First World War munitions at bottom of North Sea leaking TNT

Munitions in the undersea dumping site off the coast of Knokke-Heist are leaking TNT, according to the Royal Belgian Institute of Natural Sciences (RBINS).

The 35,000 tons of unexploded munitions are in a site of three square kilometres on the sandbank known as the Paardenmarkt, about one kilometre off the coastline.

Following the First and Second world wars, many European countries isolated chemical weapons, often sealing them cement-filled containers, and dumped them in the ocean. This was thought to be the safest spot to dispose of them.

Belgium sunk unexploded munitions containing mustard gas and TNT in the North Sea, off the coast of Knokke. The dumping site contains mostly German munitions from the First World War.

The water in the area is regularly tested for the presence of chemicals, and TNT was recently detected for the first time. Het Laatste Nieuws broke the story yesterday, and it was confirmed by the RBINS in Brussels.

The containers have sunk into the silt at the bottom of the seabed, where they are buried about a metre deep. Flemish MEP Mark Demesmaeker (N-VA) told Het Laatste Nieuws that he would like to see the containers brought up and stored safely elsewhere.

According to the RBINS, the TNT is in such low concentrations and so far out to see that it poses no danger to swimmers. It’s already illegal to fish or toss an anchor in the three-kilometre site.

“The amount measured was extremely low, about 1 microgram per kilogram, just at the amount that becomes detectable,” said Fritz Francken of RBINS. It could, however, be harmful to the marine environment, including seaweed, fish and shellfish.

“The measuring technology has improved, which is why the TNT is now detectable,” Demesmaeker told VRT. “It is in a very low concentration, but we don’t know for sure how long the munitions have been leaking.”

Demesmaeker submitted a proposal to the European Commission last year to create a pilot project to salvage munitions that have been dumped in Europe’s oceans. “Up to now, it’s always been the general consensus that we should leave it alone,” he said. “But sooner or later, it’s going to be necessary to bring it up. There’s not just TNT, but phosphorous and mustard gas down there. We need to know what kind of condition these munitions are in and assess how to salvage it safely and efficiently.”

Photo: The Paardenmarkt sandbank (in red) contains 35,000 tons of chemical weapons ©Courtesy VRT