Chris Horn: Is there a safe way to get rid of unexploded ordnance under the sea?

The Beaufort trench between Ireland and Scotland is one of the largest dumps worldwide for unexploded ordnance

Over the last year, I have become an occasional driver from Cairnryan ferry port in Scotland. Two hours and 120km later, the single lane road at last skirts Dumfries via its innumerable roundabouts, before yet another hour and eventually on to the M6 motorway at Gretna Green.

The endless bóthar absorbs Scottish allure while drivers lumber along behind a heavy freight truck, or dawdle in a long queue behind a farm tractor. The gentle serenity contrasts with the hustle of the M11/M50/M1 motorway near home which brings me the 200km to Belfast ferry port in just two hours.

The trek highlights the dichotomy between the fervour of Northern Ireland’s unionist politicians for frictionless integration with the UK and the weak physical infrastructure on the Scottish side. Cairnryan should be a significant economic gateway. But the roads north to Glasgow and east to Carlisle are unsuited to any reasonable level of freight traffic.

The old military railway connecting the port to Stranraer is long gone, and Stranraer itself has just a sporadic connection north to Glasgow.


Boris Johnson, when prime minister, did propose a bridge to connect Scotland and Northern Ireland. However, the waters off southeast Scotland run relatively deep. The Beaufort Dyke depression is 50km long and the 300m depth even facilitates submarine exercises by the Royal Navy.

In November 2018, the Stena Superfast ferry, which I now use, had to take evasive action when a periscope appeared just a couple of hundred metres away on a collision course. The subsequent inquiry ruled that the submarine’s commander had badly misjudged both the ferry’s range and speed.

The Beaufort trench is also one of the largest dumps worldwide for unexploded ordnance. The UK ministry of defence estimates that, since the 1920s, over a million tons of surplus conventional and chemical weapons have been discarded there – or in the vague vicinity. Unsurprisingly, some of the dumping crews offloaded their highly dangerous cargoes at their first opportunity, without necessarily waiting to reach their designated drop areas.

Johnson’s proposal was consequently (dare I say?) torpedoed.

Some of the ordnance and chemical weapons have now been submerged for 100 years. Climate change is leading to warmer seas and increasing acidity, both of which increase corrosion. Explosive materials such as TNT and its variants are extremely toxic to marine organisms.

A comprehensive study by the University of Aberdeen back in 1995, which at the time found no evidence of food chain contamination from the Beaufort trench, should be redone.

Of course, the Beaufort dyke is only one of many maritime dumping sites for munitions. The areas off the German coast and in the Baltic Sea are even larger, with an estimated two million tons of unexploded conventional and chemical ordnance in German waters alone.

In some areas, there is only 30 metres of depth. The region around the Danish island of Bornholm, close to the Nord Stream pipelines, is one of the most heavily littered with ordnance. Corrosion or acoustic vibration of dumped munitions could perhaps have caused the pipeline explosions last year.

There are various records of locations and types of munitions dumped, although Russian record-keeping, in particular, was apparently weak. But in any case, sea floor munitions can and do move due to currents and storms, which are increasingly stronger with climate change.

Political pressure is increasing to try to clean the Baltic and German sea beds. The EU-funded Basta project developed ultra high-resolution 3D maps of sea floor ordnance by using untethered autonomous vehicles with video cameras and magnetic sensors. A separate EU ExPloTect project used spectrometers to very rapidly analyse chemical traces found in sea samples close to suspect munitions.

But once the current location of a dangerous undersea ordnance is identified, then what?

Recovering a corroded munition from the sea floor is usually highly dangerous, potentially resulting in complete disintegration or uncontrolled explosion. Forcibly detonating them is also discouraged, due to the acoustic shock to marine life and the potential for residual chemical leakage.

Instead, undersea deflagration is gaining acceptance. A small shaped charge is placed on to the munition casing, and activated to cause the explosive inside the munition to rapidly burn away without causing an actual detonation.

There is obvious danger in having a diver scrape a portion of the casing clean of marine growth and then attaching a deflagration charge, even assuming the sea bed is reachable. Ideally, a remotely operated vehicle should instead perform the process. A small number of firms are innovating low-order deflagration technology for undersea ordnance, including Alford, Eodex and ECS in the UK, Germany’s Atlas Elektronik and Hydroid in the United States.

Climate change is exacerbating a legacy from previous generations. I believe that political attention in the EU is opening up a market for creative solutions to dumped ordnance. But I wonder whether the UK will follow, and invest in regions hitherto quietly ignored, both on land and at sea.