Laying Out Drains 477 



ning at the outlet, intervals of 50 feet, at each of 

 which a grade peg is set about 12 inches to one side 

 of the center of the ditch, where they will not be 

 disturbed, driving them down flush with the surface 

 of the ground. About 6 inches farther back from 

 the line of the ditch a finder is also set. Sub -mains 

 and laterals are staked off in a similar manner, and 

 when this is done the work of leveling for digging 

 the ditches may begin. 



DETERMINING THE GRADE AND DEPTH OF 

 THE DITCHES 



The determination of the levels of the grade pegs 

 should begin at the outlet of the main, and proceed in 

 the manner already described in leveling the field, enter- 

 ing the figures in a table prepared in the notebook, 

 as shown below : 



Table showing field notes for determining depth of ditch and grade of drain 



Depth of 

 Station Back-sight Fore-sight Difference Elevations Grade line ditch 



600 .... 3.74 .01 11.36 8.44 2.92 





