68 BULLETIN 463, U. S. DEPARTMENT OF AGRICULTURE. 
the required grade and cross section. It shall be so maintained until the 
second course of gravel has been spread. 
Intermediate courses. — When intermediate courses are required, they shall be 
constructed in a manner exactly similar to that described above for the first 
course. 
Wearing course. — After the first and intermediate courses of gravel have been 
rolled as specified the earth shoulders shall be built up or reshaped to con- 
form with the finished cross section of the road, and the wearing course, con- 
sisting of a single layer of No. 2 gravel, shall be spread uniformly to such a 
depth that when compacted it will have the thickness shown on the cross- 
section drawings. The methods specified for spreading, harrowing, rolling, 
and correcting irregularities and depressions in the first course shall also apply 
to the wearing course, except that the rolling for the latter shall begin on the 
shoulder, at least 2 feet from the edge of the gravel. 
When the gravel surfacing and shoulders have been rolled until thoroughly 
compacted and have been brought to the required cross section the surface 
shall be sprinkled with water from properly constructed sprinkling wagons and 
again rolled according to the method already described. The amount of water 
used shall be sufficient to wet the gravel but shall be put on in such quantity 
and manner as not to wet and soften the subgrade. Sprinkling and rolling 
shall be continued until the surface is thoroughly bonded. 1 
When completed the gravel surface, shoulders, side ditches, and side slopes 
shall be true to the grade and cross section shown on the plans and drawings. 
The contract price per ton for gravel to be used in surfacing shall be full 
compensation for digging, screening, loading, spreading, harrowing, rolling, 
sprinkling, and hauling the gravel onedialf mile or less. Stripping of gravel pits 
will be paid for at the contract price for excavation. The contract price for 
overhaul of gravel will be paid on all gravel hauled a distance greater than 
one-half mile. 
1 If the gravel contains clay of such quality that it causes the surface material to 
adhere to the wheels of the roller, the surface should be sanded with coarse sand. It is 
advisable also to finish the surface of a gravel road, built of gravel containing clay, with 
a coat of sand about one-half inch in thickness, before traffic is allowed upon it. 
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