Feature Article - May/June 2003
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Trail Guide

Building multiuse trails and bridges

By Kyle Ryan


Building bridges

Bridges, however, will be pricier and require more than just Internet research. It all depends on the situation to determine whether you need a simple, short wooden bridge to cross a small creek bed, or if you need a 200-foot steel suspension bridge to cross a river or highway.

PHOTO COURTESY OF ENWOOD STRUCTURES LLC
Covered bridges can offer lots of design options for additional shelter and safety.

According to Stan Elliott, a structural engineer with a trail bridge company, span is the biggest factor in determining bridge type. A simple 30-foot bridge (which can cost about $10,000) employs a straight beam system. Bridges in the 50- to 200-foot range (which can cost about $225,000) use a truss style. Beyond that, you're getting into suspension bridges, which cost upwards of half a million dollars.

There are numerous companies who build prefabricated bridges and ship them to trail sites. All you have to do is anchor them into the ground once they arrive. For larger bridges, some manufacturers can arrange for subcontractors to take care of the foundation work and other heavy-duty construction.

Elliott's company specializes in 10-foot wide bridges, a standard width that can accommodate multiple users simultaneously, such as two snowmobiles going in opposite directions. Pedestrian bridges can be as narrow as six feet.

Other factors to keep in mind besides width, Elliott says, are the type of finish, clearances and wearing surface. The type of finish refers to the bridge's material, such as painted steel or weathering steel. Weathering steel develops a surface coat of rust that doesn't damage the structure or need to be painted. Clearances are obviously important when traffic, be it river or road, passes below. Everything must be high enough. Finally, the wearing surface, that is, what endures the wear and tear from trail users, varies depending on who uses the trail. For example, snowmobiles can destroy wood pretty quickly, so they need something harder like concrete or steel.

People power
PHOTO COURTESY OF ENWOOD STRUCTURES LLC
A trail bridge at Saluda Shouls Park in Columbia, S.C.

Even though you might need heavy-duty construction when it comes to bridges, volunteers are your best bet for help with trails. Chances are there are numerous people in your community who would be more than willing to help lend a hand constructing a trail they will use.

Even though he hasn't gotten permission to build his trails yet, Matt Lebow easily signed up more than 100 people to help with construction. The American Hiking Society offers has a popular program called "Volunteer Vacations," where, for a minimal fee (around $80), people visit backcountry locations to help rebuild trails, shelters and more.