The National Transportation Safety Board (NTSB) has published an investigation report into an incident where 23 shipping containers were lost overboard the containership President Eisenhower.
The incident
On 6 February , 2024, about 2135 local time, the US-flagged containership President Eisenhower was drifting about 94 miles south of Oakland, California, while awaiting a berthing assignment, when the crew discovered that 23 shipping containers had been lost overboard. None of the lost containers carried hazardous materials. There were no injuries, and no pollution was reported. Damage to the containership and the value of the lost cargo was estimated to exceed $735,000.
Analysis
On 6 February, the containership President Eisenhower was drifting in the Pacific Ocean about 94 miles from the Port of Oakland when the crew discovered 23 shipping containers from bay 42 were lost overboard. The crew subsequently discovered an additional 10 containers were damaged. Four days before the casualty, longshoremen had loaded containers in bay 42 in accordance with a cargo loading plan developed by ship planners using the VGM of each container provided by the booking agent.
However, after the casualty, the booking agent found that an administrative error—wherein the cargo weights for 39 containers were inputted incorrectly—resulted in the VGMs for those 39 containers being significantly underreported on the cargo loading plan. The actual VGM for the 39 containers was 18.3 to 22.2 metric tons greater than the VGM used to develop the cargo loading plan. Of these 39 containers, 20 were loaded in stacks on the hatch covers in bay 42. Ten of the containers with an incorrect VGM on the cargo loading plan were loaded on the port side of bay 42, where the container loss occurred.
The actual weight of these ten containers was between 25.1 and 28.3 metric tons, leading to container stack weights that exceeded the maximum stack weight limit in the operating company’s CSM by up to 26% (see table 1). Because the cargo loading plan for bay 42 included inaccurate VGMs, the stack weights exceeded the CSM’s allowance, and the forces acting on both the containers and the cargo-securing equipment were greater than what was expected.
Additionally, since the container VGMs were incorrect on the cargo loading plan, the container stacks on the port side of bay 42 were inadvertently arranged with heavier containers in the upper tiers and progressively lighter containers toward the bottom tiers—an arrangement called reverse stratification. This arrangement resulted in the stacks having a higher center of gravity than stacks arranged with the heaviest containers on the deck and progressively lighter containers above—referred to as normal stratification.
Normal stratification is preferred because it creates a container stack with the lowest possible center of gravity. The cargo securing equipment (twist locks and lashings) on a reverse-stratified container stack would be subjected to increased forces from vessel motion while underway at sea. Therefore, the loading of containers in overweight and reverse-stratified stacks in bay 42 increased the likelihood of a cargo-securing equipment failure. After the casualty, the booking agent modified their procedures and booking system to prevent this type of input error from occurring in the future.
Because the cargo loading plan was created using inaccurate data, it showed—incorrectly—that the stack weights on the port side of bay 42 were within the maximum total stack weight limitations prescribed in the operating company’s CSM. The VGM of the containers was not verified at the terminal, and there were no issues during the loading operations. Additionally, before departure, the recorded draft was within the 0.2 meters (0.7 feet) of acceptable variance, or “correction factor,” when compared to the calculated draft in the cargo loading and stability software.
The expected mean draft from the cargo stability and loading software when the President Eisenhower departed Los Angeles was 9.62 meters (31.6 feet) with a calculated displacement of 72,351 metric tons. In this loading condition, the vessel’s tons per centimeter immersion was about 93 (meaning it would take an additional 93 metric tons of weight to increase the vessel’s mean draft by 1 centimeter). Due to the underreported container weights in the cargo loading plan, there were about 835 metric tons of additional cargo not accounted for in the draft calculations (415 metric tons above the hatch covers in bay 42, and a maximum of about 420 metric tons of additional cargo loaded in cargo holds of bays 42 and 30).
Based on the loading conditions, the additional cargo weight would have increased the President Eisenhower’s mean draft by about 9 centimeters, or .09 meters, and resulted in a calculated mean draft of 9.71 meters (31.9 feet). This was closer to the recorded mean draft of 9.75 meters (32.0 feet) before the vessel departed Los Angeles, but the difference was still within the allowable correction factor of 0.2 meters. As such, there were no indications that the container stacks in bay 42 were overweight during loading operations or while preparing to depart from Los Angeles.
After the casualty, the vessel operator found that the overweight and reverse-stratified container stacks exceeded the calculated “lashing forces,” which caused the cargo-securing equipment to fail.
As loaded upon departure from Los Angeles, some stack weights for bay 42 would have exceeded the CSM’s maximum allowable stack weight, and if known, the vessel would not have been able to sail. Despite this, the vessel successfully transited from Los Angeles to Oakland (underway about 4 days) without issue. Additionally, about 1000, after the vessel arrived outside the Port of Oakland, a crewmember had inspected the containers’ lashings and found nothing amiss. Throughout the day, the vessel drifted while awaiting entrance to the Port of Oakland, and increased wind and seas caused the vessel to roll at 18º.
The weather and sea conditions did not meet the adverse weather thresholds as defined in the operating company’s SMS, and there was no roll limit prescribed in the SMS, CSM, or onboard route monitoring software, so the crew took no action to address the rolling. However, the 18º rolls were significantly higher than what the vessel had previously encountered on the transit (reported at a maximum 5º). After the casualty, the classification society found lashing plate and socket damage, indicating that the lashings became overloaded and pulled free.
The increased rolling magnitude from seas would have increased the compression forces acting on the containers within the stacks and the racking forces acting on the cargo-securing equipment until the equipment failed, resulting in the container damage and loss.
