A complete exam-focused guide to MARPOL, OPA 90, spill reporting, garbage management, sewage treatment, ballast water, and every other pollution regulation the USCG captain's license exam tests.
The International Convention for the Prevention of Pollution from Ships — universally called MARPOL (from "Marine Pollution") — is the primary international treaty governing pollution from vessels. Originally adopted in 1973 and modified by a 1978 Protocol, it is commonly cited as MARPOL 73/78. The United States implements MARPOL through the Act to Prevent Pollution from Ships (APPS) and a body of USCG regulations found primarily in 33 CFR Parts 151–159.
MARPOL is divided into six Annexes, each targeting a different category of pollutant. Candidates for the USCG captain's license must understand the scope, key thresholds, record-keeping duties, and prohibited zones associated with each Annex.
| Annex | Pollutant Category | U.S. Implementing Reg |
|---|---|---|
| Annex I | Oil | 33 CFR Part 151, Subpart A |
| Annex II | Noxious Liquid Substances in Bulk | 33 CFR Part 151, Subpart B |
| Annex III | Harmful Substances in Packaged Form | 33 CFR Part 146 / 49 CFR |
| Annex IV | Sewage from Ships | 33 CFR Part 159 |
| Annex V | Garbage from Ships | 33 CFR Part 151, Subpart C |
| Annex VI | Air Pollution from Ships | 33 CFR Part 151, Subpart D / 40 CFR Part 1043 |
MARPOL designates certain sea areas as "Special Areas" where stricter discharge restrictions apply because of their particularly sensitive oceanographic and ecological conditions. Knowing which Annex applies to which Special Area is a frequent exam topic.
Annex I is the most tested MARPOL topic on the captain's license exam. It prohibits discharge of oil or oily mixtures unless specific conditions are met. For machinery space bilge water on vessels 400 GT or more operating outside special areas, discharge is permitted only when:
Exam Tip — The 15 ppm Rule
The 15 ppm threshold applies to the oil content of the overboard discharge, NOT the bilge water in the tank. In special areas (Baltic, Mediterranean, etc.), discharge of any oily water from the machinery space is prohibited regardless of oil content. Vessels must retain such waste on board and discharge it to a port reception facility.
Annex II covers chemical tankers carrying noxious liquid substances in bulk. Substances are categorized X, Y, and Z based on their hazard level. Category X substances (most hazardous) may not be discharged into the sea under any circumstances — they must be unloaded to a reception facility. Categories Y and Z have distance, depth, dilution, and speed requirements for any discharge.
Annex III addresses the transport of harmful substances in drums, containers, portable tanks, freight containers, and road and rail tank wagons. It establishes standards for packing, marking, labeling, documentation, stowage, quantity limitations, and exceptions. In the U.S., packaged hazardous materials are primarily regulated under 49 CFR (DOT) with USCG oversight for vessels.
Annex IV prohibits discharge of untreated sewage within 12 nautical miles of the nearest land. Comminuted and disinfected sewage may be discharged at a distance greater than 3 nm from the nearest land while the vessel is en route and making at least 4 knots. Sewage treated by an approved sewage treatment plant may be discharged at any distance, subject to flag and port state requirements.
Untreated sewage
No discharge within 12 nm
Comminuted & disinfected
Discharge allowed beyond 3 nm while en route at 4+ knots
Approved treatment plant
Discharge allowed at any distance
U.S. law (33 CFR Part 159) additionally regulates Marine Sanitation Devices (MSDs). All vessels with installed toilet facilities must have an operable MSD. Type I and Type II MSDs treat sewage to acceptable standards. Type III MSDs are holding tanks — no discharge at all. No-discharge zones (NDZs) established by states prohibit overboard discharge of treated sewage from any MSD within those waters.
