UXO abbreviates Unexploded Ordinance, a term used to describe unexploded grenades, bullets, artillery shells and mortars. A UXB is an Unexploded Bomb, and many UXOs and UXBs remain today on ex military training areas or areas targeted by air raids in World War II.
Unexploded items such as these clearly pose a health and safety risk, particularly during construction works. A UXO survey will assess whether there are any UXO causes for concern, which may be more common than you first think. According to the Construction Industry Research and Information Association, over 15,000 UXOs were found between 2006 and 2009 on construction sites in the UK. A 1,000kg bomb was found in East London in 2008 which had the potential to cause considerable damage, thus highlighting the importance of a UXB or UXO survey.
Bombs travel through the ground, and so over a course of years they will become invisible as they are covered by terrain and plants. A Geophysical UXO survey will typically detect large UXBs up to 5 metres, and smaller items which are buried up to 2 metres deep. Because of their targeting in World War II, London and Portsmouth are where most UXBs have been discovered.
The identification and location of harmful artillery is often essential at the design stage of construction projects, and an UXO survey may be of particular relevance to the redevelopment of brownfield sites. There are many types of UXO surveys, and to choose the best option surveyors will assess a number of factors. They will look at the ground type, its proposed use, the likely type of UXO and its likely depth. The survey may be used to ensure health and safety, or for use in archaeological exploration. There are three types of UXO survey. Non-intrusive surveys involve the sensing of items from the surface, intrusive surveys involve data collection from sensors inside the ground, and marine surveys detect UXOs and other metallic objects under the sea.
Magnetometry is one of the more common techniques used in UXO surveying. Intelligent software manages the findings of UXO surveys into a comprehensive set of data, filtering out any ambient magnetics.
Buried fuel tanks and air raid shelters are another reason why a geophysical survey may need to be carried out, as they can create construction problems. Geophysical surveys also show other buried features, such as mineshafts and air voids and cavities such as vaults and sewers. The prominence of badger sets also show up in these surveys, and as they are a protected species, they must be considered during construction works. Geophysical surveys can also be used to show the characterisation of land forms, which can be done on a big scale. Other uses for these surveys are reinforced concrete mapping, used for locating foundations and such, when more foundations or a borehole are required; and high frequency structural radar, used for showing features within a building, such as hidden flues and chimneys, historic features and voiding.
If an UXO is discovered in a geophysical UXO site survey, the surveyors will stop all works, evacuate the area and contact specialist disposal experts. Once the area is declared safe it will be possible to continue development.
The importance of UXO surveys