What are the MARPOL Annex II cargo discharge criteria?
Short answer
| Condition | Requirement |
|---|---|
| Speed | en route, at least 7 knots (4 if not self-propelled) |
| Outlet | below the waterline, through the underwater outlet, within the designed rate |
| Distance | more than 12 nautical miles from the nearest land |
| Depth | not less than 25 metres |
| Procedure | the approved P&A Manual (regulation 14) |
| Category X | prewash to a reception facility down to 0.1% by weight; nothing to sea |
| Categories Y and Z | efficient stripping (regulation 12), then discharge under the conditions |
- Categories (regulation 6): X most harmful, Y, Z least, and other substances; the category sets the strictness.
- Regulation 13 conditions, all together: en route at least 7 knots (4 if not self-propelled); below the waterline through the underwater outlet within the designed rate; more than 12 nautical miles from land; depth not less than 25 metres; per the approved P&A Manual (regulation 14).
- Category X: mandatory prewash after unloading, residue and washings to a reception facility until at or below 0.1% by weight; nothing to sea.
- Y and Z: efficient stripping (regulation 12), then the remaining residue may go to sea under the conditions, Y more restricted than Z; no discharge in special areas such as the Antarctic.
- Support: regulation 12 stripping and underwater discharge arrangements, regulation 15 Cargo Record Book, regulation 16 survey and certification (Certificate of Fitness); India: MS Act 2025 s.147.
- As Chief Engineer: I support the stripping, prewash and underwater discharge so the ship stays within the criteria, all recorded.
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class I section of the Marine One forum, open to members enrolled for the MEO Class I exam.