(b) Comparatively high-berth availability, reducing 

 waiting time for large tankers. 



(c) Need for only small pipelines to shore, because of 

 the onsite provision of temporary storage. 



(d) Possibility of auxiliary uses. 



(e) Relatively low shoreside impact. 



2. Background . 



The concept of prefabricated units floated to the site and sunk into 

 position is not new, although it has been gaining popularity. 



Prefabricated units are a particularly popular concept of breakwater 

 construction in the Mediterranean area, e.g., for a seawall and break- 

 water at the port of Genoa, Italy, and for oil terminals at Gela, Sicily, 

 and at Marsa El Brega near Benghazi, Libya. The concept has also been 

 adapted to the design and construction of other marine structures such 

 as bridge piers, water intakes, and tunnels built by the trench method. 



Unit construction was used to a limited extent during World War II 

 under combat conditions off the invasion beaches of Normandy. With the 

 prime requisites being simplicity, speed of placement with minimal onsite 

 construction operations and adequate serviceability although for a 

 comparatively short time, the units served their purpose well, and within 

 design limits. 



The concept of outer perforations to reduce the force of approaching 

 waves has been incorporated into the breakwater at Baie Comeau, Quebec, 

 and the deepwater concrete storage tank structure for the Ekofisk Field 

 in the North Sea. 



II. DESIGN CONSIDERATIONS 



1. Study Conditions . 



To incorporate some facts and figures into the study, assumptions 

 were made and basic physical conditions established as reasonable design 

 conditions. 



The site was assumed to be off the U.S. east coast and exposed to 

 severe wave action. It was located on a compact sandy bottom deep enough 

 to keep channel dredging at a minimum for deep-draft carriers. Not only 

 is dredging minimized, but also the associated problems of spoil disposal. 



The assumed location would not be greatly affected by tidal currents, 

 and if present, would normally be of small velocity. More important, 

 the site can be chosen so as not to interfere with established traffic 



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