UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 724 i 



i 



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Contribution from the Bureau of Public Roads 

 LOGAN WALLER PAGE, Director 



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Washington, D. C. 



PROFESSIONAL PAPER. 



December 21, 1918 



DRAINAGE METHODS AND FOUNDATIONS FOR 

 COUNTY ROADS. 



By E. W. James, General Inspector, Vernon M. Peirce, Assistant Engineer, and 

 Charles H. ^Moorefieli), Senior Hiyhicay Engineer. 



Primary soils 



Drainage 



Design of surface-drainage gutters. 

 Drop inlets and catch basins 



Page. 

 1 

 3 



18 

 24 



Subdrainage 



Foundations 



Notes on specifications. 



Page. 

 28 

 39 

 76 



The first essential feature of an impr5vecl road is adequate drain- 

 age. It is practically impossible to secure satisfactory results unless 

 this feature be given proper attention. Another prime requirement, 

 wherever a hard-surfaced road is to be constructed, is that a firm and 

 unyielding foundation be provided. The purpose of this bulletin 

 is to supply information concerning the proper methods of draining 

 roadbeds, constructed of various kinds of soil, under different topo- 

 graphic conditions, and also to explain how foundations may be 

 designed to suit the soil conditions, the road surface, and the system 

 of drainage. Since the quality of the soil has such an important 

 influence both on the proper method of drainage and on the proper 

 type of foundation to be employed, it is desirable first to discuss 

 briefly some of the most important characteristics of the different 

 kinds of soils ordinarily encountered in highway construction. 



PRIMARY SOILS. 



The texture and structure are the principal properties of soils that 

 determine the manner in which they should be drained and prepared 

 for road foundations. These are important because of their effect 

 on the permeability and capillarity of soils. For the purpose of this 

 discussion, primary soils may be classified as gravel, sand, and clay; 

 but it should be borne in mind that many of the secondary or mixed 

 soils, because of their more general occurrence in connection with 

 road-building connections, are equally important with these. This is 

 especially true of some of the more clearly defined derivative or sec- 

 ondary soils such as loam, marl, gumbo, harclpan, etc. Where a soil 

 is composed of two different materials, mixed in such proportions 

 that its character is decidedly intermediate, it may be designated 



°— 18— Bull. 724 1 



