routes and to avoid any serious navigation hazards or obstructions. 



For the basic system, it was assumed that protected berthing for 

 two 500,000 deadweight ton-supertankers, and offshore storage facility 

 for 10 million barrels of oil were to be provided. These conditions 

 dictate a location in 110-foot depth, and a minimum breakwater length 

 of 8,600 feet. 



Other inherent advantages which should not be overlooked, in line 

 with the basic concept, are: 



(a) Prefabrication is easier under yard conditions in a 

 protected coastal area. This leaves only a few difficult 

 onsite operations. 



(b) Use of massive gravity-type units will eliminate the 

 need for special anchorage systems to maintain location on 

 the final site. 



(c) This construction is suitable for the use of 

 reinforced concrete, particularly for permanent structures in 

 an open sea environment, and with a high resistance to the 

 abrasive and corrosive action at such a location. 



(d) The general scheme of oil storage being confined to 

 the interior compartments of the structure provides an almost 

 leak-proof system. Protection for these compartments against 

 ship collision damage from the seaward side is provided by 

 both the wave chamber and the grout-filled crash barrier; and 

 from the harbor side, by the sand-filled exterior compartment. 

 As an added precaution, lining the inside of all exterior sides 

 of the storage compartments with light steel plate or plastic 

 will guard against seepage through these surfaces. 



2. Selection of Design Wave . 



Since the study was not made for a particular location, the design 

 significant wave height was taken as 32.1 feet, which gives maximum wave 

 height equal to 1 .87 X 32. 1 = 60 feet. 



The 60-foot wave was selected from storm data in the Atlantic region 

 and other data using hindcasting methods to obtain wave characteristics. 



The maximum water surface elevation (astronomical tide plus storm 

 surge) was assumed to be 10.0 feet. 



The wave period used to proportion the structure was selected as an 

 average of the periods obtained using two approaches: 



11 



