How UXO Risk Impacts Brownfield Redevelopment Timelines

On brownfield redevelopments, programme risk is a constant consideration. Ground conditions, contamination, utilities, access constraints and planning requirements are all carefully managed to keep projects moving. Unexploded ordnance (UXO) risk sits within that same category. It is not about worst-case scenarios, but about understanding how a known risk can influence timelines if it is not addressed at the right stage.

When UXO is considered early, it becomes a defined and manageable part of site investigation. When it is not, it can surface later as an unexpected constraint, affecting piling sequences, contractor mobilisation and project budgets.

Where UXO-related delays typically occur

Delays are rarely caused by UXO mitigation itself, but by when the risk is first addressed.

The starting point is a UXO Risk Assessment. A Preliminary UXO Risk Assessment usually takes a couple of days. If a potential risk is identified, a Detailed UXO Risk Assessment will follow, which can take a few weeks. If this stage happens late, it can hold up decisions just as designs or groundworks are progressing.

Where mitigation is required, a UXO survey may be recommended. Depending on site size and survey type, fieldwork can take from a few days to a few weeks. Lead times also need to be considered, with survey works often booked two to three weeks in advance.

After survey completion, a few days are typically needed for data interpretation and reporting. In many cases, this results in an ALARP certificate, allowing intrusive works to proceed. However, some sites require targeted investigations of anomalies, meaning a return to site, which can interrupt planned sequences if not anticipated.
Other mitigation measures, such as UXO borehole support during ground investigations or a UXO watching brief during construction, are straightforward when scheduled in advance, but can affect contractor mobilisation if introduced at short notice.

What happens when UXO is not considered early

If UXO risk is only identified at a late design stage or during construction, the challenge is rarely the technical solution itself – it’s the disruption to timelines and site logistics.

Piling works may need to be paused while surveys are undertaken. Ground investigation programmes may need to be revised to include UXO support. Contractors may be stood down or rescheduled. These knock-on effects can influence budgets, availability of specialist plant hire and overall site coordination.

In contrast, when UXO risk is addressed during early planning and site investigation strategy, mitigation activities are simply built into the programme. Surveys, support services and any follow-up investigations are planned, priced and scheduled in the same way as other ground risk management tasks.

Planning time that protects the programme

UXO risk mitigation deserves the time it needs. This is not about adding unnecessary stages, but about ensuring that credible risks are understood and reduced in a structured way. When planned early, UXO becomes a predictable element of brownfield redevelopment rather than a last-minute disruption.

The outcome is clearer project planning, fewer surprises on site and greater confidence for contractors and project teams. Decisions can be made with a clear understanding of constraints, and works can proceed with appropriate controls in place.

Addressing UXO risk does not have to slow development. It does mean that UXO is best considered at the same stage as other ground risks, during early planning and design. On brownfield sites in particular, this approach helps keep programmes on track and ensures that risk management supports progress rather than interrupting it.

Book your UXO support today

Contact Brimstone UXO to schedule a Preliminary UXO Risk Assessment and make sure your programme stays on track.

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