Renewable energy projects often involve large, greenfield sites, and with that comes the possibility of encountering unexploded ordnance (UXO). Brimstone UXO has been working with a long-term client to provide UXO risk mitigation across seven new solar farms in the UK, helping their projects move forward safely and efficiently.

The sites are spread across Dartford, Norwich, West Yorkshire, South Gloucestershire, Dover, Lincolnshire and Aberdour, covering a combined area of 430 hectares.

Assessing the Risk

Every project began with a UXO risk assessment. This process looks at a site’s military history to determine whether there is a credible UXO risk present. By understanding how a site was used in the past, we can identify whether further mitigation is needed before construction begins.

From the assessments, the risk on 220 hectares was immediately reduced to ALARP (As Low As Reasonably Practicable). Three of the sites carried a part-elevated UXO risk. Rather than taking a blanket approach, we can sometimes zone sites and categorise certain areas as low risk, which helps to keep costs down for the client while maintaining safety.

In total:

  • 2 sites were assessed as low risk
  • 3 sites had a partially elevated risk
  • 1 site had an elevated risk
  • 1 site had an unknown risk (due to a third-party assessment)
Risk assessment data

Ground Investigation and Test Pile Support

Four of the sites required UXO support during ground investigation and test piling works. Due to every site being different, we provided a range of methodologies tailored to specific requirements:

  • Borehole Support – On some sites we delivered borehole clearance using a down-hole magnetometer probe. This progressive probing method ensures that unexploded ordnance is detected before drilling equipment encounters anything below ground.
  • Trial Pit Monitoring – Our teams monitored trial pits in real time, ensuring excavation works could proceed safely.
  • Deep Search Metal Detection – In areas designated for test piling, we used deep search metal detectors to scan for potential hazards before works began.

By applying the most suitable techniques to each stage of the project, we were able to give the client confidence that their ground investigation and piling activities could be completed safely.

Non-Intrusive Surveys

Three sites required UAV (drone) surveys. Brimstone carried out two of these surveys, with a third conducted by another provider.

UAV surveys are particularly effective on solar projects and other greenfield developments. Large areas of open land can be mapped quickly and accurately, with minimal disruption to the environment. This approach is especially useful for solar farms as they often involve shallow ground disturbances, meaning deep intrusive UXO risk mitigation is not necessary. Non-intrusive UXO surveys enable us to survey down to an assured depth of 4 metres, with slightly greater depths possible for large ordnance.

In total, we surveyed 121 hectares using UAVs. The data gathered from these surveys was then carefully analysed to identify anomalies that could represent potential UXO, giving our client the confidence to move forward with the next stage of development.

UXO survey data

Target Investigations

297 anomalies were identified across three sites that required further investigation. This process, known as a Target Investigation (TI), involves excavating anomalies to confirm whether they are unexploded ordnance or more benign items such as buried scrap metal.

Target investigations are a critical step in UXO mitigation. While most anomalies turn out to be harmless, it is only through careful excavation and confirmation that a site can be declared safe to ALARP standards. For this client, all 297 anomalies were investigated, and none turned out to be UXO. This gave the client certainty that their solar developments could continue without unexpected delays or safety risks.

Target investigation data

Supporting Renewable Energy Development

So far, Brimstone has provided ALARP clearance on 316 hectares across five of the seven solar farm sites, with clearance work ongoing at the remaining two.

By tailoring our approach to each site and applying the right mix of assessments, surveys and investigations, we’ve supported the safe development of solar farms across the country. Our work not only helps renewable energy projects progress, but also ensures costs are controlled by avoiding unnecessary mitigation measures.

Solar panels

Planning a Solar or Greenfield Development?

If you’re developing a solar farm or other large-scale project, UXO risk should always be part of your planning. Early consideration of UXO allows you to manage risks effectively, keep your project on schedule, and protect both people and equipment on site.

Brimstone UXO offers a full range of services, from initial risk assessments through to surveys, on-site support and clearance. To find out how we can support your project with safe, efficient and cost-effective UXO risk mitigation:

Learn more about our work across the UK and around the world by following Brimstone on Facebook, Instagram, X, LinkedIn and YouTube.

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