Bridge Policy

This is a strawman proposal for what our bridge policy should be. It is copy of the ATC/NPS bridge policy which needs obvious changes to adapt to our use.

Copy of ATC/NPS bridge policy

Stream Crossings and Bridges

Traditionally, stream crossings have provided hikers with varying degrees of adventure and tales to be 
told around campfires. A simple, well-designed ford or a few step-stones suffice for most stream crossings during all or most of the year, except after heavy rains or spring runoff. Others cannot be safely crossed without bridging. However, bridges are expensive and need frequent maintenance. They are usually artificial intrusions into a natural environment and occasionally can be the object of graffiti or
other vandalism.

Existing Policy

ATC Policy—A policy on bridges and stream crossings was adopted by the ATC Board of Managers in April 1995 and amended by the ATC Board of Directors in November 2008 to reflect changes in the structure of the organization. The policy does not reflect current agency requirements or address accessibility for persons with disabilities and will need to be updated. Also note that due to the difficulty and expense of obtaining engineering assistance, the bridge design handbook and the bridge construction checklist referenced below in the Footbridge Design section have not been undertaken by ATC.
ATC’s bridge policy currently reads as follows:

 

Bridge Location—The footpath of the Appalachian Trail should be located to minimize the need for stream crossings and bridges. However, in some areas, the best route for the Trail may require stream crossings. Fords, step‐stones, or bridges should be located and installed to improve safety, minimize impacts to natural resources, or enhance the hiking experience.

Because bridges may detract from the natural, remote, and wild character of the Trail, ATC encourages the use of the simplest means available that will assist in providing a safe passage for Trail visitors. A simple, well‐designed ford or a few step‐stones may be used for most stream crossings. Unbridged stream crossings may be impassable shortly after a storm or during late winter and spring runoff; others may provide a certain measure of challenge even in low‐water conditions. These primitive conditions are essential to the Appalachian Trail experience and deserve protection.

A bridge should be constructed or replaced only if:

  1. It is essential to hiker safety during the snow‐free hiking season, recognizing that a stream may be unfordable when seasonal or regular flooding occurs; or
  2. It is absolutely necessary to protect sensitive resources, such as soils along a river’s bank.

Coalignment with Public Roads—In situations where the Appalachian Trail is coaligned on or under a bridge with a road or highway, ATC will seek to ensure that state or local departments of transportation include adequate provisions for safe pedestrian use of such facilities. Provisions may include barriers or grade separations between pedestrian and vehicular traffic, adequate roadway/pedestrian‐way widths, appropriate surfacing and drainage and other design considerations for the pedestrian pathway, including approach trails or sidewalks at each end of the bridge. These coalignments should be designed according to standards established by the American Association of State Highway Engineers and Traffic Officers (AASHTO). Coalignments should include appropriate signs for motorists and pedestrians and avoid or minimize at‐grade crossings by the Trail of the vehicular‐way on the bridge. Unless agreement is reached to the contrary, ATC expects that the agency responsible for construction, inspection, and maintenance of the bridge will also be responsible for the design, installation, and maintenance of the pedestrian portion of the coalignment.

Footbridge Design—A footbridge is defined as a permanent, artificial structure not in continuous contact with the ground, regardless of length, width, or height above the surface, with a load‐bearing free span between abutments or sills, for passage over streams or wetlands. Bog bridges or puncheon used for Trail hardening and fence stiles are excluded from this policy. For the purposes of this policy, bridges are classified into two categories. Large bridges are those that are 35 feet or more in free span. Small bridges are less than 35 feet in free span. All A.T. bridges, regardless of their span, should be designed to bear a load that meets or exceeds current best management practice for architectural design and engineering of pedestrian structures for remote, recreational trail environments.

ATC will work with qualified engineers to prepare primitive, nontraditional bridge designs that meet safety objectives. These designs will be compiled into a bridge‐design handbook that will be available for use by management partners. New bridges constructed in accordance with one of these designs will not require additional engineering review unless required by the appropriate cooperating land‐management agency. ATC will prepare a bridge‐construction checklist to summarize essential characteristics, such as bridge deck widths, surfacing, slope, stringer sizes, railing requirements, abutment, and stream‐channel characteristics.

