Table 4 



Duluth-Superior Harbor Structures 



Duluth-Superior, Minnesota and Wisconsin 



Date(s) Construction and Rehabilitation History 



1898- The construction of two 1 ,720-f t-long entrance piers at Duluth Ship 

 1900 Canal (Figure 11) occurred during this period. These were timber 

 crib structures filled with stone and timber (oak and pine) with a 

 concrete superstructure (monolith blocks) . The el of the super- 

 structure ranged from +10 to +18 ft Iwd with widths of 24 ft to 36 ft 

 at the structure heads (Figure 12). 



1904- Construction of a 2, 096-f t-long north pier and a 1 ,581-f t-long south 

 1907 pier progressed at Superior Entry (Figure 11). These structures were 



built with concrete. Crest widths ranged from 8 to 11 ft with els 



ranging from +10 to +16 ft Iwd (Figure 12). 



1908- During this time, a 4, 137-f t-long north breakwater and a 1,866-ft- 

 1913 long south breakwater were constructed (Figure 11) at Superior Entry. 

 The pierheads and breakwater heads were timber cribs filled with 

 stone and timber. Crest els were +10 ft Iwd, and widths were 40 and 

 31 ft, respectively, for the pierheads and breakwater heads (Fig- 

 ure 12). The breakwater trunks were rubble-mound structures in- 

 stalled at el +8 ft Iwd (Figure 12) with 1V:1.5H side slopes. 

 Ten-ton armor stone was used. The shoreward ends consisted of con- 

 crete structures installed on rubble (Figure 12) . Crest widths were 

 12 ft, and crest els were +8 ft Iwd. 



1933 A 530-ft-long rubble-mound shore connection was installed on the 



inner end of the north breakwater at Superior Entry. It consisted of 

 an 8-ft crest width at an el of +8 ft Iwd with 1-V:1.5-H side slopes. 



1949 Thirty feet of the outer south pierhead at Duluth Ship Canal was re- 

 built, and 406 ft of the south pier at Superior Entry was rebuilt. 

 These consisted of steel sheet-pile walls and concrete (Figure 12). 

 The pierhead at Duluth Ship Canal was built with a crest width of 

 14 ft at an el of +13 ft Iwd. The pier at Superior Entry was 8 ft 

 wide with an el of +10 ft Iwd. 



1956 Longitudinal cracks on the pierhead in the middle of the super- 

 structures were repaired at Duluth Ship Canal. The repair consisted 

 of horizontal tie bolts through each monolith and reinforcing bars 

 drilled and grouted through the tunnel. After the bars were in 

 place, the tunnel was filled with concrete. No separation of the 

 monolith has occurred since then. 



1957- Twenty-six feet at the inner end of the south pierhead and 1,019 ft 

 1958 at the south pier at Superior Entry were rebuilt using steel sheet- 

 pile walls and concrete (Figure 12). 



(Continued) 



29 



