A partly laden tanker was proceeding inbound along a narrow river channel with a pilot on board. The transit was taking place in the early morning hours on a flood tide.
Shortly before entering a stretch of the channel with occupied river berths, the pilot ordered the vessel’s speed to be reduced from full ahead to half ahead. After passing the berths, the speed was again increased to full ahead.
Later that day, the tanker’s Master received notice that his vessel was alleged to have caused wash damage to a bulk carrier alongside one of the river berths due to proceeding at excessive speed. The damage included the destruction of the accommodation ladder and the parting of a number of mooring ropes due to the bulk carrier ranging forward and aft when the tanker was passing.
It was determined that the tanker’s speed at the time of passing the berths was about 9.5 knots whereas port regulations imposed a speed limit of 7 knots in this stretch of the river.
Although the tanker was proceeding along the middle of the channel, its relative narrowness meant that vessels alongside the river berths could potentially be affected by the wash of other vessels passing at excessive speed. The engine revolutions could have been reduced earlier to comply with the regulatory speed limit thus lessening the wave disturbance generated by the vessel’s movement.
Although the pilot stated concern that a lower speed could adversely affect manoeuvrability as the vessel was trimming by the head due to squat, the effect of such interaction with the ground would decline with a reduction in speed.