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2. Stronger legislation. — Stronger legislation for the prevention of pollution 

 by oil includes the prohibition of all discharges containing any oil. This is 

 accomplished by requiring either : 



(a) Washing of tanks at unloading point, discharging to a reception facility 

 prior to taking on clean ballast and making the return trip ; 



(b) Retention of all dirty ballast and tank washings, discharging being done 

 at shoreside reception facilities ; or 



(c) The requirement that all vessels carry segregated ballast; and 



(d) Retention of mixtures of bilge water containing lubricating oil which has 

 drained or leaked from machinery spaces. 



Procedures (a) and (b) are essentially the same for U.S. flag vessels. The 

 major difference, aside from locating reception facilities at opix)site ends of 

 routes, is that washing all tanks prior to making a return voyage with clean 

 ballast generates an effluent of lesser volume and greater oil concentration than 

 discharging dirty ballast and tank washings at the end of a voyage. Generally, 

 oil-water separators are more effective for high concentrations of oil in water, 

 making choice (a) the more desirable. With adequate facilities, it is possible 

 that a vessel could choose to either clean its tanks and take on clean ballast 

 prior to making a return trip after offloading its cargo or take on ballast and 

 retain it, along with tank washings, until it reaches a residue reception facility 

 near a loading port. 



The primary disadvantage of using these two methotls entirely for preventing 

 the intentional discharge of oil into the world's oceans is the fact that even the 

 most efficient oil-water separators at reception and treatment facilities will not 

 be 100% effective, resulting in the discharging of oil into the harbors and 

 water bodies adjacent to these facilities. It follows that a continuous discharge 

 of a facility effluent containing approximately 10 ppm oil in water (a figure based 

 on equipment and procedures presently available) will occur, not including the 

 discharge of those fractions of oil which are soluble in water and cannot be 

 removed by separators. 



Whether or not it is more advantageous to the marine environment to dis- 

 charge oil at specific locations within the coastal zone at a fixed rate over an 

 extended period as compared to limited discharges made in open waters is 

 highly problematic due to the lack of information on this topic and the disparity 

 of opinions among persons doing studies in this area. 



One additional factor to consider while looking at proccKlures (a) and (b) is 

 that of time. I'sing procedure (a) would increase vessel voyage time by approxi- 

 mately lO^c : procedure (b) would increase vessel voyage somewhat but not to 

 the extent that procedure (a) would. Therefore, to keep up with shipment 

 demands, an increase in the number of tankers corresponding to the percent 

 increa.se in vessel voyage time would be necessary, incurring costs and an 

 environmental impact appropriate to vessel construction and operation of these 

 additional vessels. 



By requiring that all bilge water containing oil which has drained or leaked 

 from machinery spaces be retained on board for disposal at a shoreside reception 

 facility, this .source of oil pollution would be eliminated. However, this procedure 

 is extremely costly because of the necessity to install appropriate retention 

 systems on the affectefl vessels. For tankers, this is available, in varying degress, 

 because of their oil transfer system, and retention of oily bilge water is being 

 practiced by a good number of vessels so equipped. This is not the case for ships 

 other than tankers. 



The problem of oily bilge water is scheduled to be studied during the 1973 

 IMCO (Conference. Unilateral action by the United States on this problem, 

 besides being costly, would adversely affect competition by T^S. flag vessels on 

 the world market where T)T-e«ently less than 1 percent of the world gross tonnage 

 consists of vessels registered in the U.S. Considering the fact that this source 

 of pollution will be studied at the IMCO Conference this year, any action 

 taken by the T'.S. at this time might turn out to be different than action 

 adopted bv IMCO. Conversion to meet new Convention requirements would then 

 incur additional costs to vessels meeting other standards. 



Segregated ballast helps to eliminate the problem of oily residues and tank 

 washings to a certain degree, thougli this procedure alone will not prevent all 

 oil and oily mixture di.scliarges from Ix'ing made from tankers. Table 5 sum- 

 marizes dita from a "Reymrt on tlie Segregated Ballast Tanker" prepared by 

 the United States for IMCO showing the economic impact and estimated poUu- 



