If you ever come across an unexploded bomb on a construction site, new guidance from the Construction Industry Research and Information Association should help you assess the risk and deal with it appropriately.

Unexploded Ordnance (UXO) – a guide for the construction industry is approved by the Health and Safety Executive and suggests a four-phase approach to mitigating UXO risk, from consulting mapping information and commissioning a preliminary risk assessment to risk mitigation measures should a device be discovered.

Unexploded bombs and ordnance from the Second World War are still relatively common in the UK. Between 2006 and 2009 approximately 15,000 devices, ranging from aerial bombs to mortar rounds and grenades, were removed from construction sites. According to CIRIA, around 5% of these were still live.

Until now, there has been little guidance to help clients, developers and groundworks contractors assess the risks if UXO is found during the intrusive engineering phase of a project.

The disruption UXO can cause was demonstrated in April when contractors working on a building site in Brentor Road, in the Prince Rock area of Plymouth, found a 250lb bomb. Almost 1,000 homes had to be evacuated before the device could be moved to the sea.