278 



ENGINEERING ON THE FARM 



drainage does not give satisfaction, as the ground water is not 

 lowered and the bed of the slough continues to be swampy. 

 For good drainage the water channel must be deep enough 



After University of Minnesota 



Fig. 228. Construction of an open ditch 10 feet deep by means of 



slip scrapers 



in the lowest land, and of sufficient cross section, so that 

 the water will be contained within the channel and not 

 overflow. 



Open ditches. Open ditches are essential for outlet 

 channels, and where it is necessary to reduce the first cost 

 they are used for collecting ditches. The area of land that 

 can be drained by any other than open channels is limited, 

 and their use is necessary for large watersheds. Ditch 

 construction is estimated and priced by the cubic yard. 

 The cost per yard, whether constructed by hand, with 

 teams and scraper (Fig. 228), or by means of a steam 

 dredge (Fig. 229), varies with local conditions and the size 

 of the ditch. The price per cubic yard increases with width 



