What Is MARPOL?
MARPOL (International Convention for the Prevention of Pollution from Ships) is the primary international treaty governing vessel pollution. Adopted by the International Maritime Organization (IMO) in 1973 and amended by the 1978 Protocol, it is implemented in U.S. law by the Act to Prevent Pollution from Ships (APPS), which applies to U.S.-flag vessels worldwide and all foreign vessels in U.S. waters. MARPOL has six Annexes — each covering a different category of pollutant. Annexes I, IV, and V are the most tested on captain's license exams.
MARPOL Annexes — All Six at a Glance
| Annex | Subject | Applies To |
|---|---|---|
| I | Oil | All vessels (recreational ≥26 ft for placard) |
| II | Noxious Liquid Substances (NLS) | Tank ships carrying bulk chemicals |
| III | Harmful Substances in Packaged Form | Vessels carrying IMO-regulated packaged cargo |
| IV | Sewage | All vessels with installed toilets; USCG-inspected vessels |
| V | Garbage | All vessels (placard required ≥26 ft) |
| VI | Air Pollution | Vessels ≥400 GT; diesel engines ≥130 kW |
Annex I — Oil Pollution
Annex I covers oil pollution from ships — primarily bilge water, fuel spills, and cargo residues. The U.S. implementing law is APPS, supplemented by Clean Water Act Section 311. Key thresholds tested on the OUPV and Master exams:
No oil discharge of any kind within 3 nm of the U.S. baseline. Period. No exceptions.
Beyond 3 nm, bilge water discharge allowed only if oil content is below 15 parts per million through an approved oily water separator (OWS).
Any visible oil sheen on the water requires immediate notification to the NRC at 800-424-8802, regardless of quantity.
Annex I Required Equipment & Documents
- ▸Oil Record Book (ORB) — vessels ≥400 GT or certified ≥15 persons
- ▸Oily water separator (OWS) with 15 ppm monitor — vessels ≥400 GT
- ▸Oil discharge monitoring and control system — tankers ≥150 GT
- ▸Shipboard Oil Pollution Emergency Plan (SOPEP) — vessels ≥400 GT
- ▸MARPOL oil pollution placard (5×8 in) — vessels ≥26 ft
- ▸Placards must be posted in machinery space / bilge pump area
- ▸Bilge holding capacity or pump-out access — all commercial vessels
- ▸Oil spill response equipment — USCG-inspected vessels
Annex IV — Sewage
MARPOL Annex IV governs the discharge of sewage from ships. In the U.S., it is implemented by Clean Water Act Section 312 and 33 CFR Part 159. Every vessel with an installed toilet must have a USCG-approved Marine Sanitation Device (MSD). The three MSD types are the most exam-critical content in this section.
Marine Sanitation Device (MSD) Types
≤1,000 fecal coliform per 100 mL; no visible floating solids
Vessels 65 ft (19.8 m) and under in most navigable waters
NOT compliant — any discharge prohibited in NDZ
Know 'Type I = small vessels, flow-through, disinfected'
≤200 fecal coliform per 100 mL; ≤30 mg/L suspended solids
All vessels in all navigable waters (stricter than Type I)
NOT compliant — any discharge prohibited in NDZ
Type II = higher standard than Type I; approved for larger vessels
No treatment; zero discharge overboard; capacity depends on vessel
All vessels; the only option compliant with NDZ requirements
COMPLIANT — the only MSD type allowed in an NDZ
Type III = holding tank only; zero discharge; required in NDZs
Sewage Distance Rules
No discharge of any sewage, treated or untreated
Type I or II treated sewage may be discharged if vessel is underway
Untreated sewage may be discharged if vessel is underway at ≥4 knots
No-Discharge Zones (NDZs)
EPA-designated NDZs prohibit all overboard sewage discharge, regardless of treatment level or distance from shore.
