26 BULLETIN 586, TJ. S. DEPARTMENT OF AGRICULTURE. 
(4) The work on this experiment was delayed because of bad 
weather, but the old road surface was unifornily in fairly good condi- 
tion when the work was done. 
Cost data. 
The bid prices were based on furnishing and placing the materials 
by the material unit and were as follows : 
1. Light coal-tar preparation in place, per gallon $0. 16 
2. Heavier coal-tar preparation in place, per gallon 16 
3. Asphaltic oil in place, per gallon 17 
4. Gravel for top-dressing in place, per cubic yard 1. 05 
At the above unit prices the costs per square yard for the different 
experiments were : 
Cents. 
For experiment No. 1 (cold tar) 9. 18 
For experiment No. 2 (residual asphaltic petroleum) 10. 32 
For experiment No. 3 (2 applications of tar— 1 cold, 1 hot) 15. 26 
Total contract price for the three experiments, $2,149.57. 
During the progress of the work, and with the cooperation of the 
contractor, a record was kept of both the labor employed and mate- 
rials used. Tables 30 and 31 show an itemized summary of the costs 
to the contractor, which are based on the following scale of unit costs: 
Foreman, per hour $0. 50 
Laborers, per hour 25 
Helper on truck distributor, per hour 30 
Driver for truck distributor, per hour 40 
Auto truck for hauling gravel (including driver and supplies), per 
hour 2. 00 
Auto truck distributor (including driver and supples), per hour. . 3. 00 
Boiler for heating asphaltic oil (including fireman and supplies) 
per hour , 1. 00 
Table 30. — Cost data for excavating, screening, and hauling gravel for top-dressing. 
Item. 
Quantity. 
Total cost. 
Unit cost, 
per cubic 
yard. 
Loosening gravel 
Screening gravel 
Loading and dumping gravel. 
Hauling gravel 1 
Stripping pit 
Gravel in pit 
Total. 
Cubic yards. 
271 
271 
271 
271 
271 
271 
$56.50 
53.50 
46.00 
184.00 
4.00 
13.55 
271 
357.55 
$0.2085 
.1974 
.0147 
.05 
1.3192 
i Average haul for gravel, 3,900 feet. The high cost of hauling is due to the use of an auto truck that 
could be kept running but a small portion of the time. 
