DRAINAGE 



trench. This device is better than running water 

 where grades are slight. 



A drain scoop should be used in bottom of the 

 trench to make a resting place for the tile that will 

 prevent any displacement by the soil when the 

 trench is filled. 



; Depth of Trenches. Underdrains may be 

 placed too deep in close soils for best results. In 

 an early day it was advised that the drains be put 

 down 4 feet deep. We now know that a tight 

 clay soil may give best results from a drain only 

 28 inches deep, or even a little less. In a looser 

 soil 3 feet is a better depth, and in porous swamp 

 lands the drain may well go 4 feet deep, thus per- 

 mitting increase in distance between drains 



Connections. The laterals should enter the 

 branches and mains near the top, so that the water 

 will be drawn out rapidly. The tile should be 

 laid with close joints at the top, so that the water 

 may enter more freely from the sides than the top. 

 No covering other than moist soil is needed unless 

 there is very fine sand, when paper over the joints 

 will serve a good purpose. After some moist 

 soil from the sides of the trench has been tramped 

 upon the tile, the trench may be filled by use of a 

 breaking-plow or winged scraper. 



[245] 



