CHAPTER III. 

 PRELIMINARY EXAMINATIONS AND SURVEYS. 



General. When the improvement of a stream is proposed, the actual work must 

 be preceded by the collection of data relative to its principal features. The care and 

 elaborateness with which the procuring of this information is to be undertaken will 

 depend to a great extent upon the importance of the proposed project ; but, as a general 

 thing, a survey of more or less completeness will be required. This should include 

 not only the topographic features but also those of a hydrographic nature. It should 

 determine the course, slope, depth, velocity, and discharge, as well as the character of 

 the bed and banks, together with all the topography necessary to the preparation of a 

 complete map. 



Usually a river survey by the United States Government is preceded by a prelimi- 

 nary examination and report, the object of which is to determine the general features, 

 the commerce, and the advisability of improvement, together with its character and 

 probable cost. 



Preliminary Examination and Report. When it is proposed to undertake the improve- 

 ment of a river, or of part of a river, it is first necessary that Congress order a 

 preliminary examination. This order usually states the general character of the pro- 

 posed improvement, that is, whether by locks and dams or by removal of obstructions, 

 etc., and as soon as practicable after the passage of the law the engineer officer in whose 

 charge the examination has been placed prepares and submits his report. The exam- 

 ination is usually made by a journey over the locality by the officer or by an assistant 

 engineer, supplemented by the inspection of existing maps or reports, and by inter- 

 views with those familiar with the condition and characteristics of the stream and its 

 adjacent country. The importance of the proposed improvement as well as its char- 

 acter will govern to a great extent the thoroughness of the examination. The report 

 should contain as many facts concerning the stream as can be obtained: its present 

 condition, its length, tributaries, sectional area, character of bed and banks, obstruc- 

 tions of mill-dams, bridges, etc., amount and period of rainfall, slope and discharge, 

 velocity at various stages, present and prospective commerce, character of surrounding 

 country as to agriculture, minerals, etc., proximity to railroads, and existing facilities 

 for transportation. It should state in general whether the locality is considered worthy 

 of improvement and give reasons for the conclusions. 



If the report is favorable to improvement, additional data may be required before 



an estimate of cost can be submitted, and the cost of making such a survey should be 



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