(2) Wave Conditions. Due to ocean exposure to the east and bay exposure to the 

 north, maximum wave heights during the winter are normally 8 to 10 feet. 



(3) Currents. Basically tidal currents, ranging up to an approximate maximum speed 

 of 2 knots. 



(4) Winds. Prevailing winds are from the southwest with an average measured speed 

 of 11 knots, and a maximum of about 70 knots (U.S. Coast and Geodetic Survey, 1966). 



(5) Storm Surge and Tides (U.S. Army Engineer District, Norfolk, 1973). 



Mean tidal range, 2.5 feet 

 Mean spring tidal range, 3.0 feet 

 Extreme high tides, 7.0 feet 

 Extreme low tides, —3.0 feet 



(6) Sediment Conditions. Medium compact to compact fine sand, with some silt; 

 trace of shells (Sverdrup and Parcel, 1961). 



e. Structural Features (Sverdrup and Parcel, 1961) (Figs. 3 and 4). 



(1) Dimensions of Basic Structure. 



MLW (approximate): 



Length, 1,500 feet 



Average width, 220 feet 



Area, 8 acres 

 Finished grade (approximate): 5 acres 



(2) Side Slopes. 2 on 1. 



(3) Finished Grade. 30 feet above MLW. 



/. Design Data. Preliminary design provided for possibiUty of two layers of protective 

 armor, but outer layer was finally considered unnecessary. 



(1) Design Conditions (Beach Erosion Board, 1960). 



Depth at structure, 32.0 feet at MLW 



Astronomical tide, 2.5 feet at MLW 



Storm surge, 10.0 feet at MLW 



Maximum water level, 12.5 feet above MLW 



Design wave. Significant height, 17.5 feet; period, 8.9 seconds; 



windspeed, 105 mph hurricane (100-year storm) 

 Heavy riprap (Type A), 10 tons per unit; minimum size specified 



(±20 tons used as it came from quarry) 



(2) Model Study (Beach Erosion Board, 1960). A model study was performed at the 

 Beach Erosion Board to confirm the results of design computations with stone sizes versus 

 wave conditions. Five tests were run with varying combinations of wave height, water depth, 

 and number of layers of cover stone. The designed riprap used for cover stone was 

 distributed as follows: Light stone, 6 to 8, and 8 to 10 tons per unit (5 percent each), and 

 heavy stone, 10 to 11 tons per unit (90 percent). 



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