. DEAINAGE METHODS FOE COUNTY BOADS. 
27 
instead of the drop inlet and catch basin shown in figures 8 and 9. 
The dimensions shown in the figures are considered minimum for 
good practice, and it may be necessary to increase them where the 
volume of water to be cared for is large. 
The photograph in Plate III shows a cast-iron grating suitable 
for covering either a catch basin of the design shown in figure 9 or 
a drop inlet of similar design. Where these structures are suffi- 
ciently far removed from the traveled way to obviate danger to 
traffic the cover design in figure 8 may be used. The practice of 
B-B 
CONCRETE IT END WALL 
FOR PIPE CULVERTS 
— 10"-* 
2' 
0" -4*- \0"-+ 
^B 
1 
4' 
**" 
i 
-< : 4 
— B 
-0" 
Fig. 10. 
PLAM 
leaving the tops open always is objectionable on account of danger 
to animals, and also because the opening becomes obstructed with 
sticks, leaves, etc. 
COSTS. 
Such structures as are shown in figures 8, 9, and 10 usually may 
be constructed of 1:2:4 concrete at a cost of from $12 to $18 per 
cubic yard, including all form work. The labor cost per cubic 
yard should seldom exceed about $10. 
The cost of suitable cast-iron covers, where standard designs are 
employed, averages about 2\ cents per pound in place. 
