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U.S. Marines with Marine Wing Support Squadron (MWSS) 373, Marine Air Control Group 38, 3rd Marine Aircraft Wing, detonate C4 to demolish the Bailey Bridge as part of phase I of Strategic Mobility Exercise (STRATMOBEX) II at San Clemente Island, California, Jan. 5, 2024. During phase I, MWSS-373 demolished a hazardous bridge that hindered range control’s ability to insert targets into the Shore Bombardment Area of San Clemente Island. Phase I set conditions for phases II and III of STRATMOBEX II, the construct of a shallow water crossing and follow on missions. (U.S. Marine Corps photo by Lance Cpl. Jennifer Sanchez)

Photo by Lance Cpl. Jennifer Sanchez

3rd MAW Marines demolish 85-foot bridge on San Clemente Island

24 Jan 2024 | Gunnery Sgt. Stephen Himes 3rd Marine Aircraft Wing

MARINE CORPS AIR STATION MIRAMAR, Calif. – U.S. Marine Corps Col. John Ripley is legendary in the Marine Corps for his heroism in blunting a North Vietnamese offensive by destroying the Dong Ha Bridge during the Vietnamese War. As a Captain, Ripley labored for three hours to transport and attach 500 pounds of explosives to the Dong Ha bridge while under constant enemy fire by 20,000 troops and 200 tanks of the North Vietnamese Army. His courageous actions and the resulting bridge destruction are recognized as a key factor in the defeat of the NVA during the Easter Offensive in 1972.

More than 50 years later, U.S. Marines with Marine Wing Support Squadron (MWSS) 373, Marine Air Control Group 38, 3rd Marine Aircraft Wing, performed an explosive demolition of the Bailey Bridge on San Clemente Island, Jan. 5-7, 2024, during phase one of MWSS-373’s Strategic Mobility Exercise II.

“We wanted to practice and train under expeditionary advanced base operations concepts using a real-world scenario,” said U.S. Marine Corps Capt. Zach Adler, the MWSS-373 engineer company commander.

San Clemente Island is owned and operated by the U.S. Navy and hosts the Navy’s only ship-to-shore live firing range. In October 2023, Capt. Adler and Marines of MWSS-373 conducted a site survey on San Clemente Island to identify training opportunities. San Clemente Island range personnel were seeking assistance in removing and replacing the Bailey Bridge, which was eclipsing its service life due to corrosion damage. The Marines of MWSS-373 seized the opportunity to conduct a real-world bridge demolition.

“This mission provides San Clemente Island range personnel access to service targets in the impact area that 3rd Fleet uses for ship-to shore live fire training,” said Adler. “Contractors haven’t been able to service the targets in the impact area for years due to the bridge damage.”

The Bailey Bridge was a portable prefabricated bridge, which rested on two concrete abutments. The bridge was 85 feet long and wide enough to support two-way traffic. It crossed the China Canyon and provided San Clemente Island personnel access to the ship-to-shore live firing range, known as the Shore Bombardment Area (SHOBA).

Combat engineers and explosive ordinance disposal Marines cut the bridge from the concrete abutments and weakened structural members at critical stress points before using a sequence of controlled demolitions to collapse the bridge.

“We used the composition C-4 plastic explosives and TNT to destroy the weight-bearing points on the bridge to drop it into workable pieces,” said Chief Warrant Officer 2 Austin Sabin, the MWSS-373 EOD officer in charge. “M1 dynamite was used to destroy the buttresses, or reinforced concrete walls, holding up the bridge. Detonation cord was used to tie all the charges together to create a simultaneous detonation across the bridge.”

“The first and largest controlled explosion used approximately 275 net pounds of composition C-4 plastic explosives on key stress points to bring the bridge down,” said U.S. Marine Corps Master Sergeant James Arbuthnot, the MWSS-373 EOD chief. “Follow-on shots used less than 100 pounds of TNT on more critical points that the C-4 didn’t destroy.”

The use of more than 300 pounds of explosives to conduct a controlled destruction of a bridge requires significant professional planning, technical expertise, and consideration for safety and environmental factors.

“It was important to understand how the bridge was designed, where the weight-bearing points were, and appropriate type and number of charges needed,” said Sabin. “We also focused on safety by making continuous calculated risk-based decisions. Every time we acted on the structure, we reevaluated its stress, weight, position and possibility of critical failure.”

Once on the canyon floor, Marine Corps welders used an exothermic cutting system to cut the bridge into manageable sections for removal.

“Having the ability to work on such a large scale and important project, getting to share the experience with my junior welder and teaching him a new skill in the process, reminded me of the main reasons I chose to reenlist: to help guide and teach the next generation of Marines, said U.S. Marine Corps Cpl. Conlon Kane, a welder with MWSS-373.” Kane said the exothermic cutting system uses an electrical current to ignite a cutting lance. The steel rod is coated with specialized wax that aids in the continuation of burn after ignition. An electrical current ignites the rod and oxygen allows it to burn between 8,000 and 10,000 degrees Fahrenheit.

Phase one allowed the MWSS-373 team to integrate capabilities in support of a real-world operation benefiting the range personnel of San Clemente Island and set conditions for the next phase of MWSS-373’s mission. Marines will return to San Clemente Island this February to construct a shallow water crossing across the canyon.

The Bailey Bridge demolition also simulated what Marines might face in conflict, including the austere environment of the island. With limited communications, this was a step towards practicing distributed maritime operations and completing the mission based on commander’s intent.

“This mission offers extremely beneficial training opportunities for engineers, welders, and EOD, which prepared us for real-world distributed operations,” said Adler. “The shallow water crossing project in February will provide a great training opportunity for engineers to practice mobility operations on a smaller gap crossing. This also demonstrates the necessity for greater integration between combat engineers and EOD who will work together in the future fight.”

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