Designs for large bridges require review by a qualified engineer. In the event that such a review cannot be provided by an agency partner, the club proposing the bridge will arrange for review by a qualified engineer with oversight provided by ATC. No large bridges will be constructed without approval by ATC pursuant to the following process.

The sponsoring club’s proposal for a large bridge should include a summary description of the need for the bridge, a map showing the location, construction details (such as drawings or blueprints) that show the bridge’s elevation (side view), maximum span, and the species, diameter, and condition of proposed bridge stringers, and a statement of support or endorsement for the structure from the landowning agency. Finally, the club proposal should include a commitment to periodic inspections and periodic maintenance. The maintenance schedule and procedure should be specified by a qualified engineer during the design phase.

Inventory and Maintenance—Future Trail‐assessment inventories (see Appendix H) should distinguish large from small bridges as defined by this policy and any other details critical to ATC’s oversight of essential characteristics with a bearing on safety.

Large bridges should be inventoried by ATC and the Trail clubs and periodically inspected by the landowning agency partner, ATC or their designees. ATC should allocate necessary and qualified staff time and budgetary resources to complete an inspection program where no active agency partner is now performing periodic inspections. These areas include NPSacquired lands outside of established national parks and some state‐administered Trail segments.

Small bridges will not be monitored by ATC. However, clubs and agency partners are urged to establish and follow appropriate inspection and maintenance procedures, as they do now for any structure that bears people.

 

NPS Policy—Trail bridges may be used for crossing swift waters areas prone to flash-flooding, and other places that present potential safety hazards. Less obtrusive alternatives to bridges (such as fords) and trail relocation will be considered before a decision is made to build a bridge. A bridge may be the preferred alternative when necessary to prevent stream bank erosion or protect wetlands or fisheries. If a bridge is determined to be appropriate, it will be kept to the minimum size needed to serve trail users, and it will be designed to harmonize with the surrounding natural scene and be as unobtrusive as possible (section 9.2.2.9 of the 2006 NPS Management Policies)

On National Park Service lands, an environmental review in accordance with the National Environmental Policy Act is required prior to construction of a bridge more than 35 feet in length or in any situation where bridge construction would require significant excavation.

Considerations for Planning

Inventory—The Trail club should have an inventory of all major stream crossings and existing bridges. A short list of the existing bridges and unbridged major stream crossings should be included in the plan as an appendix. The Trail-assessment process (Appendix H) currently being administered by ATC and the National Park Service includes bridge inventories and can be used to identify the actual span of an inventoried bridge, as well as the age of the structure and the condition of its stringers, decking, railings, and hardware. Clubs should update their inventory during Trail-assessments, when updating their local management plans, and when bridges are installed or receive major maintenance.

Setting Trail Club Policy—The Trail club should evaluate the need for bridges, based primarily upon a minimum standard of safety. The primary issues of safety, aesthetics, and need for bridges should be addressed. If other alternatives for safe crossing of a stream exist, they should be considered first. The club policy statement should address the need for coordination with its agency partner and other agencies.

Action Plan—If any existing stream crossings are recognized as unsafe, the Trail club should evaluate what steps are necessary to provide a minimum standard of safety. Bridge inspections should be a normal part of Trail maintenance and should be recognized in Trail-maintenance plans. A regular bridgeinspection routine is particularly important for bridges located on NPS-acquired lands and state lands. If a Trail club does not have the expertise to conduct bridge inspections, it should contact ATC to arrange for an inspection by a qualified engineer. (Note: the U.S. Forest Service has developed a Trail Bridge Catalog that includes bridge plans as well as information on planning, siting, designing, constructing, inspecting, and maintaining trail bridges. Trail clubs should consult with their agency partners and ATC regional office on bridge construction and before using any of these designs.)
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