Using the current formula from U.S. Army, Corps of Engineers, Coastal 

 Engineering Research Center, TR-4 (1966) , 



W 



K^, (S^-l)3 cos a 



where 



W = weight of armor unit in primary 

 cover layer (lbs) , 



w^ = unit weight (saturated surface 

 dry) of armor unit (lbs/ft^), 



H = design wave height at the structure, 



S = specific gravity of armor unit, 

 relative to the water in which 

 structure is situated 



S, = 



w^^ = unit weight of water (lbs/ft^), 



a = angle of breakwater slope, measured 

 from horizontal, in degrees, 



Kd = coefficient that varies primarily with 

 the shape of the armor units, roughness 

 of the surface, sharpness of edges, and 

 degree of interlocking, 



a value of Kq = 8.2 for no damage on a 1.5 on 1 slope gives required unit 

 weights close to those used for the island design. CERC TR-4 (1966) 

 recommendations for two layers of tetrapods are Kp = 8.5 for nonbreaking 

 waves on a structure trunk, and Kq = 6.5 on a structure head. 



Tlie seaward face height of +41 feet above MLLW was selected to limit 

 overtopping from a 34- foot wave to an approximate height of 3 feet. As 

 shown in Figure 4, five classes of armor are used in the west face revet- 

 ment. The heaviest is Class A for which the contractor selected the option 

 of using 31-ton precast concrete tetrapods with a specific gravity of 2.40. 

 Precast concrete tetrahedrons were also optional in place of rock for 

 Class A armor. The bid documents actually offered numerous options for 

 each of the five classes of revetment armor since no single developed 

 source of rock material was definitely better than others. The individual 

 minimum weight requirements for Class A, B, C, and D rock were allowed to 

 vary with the specific gravity of the rock. Because weight variations also 



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