economic losses by varying degrees. The line labeled "user cost with struc- 

 ture" represents the economic losses at the reduced level, and its shape in 

 this case indicates that the alternative plans along the x-axis are ordered by 

 increasing benefits. The benefits themselves are the difference between the 

 "without project" and "with-project" conditions, as indicated by the line la- 

 beled "user benefits." 



81. Project alternatives which are built so soundly as to preclude de- 

 terioration of any kind would obviously have a tremendous first cost. Most 

 projects therefore accept some minimal level of predictable deterioration and 

 associated maintenance costs in order to reduce the first costs- to an afford- 

 able level. A number of authors have treated this problem as an independent 

 matter, taking for granted that a specific level of benefits is to be achieved 

 by all alternatives. This approach overlooks the situation in public works 

 development in which the "user" or beneficiary is the same agency which must 

 pay the life cycle project cost. A true optimum plan must minimize all costs, 

 i.e., the economic losses and the structure life cycle costs. 



82. Additionally, Figure 15 shows the hypothetical ensemble of alterna- 

 tives to be ordered in terms of increasing first cost, as indicated by the 

 shape of the line labeled "structural first cost." The increasing first costs 

 are taken in this idealized representation to correspond to reduced mainte- 

 nance liability as indicated by the line labeled "structural maintenance cost" 

 which slopes in the opposite direction. The sum of these costs for each al- 

 ternative is shown as "total structural cost," with a minimum in the vicinity 

 of alternative 5. The sum of the total structural cost and the user cost with 

 structure is shown as the line labeled "total cost with structure." This line 

 dips below the "user cost without structure" line at a point where the bene- 

 fits first exceed the costs. The region where benefits exceed the costs has 

 been shaded and labeled as "project feasibility." The alternative with the 

 maximum vertical spread in this shaded area has the maximum net benefits, in- 

 dicated by the optimum point on the line labeled "net benefits." This point 

 corresponds to the point of minimum total cost with structure, somewhere 

 around alternative 9. 



83. It is useful to note that the optimum can be identified without 

 knowledge of the without-project condition. Port and harbor projects are of- 

 ten justified in terms of transportation savings over some alternate route or 

 through some other existing port. The user cost with project would in these 



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