Image ID P630TT Visible masts of the wreck of SS Richard Montgomery, an American Liberty ship built during World War II CREDIT Jason Richardson Alamy Stock Photo EXP 141223
Visible masts of the wreck of SS Richard Montgomery protude from the Thames Estuary (Picture: Jason Richardson / Alamy Stock Photo).

The 'Doomsday wreck' packed with 1,400 tonnes of explosives that could create a tsunami in the Thames Estuary

Image ID P630TT Visible masts of the wreck of SS Richard Montgomery, an American Liberty ship built during World War II CREDIT Jason Richardson Alamy Stock Photo EXP 141223
Visible masts of the wreck of SS Richard Montgomery protude from the Thames Estuary (Picture: Jason Richardson / Alamy Stock Photo).

Since 1944, the people of Sheerness in Kent and Southend-on-Sea in Essex have been living near 1,400 tonnes of unexploded ordnance – enough, some say, to create a tsunami. 

The sunken wreckage of SS Richard Montgomery, nicknamed the 'Doomsday wreck' by Medway Council in 2012, has become an unlikely tourist attraction. 

Fascinated visitors to the Thames Estuary location see the masts of the submerged ship poking out from the choppy water, knowing that beneath the surface lies 1,400 tonnes of explosives. 

Image ID HH4GN1 American Liberty Ship Advance Transport CREDIT Chronicle Alamy Stock Photo EXP 141223
An example of a US Liberty Ship (Picture: Chronicle / Alamy Stock Photo).

A publication on from Medway Council said: "Government tests on the site as far back as 1970 suggested a blast would hurl a 1,000ft wide column of water, mud, metal and munitions almost 10,000ft into the air—risking the lives of wildlife and many people." 

In January 2022, the weekly science and technology online and print publication 'New Scientist' asked researchers at Defence Research and Development Canada to assess just how much damage the SS Richard Montgomery wreck might cause if the munitions were somehow set off, and the findings were sobering. 

It said: "A blast on this scale would be one of the world's biggest non-nuclear explosions, causing widespread destruction and death." 

SS Richard Montgomery 

US Liberty Ship SS Richard Montgomery was built just a year before she sank, in 1944, by the St John's River Shipbuilding Company of Jacksonville in Florida. 

It was named after Irish-born Brigadier General Richard Montgomery, a hero of the American Revolution for his service to his country. 

President Franklin D Roosevelt claimed the ships, built to carry vital supplies for the war effort, would help bring "liberty" back to Europe. 

Other Liberty Ships were SS Harriet Tubman, named after the American abolitionist and human rights activist, SS Patrick Henry, named after the Founding Father, SS Robert E. Peary, named after the American explorer and US Navy officer and SS Stage Door Canteen, named after the segregation-free, armed forces-focused, entertainment club in New York. 

SS-Richard-Montgomery-Survey-Report-2021-SSRM overview from the north west-CREDIT-Maritime-Coastguard-Agency
SS Richard Montgomery overview from the north west (Picture: Maritime Coastguard Agency).

What happened to SS Richard Montgomery? 

During the summer of 1944, SS Richard Montgomery sailed from America to the UK as part of convoy HX-301 with a cargo of about 7,000 tonnes of munitions. 

When she arrived in the Thames Estuary on 20 August 1944, the vessel was directed to anchor in the Great Nore Anchorage, off Sheerness. 

However, due to a force 8 gale, the ship's anchor dragged in shallow water causing the vessel to drift onto a bank. 

The ship grounded amidships on the crest of the bank causing it to break its back due to a weak spot in her design. 

Over the next month, several thousand tonnes of ordnance were carefully removed from the ship.

The salvage effort only stopped when the vessel flooded completely – leaving 1,400 tonnes of explosives submerged in the Thames Estuary. 

The wreck now lies one-and-a-half miles from Sheerness and five miles from Southend-on-Sea in water about 15 metres deep, with its masts always protruding. 

The wreck is designated under section 2 of the Protection of Wrecks Act 1973, meaning there is a no-entry exclusion zone around it.  

Peel Ports London Medway – the historic ports of Sheerness and Chatham combined together – is contracted to provide and maintain a circle of buoys around the wreck to ensure that shipping avoids the area and to keep the wreck site under 24-hour radar surveillance. 

SS Richard Montgomery map CREDIT BFBS
A map showing the location of SS Richard Montgomery.

What is still on SS Richard Montgomery? 

There are three types of bombs thought to be on board: un-fused TNT bombs, about 800 fused cluster bombs and some smoke bombs – quite a combination that might make even the hardiest of people raise an eyebrow. 

However, a March 2000 report on the wreck of the SS Richard Montgomery stated: "TNT does not react with water and is extremely stable, particularly if stored at a steady, low temperature. 

"As it has been contained in metal bomb cases there has probably been little change in its chemical or explosive properties as a result of the long period of immersion." 

The report also investigates initial concerns after the vessel sank over "the possibility of the formation of very sensitive copper compounds from reaction between the lead azide in the detonators with the brass components of the fuses of the cluster bombs" and reveals why they were "no longer considered to be a significant hazard" by 2000. 

Turns out the flooding of the wreck has proved helpful in reducing the threat of explosion from the cluster bombs. 

"As the fuses will probably all have been flooded for many years, and the sensitive compounds referred to are all soluble in water, this is no longer considered to be a significant hazard," the report added.

