At some sites, boat wake loadings may be more important than those from 

 the wind-generated waves. Better models depicting wake loadings are needed. 

 The floating breakwater transmission characteristics are sensitive to the wake 

 from certain hull-speed distance-orientation cases. 



The recently developed analytical methods treating the floating breakwater 

 as a dynamic system are an improvement over static methods, but field data are 

 still needed to refine the values of the various coefficients in the analyses 

 and to verify the general methodology. Possible field installations should be 

 screened as potential field measurement sites. The system being fabricated 

 for Semiahmoo Spit Marina, Blaine, Washington, looks promising because the 

 exposure is such that frequent winds of the 30- to 50-knot range should occur 

 most of the winter season. The water depth is shallow, which will restrict 

 wave buildup. 



The users of the floating breakwaters of the concrete caisson or ladder 

 (Alaskan) type seem to be quite satisfied with their effectiveness and main- 

 tenance costs. Some of this satisfaction is likely attributable to an adjust- 

 ment in expectation of what can be accomplished in reducing wave heights 

 within a given budget, developing adequate mooring techniques, and an aware- 

 ness of crowded conditions at all moorage sites. The use of this type of 

 breakwater seems to be confined to the western Pacific coast. 



Tenakee Springs, installed in 1973, followed by Sitka and Port Orchard 

 (installed in 1974), are the sites with the longest history of performance for 

 the concrete units. Early problems at Tenakee related to alinement and module 

 connections have been corrected; anchor chains are being replaced at Port 

 Orchard. Present design knowledge would have avoided these two problems. 

 Otherwise, the units have performed very satisfactorily. 



The other early breakwater of major dimension (for the area surveyed) was 

 the one at Friday Harbor (installed in 1973) , consisting of large plastic flo- 

 tation tanks with a timber deck. A major storm shortly after installation 

 caused extensive damage. Plans are underway for replacement with a concrete 

 caisson and an enlarged configuration to accommodate the expanding demand for 

 moorages. 



The floating tire breakwaters should be restricted to sites where wave 

 conditions are quite mild. Experiences to date show that, when subjected to 

 an active wave climate, there is a rapid deterioration in buoyancy due to 

 breakdown of flotation and fatiguing of the systems used to hold the tires 

 together. Marine growth will also diminish structural buoyancy. 



Bottom conditions at a proposed site should be determined carefully to 



provide a sound basis for specification of another type. Extra costs have 



been incurred at Ketchikan and at the Friday Harbor Oceanographic Laboratory 

 site due to unforeseen foundation conditions. 



No damage to anchor systems from wave loadings has been reported. Thor- 

 ough anchor inspections are difficult because of marine growths and sedimen- 

 tation. However, there are many instances where an anchor line could be dis- 

 connected at the breakwater and be partially exposed for a more detailed 

 look. The one data point on longevity of anchor chain is that from the Port 

 Orchard installation, where a replacement after 6 years has been necessary. 



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