b. Equipment . The following equipment was used for breakwater con- 

 struction: 



(a) Caprolan nylon sandbags. 



(b) Sand-filler hopper. 



(c) Hand-held electric sewing machine. 



(d) 1-cubic yard-capacity (0.76 cubic meter) front-end 

 loader. 



(e) 15-ton-capacity (13.6 metric tons) crane with special 

 bag-grip feature added to the clam jaws. 



(f) Construction plans including bag placement instructions. 



c. Construction Preparation . Before the construction of a breakwater 

 began, a plan for the structure was prepared and a sufficient supply of 

 sandbags was filled and stockpiled. Bags were filled with damp sand from 

 the overhead hopper until at least 75-percent full, as judged by eye, then 

 sewn closed (Figs. 8, 9, and 10). Filling the bags to only 75- to 80- 

 percent capacity simplified sewing the bags closed and increased the sta- 

 bility of individual bags and the structure by allowing the bags to assume 

 a flattened shape, 7 feet long by 4 feet (1.22 meters) wide when lying on 

 their sides, facilitating interlocking among the installed bags. The 

 designs for structures I and II were based on an assumed inplace bag 

 thickness of 1.5 feet (0.46 meter), but surveys after construction indicated 

 an inplace bag thickness of 1.1 feet (0.34 meter), the value used for the 

 revised designs of structures III and IV. 



Before each test, the tank was prepared for construction of a break- 

 water; e.g., for structure 1, the sand bed was graded, then the original 

 simple structural plan was used to diagram bag placement. After structure 

 tests I, II, and III, the tank was drained to inspect the existing struc- 

 ture, remove damaged bags, regrade the sand bed, and make a survey of the 

 base for the next structure. This survey was used to determine the number 

 and placement of bags needed to obtain the desired structure configuration; 

 a bag placement diagram was then drawn showing the location and installation 

 order of each new bag. 



d. Bag Placement . Through-the-water placement was accomplished using 

 only the bag placement diagram as a guide. In accordance with the diagram, 

 the crane bucket would be positioned above the water's surface before drop- 

 ping the bag (Fig. 11). One complete layer was placed before proceeding 



to the next, starting at a tank wall and building a row across to the other 

 tank wall, then back to the original wall in a zigzag pattern until the 

 layer was complete. The water was always too cloudy to visually detect 

 any misplaced bags, but surveys and occasional draining of the tank revealed 

 remarkably good results with this placement method. 



23 



