14 BULLETIN 691, U. S. DEPARTMENT OF AGRICULTUEE. 



concrete or well-compacted broken stone or gravel foundation 

 to such depth that it will yield a uniform layer two inches in 

 thickness after thorough rolling. A seal coat of the hot asphalt 

 should then be applied at the rate of 0.4 to 0.6 gallon per square 

 yard and covered with a sufficient amount of stone chips to just 

 absorb the excess bitumen. Roads of this, character may be 

 maintained with oil-surface treatments using the materials and 

 methods given under specifications OC-2 or OH-1. The latter is 

 usually to be preferred. Such maintenance treatments should be 

 applied whenever the wear comes directly upon the wearing course 

 rock. 



