66 BULLETIN 463, U. S. DEPARTMENT OF AGRICULTURE. 
All mixing shall be classed as extra work and shall be paid for at prices 
bid for force account work. 
The completed surface will be paid for by the cubic yard of surfacing material 
used, measured in excavation. So much of the surfacing material as is neces- 
sarily hauled more than feet will be classed as sand-clay overhaul and paid 
for at the price bid for this item. 
SPECIFICATION FOR SURFACING A ROAD WITH GRAVEL. 
Subgrade. — The subgrade, or that portion of the road upon which the sur- 
facing material is to be laid, shall consist of good sound earth brought to the 
proper elevation, alignment, and cross section, and shall be rolled until firm 
and hard. The rolling shall be done with a roller of the macadam type, 
weighing not less than 10 and not more than 15 tons. Should earth be encoun- 
tered which will not compact by rolling, so as to be firm and hard, it shall be 
removed and replaced with suitable material, and that portion of the subgrade 
shall be again rolled. When the rolling is completed the surface of the sub- 
grade shall conform to the cross section shown on the plans and shall have the 
proper elevation and alignment and shall be so maintained until the surfacing 
material is in place. No surfacing material shall be spread on any portion of 
the road until the subgrade of that portion has been prepared as herein specified. 
Shoulders. — During the preparation of the subgrade, and before any sur- 
facing material is placed thereon, shoulders shall be built of the width shown 
on the cross-section drawings and to a height not less than the edge thickness 
of the first course of gravel before it is compacted. They shad be true in 
alignment and shall have the edges next to the subgrade as nearly vertical 
as the nature of the soil will permit. 1 If intermediate courses are required, the 
shoulders shall be built up to receive each course in the manner described above 
for the first course before the material for that course is spread. Before 
the wearing course is spread, sufficient material shall be added to the shoul- 
ders to bring them up level with the surface of the wearing course before it 
is compacted and so that the shoulder when rolled will have the shape shown 
on the cross-section drawings. No material which contains weeds, sod, roots, 
or other perishable matter and which will not compact under the roller shall 
be placed in the shoulders. The shoulders shall be thoroughly compacted by 
rolling at the time the wearing course is rolled, and when complete shall be 
uniformly firm and unyielding and of the required shape. 
Should the contractor prefer, he may build the shoulders at one operation 
before any surfacing material is placed on the subgrade. but if the shoulders 
are so built they shall be reshaped after each course is rolled and before the 
succeeding course is spread. 
The contract price for shaping the subgrade and shoulders shall be compensa- 
tion in full for all work directed to be done under the headings "Subgrade" 
and " Shoulders." 
Shoulder drains. — Shoulder drains shall be constructed where indicated on 
the plans or directed by the engineer and shall be of such depth and length as 
may be necessary to drain water from the subgrade into the side ditches. 
The ditches for such drains shall be excavated just before the first course of 
1 If the material composing the shoulders should be so loose that a nearly vertical efljre 
can not be obtained, boards may be staked in line to bold the gravel iu place. As soon 
as the first course of gravel has been spread earth should be placed against the boards 
and they should be removed before any rolling is done. The general use of these boards 
is discouraged. 
