omitted from the construction. Localized scour had undermined the armor stone 

 toe and resulted in the slippage failure. The structure was repaired by ex- 

 cavating around the perimeter of the structure down to firm bottom and over- 

 laying the structure head with an additional layer of 1- to 2- ton armor stone 

 which extended down to the toe. This repair was feasible due to the shallow 

 depth of the sand in the area of the west breakwater. No stability problems 

 have been observed since the repair was completed. 



North Pacific Division 



Seattle District 



13. The south jetty at the entrance to Grays Harbor, Washington (Fig- 

 ure 4), has sustained severe scour on the channel side toe. The outer 

 5,600 ft of the jetty are presently below mean lower low water (mllw) . It is 

 not known if the toe scour is the cause, or a portion of the cause, of the 

 present deteriorated condition of the jetty. Presently, no repair work is 

 planned for the Grays Harbor Jetties. 



14. As of August 1985 plans were being developed for the repair of the 

 rubble-mound breakwaters at Edmonds Harbor, Washington (Figure 5), It is not 

 definitely known that toe stability was a cause of some of the existing 

 damage, but it is thought to be a probable cause. The bottom drops off on a 

 IV: 2H slope to a deep depth just out from the toe of the breakwaters. There 

 is some thought that this deep water adjacent to the structure, which allows 

 large amounts of wave energy to reach the structure, could be initiating toe 

 stability problems. No firm decisions had been made on the repair design when 

 this report was being prepared. 



Portland District 



15. The north jetties at the mouth of the Columbia River, Tillamook 

 Bay, Yaquina Bay, Siuslaw River, Coos Bay, and Rogue River, the south jetties 

 at Nehalem Bay and Umpqua River, both jetties at the Chetco River, and Jetty 

 "A" at the mouth of the Columbia River have all shown toe stability problems. 

 The problems at these 11 sites (Figures 6-14) are the result of one or a 

 combination of the following: (a) ebb and/or flood flows training on the 

 channel side of the jetties which undermine the jetty toes, displace the toe 

 berm stone or a combination of both, (b) wave- and flow- induced displacement 

 of toe berm armor and foundation scouring and undermining at the jetty heads, 



13 



