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Case study
In June of 1990, the master of a 200,000 DWT VLCC was arrested by Piraeus port authorities and accused of having caused serious pollution of the sea by discharging oil residues. The spill was discovered on June 7th and reported at the time to be 10 miles in length, 23-30 meters in width and 10 centimetres in thickness. (This would be equivalent to a volume of oil of 50,000 cubic meters!) The pollution allegation was based on four vertical traces of oil residues on the vessel's port side when it arrived in Piraeus. State laboratory tests matched slop tank residues with samples of the spilled oil. The vessel's oil record book noted that the vessel pumped out ballast in the area at the time of its passage. Regrettably, the vessel's oil discharge monitor was not in operation at the time of de-ballasting. Four bank guarantees were lodged in order to avoid arrest of the vessel and for the release of the master on bail.

Case analysis
Without the ODM in operation and a properly annotated record of the CBT discharge, a tanker cannot defend itself against an accusation that it discharged oil to the sea at a particular time and place.

2.13.1 The oil discharge monitor
Regulation 15 of Chapter II of MARPOL 73/78 requires that tankers be fitted with an approved oil discharge monitoring and control system. The system may operate on one of a number of principles, but must be certified to meet the performance specifications adopted by the IMO, including a recording device indicating the oil content and rate of discharge.
ODM records must indicate the date and time of operation. Records must be maintained for inspection for three years. The ODM must be used when there is any discharge of effluent to the sea and must be arranged to automatically stop the discharge when the instantaneous rate of oil discharge is more than that permitted by regulation. Failure of the ODM shall also stop the discharge and shall be noted in the oil record book. Beginning on 4 April 1993, a tanker with a defective ODM may undertake only one ballast voyage (using manual alternatives of determining oil content of its effluent), before making repairs to the ODM.

Oil discharge monitor and control system.

A complete and detailed operations manual must be provided for routine ODM operations and for manual procedures to be used in the event of ODM malfunction. Each officer should become familiar with the principle and method of operation of the ODM on his ship, and understand the most common modes of failure of the equipment. Officers must also understand the principle and method of operation of the ship's oil/water interface detector.

ODME print-out from one hour after the start of slop tank decanting per oil record book entry.

Use of the ODM is required when discharging ballast from cargo or CBT tanks, slop tanks, or treated bilge water. Dirty ballast from cargo tanks, or SBT which is suspected to contain oil, must be discharged overboard above the ship's water line unless:

  • The surface of the ballast is examined and found free from oil immediately before discharge,

  • The tanks have settled for a sufficient time to permit suitable separation, the level of the oil/water interface has been determined using an approved interface detector and the discharge is by gravitation, or

  • The discharge line is fitted with a part-flow piping system which is under observation throughout the discharge.
  • 2.13.2 The oil record book
    Regulation 20 of Chapter II of MARPOL 73/78 requires every oil tanker (of 150 gross tons or more), to carry and maintain Parts I and II of the oil record book in the form specified by appendix III of the regulations. Part I is arranged to record machinery space operations. Part II is designed to record cargo or ballast operations on oil tankers. Each completed entry in the oil record book must be signed and dated by the officer or officers in charge. Each completed page must be signed by the master.
    The entries are arranged according to a letter and number code. Entries must be completed for each tank separately. Entries shall be made without delay. The entries shall be in the official language of the flag state. Vessels having an IOPP certificate must also make entries in English or French. The oil record book must be kept readily available for inspection at all times. The required oil record book entries are:
    a Loading of oil cargo.
    b Internal transfer of oil cargo during voyage.
    c Unloading of oil cargo.
    d Crude oil washing (COW tankers only).
    e Ballasting of cargo tanks.
    f Ballasting of dedicated clean ballast tanks (CBT tankers only).
    g Cleaning of cargo tanks.
    h Discharge of dirty ballast.
    i Discharge to water from slop tanks into the sea.
    j Disposal of residues and oily mixtures not otherwise dealt with.
    k Discharge of clean ballast contained in cargo tanks.
    l Discharge of ballast from dedicated clean ballast tanks (CBT tankers only).
    m Condition of oil discharge monitoring and control system.
    n Accidental or other exceptional discharges of oil.
    o Additional operational procedures and general remarks.

