 take us to many great places. Sometimes our favorite places are way up or way down from where we begin our trip. Long before we started building trails, animals had figured out that it's easier to climb up across a side slope than to climb straight up the hill. Eventually though you have to reverse direction and you can do that with a climbing turn or a switchback. Beautiful view isn't it? This is the River Trail on the Lolo National Forest in Montana. I'm Liz Gepton a trail designer and planner for the Lolo. We're going to present a video on switchbacks, how to build them, how to lay them out, how to maintain them and let's go look at a switchback. I want to start out by talking about climbing turns, a related but easier technique for gaining elevation on more gentle hillside slopes. Climbing turns result in a reversal in direction across a hillside. This is also the basic definition for a switchback. The difference between the two is that the climbing turn follows the contour of the slope. As it curves around to head back in the opposite direction, the gradient of the trail is the same as the prevailing hillside. A switchback is different. It has a constructed platform that is not as steep as the hillside and normally not as steep as the grade of the trail. Bicyclists, motorcyclists and ATV riders often prefer climbing turns to switchbacks because the turns are more gradual and easier to make. Horseback riders also prefer climbing turns but really it comes down to how steep the hillside is compared with the allowable grade of the trail. Like climbing turns, switchbacks also allow you to gain elevation in a limited distance and change directions on a hillside trail. Switchbacks differ from climbing turns because they allow you to make these turns on steep slopes without making the trail too steep. The grade through a well-designed switchback is not as steep as the rest of the trail. We only have enough time to show you the very basics of switchback planning and design. Most of the program is going to focus on the steps that we went through to lay out and build a site-specific switchback, assuming that the larger planning decisions were already made. But you still need to know some of the basics of planning and design. I can't emphasize enough how strongly I rely on the standard specs and drawings. Whether you do the work yourself or contract it out, you can get high quality and consistent trail work if you follow the standard specifications. You also should be familiar with the Forest Service Trail Management Handbook. It gives you guidelines for building trails for specific user groups. Switchbacks are among the most expensive trail investments you can make. So look for places where you can build climbing turns instead. As a general rule, the fewer switchbacks you have to construct the better. Vary the length between switchbacks. Uniform switchbacks stacked up a hillside are monotonous. They also require more control of the drainage between them. Try to fit your trail to the mountain. And as long as you can continue to cane elevation, keep the legs between switchbacks longer rather than shorter. No matter how great your trail is, people aren't going to use it unless it meets their needs. No amount of signing or barricading is going to stop them from shortcutting your switchback. You really have to get into the mind of the user. Let's look at how switchbacks differ for various trail users. We'll start with turning radius. Turning radius is an important and useful concept you'll need to understand. Think of a turning radius in terms of drawing a pencil line with a compass like you did in grade school. The point of the compass or the middle of the circle is considered the pivot point. The turning radius is the distance from that pivot point to the center line of the trail as it circles around and changes direction usually in about a half circle. Hikers don't really need a turning radius. They can walk up zig-zagging stairs and climb as steep as the trail tread stability will allow. Normally a switchback turning radius of 2 to 4 feet and a trail grade of not more than 15% allows hikers to move at a steady pace. The approaches to each switchback must not level off or hikers will take shortcuts. Pack stock can turn a switch back with a 4-foot radius but 6 foot is much better. Individual horses not on a pack string need at least a 3-foot turning radius. Easy mountain bike trail should be built with climbing turns rather than switchbacks and have grades less than 10%. Where switchbacks are necessary the turning radius should be 6 feet. Hikers may skid through tight turns creating ruts that cause drainage problems. Motor bikes need a turning radius of 6 feet. ATVs need 8 feet. The trail grade will depend on what type of soil you have and what level of damage is acceptable. Sometimes you might need special concrete blocks or other hardeners to reinforce the tread around OHV trail switchbacks. Other special design factors for motorized trails include banked or super elevated climbing turns and switchbacks for better control and safety. Another important concept is in sloping and out sloping. The special super elevated turns I just mentioned are in sloped toward the pivot point of the switchback throughout the turn. The in slope