Table 4 (Concluded) 



Date(s) Construction and Rehabilitation History 



1960 A hydraulic model investigation (Wilson 1963) was conducted at 



Superior Entry to improve wave conditions in the navigation channel 

 and at the ore docks located opposite the entry. Proposed plans in- 

 volved detached breakwaters lakeward of the existing entrance. Im- 

 provements were never constructed at the site. 



1977- The concrete superstructures of the north and south piers and the 

 1978 substructures at Duluth Ship Canal were inspected. The timber cribs, 

 riprap, and armor protection were determined to be, generally, in 

 good condition. Small gaps were noted along the joints of the cribs, 

 but the timbers were still firm, and no warping was noted. Some 

 cracks were noted in the monolith blocks, but there was no misalign- 

 ment or settlement; and the joints were all tight. 



1984 An inspection of the piers at Duluth Ship Canal was conducted. The 

 north pier was in need of work both above and below the surface, and 

 the south pier was reported in very good condition. An inspection of 

 the Superior Entry inner piers indicated that the structures were in 

 fair condition. In general, the structures needed maintenance, and 

 repairs were done. 



1986 In general, very little maintenance has been needed since construc- 

 tion of the project. Minor patching of spalling concrete has been 

 attempted with generally poor results. The structures overall are 

 presently in fair condition. 



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