DRAINAGE 



having no good clay. Its durability has not been 

 tested, but there is no apparent reason that it 

 should not be a good substitute for clay. 



The Grade. The outlet may fix the grade. 

 If it does not, the main, branches, and laterals 

 should have a fall of 3 inches, or more, to the 

 100 feet. This grade insures against deposits 

 of silt and gives good capacity to the drains. If 

 the outlet demands less fall in the system, the 

 main may be laid on a grade of only a half inch 

 to the 100 feet with satisfactory results. Such 

 a small fall should be accepted only when a lower 

 outlet cannot be secured, and great care should 

 be used in grading the trench and laying the 

 tile. 



Establishing a Grade. If the grades are light, 

 they should be established by use of a telescope 

 level. Most of the cheap levels are a delusion. 

 A stake driven flush with the surface of the ground 

 at the outlet becomes the starting point, and by 

 its side should be driven a witness stake. Every 

 100 feet along the line of the proposed drain and 

 laterals similar stakes should be driven. Their 

 levels should then be taken, and when the fall 

 from the head of the system to the outlet is known, 

 the required cut at each 100-feet station is easily 



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