causes water to channel down the inside of the switchback and must be diverted. By contrast most hiking and horse trails call for the trail surface to slope downward away from the pivot point throughout the turn. This allows for better drainage. We're on the problem section of the river trail and the trail here has some pitches of 50 to 60% grade in it that runs on up for a couple hundred yards here and that steep of grade has caused significant problems for our users. Lost a horse right in this area had to put it down and hikers have gone off and bikers so we need to fix this problem and how do we do that? We put it up on the hillside, lessen the grade and put a switchback in so that we can come back to the main trail. So let's go do that. I can't emphasize enough how important it is to take the time to go back and forth several times across the slope as you try to decide the best location for constructing your switchback. Picking the right spot will make a tremendous amount of difference in the amount of work you'll have to do. You need to know your soil characteristics, how much rock, how subject it is to erosion. Is water seepage a problem? Sometimes vegetation can give you clues. On our site the soils are gravelly and we don't have a lot of rainfall so drainage isn't a major concern. We do have a lot of rock outcrops and some are very solid. This makes construction difficult and time consuming. My crew and I have spent quite a few hours up here looking for alternatives on this relocation without having to build switchbacks. They're really no better places so we have to build it here. And the reason that we picked this particular spot out of this whole hillside is there's a little bit of a break in the terrain. We have a few rock outcrops. We have a little bit of a drop-off right here. That's from a rock cliff. And still this has a little bit of a change in the steepness of the side hill. And the pivot point is going to be the center of this turn for the switchback. You establish that from determining where the lower leg can go and where the upper leg needs to be. And right now we'll look at a five-foot radius turn here plus half of a two-foot tread. I'll give him a distance of six feet. That will be the outside edge of the trail. Now keep in mind that on a switchback you are going to have cut on the upper side. It'll come down in daylight. Just opposite me on the side hill and then it'll come around and there will be a fill section so that you can get a platform built in around this pivot point here. Let's say we go completely out to the edge of that so I know how much we have to work with. So we have almost eight feet which would give us plenty of room to build up a rock retaining wall. Fill out across to the center and out to the edge of the trail and still have some slope there. Now that's our lower leg and that's the fill section. I'll have you pivot around this point and you might as well put your daylight section in. The daylight section is simply where the side of hill is no longer a cut and fill section. It's just very flat. All right that looks good and let's mark our upper point on a horizontal distance. Okay what we've just laid out would be a five-foot radius curve and if you can visualize how this will work there will be at least two feet of fill in this section with a two-foot wide tread. It swings around hits this daylight section and then it becomes a cut section that swings up to that particular point. Obviously that will be cut down and we can approximate about a three-foot cut. So if it's cut three feet here that has to go back up the hillside. I'm going to estimate about 12-15 feet. We have a difference in elevation from the daylight section of this switchback to the upper cut section of four feet ten. We never build switchbacks completely level. There are reasons for having some grade to switchbacks. Primarily it is to get water to move off of your switchback. So we don't cut four feet ten inches. We can figure out what our grade is going to be throughout this swinging radius here by taking the rule of thumb being two thirds of the grade that you want for an approach in and the approach out. Generally those are the same. We'll probably just for a hundred feet in and out have the grade being at ten percent to get a little better flatter turn not so steep around the switchback. So we have a grade around our switchback of about seven to eight percent. Okay now that we've established this is the control point and we've got a little flat bench here more or less and we can lay out a switchback here. We're going to go in and connect this piece of trail into the original trail. We're going to do that by taking some clino shots and putting in about a 15 percent grade. You shouldn't be out here laying out any type of trail without a clinometer. It measures rise or fall in 100 feet to give you percent. In other words a 10 percent grade would mean that it's 10 feet rise or fall in 100 feet. Okay Justin we're almost online here that's 10 percent. Okay thanks. Well we're back on our original trail and we've established a grade line here. We've tied in and we've cut off a lot of our very steep washing trail up above us. It'll join up with this trail now that comes up from the bottom. We'll have to build a