68 BULLETIN 463, TJ. 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. Tbe 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 tbe 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 one-half 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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