22 BULLETIN 724. I". S. DEPARTMENT OF AGRICULTURE. 
tiallv a sloping shoulder with a raised curb at the outer edge, as in 
figure 6. The first is adapted for use where the road follows the 
natural surface of the ground closely, and there is no especial diffi- 
culty in securing the necessary width for road and gutters. Where 
the road is located in a deep cut. on the other hand, or where for any 
reason it is especially desirable to utilize the gutter as a part of the 
road surface, the second type should be employed. The method of 
construction is practically the same for both types and may be de- 
scribed briefly as follows: 
First, the foundation should consist of broken stone, gravel, or a good quality 
of earth brought to the required shape and thoroughly compacted by rolling or 
tamping, as in the case of cobble gutters. The location and probable demands on 
the strength of the structure determine the expense justifiable in any case. 
Where earth is used as a foundation in cold climates, great care should be 
exercised to see that it is well drained, as otherwise freezing may cause the 
gutter to heave. 
CONCRETE GUTTER 
i ^Z° -Slope for /"•■/' 
m D r __l_— ——. — s T7-?-^7T^ Y ROADWAY 
\-Z-A concrete about 6" thick. 
Foundation of gravel, broken stone, or good quality earth. 
Fig. 6. 
Second, the gutter paving should consist of concrete mixed in the proportions 
1 part of Portland cement to li parts of clean coarse sand and 3 parts of 
crushed stone or gravel that will pass a. li-inch screen and be retained on a 
|-inch mesh screen. If the paving is merely to prevent erosion and will take 
no traffic a 1-2-4 mix may be used. The concrete should be mixed to a rather 
dry consistency so that it will hold its shape in the gutter, and should be thor- 
oughly tamped until all the voids are filled and mortar flushes to the surface. 
The surface then should be brought to a smooth, uniform finish by striking off 
with a template shaped to conform with the cross section of the gutter and 
floating with a wooden float. In the case of the curb gutter, the mortar should 
be worked down into the face of the curb with a spade. 
Fourth, joints extending entirely through the gutter should be constructed at 
intervals of about 20 or 30 feet. The joints may be made conveniently by 
means of bituminous felt strips placed in the gutter during construction. The 
bituminous felt, which should be about i inch thick, is held in place with a 
template until the concrete is against it. 
Fifth, after the gutter is Finished as above described, it should be protected 
from the drying action of the sun and atmosphere for about two weeks. This 
is necessary to prevent the concrete from developing excessive shrinkage, crack- 
ing, and being damaged otherwise from too rapid drying out One of the most 
satisfactory ways of protecting the concrete is to cover it with canvas as soon 
