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CHAPTER VIII 



MARINE SUBSTRUCTURE MATERIALS 



To the engineer responsible for the design, construction and maintenance of 

 structures in sea water, accurate information on the nature, relative cost, effectiveness 

 and permanence of various kinds of piling and pile protections is of the greatest im- 

 portance. The lack of such information prevents a close estimate of the probable 

 annual cost of structures on piling of different kinds and must result many times in the 

 adoption of uneconomical materials or methods. There is no way to estimate accurately 

 the money value of information of this kind, but when the amount of damage done by 

 marine borers in recent years is considered, or even the annual expenditures in normal 

 years for new construction and repairs, it is obvious that information resulting in but 

 very slight improvement would permit savings of very considerable sums of money. 



Following are descriptions of the more important piling and pile protection 

 materials and methods used in San Francisco Bay and tributary waters, with dis- 

 cussions of their value on the scores above mentioned. Statements respecting per- 

 manence, especially in respect to those materials or types of piling in which that 

 quality is a function of resistance to borer attack, will be understood as applying only 

 to the conditions of this Bay or conditions closely similar to them. These statements 

 rest upon a very large body of service records gathered by this Committee, whose 

 tabulation in detail will be found in Chapter IX. 



UNTREATED TIMBER PILING 



Some species of timber form ideal piling material in respect to form and working 

 qualities. Such an ideal timber should be straight, of regular cross section, strong 

 without excessive weight, resilient, of small taper, available in long lengths when 

 needed, abundant in quantity, and relatively cheap. Ideal quality should also, how- 

 ever, include natural resistance to marine borers and other destructive agencies. 

 There is no species of wood native to North America which is naturally immune to 

 such attacks. There are a number of foreign species for which immunity is claimed, 

 some of which are commented on further in this report; but in every case these are at 

 present either too expensive, or the supply is too limited or uncertain, to permit their 

 use on anything but an experimental basis in this harbor. 



Fig. 30. Green test pile driven at west end of Alameda Distributing Station Dock in December, 

 1920. Pulled November 27, 1923. Depth of water at high tide 25 feet. Original dimensions of pile 

 40 feet long, 14-inch butt, 8-inch tip. 



Pile broke off two feet above mud line when pulled. 



Three inches of sound wood remaining from mud line to lower high water. * 



Practically all destruction by Limnoria; a few Spliaeroma, and no evidence gf Ten-do. 



Three old Bankia burrows found, near nuul line, only. 



