DEAIjSTAGE of JEFFBRSOlSr 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 ec[uipment. Possibly electrical power or internal com- 

 bustion engines may be found economical for some of the pumping 

 plants. 



After 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. 



BRroCES, 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 3.5 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. Where 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 bo provided. These box culverts should 

 each be 20 feet long, with straight head walls. For ditches with 4-foot 

 bottom width, siiniliir nilvcrts .^ by 8 feet witli flaring wing walls are 

 estimated. 



Steel I-beam bridges with 20-foot widthof roadway are recommended 

 for crossing ditches witli G, 8, 10, and 12 foot bottom widths; the 

 spaiLS should 1)0 13, 14, 10, and 20 feet, respectively. For crossing 

 larger ditches, steel pony truss bridges of the Warren type, with 

 10-foot roadways, seem most suitnhlc. The spans should exceed the 



