32 BULLETIN 407, U. S. DEPARTMENT OF AGRICULTURE. 
Table 32. — Unit and total costs. 
Items. 
Unit 
cost. 
Total 
cost. 
Clearing and grubbing, lump sum 
Excavation, 793 cubic yards 
Subdrains, 3,616 feet 4-inch tile 
Scarifying, 5,316 square yards 
Shaping shoulders and subgrade, 4,064 square yards 
Foundation stone, 146,775 tons in place 
Wearing course, penetration method, 6,421 square yards. 
Wearing course, sand-oil grout, 367 square yards 
$0. 4704 
.2145 
.0304 
.0371 
2.196 
.3284 
.3942 
$79. 61 
373.03 
782. 07 
161. 61 
150. 87 
322. 32 
2, 108. 66 
144. 66 
Total 4,122.83 
Sand-Oil Grout (Penetration Method). 
Location: Station 19+00 to station 21+00. 
Area: 366.7 square yards. 
This section includes two experiments in the use of oil asphalt 
mixed with sand for constructing a bituminous macadam surface 
according to the penetration method. The first experiment extends 
from station 19 + 00 to station 19 + 55, and was constructed in a 
manner exactly similar to that described above for the straight pene- 
tration work, except that 50 per cent by volume of sand was used 
with the bituminous material. The second experiment extends 
from station 19 + 55 to station 21+00 and was constructed in a 
similar manner to the preceding, except that only 33 per cent by 
volume of sand was used with the bituminous material. 
A total of 672 gallons of oil asphalt were used in the two experi- 
ments, which is at the rate of about 1.83 gallons per square yard. 
It appears, therefore, that the saving in bituminous material which 
was effected by employing this method is only about 0.2 gallon per 
square yard; and if the cost of heating the sand and mixing the 
oil-sand grout is considered, the cost was greater with this method 
than with the ordinary penetration method by about 2 cents per 
square yard. It is very questionable, therefore, if the experiment 
will prove of value. It will be kept under close observation, however, 
with a view to ascertaining any possible superiority which this section 
may possess over the ordinary penetration sections. 
EXPERIMENTS AT WASHINGTON. D. C. 
BITUMINOUS CONCRETE. 
The bituminous concrete experiments at Washington, D. C, con- 
sisted in the construction of two wing drives leading from the sheet- 
asphalt pavement in front of the main building of the United States 
Department of Agriculture to the sheet-asphalt plaza in the rear, and 
was completed on December 7, 1915. Each of the drives is approxi- 
mately 140 feet long and 18 feet wide. The type of construction was 
bituminous concrete upon a 6-inch foundation of Portland cement 
