Table 61 



Mackinac Island Harbor Breakwaters 



Mackinac Island, Michigan 



Date(s) Construction and Rehabilitation History 



1914 Construction of a 410-ft-long east breakwater and a 950-ft-long west 

 breakwater (Figure 170) was completed. The breakwaters were rubble 

 mound with a crest width of 10 ft and an el of +6.0 ft Iwd. Side 

 slopes were 1V:1.5H. 



1967 A 500-ft-long lakeward rubble-mound extension to the east breakwater 

 (Figure 170) was completed. The extension had a crest el of +8.5 ft 

 Iwd and a crest width of 8 ft. Stone was placed on 1-V:1.5-H side 

 slopes, and cover stone ranged from 3 to 5 tons at the breakwater 

 head and from 2.5 to 4.5 tons on its trunk. 



1986 The stone in the breakwaters has been replenished and replaced peri- 

 odically during its lifetime, and the structures are presently in 

 fair condition. An aerial view of the Mackinac Island Harbor break- 

 waters is shown in Figure 171. 



267 



