$13 Million Cost to Remove Masts From WWII Wreck

The SS Richard Montgomery no longer has a mast. Crews completed the removal of the three rusting structures from the World War II shipwreck, a move designed to reduce the risk of a catastrophic explosion in the Thames Estuary.

The vessel ran aground on a sandbar off Sheerness, approximately 40 miles from London, in August 1944. It was one of 2,700 ships built in the United States to support the Allied war effort and was carrying munitions intended for use after the D-Day landings. The ship broke apart during salvage attempts and sank with an estimated 1,500 tons of explosives in its cargo holds.

For decades, the masts remained above the waterline, visible to local residents and passing vessels. Recent surveys indicated the structure was deteriorating, raising fears that a collapse could trigger a detonation. Nolan Conway, a naval architect with Florida-based Resolve Marine Group, explained that the vessel had begun to lean. He noted that some munitions are believed to have pressure fuses, meaning an impact could set them off.

Conway stated, "The fear is the masts could have fallen onto the cargo itself, causing it to detonate." The primary engineering challenge was cutting the masts without shaking the wreck or endangering workers. The team constructed a custom lifting frame to raise each mast vertically without swinging. They also deployed a remotely operated underwater diamond-wire saw, which used hydraulic arms to clamp around the masts and cut through them without requiring divers in the water.

U.K. maritime minister Keir Mather told the House of Commons this week that the project was finished ahead of schedule and on budget. The total cost for removing all three masts was just under $13 million, according to The Guardian. Mather said the masts had placed a significant load on the structure and that their removal supports long-term safe management of the site.

The explosives remain in place because removing them would carry considerable risks. Experts disagree on the scale of a potential detonation. Conway said estimates range from shoreline effects to a tidal wave traveling up the Thames, or a minor event that might only close a nearby shipping channel. He added, "There's a large range of impacts, but none of them are really 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 continue to be subject to continuous monitoring and control through that zone. The removed masts are expected to be preserved and have been moved to the Historic Dockyard Chatham museum for display.

The Montgomery and its cargo will remain where they came to rest, now entirely out of sight. The masts, which served as a familiar landmark for over 80 years, will be exhibited in recognition of the ship's role in supporting Allied forces during the war.