I live in Arnhem, the Netherlands, which some of you may know from the movie A Bridge Too Far. The bridge from the movie is only a 15 minute walk away from my house. We regularly hear news of old explosives from WWII being found whenever someone is digging up a site for whatever reason. Which leads me to wonder: how likely is it that one of those things are going to explode after all this time? And would it take something like a digging machine jarring it a bit too much or could they explode spontaneously?
From what I read in German papers in the last few years bombs going off even now is reasonably common, but these are mostly aerial bombs with delayed fuzes (designed for delays of hours to max. days) used in the strategic bombing of Germany as a sort of double-tap tactic - I rather suspect the Allies eschewed this for political considerations when bombing targets in the occupied Netherlands. It seems contact fuzes had a much lower failure rate.
One example of a WWII bomb going off: an explosion in the Danube at Vienna on August of last year (German-language article http://diepresse.com/home/panorama/wien/1282897/Wien_Heftige-Explosion-in-der-Donau?from=gl.home_panorama )
Would the UXO in your area be aerial bombs or artillery shells?
Friendly note: I have nothing for answering your questino, but if you’re going to stick around, you’ll probably want to email a mod/admin to change your name. There’s already a ‘crazycatlady,’ and they prefer having names not be so closely matching.
Like LocoGatoDama or just Loco CatLady.
And yes, those bombs are still very much active and can still be set off.
There was heavy fighting around here in 1944, so whatever would go boom in that era can probably be found here.
I’m considering Crazier Catlady.
Good, that still leaves Craziest Catlady for when I have a sex change, and get some cats. I’m already crazy, though. 
I’m guessing artillery shells, grenades and probably a small number of things like anti-tank rockets, based on what was going on at Arnhem in 1944.
Many years ago I read a Smithsonian article about still very hazardous buried rounds in France
from WW ONE. A significant public safety issue, and killing people on a yearly basis, they commanded
the attention of squads of I think full-time disposal experts.
One problem France has that Arnhem does not have is that the front line did not vary much
for years, so there was a much longer and denser concentration of fire. Also consider that if
France has a problem arising from WW1 then Eastern Europe must have a similar one arising
from WW2, although in Eastern European the concentration of unexploded rounds would have
to be much more diffuse, since the front lines were not nearly as static there as they were
in the WW1 West.
Yup - the Département du Déminage, “Department of Mine Clearance,” responsible for the clearing of the yearly Iron Harvest.
How about “Cattier Crazylady”? Unfortunately, “More Ladylike CrazyCat” just doesn’t roll off the tongue very well.
There’s an unexploded mine from WWI on Messines Ridge. 22 tons of explosive. A similar unexploded mine went off in 1955 when struck by lightning, so it is by all means still very dangerous.
“Bodac” is one company that does bomb removals in the Arnhem area.
See
Germany is still removing 2000 tonnes of WW II bombs each year.
They said the bombs are “increasingly unstable”.
Not sure if that is to say they are becoming more likely to explode,
or the explosive chemicals are degrading and becoming less explosive… but releasing poisonous gases and materials. (ammonia and nitrates .)
Yep. I vaguely remember having heard once that they expected that it would only take a mere 100-150 more years to get rid of mostly all WWI unexploded ordinances.
A similar example is North Africa. There are still not simply mines but whole uncleaned WWII minefields in Egypt.
Lest we forget:
.. for which locals must mostly thank, that most deserving recipient of the Nobel Peace Prize, Henry Kissinger.
Did any of those British “Tallboy” "earthquake bombs not go off?
You would not like one to explode near a building!
He designed them so they wouldn’t explode?
I wonder how much those unexploded WWI mines, bombs, and shells (of which there must have been much more of 70+ years ago) affected military operations during WWII?
The iron harvest has already been covered, but I did want to add a bit on the dumping of chemical weapons immediately off the shore of Belgium/the Netherlands. It’s amazing to me that there evidently hasn’t been a serious accident yet from these munitions. As the article notes, some chemical weapons payloads, especially mustard gas, are still very lethal after all of this time.
An interesting article (.pdf) by Mark Hiznay of UNIDIR on the failure rates of cluster munitions may be found here. The Congressional Research Service paper (also pdf) on cluster munitions cites heavily from it. This page is one demining company’s opinion on the relative dangers from different UXO types. Finally, the following page is a vast list of various publicly-available documents relating to UXO and AXO (Abandoned explosive ordnance. Simply, UXO’s been fuzed or otherwise armed, and then usually shot at somebody; AXO’s the stuff that got abandoned/dumped at the end of hostilities.) From it, in a partial answer to SirRay’s question, is the 1994 Field Manual 21-16, Unexploded Ordnance Procedures (.pdf). Basically, if a Soldier or Marine sees UXO, don’t touch it, mark where it is, and get an Engineer to deal with it. Just another trade-off between it being easier to dispose of the ordnance, or just finding another spot to place the fighting hole, bunker, etc. I am unaware of any large-scale disasters or other operational impediments during WW2 military operations from WW1 UXO, but it wouldn’t surprise me if there wasn’t an accident or two.
A digger driver was killed when his machine accidentally hit an unexploded bomb in Germany–and 8 others were injured.
So maybe you should keep your distance when digging is going on.