Collision at Anchor

Summary of the report:

The reporter’s vessel was at anchor, the weather was fine with good visibility, no strong current or abnormal wind/sea condition. The OOW noticed a vessel approached the anchorage making some strange manoeuvres. The reporter tried to contact the approaching ship on VHF but he didn’t receive any response, he then sounded several blasts on the whistle and called the captain. The vessel under way made contact with the anchored vessel and caused some scratches to the hull. The port authority was informed. The other vessel explained the contact was due to a problem with main engine.


A vessel under way is expected to keep clear of a vessel at anchor as a matter of good seamanship. [COLREGS Rule 2 (a)]. Similarly a vessel approaching an anchorage must do so
without endangering other vessels or anchor too close to other anchored vessels.
A recent Safety Alert Bulletin from a major tanker charterer was issued after they noticed a significant increase in the number of incidents involving contact with other vessels at congested anchorage locations, this in a few cases resulted in a breach of the hull. They identified causal factors and identified areas for improvement that they agreed we could share with others.

Causal factors identified:
• Bridge team’s failure to correctly assess the strength and direction of the local tidal currents 
and winds prior arriving, whilst at and manoeuvring in the anchorage;
• Manoeuvring own vessel too close to vessel(s) already at anchor;
• Lack of proper navigational watch keeping practices whilst at anchor;
• Swinging circle not plotted or used as a monitoring tool, especially during swinging of anchored vessels in different directions;
• Lack of monitoring clearances from adjacent anchored vessels during change of tide;
• Inadequate monitoring of prevailing weather and weather forecasts, such as local seasonal winds, thunderstorms, passing squalls etc., leading to dragging of anchor; and,
• Unavailability of vessel’s main propulsion for immediate use, when required.
Areas to focus on:
Vessel operators are encouraged to review their safety management system and provide adequate guidance to vessels considering the below points but not limited to:
• Pre arrival / departure planning in adequate detail (i.e. appraisal, planning, execution & monitoring) including contingency, and site-specific risk assessments;
• Evaluation of the prevailing congestion status at the port’s designated anchorages;
• Identifying a suitable anchorage position in consultation with Port Authorities / VTS prior to
entering the anchorage area;
• Whilst approaching an anchorage, avoid passing close ahead of other anchored vessels;
• Evaluation of adequate length of anchor cable to pay out with due consideration to the prevailing conditions, holding ground and sea depth, and
• Plot vessel’s swinging circle on GPS, paper chart and ECDIS if available. Ensure the vessel has adequate clearance to swing about the anchor. Once anchored, the actual swing pattern to be ascertained and ECDIS/Radar/GPS alarm limits adjusted if available.
• Swing tendencies of vessels in immediate vicinity should also be monitored, especially at change of tidal streams;
• Calculation and marking of tidal streams where applicable and in known areas for strong tidal effects;
• Maintaining robust anchor watch at all times including checking of vessel’s position at regular intervals;
• Echo sounder and anemometer limit alarms, where fitted to be re-adjusted as appropriate after anchoring;
• Monitoring of weather at all times and an action plan available, in case of unexpected adverse weather or anchored vessel’s swinging in different directions;
• Inserting a visual marker, on the windlass, to indicate any instances of the brake slipping;
• Maintaining vessel’s main engine in an appropriate state of readiness;
• Use of a Bridge Navigational Watch Alarm System (BNWAS), if available whilst at anchor;
• Clear standing instructions on calling the Master well in time, based on the developing situation specific to that anchorage location;
• Emergency contact list of local support services (such as pilot, tugs etc.) to be available at all times;
• Vessel operator’s internal navigation audit to include an evaluation of above best 
practices, whenever possible; and,
• Bridge Team Simulator training provided to deck officers and Masters that includes scenarios with weather changes, such as but not limited to:
– Approaching and anchoring in congested anchorages
– Dragging of own vessel in congested anchorage
– Other vessels at anchor dragging or maneuvering vessel drifting towards own 
 vessel at anchor, which could result in a contact incident.