Tread (continued)

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.

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. Some one 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.

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.

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.

Rocks should be removed to a depth of at least 100 mm (4 in) below the tread surface, or in accordance with your specific trail standards. Simply knocking off the top flush with the existing tread may mean a future obstacle as erosion removes soil from around the rock.

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.

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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