Oil Discharge Rules at Sea

1. The ship is proceeding en route.

2. The ship has equipment of a design approved by the Administration that ensures the oil content of the effluent, without dilution, does not exceed 15 ppm.

3. The oily mixture does not originate from cargo pump-room bilges on oil tankers.

4. For oil tankers, the oily mixture is not mixed with oil cargo residues.

Important Note: The discharge requirements under MARPOL Annex I, Regulation 15 (Control of Discharge of Oil from Machinery Spaces), are subject to the prohibition of oil discharge in the Antarctic area, the applicable restrictions under the Polar Code, and the exceptions specified in Regulation 4.

Under Regulation 4 (Exception), the discharge of oil or oily mixtures may be exempted from the applicable discharge prohibitions when:

1. The discharge is necessary to secure the safety of the ship or save life at sea.
2. The discharge results from damage to a ship or its equipment.
3. The discharge resulting from combating specific pollution incidents to minimize pollution damage.

MARPOL Annex I – Regulation 34: Control of Discharge of Oil (oil tanker cargo area)

A.     Discharge outside Special Area (Regulation 34.1)

Not apply to the discharge of clean or segregated ballast

The discharge into the sea of oil or oily mixtures from the cargo area of an oil tanker shall be prohibited except when ALL the following conditions are satisfied:

1.      The tanker is proceeding en route, is not within a special area and is more than 50 nautical miles from the nearest land.

2.      The instantaneous rate of discharge of oil content does not exceed 30 litres per nautical mile.

3.      The total quantity of oil discharged into the sea does not exceed: 1/15000 of the total quantity of the particular cargo, for tankers delivered on or before 31 December 1979. And 1/30,000 of the total quantity of the particular cargo for tankers delivered after 31 December 1979.

4.      The tanker has in operation an oil discharge monitoring and control system (Regulation 31) and a slop tank arrangement (Regulations 29).

B. Discharge in Special Areas (Regulation 34.3)

Any discharge into the sea of oil or oily mixtures from the cargo area of an oil tanker is prohibited while in a special area.

Unlike Regulation 15, Regulation 34 does not permit cargo-area discharges within special areas based on a 15ppm limit (parts of oil per million parts of water by volume).

C. Requirements for oil tankers of less the 150 gross tonnage (Regulation 34.6)

The requirements of regulation 29 (slop tank), regulation 31 (oil discharge monitoring and control system), and regulation 32 (oil/water interface detector) of annex 1 of MARPOL shall not apply to oil tankers of less than 150 gross tonnage, for which the control of discharge of oil under this regulation shall be affected by the retention of oil on board with subsequent discharge of all contaminated washings to reception facilities.

References

1. International Maritime Organization (IMO). (2022). MARPOL Consolidated Edition 2022, as amended. Annex I – Regulations for the Prevention of Pollution by Oil. IMO Publishing, London. ISBN: 978-92-801-1743-1.
2. MARPOL Annex I – Regulation 4: Exceptions to the discharge prohibitions.
3. MARPOL Annex I – Regulation 14: Oil Filtering Equipment.
4. MARPOL Annex I – Regulation 15: Control of Discharge of Oil – Machinery Spaces.
5. MARPOL Annex I – Regulations 29, 31 and 32: Slop Tanks, Oil Discharge Monitoring and Control Systems, and Oil/Water Interface Detectors.
6. MARPOL Annex I – Regulation 34: Control of Discharge of Oil – Cargo Areas of Oil Tankers.
7. MARPOL Annex I – Regulation 38: Reception Facilities.
8. International Maritime Organization (IMO). International Code for Ships Operating in Polar Waters (Polar Code), Part II-A, Chapter 1 – Prevention of Pollution by Oil.
9. International Maritime Organization (IMO). MARPOL Consolidated Edition 2022 – Official Supplements and Amendments.