However, while the white phosphorus filling of the smoke bombs is stable underwater, it is capable of spontaneous ignition if exposed to the air. 

What is the risk of an explosion? 

In a House of Lords debate in July 2019, to ask what action the Government is taking to mitigate the risks posed by the wreck, Lord Harris of Haringey explained that, in 1970, the Royal Military College of Science prepared an assessment of what would happen if the entire remaining cargo were to explode. 

He said: "A 3,000 metre-high column of water and debris and a five metre-high tsunami. 

"This would overwhelm Sheerness, and the water wave, possibly carrying burning phosphorus, would reach the petrochemical installation on the Isle of Grain." 

However, others at the debate questioned whether it would be worth the cost seeing as it has been reported that disturbing the wreck could be dangerous. 

Lord Greenway said: "Some people have proposed either moving the whole wreck, which would be well-nigh impossible, or just removing the munitions. 

"The latter course has been estimated to cost tens of millions of pounds and would probably involve the evacuation of Sheerness. 

"On balance and in conclusion, I tend to follow the line... that we should leave well alone but continue to monitor closely the gradual degradation of the wreck." 

SS-Richard-Montgomery-Survey-Report-2021-Crack in Hull September 2021 CREDIT-Maritime-Coastguard-Agency
A crack in SS Richard Montgomery's hull in September 2021 (Picture: Maritime Coastguard Agency).

The March 2000 report states that up until that point, and still the case 22 years later, the damage to SS Richard Montgomery and its precarious position in a major shipping route, hasn't caused any explosions. 

The report also states that, if nature is allowed to take its course, the wreck will break up naturally and that during this process "the ordnance will get wet... and will become neutralised". 

"Even if the water has not already rendered them inert, a small explosion at any distance from the wreck will not set off the bulk of the cargo." 

However, the report is clear to point out that the wreck should not "be disturbed by moving it or attempting to unload it" – doing so might increase the chance of explosions. 

The report states that "the risk of a major explosion is believed to be remote and is probably becoming even less likely with the passage of time". 

However, what happened to the wreck of the Polish-operated cargo ship SS Kielce in 1967 has left people concerned. 

Image ID W21X7Y SS Richard Montgomery lying 1.5 miles north of Sheerness and containing 1400 tonnes of explosives CREDIT James Bell Alamy Live News EXP 141223
A small boat speeds past the masts of SS Richard Montgomery at low tide (Picture: James Bell / Alamy Live News).

It sank in the English Channel near the coastal town of Folkestone following a collision in 1946.

Even though no cargo manifest has ever been traced, it is reported that the ship had a full cargo of bombs and ammunition. 

To clear the wreck, the Folkestone Salvage Company set off explosions on 22 July 1967, the third of which, according to the March 2020 report, "brought panic to Folkestone's town and chaos to the beaches". 

The March 2000 report on the wreck of the SS Richard Montgomery also stated: "Chimneys were damaged, slates dislodged and ceilings were cracked, but no case of personal injury was reported." 

It was reported that two members of staff from the Folkestone Salvage Company were in a small boat near the wreck when the explosion occurred and reported "a small ripple and some spray". 

However, other reports state that a "tidal wave" hit the Folkestone beaches, causing some to successfully claim for property damage on Folkestone beaches. 

Image ID P630TT CROPPED Visible masts of the wreck of SS Richard Montgomery, an American Liberty ship built during World War II CREDIT Jason Richardson Alamy Stock Photo EXP 141223
A sign at the wreck location warns people to "not approach or board this wreck" (Picture: Jason Richardson / Alamy Stock Photo).

In cases like these, it's useful to check what data was recorded at the time. 

The March 2020 reports states: "The seismic effects of the explosion had been recorded by at least 25 observatories, throughout Europe and America, out to a distance of nearly 5,000 miles from Folkestone and, from these records, using techniques which were developed for cataloguing the severity of earthquakes and other seismic disturbances, a magnitude of 4½ ± ½ was allocated to the explosion." 

With all the information gathered since 1946, many believe it is considered more dangerous to attempt to remove the remaining explosives than leave the submerged wreck alone. 

However, SS Richard Montgomery has been deteriorating for 78 years, meaning that there is a possibility that structural failure might occur.  

In 2000, the Defence Evaluation and Research Agency concluded that the likelihood of a major explosion is remote but that as time passes, the deterioration of the wreck could shift the risk towards a "let's deal with this now" level of urgency. 

SS-Richard-Montgomery-Survey-Report-2021-Density plot of surrounding seabed MBES survey CREDIT-Maritime-Coastguard-Agency
The density plot of the surrounding seabed (Picture: Maritime Coastguard Agency).

The conclusions in 2000 were as follows:  

1) Masts and derricks must remain where they are. They will be removed at the start of 2023, much to the despair of tourists who like to see them. 

2) Continue to keep the wreck under close observation. The wreck is under 24-hour surveillance by Medway Vessel Traffic Monitoring Service. 

3) Monitor the seabed around the wreck in an annual survey. High-resolution multibeam sonar surveys of the wreck have been undertaken on a regular basis since 2002. The SS Richard Montgomery survey report in 2021 stated that "no significant changes had occurred" since the preceding survey in 2020. 

4) Complete risk assessments that "consider cost, environmental impact and risks to stakeholders in the event of explosion". 

5) Remove the veil of secrecy surrounding the wreck and keep information about it in the public domain. 

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