April 5, 2008
Project Logic: Logging Roads – Useful or a Money Sink?
It’s common for mountain properties to be accessed by one or more logging roads. At first glance,
these roads appear to be found money. Why? Because logging roads offer instant out-of-the
package mountain access without the upfront cost of engineering, road construction, and project
management. Heck, with some minor grading, a skiff of gravel, a lift of asphalt, and a few lot lines,
somebody could develop a project rather quickly. What a deal. Or is it?
Before examining existing logging roads, it’s important to understand what a logging road is. In
some cases, they were intended to be mainline or collector roads. Beginning at the lowest elevation
in a drainage or at the base of a mountain, these roads were built wider than other unimproved
roads, but no wider then necessary. As dirt ribbons carved out of wilderness, logging roads often
served as the only path for those driving into the high country and for those coming out, loaded with
logs, in route to mill locations. As topography increased, became “broken,” or as side drainages
appeared, loggers constructed primary spur or “branch roads” off of these valley mainlines. Then,
from these primary branch roads, secondary and tertiary branch roads were constructed with each
one usually built steeper and narrower than the former. The most primitive logging roads were built
in rugged terrain and at higher elevations where rock and steepness equated to very expensive and
difficult road building. At a certain point determined by land ownership, season of year, and
anticipated duration of work, loggers stopped building roads and instead, used bulldozers and
rubber tired machinery to simply drag, or “skid” logs out of the woods and down to their trucks.
These trails are referred to as skid trails. Timber volume ultimately dictated how much money a
logger invested in his road and on balance, it wasn’t much.
Logging roads were also meant to be temporary and this is where things get sticky. Temporary
means cheap and cheap can mean leaving stumps, topsoil, organics, and logs in road fills. In cut
areas, it’s common to find the same unstructural material in embankments. Naturally, organics
decompose and topsoil holds moisture. Neither is good for road longevity. In addition, loggers
normally did not invest the time, or possess the equipment, needed for proper fill material
compaction. Lifts were usually constructed as fast as the logger could pull the levers on a D6. This
is understandable as individual landowners rarely constructed their roads to any standard.
Compounding the problem is the fact that most logging trucks in the region rarely exceeded 10
wheels. Shorter trucks require shorter turning radiuses, which is one of the reasons why many
logging roads exhibit hairpin turns, severe switchbacks, and abrupt dead ends.
1
Another potential issue with logging roads involves lack of ditches and questionable cross drainage.
Old metal culverts and pipes buried in road fills can hold water or may even be corroded thereby
compromising the pipe’s structural integrity. Another potential problem involves pipe capacity.
Undersized pipes and culverts that cannot pass major storm events are time bombs waiting to go off.
At risk are road washouts, severe erosion, and unintended channel diversions. Needless to say,
logging roads can be a continual source of point-load sedimentation and reduced water quality.
Moreover, locust stringers and scabbed together wooden bridges may be inadequate for supporting
the weight of today’s lowboys and heavy equipment.
Above all, road geometry, as interpreted by loggers, means something entirely different to today’s
regulators. Modern horizontal and vertical curve criteria rarely overlays neat to existing logging
roads. Logging roads are known for unsafe sight distances and poor, if any, intersection layout.
Most of this is fine as logging roads worked well in providing loggers access to timber as well as
acting as transportation systems for getting the wood out. The question for land developers is
whether or not these dendritic road networks can be, or should be, cost-effectively integrated into
new community development.
Though they were never intended for today’s traffic volumes, faster speeds, and heavier loads, some
portions of logging roads may be suited for reuse. The benefits are obvious. Less clearing, minimal
grading, less rock removal, and the possibility of constructing on top of stable and time-tested road
prisms. Interested? Here are some tips on how-to evaluate your existing logging roads for
development:
1. Commission a Civil Engineering firm to centerline survey (as-built) and plot all roads
worthy of consideration. Check the grades, curves, and locations of these roads. Do they
work? Are they safe? Are they permitable or will they hamper sales? Are they a risk for
erosion or landslide? Would a new road system improve or further impact the view shed?
2. Use the same engineering firm to survey, measure, and inspect all existing culverts, bridges,
ditches, and cross pipes. Are they obsolete or are they worth keeping? Is anything
salvageable?
3. Develop multiple lot layout schemes using portions of the logging road network. Do the
roads work to optimize lot size, lot layout, and views or would you be compromising lots in
order to save on road construction cost?
2
4. With an excavator, dig test pits (pothole) all desirable sections of the road on 50 to 100-foot
centers. Be sure to include the services of a Geotechnical Engineer when potholing as the
geotech may call for closer holes if needed. Under the Geotechnical Engineer’s watchful
eye, excavate and log all soil types and note the elevations of rock and water. When
backfilling each hole, require the contractor to tamp all backfill in place and then stake the
location of each test pit. Have the Civil Engineer survey-locate each pit and have these
locations plotted on your base contour plan. Number and match each pit to correlate with the
Geotechnical report.
5. Have the Geotechnical Engineer inspect and log the exposed (surface) soil and rock along
the road. Knowing the geology will help your team later when they develop grading plans,
lay out gravity utilities, and when they specify asphalt, rock, and concrete thicknesses.
6. In some cases, unusable road portions may work as lots. Perform potholing wherever an old
road may end up in a structural condition later.
Through field exploration, you may find that some sections of logging roads are desirable to keep
but may require re-working. On poor fills, one solution is to excavate out the old road and replace it
with clean imported material. More exotic and costly methods of road rehabilitation include treating
the roadbed with lime, kiln dust, and/ or concrete. With these surface treatments, it’s important to
make sure that all below-grade utilities have been installed, tested, and complete. If a road needs
further compaction, provided that the developer has the time, resources, and material available, a
road can be mounded over temporarily with dirt. The idea being that the weight of the piled dirt will
consolidate, or surcharge, the road to a desirable density. Other tricks exist depending on what an
old logging road needs to get it right for land development. However, no process short of wholesale
replacement will correct the presence of organics and topsoil buried deep in a road fill.
The extent that existing logging roads can be used for developing land will change from project to
project. Though many techniques work for stabilizing poor subgrade, they tend to be expensive and
can impact utility installation later. Still, those developers that invest in adequate mapping and
exploration stand a better chance of avoiding the headaches and un-ending cost of road repairs
associated with overlaying good roads over bad.
3