Checking Grade with a Level Instrument
An example of checking ground spots for desired
grade with a level instrument is shown in figure 1551.
The hubs and stakes at the side of the construction
represent offset grade stakes. In figure 1551, view (A),
the grade stake calls for a cut of 7.5 feet. You set up your
level and take two readings: first on the hub and then on
the excavation. Your first reading is 5.0 feet. Since the
excavation is supposed to be 7.5 feet below the hub,
your second reading should be 12.5 (5.0 plus 7.5 as
shown). But the rod reads only 12.2; therefore, you must
cut 0.3 feet more to get to finished subgrade.
In figure 1551, view (B), your first reading is 12.0
feet on the hub. Since the stake calls for F 7.0, you
should read 5.0 on the completed fill. But the rod reads
5.5; therefore, you must fill another 0.5 feet to finish the
subgrade.
MISSING GRADE STAKE.— Another leveling
procedure is to compute a cutorfill requirement from
a missing grade stake. In figure 1552, the finish eleva
tion from the project drawings at point B is supposed to
be 378.75. You setup your level, take a backsight shot
on the bench mark at point A, and get a direct reading
of 11.56 feet. The 11.56 feet backsight reading plus the
bench mark elevation of 365.01 feet gives you an in
strument height of 376.57 feet. Then you take a fore
sight shot at point B, and get a direct reading of 1.42
feet. You now subtract the foresight reading of 1.42 feet
from the instrument height of 376.57, and find that the
existing ground is at elevation 375.15. You now take
the required finish elevation of 378.75 and subtract the
existing elevation of 376.15 and get a FILL requirement
of 3.6 feet at point B. If the existing elevation is greater
than the required finish elevation, you would be re
quired to cut.
Another example of a missing grade stake is shown
in figure 1553. Suppose the stake at station 4 + 50
has been knocked out, and there is no bench mark
Figure 1551.—Checking cut and fill.
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