46 CFR § 153.1122
Discharges of NLS residue from tank washing other than a prewash: Categories A, B, and C
April 15, 2021
Tank washings that do not result from a prewash and that contain Category A, B, or C NLS residues must be discharged to a reception facility or discharged to the sea under §153.1126 or §153.1128 except those tank washings resulting from washing a tank that has been cleaned following a ventilation procedure in the approved Procedures and Arrangements Manual.