switchback around this point and we've established where our new trail is. This is the reconstruction new construction. So the next step is to go up and build a switchback. It's important to slope the cuts and the fills so they stay in place. Otherwise they will quickly slough away and your switchback will disappear. If the hillside is less than 50 slope you may consider building your switchback without retaining walls. You simply pile the material you remove from the uphill side onto the downhill side and pack down each layer as you go. This is called building on a fill slope and it only works if the fill will stay in place by itself. You need to know about soils and how stable they are. Loose soils like decomposed granite will never hold on a fill slope. When building on a fill slope won't work you need at least one retaining wall. Rarely if ever would you build a switchback without a retaining wall on side slopes over 50 percent. Retaining walls can be made out of rock, timber or log cribbing or gabions. You may also need a retaining wall on the cut slope and possibly a rock barrier or retaining wall around the pivot point and that will help keep people from shortcutting. Try to build dry or unmortared rock walls as near vertical as you can. A dry wall is either held together or torn apart by gravity. Gravity will pull the rocks together if they're stacked nearly vertical. Round or potato rocks are hard to build with. They're not a very good choice. All right so we're back we're up here on this bench and we've posted signs on the trail below to tell visitors that trail work is in progress. Okay now we're into the construction phase of the switchback and there are several things that'll go on simultaneously but one of the first things that we need to establish is where the retaining wall with all these rocks will be laid out and layered in appropriately. Then that starts the position for all of this fill on top to come down and layer and on top of the rock. So we need a retaining wall we need to clear some of the vegetation so that we're not filling on top of grass and duff that does not compact very well. Let's get started. We'll start with the switchback and not build the last 50 feet or so the approach trail at either end until the switchback is well underway. That allows us to get the drainage just right to conform with the final switchback. That's a lot easier to adjust the approach trails than it is to move the switchback to fit the trail. Okay Charlie then once we get the vegetation off what we need to do is get this at an angle this material here without taking the edge off we're going to bench it it would be a good term for it so that we can start building up these rock into a retaining wall. Okay let's see if we can lay some rock in here okay now you can continue around the turn of the curve here coming up the hill now. What we still have in position here is the lower leg the center line flagging that will give us an idea that that is the center of the trail here. We've already got a good retaining wall established the base part of this retaining wall. We're going to take it all the way out to where the run out of our fill for the tread will be. Now the important thing and concept of getting these rocks placed is so that they will not shift and they won't slide once you start filling on top of them and in fact the shape of the rock that where it slopes into the hillside that means that gravity is going to work with you on these rocks when you start filling on top of them. So you need good solid big rocks for your base rocks and you need to key them into the slope and that means having a slight angle into the bank and then that accepts the fill as you start bringing your wall up. You have to build enough of the wall to have a place for the material you dig from the uphill side of the switchback. Once you have the wall partly completed begin digging just as far uphill from the pivot point as your footing was downhill. Tamp the fill as you go. The switchback is starting to take shape your turning platform will become more and more level. Keep in mind that switchback construction the cut will become the fill and you're probably going to come up short and have to get material in another place. Just remember switchback construction takes a lot of work and there's a lot of volume involved. Well as we stand now we've raised this ground nearly three feet layering it in rock and gravel and then more rock and gravel and what we're going to do is kind of swing it around and tighten with this section here we're going to take it down about a foot foot and a half but this rock kind of poses a problem right here. We've been banging and pounding on it all day and trying to pry it out but it's just stubborn so what we're going to have to do is blast it see if we can't get it out then and then then all this will tie together nicely. Having good drainage on a switchback is essential adding even more complexity but the last thing you want is to have your investment washed down the hillside. There are several ways to get good drainage. Standard trail specifications call for in sloping the upper approach trail and digging a lead-off ditch that spills the water off the end of the switchback. We used to construct water bars at the