A long, fascinating, disturbing blog post at SciencePunk on unexploded munitions from both World War 1 and World War 2, still showing up unexpectedly:

The WMD was discovered, quite by chance, lying by the side of a Bridgeville road in late July by a Delaware state trooper on an unrelated callout. Jutting out of the ground, the 75mm shell was encrusted in barnacles and pitted with rust; barely recognisable as a munition at all. The trooper called in his find and a military team took the bomb to Dover Air Force Base for disposal. As with most conventional rounds, a small charge was placed on the side of the shell and detonated to trigger the vintage munition’s own explosive. But something went wrong, and the bomb failed to explode.

When the two staff sergeants and technician walked over to inspect the failed detonation, they found a strange black liquid seeping out of the cracked mortar. Given that the shell had been under the sea for the better part of fifty years, the men thought little of the foul-smelling substance until hours later, when their skin began to erupt in agonising blisters. All three were rushed to Kent General hospital, where two were released later after minor treatment. A third, more seriously injured serviceman was transported to Temple University Hospital in Philadelphia, where he remained in serious but stable condition with what were only described as “burns or blisters” in a statement issued by the Army later that week. A scientific team were sent to Dover to collect soil samples from the area. The results were clear: the shell had been filled with mustard gas. The United States’ forgotten weapons of mass destruction had returned to haunt it.

[. . .]

With three servicemen now lying in hospital, injured by a weapon of mass destruction, officials could no longer ignore the problem of the rogue munitions. On August 4, the U.S. Army announced a $6 million plan to locate and stem the source of the clamshell ordnance. The investigation was led by Robert Williams Jnr of the Army’s Corps of Engineers. It seemed like an impossible task – Williams couldn’t search every clamshell-topped road in the state, and even if he did, there’d be no guarantee he could complete the survey before one of the hidden weapons detonated. Worse still, nobody knew how the munitions were getting from the ocean into driveways, and how to stop more arriving. Then Williams was handed a gigantic stroke of luck: interviews with everyone who discovered ordnance in their driveways revealed that they had all purchased their clamshell mix from one hauler, Perry Butler. And Perry Butler had an exclusive contract to collect waste clamshells from one Milford clam processing plant: SeaWatch International.

As Delaware’s only clam processor, suspicion had already been placed on the Milford plant. In spite of initial claims that no ordnance had been found on site, when the U.S. Army turned their attention to the factory, it was already the subject of an ongoing investigation by the Occupational Safety & Health Administration. On inspecting the facility, their suspicions were confirmed: twelve munitions were recovered onsite. Workers had picked the highly unstable ordnance off the conveyor lines and stored them in a bucket of water in the basement. The munitions that they did not spot had been first plunged into conditioning tanks with the live clams, passed through steam cookers, and then raked across an industrial shucker that violently shakes the cooked meat from the shells. From there, the ordnance was picked up by Perry Butler, hidden in containers of empty clamshells, who passed them through a grinder that pulverised the shells into gravel before selling the fill on to various downstate residents. That none of the munitions exploded at any point was nothing short of miraculous. That no chemical rounds had broken open or leaked, even more so. SeaWatch International was fined $9,000 by OSHA for endangering staff and only permitted to continue business with the installation of $15,000 metal detector. Just three days later, the buzzer sounded. Workers reported the discovery of a 75mm shell, identical to the one that had injured three servicemen at Dover.

The problem is much bigger than the incidents in Delaware, however, as all the combatant nations of WW1 dumped their unused chemical weapons into the sea … and not always safely (and that really deserves scare quotes: “safely”).

With the close of the First World War, both defeated and victorious nations of the world were left holding thousands of tonnes of lethal chemical weaponry and no one to launch them at. The weapons were dangerous to transport and difficult to store. And nobody really knew how to neutralize their contents. So it’s easy to see how dumping the weapons in the deep ocean, out of harm’s way, was seen as a sensible solution. Entire ships were loaded with munitions, chemical and conventional alike, and sailed out to sea where the cargo was thrown overboard. As part of the CHASE program (“Cut Holes And Sink ‘Em), entire ships filled with weapons and unwanted hardware were scuttled, some detonating on their way to the seabed. For many decades, countries cast their surplus chemical weapons into ocean water and forgot about them. Over a quarter million tonnes of British bombs filled with mustard and phosgene gas and the nerve agent Tabun lie in the waters around the UK, concentrated off the west coast of Scotland. Somewhere between 50,000 and 300,000 tonnes of German, Soviet, US and British chemical agent lies in the shallow Baltic Sea. The USA has also admitted to dumping toxic materiel off the coastlines of other nations rather than risk carrying the volatile cargo home. The James Martin Centre for Non-Proliferation Studies lists 127 known dumpsites across the world, it’s likely even more exist.