Design Source: The builder utilized design literature from the University of 

 Rhode Island. 



Construction: The first unit was 118.9 m (390.0 ft) in length and 6.1 m 

 (20.0 ft) in width. Primary flotation relied on polyethylene blocks 

 inserted in the tire crowns. The tires were coupled by polypropylene 

 rope. The reconstructed structure was also 118.9 m (390.0 ft) in length, 

 but only 4.0 m (13.0 ft) in width. Primary flotation was derived from 

 polyurethane foam poured into the tire crowns. Steel cable, 3/8-inch 

 diameter, was used to couple the tires. 



Site: 



Installation: The original structure was moored to 10 danforth anchors. 



Seven anchors were spaced evenly along the exposed side of the FTB and 

 three were spaced uniformly on the leeward side. Mooring lines were of 

 3/8- inch steel cable and were 9.1 m (30.0 ft) long. The second 

 breakwater used the same mooring configuration and same type of mooring 

 line, but employed tiedown-type helix anchors in place of the danforths. 



Special Equipment: Four 1-inch-diameter PVC pipes, each 1.2 m (4.0 ft) high, 

 were painted with fluorescent red stripes and positioned atop the FTB to 

 act as navigational markers. 



Field Experience 



Operation: Anchoring system failure was cited as a major problem for the 



original FTB (see Severe Storm Effects), as was structural failure. This 

 latter trouble was the result of the polypropylene rope failing. Fouling 

 growth and inadequate buoyancy were also cited as major problems for both 

 structures. Litter entrapment was considered a moderate problem and 

 corrosion and instability were regarded as relatively minor problems. 

 Given the chance to rebuild the breakwater, the operator would place 

 additional foam in the tire crowns and punch holes in the tire bases to 

 prevent silt from accumulating. Under typical storm conditions with waves 

 0.6 m (2.0 ft) in height and 9.0 m (29.5 ft) in estimated length, the 

 transmission coefficient was 0.20. 



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