Commercial Vessel Compliance

4/13/2018: Marine Safety Information Bulletin 03-18, Oily bilge water management

The Office of Commercial Vessel Compliance released Marine Safety Information Bulletin 03-18, Oily Mixtures (“Oily Bilge Water”) Management for Oceangoing Vessels of less than 400 Gross Tons, to provide guidance to the industry, mariners, and the general public, on compliance options for oily bilge water management for oceangoing vessels less than 400 gross tons.


This bulletin summarizes key legal requirements in 33 CFR Part 151, Subpart A and 33 CFR Part 155, Subparts A and B for the proper management and disposal of oily mixtures by oceangoing vessels under 400 gross tons. An “oceangoing ship [or vessel]” – as defined in 33 CFR 151.05 – means any vessel that operates on international voyages, is certified for coastwise service beyond three miles, or operates beyond three nautical miles at any time. Oceangoing vessels falling into this category include – but are not limited to – tugs, ferries, shuttle vessels, commercial fishing vessels, and tour boats.

Oceangoing vessels of less than 400 gross tons must be able to retain all oily mixtures until it can be discharged to a reception facility per 33 CFR 155.350. Alternatively, vessels may carry approved oily-water separator (OWS) equipment to separate oil from the water and discharge the water overboard, provided the effluent contains less than 15 parts per million (ppm) oil and meets other criteria provided in 33 CFR 151.10. The Coast Guard encourages owners, operators, and crews to take responsible measures to manage oily waste such as reducing the generation of oily mixtures and engaging in voyage planning to account for safe retention and lawful disposal.


The regulations discussed in this document have been in effect since 1983. 33 CFR 155.350 requires oceangoing vessels of less than 400 gross tons to either 1) have the capacity to retain all oily mixtures onboard and be equipped to discharge said mixtures to a reception facility or 2) have approved OWS equipment for processing oily mixtures from bilges or fuel oil tank ballast and discharges into the sea according to 33 CFR 151.10.

33 CFR 151.10 regulates the discharge of oily mixtures by all oceangoing vessels. Discharges of oil or oily mixtures are prohibited unless the oil content of the effluent is less than 15 ppm, the vessel has in operation OWS equipment, and the vessel meets various other requirements depending on its location. Note that discharges may be permissible in emergencies to secure the safety of a vessel or save life at sea per 33 CFR 151.11. Such discharges must be reported to the nearest Captain of the Port or the National Response Center per 33 CFR 151.15.

Both 33 CFR 155.350 and 33 CFR 151.10 apply to U.S. vessels (registered under federal law or documented under state law) wherever located and to foreign flagged vessels within twelve miles of the U.S. shoreline.

The terms “oily” and “oily mixtures” have a broad meaning under 33 CFR 151.05. The term includes “oily bilge water” which is “water which may be contaminated by oil” resulting from leaks or maintenance. Further, “any liquid entering the bilge system” is automatically considered “oily bilge water” per 33 CFR 151.05.

Please note the discharge of oily mixtures from oceangoing vessels overboard via “decanting” is prohibited. “Decanting” or “skimming” are common terms related to pumping bilge water from below any perceived oily film or sheen on the bilge water’s surface. This practice is a violation of 33 CFR 151.10 and 33 CFR 155.350 regardless if the discharge creates a sheen on the outside water. However, if the discharge from any vessel creates a sheen or violates applicable state water quality standards, the discharge may separately constitute a violation of the Clean Water Act. 33 U.S.C. §§ 1319(c), 1321(b)(6); 40 CFR 110.3.

General depiction of unlawful "decanting" or “skimming” where vessel is

Operation of a vessel without pollution prevention equipment required by 33 CFR 155.350 or other regulations may result in civil penalties, judicial civil action, and/or Captain of the Port orders directing remedial action. Also, unlawful discharges of oily mixtures may result in the previous listed actions as well as criminal proceedings pursuant to the Act to Prevent Pollution from Ships and the Clean Water Act.

Therefore, the Coast Guard recommends that vessel owners, operators, and crew take reasonable measures to appropriately manage and dispose of all oily mixtures. Examples of such measures may include:

• Identifying and reducing sources of liquid entering machinery space bilges;
• Ensuring material conditions do not result in water entering machinery spaces from non-machinery spaces (e.g., fish holds) resulting from leaks or free communication; and
• Voyage planning for the safe and lawful maintenance and disposal of oily mixtures.


The Coast Guard remains committed to preventing pollution and enforcing our nation’s environmental laws to maintain a level-playing field where violators do not gain an unfair advantage through pollution violations. Readers are encouraged to review the cited regulations and other applicable regulations free of charge via the U.S. Government Publishing Office at

A pdf of the bulletin is available in the MSIB library. Please submit any questions specific to this bulletin to HQS-PF-FLDR-CG-CVC@USCG.MIL.

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