Annex I of MARPOL 73/78 guideline for preventing pollution by ships




The Convention of 1973 for preventing sea pollution by tankers and the 1978 Protocol, MARPOL 73/78 contains 6 annexes: Regulations for preventing pollution of the sea by hydrocarbons,

by toxic liquid substances transported in bulk,

by toxic substances transported by sea in containers,

by waste water from ships,

waste from ships and

air pollution

Below number of annexes and their date of effect :
Annex I :Hydrocarbons ,2 October 1983
Annex II :Toxic liquid substances transported in bulk, 6 April 1987
Annex III :Toxic substances transported by sea in containers, 1 July 1992
Annex VI :Waste water from ships, 27 September 2003
Annex V :Waste from ships ,31 December 1988
Annex VI :Air pollution 19 May 2005


Annexe I
Regulations for preventing pollution of the sea by hydrocarbons Compliance with the terms of this first annexe, along with the second, is compulsory and if a government approves or signs the Convention, it cannot reject the terms set forth in these two annexes. On the contrary, as stipulated in the Convention, Annexes III, IV, V and, in future, the new annexe VI are all optional, i.e., the governments of adhering states may or may not adopt them, depending on their interests.



It could be said that oil tankers are the cornerstone of MARPOL; however, given the evolution of vessels as regards their shapes and types, oil tanker is not a vessel that carries only oil, but the convention enlarges this definition. The definition of oil tanker given by MARPOL not only includes the image of an oil tanker that carries crude oil or its by-products, but it also includes OBO (Ore Bulk Oil) tankers or tankers carrying combined loads and vessels carrying chemicals and gases.

According to Regulation 1, all vessels to which the Convention applies can be divided up into two main groups: new vessels or previously-existing vessels. New vessels are considered to be the following (Regulation 1, section 6):

    Vessels whose construction contract was formalised after 31-12-1975, or
    whose keels were either installed or being installed after 30- 6-1976, or
    vessels delivered after 31-12-1979, or
    vessels that have undergone any kind of important transformation

Consequently, all vessels not complying with the above stipulations are considered to be previously-existing vessels (Regulation 1, section. 7). However, the main difference of MARPOL with respect to previous agreements was the installation of separate ballast tanks in vessels, unlike non-MARPOL vessels, whose ballast tanks were also used as cargo tanks. Given that although, with the entry into effect of MARPOL, there are still vessels without these separate ballast tanks, those vessels are authorised to sail, provided the amount of clean ballast is not harmful to the sea.

Therefore, clean ballast is considered to be seawater coming from a tank carrying a cargo of hydrocarbons, that, when unloaded, produces no visible traces on the water surface when the water is calm and clean. States that lack sufficient resources have stations that control and watch over these unloading operations, and simultaneously obtain samples of the liquid content that remains in the ballast tank, as even if that unloading operation done out at sea could cause visible traces of hydrocarbons on the surface, the ballast is considered clean if the quantity of hydrocarbons does not exceed 15 parts per million.

All new oil tankers with deadweight tonnages equal to or more than 20000 dwt used for transporting crude oil or those with deadweight tonnages of over 30000 dwt used for carrying oil-based products, and existing oil tankers that are used to carry crude oil whose deadweight tonnages are equal to or more than 40000 dwt must be fitted with separate ballast tanks.

In no case must the cargo tanks be used as ballast tanks. This is what is set forth in the general legislation. However, the case may arise that in bad weather conditions that could jeopardise the safety of the vessel while sailing, the only way to guarantee the vessel is to use the cargo tanks as ballast tanks. In the case of these vessels, the size of the ballast tanks must be sufficient for the ship to maintain more favourable conditions for ensuring safety while sailing without having to use the cargo tanks for ballast purposes, in which case we are not referring to separate ballast tanks.

Consequently, having separate ballast tanks is a great step forward in preventing pollution. Although these tanks usually contain only seawater, they may be used as cargo tanks, provided the cargo is not a hydrocarbon or a toxic substance.

At all events, as stipulated in MARPOL, Annexe 1, Regulation 9, Control over unloading hydrocarbons, section 1), it is absolutely forbidden for vessels to unload hydrocarbons or oily mixtures into the sea. However, there is a series of exceptions to this, since the convention foresees only two types of vessels: oil tankers and vessels other than oil tankers. Below is a chart showing those exceptions, in which case it is permitted to carry out unloading operations in the following cases:

Oil Tankers Vessels other than Oil Tankers Gross Tonnage = 400 T
Vessels other than Oil Tankers Gross Tonnage < 400 T
They must be outside a special zone
They must be outside a special zone
They must be outside a special zone, and the government is responsible for ensuring that those vessels are fitted with installations for retaining hydrocarbon waste
  • They must be more than 50 nautical miles from the nearest coastline


  • They must be on course


  • They must be on course


  • The limit of 15 parts per million must not be exceeded


  • Hydrocarbon unloading regime = 30 litres per sea mile


  • The vessel must have a vigilance and control system for unloading operations and hydrocarbon-filtering equipment


  • The total quantity of hydrocarbons unloaded into the sea MUST NOT exceed:
    1/15000 of the total load for existing oil tankers and 1/30000 for new oil tankers


  • The oil tanker must have a vigilance an control system for unloading hydrocarbons
A check can be performed that the unloading is permitted if the ship is sailing outside a special zone, unless it is sailing in a special zone in the Antarctic, in which case it is forbidden for any type of vessels to perform unloading operations.

