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Jeudi, 06 Octobre 2011 12:00

How to Find WWII-Era Unexploded Munitions

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  • 12:00 pm  | 
  • Wired October 2011

German Dornier 217 bombers over London
Photo: Getty

A few years ago, construction for the 2012 Summer Olympics in London unearthed a gift from the Nazis: a 2,000-pound unexploded bomb. Such finds are common—during World War II, London was pummeled with 19,000 tons of bombs—and vintage ordnance can still blow (in 2010, three bomb-disposal experts were killed while digging up a 65-year-old 1,000-pounder in Germany). So UK projects often begin with a call to an outfit like Zetica, a leader in sniffing out subterranean munitions. Each year, Zetica finds more than 8,000 shells, bombs, and mortars in the UK alone. Here’s how.

  • 1 Research Targets

    One-tenth of the bombs dropped on the UK never detonated. Luckily, they left a paper trail. Zetica pores over vintage air-raid info and aerial photos in libraries and record offices to ID high-risk zones—mostly old industrial areas and known Luftwaffe flight paths.

2 Calculate Depth

Knowing that bombs may be at a site is half the battle. But how deeply buried are they? Zetica designed software that calculates how far the most common bombs (110 to 2,200 pounds) can travel through various types of soil and rock at terminal velocity.

3 Scan the Scene

A surface-based magnetometer is used to detect ferrous objects. An electromagnetic survey can also be used to find ordnance or fuse components that contain nonferrous alloys or brass. Special 3-D-imaging software helps visualize the size and shape of the objects.

4 Drill Down

Surface-scanning methods can sniff out explosives down to only 5 feet. For searches to depths of up to 65 feet, Zetica deploys a truck-mounted hydraulic system, which sends down a magnetometer housed inside a toughened alloy probe.

5 Dig, Defuse, Dispose

When clients request that Zetica dig up unexploded ordnance, police and military personnel are called in to defuse and dispose of the munitions. But most of the time, bombs are left untouched—they haven’t blown yet, and it’s cheaper just to build around them.

Illustration: Jameson Simpson


Authors:

French (Fr)English (United Kingdom)

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