DRAINAGE OF JEFFEESON" COUNTY, TEXAS. 21 
PUMPING PLANTS. 
The design of pumping plants for drainage districts involves the 
study of many technical phases of their construction and operation, 
but experience seems to indicate that for the pumping districts herein 
recommended the centrifugal pump driven by steam power is the 
best type. Therefore the cost estimates of the plants are based upon 
this kind of. equipment. Possibly electrical power or internal com- 
bustion engines may be found economical for some of the pumping 
plants. 
^Vftcr computing the maximum rate of run-off from each entire 
district by Frescoln's formula, a proper deduction was made for esti- 
mated storage in the ditches in order to determine the maximum rate 
at which the pumps would be required to handle the water. The 
pump sizes were computed by assuming the velocity through the 
pumps to be 12 feet per second. The engine sizes were determined by 
assuming that the water must be lifted 4 feet in all districts in the 
southern part of the county, 6 feet in district No. 9, 7 feet in district 
No. 7, and 8 feet in district No. 6. In times of excessive high water 
it might be necessary to lift the water to greater heights, but this 
contingency would be met by overloading or speeding up the engines. 
BRroGES, CULVERTS, AND FLUMES. 
A complete plan of drainage must include provision for crossing 
highways, railroads, and irrigation canals, and the cost estimate must 
include the expense for the necessary bridges, culverts, and flumes. 
The sizes of openings and the .types of structures recommended are 
indicated herewith. 
HIGHWAY CROSSINGS. 
Where drainage ditches with 2-foot bottom width are crossed by 
highways, culverts are recommended. Where such a ditch will have 
to carry only about one-fourth its computed capacity, a 36-inch 
corrugated iron pipe 35 feet long with a straight concrete head wall 
at each end will be suitable. Where the required capacity is about 
one-third the computed capacity, a similar culvert of 48-inch pipe is 
recommended. WTiere required capacities are approximately one- 
half, three-fourths, and the whole computed capacities, reinforced 
concrete box culverts with openings 4 by 4 feet, 5 by 5 feet, and 5 by 6 
feet, respectively, should be provided. These box culverts should 
each be 20 feet long, with straight head walls. For ditches with 4-foot 
bottom width, similar culverts 5 by 8 feet with flaring wing walls are 
estimated. 
Steel I-beam bridges with 20-foot widthof roadway are recommended 
for crossing ditches with 6, 8, 10, and 12 foot bottom widths; the 
spans should be 13, 14, 16, and 20 feet, respectively. For crossing 
larger ditches, steel pony truss bridges of the Warren t3rpe, with 
16-foot roadways, seem most suitable. The spans should exceed the 
