b. Site Conditions. The important winds come downriver from the east 

 where the^fetcVTis about 1.9 miles. No tidal current measurements have been 

 made at the site, but speeds of 3 to 4 knots have been estimated, with higher 

 speeds possible during periods of peak flood flows. 



Winds blowing down the Columbia River develop waves that break and pass 

 over the top of the breakwater, but have not caused problems with moored 

 boats . 



^ • Breakwate r Design . 



(1) Design and Installation. The breakwater is a caisson-type struc- 

 ture constructed""©! llghtweTght , reinforced concrete cast over Styrofoam 

 blocks in units 3 by 10 feet in the cross section and 12 feet long, drafting 

 about 18 inches. The units are held together with timber walers. The main 

 section parallel to the shore (and river) is 1,073 feet long, and is held by 

 guide pile dolphins spaced about 84 feet apart (Fig. 38). A 233-foot section 

 of breakwater is set at about a 45° angle to the upstream end of the main 

 breakwater to serve as a trash deflector (Fig. 37, b). The breakwater is 

 designed to provide transient moorage and public access with special fishing 

 facilities provided. It was installed in early 1979. Those responsible for 

 the breakwater design, construction, and installation are as follows: 



Owner-Operator: Port of Camas-Washougal , 



Washington 



Project Designer: Parametrix, Inc. 



Vancouver, Washington 



Breakwater Designer-Fabricator: Bellingham Marine Industries 



Bellingham, Washington 



(2) Performance. The wind waves move nearly parallel to the break- 

 water, so they~'are effectively attenuated. The only problem reported is that 

 from the boat wake generated by vessels passing close to the breakwater at 

 high speeds. The trash deflector is not effective. logs tend to jam up on it 

 and then work underneath it and move into the marina. The river current keeps 

 the breakwater snugged up against the pile restraints. 



d. Discussion. The overall system seems to be performing very well, and 

 the owner is satisfied. This site could serve as a field monitoring station 

 for forces on pile-restrained breakwaters, although the river current would be 

 an ever-present additive to the wave loadings from wind or boat. 



III. SUMMAEY AND CONCLUSIONS 



One of the more perplexing problems facing the designer for a floating 

 breakwater is the specification of a realistic wave climate. Local data are 

 rarely available and contemporary methods of developing an appropriate design 

 spectra for the variable fetch conditions usually encountered at potential 

 floating breakwater sites leave much subjective freedom in specifying princi- 

 pal prameters. Hopefully, the two-dimensional wave models being developed 

 will narrow the present zone of uncertainty. 



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