65 



sul)SL't|uuiit to that tiiiK' wliicli no longer exist. The period from 1878 to 1892, when 

 the last of these 14 was hiiiit, represents the time in which the plan oi harbor develop- 

 ment was being worked out, and it is to be expected that some whar\es built during 

 this ]5eriod would not conform to the final plan. It may be noted that the life of two 

 of these structures was only 15 years, wiiile one buiU in 1865 served for 49 years. 

 This bears out the general fact that in a harbor where rapid development is taking 

 ])lace the economic life of wharves may have a very wide range, this life having varied 

 in San Francisco from a comparatively few \ears to 50 years, with an average of 

 about ,^0 years. 



\\'har\es built of short li\ed piling are likely to be changed whenever the necessity 

 arises. Since development of an industrial harbor is predicated' on maximum efificiency 

 of freight handling and transportation, all temporary facilities which hinder or ob- 

 struct such de\elopment must ultimately make way for it. As an example of this, the 

 Fishermen's wharves listed in table 4, built of temporary construction, occupied a 

 space which ultimately became more urgently needed for a large freight pier; hence 

 after 15 years, when they were no longer serviceable, they were abandoned and re- 

 placed by such a pier. The new Fishermen's wharves were then built farther north, 

 outside the area of shipping piers, where movement of the small fishing craft would 

 nf)t interfere with other traffic. From many standpoints this relocation was desirable, 

 and the temporary or short lived piling used in their construction made the relocation 

 possible without material financial loss. 



Another such instance is furnished by the ferry slips listed in table 4, which had 

 an average life of 12 years. These facilities were no less urgently needed than freight 

 piers, but because their design required them to be built with flexible timber piling, 

 they were of necessity shorter lived and could readily be relocated at the expiration of 

 their life when such relocation was desired. 



When physical life exceeds economic life to any large degree the money loss 

 involved in sacrifice of unrealized physical life tends to retard destruction or replace- 

 ment until the loss from inadequate service rendered by the outgrown structure 

 equals — in man>' cases until it largely exceeds — the anticipated physical loss in re- 

 placement. In harbors undergoing comparatively slow development such facilities 

 may safely have a long life. The Southern Pacific Company Oakland Long Wharf 

 extension, 4200 feet long, built in 1869-71 of timber piling, remained in service until 

 1919, or about 49 years, before a change in the Government pierhead line required its 

 removal. That the creosoted timber piling of which the structure was built was 

 entirely adequate was shown by the fact that, at the date of its removal, much of it 

 was pulled and redriven elsewhere; a greater investment in more permanent material 

 would have increased the economic loss when removal became necessary. This same 

 company is operating a ferry slip at the end of Oakland Mole — from which the long 

 wharf extended — originally built in 1881, or 44 years ago; also car ferry slips at Benicia 

 and Port Costa originally built in 1879, or 46 years ago, all of timber piling. 



The existing San Francisco structures listed in table 5 are shown to have had 

 an average economic life of 20 years to date, with a maximum of 49 years; all were 

 built subsequent to establishment of the present waterfront line. By a coincidence 

 the present structure of the Pacific Street wharf (Pier 5) which has had the longest 

 economic life, is also the oldest now in the harbor, having been in ser\-ice since 1896, or 

 29 years. These structures are likely to remain for many years to come, and illustrate 

 the fact that wharves built according to an established ultimate harbor plan can 

 be expected to have a greatly increased economic life. It is of interest to note that 

 while the ferr\' slips built prior to establishment of the present harbor plan, as shown 



