96 



The earliest recorded use of copper slieathing in San Francisco Bay is that of a 

 group of piles dri\'en in 1870 in the U. S. Army Pier No. 1, at Alcatraz Island. With 

 reconstruction and repair these remained in service until 1907 when they were encased 

 in concrete. 



The Northwestern Pacific Railroad has used piles sheathed with copper and with 

 yellow metal under its docks at Tiburon and Sausalito. Some of these were used as 

 early as 1884. The detailed records concerning these piles are not available, but it is 

 reported that, in the main, they ga\e long life. Some trouble due to the metal being 

 torn by drift or by thieves is reported, but there was no trouble from scour. 



The Northern Pacific Railroad is stated to ha^•e driven some copper sheathed 

 piles in a wharf at Tacoma in 1877 which remained in good condition until the structure 

 was removed in 1898. 



A company which constructed a wharf at Richmond in San Francisco Bay in 

 1903-4 with copper sheathed piles reports the following: 



"These piles were green, well stripped, all knots and projections cut off 

 and finished to a smooth surface. From a point, when driven, about two feet 

 below nuul-line to a point above high water, a heavy saturated felt was 

 applied and nailed on. In turn this was covered with 16 ounce sheet copper 

 closely nailed with copper nails. The work was neatly done and had a very 

 nice appearance, was at that time a little more expensive than creosote and 

 no doubt was an excellent protection against the teredo. It has its dis- 

 achantages in the following ways: the copper being a light material, striking 

 and floating objects would tear it, bay pirates would cut it off, and changes in 

 depth of water due to wharf construction changing tide rips would remove 

 silt below copper co^•ering and allow teredo to enter." 



Several hundred of these piles were driven. About 440 of them had a concrete 

 jacket placed around them in 1908, because the mud had washed away from the bot- 

 tom, exposing wood below the copper. At present, the remainder of the original copper 

 sheathed piles are still in service without ha\'ing had additional protection, and they 

 appear to be in good condition. 



The Southern Pacific Company used yellow metal for making repairs on piling, 

 of the Dumbarton bridge in San Francisco Bay but found that it corroded readily, 

 and thereafter substituted copper for it. 



This tvpe of protection with copper as the covering material can give good service, 

 with a life of 20 years or more, when used under proper conditions. While the cost 

 of copper is high it need onl\- be applied to the portion of the pile from high water to a 

 few feet below the mud line. The disadvantages of the method are that the mud line 

 may be lowered by scour, thus exposing unprotected wood; there is great danger of 

 puncturing and tearing the covering during handling and driving or by the abrasive 

 action of driftwood and boats after installation; and the value of copper often causes 

 it to be torn oft" and stolen. 



PAINT AND COMBINATIONS OF PAINT WITH 

 OTHER MATERIALS OVER WOODEN PILING 



The use of various paints, or applications painted on, to preserve wooden piling, 

 is among the earliest means to be tried, and one of the most persistent. Tar and 

 asphalt have been most often used, but they are shown by experience to be of little, 

 if any, value so applied, at least without special treatment. At the Mare Island Navy 

 Yard an experimental pile which had never been in salt water, and which was brush- 