    Where an entry cannot be properly coded, it should be recorded in the national language of the officer and in English or French. National (port state) authorities may ask to inspect the oil record book at any time and have certified copies made on request.
    A review of some oil record books has shown examples of entries which, if carefully reviewed, incriminated the officer in charge for violation of the MARPOL regulations. These entries were then signed by the master! Great care must be taken to make the entries correctly, in a way which accurately reflects the care taken to avoid pollution.

    Owners/operators of tankers should provide detailed advice regarding oil record book entry procedures.

    An example of a simplified series of oil record book entries for a typical voyage by a SBT tanker follows:
    After decanting slops for 12 hours, the tanker began decanting the slop tank at 15.00 (Zulu). At 16.12 the pumping rate was reduced from 1000 H3/hr to 375 M3/hr (for an average rate of 750 M3/hr).

    2.13.3 Oil discharge limitations
    Regulation 9 of Chapter II of MARPOL 73/78 prohibits any discharge of oil or oily mixtures into the sea by tankers except when the following conditions are satisfied:

  • The tanker is not within a special area.

  • The tanker is more than 50 nautical miles from the nearest land.

  • The tanker is proceeding en route.

  • The instantaneous rate of discharge of oil content does not exceed 60 litres per nautical mile.
    The total quantity of oil discharged into the sea does not exceed:
    a For existing tankers 1/15,000 of the total quantity of the particular cargo of which the residue formed a part and
    b For new tankers 1/30,000 of the total quantity of the particular cargo of which the residue formed a part

  • The tanker has in operation and oil discharge monitoring and control system and a slop tank arrangement as required by Regulation 15.

  • Control of discharge of oil from cargo tank areas of oil tankers.
    *Special area requirements take effect in the Mediterranean Sea, Black Sea and Baltic Sea areas from the day of entry into force of MARPOL 73/78 and for the Red Sea and Gulf areas from the date established by IMO.
    **'Clean ballast' is the ballast in a tank which has been so cleaned that the effluent therefrom does not create a visible sheen or the oil content exceed 15 ppm (for the precise definition of 'clean ballast', see regulation 1(16) of MARPOL 73/78)

    2.13.4 Special areas and prohibited zones
    Regulation 10 of Chapter II of MARPOL 73/78 established the following special areas in which no operational discharge of oil or oily mixture from tankers is permitted.

  • Mediterranean Sea area

  • Baltic Sea area

  • Black Sea area

  • Red Sea area

  • Gulfs area

  • Gulf of Aden

  • Antarctica
  • The exact delimiting boundaries of these areas are given in Regulation 10, Section (1).
    Within the special areas, any discharge of oil or oily mixtures by tankers is prohibited. Reception facilities are provided for the cargo residues of tankers trading exclusively within special areas.

    2.13.5 Prohibited zones
    While the IMO 'special areas' protect some international waters, other nations have established regulations to protect their national waters by declaring 'prohibited zones'. In some cases, such zones apply only to national flag vessels.
    The most significant 'prohibited zone' is the 50 miles-from-land exclusion contained in MARPOL Regulation 9 (section 2.13.3 above). The 1962 'International convention for the prevention of pollution of the sea by oil' established 100 mile prohibited zones around the coasts of Canada, Greenland and Iceland, and an extensive 'NE Atlantic prohibited zone' embracing the coasts of Norway, Ireland, the United Kingdom, Western Europe, Spain and Portugal and extending (like a funnel pointing west), as far west as 40 degrees longitude. The United States has also declared a 100 mile prohibited zone around its coast.
    Within the prohibited zones, the discharge of persistent oils, or oily water mixtures containing more than 100 parts per million of persistent oil is prohibited. Special areas or prohibited zones do not apply to segregated or clean ballast discharges.

    2.13.6 Oils spills en route
    Any oil spilled en route must be reported by radio to the nearest coastal state as soon as possible. The report must include:

  • Type and name of the ship.

  • Radio frequency/channel(s) guarded.

  • Name, address and telex numher of the owner and operator.

  • Date and time (UTC) of the spill.

  • Position, course and speed of the ship at the time of the spill.

  • Description of the incident.

  • Damages sustained by the ship.

  • Type of oil involved and the amount spilled.

  • Other cargo on board.
  • Follow-up reports must be submitted as requested by the coastal state.

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