- ▸Y-valve must be secured (locked, handle removed, or wire-sealed) in an NDZ
- ▸Major NDZs: Great Lakes, many state inland lakes, Puget Sound, Lake Tahoe
- ▸Only Type III holding tank is compliant in an NDZ
Annex V — Garbage
MARPOL Annex V prohibits the discharge of most garbage from vessels. The rules depend on the type of garbage and distance from shore. One rule has no exceptions: plastics can never be discharged overboard.
| Garbage Type | Prohibited Zone |
|---|---|
| Oil (machinery bilge water) | Within 3 nm of U.S. baseline |
| Sewage — untreated | Within 12 nm (and all NDZs) |
| Sewage — Type I/II treated | Within 3 nm and in all NDZs |
| Food waste — ground <25 mm | Within 3 nm |
| Food waste — not ground | Within 12 nm |
| Dunnage / packing materials | Within 25 nm |
| Plastics (any form) | EVERYWHERE — zero miles, no exceptions |
Garbage Management Plan
Required for vessels 12 meters (39 ft) or more in length.
- ▸Written procedures for collecting, storing, processing, and disposing of garbage
- ▸Person designated as responsible for implementing the plan
- ▸Must be kept aboard and available for USCG inspection
- ▸Must be in the working language of the crew
Garbage Record Book
Required for vessels 100 GT or more, or certified to carry 15 or more persons.
- ▸Must record every discharge operation or accidental loss
- ▸Date, time, position, category of garbage, and amount discharged
- ▸Signed by the officer in charge of the operation
- ▸Retained aboard for 2 years; available for USCG inspection
Discharge Limits — Master Distance Table
The exam loves specific distance numbers. Memorize this table. Every number has appeared on past OUCPV and Master exams.
Plastics
Oil / Ground food / Treated sewage
Untreated sewage / Unground food
Oil (≥400 GT machinery)
Dunnage / non-plastic packing
OWS oil content limit
Oil Spill & Pollution Reporting Requirements
Failure to report is a separate criminal offense from the spill itself. The National Response Center (NRC) operates 24 hours a day. When in doubt, call — unreported spills carry criminal exposure that reported spills do not.
National Response Center — 24/7
800-424-8802
Report any oil sheen, 400+ gallon spill, or hazardous substance release immediately
Any visible sheen, iridescence, or discoloration
National Response Center — 800-424-8802
Immediately upon discovery
Civil: up to $25,000/day; Criminal: up to $500,000 + 6 years
400 gallons or more of oil into navigable waters
National Response Center — 800-424-8802
Immediately — before cleanup if possible
Civil: up to $1,000 per barrel spilled
Equals or exceeds the 'Reportable Quantity' (RQ) in 40 CFR Part 302
National Response Center — 800-424-8802
Immediately upon knowledge of spill reaching navigable water
Civil and criminal; same range as oil spills
Any spill that 'may be harmful' — practical threshold: sheen
USCG Sector Commander + NRC
Immediately; written report may also be required within 14 days
License revocation possible in addition to fines
Hazardous Substances — Reportable Quantity (RQ)
For substances other than oil, the spill is reportable when the quantity reaching navigable water equals or exceeds the “reportable quantity” listed in 40 CFR Part 302, Table 302.4. RQs range from 1 pound (for acutely toxic substances) to 5,000 pounds for less hazardous materials. Common examples: gasoline (100 lbs RQ), diesel fuel (not separately listed — regulated as petroleum), sodium hydroxide (1,000 lbs RQ). If uncertain, call the NRC — they will determine reportability.
Required Placards
Placard requirements are strict-liability items on USCG inspections — the placard must be present, correct size, and posted in the correct location. Exam questions ask about all three elements: which vessels, what size, where posted.
All vessels 26 feet (8 m) or longer
Machinery space, bilge pump area, or where bilge pumping equipment is operated
"Discharge of Oil Prohibited" — must state penalties and prohibited zones
33 CFR Part 155
All vessels 26 feet (8 m) or longer
Galley, helm station, and outdoor deck areas
States that discharge of garbage in U.S. waters is prohibited; lists plastic prohibition
33 CFR Part 151, Subpart C
Vessels with installed toilets (heads) connected to an MSD
Each toilet compartment (head), near the Y-valve if installed
Instructions for proper MSD use; NDZ requirements; Y-valve position in NDZs
33 CFR Part 159
Penalties for Violations
Marine pollution violations carry some of the harshest penalties in maritime law. Captains are personally liable — the vessel owner's culpability does not eliminate the captain's own criminal exposure.
