46 C.F.R. § 153.1112 Prewash for tanks containing Category A NLS residue.
Title 46 - Shipping
Unless §153.1114 allows the prewash to be omitted, a cargo tank that unloads a Category A NLS cargo must be prewashed following the procedures in §153.1120.
Title 46: Shipping
PART 153—SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS
Subpart C—Operations
Approval of Surveyors and Handling of Categories A, B, C, and D Cargo and NLS Residue
§ 153.1112 Prewash for tanks containing Category A NLS residue.

