66 



in table 4. had an average life of only 12 years, those built subsequent to the plan, 

 shown in table 5, have already had an average life of 22 years. 



GENERAL CONXLUSIOXS 



The foregoing illustrates the importance of the factor of economic life. The chief 

 general conclusion is that physical life should, as nearly as can be forecast, be equal to 

 economic life. As to -what the latter will be, it is obviously impossible to foretell the 

 trend of waterfront development for any length of time with any degree of certainty; 

 however, certain general conditions are likely to prevail. Waterfront locations may be 

 divided into three classifications as follows: 



A. Frontage adjoining property unsuited for future industrial or municipal 

 development. 



Structures located in such territories are likeh' to ha^•e unlimited eco- 

 nomic life provided they in no way interfere with navigation. This class 

 will include bridges and government structures such as fortifications and 

 lighthouses. 



B. Frontage adjoining property suited for future industrial or municipal 

 development. 



Structures located in such territories are likely to have a long economic 

 life, depending on the rate of development of the territory. 



C. Established municipal waterfront property. 



Structures located in territories where no plan of harbor development 

 has been adopted are likely to have an economic life of a compara- 

 tively few years; where a permanent plan has been adopted the range 

 of life should be much greater. 



A\NaT.\L Cost 



Information on the relative annual costs of the various kinds of piling provides a 

 means of judging their relative merits on a fundamental basis. Establishing this 

 annual cost, however, requires accurate data on the physical life of the types, together 

 with all the items of expense involved throughout their complete service — and such 

 data are difficult to obtain. The physical life of any type will var>' with the quality 

 of materials, workmanship, handling and construction practice and the prevailing 

 conditions of use; and information on the items of expense would require records 

 covering a long period — which are seldom, if ever, maintained because of the labor 

 and cost involved. For this reason the elements of life and expense can onh- be esti- 

 mated as accurately as possible from data at hand and an approximate means of 

 comparison secured. However, the results if carefully developed should furnish a 

 correct indication of relative costs, which are not likely to be fundamentally altered 

 by slight changes in actual conditions. 



The following analysis of annual cost has been prepared by Mr. Jerome Newman, 

 formerly Chief Engineer of the Board of State Harbor Commissioners, for six different 

 types of waterfront construction, based on pre-war contract prices. It is belie\ed that 

 the changes in labor and material costs of the past few years have been fairly uniform 

 for the several types of construction considered, and that the pre-war contract prices 

 will show the relations more satisfactorily for future use than will the erratic fluctua- 

 tions which obtained during and following the war. However, any of the assumptions 

 ma\- be changed, and the general method still be used. 



A life of twenty-five years is assumed for creosoted Douglas fir piles, based upon 

 the service of those of the Southern Pacific Co., Oakland, Long Wharf. With good 



