Operation Sandcastle

Operation Sandcastle was a United Kingdom non-combat military operation conducted between 1955-1956. Its purpose was to dispose of chemical weapons by dumping them in the Irish Sea.

The British possessed almost 71,000 air-dropped bombs of 250 kilograms in weight, each of which was filled with tabun. These had been seized from German ammunition dumps during the final months of World War II. A total of 250,000 tons of German chemical weapons had been discovered, the majority of which were destroyed because they comprised warfare agents which the allies already possessed in great abundance e.g. mustard gas. However, the stocks of tabun and sarin were considered more valuable because the allies did not possess nerve agent technology at that time. As a result, captured stocks of German nerve agents were divided between Britain and the United States after discussion, with the Americans taking the sarin. The British transferred their 14,000 tons of ordnance containg tabun in October 1945, via Hamburg and Newport, to temporary storage at the RAF strategic reserve ammunition store at Llanberis. Longer term facilities were prepared at RAF Llandwrog where the bombs were to be stored in stacks, out in the open, on the runways of the disused airfield. The intention was that any leaks of nerve agent would be carried out to sea by prevailing winds. The bombs were transported to Llandwrog by truck from August 1946 to July 1947.

In July 1947 it was discovered that the bombs were fuzed and a number of them were leaking nerve agent. The fact that the bombs had fuzes inserted meant that they were inherently unsafe: to reduce the risk of accidental detonation, standard practice is to avoid installing the fuze in any air-dropped bomb until shortly before it is loaded onto an aircraft to be used in combat. For similar reasons bomb fuzes are always stored separately, well away from bombs. Unfortunately, this was not the case with the 250 kilogram tabun bombs at RAF Landwrog. Not only had the bombs been left with fuzes inserted for a considerable amount of time (possibly years), but they were also left exposed to the elements creating a corrosion risk, together with the inevitable temperature fluctuations which resulted from changing weather. None of these factors were accepted practice regarding the safe, long-term storage of bomb fuzes or explosive ordnance in general.

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