10 BULLETIN" 691, U. S. DEPARTMENT OF AGRICULTURE. 
stone to fill the surface voids when thoroughly rolled. 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. 
