MEPC 55/23

I:\MEPC\55\23.doc ANNEX 2

RESOLUTION MEPC.150(55)

Adopted on 13 October 2006

GUIDELINES ON DESIGN AND CONSTRUCTION TO FACILITATE SEDIMENT CONTROL ON SHIPS (G12)

THE MARINE ENVIRONMENT PROTECTION COMMITTEE,

RECALLING Article 38(a) of the Conve ntion on the International Maritime Organization concerning the functions of the Marine Environment Protection Committee conferred upon it by the international conventions for the prevention and control of marine pollution,

RECALLING ALSO that the International C onference on Ballast Water Management for Ships held in February 2004 adopted the In ternational Convention for the Control and Management of Ships’ Ballast Water and Sedi ments, 2004 (the Ballast Water Management Convention) together with four Conference resolutions,

NOTING that Regulation A-2 of the Ballast Water Management Convention requires that discharge of ballast water shall only be conducted through Ballast Water Management in accordance with the provisions of the Annex to the Convention,

NOTING FURTHER that Regu lation B-5.2 of the Ballast Water Management Convention provides that, ships constructed in or after 2009 should, without compromising safety or operational efficiency, be designed an d constructed with a view to minimize the uptake and undesirable entrapment of sediments, facil itate removal of sediments, and provide safe access to allow for sediment removal and sampling taking into account Guidelines developed by the Organization,

NOTING ALSO that resolution 1 adopted by the International Conference on Ballast Water Management for Ships invite d the Organization to develop these Guidelines as a matter of

urgency,

HAVING CONSIDERED, at its fifty-fifth se ssion, the draft Guid elines on design and

construction to facilitate sediment control on ships developed by the Ballast Water Working Group, and the recommendation made by the Sub-Co mmittee on Bulk Liquids and Gases at its tenth session,

1. ADOPTS the Guidelines on design and constr uction to facilitate sediment control on ships as set out in the Annex to this resolution;

2. INVITES Governments to apply the Guidelin es as soon as possible, or when the Convention becomes applicable to them; and

3. AGREES to keep the Guidelines under review.MEPC 55/23

ANNEX 2 Page 2

I:\MEPC\55\23.doc ANNEX

GUIDELINES ON DESIGN AND CONSTRUCTION TO FACILITATE SEDIMENT CONTROL ON SHIPS (G12)

1 PURPOSE

1.1 Regulation B-5.2 of the Convention requires th at ships described in Regulations B-3.3 to B-3.5 should, without compromising safety or operational efficiency, be designed and constructed with a view to minimize the upta ke and undesirable entrapment of sediments,

facilitate removal of sediment s and provide safe access to allow for sediment removal and sampling, taking into account these Guidelines. Ships described in Regulation B-3.1 of the Convention should, to the extent practicable, al so comply with Regulation B-5.2 taking into

account these Guidelines.

1.2 The purpose of these Guidelines is to provide guidance to ship designers, ship builders, owners and operators in the development of sh ip structures and equipment to achieve the objectives of paragraph 1.1 and thereby, reduce th e possibility of introducing harmful aquatic organisms and pathogens.

1.3 There may be a conflict between preventi ng accumulation of sediments and preventing the discharge of harmful aquatic organisms and pathogens.

2 INTRODUCTION

2.1 Water taken up as ships’ ballast can contain solid alluvial matter that, once the water is becalmed in a ship’s ballast tank, will settle out onto the bottom of the tank and other internal

structures.

2.2 Aquatic organisms can also settle out of the ballast water and can con tinue to ex ist within the sediment. These organisms can survive for l ong periods after the water they were originally in has been discharged. They may thereby be transported from their natural habitat and discharged in another port or area where they ma y cause injury or damage to the environment, human health, property and resources.

2.3 Regulation B-5.1 of the Convention requires that all ships rem ove and dispose of sediments from spaces designated to carry ballas t water in accordance w ith the Ballast Water Management Plans. These Guidelines are to a ssist ship designers, ship builders, owners and operators to design ships to minimise the reten tion of sediment. Guidance on the management of

sediment is contained in the Gu idelines for Ballast Water Mana gement and the Development of Ballast Water Management Plans (G4).

3 DEFINITIONS

3.1 For the purposes of these Guidelines, the de finitions in the Intern ational Convention for the Control and Management of Ships’ Ballast Water and Sediments (the Convention) apply.MEPC 55/23

ANNEX 2 Page 3

I:\MEPC\55\23.doc 3.2 Ballast Water Tank – for the purposes of th ese Guidelines a ballast water tank is any tank, hold or space used for th e carriage of ballast water as defined in Article 1 of the

Convention.

4 DESIGN FOR REDUCING ACCU MULATION OF SEDIMENT

4.1 Ballast water tanks and their internal st ructure should be designed to avoid the

accumulation of sediment in a ballast tank. The following should, as far as is practicable, be taken into account when designing ballast tanks:

.1 horizontal surfaces to be avoided wherever possible;

.2 where longitudinals are fitted with face bar stiffeners, consideration should be given to fit the face bar stiffeners below the horizontal surfaces to aid drain off from the stiffeners;

.3 arrange for induced flows of water, either by pump forces or gravitational forces, to wash along horizontal or near horizontal surfaces so that it re-suspends already settled sediment;

.4 where horizontal stringers or webs are requ ired, drainage holes to be as large as possible, especially if edge toe-stops are fitted where horizontal stringers are used as walkways, to encourage rapid flow of water off them as the water level in the tank falls;

.5 internal girders, longitudinals, stiffene rs, intercostals and floors, where fitted should incorporate extra drain holes whic h allow water to flow with minimal restriction during discharg e and stripping operations;

.6 where inner members butt against bulkhead s, their inst allation should be such as to prevent the formation of sta gnant pools or sediment traps;

.7 scallops should be located at the joints of the inner bottom (tank top) longitudinals

or intercostals and floors to allow for good airflow, a nd thus drying out of an empty tank. This will also allow air to escape to the ai r pipe during filling so that minimum air is trapped within the tank;

.8 pipeline systems should be designed such that, when deballasting, disturbance of the water in the tank is as powerful as possi ble, so that the turbulence re-suspends sediment; and

.9 flow patterns in ballast wa ter tanks should be studied (for example by the use of Computational Fluid Dynamics (CFD)) and co nsidered, so that internal structure can be designed to provide effective flus hing. The amount of internal structure in double bottom tanks will reduce the scope for improving flow patterns. The hydrodynamic performance of th e ballast tank is crucia l to ensure sediment scouring.MEPC 55/23

ANNEX 2 Page 4

I:\MEPC\55\23.doc 4.2 Any designs depending upon wate r flow to re-suspend sediment should, as far as possible be independent of human intervention, in order th at the work load of ships’ crews is minimal when operating the system.

4.3 The benefits of design concepts for reduc ing sediment accumulation are that there is likely to be good sediment removal while deballas ting, with minimum retention of sediment in the tanks, and therefore a reduction or no need for removal by other means.

4.4 The design of all ships should provide safe access to allow for sediment removal and sampling.

4.5 The design of ballast water ta nks should facilitate installation of high sea suction points

on each side of the tank.

4.6 When practical, equipment to remove suspe nded matter at the point of uptake should be

installed.

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