64 BULLETIN 463, U. S. DEPARTMENT OF AGRICULTURE. 



or spongy material which will not compact under the roller * so as to make a 

 firm unyielding subgrade or earth road surface. 



All trees, stumps, and roots within the limits of the improvement 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, except that if 

 they occur in an area to be covered by a fill more than 18 inches in depth they 

 shall be grubbed up or cut off even with the present surface of the ground. 



Embankments shall be formed of good sound earth or stone and carried up 

 full width. The material shall be deposited in layers not more than 1 foot 

 in thickness, and each layer shall be rolled 1 until thoroughly compacted with 

 a roller weighing not less than 10 tons. 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 right of way to complete the embankments, 

 suitable borrow pits from which the contractor 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 em- 

 bankments or shall be deposited where the engineer may direct. Where 

 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 surfac- 

 ing 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. 



All excavated material 2 will be classed as earth and rock. Only rock in 

 place which requires blasting for its removal and bowlders of one-half cubic 

 yard or more in volume will be classed as rock excavation. 



Materials obtained from excavation and used in embankments will be paid 

 for as excavation only, though the contractor is required to shape and trim 

 the embankments properly. Materials obtained from excavation and used for 

 surfacing will be paid for only once and at the price bid for surfacing 

 material. 



Quantities of materials moved in grading will be measured in excavation 

 and the volumes determined by the average end-area method, and no payment 

 will be made for materials excavated outside the slope lines shown on the 

 plans unless the additional excavation is ordered by the engineer. 



The contract prices for excavation shall be compensation in full for all the 

 work which is required to be done under the heading " grading," except that 

 an additional allowance at the rate of 1£ cents per cubic yard per 100 feet 

 will be made for all materials of excavation necessarily hauled more than 500 

 feet. The centers of gravities of cuts and corresponding embankments will 

 be used in determining the length of haul, and if the center of gravity of the 



1 For earth and sand-clay arods the rolling is frequently omitted. 



~ In general it is more satisfactory to classify the materials of excavation and to invite 

 unit-price bids rather than lump-sum bids. However, if unit-price bids are invited it is 

 important that the various quantities be accurately determined in order that the best bid 

 may be selected. If lump-sum bids are desired, omit the following paragraphs. 



