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Trail Construction and Maintenance Notebook

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.

[diagram] Reestablishing outslope removing slough and berm
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.

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