52 BULLETIN 72-i, U. S. DEPARTMENT OF AGRICULTURE. 



of care exercised in doing- the rough grading, and to a less extent on 

 the type of road crust or foundation which it is proposed to emplo3^ 

 The character of the soil composing the roadbed also may be an im- 

 portant consideration in estimating the cost of this work, especially 

 if any considerable period of time elapses after the completion of 

 the rough grading before the subgrade is prepared. Some soils re- 

 main loose indefinitely and are easily worked into proper shape, while 

 others may become hard and compact in a very short time after 

 being placed in a roadbed. 



The following examples of road-improvement projects completed 

 under the supervision of the Bureau of Public Roads have been 

 selected to illustrate how the cost of subgra.de preparation varies 

 with the local conditions. 



Example No. 1. — A macadam road in Montgomery County, Md. 

 Area surface, 47,456 square yards. 

 Character of soil, stiff clay. 



Grading done -with steam-shovel outfit and not very carefully finished. 

 Cost of preparing subgrade, 6.8 cents per square yard. 

 AVork done with pick and shovels. 

 Cost includes necessary rolling. 



Example No. 2.- — Several sections of gravel road in Leflore County, Miss. : 

 Aggregate area surfaced, 189,.535 square yards. 

 Character of soil, light loam. 



Grading done with scrapers and fairly well finished. 

 Cost of preparing subgrade, approximately, 1.4 cents per square yard. 

 Work done with road grader and a limited amount of plowing required. 

 Cost includes necessary rolling. 



Example No. 3. — A gravel road in Bexar County, Tex. 

 Area surfaced, 100,000 square yards. 

 Work consisted in scarifying and reshaping an old gravel road, and was 



done by means of a roller with scarifier and road grader. 

 Cost of preparing subgrade, 3.8 cents per square yard. 



Cost includes picking out large stones that were turned up in scarifying, 

 as well as all necessary rollings. 



Example No. 4. — A concrete road in Licking and Muskingimi Counties, Ohio : 

 Length of road, '24 miles ; width of concn-'te surface, 16 feet ; character of 

 soil, stiff clay. The rough grading was done with steam-shovel equipment 

 and scrapers, and the work Avas in progress during 1914 and 1915. During 

 1914 the subgrade was prepared almost immediately after the rough grad- 

 ing was completed, and the average cost of lis preparation was approxi- 

 mately 3 cents pei* .square yard. During 1915 the rough grading was com- 

 pleted several months in advance of the subgrade, and the average cost of 

 preparing the subgr.ide was approximately 7.5 cents pei* S(iuare yard. This 

 large difference in cost is attributable partly to the fact that several wash- 

 ing rains occurred between the time of completing the rough grading and 

 tho time of preparing the subgrade, and the work charged to subgi*ade 

 preparations really included a considerable amount of rough grading made 

 necessary )>y erosion of the roadbed. 



