(a) Step 1— Determine the economic study area. 

 Delineate the economic study area that is tributary 

 to the proposed harbor and channel improvement. 

 Assess the transportation network functionally relat- 

 ed to the studied improvement, including the types 

 and volumes of commodities being shipped, in 

 order to determine the area that can be served 

 more economically by the improvement. Include for- 

 eign origins and destinations in this assessment. 

 Consider diversion from or to adjacent competitive 

 harbors as well as distribution via competing modes 

 of transport. It should be recognized that the lines 

 of demarcation for the economic study area are not 

 fixed and that the area may expand or contract as 

 a result of innovations or technological advances in 

 transportation and/or production or utilization of a 

 particular commodity. The economic study area is 

 likely to vary for different commodities. Combina- 

 tions of economic areas will result in a trade area 

 delineated specifically for the improvement under 

 study. However, in many cases, due to the close 

 proximity of adjacent harbors to the proposed im- 

 provement, the economic study area may be the 

 same as, or overlap with, such adjacent harbors. 

 Therefore, in the final delineation of the economic 

 study area for a given improvement, there should 

 be adequate discussion of the trade area relative to 

 adjacent ports and any commonality that might 

 exist. 



(b) Step 2— Identify types and volumes of com- 

 modity flow. To estimate the types and volumes of 

 commodities that now move on the existing project 

 or that may be attracted to the proposed improve- 

 ment, analyze commerce that flows into and out of 

 the economic study area. This analysis provides an 

 estimate of gross potential cargo tonnage; the esti- 

 mate is refined to give an estimate of prospective 

 commerce that may reasonably be expected to use 

 the harbor during the period of analysis in light of 

 existing and prospective conditions. If benefits from 

 economics of ship size are related to proposed 

 deepening of the harbor, the analysis should con- 

 centrate on the specific commodities or types of 

 shipments that will be affected. Thus, an historical 

 summary of types and trends of commodity ton- 

 nage should be displayed. The considerations gen- 

 erally involved in estimating current volumes of 

 prospective commerce are: 



(1) If the plan consists of further improvements to 

 an existing project, statistics on current waterborne 

 commerce will provide the basis for evaluation. For 

 new harbors with no existing traffic, or for existing 

 commodity movements that may be susceptible to 

 diversion from adjacent harbors, basic information 

 is collected by means of personal interviews or 

 questionnaires sent to shippers and receivers 

 throughout the economic study area. Secondary 

 commercial data are usually available through State 



and local public agencies, port records, and trans- 

 portation carriers. In the case of new movements, 

 give attention to resource and market analyses. 



(2) After determining the types and volumes of 

 commodities currently moving or expected to move 

 in the economic study area, it is necessary to 

 obtain origins, destinations, and vessel itineraries in 

 order to analyze the commodity types and volumes 

 that are expected to benefit from the proposed im- 

 provement. Commodities that are now moving with- 

 out the project but that would shift origins or desti- 

 nations with the project, as well as induced move- 

 ments, should be segregated for additional analysis 

 (see steps 5 and 6). A study should be made of 

 various alternatives for the existing traffic and of 

 new traffic susceptible to diversion from alternative 

 harbors or other modes of transportation. The ob- 

 jective of such a study is to determine the type and 

 volume of those commodities for which savings 

 could be affected by movement via a proposed 

 navigation improvement and the likelihood that 

 such movements would occur. Cost reduction 

 benefits sufficient to divert traffic from established 

 distribution patterns and trade routes are navigation 

 project benefits. In determining the likelihood of 

 prospective commerce, particular attention should 

 be given to alternative competitive harbors in the 

 case of new movements and to hinterland traffic. 

 Elements of analysis of current tonnage include: 

 size and type of vessel, annual volume of move- 

 ments, frequency of movements, volume of individ- 

 ual shipments, adequacy of existing harbor and 

 transportation facilities, rail and truck connections, 

 and service considerations. Generally this prospec- 

 tive traffic is the aggregate of a large number of 

 movements (origin-destination pairs) of many com- 

 modities; the benefit from the navigation project is 

 the savings on the aggregate of these prospective 

 movements. 



(c) Step 3— Project waterborne commerce. De- 

 velop projections of the potential use of the water- 

 way under study for selected years from the time of 

 the study until the end of the project life, over time 

 intervals not to exceed 10 years. Document com- 

 modity projections for the commodity groups identi- 

 fied in step 2. 



(a) The usual procedure for constructing com- 

 modity projections is to relate the traffic base to 

 some type of index over time. Indices can be con- 

 structed by many different methods, depending on 

 the scope and complexity of the issue under con- 

 sideration and the availability of data and previous 

 studies. 



(b) Generally, OBERS projections are the demo- 

 graphic framework within which commodity projec- 

 tions are made. There are many instances, howev- 

 er, in which a direct application of OBERS-derived 



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