The Bahamas Maritime Authority issued a Safety Alert sharing lessons learned from a grounding involving a RoRo passenger ferry after dragging anchor. The investigation highlighted that the crew had been forced to change the plan at short notice and no appraisal was conducted to select an anchorage position.
The incident
Due to congestion at the terminal, a Bahamas registered ro-ro passenger ferry anchored in the designated anchorage outside the harbour. With gale force winds from the north, the ferry anchored with four shackles on deck in 29m of water, approximately 0.7 nm due north of a charted (and buoyed) obstruction.
Within 11 minutes of letting go the anchor, the master declared the vessel brought up and handed over to the second officer when he returned from the focsle. Unnoticed by either of them, the vessel was dragging before the master left the bridge. The second officer remained on the bridge for the next 40 minutes, occasionally checking the vessel’s position by using the radar’s variable range marker against the land to the west.
10 minutes after taking over the watch, the third officer suspected the vessel was not in position and called the master who, after a delay, requested engines and sent an anchoring party forward.
An hour later, the vessel grounded on the charted obstruction, stern first, resulting in flooding to two compartments.
Safety Factors
- Having been forced to change the plan at short notice, no appraisal was conducted to select an anchorage position or range of cable suitable for the weather conditions, seabed characteristics or underwater obstructions.
- The ferry started to drag almost immediately; checks by the anchor party or bridge team were not robust enough to detect this.
- Successive watchkeepers failed to identify that the vessel was out of position – bridge resources were not fully utilised and the proximity to a charted obstruction was not incorporated into either handover.
- The vessel’s engines were not made available in time to manoeuvre the vessel clear of the obstruction.
- The ferry was drifting for over an hour before local VTS intervened.
Lessons learned
- A late change of plan can add significant stress to shipboard operations, including work and rest patterns. If this goes unrecognised, it is difficult to mitigate.
- Any change to the passage plan needs to be appraised: even a short term anchoring position needs to be carefully selected and the likelihood and consequence of dragging assessed. Dragging risk should inform the range of cable, monitoring frequency and engine readiness.
- All available means shall be used to determine the vessel’s actual and estimated position. The method in use must be verified against another means to ensure accuracy and prevent erroneous information.
- There are multiple ways to set automatic anchor/dragging alarms on the bridge equipment – settings need to be adjusted to avoid alarm fatigue whilst still providing adequate warning.
- VTS monitoring can only help avert casualties if it is proactive.
