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  Trail Care Crew Tip

Curb Erosion By Hardening Problem Spots

Jan and Mike Riter, Subaru/IMBA Trail Care Crew

The sustainability of our trails has a lot to do with the kind of soils we have to ride on. If your mountain biking area was once covered by glaciers, or if you live on the coast or in a desert, it is probably more difficult for you than the rest of the country to keep your soils in one place. You may also face serious erosion problems on a fall-line (steep) trail that ideally should be rerouted, but for whatever circumstances, you cannot alter the trail placement. Or you have a high equestrian or motorized use causing soil to end up at the bottom of the hill. Our goal in this column is to introduce you to three trail hardening techniques that will help in problem areas.

The first method is our favorite because of the look of disbelief it provokes: kitty litter. A generic, low-grade kitty litter has a substantial clay content which, when added to a trail, will act as a binder to help keep things together. The cheaper the litter, the better it will harden. The good folks of Michigan Mountain Bike Association discovered this gem. Let's say that at the bottom of a hill there is a sand pit that has the potential to pull down riders like quicksand. Purchase enough kitty litter to mix 50/50 with the sand, and you'll soon sail through with ease. The trick is to mix it thoroughly and if possible, install it just before a rain. Or, if your weather person is as inaccurate as ours, bring your own water. The Wisconsin Off Road Bicycling Association (WORBA) has perfected the God-like act of rain-making by using a pressurized fire extinguisher to spray the trail with water. This way, once the litter is blended as deep as possible, you can form the tread to drain water and the moisture will cause it to pack firmly together. (Be careful not to create a berm.) Another option discovered by WORBA is to add a limestone road base to the mixture with the kitty litter. The end result is a stable riding surface that is a lot more fun.

Pouring Kitty Litter Comparing Soils
Before and after kitty litter: loose in
the left hand; cohesive in the right.

A second technique is to use a byproduct of iron smelting called "slag" We saw it used in a state park in Maryland and we studied the chemical composition of the slag and its effect on the environment. It does not sound that appealing, but both visually and environmentally it is much more friendly than its name would imply. The really good part is that because it is a waste product, it can usually be acquired for free or very little cost. It is especially useful in wet or boggy areas when reroutes are not possible, filling in between protruding rocky areas, or building turnpike (raised) tread.

When installing slag, the process is similar to spreading gravel. The consistency and weight means that it will have to be brought in by wheel barrow or trucked into the work site. Once you have it there, spread it evenly to a depth of several inches and pack it with a McLeod or other compacting device. A period of 24 hours is usually enough time for it to dry into a stable tread surface. Once finished, you can tell that something was added to the trail to hold it together, but it is far from unsightly, and is a plausible solution to extremely tough areas to fix.

Finally, you can turn to grass pavers. The pavers are similar to concrete blocks, except that they are two feet square and six inches deep; the openings are diamond or various other patterns.

The installation is difficult and time consuming, but the pavers will last. Bury them into the trail tread so that the patterns will hold soil. They should also be buried into the backslope and into the downslope as well, (three wide works well). Also keep in mind that you do not want to have the edges of the pavers exposed, causing sharp drop-offs that can be intimidating. Be conscientious to bury the beginning and end pavers at a slight angle to create a subtle ramp onto the pavers. Grass pavers are more expensive than other trail hardening techniques. They are effective, but unless you have an unlimited budget and volunteer force, we recommended them only in areas where little else has worked.

These are a few suggestions that will hopefully help in the long run. Always remember that each situation is unique and should be assessed that way.

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