APPENDIX 2
GUIDANCE ON SAYETY ASPECTS OF BALLAST WATER EXCHANGE AT SEA
1 Introduction
1.1 This document is intended to provide guidance on the satety aspects of ballast water exchange at sea. The different types of ships which may be required to undertake ballast water exchange at sea make it presently impractical to provide specific guidelines for each ship type. Shipowners are cautioned that they should consider the many variables that apply to their ships. Some of these variables include type and size of ship, ballast tank configurations and associated pumping systems, trading routes and associated weather conditions, port State requirements and manning.
1.2 Ballast water exchange at sea procedures contained in relevant management plans should be individually assessed for their effectiveness from the environmental protection point of view as well as from the point of view of their acceptability in terms of structural strength and stability.
1.3 In the absence of a more scientifically based means of control, exchange of ballast water in deep ocean areas or open seas currently offers a means of limiting the probability that fresh water or coastal aquatic species will be transferred in ballast water. Two methods of carrying out ballast water exchange at sea have been identified:
.1 the sequential method, in which ballast tanks are pumped out and refilled with clean water; and/or
.2 the flow-through method, in which ballast tanks are simultaneously filled and discharged by pumping in clean water.
2 Safety precautions
2.1 Ships engaged in ballast water exchange at sea should be provided with procedures which account for the following, as applicable:
.1 avoidance of over and under-pressurization of ballast tanks;
.2 free surface effects on stablily and sloshing loads in tanks that may be slack at any one time;
.3 admissible weather conditions;
.4 weather routeing in areas seasonably affected by cyclones, typhoons, hurricanes, or heavy icing. conditions;
.5 maintenance of adequate intact stability in accordance with an approved trim and stability booklet;
.6 permissible seagoing strength limits of shear forces and bending moments in accordance with an approved loading manual;
.7 torsional forces, where relevant;
