As per MARPOL 73/78, regulation 9
Discharge shall be prohibited when:
- The tanker is within a special area
- The tanker is less than 50 NM from the nearest land.
- The tanker is not proceeding en route.
- The instantaneous rate of discharge exceeds 30 liters per nautical mile.
- The total quantity discharged exceeds 1/15,000 of the total cargo the ship is carrying.
- The tanker does not have in operation an oil discharge monitoring and control system and a slop tank arrangement.
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Methods of prevention of pollution in Special Areas
The Special Areas are as follows:
- The Mediterranean Sea and its gulfs and seas within
- The Baltic Sea in Finland
- The Black Sea
- The Red Sea Area
- The Gulf of Aden
- The Antarctic
- Any discharge of any sort is prohibited by ships of more than 400 gross tons while in these areas.
- Bilge water may be discharged provided:
- It does not originate from the cargo pump-room bilges
- It is not mixed with oil residues
- The ship is proceeding en route
- The oil content does not exceed 15 ppm
- The ship has filtering equipment in operation
- The ship has an automatic stopping device to stop discharging is the bilge content exceeds 15 ppm.
- The oil residues which cannot be discharged shall be retained on board or discharged to reception facilities.
- The Governments of Parties to the Convention shall be obliged to investigate should visible traces of oil be observed in the immediate vicinity of a ship.
- For the Antarctic area, the Governments of Parties to the Convention should ensure that ships flying their flag should be fitted with sufficient facilities to hold all its sludge, dirty ballast, oil and oily mixtures while operating in the area.