Building Principles: Take Me Home, Country Roads . . . with apologies to the late John Denver

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.

 

Rick Stryker is a professional engineer with Camp Facilities Consulting providing study, design, permitting, and construction consultation services to the camp and conference center community. Camp personnel may contact him at 570-296-2765 or by e-mail at rstryker@ptd.net.

Originally published in the 2003 March/April issue of Camping Magazine.

 

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