114 ENGINEERING FOR LAND DRAINAGE. 



water from carrying silt into the drains. Small drains, 

 however, should be securely plugged up at the upper 

 end. Drains which in some way have become par- 

 tially obstructed during construction maybe cleaned in 

 this way provided the required quantity of water is at 

 hand at the right time. It is desirable to fill the 

 trenches as soon after the tile are laid as practicable in 

 order to lessen the risk from injury by freshets. 



Filling the Ditches, 



Enough earth should be thrown upon the tile after 

 they have been laid and inspected to secure them in 

 their position. This should be done by a careful work- 

 man, who should see that the earth is thrown around 

 and over the tiles in such a way that they will not be 

 moved by any subsequent filling. This is practically 

 the final inspection of the most permanent and lasting 

 improvement which can be made in a soil. Where the 

 drains are in cultivated land, filling may be completed 

 with a plough drawn by a team on each side of the ditch. 

 The evener used on this plough for this work should be 

 about 1 6 feet long. It is assumed that the excavated 

 earth has been thrown in about equal quantities on each 

 side of the ditch. If the land through which the drains 

 pass is in grass, a V-shaped scraper made for the pur- 

 pose and drawn with the point behind should be used, 

 as this will move the earth without injuring the sod. 

 Care should be taken to place all of the excavated 

 earth in and directly over the ditch. If this is not 

 done, there will be a depression over every line when 

 the loose earth settles firmly in place- The fact that 



