UXO Survey

We offer a range of solutions onshore, nearshore and offshore to help to mitigate the risk for our clients. 

Unexploded mines and bombs deployed during World War II are still present in the subsurface and seabed around the UK. They continue to cause problems for site developers, asset owners and contractors, as well as local communities.

Onshore and Intertidal UXO Survey

While some land-based UXO surveys can be fairly straightforward, working in the intertidal zone can be highly changeable with a range of conditions encountered.

There are various options for land-based UXO surveys, ranging from handheld magnetometers through to survey platforms towed behind All-Terrain Vehicles (ATVs) and even hovercrafts. 

For surface-lain UXO, depending the size, a UAV based photogrammetry survey will help to acquire a quick and cost-effective dataset while reducing the working hours on site. 

UXO Surveying in Built-up Areas

For UXO surveying in built-up areas, we work with PanGeo Subsea using their patented Sub Bottom Imager (SBI) system.

The SBI is a sophisticated 3D chirp which creates a high-resolution image of the sub-seabed, allowing the identification of targets within the surveyed area. The system can be deployed in shallow water either from a vessel using the GeoLink system or a shoreside crane. The data is then processed, with a target listing produced for further intrusive investigation. 

Nearshore UXO Survey

For nearshore UXO surveying, we tend to deploy a transverse gradiometer (TVG) frame comprising two Geometrics G882 magnetometers with a separation of 1m.

For areas where it is not possible to deploy a gradiometer frame, we tow a single magnetometer at a tight line spacing. The line spacing is typically determined by the threat item identified as part of the desktop UXO study. 

Other sensors generally include a multibeam echosounder to measure the seabed bathymetry, a side scan sonar for surface debris and object detection, and a sub bottom profiler, for shallow seismic data acquisition. Assuming the water depth is sufficient, we position the towfish using USBL positioning, or standard layback measurements in the shallowest areas. 

The magnetometer data is brought into Oasis Montaj for processing before being cross-correlated with the other datasets to allow the creation of target listings.

Offshore UXO Survey

Offshore, there is less restriction in terms of the size and draught of the vessel, which means a larger back deck space and additional deployment capability.

For offshore UXO surveying, there are several options including towing of multiple EIVA ScanFish to maximise productivity, which builds upon the same gradiometer technique as employed nearshore with the added benefit of semi-automated flying. 

For large-scale non-ferrous surveys, PanGeo also has a solution in the form of their custom-built ROTV known as the SeaKite. In the right conditions, the system can acquire up to 130km a day of SBI data; vastly outperforming the standard ROV deployment technique. 

At SEP Hydrographic, our team have decades of experience in UXO surveying in challenging conditions. We work closely with trusted UXO partners to ensure a quality end-to-end service, get in touch today to learn more.