0.2 0.4 0.6 0.8 1.0 1.2 

 Beam to Estimated Wavelength Ratio 



Figure 2. Reported effectiveness of the Goodyear FTB as a function 

 of the ratio of the structure's beam to the estimated 

 length of an incident storm wave. 



average cost of $26.87/m 2 ($2.50/ft 2 ). For freshwater sites, ignoring two 

 extreme cases, total project costs varied from $6.01/m 2 ($0.56/ft 2 ) to $15.03/ 

 m 2 ($1.40/ft 2 ) with an average cost of $10.28/m 2 ($0.96/ft 2 ). The two extreme 

 cases included an FTB project with a rigid pier and dock built atop the struc- 

 ture for an overall cost of $109.62/m 2 ($10.18/ft 2 ) and a city-funded FTB 

 project with unusually high material and labor costs for a final cost of 

 $141.96/m 2 ($13.19/ft 2 ) . This disparity in costs between saltwater and fresh- 

 water sites is logical, because the saltwater FTBs usually must withstand much 

 more severe weather, corrosion, and fouling growth conditions. 



Additional considerations in the cost of an FTB project are the leadtime 

 required to obtain a permit for its installation and the design life of the 

 structure. While these data are not included in the summary sheets, MEM did 

 obtain information on these subjects from the operators. The length of time 

 required for FTB builders to secure a Corps permit varied from 1 to 13 months. 

 The average leadtime required was 5 months. In many cases, the cost incurred 

 was considered negligible and is factored into the total cost estimates given 

 above. The design life of the FTB was variously estimated from 3 to 30 years. 

 The average design life was 13 years. For the four cases where final removal 

 occurred, the disposal cost varied from $2.16/m 2 ($0.20/ft 2 ) to $6.31/m 2 

 ($0.59/ft 2 ) in 1980 dollars. The average disposal cost was $4.88/m 2 ($0.45/ 

 f t ) . A final cost consideration is the maintenance required of an FTB. 

 Little uniform data were available on this matter from the surveys and no 

 general guidelines can be drawn at this time. Reported annual maintenance 

 costs varied between 2.2 percent and 18.2 percent of total construction 

 cost illustrating the wide discrepancy in routine maintenance practices. 



16 



