Tidal currents are 1 knot maximum on both flood and ebb. Bottom elevations 

 are -35 feet MLLW under the long leg of the breakwater and -6 feet MLLW at the 

 shoreward end of the short leg. 



Waves estimated at 4 feet in height have been reported coming in from the 

 northwest. Thesa strike the breakwater at an appreciable angle and are atten- 

 uated quite effectively. Ocean swell penetrates the offshore islands and 

 passes through the breakwater. Boat wake is a common loading from the pleas- 

 ure craft, fishing vessels, and the occasional tug which ply the channel. 



c. Breakwater Description. 



(1) Design. The structure was the second one built of the Alaska- 

 catamaran or ladder type, and consists of 3- by 5- by 18-foot reinforced, 

 lightweight concrete pontoons cast over solid polystyrene foam blocks. Three 

 pontoons were posttensioned on site to form 60-foot modules, which were then 

 linked with a chain-rubber back fender connector as illustrated in Figure 9. 

 The main leg of the breakwater is 685 feet long; the shorter one is 275 feet 

 long, with a 3.5-foot draft. 



Anchoring was accomplished with 1-1/4- and 1-3/8-inch galvanized stud-link 

 chain at each module fastened to stake piles. Where the stake piles could not 

 be driven to adequate penetration, as determined by jetting tests before 

 installation, concrete blocks were added to increase lateral resistance; 29- 

 ton units were used on the windward leg of the north-facing (short) leg of the 

 breakwater, and 12-ton units were used on the west-facing (long) leg. A space 

 of about 6 feet is maintained between the two breakwaters at the junction of 

 the "L" base. This design feature was used to avoid stress problems likely 

 with a positive connection. 



(2) Installation. The breakwater was installed in 1973 at a cost of 

 $480 per foot^ Those responsible for the breakwater design, construction, and 

 operation are as follows: 



Owner-Operator: Owned by State of Alaska, but operated 

 by City of Sitka 



Designer: State of Alaska, Juneau 



Division of Harbor Design and 

 Construction 



Design Engineer: D.S. Miller 



Fabricator: Bellingham Marine Industries 

 Bellingham, Washington 



Installation: Units were fabricated in Bellingham and 

 barged to the site. Basic dimensions 

 of the breakwater were chosen to facil- 

 itate shipping and onsite erection with 

 equipment readily available in the 

 area. T.O. Paddock Company, Juneau, 

 was the erection contractor. 



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