The news on Friday (20 April 2018) that up to 10,000 people had to be evacuated from homes and offices in central Berlin, after the discovery of an unexploded World War II bomb, should serve as yet another reminder to both developers and landowners back here in the UK of the significant issue of unexploded ordinance (UXO).

The issue arises surprisingly often; with the following recent reports surfacing in the national press.

  1. February 2018 – A 500kg UXO was found near London City Airport after exploratory construction works, causing the cancellation of all flights for a day whilst the device underwent controlled detonation off the Essex coast.
  2. February 2017 - All ferries were stopped and trains between Portsmouth and Southsea station and Portsmouth Harbour were suspended after a World War II bomb containing 131kg of high explosives was found in Portsmouth harbour. There were also extensive road closures in the area affecting access to Gunwharf Quay Shopping Centre.
  3. May 2016 – Thousands of people were evacuated from the city of Bath after contractors unearthed a 226kg World War II shell from beneath the surface of a former school playground.

There are also smaller incidents of UXO discovery which don’t catch the attention of the national press but still present a considerable problem for site owners and contractors, in terms of development delay, remediation costs and, in rare instances, risk to life. The lack of centralised data on such incidents makes risk management particularly difficult for interested parties. The Ministry of Defence has previously confirmed that it attends approximately 60 incidents a year to carry out disarmament work on UXOs but this figure fails to account for the work of various specialist private firms undertaking similar services. The mere fact that a market exists for such firms should serve as a cautionary note for all involved in site acquisition and development.

Origins of UXO

There are two principal sources of UXO discovered on sites in the UK. The first and perhaps most obvious cause is bombs dropped during the Second World War (particularly in large towns and city centres) which failed to detonate on impact. Instead this ordnance becomes lodged in the ground and over time is covered over and forgotten about. As the value of these urban sites has increased dramatically in subsequent decades, developers have tried to build taller buildings with deeper foundation structures, unearthing more UXO in the process.

The second source comes from the historic use of the land itself. Many former military bases (particularly former Royal Air Force bases in the East of England), artillery ranges and defence bunkers have been put to alternative use; as agricultural land, for housing stock and out-of-town industrial estates. The remnants of these past operations (which often involved simply burying equipment on site) can present a real risk to present day occupiers.

Mitigating the risk

Fortunately for developers and landowners, there are an increasing number of search providers who are able to assess the risk of UXO at potential new developments. Usually the search providers are able to offer a two tier service. In the first instance, the provider undertakes a desktop assessment of the likelihood of a UXO risk, relying on Ordnance Survey data and historical records of bombings from the Second World War to determine the risk, in a similar manner to desktop searches for other environmental hazards on the market.

The second tier, usually undertaken where a desktop assessment identifies a risk of UXO, is to undertake a site survey; utilising both non-intrusive 'magnetometer' detection and/or intrusive hydraulic probing to actively seek out UXO, in order to render sites as safe as possible prior to development.

Purchasers are nowadays well versed in the need to commission searches before buying property, looking to identify risks from contamination and flooding through to radon and even chancel repair liability. Although the risk of UXO is small, given the potentially catastrophic consequences (to both property and person) it may soon be the case that UXO joins the list of risks a prudent buyer should be seeking to protect themselves against. This will increasingly be the case for city centre developments and land known to be used for operations during the Second World War.