your site is located in a rural area of the country, with no history of military activity a Detailed UXO Risk Assessment may determine that no action is required.

Fellows would be happy to advise you further in this. Please get in contact if you have any questions, or you can start the process by ordering a Preliminary Desk top study here.

What is a UXO Risk Mitigation Strategy, and do I need one?

You will need a UXO Risk Mitigation Strategy if a UXO risk has been identified on you project site. The primary objective of the UXO Risk Mitigation Strategy is to create an overall project strategy to reduce the risk posed by UXO in accordance with the ALARP principle. This ensures that the Client expends only the resources necessary in time, effort and cost to reduce the risk to an acceptable level eliminating any UXO threat to the project providing a safe, cost-effective solution.

What are the different kinds of site survey?

There are two types of survey for UXO risk mitigation. Non-intrusive and intrusive surveys. If pro-active mitigation is required it should be considered if the survey is correct for the risk profile of the site, the site ground conditions, if infrastructure exists which will compromise the survey and will it produce meaningful, certifiable results.

Non-intrusive surveys can be employed for both land and marine environments and provide rapid and cost-effective surveys over large areas of site. Designed for greenfield sites or sites that have not previously been developed, RMS UXO will deploy the latest state of the art UXO survey technology either by a pedestrian or vehicle towed survey array.

The effectiveness of these techniques can be limited on sites that have been previously developed and have high levels of metallic contamination. In this case, an intrusive survey may be more appropriate.

Intrusive Surveys are delivered either by CPT or drilling technology these surveys provide point specific, deep vertical survey columns with look ahead capability to the maximum bomb penetration depth. Primarily designed to survey point locations where deep engineering works are being undertaken such a piling, pile clusters and sheet piled walls.

This methodology is deployed to clear areas where engineering works may encounter a UXB up to 25 metres bgl.

Is there a legal requirement to undertake UXO Risk Mitigation measures?

No, the The management and control of UXO risks in the UK construction industry is not mandatory, however, issues regarding risk management at a site are addressed within existing legislation such as the Construction Design Managements regulations in 1994; CDM, last updated 2015.

The most comprehensive and widely referenced UXO guidance for the construction industry is CIRIA C681 – Unexploded Ordnance (UXO) a guide for the construction industry (Published in 2009).

The approach described within CIRIA C681 follows UK HSE guidance and is based upon the ALARP (As Low As Reasonably Practicable) approach. This approach also recommends that proactive risk mitigation measures are employed whenever possible and reactive measures are only employed as a last option. 

The CIRIA guidelines for land based UXO contracting has also been further developed with the introduction of the “Unexploded Ordnance (UXO) Risk Management Guide for Land-Based Projects (C785)” introduced in 2019.

Do I need to consider UXO during site or ground investigation?

Yes, where a UXO risk has been identified or not discounted through a preliminary of Detailed UXO Risk Assessment then the appropriate level of UXO risk mitigation measures should be implemented for the Site or Ground Investigation works such as Bore-Holes, Window Sampling or Trial Pit areas.

What guidance is available for the construction industry about UXO risk?

CIRIA Report C681 - Unexploded ordnance (UXO) A guide for the construction industry.

This report is an independent construction industry guide produced by the Construction Industry Research and Information Association. It focuses on the needs of the construction industry if there is a suspected UXO on site and covers issues such as what to expect from an UXO specialist.

The CIRIA guidelines for land based UXO contracting has also been further developed with the introduction of the “Unexploded Ordnance (UXO) Risk Management Guide for Land-Based Projects (C785)” introduced in 2019.

What guidance is available for marine projects which may encounter UXO?

CIRIA Report C754 – Assessment and management of Unexploded ordnance (UXO) risk in the marine environment.

This report from 2015 is an independent guide produced by the Construction Industry Research and Information Association (CIRIA). It focuses on the risk of encountering UXO during inshore or offshore projects and gives guidance as to how the risk can be assessed and managed.