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Vessel collision with underwater objects in harbour

What happened

A vessel suffered underwater damage to the hull when it collided with uncharted objects in the harbour. The incident occurred after completion of cargo operations when an AHTS vessel cast off from the quayside for departure. While proceeding towards the harbour channel and leaving the mooring buoys on its port side, crew on the vessel felt a blow to the vessel. Immediately the crew went to check for damage and found out the vessel was holed – seawater was coming in. The authorities were informed and the vessel returned to the quayside. The vessel had to be dry-docked for repairs.

What went wrong

The vessel collided with uncharted underwater harbour pilings.

What was the cause?

  • There were no proper navigational markings – the piles were not marked with floating buoys;
  • The most recently updated charts for the harbour, provided by the authorities six months before this incident, did not reflect the exact co-ordinates of the underwater piles;
  • The pile height and the water depth information provided on the chart did not match the “under keel clearance” calculation done by the bridge crew on the vessel.

Additionally, our member noted that:

  • There was a warning in place: a recent local notice to mariners was given with general coordinates for an area in the harbour without any coordinates identifying the underwater piles. The notice did warn all vessels to be “careful in this area” but did not restrict entry to it;
  • Comparison of the coordinates where the collision took place, with underwater pile coordinates subsequently obtained by the company, confirmed absolutely that the vessel hit one of the piles.

What happened next?

  • Bridge crew should calculate “under keel clearance” considering draft versus water depth, height of subsea objects, vessel stability, weather conditions and squat effects when navigating through a potentially hazardous area;
  • If possible, avoid navigating through areas for which notices to mariners or similar warnings are in place. If there is no option but to do so, it may be appropriate to seek shore-side management approval.

Members may wish to refer to

Safety Event

Published: 23 November 2022
Download: IMCA SF 26/22

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