igo ENGINEERING FOR LAND DRAINAGE. 



fact, patent to every observer of an underdrained road, 

 is enough to prove the necessity of surface drainage, 

 and that is this : That when by any means a rut has 

 been made and puddled by the continual action of the 

 wheels, no water will pass through the soil at those 

 places. The water must be evaporated or the puddle 

 tapped by a surface ditch. The surface of a road must 

 be sufficiently crowning to throw off all water possible, 

 and then underdrains at the side will prevent the bot- 

 torn from becoming saturated and soft. The surface 

 should receive such care at times as is necessary to 

 keep it crowning and to drain water from ruts that are 

 sure to introduce themselves into all earth road sur- 

 faces. A line of tile at each side of the embankment 

 gives the most perfect drainage. Let the lines be so 

 located that teams cannot drive directly over them, for 

 their value for taking surface water depends upon some 

 part of the earth near the drain being left porous and 

 free from the puddling effects of passing teams. 



Deep side trenches are not desirable, though they 

 may serve the purpose of lowering the water level suffi- 

 ciently for road purposes, because they are difficult to 

 keep graded so that the water will all flow from them, 

 and because the mowmg-machine cannot be con- 

 veniently used to keep the grass and weeds trimmed 

 down, which is also a desirable part of road main- 

 tenance* Besides this, these side ditches are used for 

 a winter sleigh road in latitudes where there is snow- 

 fall, and deep ditches are usually narrow and are ill 

 suited for such use. Broad shallow side ditches graded 

 so that storm water may flow away with tile drains at 

 the inner edge to remove subsoil water form the best 



