The Sitka anchors consisted of a combination of piles and concrete blocks. 

 Jetting was accomplished with high-capacity equipment at the planned anchor 

 location before contracting. Up to 18 feet of penetration was attained in 

 some locations. Steel piles were much more economical to install than con- 

 crete blocks, and when penetration was deemed insufficient to develop the 

 required lateral resistance, a concrete block was installed adjacent to the 

 pile. The anchor line at Sitka was used, regalvanized stud link chain (1-1/4 

 and 1-3/8 inches) proof-tested up to 130,000 pounds. The chain was connected 

 to the pile or concrete block prior to placement. The only underwater work 

 was the installation of one bolt for the lower chain connection and the 

 attachment of the anchor chain shackle (Miller, 1974b). 



c. Olympia Harbor, Washington, Experimental Investigation. The Alaska- 

 type floating breakwater was investigated experimentally by Carver (1979) for 

 potential application at East Bay Marina, Olympia Harbor, Washington. The 

 structure, which was tested in the two-dimensional wave flume, had prototype 

 dimensions of 21 feet wide by 120 feet long (Fig. 41). The 381,226-pound 

 prototype structure was reproduced with a 372-pound model structure. Detailed 

 geometry of the prototype structure is presented in Figure 42. Tests were 

 conducted with two different mooring arrangements — anchor chains crossed and 

 uncrossed (Fig. 43). Wave attenuation tests were conducted in 25 feet of 

 water, with wave periods of 2.5, 3.0, 3.5, 4.0, and 4.5 seconds. Test waves 

 ranged in height from 1.5 o 3.5 feet. Transmitted wave heights were measured 

 one wavelength behind the structure. 



The experimental study results indicated that both anchoring arrangements 

 gave almost identical values for the 2.5- and 3.0-second wave periods; 

 however, the crossed arrangement yielded slightly lower transmitted wave 

 heights for the 3.5- and 4.0-second wave periods, and the differences observed 

 in the model should be representative of the prototype behavior. It appeared 

 that the anchoring arrangement had a wave period-dependent effect on the 

 amount of roll experienced by the structure and, hence, a wave period- 

 dependent effect on transmitted wave heights. Observations of the Alaska-type 

 floating breakwater under test conditions showed that for a 3-second wave 

 period, an incident wave height of 1.5 feet produced a high degree of roll. 

 However, as the incident wave height was increased to 2.0 and 2.5 feet, 

 progressively larger amounts of water washed over the structure and dampened 

 its rotation. The net result was that the transmitted wave heights observed 

 for all three incident wave heights were nearly the same. The coefficients of 

 transmission, C t , versus the relative breakwater width, W/L, resulting 

 from these two-dimensional tests of the Alaska-type floating breakwater are 

 presented in Figure 44. 



d. Potential Prototype Installations . 



(1) Bar Point Harbor, Ketchikan, Alaska . This site lies on the 

 northeast shore of Tongass Narrows, a fjord oriented between bordering 

 mountains which guide the approach of strong winds up or down the channel. In 

 the absence of site wave records, wave conditions were predicted from fetch- 

 speed relationships. Short-term speeds of at least 50 miles per hour can be 

 expected, and with a fetch of 1 nautical mile, a significant wave height of 

 3.2 feet and period of 3.5 seconds can be expected. The magnitude of pro- 

 totype anchor forces is a parameter which should be the subject of further 

 study. In the usual laboratory scale investigation, a relatively short 



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