How to Build a Trail Turnpike

How to Build a Trail Turnpike
Crossing terrain with high water levels presents a challenge for trail builders. The trail turnpike is a construction concept developed as a minimally-invasive footprint in the natural landscape. The technique builds a trail above the water level and works in generally flat areas over boggy soils. The quantity of the materials needed varies with the length of the turnpike.


Difficulty: Challenging

Preparing The Trail Turnpike Site

Things You’ll Need:
  • Spade shovel
  • Garden rake
  • McCleod hoe
  • Mattock pick
  • 5-foot wide Geotextile
  • Rocks, 6 to 10 inches in diameter
  • Minimum 6-inch peeled logs
  • Gravel
  • String
  • Surveyor stakes
  • Large waterproof tarp
Step 1
Clear the site wide enough to accommodate the trail's tread--its walking surface--and adequate room for drainage ditches plus the retainer rocks or logs on each side of the tread. Work within the trail alignment to keep the disturbed area to as narrow an alignment as possible.
Step 2
Retain stiff branches to use as stakes holding the geotextile and retainer logs in place. The best branches for this purpose are 2 to 4 inches in diameter.
Step 3
Protecting the geotextile from damage or ripping is critical. When there are pointed rocks, stumps from trees or brush, or any object that could puncture the cloth, remove it completely or at least trim it to ground level. Soil too wet to work with a shovel means the turnpike is not the right solution. Either a boardwalk (called a puncheon) or a causeway construction technique will be required.

Trail Turnpike Construction

Step 1
Run a length of string tied to surveyor stakes down the two sides of the trail marking its alignment. Digging a V-shaped ditch on each edge of the trail width deep enough to keep water below the level of the geotextile and retaining rocks or logs is the start. Save the spoils (the dirt removed) placing it on a tarp or in a cart.
Step 2
Unroll the geotextile down the length of the trail overlapping any seams by three to four inches. Place the retaining rocks or logs parallel to the ditch at the sides of the tread area. Use the wooden stakes pounded into the ground on the outside of the logs and through geotextile to hold both in place. With rocks as the retainers, use the stakes to hold the geotextile in place.
Step 3
Fill the area between the retainers with soil in layers, packing each layer. The filled tread should be a slightly curved surface directing water away from the center of the tread into the ditches. If soil is exceptionally moist, a 1- or 2-inch layer of gravel on top of the geotextile helps drain water from the tread. The center of the tread should be about two inches higher than the edges for treads of 3 feet or less. Add one inch of center height for each foot of width on the tread over three feet.
Step 4
Incorporate natural or built drainage structures at each end of the trail. This ensures that water diverts into the ditches without cross-cutting the tread and that water exits the ditches without flooding the downstream end of the trail. Depending on depth of ground water and length of the turnpike, it may also be necessary to cut places in the ditches to periodically accommodate water outflow.

Tips & Warnings

A lawn roller can help with smoothing the turnpike's tread during construction.
The tread must always be higher than the water table.
If the tread is narrow, it may be necessary to install a rope or chain hand rail
When setting the drainage, ensure that the turnpike does not block flowing water, which results in the turnpike becoming a dam.
Align entries to the trail at 90-degrees so users are not tempted to short-cut an angle resulting in damage to the drainage system.
If gravel is used, it is beneficial to use a geotextile that a little more than double the width of the tread. Create a gravel sausage by wrapping the wide ends of the geotextile back over the top of the gravel. This keeps dirt from clogging the gravel.

Article Written By Eric Jay Toll

Eric Jay Toll has been writing since 1970, influenced by his active lifestyle. An outdoorsman, businessman, planner and travel writer, Toll's work appears in travel guides for the Navajo Nation, "TIME" and "Planning" magazines and on various websites. He studied broadcast marketing and management at Southern Illinois University.

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