Other Uses of Cement Pipe 157 



The town of Glendale is the first in Arizona to use machine-made 

 cement pipe for sewer lines. (See page 7Z.) The town has voted 

 additional bonds and will enlarge its sewer system, using the same 

 kind of pipe. The city of Globe, also, is to adopt machine-made 

 cement pipe for an extensive sewer system. Other cities in Arizona 

 may well follow the example of Glendale and thereby save the 

 difiference in cost between cement and clay pipe. 



BRIDGES AND CULVERTS 



Pipe culverts are much used for stormwater conduits on public 

 highways, though in Pima and some other counties the substitu- 

 tions of dips (depressions in the grade) is increasing. Where the 

 watershed to be drained is local and the maximum flow can be 

 estimated with some certainty the culverts are advisable, on ac- 

 count of the even grade of the road, the low cost to install, and 

 practically no upkeep. But there are thousands of drainage cross- 

 ings where a usually insignificant channel overflows into a river tor- 

 rent occasionally, usually for an hour or less at a time, and for such 

 places the dip is advisable. Dips should be floored with concrete ; 

 "gravel dips" are a failure, but in a few localities, where the best 

 caliche binder is available, "lime-bound" gravel dips may be justi- 

 fiable. Dips should have thick, heavy, and sloping cutofif walls on 

 the downstream side and thin but deeper walls on the upstream 

 side. The dip is not a suitable type of construction for rivers, since 

 it is impossible to design them to resist undermining at reasonable 

 cost. 



For road culverts a range of sizes from 18 to 30 inches is feasible. 

 Smaller culverts become clogged with floating debris ; larger than 

 30 inches are expensive and with much less capacity than dips or 

 slab bridges. 



The culverts should be sunken so that the thickness of earth 

 covering over the crown is equal to the diameter of the pipe. The 

 backfilling should be done very thoroughly, so that the bottom and 

 sides of the pipes are well supported. End walls of concrete or 

 rubble are necessary to prevent cutting out by the swirl of the water 

 or by the flow creeping along the outside of the pipe. 



Pipe culverts ofifer an ideal substitute for the wooden bridges 

 over irrigating ditches both in the fields and in highways. It often 

 happens that a single ranch owner has from six to twenty such 

 bridges to build and maintain. The pipe culverts are actually less 