MARPOL Annex V categorically prohibits the discharge of all plastics into the sea. "Plastics" includes synthetic ropes, fishing nets, plastic garbage bags, incinerator ash from plastic products, and any garbage that contains or is made of plastic. This prohibition is absolute — it applies everywhere, at all distances, at all times.
| Garbage Type | Outside Special Areas | Special Areas |
|---|---|---|
| All plastics | PROHIBITED everywhere | PROHIBITED everywhere |
| Food waste (comminuted/ground) | Greater than 3 nm from land | Greater than 12 nm (some areas prohibited) |
| Food waste (not processed) | Greater than 12 nm from land | PROHIBITED |
| Cargo residues (not HME) | Greater than 12 nm from land | PROHIBITED |
| Cleaning agents/additives in wash water | Any distance (if not harmful) | PROHIBITED |
| Operational waste | PROHIBITED (retain on board) | PROHIBITED |
| Cooking oil | Greater than 12 nm from land | PROHIBITED |
| Fishing gear (lost/discarded) | PROHIBITED | PROHIBITED |
All vessels of 100 GT or more, and vessels certified to carry 15 or more persons, must have a Garbage Management Plan and a Garbage Record Book. The plan must describe procedures for minimizing, collecting, storing, processing, and disposing of garbage. The record book must log all garbage disposal or incineration operations.
Annex VI establishes global limits on sulfur oxide (SOx) and nitrogen oxide (NOx) emissions from ships, and prohibits deliberate emissions of ozone-depleting substances. The global sulfur cap for fuel oil used on board ships is 0.50% m/m (mass by mass) since January 2020. Within Emission Control Areas (ECAs), the limit is 0.10% m/m.
The Oil Record Book is the primary compliance document for Annex I. MARPOL and 33 CFR 151.25 require its maintenance on all oil tankers of 150 GT or more, and all other ships of 400 GT or more. There are two parts:
Key ORB Requirements
The Oil Pollution Act of 1990 was enacted in response to the Exxon Valdez disaster. It fundamentally restructured U.S. law on oil spill prevention, response, and liability. Key provisions include:
Strict Liability
Responsible parties are liable for cleanup costs and damages without proof of negligence. Defenses are limited to acts of God, acts of war, and acts of a third party.
Liability Limits
Liability caps vary by vessel type and size. Limits are not available if the spill was caused by gross negligence, willful misconduct, or violation of federal safety regulations.
Financial Responsibility (COFR)
Vessels over 300 GT in U.S. waters and any vessel using a U.S. port must carry a Certificate of Financial Responsibility (COFR) demonstrating ability to pay for oil spill damages.
Vessel Response Plans (VRP)
Tank vessels and certain non-tank vessels must have USCG-approved Vessel Response Plans describing how the vessel will respond to a worst-case discharge.
Double-Hull Requirement
OPA 90 phased in mandatory double-hull construction for oil tankers operating in U.S. waters. Single-hull tankers were required to be phased out by 2015.
National Contingency Plan
OPA 90 strengthened the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), establishing the framework for federal response to oil spills.
Under OPA 90 and 33 CFR Part 155, tank vessels of 250 barrels (bbl) or more capacity operating in U.S. waters, and non-tank vessels of 400 GT or more, must have a USCG-approved VRP. The plan must identify:
33 CFR Part 153 implements the reporting and response framework for discharges of oil and hazardous substances into navigable U.S. waters, the contiguous zone (CZ), and the exclusive economic zone (EEZ). The person in charge (PIC) of a vessel must immediately report any discharge equal to or greater than the reportable quantity (RQ) to the National Response Center (NRC).
National Response Center (NRC)
1-800-424-8802
Available 24 hours a day, 7 days a week. The NRC is the single federal point of contact for reporting oil and chemical spills, radiological discharges, etiological (biological) releases, and MARPOL violations. Memorize this number — it appears regularly on the exam.
For oil, the reportable quantity is a discharge that causes a sheen on the water, a sludge or emulsion beneath the water surface, or a discoloration of the water. In practice, any visible discharge of oil requires reporting. For hazardous substances, RQs are specified in 40 CFR Part 302 Table 302.4.
Failure to report is a criminal offense. Under the Federal Water Pollution Control Act (Clean Water Act) and OPA 90, a person who fails to report a discharge may be fined up to $25,000 per day of violation and/or imprisoned for up to 5 years. Civil penalties under OPA 90 can reach $40,484 per day of violation (indexed for inflation). The responsible party also remains fully liable for all cleanup costs and natural resource damages.
Several categories of zones prohibit or restrict overboard discharge regardless of the type of waste:
MARPOL Special Areas
Designations under specific Annexes (I, II, V, VI) where stricter rules apply. Determined by the IMO based on oceanographic, ecological, and traffic conditions.
