Forest Road Engineering Guidebook - Ministry of Forests

Forest Road Engineering Guidebook
70
Scattering
be used to raise the subgrade above the normal groundline. Trenching should
not be used on natural slopes with greater than 20% gradient, as it could
undermine the road surface, causing long-term subgrade instability.
Mounding or windrowing
With this technique, all slash and debris are accumulated along one side of
the cleared width between the road prism and the standing timber. The
woody debris is placed first and compacted by the grubbing equipment.
Stripping material from the road prism is used to cover the slash with additional
mineral soil, used as required to ensure that a minimum of 300 mm of
soil cover is achieved. Because of the difficulty of maintaining an adequate
soil cover on the downslope side, the results of this method on natural slopes
with greater than 50% gradient are not easy to control.
Pushouts
Pushouts should be located in natural openings along the cleared area and
should be appropriate for the volume of material to be disposed of. Debris
should not be pushed into standing timber, and the piles should be properly
groomed to be stable and visually acceptable.
This process is similar to mounding and windrowing, but does not require
the slash to be buried (Figure 14). In low-density stands, debris may be
spread among the standing timber in natural openings along the cleared area,
thus reducing the clearing width required for disposal. Care must be taken to
avoid damaging the standing timber.
Scattering should be considered where:
• sidecasting slash and debris will not increase the likelihood of landslides
• fire and pest hazards are low and aesthetic concerns are not an issue.
Incidental burying may occur, but is not an objective. The material may be
bunched or spread, but any continuous accumulations should be breached to
accommodate drainage, snow removal, and wildlife passage.
Slash and debris can also be chipped, or ground up, and blown along the
cleared area or into the standing timber, away from watercourses. In addition,
chipping may limit erosion of exposed soils and facilitate revegetation.