Page 218 - Moving the Earth_ The Workbook of Excavation

DITCHING AND DEWATERING

5.20 THE WORK

Finish Levels. When the digging of a ditch section has been finished, boards may be placed on
edge across the ditch at 10- to 25-foot intervals, and staked or otherwise firmly fastened in undis-
turbed soil, in position such that a tight string may be run over the ditch and adjusted by instru-
ment readings to be parallel with the final grade of the bottom. Extra strips of wood may be nailed
on, or notches cut into original boards, if they are too low or too high. Finishing of the bottom,
and placement of pipe, is governed by measurements down from this string.
Laser. Lasers provide means for very exact control over line and grade in trenching, and in pipe
placement.
Lasers are discussed in Chap. 2.

BACKFILLING

General Methods. Trenches dug for laying of pipes or conduits must be backfilled when the
installation is complete. The dirt taken out is pushed or pulled back in. This job can be handled
by most earthmoving machines, but the bulldozer is the standard tool for the purpose.
If the backfill need not be compacted from the bottom up, it may be pushed into the trench in
the ways shown in Fig. 5.13. The bulldozer operates at right angles to the trench, taking as large
a slice of the pile as it can handle comfortably. Dirt which drifts across the blade is left in
windrows that are pushed in a separate series of passes, with poor efficiency, as in (B). Or the

FIGURE 5.13 Backfilling.