200938 Dragging of anchor and collision

Dragging of anchor and collision
MARS Report 200938

Our vessel was anchored in a crowded inner anchorage with a current of up to two knots. A squall was observed approaching from the opposite direction of the tide. Own vessel contacted engine room to request engine and thrusters. As the squall passed, own vessel started to drag anchor. Fortunately the engine was started and vessel put into DP mode and successfully maintained position.

Among the other vessels in close proximity, a cargo vessel was observed to be dragging towards a tanker. Within 10 minutes, the two vessels had collided. During this period, nobody was observed on the bridge or the deck of the cargo vessel: only upon impact did crew members appear. On board the tanker the OOW had observed what was happening, however the engine was started late. But there was no pollution and no report was made to the port authority over the radio.
Lessons learned

An efficient lookout and watch must be maintained at all times at anchor.
Beware of dragging, especially when in an area of strong tides / current.
Have engines on short notice when in crowded anchorage.
Have contingency plans in place, especially in areas where squalls can be expected.
Report incidents to the port authorities promptly.