GRADING THE DITCHES FOR TILE. 121 



Will be observed that the only bond or security required 

 of the contractor is the 2$ per cent retained until the 

 completion and acceptance of the work. The only 

 method of securing good work of this kind is to give it 

 thorough supervision and know that it is right before 

 the drain is covered. When a drain has been accepted 

 the liability of the contractor should cease provided the 

 individual line has been finished. The retaining of 25 

 per cent is made for the purpose of securing the cor- 

 rection of any faults in the work which may be discov- 

 ered before the drain is covered. 



GENERAL SPECIFICATIONS FOR THE CON- 

 STRUCTION OF TILE DRAINS. 



The lines for the ditches are indicated on the field by 

 stakes which have been set by the engineer, and the 

 depths and grades given by him shall constitute a part 

 of these specifications. 



Digging the Ditches. — The digging of each ditch 

 must begin at its outlet, or at its junction with another 

 tile drain, and proceed toward its upper end. The 

 ditch must be dug along one side of the line of survey 

 stakes, and about ten inches distant from it, in a 

 straight and neat manner, and the top soil thrown on 

 one side of the ditch and the clay on the other. When 

 a change in the direction of ditch is made, it must be 

 done by means of a neat curve, but in all cases the ditch 

 must be kept near enough to the stakes so that they 

 can be used in grading the bottom. In taking out the 

 last draft, the blade of the spade must not go deeper than 



