What Is UXO Borehole Support | A Guide for Geotechnical Engineers

Geotechnical investigations play a vital role in understanding ground conditions before construction or infrastructure projects can progress. Boreholes are one of the most widely used techniques for exploring soil, rock, and groundwater, providing engineers with the data needed to design safe and reliable foundations. In parts of the UK, however, borehole drilling carries an additional risk: the possibility of encountering unexploded ordnance (UXO).

UXO remains a hidden hazard across former military sites, coastal areas, and even greenfield land, due to historical world wars, military training, defensive measures, and weapons manufacturing. Ignoring these risks can put people, projects, and budgets at significant risk.

This is where our UXO borehole support comes in – a service designed to make ground investigations safe, efficient, and compliant with health and safety regulations.

Understanding UXO Borehole Support

UXO borehole support (sometimes referred to as downhole support) involves the progressive clearance of borehole positions using a downhole magnetometer probe. This ensures any potential UXO is detected before drilling equipment encounters it underground.

We support a range of drilling techniques, including cable-percussive, rotary, window, and windowless sampling, adapting our approach to suit your site conditions. The service is essential for sites where a moderate or high UXO risk has been identified.

A key benefit is that clearance happens in real time, on site. As drilling progresses, our UXO engineer provides instant feedback on whether it is safe to continue. This keeps borehole drilling moving efficiently while ensuring safety is never compromised.

Why Borehole Support Matters in Geotechnical Projects

For geotechnical firms, time and cost certainty are top priorities. Ground investigations are often tightly scheduled, and delays caused by unforeseen risks can quickly escalate into significant costs with knock-on effects for the wider project. UXO borehole support reduces these risks by integrating safety directly into the investigation process.

Another important advantage is the reporting process. Once the work is complete, a clearance report is generated for the borehole or test location. This document provides engineers with evidence that UXO risks have been properly managed, often forming part of the wider ground investigation package alongside borehole logs, soil test results, and contamination assessments.

What Does Borehole UXO Support Involve?

Before drilling begins, our UXO engineer clears the first metre with a hand-dug pit. A magnetometer probe is then lowered into the borehole at one-metre intervals, scanning until the maximum theoretical bomb penetration depth (typically 12m) is reached. The probe detects magnetic signatures within a one-metre radius, and all findings are carefully recorded.

If no anomalies are detected, drilling continues safely. If an anomaly is identified, drilling stops immediately. We then work with the client to determine the next steps – usually relocating the borehole or, if necessary, conducting a Target Investigation to excavate and identify the object.

At Brimstone UXO, we combine advanced downhole technology with the expertise of our ex-military engineers, helping geotechnical projects move forward safely and efficiently.

Integrating Borehole Support into the Project Timeline

A common question from geotechnical engineers is when borehole UXO support should be included in a project.

Our work often begins with a UXO Risk Assessment, reviewing the site’s history to determine whether UXO may be present and how proposed works could encounter it. If the risk can be reduced to ALARP at this stage, no further mitigation is required.

Where a moderate or elevated risk is identified, or if requested directly by the client, we deploy our team during drilling. Using specialist downhole detection equipment, we monitor for magnetic anomalies that may indicate buried UXO.

Early involvement of UXO specialists allows geotechnical engineers and clients to quote, schedule, and carry out investigations with confidence in both safety and timing. In some cases, borehole support is requested without a full risk assessment, particularly when speed and safe clearance are priorities.

Supporting Geotechnical Engineers Across the UK

Borehole support is not just about managing risk; it enables geotechnical engineers to focus on their core work. By integrating seamlessly into ground investigation teams, UXO specialists take responsibility for the ordnance risk, leaving engineers free to concentrate on soil strength, groundwater, and contamination issues.

At Brimstone UXO, borehole support accounts for around half of our monthly site deployments, reflecting both the scale of the geotechnical market and the trust we’ve built with geotechnical specialists across the UK. Our fixed pricing model for mainland England and Wales allows clients to quote with confidence, without worrying about hidden costs or unexpected changes.

Ensuring Safe and Efficient Ground Investigations

For geotechnical engineers, borehole support provides a straightforward way to manage UXO risk without slowing investigations. It combines safety with efficiency, ensures compliance, and delivers the documentation needed for wider reporting. With experienced UXO specialists on site, geotechnical teams can focus on understanding the ground and delivering reliable data to their clients.

If you’re planning intrusive investigations and want to ensure UXO risks are managed effectively, speak to the Brimstone team today. Our experienced engineers, industry-leading equipment, and rapid response times ensure your project can progress safely, on schedule, and without hidden surprises.

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