Twenty-one shipping containers were improperly stacked when they toppled into the ocean from a Young Brothers barge near Hilo Bay on June 22, the National Transportation Safety Board said in a recently released report.

In the 12-page report issued April 6, the NTSB found the probable cause for the incident was the company’s failure to provide the barge team with a plan when the barge was being loaded in Honolulu.

The NTSB found four stacks of 40-foot shipping containers were loaded almost exactly opposite of the proper way, meaning the heaviest were on top and the lightest on the bottom. They should have been loaded with the lightest on top, the NTSB said.

The lack of a load plan allowed the improper stacking to go undetected, and subjected the stacks to the forces of transit while crossing the ocean, the agency said. Also, the barge team had no procedures or calculations to determine whether the lashing would be sufficient with the reverse stacking.

Eight containers were found floating 3 miles off Pepeekeo Point and were recovered, but 13 were never found. The incident caused an estimated $1.6 million in losses, with $1.5 million in cargo loss, and $131,000 in damage to the barge and containers.

“Numerous barge team members stated that heavy containers could be loaded over light containers if some ‘heavies’ came into the yard after the lighter containers had already been loaded,” and they had loaded and secured the barge as they had in the past, the marine accident brief said.

One operator said they typically stacked containers five high, but a barge superintended said since the start of the COVID-19 pandemic, stacking was overall higher, but never above five high.

The Hoomaka Hou, a 340-foot-by-90-foot, flat deck, unmanned barge, was being towed by the tug Hoku Loa, with a crew of six, when a weather buoy off Hilo indicated “steep seas” with 6-foot waves 18 miles southeast of the tug.

So the tug officer on watch changed course at 2 a.m. and reduced the engine rpm to make the 4 a.m. arrival. Several crew members noticed the vessel tended to roll more on the Pepeekeo Point to Hilo leg, the NTSB said.

Unbeknownst to the tug crew, nearly half of the containers had fallen overboard at about 2:30 a.m. near Pepeekeo Point.

When the vessels pulled into Hilo Harbor at about 4 a.m., the tug captain was notified that containers had toppled over.

Once the barge was moored, personnel found the outside stack on the port side had gone overboard, and 16 on the starboard side disappeared.

“Young Brothers is proud of our record of safely and reliably transporting what matters most to Hawaii,” Chris Martin, terminal operations director, said. “We have implemented enhanced safety measures since our first loss of containers overboard in more than 20 years. We are carefully reviewing the report and considering the appropriate next steps.”

The company said it added safety protocols last year, increasing lashing arrangements that secure containers in place while in transit.

U.S. Rep. Kai Kahele, who is from Hawaii island, said, “The NTSB report clearly stated that the lack of an initial barge load plan and the failure to provide and implement adequate procedures for the monitoring of the cargo load was the probable cause of the container collapse.

“Young Brothers should implement enhanced safety measures as a result of this incident and work together with the barge team to ensure the safe loading of all of its vessels.”