i8 THE IMPROVEMENT OF RIVERS. 



as the depth and width of the proposed channel, is of course influenced by the nature 

 and the amount of commerce, present and prospective, which should be commensurate 

 with the cost. Other considerations would be the dimensions and character of existing 

 works of navigation on other parts of the stream or on its tributaries, or on the stream 

 to which it is a tributary, the supply of water, the nature of the bed and banks, the 

 slope, and action of floods, etc. Unless the survey has been exhaustive only an approx- 

 imate estimate of cost can be arrived at. This should give in detail, as far as practicable, 

 the quantity and cost of the various items forming the several parts of the improve- 

 ment, and may also state the probable cost of maintenance. If the improvement is 

 to be by slackwater, then the number of locks and dams with the dimensions and gen- 

 eral characteristics, as well as probable cost, should be given. Approximate locations 

 may be fixed for the purpose of making the estimate, but the final locations are not 

 generally decided until the time has arrived to prepare for construction, as changes 

 in the river from time to time and the effect of other dams already built should be ascer- 

 tained first, and more careful borings and investigations may point out a better location 

 than would be indicated by the first survey. 



In determining upon what part of a river to begin the improvement, whether at 

 the lower or upper end, or at some intermediate point, the requirements of present and 

 prospective commerce should be considered, and those places forming the worst ob- 

 structions should be first overcome. 



Preparation for the Improvement. After a project has been approved and adopted, 

 and sufficient funds appropriated for carrying it out or for commencing it, the engineer 

 officer in charge of the district usually assigns an assistant engineer to take local charge 

 of the improvement, although sometimes another engineer officer, acting under the 

 immediate orders of the district officer, is placed in local charge. If the work be of minor 

 importance, or if it be simply the removal of obstructions to navigation, it is frequently 

 assigned to a master workman or to a steamboat- or river-man familiar with the re- 

 quirements of the locality. This character of work and the building of small dikes, 

 wing dams, etc., in the smaller streams is difficult to let by contract, and the usual method 

 is to do it by hired labor, working under an overseer. It may require the use of boats, 

 derricks, explosives, and a variety of appliances and tools which the Government will 

 hire, purchase, or construct, as may appear best in each case. 



Plans and Specifications. When the location has been fully decided upon and the 

 various dimensions determined, plans and specifications are prepared, if the work is 

 one of sufficient magnitude to require them. These will comprise complete plans, sec- 

 tions, and elevations of the work to be built, as well as detailed drawings of special parts, 

 and a full description of the work to be done and manner in which it is to be executed. 



When there are insufficient funds to complete the work, or for other reasons, it 

 may be advisable to make a contract for the preparation and delivery of the necessary 

 material, depending on future appropriations for money with which to carry on th 

 building. Later contracts mav V> n r the construction, or different contract 



