EARTH, SAND-CLAY, AND GRAVEL ROADS. 15 
approximately smooth slope, as is done in earth cuts. In excavating 
solid rock only such material is moved as is actually necessary to 
obtain the desired width at the bottom of the cut or as has been 
loosened in blasting. The faces should, of course, be cleared of all 
material which is loose, or which might be loosened subsequently by 
frost and slide down upon the road. Stone embankments will stand 
on a slope of about 1 to 1. 
In order to prevent damage by washing all earth slopes in either 
excavation or embankment should be protected by a growth of grass 
as soon as practicable after they are formed. 
In many localities where the soil is fertile and a good quality of 
grass is native no seeding of the slopes is necessary. In other cases 
the soil may not possess sufficient fertility to grow grass, even when 
the slopes are seeded, and in which event it may be very desirable to 
cover the slopes with cut sod. This latter process usually is very 
expensive, and should be employed only where it is known that 
thorough seeding and fertilizing would fail to secure a covering 
of sod. 
Another precaution frequently necessary in order to prevent the 
washing away of excavation slopes is to intercept water from the 
CROSS SECTION SHOWING BERM DITCH BUILT ABOVE SLOPE 
Dimensions of the ditch are determined by the amount of water to be carried 
C is generally 18 to 24 and "G" about 12". 
Fig. 10. 
natural ground surface which otherwise would flow down over the 
excavation slope. This is done by means of a " berm " ditch con- 
structed well back from the top of the slope. Figure 10 illustrates 
a condition which makes a "berm" ditch desirable and also shows 
how such a ditch is constructed. 
EARTH ROADS. 1 
Roads constructed by grading the natural soil to the required 
shape, grade, and alignment, without special surfacing of any kind, 
are designated as earth, or dirt, roads. The efficiency of such roads 
1 This section has been read and revised by P. St. J. Wilson, chief engineer, and T. War- 
ren Allen, general inspector, U. S. Office of Public Roads and Rural Engineering. 
