GUIDELINES FOR APPROVAL OF ALTERNATIVE STRUCTURAL OR OPERATIONAL ARRANGEMENTS AS CALLED FOR IN MARPOL 73/78, ANNEX I, REGULATION 13G(7)

(Adopted by the Resolution MEPC.64(36)
on 4 November 1994)

 

1. Background

 

2. Applicability

 

3. Performance requirements

 

4. Damage and outflow criteria

 

5. Methodology for calculation of the hypothetical oil outflow

 

5.1 Damage assumptions

5.2 Calculation of outflow in case of side damage

5.3 Calculation of outflow in case of bottom damage

5.4 Calculation of total outflow in case of side or bottom damage

 

6. Outflow reducing arrangements

 

7. Operations manual

 

8. Endorsement of the IOPP Certificate/Supplement

 

Appendix.

Arrangement acceptable as alternatives under regulation 13G(7) of Annex I of MARPOL 73/78

 

 

Background.

 

1. Regulation 13G(4) of Annex I of MARPOL 73/78 specifies the requirements applicable to existing crude oil tankers of 20,000 tons deadweight and above and product carriers of 30,000 tons deadweight and above to reduce the accidental outflow of oil in the event of a collision or stranding. Regulation 13G(7) permits other structural or operational arrangements to be accepted as alternatives, provided that such alternatives provide at least the same level of protection against oil pollution in the event of collision or stranding, and are approved by the Administration based on guidelines developed by the Organization.

 

The guidelines contained herein specify the criteria by which the acceptability of alternative arrangements should be determined. Methods approved by the MEPC at the time of development of the guidelines are detailed in the Appendix.

 

Other alternative arrangements may be approved by the MEPC after considering their pollution prevention and safety characteristics. A proposal for approval of a new or revised arrangement should be submitted by an Admi­nistration and contain technical and operational specifi­cations and evaluation of any safety aspects.

 

Applicability.

 

2. These guidelines apply to crude oil tankers of 20,000 tons deadweight and above and product carriers of 30,000 tons deadweight and above which are not required to comply with regulation 13F and do not satisfy the requirements of regulation 13G(1)(c).

 

Performance Requirements

 

3. The required minimum protection against accidental oil outflow is governed by regulation 13G(4), which stipulates that tankers to which regulation 13G applies shall have wing tanks or double bottom spaces, not used for the carriage of oil and meeting the width and height requirements of regulation 13E(4), covering at least 30% of Lt for the full depth of the ship on each side or at least 30% of the projected bottom shell area within the length Lt, where Lt is as defined in regulation 13E(2). Equivalent structural or operational arrangements, as permitted by regulation 13G(7), should ensure at least the same degree of protection against oil pollution in the event of collision or stranding. The equivalency should be determined by calculations in accordance with paragraphs 4 and 5 below.

 

Damage and outflow criteria.

 

4. The oil outflow should be calculated for the damage cases identified in subparagraph 5.1 of these guidelines. The hypothetical outflow should be calculated for the conditions specified in subparagraphs 4.1, 4.2 and 4.3 below and in accordance with the procedures defined in subparagraphs 5.2, 5.3 and 5.4. The hypothetical outflows so calculated, divided by the volume of the cargo being carried by the ship in its original configuration, and expressed as a percentage, constitute the Equivalent Oil Spill number (the EOS number) for the ship under each of the conditions detailed in subparagraphs 4.1, 4.2 and 4.3.

 

4.1 The EOS number should be calculated for the existing ship, with the ship loaded to the maximum assigned loadline with zero trim and with cargo having a uniform density allowing all cargo tanks to be loaded to 98% full. This calculation establishes the base EOS number and also the nominal cargo oil density, which should be applied in the calculations required by subparagraphs 4.2 and 4.3.

 

4.2 A second EOS number should be calculated for the ship arranged with non-cargo side tanks as referred to in regulation 13G(4).

 

4.3 A third EOS number should be calculated for the selected alternative method and should not exceed the EOS number as calculated according to subparagraph 4.2, and should furthermore not be greater than 85% of the EOS number calculated according to subparagraph 4.1.

 

4.4 Fuel oil tanks located within the cargo tank length should be considered as cargo oil tanks for the purpose of calculating the EOS numbers.

 

Methodology for calculation of the hypothetical oil outflow.

 

5. The methodology detailed in this paragraph should be used for calculating the equivalent oil spill number as required by paragraph 4.

 

5.1 Damage assumptions.

 

The damage assumptions identified below should be applied to all oil tanks when calculating the equivalent oil spill number.

 

5.1.1 Side damage.

 

 

5.1.2 Bottom damage