center of the switchback at the daylight section but this creates a hazard for mountain bikes so now we recommend building a drainage structure at the top approach. When you do that be sure you drain it at the lower approach with another structure. Okay what we're going to do here is construct what's called a rolling dip. Now since we have a natural dip here we'll use this what we want to do is clean out the inside level it out a little bit and then slope it down gradual into the dip and slope it out so it's an easily nice easy climb in and climb out. This way we're doing this to kick the water off that's coming down the trail before hits our switchback. Now our switchback is of rocky material and normally we would ditch it out but since we have this dip we'll use it to kick the water off and prevent any kind of erosion down farther. Finally the switchback is done. The rock has been blasted out of the way it has a good turning radius and grade. We're pretty happy with this one. We're at the switchback that takes off from the main trail into our reroute the new location above us here and this switchback is approximately 80% done. One of the reasons that we didn't complete it is we have a fairly significant barrier here with this solid rock. We did try rocks and pry bars but unfortunately it didn't break up completely. So we developed the tread through here and got an in slope going around this corner. The purpose of this in slope is to take any of the drainage that will come off of the trail and get it to roll down into the stitch line and there will be a little bit larger ditch when we complete it but it goes off the trail at that point. The point that we started building this trail was right down here at this retaining wall and of course again we keyed in the rock at the base of it made sure that those were good and solid and base to bring up the retaining wall. After you start laying the retaining wall rocks then you have to bring in fill and more rock so really we're just about done with this switchback. We'll need to come in and blast some rock out of it. Now 100% done. The switchback looks good for grade and drainage. The rock is gone and the old trail is obliterated. We've successfully completed our tie-in. This brings us to the bane of most trail crews blocking off switchback shortcuts. Travelers will take whatever route is most attractive to them. No amount of barricading will keep them on a trail that doesn't match the purpose. So when you figure out why your users are taking shortcuts you can decide on a solution that will work. Short cutting often occurs because the trail is not as steep as people want to climb. Hikers on the move want to climb or descend quickly. Usually a switchback needs a barrier between the upper and lower side to prevent shortcutting. Take advantage of natural barriers like trees, down logs and rock outcroppings. When natural barriers aren't available you'll need to build some type of wall between the approaches. Build some kind of barrier even on shallow slopes or brushy hillsides. On heavy use trails especially those with mixed uses travelers will often take shortcuts just to get around each other safely. Consider building some official shortcuts with steps and check dams. Maybe you can build turnouts and wide spots for passing too. When it comes to switchbacks 90% of the work most trail crews do is either reconstruction or maintenance not new construction. Routine switchback maintenance means cleaning ditches, repairing water bars, patching walls, cutting brush or adding a few rocks to the inside barrier wall. But if you have a switchback that needs a lot of work over and over there's some inherent problem with the structure. You need to figure out what that problem is then reconstruct the switchback so it stays in good condition. Sometimes improper drainage is the problem. If the switchback has an inside ditch that doesn't seem to collect water you can build a rolling dip or a short grade reversal at the point where the upper trail begins its in slope. This is an example of a switchback that was constructed and either wore out or just didn't have the proper construction in the first place. It's on a steep side hill here probably 60% grade so the solution to it is to construct a retaining wall in the lower side and then pull the cut material down into the retaining wall. That will create a platform that will make a better transition across the switchback. The solution to approaches that are too steep to the switchback is to extend the pivot point further out on the hillside lengthening the approaches. Be careful though because that might encourage shortcutting. Repair any skid trails left from dragging rocks or logs. Finish by re-establishing vegetation. You may buy or collect native seed to spread on large disturbed areas. At the least you should mulch bare soil with duff, dead grasses and leaves. This is more than just a finishing touch it can be a big project something you should think about when you decide whether or not to relocate a particular section of trail. So I hope that some of these ideas and concepts that we've shown you in this program will help you in your next project and remember if you build your switchback right with routine maintenance they'll last for decades.