Thames Wreck Engineering: Masts Removed for Under $13M

Local residents and shipping traffic in the Thames Estuary will no longer see three rusting masts rising from the water. The SS Richard Montgomery, a World War II cargo ship, remains grounded off Sheerness, but the tall vertical structures that marked its location for eight decades have been cut away. The physical footprint of the wreck has shrunk, though the cargo inside remains unchanged.

The Montgomery ran aground in August 1944, approximately 40 miles from London. It was one of roughly 2,700 vessels built in the United States for the Allied war effort. The ship was carrying munitions intended for use after the D-Day landings. During salvage attempts, the vessel broke apart and sank with an estimated 1,500 tons of explosives in its holds. For decades, the masts served as a visual landmark for locals and passing ships. Recent surveys indicated the structure was deteriorating, raising concerns that a collapse could trigger a detonation.

Nolan Conway, a naval architect with Resolve Marine Group, stated the vessel had begun to lean. He noted the primary fear was that the masts could fall onto the cargo and cause it to explode. Conway added that some munitions are believed to have pressure fuses, meaning an impact could set them off. His team faced the challenge of cutting the masts without shaking the wreck or endangering workers. They constructed a custom lifting frame to raise each mast without swinging. The team also employed a remotely operated underwater diamond-wire saw with hydraulic arms, allowing them to cut through the masts without sending divers into the water.

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

The explosives remain on the seabed because extraction carries considerable risk. Conway said expert estimates for a potential detonation range from shoreline effects to a tidal wave traveling up the Thames, or a minor event closing a nearby shipping channel. He described the range of impacts as broad but noted that none are favorable. Officials maintain that the overall probability of an explosion is low.

The masts have been moved to the Historic Dockyard Chatham museum for display. Mather said the site will continue to be subject to continuous monitoring through the existing exclusion zone, which lies about 1.5 miles off the Sheerness coast.

The wreck and its cargo now lie entirely underwater. The Montgomery will remain in place, with the government maintaining the control zone around the 1.5-mile radius.