Masts Stripped From Thames Wreck in $13 Million Operation

The SS Richard Montgomery now sits entirely beneath the surface of the Thames Estuary. Three rusting masts that had poked above the water for eighty years were cut away this week. The shipwreck still holds a massive cache of explosives, which remains undisturbed on the riverbed.

The U.S. Maritime Administration vessel ran aground in August 1944 near Sheerness. It was one of roughly 2,700 ships built in America to support the Allied war effort. The Montgomery carried munitions intended for use after the D-Day landings. It broke apart during salvage operations and sank. An estimated 1,500 tons of explosives are trapped in its cargo holds.

Nolan Conway, a naval architect with Resolve Marine Group, led the removal effort. Conway told CBS News that the vessel had begun to lean. He explained that engineers feared the masts could fall onto the cargo and cause a detonation. Some of the munitions are believed to have pressure fuses, meaning a hard impact could trigger an explosion.

The team built a custom lifting frame to raise each mast without causing it to swing. They also used a remotely operated underwater diamond-wire saw to cut the masts at the waterline. This tool clamps around the mast with hydraulic arms and passes a saw through the metal. No divers had to enter the water to perform the cuts.

U.K. maritime minister Keir Mather told the House of Commons that the project was completed ahead of schedule. The total cost was just under $13 million. Mather stated that the masts placed a heavy load on the structure. Removing them reduces that risk and supports long-term safe management of the site.

Officials are keeping the explosives in place because removing them would be dangerous. Experts disagree on what a detonation would cause. Conway said estimates range from damage to the shoreline to a tidal wave traveling up the Thames. Other estimates suggest the event might only close a nearby shipping channel. He noted that none of the potential outcomes are good. Officials still judge the overall chance of an explosion to be low.

The government maintains an exclusion zone around the wreck, which lies about 1.5 miles off the Sheerness coast. Mather said the site will remain under continuous monitoring through that zone. The three removed masts have been moved to the Historic Dockyard Chatham museum. They will be displayed there to recognize the ship's role in the war.