Richey and Adee (1975) emphasize that the sway periods (movement in the 

 direction of wave propagation) of the structure should be long compared to the 

 periods of the incident waves at the site. The longer the structure relative 

 to the crest length of the incident waves, the lower will be the force in the 

 anchor lines. However, the anchor system is a very important component of the 

 floating breakwater installation; hence, the conservative attitude in 

 existence should continue until more substantiating field experience is 

 acquired. 



5. Comparative Cost Estimates . 



Comparative cost estimates for approximating construction cost of various 

 types of floating breakwaters, developed by Adee (1975b) and Jones (1980), 

 are presented in Table 8. A cost comparison is strictly meaningful only if 

 the structures produce the same degree of wave attenuation. The structures 

 presented in Table 8 are of various designs which produce a coefficient of 

 transmission, Ct > peculiar to that specific design. Accordingly, any cost 

 per foot comparison of the structures of Table 8 should be used with the 

 understanding that the effectiveness of the compared structures may not be 

 precisely identical. 



Table 8. 



Comparative 



data for various floating 



breakwaters. 



Breakwater 



Maximum width 

 (ft) 



Weight 

 (lb/ft) 



(approx. ) 



Cost/ft 

 (yr) 



Construction 

 material 



A-frame 1 



28.17 





0.4 



$230 

 (1965) 



Steel frame, 

 wood planking 



Alaska-type 1 



21. 



2,006 



0.4 



$425 

 (1972) 



Lightweight 

 concrete, foam 

 core 



Friday Harbor 1 



25. 



1,965 



0.25 



$320 

 (1972) 



Plastic flotation, 

 wooden deck 



Holmes Harbor 1 



29. 









$197 

 (1973) 



Foam-filled 

 aluminum drainpipe 



Embarcadero 



14. 





0.3 



$275 

 (1973) 



Regular concrete, 

 foam core 



Port Orchard 1 



12. 



1,535 



0.3 



$175 

 (1974) 



Rectangular sec- 

 tion, lightweight 

 concrete, foam 

 core 



Scrap tires 1 



30. 





0.4 



$100 

 (est) 



Scrap tires in 

 bundles 



Tethered float 1 







0.35 



$175 

 (est) 



Plastic float- 

 ing spheres 



Sloping float 2 



90. 





0.5 



$6,000 

 (1980) 

 (est) 



Barge pontoon 



i 



^ost estimate developed by Adee (1975b). 

 2 Cost estimate developed by Jones (1980), 



269 



