Page 202 - Moving the Earth_ The Workbook of Excavation

DITCHING AND DEWATERING

5.4 THE WORK

must be pushed back by the bucket as it is built, and in addition it may be necessary to allow the
spoil to come to the edge. Piling on both sides is usually avoided because of backfilling work. It
does serve to block off the ditch so that people are less likely to walk into it absentmindedly or in
the dark, although it is not adequate barricading.

Topsoil. If topsoil is to be saved and put back on top of the other fill, it may be piled on the
opposite side of the ditch from the deeper digging. If the volume of the spoil is not large, the top-
soil may be placed on the same side as the fill but farther back, so that when a dozer backfills, the
topsoil will be next to the blade and will reach the ditch after the fill.
Topsoil is salvaged during the digging by scraping it off first, and bringing the bucket as near the
shovel as possible on the last bite. The body of the ditch is then dug, with the bucket lifted out short
of its closest position. There should then be a separation between the heap of topsoil and that of fill,
as in Fig. 5.2. When the shovel backs away, it can dig the pile while stripping the next section.

Sod. If sod is to be saved, it should be removed ahead of the shovel. It may be dug by hand, or
cut in strips by a tractor-drawn or self-powered sod cutter. The strips left by it may be sliced in
sections and piled at a safe distance by hand. The sod should be taken out at least 6 inches, and
preferably 1 foot, back from the digging sidelines, to avoid damage.

Guides. Sod removal serves as an excellent and unmistakable indication of the location of the
ditch; otherwise a line of pegs low enough to allow the shovel to walk over them may be used.
The shovel is lined up over the ditch in the same manner as described for basements in the previous
chapter, except that for ditches marked with centerlines, the dead axles should be marked to indi-
cate bucket center, not sides.
If the bottom is to follow ground contour, the bucket stick may be given a paint mark that will
be even with the surface when it is straight down at the proper depth. The distance may also be
marked on a stick to be used for checking.
A bottom gradient that is independent of surface levels is usually set and checked by instrument
from reference points. Anything from a hand level to a laser beam may be used, depending on the
conditions and the accuracy needed.

Side Digging. A hoe should be worked away from the end of the ditch that is blocked. In ditching
from a house to the street, it starts at the house and finishes in the open space of the street. However,
it often happens that a ditch must be dug between two buildings, or under other circumstances
where both ends are blocked.
The simplest method of accomplishing the necessary turnaround is to dig the ditch from one
end, then from the other, having them meet at some spot where the shovel can move off to the
side. The digging of the second section should be stopped while there is still comfortable room to
turn the shovel and get it out, as in Fig. 5.3(A). The shovel is then turned at right angles to the
ditch and walked back into the undug space, with its center pin in the centerline of the ditch, as in
(C). It then digs as closely to its tracks as possible on both sides and backs away, connecting the
ditch sections by digging first on a slant and then at right angles to the trench line.
This method calls for an excavation that is usually two or more ditch-widths with a hydraulic
backhoe. (See Fig. 5.4.) Sometimes such a connection can be made where extra width is needed
for a manhole, pumphouse, or side ditch.
Tractor Mounting. The smaller sorts of hydraulic, mounted on the backs of wheel tractors, are
usually the most economical and efficient hoes for work around buildings.
They have the advantages of light weight and rubber tires, and thus are less likely to damage
lawns and paths than the heavy crawlers, either while working or while getting in and out.
Accidental damage to trees and structures caused by operator mistakes is likely to be small.
Another asset is that their small buckets are usually narrower than those of larger machines.
For the usual pipe or wire, they take out less soil to put back. However, in this respect they are not
nearly as economical as small drag trenchers.