Particularly Sensitive Sea Areas (PSSAs)
IMO-designated areas (e.g., Florida Keys, Great Barrier Reef) that may have additional protective measures beyond standard MARPOL requirements.
No-Discharge Zones (NDZs)
Established by states under the Clean Water Act, Section 312. Prohibit discharge of treated sewage from MSDs within the zone. Common in environmentally sensitive lakes, bays, and coastal areas.
U.S. Inland Waters
The Clean Water Act broadly prohibits discharge of any pollutant from a vessel into waters of the United States without an NPDES permit or other authorization.
Antarctic Area
Under MARPOL Annexes I and V, the Antarctic is the most restrictive special area — virtually all overboard discharges of oil and garbage are prohibited.
Vessels carrying hazardous materials must comply with both MARPOL Annex III (for harmful substances in packaged form) and U.S. DOT/USCG regulations under 46 CFR and 49 CFR. Key obligations include:
The IMDG Code (International Maritime Dangerous Goods Code) is the international standard for the transport of dangerous goods by sea. It classifies hazardous materials into nine classes based on their primary hazard (explosives, gases, flammable liquids, flammable solids, oxidizers/organic peroxides, toxic/infectious substances, radioactive material, corrosives, and miscellaneous).
The International Convention on the Control of Harmful Anti-Fouling Systems on Ships (AFS Convention, 2001) prohibits the application or re-application of organotin (TBT) compounds as anti-fouling biocides. Vessels must have either:
Vessels of 400 GT or more engaged in international voyages must carry an International Anti-Fouling System Certificate and a Record of Anti-Fouling Systems. In U.S. waters, the Organotin Anti-Fouling Paint Control Act of 1988 further restricts TBT use on vessels less than 25 meters in length and prohibits it on aluminum vessels.
Ballast water is one of the most significant vectors for the introduction of invasive aquatic species worldwide. The International Ballast Water Management Convention (BWM Convention, 2004) entered into force in 2017 and established mandatory standards for all oceangoing vessels with ballast water tanks.
Standard D-1 — Ballast Water Exchange
An interim standard requiring ballast water exchange in the open ocean (at least 200 nm from the nearest land in water at least 200 meters deep). The vessel must achieve at least 95% volumetric exchange of ballast water. Exchange must occur before entering port waters. This standard was intended as a transitional measure.
Standard D-2 — Ballast Water Performance
The ultimate standard requiring installation of a type-approved Ballast Water Management System (BWMS) that treats ballast water to achieve specified discharge concentrations of living organisms. All vessels must comply by established implementation schedules tied to IOPP certificate renewal dates.
In U.S. waters, 33 CFR Part 151, Subpart D requires all vessels entering U.S. ports from outside the EEZ to conduct mid-ocean ballast water exchange or use an approved treatment system. The USCG enforces these requirements through inspections and review of the Ballast Water Reporting Form, which must be submitted to the USCG National Ballast Information Clearinghouse (NBIC) before arriving at a U.S. port.
The EPA also regulates ballast water under the Clean Water Act through the Vessel General Permit (VGP), which establishes numeric discharge limits for ballast water and requires Best Management Practices (BMPs) for vessels operating in U.S. waters. The Vessel Incidental Discharge Act (VIDA, 2018) directs the EPA, in consultation with the USCG, to develop a unified federal standard for vessel incidental discharges.
Federal environmental penalties for vessel pollution are severe and multi-layered. A single incident can trigger civil and criminal liability under several statutes simultaneously. Captains must understand that personal liability can follow crew members who order or cover up illegal discharges.
