Show 4 ROAD t- t G DRAINAGE FOR GOOD ROADS Essential Feature of an Improved Highway Highway Another Another Requisite Is Firm Foundation Prepared by the HIe United States Department Department Department Depart Depart- ment of ot Agriculture An essential feature of an Improved rond Is adequate drainage e. e Thorough h drainage Is Sf so necessary that It Is practically Im Impossible o to maintain a satisfactory satIsfactory satisfactory sat sat- rood road unless It be given proper prop prop- er r attention Another prime requirement requirement requirement require require- ment wherever where a hard surface road isto Is Isto Isto to be constructed Is a n firm and unyielding ing Lag foundation As the quality of the soil ioU has an Important influence on the proper method of drainage and the type of foundation to be employed much care and stud study must be devoted to the nature type and character of the soils In the section through which It Is proposed to build a road J The most Important primary soils solIs are classified as gravel sand and nd clay but often many of the secondary or mixed soils because of their more general general gen gen- eral occurrence In connection with road-building road operations are arc equally Important Such t types pes as loam marl gumbo and hardpan are representative tive five of this or order er In the design of a road rond the drainage structures are planned to take care of water under three general conditions rain rain that falls CaBs on a road rond surface or grade rain that falls Calls on contiguous land and flows in accumulated volume volum toward the toad road and ground water from any Immediate source To meet these conditions use Is found for special vial cial structures Including longitudinal side ditches usually parallel or approximately approximately approximately ap ap- ap- ap proximately parallel to the center line Intercepting ditches to accommodate water whose approach so close to th the roadway as the side ditches Is likely to cause Injury lateral ditches or culVerts culverts culverts cul cul- cul- cul verts to conduct accumulated water away from or under the road end and In order to plan Intelligently Intel Intel- a system of drainage for any particular road rond it Is necessary to conar con- con L. L tx 71 Ait ar q 1 f p l Water Drains Readily From This Type of Highway I IsIder Ider sIder not only the local character of the soil soli composing the roadbed but also the topography of the adjacent land tand the amount and rate of rainfall and the availability of material suitable suitable suit sulf- f able ble for use In constructing drains Surface drainage systems for roads consist of side ditches along the road paved gutters which are a development development develop develop- ment of side ditches and replace them open oen Intercepting ditches constructed to prevent water from reaching the I road road and lateral or relief ditches to carry off the water vater which collects In Inthe inthe th the side ditches or In the Intercepting ditches Culverts and drains which are constructed for the purpose of removing storm water from the side ditches or gutters are essentially a apart apart apart part of of the surface drainage s system stem and are not to be confused with sub- sub drains which serve an nn entirely different differ differ- ent purpose Where the grade of a road Is so t steep that the ordinary earth side ditches cannot be maintained satisfactorily satisfactorily at a reasonable cost or where j earth side ditches would be k or appear appear unsightly It Is customary to provide pro paved gutters for removing the surplus water Drop Inlets and catch basins are I Iu used u ed to conduct water from side ditches ditch ditch- es ea or gutters Into underground drains or culverts On country roads they are I used most frequently on side hill bill locations locations loca loca- l where the water collecting In the upper side ditch or gutter can cnn be r re removed I moved from the road at Intervals by bym means m of a culvert across to the lower low- low lower er side Drop Inlets usually are arc sufi sufi- suf f. f dent clent an and catch basins seldom are used In country countr road work except where itis It ItIs ItIs Is especially desirable to 10 prevent the silt and other forel foreign n material carried by the water from getting Into the underground drainage structure |