554 IOWA DEPARTMENT OF AGRICULTURE 



LEVELING. 



If leveling is done by an engineer tiefore the work begins the fall and 

 depth of the tile at every place in the field can be known. On level land 

 this is necessary so that mains may be laid deep enough to reach all 

 branches that may reach back to low places or ponds in the field. Many 

 ditchers claim that they can tell by the eye how deep to dig and how much 

 fall to give. Surrounding groves, hills and low land confuse the eye. It 

 is better to pay for an engineer than to spoil a drain. Some places have 

 little or no fall while sometimes there is a drop backward into a basin. 

 By leveling the fall may be distributed thoroughout the line and the depth 

 at each stake known before any digging is done. 



THE OUTLET. 



Of course the outlet should be located at the lowest place in the system. 

 The water should flow freely away from the outlet so that the water in 

 the tile will not be held back. Sometimes it is necessary to go some dis- 

 tance below the place chosen for the outlet of the tile and deepen the 

 channel or dig an open ditch back to the outlet. This open ditch should 

 be from three to five times &s wide as deep with sloping sides. If the 

 sides can be set to grass they will not be apt to wash or cave. A watchful 

 care should be exercised and the open ditch kept free from weeds and all 

 other obstructions. The outlet should be protected from caving and tramp- 

 ing of stock. When possible it is well to have the outlet open from a bank 

 and this bank should be held around and above and below the outlet by 

 an abutment of concrete or stones. There should be as few outlets as 

 possible as there will be less to care for. Adjacent land owners can often 

 get good outlets by uniting and laying large tile in the natural channels. 

 In some places outlets can be made by draining into wells that reach to 

 gravel beds or crevices in the rock below. 



THE MAINS. 



xH general the main should follow the lowest part of the system so that 

 the branches will readily drain into it. As the branches seldom if ever 

 all run full at once, but simply gather the water, it is not necessary to 

 make the main as large as the total capacity of all the branches. If the 

 main is too small the branches will bring water faster than the main can 

 carry it on, and it will be crowded full and water will be forced out of the 

 joints and intb the soil where it must run over the surface or wait until 

 the main can take it away. In places where there is danger of washing, 

 it is well to lay the main a little to one side to prevent uncovering the 

 tile by washing. In wide sloughs it is often better to carry the water 

 from the branches through two or more smaller mains laid some distance 

 apart rather than through one line of large tile. This plan permits the 

 use of smaller tile in the mains and the several lines each drain a part of 

 the slough. \:\-\]'B 



