DEAINAGE METHODS FOR COUNTY ROADS. 83 



All trees, stumps, and roots within the limit of the iniiprovement shall be 

 grubbed up so that no part of them shall be within 6 inches of the surface 

 of the ground or within 18 inches of the surface of the subgrade. 



Embankments shall be formed of good, sound earth and carried up full width. 

 The earth shall be deposited in layers not more than 1 foot in thickness, and 

 each layer shall be rolled or otherwise suitably compacted by distributing 

 traffic uniformly over the sui'face until thoroughly compacted. 



All existing slopes and surfaces of embankments shall be plowed or scarified 

 where additional fill is to be made, in order that the old and new material 

 may bond together. When sufficient material is not available within the fence 

 lines to complete the embankments, suitable borrow pits, from which the con- 

 tractor must obtain the necessary material, will be designated by the engineer. 

 If there is more material taken from the cuts than is required to construct the 

 embankments as shown on the plans, the excess material shall be used in 

 uniformly widening the embankments or shall be deposited where the engi- 

 neer may direct. Wherever embankments are formed of stone the material 

 shall be carefully placed, so that all large stones shall be well distributed and 

 the interstices shall be completely filled with smaller stone, earth, sand, or 

 gravel, so as to form a solid embankment. 



During the work of grading, the sides of the road shall be kept lower than 

 the center and the surface maintained in condition for adequate drainage. 



The grading of any portion of the road shall be complete before any sur- 

 facing material is placed on that portion ; and where the plans do not call for 

 any substantial change in the grade of any existing section of the road the 

 surface shall be completely scarified to a depth of 3 inches or more before the 

 subgrade is prepared. 



SUBGRADE. 



The subgrade, or that portion of the road upon which the roadway is to be 

 constructed shall consist of good, sound earth brought to the proper elevation, 

 alinement, and cross section, and shall be rolled until firm and hard. The 

 rolling shall be done with a power roller, weighing not less than 10 tons and 

 not more than 15 tons. Should earth be encountered which will not compact by 

 rolling, so as to be firm and hard, it shall be removed and suitable material 

 put in its place, and that portion of the subgrade shall be again rolled. When 

 the rolling is completed the surface of the subgrade shall conform to the cross 

 section shown on the plans, and shall have the proper elevation and aline- 

 ment, and shall be so maintained until it is covered by the foundation or road 

 crust. 



CRUSHED-STONE FOUNDATION. 



Where a crushed-stone foundation is called for on the plans it shall be con- 

 structed after the curbs are set and in two courses of such thickness that the 

 finished foundation will have the required depth shown on the plans. 



The first course of stone shall consist of a single layer of No. 1 stone spread 

 uniformly to a depth of not more than 6 inches before compacting. The stone 

 shall be spread by hand from dumping boards or from dump wagons of a type 

 that will distribute each load of stone evenly over that part of the subgrade to 

 be covered by the load. 



After the crushed stone of the first course has been spread to the required 

 depth, it shall be rolled until it is thoroughly compacted and firm with a three- 

 wheeled power roller weighing not less than 10 tons and not more than 15 tons. 

 The rolling shall begin at the curbs and progress gradually toward the crown. 

 All irregulai'ities and depressions that may develop shall be immediately cor- 



