Behind the Veil – Understanding the Assessment of Unexploded Ordnance Risk

In response to complaints from the construction industry about poor practices, CIRIA, through collaborative consultation, has established best practice guidelines for assessing the risk from unexploded ordnance (UXO) on development sites. The “Clients’ Guide for Assessing Risks on UXO Sites” provides the tools to review UXO risk assessments against what is the defacto industry standard, providing a consistent approach, and advocating semi-quantitative processes that introduce statistical rigour into what has often been a wholly subjective assessment; an approach supported by the HSE within the Clients’ Guide.

The CIRIA Approach

The report is based on a rigorous Four Phased approach to assessing and mitigating UXO risk, namely; Preliminary Assessment, Detailed Assessment, Mitigation Design and On-Site Mitigation Contracting.

The Preliminary Assessment is designed to screen out sites where no significant UXO risk exists; 80% of sites could be filtered out at this initial stage, utilising cost effective risk mapping products, that enable a rapid assessment the overall potential.

If a significant UXO risk is assessed in the Detailed Assessment, the next phase is to design Risk Mitigation activities to deliver a sign-off to satisfy the ‘As Low As Reasonably Practicable’ (ALARP) principle. The time, costs and effort of mitigating the UXO risk are balanced against reducing the risk to an acceptable level; an approach that should eliminate the problem of inappropriate and extensive on-site UXO mitigation work. 6 Alpha Associates’ work on the Crossrail project, designing the UXO mitigation in line with ALARP, this approach enabled the initial contractor figure for UXO survey to be reduced by 85%.

Separating the delivery of the risk assessment and mitigation design, from undertaking the on-site work, removes the potential conflict of interest whereby a single turn-key UXO contractor may artificially increase risk in order to generate follow on work.

The CIRIA process will ensure a balanced approach that ensures only an appropriate amount of time, effort and costs are targeted at UXO risk mitigation.

The Clients’ Guide for Assessing Risks on UXO Sites can be purchased from CIRIA here.