Section 1A(10) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(10)"clean ballast" means the ballast in a tank which, since oil was last carried therein, has been so cleaned that the effluent therein, if it were discharged from a ship which is stationary into clean calm water on a clear day would not produce visible traces of oil on the surface of the water or, on adjoining shorelines or cause a sludge or emulsion, to be deposited beneath the surface of the water or upon adjoining shorelines and if the ballast is discharged through a specified oil discharge monitoring and control system, evidence based on such system to the effect that the oil content of the effluent did not exceed fifteen parts per million shall be determinative that the ballast was clean, not with standing the presence of visible traces referred to above;
