(a) Unless Sec. 153.1114 allows the prewash to be omitted, a cargo tank from which a Category B NLS is unloaded must be prewashed using the procedures in Sec. 153.1120(b) if the tank--
(1) Operates under the interim standard in Sec. 153.481(b); or
(2) Has a waiver issued under Sec. 153.483.
(b) Unless Sec. 153.1114 allows the prewash to be omitted, a cargo tank from which a Category C NLS is unloaded must be prewashed using the procedures in Sec. 153.1120(b) if the tank has a waiver issued under Sec. 153.483.