| Statute | Civil Penalty | Criminal Penalty |
|---|---|---|
| Clean Water Act (FWPCA) | Up to $25,000 per day | Up to $50,000/day and 3 years imprisonment (negligent); $100,000/day and 6 years (knowing) |
| OPA 90 | Up to $40,484 per day or per barrel discharged | N/A (civil statute; criminal liability under CWA) |
| Act to Prevent Pollution from Ships (APPS / MARPOL) | Up to $25,000 per day | Up to $500,000 fine and 6 years imprisonment per violation |
| Port and Waterways Safety Act | Up to $25,000 per violation | Criminal sanctions for knowing violations |
| Refuse Act (Rivers and Harbors Act) | N/A | Up to $2,500 fine and 1 year imprisonment |
The Act to Prevent Pollution from Ships (APPS) implements MARPOL in U.S. law. APPS criminal prosecutions have resulted in tens of millions of dollars in fines against shipping companies and individual imprisonment of crew members. The most common criminal charges involve:
Captain's Personal Liability
Under OPA 90 and APPS, individual officers — including the captain, chief engineer, and any crew member who orders, consents to, or participates in a violation — may be held personally criminally liable. The phrase "responsible corporate officer doctrine" (also called the Park Doctrine) allows prosecution of supervisory individuals who had authority to prevent violations, even if they did not personally order them. This is a powerful deterrent and means every licensed captain is on the hook for what happens on their vessel.
Independently of criminal or civil penalties, USCG may suspend or revoke a merchant mariner credential (MMC) upon conviction of a drug or alcohol offense, or upon a finding of misconduct, negligence, or incompetence. A pollution violation resulting in a criminal conviction will typically trigger a USCG suspension and revocation proceeding. Administrative law judges (ALJs) within the USCG adjudicate these proceedings, and decisions may be appealed to the Commandant.
There are six MARPOL Annexes. Annex I covers oil. Annex II covers noxious liquid substances in bulk. Annex III covers harmful substances in packaged form. Annex IV covers sewage. Annex V covers garbage. Annex VI covers air pollution, including SOx, NOx, ozone-depleting substances, and shipboard incineration.
Under MARPOL Annex I, machinery space bilge water may only be discharged overboard if the oil content of the effluent does not exceed 15 parts per million. The oily-water separator (OWS) must be operating, the vessel must be en route, and the discharge must be recorded in the Oil Record Book. In MARPOL special areas, ANY discharge from the machinery space is prohibited regardless of the ppm reading.
Part I of the ORB records all machinery space oily operations: ballasting and cleaning of fuel tanks, disposal of dirty ballast, sludge disposal, overboard discharge or disposal of bilge water, and accidental or exceptional discharges. Each entry must be signed by the responsible officer; each page must be countersigned by the master. The ORB is retained for 3 years after the last entry and is open to USCG inspection at any time in U.S. waters.
OPA 90 imposes strict liability for oil spill cleanup costs and damages, requires a Certificate of Financial Responsibility (COFR) for vessels over 300 GT, mandates USCG-approved Vessel Response Plans (VRPs) for tank vessels and certain non-tank vessels, and phased in double-hull requirements for oil tankers. Liability caps are lost if the spill was caused by gross negligence, willful misconduct, or violation of federal safety regulations.
The person in charge of a vessel must immediately report to the National Response Center at 1-800-424-8802 any discharge of oil that causes a visible sheen, sludge, or discoloration on or beneath the water surface, or any discharge of a hazardous substance equal to or exceeding its reportable quantity (RQ). Failure to report is a federal crime punishable by up to $25,000/day in fines and up to 5 years imprisonment.
ALL plastics are prohibited everywhere, always. Food waste that has been comminuted or ground may be discharged more than 3 nm from shore; unprocessed food waste may be discharged more than 12 nm from shore. Cargo residues that are not harmful to the marine environment may be discharged beyond 12 nm. In MARPOL special areas (Baltic, Mediterranean, etc.), virtually all garbage discharge except minimal cargo residues is prohibited. Garbage disposal must be recorded in the Garbage Record Book.
A Vessel Response Plan (VRP) is a USCG-approved document describing how a vessel will respond to a worst-case oil spill. Under OPA 90 and 33 CFR Part 155, VRPs are required for tank vessels of 250 bbl capacity or greater and non-tank vessels of 400 GT or more that use the waters of the United States. The VRP must identify a qualified individual (QI), an Oil Spill Response Organization (OSRO), notification procedures, and resources for responding to various spill scenarios.
Under the Act to Prevent Pollution from Ships (APPS), criminal penalties reach $500,000 per violation and 6 years imprisonment. Under the Clean Water Act, knowing discharges carry up to $100,000/day and 6 years imprisonment. Falsifying the Oil Record Book is itself a separate crime. Individual officers — including the captain — may be personally liable even if they did not personally direct the violation but had authority to prevent it. USCG may also suspend or revoke the mariner's credential.
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