Table 22 



Manistique Harbor Breakwaters 



Manistique, Michigan 



Date(s) Construction and Rehabilitation History 



1887 A 420-ft-long timber crib breakwater was constructed offshore of the 

 site (Figures 59 and 60, Section E) . The structure was about 29 ft 

 wide, and stone was placed on each side of the breakwater. Core 

 stone ranged from 2 to 3 ft in thickness, and cover stone was a mini- 

 mum of 4.5 ft thick. 



1909 A 322-ft-long stone-filled timber crib pier was completed west of the 

 harbor entrance (Figures 59 and 61, Section H) . The pier was approx- 

 imately 20 ft wide and installed at an el of +4 ft Iwd. The lakeward 

 portion of the structure included a concrete cap (cast in place) and 

 riprap toe protection. The rest of the pier consisted of a cap of 

 precast concrete blocks and stone. 



1911- During this time, construction of the east and west breakwaters was 

 1915 completed (Figure 59, Sections A-G) . The 420-ft-long breakwater 



(built in 1887) was capped with concrete and became a portion of the 

 east breakwater. The shoreward 624 ft of the east breakwater and 

 480 ft of the west breakwater (Figure 60, Sections A and B) were con- 

 structed of woodpiling and stone. The superstructure consisted of a 

 concrete cap and stone. The shoreward portion (Section A) was 8 ft 

 wide, and the rest of the structure (Section B) was 11 ft wide. The 

 crest el was +7.1 ft Iwd, and stone was included on both sides. The 

 1,000-f t-long lakeward end of the west breakwater and 300 ft of the 

 east breakwater shoreward of the dogleg section (Figures 59 and 60, 

 Sections C and D) consisted of wooden crib construction with concrete 

 caps. The 300 ft of east breakwater and 500-f t-long shoreward end of 

 the portion of the west breakwater (Section C) were 20 ft wide. The 

 outer 500-ft-long portion of the west structure (Section D) was built 

 24 ft wide. The breakwaters (Sections C and D) had a +7.1 ft Iwd 

 crest el. The outer 400 ft of the east breakwater (Figures 59 

 and 61, Sections F and G) consisted of timber crib construction with 

 concrete caps. The breakwater was 24 ft wide and had a crest el of 

 +7.1 ft Iwd. 



1953 The shoreward end of the east breakwater was extended 200 ft to 



shore and 300 ft parallel to the shoreline (Figures 59 and 61, Sec- 

 tion I). The structure was of rubble-mound construction with 1V:1.5H 

 side slopes. It had an 8-ft crest width and +7.0 ft Iwd crest el. 

 Cover stone on the lakeside ranged from 1 to 3 tons and on the harbor 

 side from 0.5 to 1.5 tons. The structure presently is entirely on 

 shore . 



1957 The superstructure of the inner 924 ft of the east breakwater (Fig- 

 ure 59, Sections A, B, and C) was refilled with stone. 



(Continued) 



99 



