t was a 25 year old tanker which had drydocked in Greece. In drydock, the sewage was collected in a tank and was sent to shore collection tank once in a while when the barge or collecting tank was available. The high level alarm was not working and the level was also not monitored regularly. One day the tank got filled, and because of the pressure, the tank got cracked at the top and also at the side. Sewage started leaking into the store which was above the sewage tank. On the side DO bunker tank was situated.

The crack and the leakage onto the store could be realized, but this crack was not identified. The shore help was called and the sewage was transferred to the shore receptacle.At the end of drydocking, the ship could not go to the anchorage on its own power due to the starting air line problem. Hence tug assistance was called and the ship reached anchorage and the vessel was anchored safely. At the anchorage, DO bunkers were taken. At the anchorage, the sewage overboard valve was kept open. After a day, there was a sheen of oil observed around the ship.

Checks were carried out in ER and the cause for this oil leakage could not be located.The Greek coast guard came on board and asked for the oil samples. C/E instructed 2/E to give the DO sample from the service tank. This matched the oil sample they collected from the sea. The divers were employed and it was found that the DO was coming through the sewage plant overboard valve.

Sewage treatment plant was gas freed and on inspection found that the DO seeping through this plant from the bunker tank due to crack. DO was transferred to other tanks and the cracked plate was replaced with a new one.C/E and the Master were behind the bars for a week, and they were fined 20,000 US $ each.