volume. They recommend creosote treatment alone rather than dual treatment 

 for fender piles in cases where breakage from impact may limit the useful 

 life before marine borer attack. Appendix B describes their results, in- 

 cluding effects on other mechanical properties. 



In northern waters or where attack by L. tripunctata is not anticipated 

 and Teredo is the only threat, pressure treatment of 3 140 newtons per cubic 

 meter of coal-tar creosote would be sufficient. The effects on properties 

 are described in Appendix B. Other chemicals, such as pentachlorophenol , 

 should not be used in seawater because this chemical will hydrolize. That 

 is, the presence of water will split the chemical bonds and unite with the 

 radical ions of the original compound to form acids and bases. 



Table 34 shows preservative retention requirements as set forth in AWPA 

 Standard C3 for single and dual treatment of wood species most likely to be 

 used for piles in the United States. Preservative retentions in pounds per 

 cubic foot are measured by assay of bore samples. 



Requirements for adequate preservative treatment of piles include 

 minimum penetrations. Penetration requirements for various species of wood 

 piles and use conditions are also set forth in AWPA Standard C3. Penetration 

 tests are made by gauging the penetration distance from the outside face of 

 the pile. Representative preservative penetration requirements for the wood 

 species most frequently used for piles are presented in Table 35. 



Table 35. Representative preservative penetration requirements. 





Foundation or 



Saltwater 





Freshwater 



Dual Treatment 



Southern Pine 



7.6 cm or 90 



8.9 cm or 90 





pet of the 



pet of the 





sapwood 



sapwood 



Coastal Douglas Fir 



1 .9 cm and 85 



2.5 to 4.4 cm and 





pet of the 



85 pet of the 





sapwood 



sapwood. 



(2) Treatment of Pile Cutoffs, Framing Cuts and Holes . After 

 driving treated wood piles in a wood wharf or another structure, excess wood 

 in the piles is sawed off at the desired elevation. This exposes untreated 

 wood at the cutoff, which necessitates some kind of preservative treatment 

 in place. The usual method is to swab the cutoff with creosote, cover that 

 with Irish flax, and add another coat of creosote before placing the pile 

 cap. On inspection, cones of dry rot have been found in the pile tops with 

 the foregoing treatment, after only a few years' service. 



A method which has adequately protected the cutoff areas and is inexpen- 

 sive consists of boring five or six 19.1-millimeter (0.75 inch) holes, about 

 25.4 millimeters (1 inch) apart in a circular pattern, in the untreated area 

 of the cutoff. This is shown in Figure 68. The holes are then filled with 

 a 50-50 mix of liquid coal tar and creosote. A layer of Irish flax is 



261 



