{"data":{"id":"us/33-cfr-157.03","jurisdiction":"us","citation":"33 CFR 157.03","heading":"Definitions.","body":"Except as otherwise stated in a subpart:\nAmidships means the middle of the length.\nAnimal fat means a non-petroleum oil, fat, or grease derived from animals and not specifically identified elsewhere in this part.\nBallast voyage means the voyage that a tank vessel engages in after it leaves the port of final cargo discharge.\nBreadth or B means the maximum molded breadth of a vessel in meters.\nCargo tank length means the length from the forward bulkhead of the forwardmost cargo tanks, to the after bulkhead of the aftermost cargo tanks.\nCenter tank means any tank inboard of a longitudinal bulkhead.\nClean ballast means ballast which:\n(1) If discharged from a vessel that is stationary into clean, calm water on a clear day, would not—\n(i) Produce visible traces of oil on the surface of the water or on adjoining shore lines; or\n(ii) Cause a sludge or emulsion to be deposited beneath the surface of the water or upon adjoining shore lines; or\n(2) If verified by an approved oil discharge monitoring and control system, has an oil content that does not exceed 15 p.m.\nCombination carrier means a vessel designed to carry oil or solid cargoes in bulk.\nCrude oil means any liquid hydrocarbon mixture occurring naturally in the earth, whether or not treated to render it suitable for transportation, and includes crude oil from which certain distillate fractions may have been removed, and crude oil to which certain distillate fractions may have been added.\nDeadweight or DWT means the difference in metric tons between the lightweight displacement and the total displacement of a vessel measured in water of specific gravity 1.025 at the load waterline corresponding to the assigned summer freeboard.\nDedicated clean ballast tank means a cargo tank that is allocated solely for the carriage of clean ballast.\nDomestic trade means trade between ports or places within the United States, its territories and possessions, either directly or via a foreign port including trade on the navigable rivers, lakes, and inland waters.\nDouble bottom means watertight protective spaces that do not carry any oil and which separate the bottom of tanks that hold any oil within the cargo tank length from the outer skin of the vessel.\nDouble hull means watertight protective spaces that do not carry any oil and which separate the sides, bottom, forward end, and aft end of tanks that hold any oil within the cargo tank length from the outer skin of the vessel as prescribed in § 157.10d.\nDoubles sides means watertight protective spaces that do not carry any oil and which separate the sides of tanks that hold any oil within the cargo tank length from the outer skin of the vessel.\nExisting vessel means any vessel that is not a new vessel.\nFleeting or assist towing vessel means any commercial vessel engaged in towing astern, alongside, or pushing ahead, used solely within a limited geographic area, such as a particular barge fleeting area or commercial facility, and used solely for restricted service, such as making up or breaking up larger tows.\nForeign trade means any trade that is not domestic trade.\nFrom the nearest land means from the baseline from which the territorial sea of the United States is established in accordance with international law.\nFuel oil means any oil used as fuel for machinery in the vessel in which it is carried.\nInland vessel means a vessel that is not oceangoing and that does not operate on the Great Lakes.\nInstantaneous rate of discharge of oil content means the rate of discharge of oil in liters per hour at any instant, divided by the speed of the vessel in knots at the same instant.\nIntegrated tug barge means a tug and a tank barge with a mechanical system that allows the connection of the propulsion unit (the tug) to the stern of the cargo carrying unit (the tank barge) so that the two vessels function as a single self-propelled vessel.\nLarge primary structural member includes any of the following:\n(1) Web frames.\n(2) Girders.\n(3) Webs.\n(4) Main brackets.\n(5) Transverses.\n(6) Stringers.\n(7) Struts in transverse web frames when there are 3 or more struts and the depth of each is more than 1/15 of the total depth of the tank.\nLength or L means the distance in meters from the fore side of the stem to the axis of the rudder stock on a waterline at 85 percent of the least molded depth measured from the molded baseline, or 96 percent of the total length on that waterline, whichever is greater. In vessels designed with drag, the waterline is measured parallel to the designed waterline.\nLightweight means the displacement of a vessel in metric tons without cargo, fuel oil, lubricating oil, ballast water, fresh water, and feedwater in tanks, consumable stores, and any persons and their effects.\nMajor conversion means a conversion of an existing vessel that:\n(1) Substantially alters the dimensions or carrying capacity of the vessel, except a conversion that includes only the installation of segregated ballast tanks, dedicated clean ballast tanks, a crude oil washing system, double sides, a double bottom, or a double hull;\n(2) Changes the type of vessel;\n(3) Substantially prolongs the vessel's service life; or\n(4) Otherwise so changes the vessel that it is essentially a new vessel, as determined by the Commandant (CG-CVC).