Human errors, mechanical woes caused Marine tank sinking that killed 9 off San Clemente coast

Left to Right, top row: Pfc. Bryan J. Baltierra, 19, of Corona, Pfc. Evan A. Bath, 19, of Oak Creek, Wis. Christopher Gnem, 22, of California. bottom row: Lance Cpl. Chase D. Sweetwood , 19, from Portland, Ore. Lance Cpl. Guillermo S. Perez, 20, of N

Inadequate training, shabby maintenance and poor judgment by leaders led to the sinking of a seafaring tank last year off Southern California that killed nine service members, according to findings of a Marine Corps investigation released Thursday.

The report detailed a slew of missteps and oversights that left the crew of the amphibious assault vehicle in the dark and using their cell phone lights to desperately try to find an unmarked escape hatch as they took on water.

"Ultimately this tragic mishap was preventable," wrote Lt. Gen. Steven R. Rudder, commander of U.S. Marine Corps Forces, Pacific, in his review of the investigation.

It was one of the deadliest Marine training accidents in decades. Three commanders have been dismissed as a result, including the leader of the 15th Marine Expeditionary Unit who oversaw the training exercise in the summer of 2020 off San Clemente Island, about 70 miles (113 kilometers) northwest of San Diego. Seven other military personnel faced administrative or disciplinary action.

RELATED: 9 service members killed in training accident off San Clemente coast

The training exercise was fraught even before it began. The investigation found inadequate training of the platoon members who were provided 14 amphibious assault vehicles that had not been used in more than a year and were in "poor condition." The platoon made repairs in a rush to meet a deadline, according to the investigation.

The Marines use the vehicles to transport troops and their equipment from Navy ships to land. The armored vehicles outfitted with machine guns and grenade launchers look like tanks as they roll ashore for beach attacks, with Marines pouring out of them to take up positions.

During the training exercise the vehicles were headed to a Navy ship after leaving the shores of San Clemente Island on July 30. One of the tanks with three crew members, 12 Marines and one sailor started taking in water shortly after 6 p.m.

A crew member alerted the vehicle commander who only responded "thanks, for letting me know," according to the investigation. The troops should have immediately been ordered to remove their gear and prepare to evacuate, according to military safety procedures.

The tank suffered numerous leaks, one of which was from a poorly installed headlight that left a gap in the hull area. There also was no oil in the transmission, according to the findings. The generator went out and the pump needed to flush out the water started failing.

As the water started rising above the troops’ boots, they should have gotten out but no such orders were given because the driver was on top of the vehicle waving a distress signal flag, which was not seen for more than 20 minutes.

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It took 45 minutes for the tank to sink and if the distress signal had been seen sooner, it’s likely rescuers could have saved the troops, the report stated. But there were no safety boats nearby.

As the water levels continued rising, the troops who had only trained on land remained inside the broken-down tank in seas that were rougher than expected, according to the findings.

They were not told to remove their helmets, weapons and other gear, which prevented them from being able to escape. Their life jackets also may have prevented them from removing their body armor and proved useless in keeping them afloat because of the weight, according to the investigation.

At least two of the troops had not completed their swimming certifications.

The emergency lights did not function and no markings were put on a side hatch, leaving troops scrambling in the dark, using their cell phone lights to find it, according to the findings.

Once they did, they struggled to open it, losing time. As they finally pried open the hatch, another assault vehicle came to rescue the crew and ended up colliding with the distressed vessel, which turned broadside into a wave that swept over it.

The troops were knocked off their feet and water flooded through the hatch and into the compartment, causing the vehicle to rapidly sink. Seven Marines and one Navy corpsman went down with the tank. An eighth Marine who was among those rescued later died.

The amphibious vehicle settled 385 feet (117 meters) below the surface on the ocean floor. After it and the bodies of the eight aboard were recovered, officials discovered that the vessel’s pyrotechnics — which are used to fire into the air as a distress call — had not been touched.

"These were outstanding young men and their loss is felt not just by their families but also by the scores of Marine and sailors with whom they served and on whom they left lasting impressions," Rudder wrote.

Rudder said the investigation will provide "little solace to the families" but he hopes it will prevent another such tragedy.

After the accident, the Marine Corps adopted stricter inspections for its fleet of amphibious assault vehicles, and a majority failed to meet the standards, the report stated.

The Marine Corps is calling for the problems to be addressed but said it believes the vehicles are safe when maintained and operated properly and called amphibious operations vital to the branch’s storied history. The report recommended a slew of changes from better training to requiring safety boats during exercises.

Col. Christopher J. Bronzi, the commander of the 15th Marine Expeditionary Unit, was let go Tuesday. Two other commanders were relieved in October. None could be reached for comment.