to avoid the need for bottom preparation before depositing the bottom 

 rock material. If small differences is elevation along the breakwater 

 axis were unavoidable, the casting height of the units could be varied 

 accordingly. 



The cost estimate, with recommended modifications to adjust for local 

 costs, is believed valid for a breakwater located at any point along the 

 northern U.S. east coast as far south as Cape Hatteras. 



b. Precasting and Outfitting Sites . The basic approach for construc- 

 tion of the units is to cast, in a dry basin, the base slab and enough 

 of the walls to permit safe flotation, and to complete casting and out- 

 fitting alongside a pier while afloat. Therefore, the outfitting site 

 must have adequate depth to float the completed empty units (with the 

 possible addition of some stabilizing ballast). The maximum net draft 

 of the largest units is estimated to be 63 feet; hence a 70- foot depth 

 was assumed necessary, including allowance for tide variations and minor 

 ballasting. 



Since the outfitting site will be relatively unprotected, the cost 

 estimate includes three additional units 50 feet in height to be used as 

 temporary protection at this stage of the operation (money should be 

 available for outfitting site protection, though possibly using a 

 different technique) . 



These conditions severely limit possible outfitting locations along 

 the east coast. After considerable study, the north shore of eastern 

 Long Island, fronted by Long Island Sound, located in the vicinity of 

 Port Jefferson, New York, was selected as a suitable site. In this area, 

 70-foot depths occur about one-half mile offshore. To reduce the towing 

 distance from the dry basin to the outfitting pier, and to keep operations 

 close together for supervision during construction, the dry basin site 

 was assumed to be within 5 to 10 miles of the outfitting pier. 



The largest units are designed for 90- to 110-foot depths, and any 

 breakwater site south of Cape Cod would require precasting in Long Island 

 Sound. Suitable precasting sites north of Cape Cod could be found near 

 Portland, Maine. However, for a shallower site near the Delaware or 

 Chesapeake Bays, local precasting sites can probably be found. 



Ocean tow of a completed unit to the breakwater site is estimated to 

 require four 1,200 to 1,500 horsepower, oceangoing tugs for reasonable 

 speed and adequate safety. The tows must be scheduled for suitable 

 weather. The period during positioning and final sinking of the units 

 will also require relatively calm weather with tugs standing by at the 

 site. 



Estimated towing costs were based on a tow from Port Jefferson to 

 Long Branch via Montauk Point. Towing costs for other sites can be 

 obtained by assuming towing rates of approximately $150 per nautical 

 mile. 



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