30% (an average of $2,345) and the ground tackle portion 70% (an average of 

 $5,480). A higher percentage of costs for the ground tackle was due to high 

 labor costs associated with sandblasting the chain prior to dip-coating. With 

 three- and four-legged moorings the relative costs of the work should be about 

 the same for the buoy as for the ground tackle. 



It should be noted that the factors affecting maintenance costs of 

 rehabilitating moorings at San Diego may be quite different from those at 

 other NFEC field activities. While conditions in San Diego are severe, condi- 

 tions may be appreciably worse in tropical environments. In cold areas, factors 

 contributing to corrosion should be appreciably less. The mooring maintenance 

 operations at Public Works Center, San Diego are considered to be quite effi- 

 cient, and maintenance costs at other field activities may be appreciably 

 greater. Only a survey of data from other locations could indicate the relative 

 maintenance costs at activities other than Public Works Center, San Diego. 



BUDOCKS Instruction 1153.4B of 9 April 1965 calls for (1) annual 

 inspection of mooring buoys for damage, deterioration or corrosion, and 

 physical condition of the ground tackle connected to the buoy, (2) lifting of 

 buoys from the water every 3 years for painting and required repairs, and 

 (3) hauling out of the water, inspecting, and rehabilitating the complete 

 mooring assemblies every 3 years where there are adverse bottom conditions 

 and every 5 years where there are favorable bottom conditions. Public Works 

 Center, San Diego follows the 3-year program for both buoys and their ground 

 tackle. 



Plastic Buoys. Very few data are available on the costs of maintaining 

 plastic buoys. After 4 years of heavy duty in San Diego Bay, there is no evi- 

 dence of significant deterioration on the hand lay-up buoy that would require 

 removal ashore for repairs in the near future. The buoy at Pearl Harbor seems 

 to have no significant deterioration after 1 year of service, and the overall 

 appearance is better than that of the San Diego hand lay-up buoy after a simi- 

 lar period of time. 



CONCLUSION 



NCEL studies'^ into cathodic protection of moorings indicate that it 

 would be unnecessary to move moorings ashore for maintenance if the chains 

 were protected from corrosion by sacrificial zinc anodes. It would seem logi- 

 cal to utilize in conjunction with such a system a mooring buoy that gives a 

 longer service life between periods of necessary overhaul than that of the 

 presently used steel buoys. A plastic mooring buoy appears to fulfill this 

 requirement. Reinforced plastic navigational buoys have also been shown'* 

 to be less expensive to maintain than comparable steel buoys. 



10 