\nMARPOL 73/78 means the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating to that Convention. A copy of MARPOL 73/78 is available from the International Maritime Organization, 4 Albert Embankment, London, SE1\nNew vessel means:\n(1) A U.S. vessel in domestic trade that:\n(i) Is constructed under a contract awarded after December 31, 1974;\n(ii) In the absence of a building contract, has the keel laid or is at a similar stage of construction after June 30, 1975;\n(iii) Is delivered after December 31, 1977; or\n(iv) Has undergone a major conversion for which:\n(A) The contract is awarded after December 31, 1974;\n(B) In the absence of a contract, conversion is begun after June 30, 1975; or\n(C) Conversion is completed after December 31, 1977; and\n(2) A foreign vessel or a U.S. vessel in foreign trade that:\n(i) Is constructed under a contract awarded after December 31, 1975;\n(ii) In the absence of a building contract, has the keel laid or is at a similar stage of construction after June 30, 1976;\n(iii) Is delivered after December 31, 1979; or\n(iv) Has undergone a major conversion for which:\n(A) The contract is awarded after December 31, 1975;\n(B) In the absence of a contract, conversion is begun after June 30, 1976; or\n(C) Conversion is completed after December 31, 1979.\nNon-petroleum oil means oil of any kind that is not petroleum-based. It includes, but is not limited to, animal fat and vegetable oil.\nOceangoing has the same meaning as defined in § 151.05 of this chapter.\nOfficer in charge of a navigational watch means any officer employed or engaged to be responsible for navigating or maneuvering the vessel and for maintaining a continuous vigilant watch during his or her periods of duty and following guidance set out by the master, international or national regulations, and company policies.\nOil means oil of any kind or in any form including, but not limited to, petroleum, fuel oil, sludge, oil refuse, and oil mixed with wastes other than dredged spoil. This includes liquid hydrocarbons as well as animal and vegetable oils.\nOil cargo residue means any residue of oil cargo whether in solid, semi-solid, emulsified, or liquid form from cargo tanks and cargo pump room bilges, including but not limited to, drainages, leakages, exhausted oil, muck, clingage, sludge, bottoms, paraffin (wax), and any constituent component of oil. The term “oil cargo residue” is also known as “cargo oil residue.”\nOil residue means—\n(1) Oil cargo residue; and\n(2) Other residue of oil whether in solid, semi-solid, emulsified, or liquid form, resulting from drainages, leakages, exhausted oil, and other similar occurrences from machinery spaces.\nOil spill response vessel means a vessel that is exclusively dedicated to operations to prevent or mitigate environmental damage due to an actual or impending accidental oil spill. This includes a vessel that performs routine service as an escort for a tank vessel, but excludes a vessel that engages in any other commercial activity, such as the carriage of any type of cargo.\nOil tanker means a vessel that is constructed or adapted primarily to carry crude oil or products in bulk as cargo. This includes a tank barge, a tankship, and a combination carrier, as well as a vessel that is constructed or adapted primarily to carry noxious liquid substances in bulk as cargo and which also carries crude oil or products in bulk as cargo.\nOily mixture means a mixture, in any form, with any oil content. “Oily mixture” includes, but is not limited to—\n(1) Slops from bilges;\n(2) Slops from oil cargoes (such as cargo tank washings, oily waste, and oily refuse);\n(3) Oil residue; and\n(4) Oily ballast water from cargo or fuel oil tanks, including any oil cargo residue.\nOily mixture means a mixture with any oil content.\nOther non-petroleum oil means an oil of any kind that is not petroleum oil, an animal fat, or a vegetable oil.\nPermeability of a space means the ratio of the volume within a space that is assumed to be occupied by water to the total volume of that space.\nPetroleum oil means petroleum in any form, including but not limited to, crude oil, fuel oil, sludge, oil residue, and refined products.\nPrimary towing vessel means any vessel engaged in towing astern, alongside, or pushing ahead and includes the tug in an integrated tug barge. It does not include fleeting or assist towing vessels.\nProduct means any liquid hydrocarbon mixture in any form, except crude oil, petrochemicals, and liquefied gases.\nSegregated ballast means the ballast water introduced into a tank that is completely separated from the cargo oil and fuel oil system and that is permanently allocated to the carriage of ballast.\nSlop tank means a tank specifically designated for the collection of cargo drainings, washings, and other oily mixtures.\nTank means an enclosed space that is formed by the permanent structure of a vessel, and designed for the carriage of liquid in bulk.\nTank barge means a tank vessel not equipped with a means of self-propulsion.\nTank vessel means a vessel that is constructed or adapted primarily to carry, or that carries, oil or hazardous material in bulk as cargo or cargo residue, and that—\n(1) Is a vessel of the United States;\n(2) Operates on the navigable waters of the United States; or\n(3) Transfers oil or hazardous material in a port or place subject to the jurisdiction of the United States. This does not include an offshore supply vessel, or a fishing vessel or fish tender vessel of not more than 750 gross tons when engaged only in the fishing industry.\nTankship means a tank vessel propelled by mechanical power or sail.\nVegetable oil means a non-petroleum oil or fat not specifically identified elsewhere in this part that is derived from plant seeds, nuts, kernels, or fruits.\nWing tank means a tank that is located adjacent to the side shell plating.","path":["Title 33—Navigation and Navigable Waters","CHAPTER I—COAST GUARD, DEPARTMENT OF HOMELAND SECURITY","SUBCHAPTER O—POLLUTION","PART 157—RULES FOR THE PROTECTION OF THE MARINE ENVIRONMENT RELATING TO TANK VESSELS CARRYING OIL IN BULK","Subpart A—General"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-33.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:25:35Z","sha256":"d3ed6f1a595f0eb36a6556692735153db87008d8bd0c82d6691015643f4188ec","source_id":"us-cfr","stale":true,"prev":"us/33-cfr-157.02","next":"us/33-cfr-157.04"},"notice":"GroundRules: Original legal text. Not legal advice."}