Section 30(6) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(6)On every oil tanker the discharge of ballast water or oil-contaminated water from cargo tank areas shall (take place above the waterline, except as follows.-(a)Segregated ballast and clean ballast may be discharged below the waterline-(i)in ports or at offshore terminals;(ii)at sea by gravity; or(iii)at sea by pumps if the ballast water exchange is performed under the provisions of regulation D-l.l of the International Convention for the-Control and Management of Ship's Ballast Water and Sediments:Provided that the surface of the ballast water has been examined either visually or by other means immediately before the discharge to ensure that no contamination with oil has taken place; -(b)oil tankers delivered on or before 31st December, 1979, as defined in sub-rule (46) of rule 1A, which, without modification, are not capable of discharging segregated ballast above the waterline, may discharge segregated ballast below the waterline at sea, provided that the surface of the ballast water has been examined immediately before the discharge to ensure that no contamination with oil has taken place;(c)oil tankers delivered on or before 1st June, 1982, as defined in sub-rule, (33) of rule 1A, operating with dedicated clean ballast tanks, which without modification are not capable of discharging ballast water from-dedicated clean ballast tanks above the waterline, may discharge this ballast below the waterline provided that the discharge of the ballast water is supervised in accordance with clause (c) of sub-rule (8) of rule 18;-(d)on every oil tanker at sea, dirty ballast water or oil-contaminated water from tanks in the cargo area, other than slop tanks, may be discharged by gravity below the waterline, provided that sufficient time has elapsed in order to allow oil/water separation to have taken place and the ballast Water has been examined immediately before the discharge with an oil/water interface detector referred to in rule 32, in order to ensure that the height of the interface is such that the discharge does not involve any increased risk of harm to the marine environment;(e)oil tankers delivered on or before 31st December, 1979, as defined in sub-rule (44) of (rule lA, at sea dirty ballast water or oil-contaminated water from cargo tank areas may be discharged below the waterline, sub-sequent to or in lieu of the discharge, by the method referred to in clause (d) of sub-rule (6):Provided that-(i)a part of the flow of such water is led through permanent piping to a readily accessible location on the upper deck or above where it may be visually observed during the discharge operation; and(ii)such part flow arrangements shall comply with the conditions specified in the Sixth Schedule.
