Farming Magazine - May, 2010
On the Road
The right way to build forest access roads
| One important part of forest road design relates to culvert sizing, which plays a vital role in protecting stream ecology.
Photos Courtesy of University of Maine.
We sometimes hear reports of a “road to nowhere”—some Congressionally funded pork project that constructs a road where it’s not needed or to a location nobody wants to go. A forest road is exactly the opposite of a that. Forest roads, usually nowhere near as grand as a highway, are created only when and where they’re absolutely needed. These roads provide a critical avenue to remove timber during a harvest, as well as provide landowners access to woodlots for recreation and forest management purposes well into the future.
In order to provide long-term service in an environmentally responsible way, forest roads need to be designed and built correctly, says Jeffrey Benjamin, an assistant professor at the University of Maine’s School of Forest Resources who teaches a course on forest road construction. Each year, Benjamin identifies a location on the University of Maine’s forest property, gives students maps of the site and asks them to select the best location to put in a forest road. “If you have a topographic map, you can estimate grades, and we also overlay some drainage classifications based on vegetation and soil surveys, which lets us know which areas are susceptible to being wet, so we can avoid those. You might be able to see on aerial photos where there is a stream or a beaver dam. You also look for property boundaries that need to be avoided,” he explains. “After the students route the road on a map, we go out and actually walk the spot they’ve mapped using a compass, hang ribbon and identify any wet areas or crossings.”
Once they’re physically standing on a site, the students can then make adjustments based on wet areas or streams. “Then, we get into culvert sizing based on the hydrology, best management practices, stream ecology and so on,” Benjamin explains. “We typically see the stream-road interface as ‘the road needs to go here and the stream is in the way,’ but it’s good for students to understand stream ecology to get another perspective,” he adds.
Maine’s “Water Quality Best Management Practices Guidebook” has easy-to-understand instructions about culvert sizing, and students use this resource, says Benjamin. Stream dimensions, the desired length of service—one season or 25 years, etc.—all go into culvert sizing, he explains. “We also use some more scientific ways of calculating flow and then factor in stream ecology to be sure that the culvert isn’t passing water, but blocking fish passing. We combine all of these things together to come up with the solution.”
The forest roads that Benjamin works on with his students are typical of those found in the Northeast. “They’re small access roads—something that a wheeler truck could use for access—but it’s not a big, double-wide main line road with crowning,” he explains. “In most situations in the Northeast, whether for small woodlot owners or even in the industrial forest industry, the forester will typically take a GPS unit, pick off a few points, hang a few ribbons and then hand the map over to the logging contractor. Because they are the ones who will be making decisions on the ground, and with a good logging contractor, that system works.”
Still, Benjamin goes the extra mile to teach students some of the intricacies of forest road design in case they encounter particularly challenging sites or projects in the Northeast, or choose to work in other regions, he says. In British Columbia, for example, forest roads are much more involved, he points out: “Depending on the slopes, there are requirements for engineering designs for roads with huge cut and fills, blasting, end-hauling material away. Those are real roads.”
So, he gives students a taste of some of the engineering that goes in to constructing such a road. “After students have hung ribbons for their road, we literally survey the site with a compass, chain and clinometer and prepare a small topographic survey for the route,” says Benjamin. “We bring that back into the computer and design the alignments horizontally and vertically, and estimate how much material will have to be moved. It’s way beyond what they’ll typically need to do, but I feel it’s important for students to at least see these aspects of forest road construction. There certainly are cases where jobs could benefit for this more detailed work.”
| While not as common in the Northeast as in other parts of the U.S. and Canada, main line forest road design and engineering is covered in the University of Maine’s forestry curriculum. Skills such as surveying, road alignment, materials estimating, turning radius calculations, etc., could prove valuable on certain jobs, explains assistant professor Jeffrey Benjamin.
In fact, he advises all aspiring foresters to learn about his aspect of forest operations: “If you’re working for a forest company and they have you doing cruising all day, ask a couple of times to go with someone doing road layout and volunteer to help out with that—it’s valuable knowledge.”
Loggers also are taught the skills needed for proper forest road construction.
Michael Burns is deputy director of the Empire State Forest Products Association and also works with the New York Logger Training program. He says forest road construction and maintenance are part of the training’s focus on best management practices for water quality. “We give the loggers some of the tools they can use to ensure the longevity of the road. This means the road will continue to provide access to the back of the woodlot, but more importantly it will continue to help to protect water quality,” explains Burns.
Building a forest road the wrong way will create a channel for the water, allowing it to pick up speed, creating erosion and sediment. “I always tell loggers, the goal is to keep the road as a road, and not to go around installing gullies,” says Burns. The most commonly used tool in this pursuit is a water bar, he adds, “and they come in all shapes and sizes, depending on what the landowner’s goals are. If you’re working with someone who doesn’t want to drive up and down the road, and they have a problem with four-wheelers, than you can create a 4-foot-deep tank trap. However, water bars can be just as effective at no more than 6 inches in height and still allow the landowner to drive a pick-up or tractor back into the woods.”
Rather than size, it’s the number, location and angle of water bars that most determines their effectiveness, says Burns. “Mostly, you want water bars to be 45 degrees across the road. Although the term is ‘water bar,’ the goal isn’t to stop the water. It’s to take the water’s momentum and move it off the road and into the undisturbed soil, which is really just a huge sponge to absorb the water into the ground.”
Obviously, it’s important to angle the water bars such that the water is carried off the road on the downhill side. It’s also important to be sure that the area on the downhill side is clear, so the water doesn’t pond up on the side of the road, Burns emphasizes: “Water is always going to go downhill and, like electricity, it’s always going to take the path of least resistance. That is usually the compacted soil on the road, so you have to get the water off.” He says a simple tip for calculating the number of water bars needed is to install them at eye level when walking up the forest road: i.e. stand facing uphill at each previous water bar location and locate the next water bar where eye level meets the slope in front of you.
Burns says water bars are typically made onsite using whatever equipment —skidder blades or dozer—the contractor has available. Sometimes, a 4 or 5-inch-diameter tree is used in the water bar to anchor the dirt around it. There is one other option to consider called a “rubber dam,” a simple device consisting of a conveyor belt material attached between two 2x6s buried in the ground. “When you go over it, it flops over when your tires hit it, but it flops right back up again. It’s easy to make—you just need some lumber and a chunk of old conveyor belt. If you’re going to be using the road for years, it’s a great tool,” says Burns. He advises checking all water bars each spring to ensure they’re still functioning properly.
Burns says that finding a logger who has been through the training and is certified will help ensure that proper water bar installation procedures and other best management practices are followed when forest roads are constructed. “It’s another case where the highest price is not always the best deal,” he says. “I’ve seen cases where contractors have done a horrible job with the roads. They’re left all rutted and the landowner is left without access to their woodlot for years to come.”
Burns says that forest roads are often an overlooked topic of discussion between landowners and logging contractors. He recommends that landowners explain their goals for access on the roads long after the harvest is over. “Certified loggers are fully qualified and capable of building quality forest roads—and some prefer to do it to be sure it’s done right,” he points out. When they’re already onsite with their equipment, it can be a win-win for the landowner and contractor to negotiate construction of access roads that will create benefits for years after the harvest is over. “A lot of times, with a harvest, the landowner is only thinking about the dollars, but landowners have an investment in their property, and they’re paying on that investment every year when the tax bill comes,” says Burns. Investing a little more in the proper installation of forest roads can help landowners get out to enjoy their property more completely.
Patrick White is a freelance writer and editor who is always on the lookout for interesting and unusual stories. Comment or question? Visit www.farmingforumsite.com and join in the discussions.