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Trail Construction and Maintenance Notebook

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Tread

Tread Surface

Tread is the actual travel surface of the trail. This is where the rubber (or hoof) meets the trail. Tread is constructed and maintained to support the designed use for your trail.

Most trail construction revolves around making sure solid, obstacle-free tread is established and enough protection is provided to keep it in place. If you don't do a good job of locating, constructing, and maintaining tread, the users will find their own pathways instead.

Outsloping is the first line of defense against tread erosion. An outsloped tread is one that is lower on the outside or downhill side of the trail than it is on the inside or bank side. Outsloping lets water run naturally off the trail. A 500-mm (2-ft) wide trail would have an outside edge 30 to 60 mm (1.2 to 2.4 in) lower than the inside edge. Tread is also the travel surface on structures like turnpike and puncheon. Tread, whenever elevated, should be slightly crowned to drain better.

Tread Creep

Does your sidehill trail display:

  • Exposed bedrock or roots along the upper side of the tread?
  • Daisy-chained tread alignment (Figure 14)?
  • Pack bumpers, jump-offs, and prominent tread anchors?

Photo of a trail with trail creep.
Figure 14--Some classic signs of tread creep.
This trail needs help now.

All three are indications that the tread surface has been eroded and compacted by travel along the lower edge. Insidious tread creep at work. Tread creep should be arrested or the trail will eventually become very difficult or dangerous to travel.

What causes tread creep? The answer is simple. Most livestock, two-wheeled traffic, and some people have a natural tendency to walk the outside edges of sidehill trails. Sloughing makes the edge the flattest place to walk. As the tread moves downhill, it also narrows, with the result that more traffic travels closer to the outer edge. Other causes of tread creep are constructing a trail that is too narrow or with cutslopes that are too steep. Your job is to bring the trail back uphill to its original location and keep it there (Figure 15).

Image of the causes of trail creep.
Figure 15--Tread creep at work--
sloughing and soft fillslopes.

One of the best ways to do this is to take advantage of large stationary objects (guide structures) to prevent animals and people from walking the edge. Trees, log ends, rocks, and stumps left close to the downhill edge of the trail will keep animals walking closer to the middle. Guide structures should be no more than 500 mm (1 ft) high so they will not catch animals' packs.

Curb rocks need to be well anchored, and they should be placed at random distances so they don't look like a wall or trap water on the tread.

Tread between these anchors will creep downhill creating a situation where the trail climbs over every tread anchor and descends again. At the bottom of these "dips," water and sediment collect. This is the weakest portion of the tread and the most prone to catastrophic failure. The tread can be so soft that packstock may punch completely through the tread (called a step-through) or bicycles or dirt bikes may collapse the edge. The result can be a bad wreck.

Where soil is in short supply, you may have to install a short crib wall and haul in tread material. Thin tread on bedrock will not usually stay put without some support. If normal slough removal does not work on more substantial soils, the tread should be

benched back into the slope in the original alignment. Guide structures should be installed on the outside edge of the tread to keep traffic toward the center.

A note on guide structures: If you use a rock, be sure it is big enough that at least one-third of it may be buried (so people and bears won't roll it away) and it will still be obtrusive enough that hikers and horses won't walk over it (Figure 16). Log ends should be sawed back at an angle if the top edge of the log is more than 500 mm (20 in) above the tread. If you have really substantial berm to remove, leave 1-m (3-ft) long portions at 3- to 5-m (10- to 15-ft) intervals with the ends feathered into the fillslope to serve as guide structures.

Image of stabilizing tread creep.
Figure 16--Guide rock properly installed
to help prevent tread creep.

Slough and Berm

On hillside trails, slough (pronounced "sluff") is soil, rock, and debris that has moved downhill to the inside of the tread, narrowing it. Slough needs to be removed (Figure 17). Removing slough is hard work, and is often not done adequately. Leaving slough is another reason trails "creep" downhill.

Image of reestablishing outslope.
Figure 17--Remove the slough and berm, leaving the trail
outsloped so water will run off. One fist's worth of drop for the
length of a Pulaski is a good rule of thumb.

Loosen compacted slough with a mattock or Pulaski, then remove the soil with a shovel or McLeod. Use excess soil to fill holes in the tread, or on the downhill side of waterbars. Reshape the tread to restore its outslope. Avoid disturbing the entire cutbank unless absolutely necessary. Chop off the toe of the slough, and blend the slope back into the cutbank.

Berm is soil that has built up on the outside of the tread, forming a barrier that prevents water from running off the trail. Berms are a natural consequence of tread surface erosion and redeposition, and of inadequate compaction during construction. Berms prevent water from flowing off the trail. Water runs down the tread itself, gathering volume and soil as it goes. Berm formation is the single largest contributor to erosion of the tread surface. Removing berms is almost always the best practice. Observe erosion on trails with and without berms, see what works best in your area, and ask the project leader for a recommendation if you are in doubt.

Berms also trap water in puddles on level portions of tread and at the bottom of dips. Trapped water contributes to soil saturation, greatly reducing tread cohesion. Saturated tread material is prone to mass wasting and step-throughs.

