=7. Excavation= is generally measured by the cubic yard, although, in a
few localities, measurement by the perch is still in use. If the latter
method is adopted, it should be stated just what is meant by a perch,
as this varies considerably in different parts of the country.
Before fixing the price for excavation, it is advisable to investigate
the character of the soil by making boring tests. Where there is rock
to be blasted in making the excavation, a special price should be given
in the estimate. If the ground is wet, rendering pumping necessary,
provision should be made for the cost of the extra labor needed.
The disposition to be made of the excavated material should also be
considered; if it must be hauled a long distance, the cost will be much
greater than if the soil can be _wasted_ near by. To aid in estimating
the actual cost, it is convenient and approximately correct to consider
1 cubic yard of ordinary earth as a load for an ordinary two-horse
wagon.
In making calculations of the amount of material to be removed, care
should be taken to note the existing levels of the ground and those
required by the drawings. The excavation should be figured (and made)
at least 1 foot greater than the size of the foundation, so as to
provide room for setting the masonry, pointing, etc.
Excavation for pipes, drains, etc. should be at least 9 inches wider
than the diameter of the pipe to be laid therein. If the soil in which
the excavation is to be made is of a loose and sandy nature that is
liable to crumble and slide, a slope, say of 3 inches horizontal to 1
foot vertical, should be allowed on both sides of the trenches. If the
latter are of considerable depth, it is sometimes necessary to curb or
shore up the sides, in which case an allowance should be made in the
estimate for the lumber required. If piles are required, they should be
figured at so much per linear foot, driven.