Guidelines and Best Practices for the Design, Construction and Maintenance of Sustainable Trails for All Ontarians - Trails for All Ontarians Collaborative 2006
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There are many ways to build a trail. Detailed information about materials and construction techniques for the trail should be developed during the trail design phase. The construction crew leader uses the detailed construction log created during trail design to ensure that the trail is constructed as intended . The specific construction techniques on each trail will vary, depending on many factors (e.g., intended trail experience, type and volume of trail users). The trail designer will have considered the range of abilities among trail users as well as environmental factors in order to determine the final trail design. The designer will also have worked closely with the landowner to ensure that the final trail design will be supported and accepted. It is important that the construction crew follow the construction log details as closely as possible , so that "as built" will be virtually the same as "as designed".
The construction techniques described in this "best practice" document are intended for use by volunteers who will be building trails without using heavy machinery . They are the recommended minimum standard for trail design, construction and maintenance. Volunteer labour and hand tools are the source of most Ontario trails. Trails professional unfamiliar with sustainable trail design will also find these "best practices" informative. It is essential that the person leading the trail construction work be thoroughly familiar with all of the design and construction standards that apply to the trail . Trail designers and construction crew leaders should strive to ensure that every trail meets not only these minimum guidelines, but also any additional guidelines that may apply to specific trails or managed lands. Otherwise, the volunteer labour used to construct the trail may be for nought if, after construction, sections of the trail do not meet required standards and have to be re-done.
Once the route is final, trail construction usually proceeds in five broad steps . The order of completion will vary depending on the specific site conditions. The steps are:
Each of these steps (described in subsequent sections) requires various materials and tools. It is important that the materials and tools be carefully chosen to ensure that they are suited to the specific task and local conditions. Making good choices of material and tools will save time and costs.
It is important that every trail be constructed in a manner that respects the natural surroundings. People use trails to make contact with the natural environment, and research clearly shows that 90% of the environmental impacts caused by sustainable trails occur during construction and initial use. It is a misconception that the environmental damage from a trail results primarily from ongoing trail use. However, if a trail is constructed using these "best practices" for sustainability and universal design, only minimal environmental impacts will occur after the first year of trail use. [56] Your challenge, as a trail builder, is to limit the environmental damage during trail construction as much as possible .
Erosion and compaction of the soil adjacent to the trail tread are the two largest problems faced by trail builders . Erosion and compaction modify the trail's local environment by changing the way that water, soil and nutrients move about. It is a common misconception that erosion and compaction are "unavoidable", as if they inevitably and naturally result from trail construction and use. This need not be the case. By constructing a sustainable trail tread , that is itself properly compacted and suitable for the type and amount of trail users, the erosion and compaction of areas adjacent to the trail tread can be largely avoided . If compaction of the trail tread will potentially damage sensitive plants or trees, the design of the trail should be re-considered to ensure that the tread is located in more appropriate soils and vegetation.
To minimize soil erosion and compaction on areas adjacent to the trail tread , design and construct your trail so that:
In addition to minimizing the erosion and compaction of soil adjacent to the trail, the uniqueness and sensitivity of trailside vegetation must also be carefully considered and appropriately managed . The aesthetic appeal of a trail is enhanced if it takes the trail user through a variety of vegetation. Vegetation can be used to protect privacy, provide vistas, and enhance public safety. Close to the trail edge, leave vegetation so that it looks undisturbed. This will discourage users from going off of the trail tread and the foliage can help to reduce the impact of rainfall on the surrounding soil. If vegetation adjacent to the trail is damaged or must be removed during trail construction, ensure that the area is re-planted with native species as soon as the damaging construction work has been completed.
The construction of a trail often also provides opportunities to carry out habitat restoration or enhancement projects. Actively look for opportunities to improve or restore the trail environment as part of your trail construction project. Within urban areas especially, there may be funding available to encourage schools to be involved in naturalization projects or for the planting of native species. Similarly, the construction of a stream crossing can often offer opportunities for projects that will stabilize rapidly eroding banks or streams with pools and riffles.
When planning an environmental restoration or rehabilitation project, be sure to obtain all of the necessary permits and approvals. Wetland projects will require approval from the Ministry of Natural Resources. Conservation Authority approval may also be required, and the staff can provide detailed information about species at risk or other special considerations that may apply to the trail environment.
The first step in constructing a trail is to complete the clearing of the trail corridor. With the initial brushing and clearing of the trail corridor completed during the design phase (see Guidelines for Trail Design - Clear Corridor ), some of the clearing work will already be done. At this stage, the crew follows along the final flag line for the tread alignment, ensuring that all vegetation and obstacles (e.g., rocks) have been removed. There are three goals for this clearing work:
In most places, especially in southern Ontario, clearing the trail corridor will require removal of the existing vegetation. On the trail tread, all organic material must be removed in order to optimize the sustainability of the constructed tread over time. Adjacent to the trail tread, it is usually best to leave as much of the natural vegetation as possible . A well-designed trail will minimize the need for vegetation removal by taking advantage of naturally occurring clearings and not requiring the removal of larger trees (which are an important environmental and aesthetic asset).
