Page 347 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

ROADWAYS 8.9

plus sign. For example, a full station 500 feet from zero is 5 00, and the part or plus station at
545 feet is 5 45. A distance of 3,456.2 feet from zero is station 34 56.2.
If changes in plan should cause the project to be extended to the other side of the zero point,
minus stations would be used. A stake 180 feet beyond zero would be station 1 80.
Location measurements refer to distances on a horizontal plane, unless specified otherwise. As
a result, 100-foot stations will appear to be more than 100 feet apart if measurement is made along
1
steeply sloping ground. On a 1-on-3 slope (33 ⁄ 3 percent grade) the surface distance would be about
105.4 feet. But if the stakes were extended upward or downward, any horizontal line between
them would be 100 feet long.
Centerline stakes are in the middle of a single roadway, and usually in the median of a double
one. They are marked L, C, or /c. They show depth of cut or height of fill needed, and usually
carry information about location of culverts, structures, and other features.

Slope. Slope stakes are set where the outer slopes of the cuts or fills meet the original grade,
usually at 100-foot intervals along the roadway, and also at other points where ground slope
changes or special structures affect the slope. They are always at points of no cut and no fill.
Slope stakes are usually set with a transit or dumpy level and a 100-foot steel tape. They provide
the first markers the work crews need, as they show the outer limits of the area to be cleared.
Each stake should show the cut or fill necessary to make the ground level with the centerline
at that point, and the distance to the centerline. It should also show the steepness of the slope, but
it often does not. If this is the same for the whole job, the grading supervisor can carry the infor-
mation in her or his head.
Slope and other side stakes are usually marked with the station number, the distance from the
centerline, and the direction of the centerline. Direction is indicated by the letter R for right or L for
left. Such directions for plus stations are read looking from the zero stake. In some localities 25-R
means 25 feet right of the centerline, in others that the centerline is 25 feet to the right of the stake.
A slope that is not known can be figured by subtracting one-half the width of the road (includ-
ing a gutter, if there is one) from the distance from slope stake to center, and dividing the remain-
der by the cut or fill measurement.
For example, if the distance from slope stake to center were 28 feet and the half width of the road
were 24 feet, the width of the slope would be 4 feet. If its height were 2 feet, the slope would be 1 on 2.
As a cut deepens or a fill is built, it is usually necessary to check the slope with new stakes. These
may be set from the original with a string or carpenters’ level, a rule, and a plumb bob. (See Fig. 8.6.)
Reference (Offset). Stakes on areas to be cut will be dug away, and those inside fill lines will
be buried. In shallow cuts, stakes can be left temporarily in islands; and in shallow fills, long
stakes may be used which will project from the top unless they are knocked over. Slope stakes are
liable to be undercut or buried. Any stakes are apt to be moved by accidents, particularly if the
ground is stony or frozen.
It is therefore desirable to set reference stakes well outside the work lines to simplify resetting
of the work stakes.
Such stakes may be set on one side or on both sides. They are marked with the station and the
distance from the centerline, and may be identified by lettering such as OFF or REF.
If the road strip is narrow or of moderate length, reference stakes on both sides will permit
replacement of the working stakes simply by measuring between the offsets.
Where trees or heavy rocks are near the road, nails may be driven into trees, or marks chiseled
on rocks, on opposite sides of the road, and a tape stretched between them. The reading at the cen-
terline and ends and the station are noted. With these notes it should be possible to find the cen-
ter again quickly and accurately.
When a few centerline points can be found from side references, it is often possible to sight in
the rest of the missing stakes by eye with reasonable accuracy.
Grades may be marked on offset stakes, or a separate system of benchmarks may be used.
Surveyors often set a line of offset stakes instead of a centerline, leaving the center and other
stakes to the contractor’s crew.