MEASURING THE GRAVEL. When gravel roads are built by public officials, the gravel is usually measured in place in the pit or in the wagon. The former is the better practice, since it is more definite. When the road is built by contract, the gravel is measured (1) in the wagons, or (2) loose in the road by means of gage boards, or (3) compacted in the road by means of established grades. The first or second method is generally used with surface construction, and the third with trench construction. With the last, it is customary to require that the finished surface shall con form to an established grade, and consequently a considerable -quantity of gravel is liable to be forced into the subgrade,—par ticularly if the earth foundation is made to conform to the grade established for it. The specifications for state-aid roads in New Jersey specify that " the contractor is to place sufficient gravel on the road to allow it to shrink 33 per cent in rolling and settling." * Loose gravel with clay or loam binder will shrink 12 to 15 per cent in rolling, and gravel in which the binder is produced by crushing part of the material will shrink still more—possibly twice as much; the above specifications provide, therefore, for the possibility of forcing 18 to 21 per cent of the gravel into the subgrade.
If it is expected that part of the gravel may be forced into the soil, the subgrade may be left a little higher than the established grade, and then the addition of the stipulated amount of gravel will bring the finished surface to the specified grade. Or, a thin layer of sand on the subgrade will sometimes prevent the gravel from being forced into the soil. For a further discussion of this subject, see § 335.
Cost. The cost of gravel roads varies greatly with the
form of construction, the cost of gravel, the amount of grading and drainage required, the width and thickness of the gravel, etc. An average depth of 1 foot over a width of 13i feet requires half a cubic yard per linear foot of road, or 2,640 cubic yards per mile. The gravel usually costs from 5 to 10 cents per cubic yard in the bank stripped. The cost of loading will vary from 5 to 10 cents per cubic yard, not including the time lost by the team in waiting for a load. Setting gage plank, leveling, etc., may cost from 2 to 10 cents per cubic yard. The cost of hauling varies materially with the time of year (see § 4), and including the time lost in load ing and unloading, will usually be at least 15 cents per cubic yard (about 1i tons) per mile and seldom more than 30 cents—the former when done by farmers in the slack season and the latter when done by teamsters. For a haul of 1 mile the total cost in place is 40 to 50 cents per cubic yard.
Reports from forty-four counties in Indiana show that the total cost of construction of gravel roads in that state varies from $800 to $3,500 per mile; and except in a few counties, the cost varies from $1,000 to $2,500, and is generally from $1,000 to $2,000. The cost varies with the distance about as follows: when the gravel is hauled 1 mile, the total cost of the road is $1,000 per mile; when the haul is 2 miles, $1,250 per mile; when the haul is 3 miles, $1,500 per mile; when the haul is 4 miles, $1,750 per mile; and if 5 miles, *2,000 per mile. Numerous data from Ohio and Illinois seem to show that the above prices are fairly representative.