by Rick Stryker
Getting from here to there on camp property shouldn’t be the biggest
obstacle or most memorable moment for any visitor. But just because there
aren’t any “moving parts,” one shouldn’t assume that there isn’t more
than meets the eye to a good roadway system. The horizontal route, the
steepness, the drainage, and the surface itself all should work together
to provide a safe means of moving about. If your facility doesn’t have
the luxury of rebuilding its roads every year (or even every other year!),
read on and see what you can do to get the most out of your roadway investments.
Layout Geometry
For the most part, camps and conference centers are largely “stuck” with
the route their roads take since they are already in place. In order to
better understand how your roads are serving you, we should look at these
design components. Overall, the physical shape of the roadway path (called
vertical and horizontal alignments) will dictate the sight distance along
the path. Sharp turns and steep hills prevent vehicle operators from seeing
and anticipating roadway obstacles — particularly intermittent ones like
pedestrians or wildlife. This is especially true at night since headlights
only travel in straight lines directly aligned with the vehicle. In short,
if campers and vehicles are expected to share the same routes, the cost
of constructing improved footpaths that establish specific crossing points
is money and time well spent.
Notice the words “constructing” and “improved.” This doesn’t necessarily
mean paved highways, but the paths should be planned, built, and maintained
for foot travel. Their construction should be pursued in much the same
manner and with the same conviction as roadway construction — with a layout,
design, and commitment of money, labor, and equipment — if the finished
paths are to be used as an alternative to walking on the road. No matter
how “back to nature” your campers may be, if the footpath is always sloppy
with mud, uneven, or laden with trip hazards like stumps and rocks, the
road will be the route of preference.
For new site development, or where old roads are being reworked, the
sight distance and operational issues can be reasonably addressed in design
and construction. There are design standards for rural roadways, which
set limits on the steepness and sharpness of curves — and these should
comprise the foundation of the design.
Imagine looking down on the site from above. The road should have as
broad, sweeping curves as the site will allow. The “insides” of each curve
should be cleared to allow headlights to illuminate the road across the
open area to allow the driver and pedestrians time to adjust for each
other. Curves which break one way and then the other in short succession
makes for difficult driving, particularly for trailered vehicles.
Now imagine the roadway as you might see it across the edge of a cliff
or cut away.The profile looks a little like a smooth line graph. Hilltops
(crests) should be broadened to allow the maximum distance for headlights
to light the path. The bottoms of curves (sags) will tend to collect water
runoff. These will flood and deteriorate most rapidly unless adequate
provisions are made to pass the water from the high to the low side of
the roadway.
Drainage
Most rural roadways are best suited to collect water in ditches on each
side. Periodically, the water needs to be passed to the lower side of
the roadway for transfer to a creek, stream, or other water body. There
are a host of questions that come out of this very simple combination
of issues, which include:
- How wide and deep should the ditch be?
- How often is “periodically?”
- How big should the crossing pipe(s) be?
The answers to all of these depend on many factors and are the ones that
are answered in the roadway design process. For most existing facilities,
these are questions which can be answered by experience.After a washout,
there is a tendency to get so focused on the most immediate and pressing
issues of repair that the same mistakes are repeated. Often, a washed
out culvert is replaced with another just like it! If the pipe was too
small to pass this particular amount of water, isn’t it likely to encounter
this same flow again soon?Why not spend the very few extra dollars by
installing the next larger pipe size? It may also make sense to add another
crossing pipe halfway uphill of the one that washed out. Between the two
improvements, this may be sufficient to lessen future floods.
Pipe Material
It’s important to note that there is no “one material fits all” answer.
Each pipe material has benefits and shortcomings — and each should be
considered when choosing pipes for culverts. One point to consider is
that many regulating agencies forbid pipe smaller than fifteen inches
in inside diameter. This provision has come about because of the tendency
of smaller pipes to become clogged with large debris. Even though almost
all of the products discussed will come in sizes much smaller, we do not
recommend using pipes that are smaller than twelve inches under any circumstances.
The most common culvert material that we see is black corrugated pipe.
It is made of a plastic called high-density polyethylene or HDPE. It’s
comparatively inexpensive and light enough to handle without a lot of
specialized equipment. In addition, it is chemically inert to the low
pH associated with acid rain.
We encounter reinforced concrete and corrugated steel pipes equally often.
For a number of reasons, though, we don’t see these products as frequently
as the plastic pipe. If you have these products on site already and are
considering replacing them, the new pipes should have properties similar
to those described below. Both concrete and corrugated metal corrode —
the HDPE pipe does not. In some ways, these materials provide a more forgiving
installation than their HDPE cousins. That is, they tend to be a little
stronger with shallow installations. In addition, the flexibility of HDPE
allows the pipe to be installed without a constant grade (there could
be a sag in the middle), whereas the concrete or metal pipes are more
rigid.
