Thames Wreck Masts Cut for $13 Million

Crews have removed the three masts from the SS Richard Montgomery, a World War II shipwreck in the Thames Estuary, at a cost of just under $13 million.

The SS Richard Montgomery was one of approximately 2,700 vessels built in the United States to support the Allied war effort. The ship struck a sandbar off Sheerness in August 1944, about 40 miles from London. It carried munitions intended for post D-Day operations. The vessel broke apart during salvage attempts and sank with an estimated 1,500 tons of explosives in its holds.

The masts had remained visible above the waterline for decades. Recent surveys indicated the structure was deteriorating. Engineers feared the spars could collapse onto the cargo and trigger a detonation. Nolan Conway, a naval architect with Resolve Marine Group, the firm contracted for the job, noted the vessel had begun to lean. He stated that some munitions are believed to have pressure fuses, meaning an impact could set them off.

The project required cutting the masts without shaking the wreck or endangering workers. The team built a custom lifting frame to raise each mast without swinging. They used a remotely operated underwater diamond-wire saw that clamps around the mast with hydraulic arms. This method allowed the crew to cut the masts without placing divers in the water.

U.K. maritime minister Keir Mather told the House of Commons this week that the complex project was completed ahead of schedule and on budget. Mather said the masts placed a heavy load on the structure and that removing them reduces that risk. The government has maintained an exclusion zone around the wreck, which lies about 1.5 miles off the Sheerness coast, and will continue to monitor the site through that zone.

The explosives remain in place because removing them carries considerable risks. Conway said estimates for a detonation range from shoreline damage to a tidal wave traveling up the Thames. He described the potential impacts as a large range of outcomes, none of which are good. Officials still judge the overall chance of an explosion to be low.

The removed masts have been moved to the Historic Dockyard Chatham museum. Mather said they will be displayed in recognition of the ship's role in supporting Allied forces during the war. The Montgomery and its cargo will remain where they sank, now entirely out of sight.