Which UXO Survey Is Right for Me?

Unexploded ordnance (UXO) remains a significant risk on many UK development sites. Before groundworks begin, it’s crucial to assess and manage this risk properly. But with a range of UXO survey methods available, how do you know which one is right for your project?

The answer depends on several factors, including your site’s location, historical use, ground conditions, and the type and depth of proposed works. That’s why UXO surveys are never one-size-fits-all.

At Brimstone, we offer both intrusive and non-intrusive UXO surveys, as well as tailored alternatives when surveys aren’t possible. This blog outlines the main survey types we provide, where they’re most effective, and how to decide what’s right for your site.

Intrusive UXO Surveys

Intrusive UXO surveys are one of the most effective methods for identifying deeply buried unexploded ordnance, particularly on sites where piled foundations or other deep excavations are planned. These surveys involve physically probing the ground using a Cone Penetration Testing (CPT) rig fitted with specialist magnetometer probes. The equipment collects magnetic data at depth, enabling our team to detect anomalies that may indicate the presence of UXO.

Our CPT rigs offer detection and clearance down to the calculated maximum bomb penetration depth of 12 metres, far exceeding the capabilities of non-intrusive methods. Whether surveying individual pile locations, clusters, or carrying out a site-wide matrix clearance, we provide flexible and scalable solutions.

The rigs themselves are box-like containers mounted on crawler undercarriages, built to traverse rough or uneven ground often found on construction sites. Using hydraulic pressure, the rig pushes a magnetometer probe vertically into the soil. As the probe advances, it measures magnetic field fluctuations in real time. If an anomaly is detected, the survey can be paused immediately, ensuring safety throughout the process.

Intrusive surveys are suitable for a range of ground conditions, including greenfield, brownfield, made and reworked land. They are particularly well-suited for housing and infrastructure projects, and sites where non-intrusive surveys are impractical.

Striking buried UXO with construction equipment can have catastrophic consequences. Intrusive UXO surveys are designed to detect these hazards before works begin, ensuring the safety of workers and the public, and protecting your project from dangerous and costly delays.

Non-Intrusive UXO Surveys

Non-intrusive UXO surveys are ideal for greenfield sites with open, accessible terrain and shallow buried UXO risks. These surveys use magnetometers mounted on a range of platforms, including pushcarts, towed arrays, and drones, depending on site conditions and access.

These methods are particularly effective at detecting shallow-buried ordnance, such as projectiles, grenades, and mortars (collectively known as Land Service Ammunition). With a typical assured detection depth of up to 4 metres, and potentially deeper for larger ordnance, they offer a practical and cost-effective way to survey open land for UXO.

Non-intrusive surveys are fast to deploy, cause minimal disruption to the site, and are ideal for areas such as agricultural land, undeveloped plots, or fields earmarked for housing or commercial development.

We offer three main non-intrusive survey options:

• Pushcart UXO Survey: Best suited for small to medium-sized sites, this method involves a two-person specialist team manually pushing a five-channel magnetometer system across the land. The equipment detects ferromagnetic anomalies beneath the surface and provides high-resolution data for analysis.
• Towed-Array UXO Survey: Designed for surveying large open areas, this method uses an eight-channel magnetometer system towed behind an all-terrain vehicle. With its wider sensor array, it increases efficiency without compromising data quality, making it ideal for extensive fields or sites under tight timescales.
• Drone UXO Survey: Our drone-mounted systems are ideal for areas with limited ground access or sensitive sites where ground disturbance must be avoided. Equipped with LiDAR, photogrammetry, and magnetometry, our drones can detect ferrous anomalies below the surface and survey large or inaccessible sites quickly and safely.

What if My Site Isn’t Suitable for a UXO Survey?

In some cases, a UXO survey may not be feasible. This could be due to limited access, built-up ground surfaces, dense obstructions, or specific project constraints. When this happens, we still have robust measures in place to manage the UXO risk.

We might recommend a UXO Watching Brief, where a UXO engineer is present during groundworks to monitor excavation and respond to any suspect items. Alternatively, if shallow investigation is required but traditional survey methods can’t be applied, we may propose a Search and Clear operation, a systematic manual inspection and clearance of the ground surface.

For projects involving boreholes or deeper intrusive works, our team can also provide UXO Borehole Support, sometimes known as Downhole Probing. These options help ensure boreholes and pile locations are safely cleared before drilling proceeds.

In Summary

There’s no universal solution when it comes to UXO risk mitigation – each site needs a tailored approach.

• Intrusive UXO surveys are ideal for detecting deeply buried items, particularly where deep excavations or piled foundations are planned.
• Non-intrusive surveys work well on open, accessible greenfield land with shallow UXO risks, offering fast and cost-effective results.
• Alternative solutions like UXO Watching Briefs or Borehole Support are available when surveys aren’t practical.

At Brimstone, we match the right method to your project, helping you manage UXO risks efficiently, safely, and with minimal disruption to your programme.

Still Not Sure Which Survey You Need?

Choosing the right UXO mitigation method can be complex, but you don’t need to make the decision alone. At Brimstone, we assess every site individually to recommend the most appropriate and cost-effective approach based on your development plans and the risk level identified in the UXO Risk Assessment.

If you’re planning a new project and want advice on which UXO survey is right for you, feel free to get in touch. Our experienced team is here to help you move forward with confidence.

Email: enquire@brimstoneuxo.com

Call: 0207 117 2492

Drop us a message: www.brimstoneuxo.com/contact

Find us on Facebook, Instagram, X, LinkedIn and YouTube for updates on our latest work and sector news.