In any case, the pipe you select should have:
- HS-20 load rating. This means that it is structurally capable of
supporting vehicle loads without collapsing or flattening. This rating
will be for specific depths of bury, so you’ll need to know how deep
the pipe will be under the road.
- A smooth interior. Lower quality corrugated pipes have the ripples
or corrugations on the inside as well as the outside. The ripples provide
stiffness to the pipe, but if carried through to the inside of the pipe,
they impede the flow through the pipe. This is one of the drawbacks
to corrugated metal culverts as well.
- Integral joints. Pipes often need to be connected end to end to reach
from one roadside to the other. Some manufacturers make their pipes
to receive special couplings to join them together. For simplicity,
we recommend that the selected pipes have a wide end (the “bell”) that
receives a matching narrow end (the “spigot”).
If the pipe at your local hardware store doesn’t have these properties,
consider asking them to stock it or finding a wholesale supplier and stocking
it on site yourself. The success of your project will be largely dependent
on how closely the installation instructions are followed. Pay particular
attention to the recommendations regarding how the pipe trench is to be
prepared, how the pipe is joined, and the technique for burying the pipe.
Roadway Surfaces
Cement concrete
Although not a widely used surface at camp, there are locations where
Portland cement concrete (PCC) is the best material for a roadway surface.
Specifically, these would be at locations where one expects frequent heavy
truck traffic — like garbage dumpster pads and accesses, pool-supply and
soda-delivery locations, and fueling stops. The weights of these types
of vehicles that make regular visits to camp are extraordinary and should
be considered when planning roadways to, and at, these locations.
The main benefit of concrete is that it is a rigid surface that receives
loads from above and spreads them across the entire structure. For proper
service, it is especially important that the ground on which the concrete
is placed is tightly compacted and well drained. Otherwise, the loads
from above will not be uniformly transmitted to the ground below, and
groundwater and frost will lift the slab. Both will cause the slab to
break. PCC also requires the inclusion of reinforcing to handle certain
internal stresses. How much steel, what kind, and the placement of the
steel are all part of the design.
Bituminous concrete
A more common type of camp roadway surface is bituminous concrete and
is called a variety of things including tar, asphalt, and blacktop. Some
of its benefits include good surface drainage and no dust. All of these
properties are contingent upon proper construction from the ground up
— literally. Because it is a flexible surface, it is particularly sensitive
to the movement and freezing of water beneath. Subsurface drainage and
proper compaction of the native material are critical to the longevity
of the final project.
Consider one of the misnomers for the product, “blacktop.” If a camp
has a soil roadway and decides to “black top” it, that’s what it will
get — a road with a black top. However, without proper drainage and compaction
beneath, the black topping will be stacked on the road edge after the
first winter of plowing. Each granular layer beneath the asphalt concrete
surface should be carefully compacted by power driven equipment until
the rear tires of a fully loaded dump truck do not sink at all into the
surface. Any material that moves under the weight of the truck should
be dug out, replaced, recompacted, and retested.
This sequence will be more expensive than calling the local paving contractor
and getting a blacktop quote, because laying asphalt is quick and easy
with modern equipment. It’s the surface preparation, which is difficult
and time consuming. This is one of those times when there’s no point in
doing it at all if you’re not going to do it right. If the budget won’t
allow you to do the whole project at once, phase it over several seasons
and do what you can afford each year.
This “do-it-right-or-not-at-all” mindset especially applies if you already
have an asphalt surface covered with cracks, the edges are breaking off,
or humps appear during the winter. These are indications of poor under
drainage. Just like a coat of paint won’t cure rot on a building, adding
asphalt (or other “black stuff”) to the surface of the road won’t cure
a failing roadway.
Improved soil
Lastly, there are dirt or “improved soil” surfaces. Surface drainage here
is the key to a lasting roadway. A well-graded, crowned, and compacted
surface can serve many installations well. A properly crowned roadway
will direct water to both ditches equally when dumped on the centerline.
A 4 percent drop from centerline to the top edge of the ditch should provide
sufficient slope to move the water away from the traveled surface. The
dust can be controlled using any number of sprays applied by trucks throughout
the summer. The U.S. Department of Agriculture Forest Service has several
very good publications available on the construction and maintenance of
improved soil roads and dust palliatives. One particularly good guide
is Landowner’s Guide to Building Forest Access Roads, by Richard Wiest,
July 1998. This particular document covers a large portion of the proverbial
“nuts and bolts” you’ll need to construct, maintain, and repair your improved
soil roadways.
The drives in and out of your camp are the first and last things that
your visitors encounter, so from a marketing standpoint, roadway access
to your facility may be your most important site improvement. But there
is certainly a happy medium between a concrete super-highway and a pothole-laden
cart track. Capital cost has to be balanced against maintenance cost and
lifespan of the roadway surface. Ask your engineer what’s available in
your area and which products will best suit your operation.
Originally published in the 2003 March/April
issue of Camping Magazine. |
