Regulation 10 Category C—tank washing in Special Areas
Where a Category C substance is unloaded at a port in a Special Area every tank from which such substance has been unloaded shall be pre-washed and the resulting tank washings shall be discharged to a reception facility at the port of unloading unless—
unloading was carried out as required by regulation 7 or to the satisfaction of a Marpol surveyor, and
either
the substance is a Category C substance identified in the ship’s Procedures and Arrangements Manual as likely to result in a residue quantity from any one tank which does not exceed one cubic metre or 1/3,000th of the capacity of that tank, whichever is the greater, or
the substance is not a high residue substance and the residues are to be retained on board for discharge outside a Special Area.