46 



5 Revere Dike Study 



Park Dike, 1991 Profile 



Model construction 



Plans for the proposed park dike were received at CERC from NED, 

 and are reproduced in part in Figure 13. The plans propose narrowing 

 Revere Boulevard and adjacent sidewalks from the current 80 ft to 46 ft 

 and building a mound of random fill covered with a 12-in. layer of top- 

 soil. Design of the mound specified a crest elevation of +27.5 ft mlw 

 (equivalent to 23.0 ft NGVD as seen in Figure 13, where NGVD is Na- 

 tional Geodetic Vertical Datum), a toe wall along the seaward toe at eleva- 

 tion +21.5 ft mlw, a width of approximately 110 ft from toe wall to crest 

 yielding a slope of approximately 1:18.3, and a slope of 1:2.5 on the land- 

 ward side of the dike. Within the dike is a rubble core to provide protec- 

 tion in case the topsoil and random fill are eroded away during a storm. 



In the model, a toe wall was constructed to an elevation of +21.5 ft 

 mlw at a distance of 46 ft shoreward of the seawall as specified in the 

 park dike plans. The dike was constructed with plywood extending from 

 the crest of the toe wall to the crest of the dike, with the area shoreward of 

 the dike crest sealed to retain any overtopping (Figure 14). 



All tests were conducted by first filling the area between the seawall 

 and toe of the park dike with water to allow maximum wave energy to 

 reach the dike. Seawall elevations of +20.9 and +21.3 ft mlw are found in 

 the reach represented by Profile 2; both seawall elevations were tested. 



Three park dike crest elevations were tested. The highest crest eleva- 

 tion was the proposed elevation of +27.5 ft mlw, the lowest elevation was 

 set at +24.0 ft for a seaward slope of about 0.014, and the third elevation 

 was approximately midway at +25.6 ft mlw. 



The model was tested with the 1991 post-storm beach profile which 

 had been constructed during Task B, above, for Profile 2. The beach pro- 

 file had a beach elevation at the seawall of +20.5 ft mlw. Additional tests 



Chapter 5 Revere Dike Study 