- •Up to $25,000 per day per violation
- •Up to $1,000 per barrel of oil spilled (CWA)
- •Assessed by USCG or EPA administratively
- •Does not require criminal prosecution
- •Fines up to $100,000 per violation
- •Imprisonment up to 1 year
- •Applies to negligent (unintentional) violations
- •USCG license revocation / suspension
- •Fines up to $500,000 per violation
- •Imprisonment up to 6 years
- •Includes falsifying Oil Record Book
- •Individual officers and crew can be prosecuted
Exam Strategy — Most-Tested Rules & Common Traps
Marine pollution questions appear in the Deck General & Safety section. Expect 4–8 questions on any OUPV or Master exam. These six points account for the majority of exam losses in this topic area.
The plastic prohibition has NO distance exception
The single most-missed garbage question: exam answers often include '25 nm from shore' as a trap for plastic discharge. Plastics are NEVER permitted overboard at any distance. The 25 nm rule applies to dunnage and non-plastic packing materials only.
3 nm vs 12 nm — know which rule applies to which substance
Oil: prohibited within 3 nm (with 15 ppm OWS limit beyond). Untreated sewage: prohibited within 12 nm. Unground food waste: prohibited within 12 nm. Ground food waste: prohibited within 3 nm. Dunnage: prohibited within 25 nm. Memorize: Oil=3, Sewage=12, Unground food=12, Ground food=3, Packing=25.
NDZ = Type III holding tank only
In a no-discharge zone, neither Type I nor Type II MSD allows discharge. Any overboard discharge is prohibited. The only compliant option is a Type III holding tank with all overboard valves secured. The exam may phrase this as 'which MSD is required in a no-discharge zone?' — answer: Type III.
Report to the NRC at 800-424-8802 — sheen triggers reporting
Any visible sheen requires immediate notification to the National Response Center. Candidates often think a small spill is below the reporting threshold. Under federal law, the threshold is not a volume — it is a sheen. If it sheens, report it.
The Oil Record Book is NOT required on recreational vessels under 400 GT
The ORB is required on vessels ≥400 GT or certified to carry ≥15 persons. The MARPOL placard IS required on all vessels ≥26 ft, including recreational. Exam trap: confusing the placard requirement with the ORB requirement.
Placard locations are tested directly
The oil pollution placard must be in the machinery space or bilge pump area. The garbage placard must be in the galley, at the helm, and on deck. The sewage placard must be in the head/toilet compartment. The exam asks 'where must the garbage placard be posted?' — all three locations (galley, helm, deck) are correct.
Frequently Asked Questions
What is the 15 ppm rule under MARPOL Annex I?
The 15 ppm rule limits the oil content of bilge water discharged overboard to no more than 15 parts per million. Beyond 3 nautical miles from the U.S. baseline, a vessel may discharge oily bilge water only if it passes through an approved oily water separator (OWS) that maintains output below 15 ppm, an oil content monitor with automatic shutoff is in use, the vessel is underway (not at anchor), and the discharge does not cause a visible sheen. Within 3 nm of the baseline, no discharge of any oily water is permitted regardless of oil content. The 15 ppm rule applies to the machinery space bilge water of all vessels subject to MARPOL Annex I.
What are the three types of marine sanitation devices (MSDs)?
USCG-approved MSDs come in three types: Type I is a flow-through treatment device that uses maceration and disinfection to reduce fecal coliform bacteria to no more than 1,000 per 100 mL and no visible floating solids — approved for vessels 65 ft and under in most waters. Type II provides advanced biological or chemical treatment resulting in no more than 200 fecal coliform per 100 mL and no more than 30 mg/L suspended solids — approved for all vessels. Type III is a holding tank that retains all sewage aboard for pump-out ashore — no treatment, no discharge. In state-designated no-discharge zones (NDZs), only a Type III (holding tank) satisfies the requirement because any overboard discharge is prohibited.
What garbage can never be thrown overboard, regardless of distance from shore?
