anchor force, properites of the anchor system that affect overall float mo- 

 tions and internal loads. 



OBSERVATIONS OF PERFORMANCE AND DURABILITY 



Visual comparisons of incident and transmitted wave height indicated that, 

 under all observed wave conditions, the pipe- tire and the concrete breakwaters 

 provided an adequate and very similar degree of wave protection for both wind 

 waves and boat wakes (Photograph 19). Readily apparent was the fact that the 

 concrete breakwater reflected the wave energy, but the pipe-tire breakwater 

 dissipated it through viscous damping. As a result of wave reflection, the 

 windward side of the concrete breakwater was always noticeably rougher than 

 the windward side of the pipe-tire breakwater (Photograph 20). 



Overtopping of the concrete breakwater by waves was quite pronounced 

 (Photograph 21). Sheet flow 3 to 4 in. deep was common. As a result, a lush 

 crop of algae thrived on the deck of the structure, making the surface treach- 

 erously slippery. The actual freeboard of the concrete breakwaters was about 

 13 in. , 4 to 5 in. less than anticipated in the original design. The reduced 

 freeboard undoubtedly contributed to the amount of overtopping. 



The relatively high tension in the anchor lines of the concrete break- 

 water (5,000 lb with the 2,000-lb clump weights and 1,500 lb without the clump 

 weights) appeared to minimize the lateral travel of the floats even during low 

 tides and fast tidal current flows (2 knots). Lateral displacements were esti- 

 mated to be less than 2 ft even when the clump weights were removed. 



Lateral displacement of the pipe-tire breakwater did not appear excessive 

 (about 5 ft), but tidal currents running at a 45° angle to the anchor lines 

 tended to carry the pipe-tire breakwater in a longitudinal direction to the 

 near end of the concrete breakwater, a distance of about 30 ft. 



Water leakage into the hollow end compartments of the concrete breakwater 

 was a serious problem throughout the test. Primary leak points were the 

 "watertight" access hatches and the 2-in. -diameter post-tensioning bolt holes 

 that were used when making the rigid connections between the two floats. Be- 

 cause calculations indicated that the breakwater could sink if the end compart- 

 ments filled, emergency pumping operations were carried out on several oc- 

 casions. Eventually, reworking the hatch covers and filling the bolt holes 

 with sealant reduced the leakage rate to manageable levels. 



116 



