Using the latest technology and techniques to undertake unexploded ordnance surveys

Borehole geophysics takes advantage of using regular geophysical techniques at depth down a borehole. The techniques operate in the same manner as they would on the surface, with the advantage of providing high-resolution data at depth. Borehole seismic surveys are used to obtain in situ properties of soil and rock strata and are often used as part of a comprehensive geotechnical investigation.

Unexploded ordnance (UXO) and unexploded bombs (UXB) still pose a risk of detonation. There are many sources of UXO contamination, most from wartime; however, more recent sites such as military training grounds can also contain significant numbers of UXO and UXBs. About 60 bombs are found every year in the UK, the majority in sites undergoing new development. It is important to understand the hazards and risks early in the development of a site in order to avoid unanticipated costs and delays. As part of the management of UXO risks on development sites, the findings of a thorough and detailed desk study and risk assessment are used to inform any survey (if required), thereby ensuring that the correct UXO detection techniques are employed.

Detection surveys

In order to determine the most effective geophysical detection methods on a site, consideration is given to a number of factors, including UXO target type and size, anticipated burial depth (centimetres to many metres) and type of ground conditions present at the site. Where shallow buried UXO may be present, a non-intrusive surface electromagnetic or magnetic detection survey using one or more techniques may be appropriate. For deeper targets, in-hole magnetic detection methods may be deployed. This is typically undertaken with a magnetometer probe at discrete intervals down a borehole during drilling works to detect the presence of deeper UXO.

Data processing and interpretation

When conducting UXO investigations, data quality and targeting accuracy are key to effective characterisation and remediation of UXO sites. Without further analysis or investigation, it cannot be determined from the data alone whether an object is of UXO origin or is scrap metal. RSK uses advanced analysis and modelling software on each magnetic and electromagnetic anomaly when needed to determine its characteristics, including amplitude, size and likely depth, in order to establish its likelihood of being UXO. Depending on the findings of the above, an intrusive target investigation may be required to further mitigate the remaining potential UXO risk.

Other geophysical survey applications

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RSK Geosciences is part of the RSK group of companies

The RSK group is a leading integrated environmental, engineering and technical services business offering bespoke end-to-end solutions to a variety of sectors. Headquartered in the UK but with an established presence throughout Europe, Africa, the Middle East, Asia and Australia, RSK helps organisations around the world achieve their business aspirations in a sustainable and efficient manner.