Road Construction
Before the heavy equipment is engaged and put to work, the road location should be well marked and all preparatory work within the right-of-way should be completed. Marking and preparation will permit immediate and steady use of the machinery and will result in prompt completion at minimum equipment costs. It is important economically that proper size equipment be used.

This section describes the standard road construction phases of clearing, shaping of the roadbed, shaping back slopes, allowing for drainage, and seeding and mulching.

Road Width
It is important to pay close attention to road width during planning and construction. A common mistake is building a road wider than needed for its intended use; it not only adds to the cost of the road, but takes land out of production and renders it useless. Build the narrowest road that will serve your purpose.

If you have problems with wet sections of the road and want the area to dry faster, do not increase the road width. Try improving drainage first (see the section on Road Drainage Methods) or try clearing a larger area so more sunlight can help dry the wet section of road causing problems.

Clearing
Merchantable trees in the right-of-way are cut down and sawn into logs before construction begins. Logs and tops should be moved far enough off the right-of-way that they will not interfere with construction of the road.

Stumps that will be covered by a foot or more of fill material should be cut low but need not be removed. All other stumps and roots over 3 inches in diameter should be dug out of the ground. Leaving a stump about 2 feet high will facilitate its removal with the bulldozer blade. Where the right-of-way supports only brush or young timber, or where a sufficiently heavy tractor-bulldozer is engaged, no felling need be done, and all material can be cleared by machine. Trees moved by bulldozer should not be left leaning or suspended above the ground. They present a hazard that should be eliminated at the time of road construction. Snags that may fall into the road should also be felled. Blasting of rocks and boulders may be necessary on rare occasions, although this need can usually be avoided at the time the road location is planned. Even after construction is under way, it may be possible to bypass such obstacles by minor changes in alignment. If the road has a dead end, sufficient space should be cleared and leveled so equipment can easily turn around.
Road Drainage Methods
This section describes drainage methods that can be used where no intermittent or permanent streams cross the road: water bars, broad-based drainage dips, ditches, outsloping, deflectors, and open top and pole culverts. Depending on the method used, drainage structures would be installed during or after basic construction.

Water Bars
Water bars are narrow structures that may be shallow or deep depending on the need. The deep bars are usually used on roads to be closed to vehicle traffic. Figure 10 shows dimensions for narrow-based water bars. Table 6 shows recommended spacing between water bars.

Water bars can be constructed with hand tools, but bulldozers are most commonly used. It is best to start at the end of the road and work outward so the bars are not damaged by frequent crossing by machinery.
A water bar effectively intercepts surface water and diverts it from the road.
A water bar effectively intercepts surface water and diverts it from the road.
Water bars should be installed at about a 30-degree angle downslope. The outflow end of the water bar should be open to keep water from accumulating and should not flow directly into a stream, to allow the sediment to settle out of the water and to prevent erosion. As a supplement to water bars on roads that will be closed, logging slash can be lopped and scattered on the road, grass can be planted, or both.
Figure 10. Water bars are narrow structures that may be shallow or deep. Deep water bars are usually used on roads that will be closed for extended periods.
Figure 10. Water bars are narrow structures that may be shallow or deep. Deep water bars are usually used on roads that will be closed for extended periods.
Table 6. Distance needed between water bars
Road grade
(percent)
Distance
(feet)
2 250
5 135
10 80
15 60
20 45
25 40
30 35
___________
Source: Kochenderfer 1970, p. 28
Broad-Based Drainage Dips
Broad-based drainage dips, which are easily maintained, do not increase wear on vehicles or reduce hauling speed when properly installed. Because of construction characteristics, these dips should not be used on a road with a grade in excess of 10 percent (Figure 11).

