32 BULLETIN 1408, IT. S. DEPARTMENT OF AGRICULTURE 
entrance, and a fence so located as to prevent the forming of a bar 
in the main channel by the trampling of stock. In very soft ground 
a plank floor will be needed at the lower end of the approach. 
Watering places on underdrains should be provided by the in- 
stallation of a by-pass consisting of a trough situated several feet 
from and parallel to the main line and connected to it at each end 
with Y-branches. A coarse screen must be placed at the lower end 
of the trough, which is located in a sump with sloping sides to per- 
mit access by stock. The earth excavated should be spread entirely 
around the sump so as to exclude surface water. 
TRANSITIONS 
Occasionally it is necessary for an open drain to discharge into a 
pipe line of considerable length. Elaborate structures with warped 
transitions are usually unnecessary. In a general way they should 
resemble the intake structure of a culvert and have ample cut-off 
walls. A sloping screen or trash rack should be provided. The 
joints of the pipe should be cemented for a distance of 20 to 30 feet 
below the structure. 
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