Site Investigation

Unexploded ordnance

Unexploded ordnance (commonly known as UXO, sometimes referred to as UXB) are explosive weapons (bombs, bullets, grenades etc.) that did not explode when employed and still pose a risk of detonation. In the UK, the risk of encountering UXO is mainly limited to areas in London, Portsmouth, Plymouth, Bristol, Manchester, Coventry and Birmingham, that suffered wartime bombing and to land used by the military for training or to store ammunition.

When planning a new construction or civil engineering project, it is important to consider UXO risk assessments as part of the site investigation to determine whether any potential risks may be present. The Construction Industry Research and Information Association (CIRIA) have published “Unexploded ordnance (UXO) – a guide for the construction industry” to provide advice on assessing the risk posed by UXO.

There are two types of desk-based assessments that could be undertaken. The first is a ‘preliminary UXO risk assessment’, which provides an initial screening report that includes a probability assessment of UXO risk. The second assessment is a ‘detailed UXO risk assessment’, which provides a more quantifiable risk assessment. It takes into consideration both the probability of the unexploded ordnance threat in addition to the potential consequences.

The level of data provided in the reports offers a basis on which to consider any relevant action, for example if the site would benefit from further investigation or specialist survey from a UXO expert.