Under MARPOL Annex V, plastics of any kind — including synthetic rope, fishing nets, plastic bags, and plastic packaging — are prohibited from discharge overboard anywhere in the ocean, at any distance from shore. There is no exception. Other materials have distance-based rules: food waste ground to less than 25 mm may be discharged 3+ nm offshore; unground food waste requires 12+ nm; dunnage, lining, and packing materials require 25+ nm. But the plastic prohibition is absolute — no distance makes it legal.
When must I report an oil spill to the National Response Center?
Under the Federal Water Pollution Control Act (Clean Water Act Section 311) and the Act to Prevent Pollution from Ships (APPS), you must immediately notify the National Response Center at 800-424-8802 whenever an oil discharge causes a visible sheen, discoloration, or slick on the water — even a small quantity. Additionally, any discharge of 400 gallons or more of oil is reportable regardless of whether a sheen is observed. For hazardous substances other than oil, reportability is triggered when the quantity equals or exceeds the 'reportable quantity' (RQ) listed in 40 CFR Part 302. Failure to report is a criminal offense under APPS, punishable by fines and imprisonment.
Is an oil record book required on recreational vessels?
The Oil Record Book (ORB) is required under MARPOL Annex I for vessels of 400 gross tons (GT) or more and all vessels certified to carry 15 or more persons in navigable waters of the U.S. Smaller uninspected recreational vessels are not required to maintain an ORB, but are still subject to the discharge prohibitions. The MARPOL 5×8-inch pollution placard ('Discharge of Oil Prohibited') is required on all vessels 26 feet and longer, including recreational vessels. The placard must be displayed in the machinery space or bilge pump area where it can be read by persons operating bilge pumping equipment.
What is a no-discharge zone (NDZ) for sewage?
A no-discharge zone (NDZ) is a body of water designated by the EPA where no vessel sewage may be discharged, regardless of treatment level. In an NDZ, even Type I or Type II treated effluent is prohibited. The only compliant option is a Type III holding tank that retains sewage for pump-out ashore. Vessels with overboard discharge valves (Y-valves) must have those valves secured in the closed position while in an NDZ — either by locking the handle, removing the handle, or using a non-releasable wire seal. Major NDZs include many lakes, state inland waters, and sections of the Great Lakes.
Where must the MARPOL garbage placard be posted?
MARPOL Annex V requires that a garbage placard be prominently posted in the galley, at the helm station, and at the vessel's outdoor deck areas on vessels 26 feet (8 meters) or longer. The placard must be at least 4×9 inches, written in the working language of the crew, and state that the discharge of garbage into waters of the U.S. or navigable waters is prohibited. The sewage placard (Annex IV) is also required on vessels with installed toilets and must be posted in each toilet compartment or near the head. Failure to display required placards is a strict-liability offense on USCG inspection.
What are the civil and criminal penalties for MARPOL violations?
Civil penalties under APPS (Act to Prevent Pollution from Ships) can reach $25,000 per day per violation. Criminal penalties for knowing violations can result in fines up to $500,000 per violation and imprisonment up to 6 years for individuals. Under the Clean Water Act Section 311, civil penalties for oil spills can reach $25,000 per day, or up to $1,000 per barrel spilled. Negligent violations carry fines up to $100,000 and imprisonment up to 1 year; knowing violations up to $500,000 and 6 years. Captains are personally liable and can face license revocation in addition to criminal prosecution. The USCG actively patrols for falsified oil record books, which are separately criminal acts.
Related Study Guides
Deck General & Safety
Full section overview: PFDs, EPIRBs, fire classes, stability, distress signals.
Marine Fire Fighting
Fire classes A–K, extinguisher types, USCG requirements by vessel length.
First Aid & CPR
Medical emergency response requirements for licensed captains.
VHF Radio Guide
MAYDAY protocol, channel assignments, DSC, and FCC licensing.
OUPV Exam Overview
Exam structure, section weights, passing scores, and registration.
Stability & Loading
GM, free surface effect, loading rules, and stability calculations.
Practice Marine Pollution Questions
Drill MARPOL distance rules, MSD types, reporting thresholds, and placard requirements with OUPV-style questions — instant feedback, full explanations. Find your gaps before exam day.
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