131 



l)l;u-ini; and driving the pWv and dangrr of damaging it in that pniccss; and llir un- 

 (■crtaint>' as to length of life which can be secured. 



With reference to both reinforced concrete cylinder and reinforced concreH- pile 

 constrnction, many engineers are of the (jpinion that the increased cost ol this con- 

 struction is not justified by the degree of ])ernianence so far exhibited. The principal 

 factor which has influenced the early development of this construction in this locality 

 has been the demand for hre-proofing in waterfront structures where cargoes are 

 concentrated aggregating in \alue many times the cost of the structures. As fre- 

 quently happens, the pioneer has paid heavily for the experience of blazing the way. 

 All the early structures were built before the modern scientific studies of concrete 

 construction were disseminated, at a time when not only was the danger ol excessive 

 water and sand contents unknown but such excesses were even thought beneficial, 

 and when concrete of an>- thickness was considered as efticient jtrotection irom the 

 corrosion of steel. 



Notwithstanding tlefects which will admittedly lessen the dural)ilit\' of the actual 

 structures built, engineers who are familiar with these structures belie\e that they 

 indicate the essential soundness and \alue of the t\-pe when constructt-d witli safe- 



Fig. 51. Handling 105-foot concrete pile with 5-point suspension. Pier 3, San Francisco. 



(Board of Slate Harbor Corn's. Photo.) 



guards whose value is now universally recognized. In general it may be stated that 

 high class reinforced concrete cylinder and reinforced concrete pile construction on 

 San Francisco Bay gives promise of outlasting all other types of substructure support 

 with the exception of mass concrete construction. Its high cost necessarily limits its 

 use to structures in which long economic life, fire risk or difficulty of replacement justi- 

 fies increased expense. On the other hand it may be observed, however, that since 



