Land and Watershed Management - Practices of Irrigation and On-farm Water Management - page 208

work is completed and before final land leveling. Leaving undisturbed temporary
and permanent buffer zones (i.e., vegetated buffer strips) in the grading operation
may provide an effective and low-cost erosion-control measure that will help reduce
runoff velocity and volume and off-site sedimentation.
Finish work with a land plane so that the field is free from depressions that would
cause ponding of water. The land plane should be operated over the field three times:
once at a 45 ◦ angle to the direction of the rows; once at a right angle to the direction
of the rows; and finally in the direction of the rows. Field checking to determine
compliance with design grades should have a maximum tolerance of

±

3.0 cm at
any grid point, with no reverse grade. Instruments (scrapers) are now available for
heavy excavation and GPS/Laser controlled cut and fill work. Finishing scrapers
should be used to level land, precision finishing, and land-forming work.

6.4.5.4 Maintenance Considerations

During the first year after grading, normally cut areas swell and fill areas settle. This
may require minor cuts-and-fills and additional land leveling.
All graded areas and supporting erosion and sediment control practices should
be periodically checked, especially after heavy rainfalls. All sediment should be
removed from diversions or other storm water conveyances promptly. If washouts
or breaks occur, they should be repaired immediately. Prompt maintenance of small-
scale eroded areas is essential to prevent these areas from becoming significant
gullies.

6.4.5.5 Earth Work Volume Estimation

The accuracy of the earthwork quantities estimated is directly related to the com-
pleteness of the surveying work performed. Excavation and fill materials required
for or obtained from such structures as ditches shall be planned as a part of the
overall leveling job.
“Cut-Fill” or “Volumetrics” is the calculation or analysis of landform volumes.
A “Cut” volume is defined as the volume of material, which is excavated below
existing site levels (Fig. 6.1 ) . “Fill” volume is the volume of material, which is
mounded above existing site levels. Negative volume values indicate areas that have
to be filled, positive volume values indicate regions that have to be cut.
Before volumes can be calculated, the areas of excavation (either horizontal or
vertical) must be established. Horizontal areas are associated with cross-sections cut

Proposed
land level

Cut

Fill

Fig. 6.1 Schematic of
showing cut and fill on a site

Existing land
surface