20 



4. Creosoted piles; 



5. Pre-cast concrete piles. 



The efforts of the Engineering Department in all new construction 

 are largely directed toward more exacting work than is necessary 

 in inland construction. In the case of concrete the principal desid 

 eratum is density and imperviousness which is obtained by proper 

 proportioning, by the exclusion of sea water or surplus mixing water 

 and by excess tamping. In the case of creosoted and protected piles 

 the principal desideratum is the preservation intact of the protective 

 shell or coating in order to prevent ingress of the borers to untreated 

 timber. The success or failure of each of the above types is directly 

 proportional to the degree of perfection with which these two re- 

 quirements are fulfilled. 



Tabulation of Service Records 

 Existing Structures on the Waterfront of San Francisco 



TYPE Green Piles encased in rectangular concrete piers placed 

 in open coffer dams and carried 2 to 3 feet below mud line: 



Date Number of Condition 1921 



Structure Constructed Supports Inspected ~by Diver 



Ferry 1895 5200 Concrete and piles in first class 



Building Green Piles condition with exception of 5 



Foundation piers opposite ferry slips where 



mud has been partially removed 

 by scouring action of propellers. 

 5 Piles exposed to Xylotrya at- 

 tack. 



TYPE Green Piles encased in concrete deposited inside of steel 

 shells composed of 3/16" boiler plate: 



Date Number of 



Structure Constructed Supports Condition 1921 



Pier 5 1896 130 All cylinders intact, utilized in 



construction of floor 1919 and 20. 



Pier, 20 1896 120 - All cylinders intact and in ser- 



vice. Some cylinders are hollow 

 at mud line according to diver's 

 report. 



