378 



range from 300 to 5,000 ppmp at discharge.' Without an improvement in LOT 

 technology, it appears that this procedure is not an acceptable solution to meet 

 the requirements of the bill for discharges made beyond 50 miles of the nearest 

 land. Even with improvement, LOT will not normally meet the requirements for 

 discharges made within 50 miles. It should be pointed out here that ballast is 

 primarily discharged outside of loading points. With the U.S. exporting very 

 little oil, and all coastal oil trade being i>erformed by U.S. ves.sels, the impact of 

 foreign flag vessels will be minimal since they discharge their ballast and tank 

 washings near the loading jjoint where they pick up their crude oil loads. 



Of all procedures, the most eeffctive means of preventing oil discharges on 

 coastal trips is by retention of dirty ballast and tank washings or use of clean 

 ballast. 



To measure oil in water concentrations of discharges from ships other than 

 tankers and discharges from machinery space bilges of tankers, vessels must pres- 

 ently depend on visual inspection of the effluent to detect discharges in approach- 

 ing the 100 ppm limitation (under most conditions a discharge becomes \-i.sible at 

 well under 100 ppm of oil in water). Equipment to mea.sure the oil concentration 

 is not off-the-shelf hardware at this time. However, the Coa.st Guard is evaluat- 

 ing a system for shipyard use that proce.s.ses machinery .si)ace bilge water wliich 

 produces an effluent under the 100 ppm limitation while retaining that portion of 

 the bilge water that would produce an effluent in excess of 100 ppm. 



Great Barrier Reef Consideration 



The first of the 1971 amendments to the Convention being implemented by this 

 bill applies the distance from land criterion for discharges of oil and only mixture 

 to the area of the Grea-t Barrier Reef near Australia as if it were land. This will 

 help preserve the reef in its natural state free from pollution caused by oil dis- 

 charges from ships. 



Tank Size/ Arrangement Limitations 



The other amendments included in the bill relate to the arrangements of 

 vessel tanks and limitations of tank size for new tankers. The objectives of those 

 amendments are to place an upper limit on the quantity of oil which can escape 

 into the sea as a result of collision or other vessel casualty. Annex C to the Con- 

 vention would make formulae available for design computations in connection 

 with tank arrangements and size for tankers built subsequent to the effective date' 

 of the amended convention. Also, certain ships even now under construction would 

 have to comply with the tank arrangement and size limitations within two years 

 after the date the Convention comes into force. That provision would apply to 

 tank vessels presently under construction which will be completed after 1 January 

 1977 and to vessels completed before this date but which were started after 1 

 January 1972. 



Annex C sets controls on the size and arrangement of tanks in that it stipulates 

 a limit of oil outflow, calculated in accordance with the formulae of Annex C. on 

 the ba.sis of assumed conditions of .severe injury, and taking account of the tank 

 volume along with the provision of double bottoms, wing voids, or interrupted 

 arrangement of full and empty tanks. This oil outflow limit shall not exceed 

 30,000 cubic meters for vessels' up to 420,000 deadweight tons and 40 000 cubic 

 meters for vessels over 1.000.000 deadweieht tons. The limit is a function of 

 the vessel size between 420.000 and 1.000.000 tons. 



The 1971 amendment dealing with tank size and arrangement was the result 

 of the concern of nations participant to IMCO. indudin? the V . S.. that construc- 

 tion of large tankers without accomoanying control of size or internal arrange- 

 ment of cargo tanks could lead to the possibil'tv. in the event of a single ac- 

 cident, of catastrophic environniental iWlution. This is based on the fact that as 

 tankers have become lareer and larger, tank size has nrorortionailv become 

 larger. In some ca.ses, the numbers of cargo tanks ver tanker have decreased as 

 lar'^er tankers have been built, causing an even greater increase in the volume 

 of tanks. The IMCO Subcommittee on Shin Design and Enuipnient deve'op^^d this 

 amendment with the intention of encouraging design features which would mini- 

 mize the oil outflow resulting from a collision or stranding. This I>fCO action 

 recognized that despite increastnl oi>eration safety measures, it is not possible 

 to eliminate entirely acHdents wh'ch U>ad to the release of oil. However, it is 

 possible to minimize the ensuing oil outflow. 



1 Ihid. 