Nevertheless, the possibility exists, even in the case of unloading with negative consequences for the marine environment, that this is not considered to be an infringement of the Convention19. Such cases are those in which the lives of people might have been endangered if that unloading operation had not been carried out, which is referred to by the (state of need) juridical concept, in which preference is give to the juridical good protected (human life) than to the natural environment.

To prevent unloading of hydrocarbons in the case of running aground or boarding, one of the measures adopted in Annexe I was the installation of ballast tanks or spaces not used for loading or for diesel near the cargo tanks.

Those tanks may be lateral tanks laid out along the length of the ship’s side or laid out at the bottom of it, known as double-bottomed tanks. These lay-outs are applicable to oil tankers with deadweight tonnages equal to or more than 5000 tonnes, with building contracts awarded as from 6 July, 1993. This regulation is of vital importance since it obliges oil tankers built after July 1993 to have double hulls, thereby leading to a substantial reduction in the international fleet of single-hull ships in the future.

Certificates, Recognition and Inspections

MARPOL states that shipping companies must be in possession of an International Oil Pollution Prevention Certificate, also known by its initials in English, (IOPP). That certificate must be renewed at least every five years.

To ensure a correct verification, vessels are submitted to a series of inspections and examinations in the case of oil tankers whose gross tonnage is equal too r more than 150 T or in the case of all other vessels whose gross tonnage is equal to or more than 400 T. The first of these inspections must be made before the vessel is put into operation or before the issuance of the (IOPP) certificate.

The administration makes regular checks at intervals not exceeding five years, which makes it possible for it to make a check every year or every six months on the vessel, on issues related to preventing pollution. Such inspections, which were, until now, probably not made in an efficient manner, have now been stepped up following the measures adopted in the Erika I legislative package. For that purpose, these inspections have been carried out by inspectors appointed by the administration. This is contemplated in European Parliament and Council Directive 2001/106/EC of 19 December, 2001 on compliance with the international maritime safety laws and pollution prevention.

In relation with what has been said up to now, this directive aims to substantially increase inspections on vessels, particularly with respect to one of the ballast tanks. Depending on the age of the vessels, those inspections are to be performed at shorter intervals than for relatively new vessels.

Furthermore, that European directive sets forth that the vessels must send a series of documents to the authorities responsible for vessel that are mooring with information about the vessel and its pollution prevention systems, in order to facilitate such inspections. However, this still does not remove sub-standard vessels from the seas since the easiest option for such vessels is to go to states in which this and other equally restrictive directives are not applicable, although it seriously impairs their range of operations in maritime trade.

Reception Facilities and Services

The adoption of this Convention entails, among other things, that the ports of the states signing it must have stations for unloading hydrocarbons and oily mixtures, even though they do not originate from cargo tanks. Therefore, as a general rule, all ports in which unloading of crude is carried out must have those facilities.

However, this regulation not only affects ports used to unload crude oil, but also applies to shipyards. This is due to the fact that repairs of cargo tanks or cargo space is performed in those facilities, or in facilities in which those tanks are cleaned.

Retaining of hydrocarbons on board

In this section, reference has been made to vessels with systems for retaining hydrocarbons on board, particularly in oil tankers with gross tonnages that are equal to or more than 150 T.

Reference is made to having a washing system for cargo tanks, provided that system is approved by the government of the country where the tanker is registered. In addition, this requires the existence of a decantation tank to which the water used to clean the cargo tanks is piped. This tank is emptied in the event that it is possible to connect a line to land or to a vessel provided for that purpose.

For vessels visiting Spanish ports, there is a discount of 2% off the port rates for vessels presenting an invoice proving they have used a MARPOL waste-collection system. Lastly, there is a vigilance and control device for operations involving the unloading of hydrocarbons. The decantation tanks must have a capacity greater than 3% of the hydrocarbon transportation capacity, and in exceptional cases, this percentage is reduced to 1%23.

However, it is of vital importance to say that the tankers must have a device that is efficient at all times for controlling the unloading of hydrocarbons from the vessel itself. For this purpose there must be a meter that constantly shows the total number of litres unloaded per nautical mile.

In addition, that system must be approved by the administration and also record the litres per mile, date and time when the unloading operation is performed, which must be kept for at least 3 years. This constitutes an extremely effective control of unloading operations performed on board the tankers. Since it is an automatic device, it reduces the possibility of the unloading operation being inaccurately recorded, in addition to being set into operation as soon as an unloading operation is detected.

To prevent the system from being unable to control the unloading operations due to a failure, the administration obliges the vessel to have another manual device. According to the regulation itself, the vessel can be immobilised by the port authorities in the case of that automatic unloading control system functioning. At most, it can allow the tanker to sail if the destination is simply a shipyard in order to undergo repairs. Therefore yet again, it is obvious that non-adapted vessels will have problems in docking in certain ports, but there is a series of exceptions to this, and the administration may authorise the vessel to continue its journey. Those exceptions are described in Annexe I, Chapter II, Regulation 15, section 3.

Hydrocarbons Register

This is a very simple element, consisting of a document in the form of a register in which all unloading operations made from the vessel must be recorded. Therefore, it includes both operations involving the ballasting of cargo tanks, unloading the ballast if there are no separate ballast tanks, and the loading or unloading hydrocarbon waste, including a record of the closing of the valves after those unloading operations.

It must be kept in an adequate place to allow it to be inspected at any reasonable time and must always remain on board. It should be kept for three years after recording the last entry. All copies certified by the ships captain as a true copy of an entry made in the Hydrocarbons Register is admitted in any court proceedings as proof of the facts declared therein.

That register has two parts: Operations in machine areas and Loading and ballasting operations, for oil tankers (with the meaning given to the term oil tanker in the Convention) with gross tonnages of over 150 T.


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