the bay. In this capacity, it was twice towed over to the facility, where 

 it remained for a month each time, before being returned to the Jamestown, 

 site. 



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

 Rhode Island. 



Construction: This FTB is 61.0 m (200.0 ft) long and 3.7 m (12.0 ft) wide. 

 Primary flotation originally relied on air trapped in the tire crowns. 

 After sinking in 1977, the FTB was retrofitted with polyethylene blocks 

 inserted in the tires. Rubber conveyor belting fastened by nylon bolts is 

 used to couple the tires. Rope is used to couple the modules. 



Site: 



NARRAGANSETT BAY 



I 1 1 



25 50m 



IN 



T 



Installation: The breakwater is anchored to four 908-kg (2,000 lb) concrete 

 blocks spaced evenly along the structure's exposed side. Mooring lines 

 are of chain and are 22.9 m (75.0 ft) in length. 



Field Experience 



Operation: Inadequate buoyancy is cited as a major problem and fouling growth 

 as a moderate one. Together, these problems were most vividly apparent in 

 1977 when the structure sank. Since then, polyethylene blocks have been 

 added, though this still has not fully resolved the problem. Structural 

 failure with strands of modules breaking loose due to rope failure is 

 considered a minor problem. Interference with boating traffic and litter 

 entrapment are also regarded as minor problems. Under moderate wind 

 conditions, around 25 km/hr (14 kn) , with waves 0.3 m (1.0 ft) in 

 height and 3.9 m (12.8 ft) in estimated length, the transmission 

 coefficient is 0.10. 



Maintenance: Scheduled maintenance consists of blowing compressed air into 

 the structure three to four times per year. 



Severe Storm Effects: During an exceptionally bad storm in October 1980, 



winds reached 113 km/hr (61 kn) and seas were very rough. Under these 

 conditions, the FTB provided no effective protection to the facility, but 

 suffered no damage itself. 



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