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BULLETIISr 190, U. S. DEPARTMENT OF AGRICULTURE. 



In general, it may be said that the proper" location of a drain 

 depends upon the surface and subsurface topography, the nature of 

 the soil, and the source of the damaging water. Subsurface condi- 

 tions have more to do with the location of drains than does the sur- 



FiG. 4. — Illustrating importance of proper depth of tile: a, Drain ineffective owing to insuflacient depth. 

 The water passes through sand stratum under the tile, which is in dry clay, b, Two ways of making 

 above system effective — by deepening drain 1 foot, or by changing the location so that line wfll cut 

 through previous substratum, the depth remaining the same. 



face topography, but most important of all is the source of the dam- 

 aging water, since in many cases it is necessary to intercept this flow 

 at the point of entrance to the tract. The question of location, 



mter,Bec>rm3^"'^^ 



Drain 5 deet 



J.G.H.,de;. 



Fig. 5.— Section of water-logged tract in which attempt at drainage was unsuccessful owing to insuflacient 

 depth of drain. The trench should have been cut entirely through the water-bearing sand and the tile 

 laid on the underlying clay. 



however, must often be considered in connection with that of required 

 depth. For instance, referring again to figure 4, b, it will readily be 

 seen that a drain located at the change of slope will be fully as 

 effective and more economical than one located on the top of the rise. 



