Exhibit 1
Field Location Techniques
Work Item or
Condition Techniques
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1. Overall - Locate road using gradeline control
location with Abney or clinometer when cross
slopes are greater than 15 percent.
- Locate road using horizontal control
with hand compass when cross slopes
are less than or equal to 15 percent
or in rolling hummocky ground with no
specific side slope.
- Fit road to the topography, minimizing
landform modifications.
- Run lines from specific control points
to general points.
- Tie into previously selected control
points using an altimeter. Check
against profiles and maps.
- Exhaust other feasible alignment options
before locating road on exposed slopes.
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2. Running - The final design line will often be
steeper than the gradeline located line.
The shorter the "shots" and the more broken
the terrain, the greater the deviation.
This deviation is the least evident where
the located line is essentially the final
design line.
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Located Grade Design Grade
2-4% Approx. 1/2% steeper
5-10% Approx. 1% steeper
10-14% Approx. 2% steeper
- Grades should be slackened in broken terrain
to allow sufficient design flexibility.
- Flatten grade at potential drainage dip
locations.
- Grades of 0-2% should be avoided where
possible.
- Where the algebraic difference in grades
exceeds 5 percent, transition grade changes in
increments of 5 percent or less. Separate
incremental transition by 25' to 50'.
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3. Log landings - Tractor landings should be located in
and logging areas with gentle back slopes and low
systems cut banks.
- Provide opportunities for off-road landing
access.
- Roads leaving landings should be located
with a grade of 0-5 percent for approximately
150'.
- For road segments with, or to be used as,
continuous landings, grades of 6 percent or
less are preferred.
- To the extent possible, locate roads on
topographic breaks to fit logging system
needs.
Work Item or
Condition Techniques
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- Coordinate landing locations withturnout
opportunities.
- Reduce or minimize visual impacts by
avoiding noses of ridges for landings, if
possible.
4. Switchbacks - Locations should be limited to areas with
side slopes of 35 percent or less.
- Locate switchbacks to minimize visual
impacts using vegetation or topography to
screen impacts.
- Mark approach grades and grades within
switchbacks in accordance with design
standards (4.32).
- Design grades will be steeper than located
grades on switchbacks.
- Lay out short radius switchbacks as circular
curves using radius point and cloth tape or by
deflection angle (2.33).
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5. Intersections - Locations should be limited to areas
with side slopes of 25 percent or less.
- Intersection angles should not be less than
60 degrees (4.33).
- Grade of through road at intersections
should not exceed 4 percent.
- Grade of approach road should not exceed 6
percent (4.33).
- Grade of both roads should be the same until
adequate horizontal separation is achieved.
Work Item or
Condition Techniques
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6. Horizontal - Approximate curve locations by establishing
curves a series of points on curves (POCs). Incre-
mental deflection angles should be less than
45 degrees.
- Lay out short radius curve as circular
curves using a radius point and cloth tape or
by deflection angle (2.33).
- Low standard roads may not require layout of
circular curves.
- Lay out curves so that sharp crest vertical
curves do not coincide with horizontal curves.
- Lay out alignment along natural curvature of
terrain to minimize cuts and fills and to
provide self-balanced sections.
- Check curves to see that they are smooth
and without sharp breaks. Check local
topography to be sure necessary curve widening
and turnouts can be accommodated.
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7. Ridges (sharp - Avoid abrupt vertical curves at ridge points.
and narrow)
- Lay out short radius curves as circular
curves using a radius point and cloth tape or
by deflection angles.
- Reduce grade to provide sufficient design
flexibility.
Work Item or
Condition Techniques
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8. Drainages - Avoid paralleling for prolonged length.
and draws
- Avoid locations that will result in filling
of natural stream channel.
- Avoid sag curves over drainages. Locate
vertical points of intersection (VPIs) in
vicinity of transition between cuts and fills
(4.32).
- Where possible, slacken the location grade
to 0-1 percent approximately 100'-200' before
crossing draw and extend 100'-200' beyond draw
or reduce favorable grades by 5 percent,
adverse grades by 2 percent (reduces the need
for shifting or braking on curves).
- Where possible, cross at right angle and
from top of bank to top of bank. Avoid
cutting down banks, if possible.
9. Surface - Drainage dips should not be located on
drainage desing grades over 10 percent (4.43).
- If surface drainage is to be controlled by
rolling grades, incorporate grade breaks in
the road location.
- Avoid locating cross drainage on curves and
at turnouts.
10. Full bench - The marked grade line will be above the
anticipated design grade line and shifted into
the side hill 1/2 road width compared to self-
balanced areas. Provide for transitions into
and out of full bench sections.
Work Item or
Condition Techniques
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11. Instrument - Check Abneys, clinometers, and checks
compasses daily. Check other supporting
equipment and materials frequently.
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12. Bridge sites - Desirable features:
o Naturally confined stream
o Good approach alignment
o No grade changes or curves on bridge
o Solid foundations for abutments
o Straight stream course
o Crossing is perpendicular to the stream
o Bridge not located at grade sag.
o Bridge is significant cost item.
Location of economical crossing
may controllocation of approaches.
o See FSH 7709.56b, Drainage Structures
Handbook.
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13. Road - Locate intersections to facilitate
closures effective road closures where required.
- Locate closure points in vicinity of areas
suitable for turnarounds.
- Locate closure points that tie into natural
barriers.
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14. Scenic - Where specified in design criteria and road
vistas management objectives, identify off-road parking
areas in the vicinity of scenic features.
- Provide safe sight distance for vehicles entering
or leaving identified parking areas.
2.33 - Field Location Techniques for Special Situations. In some
areas it is necessary to mark the field location of sharp radius
curves through switchbacks, draws, and ridges as a circular curve
regardless of the actual design method that will be used.
1. Marking Curves by Deflection Angle. Vegetation,
topography, or other factors may preclude locating a curve by
using a tape held at the radius point and marking the arc of the
curve. In these cases, marking the curve by deflection angle and
chord can be effective, as shown in exhibit 1.
2. Switchbacks. Switchbacks can be located in the following
manner (and as illustrated in exhibit 2) unless the radius is
relatively large. (For switchbacks with a radius greater than
100 feet, consider using the deflection angle method.)
a. Step 1. Extend the upper and lower gradelines of the
approaching alignment until they intersect.
b. Step 2. Shift the intersecting point uphill. The
steeper the side slope, the greater the shift. This
becomes the radius point of the curve. The shift results
in better balance of earthwork.
c. Step 3. Mark the curve by measuring radially from
the radius point.
d. Step 4. Connect the point of curvature (PC) and
point of tangent (PT) of the curve to the upper and lower
gradelines with a horizontal line that follows the
natural ground contour.
3. Locating and Carrying a Grade Through a Narrow Ridge. A
road can be located to cross through a narrow ridge by using the
procedures described below and illustrated in exhibit 3.
a. Step 1. Select a location for crossing the ridge.
Extend the approaching gradeline to the beginning of the
curve (Point A).
b. Step 2. Using the radius point or deflection angle
methods, establish the horizontal alignment through the
selected ridge point. The midpoint on the curve (Point
B) will lie approximately at the crest of the ridge.
c. Step 3. Starting at Point A, use an Abney or
clinometer to mark equal vertical step(s) up the ridge on
the approach side, and down the ridge on the other side
at the desired grade (G), while following the horizontal
alignment. The number of steps up must equal the number
of steps down. The grade setting on the survey
instrument must be reversed before stepping down.
d. Step 4. Where the topography will permit proceeding
on grade with a smaller deflection angle than is required
by following the horizontal curve (Point C), continue
running a gradeline along the ridge.