By Alex Kirby
Environment correspondent, BBC News website
Munitions dumped off the British coast nearly a century ago are dangerously unstable now, a salvage expert says.
Out of sight but not out of mind
Michael Fellows, a former Royal Navy diver, says the weapons, jettisoned in the Irish Sea, are "liable to go bang".
He also believes a World War II wreck in the Thames estuary is "a ticking timebomb", which cannot be ignored.
Mr Fellows says the freighter, which was carrying munitions from the US, may threaten a liquid gas terminal due to be constructed on the coast of Kent.
Mr Fellows was speaking to BBC Radio 4's programme Costing The Earth, which has examined the risks posed by discarded weapons, wrecks and nuclear reactors in the waters round the British Isles.
One of the main concerns is Beaufort's Dyke, a deep submarine trench in the Irish Sea between Scotland and Northern Ireland, used as a munitions dump since early last century.
The Ministry of Defence says more than one million tonnes of weapons were jettisoned there, though some are known to have been dumped short of the Dyke in shallow coastal waters.
Mr Fellows, who has worked for 40 years in bomb and mine clearance and was decorated for his work during the Falklands War, now heads his own munitions clearance company, Fellows International.
He told the programme: "Most of the weapons dumped in the Beaufort's Dyke... weren't designed to go under water.
"There are sporadic explosions two or three times a month, I should think, in the Irish Sea, popping off all the time."
Asked whether the oldest munitions in the Dyke were losing their ability to withstand corrosion, Mr Fellows said: "Yes. They are getting old and they're liable to go bang."
A local councillor in Northern Ireland, Oliver McMullan, told Costing The Earth the Dyke contained sarin and tabun (both nerve gases), phosgene, mustard gas and explosives.
Incendiary bombs containing phosphate used to drift onto the shore each winter, said Mr McMullan.
"We had hundreds upon hundreds of these things getting washed up in a matter of days," he added.
"Out of the water, body heat will ignite them, or the heat of the sun, and then they just explode into flame.
"There was a couple of young boys here locally who got burns off them, and another in Scotland was burnt."
He fears the problem will worsen, telling the programme: "There's too much stuff down there that's only breaking up now."
Michael Fellows is also worried about the wreck of the US freighter Richard Montgomery, which sank with its cargo of high explosives in August 1944 off Sheerness in the Thames estuary.
He said: "It's a ticking timebomb. It's likely to go pop at some stage. Areas of Sheerness within about 3km (1.9 miles) will feel the effects.
"And they really ought to be worried about the new liquid gas terminal they're going to build 2.5km (1.5 miles) from the wreck."
He rejected the opinion of the government's Receiver of Wrecks, who was advised that munitions would not explode spontaneously but needed a trigger.
Mr Fellows said: "We can't afford to just leave it as it is. One option is to do a survey, or to de-ammunition it.
"Something needs to be done. We can't just afford to leave it for another 50 years."
The Department of Transport said the wreck of the USS Richard Montgomery was checked by divers once a year and that no ships were allowed to pass over the wreck.
A spokeswoman said this summer that the last examination, in 2003, showed the site to be no more dangerous than in the past.
The Costing The Earth programme also explores the possible risk from obsolete Royal Navy nuclear submarines moored at Devonport, and from the reactors of similar Soviet vessels lost at sea.