Table 7. Distance needed between water bars
Road grade
(percent)
Distance
(feet)
2 - 4 300 - 200
5 - 7 180 - 160
8 - 10 150 - 140
___________
Source: Kochenderfer 1970, p. 19, 25
Figure 11. Drainage dips are broad structures used on roads with grades of
Figure 11. Drainage dips are broad structures used on roads with grades of 10 percent or less.
As for a water bar, care should be taken to ensure adequate drainage at the outflow of a dip. It should never be designed to discharge directly into a stream. The discharge area should be protected with stone, grass, sod, heavy litter cover, brush, logs, or anything that will reduce the velocity of the water. Natural litter may be adequate in many cases if the terrain is not too steep.

Table 7 presents the spacing of broad based dips as computed with the following formula (Kochenderfer 1970):
equation

Close attention should be paid to construction of broad-based dips, because they are often made too small. Figure 11 shows minimum dimensions. Dips should be armored with crushed rock or gravel.
Figure 12. Water deflectors are installed so that only 3 inches of belting extend above the road surface to turn water aside
Figure 12. Water deflectors are installed so that only 3 inches of belting extend above the road surface to turn water aside. (Original design by Paul Karr, retired, USDA Forest Service)
Ditches
The construction of ditches is usually restricted to roads where there are frequent springs or seeps. The use of ditches requires that a wider road be cleared. A minimum of 3 percent grade is usually recommended to keep water from standing in the ditch. At a minimum, ditches require annual maintenance to provide proper drainage.
Outsloping
Outsloping a road means building the road surface so that it is tilted outward 4-6 percent so water can run off the road surface (Figure 9, Outslope Section).

Outsloping works well under the right conditions. The following conditions are favorable for use of outsloped roads with no ditch:

Short back slopes

Terrain slope less than 20 percent

Road grades steeper than 3 percent

Seasonal road use

Light traffic

Fast revegetation of cut and fill slopes.
A drainage dip is effective in controlling water on the road and does not signifi-
A drainage dip is effective in controlling water on the road and does not significantly slow the speed of vehicles.
A deflector is an alternative method to divert surface water from a road.
A deflector is an alternative method to divert surface water from a road.
Outslopes become a problem if maintenance is not performed when ruts begin to form. The ruts will then act as channels.
The following conditions are unfavorable for outsloping:

Long back slopes


Terrain steeper than 20 percent

Steep continuous road grade

Where ruts occur and allow water to concentrate and run along the road

Where winter hauling is required.
Deflectors
The water deflector is a low cost, low maintenance method to deflect surface water from a roadway, which works as well as an open top culvert. Originally designed by Paul Karr of the USDA Forest Service at Bonners Ferry, Idaho, the water deflector has since been modified by the Engineering Staff of the Lolo National Forest (Figure 12).

The deflector is simply a piece of rubber belting 5/16 inch to ½ inch thick fastened between treated timbers. Figure 12 shows a typical deflector installation. Different widths of belting can be used depending on availability. The timbers are installed in the same way as an open top culvert. The only thing showing above the road surface is 3 inches of belting, which deflects the water from the road surface.
A deflector should be installed with approximately 3 inches of belting above the
A deflector should be installed with approximately 3 inches of belting above the road surface.
The design is simple and works well on low volume and low maintenance roads. The cost for an installed deflector is equivalent to that for an open top culvert. Because there is no abrupt grade change, water deflectors can be used on grades over 10 percent. On roads where farm equipment may have some trouble negotiating broad-based drainage dips, water deflectors would pose no difficulty.

Care is needed when using a road grader to maintain a road with deflectors. Unless the grader operator is careful, the rubber belting can easily be sheared off. This is especially common during winter when the roads are snow covered.
Open Top and Pole Culverts
Open top and pole culverts can be used in place of any of the above-mentioned road drainage methods except outsloping. Open top culverts and pole culverts are inexpensive and easy to construct (Figures 13 and 14). They work well when maintained, but are easily filled with sediment and rendered ineffective within a short period of time when not maintained. Open top and pole culverts are not recommended for crossing live or intermittent streams, and should not be used in lieu of pipe culverts.

