Table 1 



Grand Marais Harbor Breakwaters 



Grand Marals, Minnesota 



Date(s) Construction and Rehabilitation History 



1883- A 300-ft-long rock-filled timber-crib breakwater was constructed at 

 1884 the site (Figure 5, Sections E and F) during this period. The outer 

 48 ft of the structure (Figures 5 and 6, Section E) was built 40 ft 



in width, and the remaining 252 ft (Figures 5 and 6, Section F) 

 was constructed 30 ft in width. 



1901- A 350-ft-long rock-filled timber crib breakwater was constructed west 

 1902 of the first structure during this period (Figures 5 and 6, 

 Section D) . The structure was built 24 ft wide. 



1925 A concrete cap (superstructure) was constructed on the outer 48 ft of 

 the structure built during 1883-84. The crest el was +7 ft Iwd (Fig- 

 ure 6, Section E) . 



1926 A concrete cap (superstructure) was completed on the 30-ft-wide, 

 252-ft-long structure built during 1883-84. The crest was con- 

 structed at an el of +7 ft Iwd (Figure 6, Section F) . 



1933 A concrete cap (superstructure) was installed on the breakwater built 

 during 1901-02. The crest el was +7 ft Iwd. Heavy riprap was placed 

 on both sides of the structure (Figure 6, Section D) . Also in 1933 a 

 43-ft-long concrete breakwater connecting the east breakwater to 

 shore was constructed (Figure 5, Section G) . The structure was 12 ft 

 wide and had a crest el of +7 ft Iwd (Figure 6, Section G) . 



1959 Construction of a 921-ft-long rubble-mound inner breakwater was com- 

 pleted (Figure 5, Section A). Cover stone, a minimum of 2 tons, was 

 placed on the outer 550 ft of the structure, and 1-ton (minimum) 

 cover stone was placed on the remaining part of the breakwater. The 

 crest el was +6 ft Iwd with an 8-ft width. The structure had side 

 slopes of 1V:1.5H (Figure 6, Section A). The inner breakwaters were 

 model tested (Fenwick 1941, 1944). 



1972 A 65-ft-long rubble-mound breakwater connecting the shore to an is- 

 land (Figure 5, Section B) and a 40-ft-long rubble-mound breakwater 

 connecting the island to the east breakwater (Figure 5, Section C) 

 were constructed. These structures were built with stone ranging 

 from 5 to 20 tons and had crest els of +6 ft Iwd (Figure 6, Sec- 

 tions B and C) . Model testing of these structures was conducted 

 (Fenwick 1941) . 



1981 A survey of the structures revealed spalling of the concrete at sev- 

 eral locations, particularly on the lakeside of the east breakwater. 

 The rubble-mound shore connection of the west breakwater required 



(Continued) 



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