What is UXO? >

Unexploded ordnance (UXO) is explosive ordnance which has been primed, fuzed, armed or otherwise prepared for use. It may have been projected, launched, dropped or otherwise discarded, and should have exploded but failed to do so. Such ordnance may also have been purposely disposed of through burial or burning.

Is my site at risk from Unexploded Ordnance? >

The majority of construction and development projects in the UK should be at no significant risk from unexploded ordnance. However, with the increasing number of developments being planned in areas of the country which were heavily bombed, or in areas previously used by the military, the issue of UXO can be a concern. 1st Line Defence would recommend that at an early stage of any project, a Preliminary UXO Risk Assessment is undertaken to determine whether there is any requirement for further research or whether the risk can be discounted at that stage. If more research is deemed necessary, it is usually recommended that a Detailed UXO Risk Assessment is commissioned to fully qualify the risk through thorough and exhaustive research and analysis. If a risk is identified, site and work-specific mitigation measures can then be recommended to reduce that risk to as low as reasonably practicable.

How can I mitigate/reduce the risk from UXO? >

If a viable risk from UXO has been identified (either through historical research or as a result of empirical evidence of contamination), various risk mitigation options are available to reduce that risk to as low as reasonably practicable. This will depend on the nature of the risk and on the type and extent of works proposed. Mitigation services range from Intrusive and Non-intrusive UXO Magnetometer Surveys through to UXO Specialist On-site Support, Briefings, Search & Clear and Borehole Support. Certain services will only be appropriate for certain sites and for certain risks – for example, a non-intrusive UXO magnetometer survey would only be appropriate for a relatively ‘clean’ site, free from significant background ferrous contamination. It is therefore recommended that 1st Line Defence is contacted to discuss these options in detail to determine the most suitable methodology for your site.

My site is located in an area which was heavily bombed during WWII – will there be a risk of encountering UXBs? >

Not necessarily. Just because a site is located in an area of high density bombing does not by definition mean that there will be a risk of encountering UXBs. It is imperative that detailed historical research is undertaken in order to determine exactly what occurred on and around the site in question during the war. 1st Line Defence Detailed UXO Risk Assessments consider factors such as land use, damage, frequency of access and ground cover to make a ‘micro-level’ assessment of the site – looking at it building by building for example. If a structure and its surrounds survived the war intact and undamaged, it might be considered that evidence of unexploded ordnance is more likely to have been noted and dealt with at the time. Contact 1st Line Defence to find out more about how risk assessments are undertaken and what sort of information is considered.

My site is not in a heavily bombed urban area – presumably it is not at risk from UXBs? >

Not necessarily. It is always worth at least considering UXO risk even if there is nothing obvious known to you in the area. Often the legacy of historic military activity across the UK is not obvious – especially in rural areas. The presence of features and installations such as old airfields, training areas, defensive lines, firing ranges and bombing decoy sites are often not obvious today, many only existing on old maps and plans and in archival documents. It is always worth undertaking a Preliminary UXO Risk Assessment for all sites in the UK to consider such hidden risks.

What is the risk of detonating an unexploded bomb or item of ordnance? >

Items of unexploded ordnance will not spontaneously explode – however if subject to shock or vibration, there can be a significant risk of detonation. There are many examples of WWII-era UXBs detonating unexpectedly in Germany and causing death, injury and damage.

Is it a legal requirement to undertake a UXO Survey? >

It is a requirement to ensure that all construction works are conducted in a safe manner under safety legislation and CDM regulations. In the event that something goes wrong, failure to have considered and addressed potential UXO risk would be a very serious issue.

Do I need to undertake a UXO Desktop Study >

It is recommended that at least a Preliminary UXO Desktop Study is undertaken for every construction project as a matter of course, as per CIRIA guidelines. It is best if such a study is undertaken by a specialist UXO company, but they can also be undertaken by individuals depending on their level of knowledge and access to resources. 1st Line Defence provide Express Preliminary Assessments, costing only £150, with a turnaround of only 1-2 days.

Can a UXO Survey detect deep buried bombs from the surface? >

A non-intrusive UXO magnetometer survey can detect buried ferrous weaponry from surface, however there are limitations to the suitability of this type of survey. It will generally not be suitable for sites with considerable ‘Made Ground’ or background/extraneous ferrous contamination. In ‘clean’ ground however, a 50kg bomb (the most common of the HE bombs dropped over the UK) can be detected down to around 4m bgl (below ground level). Such a survey would not be suitable for providing clearance for deeper buried bombs for activities such as piling or boreholes. An intrusive magnetometer survey is likely to be required.

What do I do if I find a suspect/suspicious item on my site? >

Stop work, do not disturb the device and seek assistance. If concerned, treat any such discovery as potentially ‘live and dangerous’ until it is investigated and checked by a UXO Specialist. Consider having in place a UXO Risk Management Plan so that there is a strategy to deal with any such eventuality. Contact 1st Line Defence for more information about UXO Risk Management Plans.

Can a bomb be found beneath a property which survived the war intact? >

Yes – many unexploded bombs do not penetrate straight into the ground, but more commonly conform to a ‘J-Curve’ – ending their trajectory at a lateral offset from point of entry. Some of the recent UXBs uncovered in London were found under buildings which pre-dated the war. It is thought that they fell into adjacent ‘bomb sites’ unnoticed and unrecorded.

What is the process for Detailed UXO Risk Assessments? >

1st Line Defence UXO Risk Assessments consider the following factors – the risk of UXO contamination (bomb density, ground cover, frequency of access, failure rate etc.), the risk of UXO remaining, the risk of encountering UXO, the risk of initiation, and the consequences of initiation. These factors form the basis of all our risk assessments.

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