rubble-mound structure. The remainder of the structures at Keweenaw are tim- 

 ber crib with some rubble and steel sheet piles. 



31. In general, the rubble-mound structures in the Detroit District 

 that show toe stability problems have shown the results of this problem 

 through damage to the upper slope and crown armor. It is not known defi- 

 nitely, but it is expected that the toe damage is a combination of toe armor 

 instability combined with foundation scour and undermining of the structure 

 toes. Repair to a structure is carried out by filling the scour holes with 

 stone and then reshaping and repairing the structure's armor stone layer(s). 

 Some repairs have been successful thus far, while other areas require frequent 

 repair work. 



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