Specifications for installation and use of open top and pole culverts follow:
1. Install culverts flush or just below the road surface and angled 10 to 45 degrees downgrade. More maintenance may be required as the angle approaches 10 degrees, 30 to 45 degrees is often times recommended, but this adds length to the culvert.
2. Upper end will be at the same grade as the side ditch and extend into toe of upslope bank.
3. The outlet will extend beyond the road surface with adequate riprap or other material to dissipate water velocity to prevent erosion of fill material.
An open top culvert can be used for road drainage but should not be used for stream crossings.
An open top culvert can be used for road drainage but should not be used for stream crossings.
4. Spacing is the same as for broad-based drainage dips.
5. Use is limited to low water flows and to roads located on flat ground with minimal fill.
6. They are recommended for ongoing operations only and should be removed upon completion of activities.

Shaping Back Slopes
The best time to shape back slopes is during road construction, because it is more expensive to reshape the road profile after it is constructed.

Back slopes can contribute a significant amount of sedimentation until some type of vegetative cover is established. That is why it is important to seed these areas as soon as conditions are right for this type of activity (usually spring or fall). See Seeding for guidelines.
Figure 13. For an open-top culvert to function properly, careful installation and regular maintenance are necessary.
Figure 13. For an open-top culvert to function properly, careful installation and regular maintenance are necessary.
The angle of repose for the slope, which is the natural slope of the material, will be determined by the types of soil in your area. An example would be a 2:1 back slope, which is 2 feet horizontal to 1 foot vertical slope. Successful revegetation will be greater on gentler slopes. There is little benefit in flattening the slopes beyond the angle of repose, which would increase the area exposed to erosion. Figure 15 gives an example of some common proportions of back slopes and describes the type of treatment needed to stabilize them (Hartung and Kress 1977).

If you have a complex stabilization problem requiring the use of terraces or retaining walls, consult a professional engineer.


Figure 14. Pole culverts have installation and maintenance requirements similar to those of open-top culverts. (Redrawn and adapted from Michigan Department of Natural Resources 1997, p. 34)

Figure 14. Pole culverts have installation and maintenance requirements similar to those of open-top culverts. (Redrawn and adapted from Michigan Department of Natural Resources 1997, p. 34)
Seeding and Mulching
Seeding and mulching should be completed as soon as possible to reduce erosion and sedimentation on both cut and fill portions of the road.

Seeding
Seeding is usually accomplished with best results in spring or fall, but results will depend on local weather conditions.

A wide variety of seed is available. Contact your local agronomist, extension agent, county engineer, or the NRCS for a recommended seed mixture for roads in your area. A note of caution: if you have cattle, sheep, or animals that could damage your cut and fill slopes, select a seed mixture less palatable than the surrounding vegetation. Some criteria to look for in selecting a seed mixture are these:

Fast growing or include a fast growing component in the mix
Easy to plant
A compatible mix of perennial and annual seed
Readily available
The success and quickness of establish-ing cover may be enhanced by mulching, depending on climate conditions.
The success and quickness of establishing cover may be enhanced by mulching, depending on climate conditions.
Reasonable cost
Provides sufficient soil protection by establishing a good root system
Unpalatable to livestock or other grazing animals.
Adaptable to soil conditions, for example, drainage, soil depth, aspect, drought tolerance and climate conditions.
Cut and fill slopes should be stabilized, which can be accomplished by reducing them to their natural angle of repose. If not stabilized, slopes will not revegetate and will continue to erode.
Mulching
Straw is the most commonly used mulch material as long as slope gradient, slope length, and rainfall intensity are not excessive. Straw mulch applied at 2 tons per acre is effective in reducing erosion. If weed-free hay is used, seed at a rate of 2 ½ tons per acre. Straw can be used in combination with other bank erosion control measures to increase its effectiveness. Combinations of mulch and netting products are commercially available for areas that are difficult to seed.
Figure 15. The angle of a back slope, shaped during construction, is determined by the natural angle of repose for the soil type. (Redrawn and adapted from Hartung and Kress 1977, p. 11)
Figure 15. The angle of a back slope, shaped during construction, is determined by the natural angle of repose for the soil type. (Redrawn and adapted from Hartung and Kress 1977, p. 11)
horizontal ruler
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