In its recent Good Catch series the American Club informs about a mooring line slack accident and provides lessons learned.
The incident
A general cargo vessel was moored at a facility to offload its cargo with its port side to the dock. The vessel was using its standard mooring line configuration with bow and stern lines, a forward and an aft spring line and 2 brest lines.
Anticipating that the vessel’s draft would be decreasing as the cargo was being offloaded, the Chief Officer had instructed that some slack be left in the mooring lines. He did not specify how much slack and did not check the mooring lines himself. The weather was mild with winds blowing at approximately 1-2 knots and there was no appreciable current at that dock.
Shortly after offloading began, a tank vessel passed by. The wake from the tank vessel caused the general cargo vessel to move pushing it into the dock then pulling it away from the dock while also sliding it forward. The movement was substantial due to the slack in the mooring lines.
The American Club notes that the mass of the vessel and the movement forward damaged the fendering system and created a series of scrapes along the vessel’s hull. The mooring lines were not damaged nor were the bollards on the dock. However, several of the large rubber fenders were torn from their mounts.
Probable cause
According to the investigation it was determined that
- the slack in the mooring lines was excessive for the circumstances,
- the Chief Officer’s attempt to save the crew some work tending the mooring lines was inappropriate.
The investigation also concluded that the tank vessel passed by at a reasonable speed and a reasonable distance from the general cargo vessel.
Damages and injuries
The damage was limited to the fender system on the dock and scrapes in the paint on the port side of the general cargo vessel. The unknown condition of the fender system prior to the incident created questions about whether the vessel was responsible for the damage or whether the fender system was in poor condition prior to the vessel arriving. The claim took over a year to resolve with the repairs and legal fees totaling over $96,000.
The American Club highlights that this incident could have been substantially worse. Had someone been standing or walking on the gangway at the time of the incident, they could have been seriously hurt. Although the mooring lines held as designed and intended, had one or more mooring lines parted, the vessel’s movement could have easily caused hull damage significantly more extensive than the paint scrapes experienced.
Lessons learned
In order to prevent and avoid such incidents, the following points should be taken into consideration:
- Mooring lines should always be conscientiously and diligently tended as cargo is loaded or offloaded, as the tide changes, and as wind and weather change.
- Time-saving shortcuts such as slacking the mooring lines in anticipation of cargo being offloaded should only be considered after an assessment of the associated risks and should only ever be done incrementally.
- The mooring plan should consider the likelihood of other vessels passing by in close proximity and the mooring configuration should be adjusted accordingly.
