This informal CPD article, ‘Managing your site’s UXO risk’, was provided by Brimstone Site Investigation who are Explosive Ordnance Disposal (EOD) experts dedicated to the safe removal and disposal of Unexploded Ordnance (UXO) across the United Kingdom and around the globe.
Managing your site’s UXO risk
If you’re in charge of a construction project that involves groundworks, whether it’s humanitarian, governmental or commercial, you need to consider the possibility of there being buried unexploded ordnance (UXO) onsite. UXO is any explosive ordnance which has been primed, fuzed, armed or otherwise prepared for action, and which has been buried, dropped, fired, launched, projected, thrown, or placed in such a manner as to constitute a hazard. It remains unexploded either by design or malfunction.
Although your mind may jump straight to undiscovered world war bombs, in reality, there are many other sources of UXO contamination in the UK, including allied activities and weapons manufacturing. UXO can pose a real danger to construction projects. This is why UXO risk mitigation is so important.
Assessing the risk
The first step in UXO risk mitigation is assessing the risk through a risk assessment. This will place your site in its military context, based on historical research, post-war developments and modern methods of construction. It will also take human factors, allied and enemy action and additional sources of information into account, providing you with a risk rating and any recommended further action. It may be that a risk assessment is all you need to do to mitigate the risk of UXO on your site.
UXO surveys
If your site is deemed to be moderate or high risk, the next step in mitigating the risk is having a UXO survey undertaken on your site. This detects anomalies beneath the surface that could be items of UXO. These results are then analysed by geophysicists, who check the data for characteristics of unexploded ordnance.
The type of UXO survey you require will depend on a few different factors. For example, a non-intrusive UXO survey is only suitable for greenfield sites, can reach hard to access areas and can only clear depths down to 6m. In comparison, an intrusive survey can survey to a depth of 25m and is suitable for made ground or brownfield sites. If the survey identifies any targets, you may need to have these investigated.
Ground investigations
Usually, a ground investigation is a follow up activity to a UXO survey, however, they can be carried out as a stand-alone procedure. The services available might include watching briefs, borehole support or a search and clear. A watching brief does pretty much what you’d expect from its name. It involves a UXO engineer supervising an excavation to mitigate the likelihood of any unplanned UXO encounters. This service supports reduced digs, excavations, trial pits and archaeology projects.
Borehole support involves clearing borehole positions as the borehole deepens, making sure all operatives are kept safe during the process. At intervals of 1-2m, beginning at the surface, the UXO engineer will test the hole for magnetic signatures by lowering a magnetometer probe on a cable extension to the bottom of the borehole. Finally, a search and clear is where a UXO engineer will clear lanes in the ‘at risk’ zones using search equipment. They will log, mark, and excavate any targets as they present themselves.
Guidance on UXO risk mitigation
Surprisingly, there’s no legislation in the UK which defines the steps you must take to check for UXO before construction or development work begins. However, there are legal obligations under the Health and Safety at Work Act 1974 and CDM2015 to ensure the health and safety of employees. CIRIA C681 is a well-known industry guide for the management of risk associated with UXO. It focuses on the needs of construction professionals and reduces the risk of an unexpected UXO encounter.
The guide focuses primarily on UXO from World War I and II aerial bombardment, but it is broadly applicable to other forms of unexploded ordnance.
Creating a better, safer world for everyone
So far, nobody has been killed in the UK by a UXO incident. Help us keep it that way, by taking the necessary steps before conducting your project.
We hope you found this article helpful. For more information from Brimstone Site Investigation, please visit their CPD Member Directory page. Alternatively, you can go to the CPD Industry Hubs for more articles, courses and events relevant to your Continuing Professional Development requirements.
