An ice-strengthened oil exploration support vessel left port under the control of a pilot; the Master and OOW were also on the bridge. About five minutes after having left the berth, and while proceeding at about 3.5 knots, a loud noise was heard and a slight shudder was felt throughout the ship. At the time it was thought that the noise and shudder were caused by the anchor being secured in the anchor pocket. A few minutes later the pilot disembarked and the vessel continued on its voyage.
Over the next few hours it was discovered that the number 4 port ballast tank was taking water at a rate of about 8m3/hr. Even though the vessel’s ballast pumps could discharge at 100m3/hr, the Master turned the vessel around and they returned to berth for further inspections.
Once at berth, divers confirmed a fracture on the bottom plate of number 4 port ballast tank. New depth surveys of the area of presumed bottom contact were conducted by the National Hydrographic Service. Several previously uncharted shallow areas and rocks were discovered and a new chart was subsequently published.
- Some isolated ports still rely on charts that are based on relatively old surveys. In this case, the chart used had been issued by the National Hydrographic Service and was based on a 1935 survey.
- Unexpected noises and a shudder were an indicator that something out of the ordinary had happened. Because the ballast tanks were equipped with tank level gauges the crew quickly noticed that one of the ballast tanks was taking water. If you experience unexpected noises, always assume bottom contact and sound all tanks.