Ballast Water Management Decision Support System - Global Maritime Transport and Ballast Water Management: Issues and Solutions - page 253

Fig. 19 Decision (10) on allowing or not a vessel to discharge unmanaged ballast water (Enhanced
after David 2007 ) (This fi gure can be downloaded from http://extras.springer.com/ )

- voyage duration and other conditions;

- vessels capability to conduct alternative BWM options; and

- the result of RA.

In case a vessel took all measures to comply with the requirements, including
alternative BWM options, then the level of risk posed by the ballast water intended
for discharge needs to be verifi ed. If the ballast water was assessed as of extreme
risk, than the vessel should not be allowed to discharge ballast water, however in
cases when the risk level assessed was intermediate or high, the vessel may still be
allowed to discharge ballast (see Fig. 19 ).
Certainly, this should be understood only as minimum criteria. It is up to each PSA
to decide whether or not to apply a more stringent approach and possibly not allow
discharge of unmanaged ballast water that was assessed as high or even intermediate
risk which would be desirable especially from an environmental perspective.