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Talking Point with David Mole

Looking at why unexploded ordnance assessments should form part of every desk study

When embarking on a new project, the probability of identifying unexploded ordnance (UXO) that originated from the Second World War might not be as uncommon as you would first imagine.

According to research by CIRIA, between 2006 and 2009, approximately 15,000 devices were removed from construction sites - of which 5% were live.

“At Ypres in Belgium, two construction workers were killed on 19 March by a WWI explosive”

It is important that the correct risk assessments are undertaken prior to any new ground works commencing, to ensure you are aware of the potential UXO risk and you are aware of how to deal with it in the correct way.

While infrequent, we sadly continue to read reports of injuries or even deaths that have occurred as a result of uncovering live munitions. In Belgium two construction workers were killed on 19 March by a WWI explosive while working on a project in Ypres.

As the explosion in Germany demonstrates, encountering an unexploded bomb on a construction site is a low probability but extremely high consequence event, particularly if you take into account potential loss of life.

Shockwaves can also spread underground for some distance, causing damage to foundations and other underground works. As I see it, it is the potential consequence, rather than the probability, which really drives the importance of undertaking detailed risk assessments before
any work starts.

The term “bomb search” covers all the explosive remnants of war - from aerial bombs and grenades through to torpedoes and mortar round. Anecdotally, in WWII, thousands of tonnes of explosive fell on the UK, with 17,000t falling on London alone, with figures suggesting that approximately 10% of these did not detonate on impact.

Other cities that would have been particularly affected include Birmingham, Bristol, Manchester and Newcastle, as well as ports, harbours, RAF and other military sites.

Furthermore, an eighth of the UK’s landmass has been used by the military for training, and occasionally live ammunition can be left behind. While most of these are known about, some can still come as an unwanted surprise.

Preliminary UXO risk assessments can provide a quick yes or no answer as to whether there is any risk of encountering a bomb. It’s a quick and relatively cost effective option, which has been developed in line with guidance from CIRIA and endorsed by the Health and Safety Executive.

A more detailed UXO risk assessment will be needed if there is a yes response to the initial search and this will detail the type of threat, the size, origin and also takes into account the proposed construction method and how that would impact on risk of detonation.

This knowledge is essential to the implementation of risk mitigation measures to reduce the level of risk to an acceptable level to allow construction to proceed.

While the level of cost involved in these searches, and potential risk, is small, the step should not be overlooked for the ultimate safety of all those concerned.

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