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IOWA DEPARTMENT OF AGRICULTURE. 



cold climates, where if water is allowed to remain in the substructure 

 and form a deep frozen crust, the surface is heaved up by frost and des- 

 troyed by the wheels of vehicles on thawing. If the subsoil is kept dry, 

 frost has nothing to act upon, and to this end subdrainage is essential. It 

 is undoubtedly true that many of our worst roads could be improved by 

 subdrains as to yield benefits to their users many times greater in value 

 than the cost of the drains themselves. Subdrainmg earth roads is 

 neither expensive nor difficult, but, like all other kinds of road work, 

 it takes good judgment. 



Hundreds of miles of our roads are located on low level lands and 

 on springy soils, and thousands of miles in the prairie states are for 

 many weeks in the year wet and well-nigh impassable. (Fig. 7.) Such 



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Fig. 7.— Western road that could be made tolerable by drainage. 



roads may be greatly benefited by subdrainage. When wet weather or 

 perennial springs exist in the soil under the road, they should be tapped 

 by blind drains of stone or brick or clay pipe (Fig. 8), leading diagonally 



Fig. 8. — Cross sections showing construction of subdrain. 



to the side ditches. Where sidehill roads are springy, deep open ditches 

 on the higher sides will often suffice, otherwise subdrainage must be 

 resorted to. 



REMEDY FOR FREEZING.— When water is permitted to remain in 

 the foundation of a road through the winter, it freezes, expands and 



