An international conference held in London in October 1973 adopted a new International Convention for the Protection of Pollution from Ships to replace the 1954 Oil Pollution Convention. The "MARine POLlution Convention", MARPOL 73/78 for short, was signed in London on 2 November 1973. Its official name is: International Convention for the Prevention of Pollution of the Sea by Ships, 1973, as amended by the protocol of 1978. The Convention comprises 20 articles, two protocols and five technical annexes. There are also provisions governing the exchange of information between the Convention States, arbitration and amendments. In the two protocols certain articles are elaborated in more detail. Protocol I concerns the duty of notification incumbent on the captain of a ship in the event of an incident or risk of an incident causing pollution at sea.
Protocol II regulates the details of arbitration should a dispute arise between countries. In 5 annexes MARPOL 73/78 specifies prevention of pollution:
Annex I oil;
Annex II noxious liquid substances in bulk;
Annex III harmful substances in packaged forms;
Annex IV sewage from ships
Annex V garbage from ships
Annex VI emissions into the air
Annex I (oil), Annex II (noxious liquid substances in bulk) and Annex III (harmful substances in packaged forms) are relevant for this manual dealing with chemical spill response.
The main aim of the MARPOL 73/78 Convention is to combat the pollution of the sea by harmful substances to the extent that such pollution is the consequence of the conduct of operations on board ships (so called operational discharges). The activities covered here include the discharge into the sea of oil residues from the engine room and cargo tanks, of chemical residues, household waste and sanitary effluent.
In order to achieve a reduction in pollution, the following set of instruments is provided through MARPOL 73/78:
- Regulations on the construction and equipment of ships;
- Regulations on the conduct of operations on board and the keeping of records in a journal;
- Regulations on the conduct of surveys and inspections;
- The issue of certificates;
- Better facilities for surveillance.
The aspects accidental of spill prevention and response to be discussed in this section are:
- ship design operations on board
- traffic control
Requirements for ships may be divided into the following categories:
- Requirements to reduce the probability of an accidental spill;
- Requirements to limit the outflow in the event of an accidental spill.
A number of codes have been drawn up covering various aspects of the design and the standards of construction that should be adhered to for ships carrying dangerous substances.
Under the MARPOL 1973/78 there are several requirements having the objective to reduce the probability of an accident or to limit the outflow in the event of an accident.
MARPOL, Annex I contains the regulations for minimizing pollution from an oil tanker:
- The size of cargo tanks is limited to wing tanks up to 30,000 m3 and centre tanks up to 50,000 m3. As a result the amount of oil which can enter the sea following damage to a tank is limited;
- The segregated ballast tanks must be positioned in such a way as to give maximum protection to the cargo tanks in the event of a collision or grounding;
- Subdivision and stability requirements to ensure that tankers can survive damage to a degree, which is specified on the basis of the ship's length.
The technical annexes to the MARPOL 73/78 cover every day routines and operations on board ship. Each one is concerned with the prevention of a particular form of marine pollution, namely: oil (Annex I), liquid chemicals (Annex II), packaged chemicals (Annex III).
Annexes I and II are the so called mandatory Annexes: in other words a country which has adopted MARPOL 73/78 undertakes to enforce the provisions of these two Annexes, though not simultaneously. First comes Annex I (oil), followed at least three years later by Annex II (liquid chemicals).
The countries at their own discretion may adopt the other Annexes. Annex III to the MARPOL 1973/78 Convention contains general requirements relating to the prevention of pollution by harmful substances carried by sea in packaged form including those in freight containers, portable tanks, road and rail vehicles or ship borne barges.