DSB: Both Wadden Sea shipping routes at risk of losing containers
The Wadden area must be better protected against the loss of containers on the shipping routes that pass the islands to the north. During northwestern storm, both the northern and southern routes form a risk for large, wide container ships. This follows from a report about the MSC Zoe accident published by the Dutch Safety Board (DSB).
In the night of 1 to 2 January 2019, the MSC Zoe with more than 8000 containers on board was travelling from Sines in Portugal to Bremerhaven in Germany. North of the Dutch Wadden Islands, the MSC Zoe found itself in severe weather. The ship lost 342 containers. The cargo comprised a wide range of items and packaging materials that on the subsequent days washed ashore on the coastline of the Wadden Islands.
This occurrence caused the Dutch Safety Board to initiate two investigations: a combined international investigation with Panama and Germany into the course of events of the accident and an investigation by the Dutch Safety Board itself into the risks on the shipping routes north of the Wadden area.
Above the Wadden Islands there are two internationally designated shipping routes, a northern and a southern route. The MSC Zoe lost containers on the southern route. However, the investigation by the Dutch Safety Board has revealed that a combination of a number of phenomena means that on both the southern and northern shipping routes, there is a risk of loss of containers.
In storm-force northwesterly wind, vessels are confronted with high athwartships waves. As a consequence, large, wide container ships make extreme rolling movements. On the relatively shallow southern shipping route, there is also a risk of seabed contact (grounding) due to the combination of vertical and horizontal ship movements. Moreover, waves can slam against the ship, and seawater travelling at high speed along the side of the ship can be forced upwards against the containers. These phenomena, individually and in combination, cause extreme forces to act on the ship, the containers and the lashing systems used to retain the containers. As a consequence, containers can break free and be washed overboard.
High stability main cause of MSC Zoe accident
The investigation into the course of events has revealed that the MSC Zoe lost cargo at six locations. The extreme forces acting on the ship, the containers and the lashing systems as a result of specific conditions on this shipping route were the primary cause of the loss of containers. The crew did not notice the first containers being lost.
The MSC Zoe experienced four different hydrodynamic phenomena that played a role in the loss of containers: extreme motions and accelerations; contact or near contact with the sea bottom, green water and slamming. The main cause of the loss of containers was the high stability at which the ship was sailing in a beam sea scenario in shallow water conditions where it encountered the combination of the four hydrodynamic phenomena. The encountered transversal accelerations were at the design limits, leading to failure of the container structure and/or the lashing equipment and subsequent container loss.
The high stability condition made the ship more likely to show a higher roll response to the wave periods. The ships corrected GM of 9.01 metres, was typical for vessels of that size, states the Safety Board. The high stability leads to shorter natural roll periods, but these are closer to the wave periods present in the Wadden Sea at that time. This resulted in larger resonant roll motions in beam seas.
According to the Safety Board, high stability has not been recognised and formalised in the IMO Intact Stability Code and the effects of high GM are underestimated. Current limits are only set for a minimum GM.
MSC Zoe may have hit the seabed
It cannot be ruled out that the MSC Zoe also made contact with the sea bottom, says the Board. Basin tests have shown that when a group of relatively high waves is passed, the ship model experienced large vertical heave motions with a large roll motion at the same time. Although no damage was found to the bottom or bilge, the sandy sea floor may not have caused any while there was contact all the same. Such contact would cause vibrations and deformations propagated to the whole structure of the ship.
The crew also had no accurate way of measuring roll angles, forces and accelerations with just a mechanical inclinometer on board. This may have been another contributing factor.
No structural deviations of international regulations pertaining to lashing material and the lashing itself were observed. However, the Board notes that as the size of container ships continues to increase, the investigation revealed that the concept of lashing of containers on deck needs to be reviewed and internal technical and operational standards need to be amended or developed where necessary.
Recommendations by the Dutch Safety Board
Minimising the risks of container loss on the two shipping routes north of the Wadden Islands requires an integrated approach by the parties involved: the container shipping sector, the IMO and the Dutch government, according to the Board. The following recommendations have been made to the Minister of Infrastructure and Water Management:
- In collaboration with the Wadden states Germany and Denmark, take the initiative for a specific proposal to the IMO with measures for international container shipping to prevent the loss of containers on both shipping routes north of the Wadden Islands. This can for example take the form of a review of technical standards, the introduction of restrictions, recommended routes, precautionary areas, traffic control and/or information provision. Make particular use of the status of the Wadden Sea as a Particularly Sensitive Sea Area (PSSA) and the possibilities within the IMO standards for taking measures to protect a PSSA. Make use of the outcomes of this investigation and other investigations into route-specific risks (also see recommendation 5).
- Inform shipping companies and masters of large container ships in a structural manner about the four hydrodynamic phenomena that emerged from this investigation, which can occur in the event of high beam seas on both shipping routes north of the Wadden Islands. In providing this information, also make it clear that these phenomena and combinations of these phenomena can generate forces on large, wide and stable container ships which can result in the loss of containers.
- Grant the Netherlands Coastguard the tasks, authorities and resources it needs to monitor container ships so that ships can sail safely past the Wadden Islands in all wave and weather conditions. With this in mind, investigate the possibilities for traffic control of container ships, such as establishing a VTS area, actively disseminating warnings to shipping about prevailing weather and wave conditions in the Dutch part of the North Sea and innovating the way such information is provided. Involve the Netherlands Coastguard and Rijkswaterstaat in defining this role and responsibility. Also seek cooperation and/or harmonization with Germany on the intended tasks.
- Investigate the extent to which the route-specific risks of loss of containers on the shipping routes near the Wadden Islands as referred to in this report can occur on different types of container ships and in different meteorological and maritime conditions. In this investigation, include all incidents and other signals which could suggest other as yet unrecognized risks of loss of containers on the specific shipping routes.
- Make a periodic risk analysis of the route-specific risks that can lead to container loss on the shipping routes close to the Wadden Islands, with a view to the safety of shipping and protection of the North Sea and the Wadden area, and include this analysis as a fixed element of North Sea policy. Under all circumstances, make use of a system of monitoring and analysis of shipping incidents and near misses on these shipping routes. Also include developments in shipping such as economies of scale, changes in the picture of shipping traffic and (future) changes to infrastructure and area activities on the North Sea.
Recommendations from the international investigation
The international report makes recommendations to the Panamanian, German and Dutch governments to review the technical requirements imposed on container ships in an IMO context. More specifically, this concerns:
- the design requirements for lashing systems and containers,
- the requirements for loading and stability of container ships,
- obligations with regard to instruments providing insight into roll motions and accelerations, and
- the technical possibilities for detecting container loss.
Recommendations are also made to the German and Dutch governments to investigate, in cooperation with Denmark, the need for additional measures on these shipping routes or adjustments to the routes and to submit a proposal to the IMO on the basis thereof. In addition, the shipping company of the MSC Zoe is instructed to explicitly draw the attention of crews sailing in this area to the route-specific risks, and to equip and load their ships in such a way that the loss of containers is prevented.