103 



nacles, etc., exposing the pile wood, which is in process of borer attack. A similar life 

 of not more than fn-e years seems probable from current inspections. 



CoiAMiii.\ Paint Process 



This process as used by the San Francisco-Oakland Terminal Railways in 191,1 

 and 1914 was similar to the Paraffine Paint method, and consisted in applying to the 

 piles a coat of the Harbor Brand Compound, a paint made by the Columbia Paint 

 Co. (now the Columbia Wood & Metal Preservative Co.), a coat of burlap soaked in 

 the paint, redwood battens and a final coat of paint. In addition to such toxic value 

 as it has, the composition made l:)y this company has special usefulness for such 

 purposes as painting application to built-up pile spring line ribbons and submerged 

 bracing. This is due to the fact that the composition forms so cohesive a matrix that 

 boards or planking placed in tight surface contact immediately after receiving a 

 heavy application of the compound can hardly be torn apart, after the compound has 

 set, e.xcept with rupture of the wood itself. This adds to the chemical safeguard a 

 mechanical one against the attack of borers in the minute space between built-up 

 members, which is otherwise especialK' \ulneral)le. 



Argentink Quebr.\ciio Process 



In 1920 the San Francisco-Oakland Terminal Railways coated 160 piles with 

 about 20 feet of protection consisting of a coat of "Argentine Quebracho Commercial 

 Paint" produced by the Imp Manufacturing Co., then a layer of H-'n. by 2 in. red- 

 wood battens and a coat of paint over the battens. The second coat of paint was 

 sanded to harden the surface and prevent the piles from sticking together in the rafts. 

 The same process has also been used by the .Six-Minute Ferry Co. at its slip at Crockett. 

 Chemical analysis by the Committee shows no Quebracho in this compound, whose 

 chief constituent appears to be gas tar oil. 



MiSCELL.ANEOUS PROTECTIVE DEVICES FOR WOODEX PiLES 



Several methods have been proposed for pile protection which cannot be classi- 

 fied under any of the above heads. The following are examples: 



THE BUILT-UP PILE 



Much was hoped for this pile at one time. It was a square or rectangular pile 

 built up of separate planks spiked together so as to have, from any direction, the 

 greatest possible number of cracks intercept a path through the pile. This was on the 

 commonly accepted belief that the shipworm would not cross a crack. But whatever 

 the scruples of the shipworm it soon became apparent that Limnoria had none. A 

 layer of felt beneath the outside planks helped somewhat; but the spikes in course of a 

 little time loosened and opened the cracks till they offered shelter instead of discourage- 

 ment to borers. The construction of this t\'pe of pile was not continued. 



FLOAT PROTECTORS 



Floats, loosely fastened around the pile so that they will rise and fall with the 

 tide and keep constantly in motion from wave action have been actively promoted for 

 some years. They are made in various forms. The original idea overlooked the fact 

 that the shipworm borers work mainly below tide levels, and most severely at and 

 near the mud line. Later there were added to the device chain festoons to assist in 

 warding off the borers below the surface tidal range. No record of their commercial 

 use in San Francisco Bay has been found by the Committee, but they ha\e been 