Berms, especially when associated with tread creep, may form a false edge. False edge is unconsolidated material, often including significant amounts of organic material, that has almost no ability to bear weight. This is probably the least stable trail feature on most trails and the major contributor to step-throughs and wrecks.

Berms should not be constructed intentionally. Guide structures or even guard rails, if appropriate, should be combined with tread outsloping to keep users on the center of the trail and water off of it.

Tread Maintenance

Maintain tread at the designed width. This means filling ruts, holes, and low spots. It includes removing obstacles such as protruding roots and rocks. It also means repairing any sections that have been damaged by landslides, uprooted trees, washouts, or boggy conditions.

Tread maintenance aims for a solid, outsloped surface. Remove all the debris that has fallen on the tread, the sticks and stones and candy wrappers. Pull the lower edge berm back onto the tread surface and use it to restore the outslope. Use any slough material in the same fashion. Remove and widely scatter organic debris well beyond the clearing limits, preferably out of sight.

Removing Roots and Stumps

Removing roots and stumps is hard work. Explosives and stump grinders are good alternatives for removing stumps, but chances are you'll have to do the work by hand. A sharpened pick mattock or Pulaski is most often used to chop away at the roots. If you are relying on some type of winch system to help you pull out the stump, be sure to leave the stumps high enough to give you something to latch on to for leverage.

Not all roots and stumps are problems. You should not have to remove many large stumps from an existing trail. Before you do so, consider whether a stump was left the last time around to help keep the trail from creeping downhill.

Rock Removal

Rock work ranges from shoveling cobble to blasting solid rock. Both ends of the spectrum are often specialty work. The good blaster can save a crew an astounding amount of work. Someone building a rock retaining wall may be a true artisan, creating a structure that lasts for centuries. The key to any decent rock work is good planning and finely honed skills.

The secret to moving large rocks is to think first. Plan out where the rock should go, and anticipate how it might roll. Be patient--moving rock in a hurry almost always results in the rock ending up in the wrong location. Communicate with all the crew about how the task is progressing and what move should occur next.

Rule of thumb for roots--if perpendicular to the tread, fairly flush, and not a tripping hazard, leave them. Remove roots that are parallel with the tread. They cause erosion and create slipping hazards. Look for the reason the roots were exposed and fix that problem.

Tools of the trade include:

  • Lots of high-quality rockbars; don't settle for the cheap digging bars, you need something with high tensile strength.
  • Pick mattock.
  • Sledge hammer.
  • Eye protection, gloves, and hardhat; don't even think of swinging a tool at a rock without wearing these.
  • Gravel box, rock bag, rucksack, rock litter; items useful for carrying rock of various sizes.
  • Winch and cable systems; some rocks can be dragged or lifted into place.
  • All sorts of motorized equipment, including rock drills and breakers.
Remember that the two most common injuries in rock work are pinched (or smashed) fingers and tweaked (or blown out) backs. Both sets of injuries are a direct result of using muscles first and brains last. High-quality rock work is almost always a methodical, even tedious task. Safe work is ALWAYS faster than taking time out for a trip to the infirmary.

Blasting is useful for removing rocks or greatly reducing their size. Careful blasting techniques can produce gravel-sized material. Motorized equipment can be used to split boulders or to grind down projecting tread obstacles. Chemical expansion agents poured into drilled holes will break large rocks without explosives. Drills and wedges can be used to quarry stone for retaining walls or guide structures.

Your specific trail maintenance specifications may call for removing embedded rocks. Use good judgment here. Often very large rocks are better removed by blasting. Other solutions include ramping the trail over them, or rerouting the trail around them.

Rockbars work great for moving medium and large rocks. Use the bars to pry rocks out of the ground and then to guide them around. When crew members have two or three bars under various sides of a large rock they can apply leverage to the stone and virtually float it to a new location with a rowing motion. Use small rocks or logs as a fulcrum for better leverage.

When dealing with rocks, work smarter, not harder. Skidding rocks is easiest. Rolling them is sometimes necessary. Lifting rocks is the last resort.

It may seem like fun at the time, but avoid the temptation to kick a large stone loose. When rocks careen down the mountainside they may knock down small trees, gouge bark, wipe out trail structures, and start rockslides.

Even worse is the possibility an out-of-control rock might cross a trail or road below you, hitting someone. If there is any possibility of people below, close the trail or road, or post sentries in safe locations to warn travelers of the danger.

You might construct a barrier by laying logs against two trees to stop a rolling rock before it gains much momentum. Once a rock is loose, do not try to stop it.

When you need to lift rocks, be sure to keep your back straight and to lift with the strong muscles of your legs. Sharing the burden with another person is sometimes a good idea.

To load a large rock into a wheelbarrow, lean the wheelbarrow back on its handles, roll the rock in gently over the handles (or rocks placed there) and tip the wheelbarrow forward onto its wheels. Keep your fingers clear any time you deal with rocks.

Small stones are often needed for fill material behind crib walls, in turnpikes and cribbed staircases, and in voids in talus sections of trail. Buckets and wheelbarrows are handy here. So are canvas carrying bags. If you are part of a large crew, handing rocks person-to-person often works well. Remember, twisting your upper body while holding a heavy rock usually isn't a good idea.


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Updated: 04/14/2014
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