By: Steve Bowers, Douglas County Extension Forester
Even under the best of conditions, roads need to be maintained and/or repaired periodically. Roads are unnatural changes to the forest landscape and nature continually works at reestablishing that natural landscape. During adverse weather conditions, roads being used require regular maintenance because damage not immediately repaired can cause serious issues both financially and environmentally.
Remember to inspect roads in the context of how they are going to be utilized. If an old rock or non-durable rocked road is going to be used in the capacity of intermittent, light usage, then the condition of ditch relief structures will take precedence. If the road is to be used for heavy traffic during the wet weather, then surfacing and ditch relief structures are of equal importance to ensure proper water diversion and to minimize any damage to the road surface and sedimentation issues regarding streams and fish habitat.
It may not be readily apparent whether a road is capable of withstanding wet weather hauling. Especially in the case of low-usage roads, roadside vegetation and lack of maintenance may suggest a non-durable rocked surface unable to withstand heavy, wet weather hauling. It is also possible the road has merely lacked a routine maintenance and is fully capable of standing-up to heavy loads under inclement weather conditions.
If there is no history for the road being utilized for a timber harvesting operation during the wet season, one may be uncertain of the ability of the road to withstand heavy traffic and/or wet weather use. In this situation, a cross section of the roadway may be needed to accurately determine whether the road canmeet the performance standards of its intended use with no negative financial or environmental impacts. Note: It is imperative this evaluation be made prior to road usage. Once operations are underway, maintenance and repair costs increase significantly, both in terms of finances and the environment.
Most likely, 10 to 12 inches of clean, durable rock will withstand wet weather hauling. A road with 3 to 4 inches of rock most likely has the capacity of supporting light travel by a pickup, but will be unable to sustain any heavy activity. Note: These are general guidelines. A road constructed on deep, clay soils will require the full complement of rock surfacing. A road constructed on a firmer, natural rock surface may be able to withstand heavy, wet weather hauling with less rock, but don’t count on it.
All roads, regardless of surfacing, deflect under vehicle wheel loads and do not return to their original shape. Regardless of the amount of deflection, this is how ruts develop on the road surface. The road can quickly develop ruts if the subgrade or surface has been improperly constructed, or if the road is being used for a purpose that exceeds the capacity of its intended use.
When wet weather hauling occurs, the road may fail because trucks are too heavy for the surface to support and initiate a concept known as “pumping.” The subgrade becomes saturated and mud is “pumped” towards the surface because the subgrade soil is squashed from the wheel load and migrates through the more-porous rock surfacing. Moisture and soil particles act as a lubricant, destroying the strength of the road.
To avoid pumping, forestland owners must eliminate standing water by keeping ditches in operating condition and keeping the road properly surfaced. If conditions become too adverse, the road may have to be closed until the area dries out. Once pumping occurs, moisture can remain in the road long after the surrounding areas have dried out.
Unfortunately, when a road has deteriorated to the state previously stated, routine maintenance may hide the problem, but the root cause persists. Damage may be hidden when the road surface is reshaped. This can cause serious problems in the future if the material used to smooth the road surface has pumped saturated subgrade soil (mud) into the base or surface layer of the road. Mixing the saturated subgrade base with the surface can cause continual rutting problems because the road has lost its strength. In severe cases, excavation is required and the base and surface rock must be replaced; proving the old axiom an ounce prevention being ($) worth a pound of cure ($$$).