Table 62 



Mackinaw City Harbor Breakwaters 



Mackinaw City, Michigan 



Date(s) 

 1955 



Construction and Rehabilitation History 



1967 



1986 



Construction of a 600-ft-long causeway, which serves as a breakwater, 

 was completed by local interests (Figure 172). The structure was 

 built of rock and concrete. The harbor side of the structure was 

 lined with vertical sheetpiling, and the lakeward side was con- 

 structed with rubble-mound materials with side slopes of about IV: IH 

 (the natural angle of repose) • 



Construction of a 430-ft-long rubble-mound breakwater (Figure 172) 

 was completed. The breakwater had a crest el of +8.8 ft Iwd with a 

 width of 8 ft. One- to two-ton cover stone was used in construction 

 along with side slopes of 1V:1.5H (Section B-B) . The outer 200 ft of 

 the existing breakwater was authorized for federal maintenance. 



The breakwaters presently are considered to be in good condition. An 

 aerial photo of the Mackinaw City Harbor breakwaters is shown in Fig- 

 ure 173. 





Figure 172. Mackinaw City Harbor, Michigan 

 270 