It is also important to remove all objects that protrude into the trail tread area . Rocks protruding from the trail tread are a tripping hazard for trail users, particularly those who are less agile (e.g., older adults) and those who may be inattentive (e.g., children). Objects that overhang the trail tread above the ground are also hazardous. Bumped heads or "whacks" on the body are not a component of a "safe trail experience". Objects overhanging the trail tread are particularly hazardous for people with limited sight and those who may be inattentive (e.g., children).
In certain special situations (e.g., tundra and riparian areas), existing vegetation must be left as untouched and undisturbed as possible to maintain environmental quality. In these special circumstances, the trail tread must be built above and around existing vegetation (refer to Tread Structures Above the Surrounding Terrain for additional information). Contact your local Conservation Authority and office of the Ministry of Natural Resources for detailed information about what, if any, work can be undertaken in these environments.
Occasionally it may be desirable, or even necessary, to make additional small openings in the vegetation along the trail. There are a number of reasons that additional openings may be desirable (e.g., provide a view, allow a rest area, provide a break in the "tunnel effect" of continuous canopy, management of species growth by altering sun penetration). The location of these areas and the work required should be specified in the trail construction log. It is important that all decisions regarding vegetation removal be informed and approved . In areas where the clearing limits are increased above the minimum, it is helpful to include a brief note about the reason(s) for the decision in the construction log. Trail volunteers often equate the removal of vegetation with environmental damage . Therefore, it is important for the construction crew leader to carefully monitor the work to ensure that the intended clearing limits are achieved throughout the trail.
The specific methods and extent of clearing will vary, depending on the type of tread surface to be constructed. If an elevated tread surface (e.g., boardwalk, causeway) will be constructed, the initial steps to remove existing vegetation will likely not be required. However, to clear the trail corridor for safe and sustainable construction and use of a ground-level trail tread, complete the following steps:
The clearing limits for the trail corridor should be specified in the construction log. Decisions regarding the size of the trail tread area and buffer zone are made during the design phase , and are typically based on input from local environmental experts and the landowner in addition to the needs of trail users.
The clearing limits for the trail corridor will be determined by two factors:
The designed trail tread area is the width and height of clear space required by permitted trail users . For a hiking trail, the designed width should be 1.0 metre (3 feet) or more and the designed height should be 2.0 metres (6.6 feet) or more. For trails that permit other user groups, the design width and height may be increased.
The buffer zone is the area on both sides and above the designed trail tread area . The purpose of the buffer zone is to establish the sight lines required for safe trail use, minimize the damage to trailside vegetation from users who stray off of the tread, and ensure that vegetation does not encroach onto the trail tread between the times for scheduled maintenance. The buffer zone should be at least 0.3 metres (12 inches) wide on each side of the trail and at least 0.5 metres (20 inches) above the top of the designated trail tread area. Many trail managers and landowners require larger buffer zones, particularly on more remote trails where maintenance is infrequent, on trails where users may be travelling at higher speeds, or where the position of vegetation is routinely affected by heavy ice, rain or snow conditions.
Construction crews should not make changes to the plans for vegetation removal described in the construction log. If additional vegetation removal seems to be required, the trail designer, a person who knows the local natural vegetation and the landowner should be involved in making and approving any changes. Trail workers should also make sure to clear the corridor to the width specified in the construction log. Many trail volunteers may mistakenly believe that clearing less vegetation will result in less environmental impact. However, trail impact research has clearly demonstrated that the vegetation loss and vegetation impact is much greater if the vegetation removed during construction is not wide enough for two trail users to walk the trail side by side. If vegetation is not carefully cut by trail workers so that the tread and buffer zone are free of vegetation, inevitably trail users will bend or break the vegetation to get it out of their way. Broken branches often result in stripped sections of bark which leave the vegetation at much greater risk for infection. In some cases, the stripped bark may actually kill small saplings.
A wide variety of hand tools can be used for trail clearing. Specific tool choices will depend upon the type and diameter of the vegetation to be removed. Make sure that all trail workers have the training and experience to use tools appropriately and safely .
Powered mowers (e.g., string mower [57]) and weed cutters (often called "weed whip", "swizzle" or "weed whacker") can be used to quickly clear fields of grassy vegetation. If powered equipment will be used, the work crew should make a "first pass" to remove the larger saplings before the weed clearing work begins. Often, alternating passes of removing saplings and weeding are required. The saplings are difficult to see before the weeds are cleared, but the weeds are more difficult to clear when they surround more substantial vegetation. For particularly dense vegetation, a Swedish brush axe (also known as a Sandvik) can be used. It functions similar to a machete, but the shorter blade and long handle make it much safer to use.
Cutting and digging tools are sharp and care must be taken in their use. Chainsaws are extremely dangerous and should only be used by properly trained individuals. Tools that bounce or glance off tree trunks or stumps when swung are a common cause of injury among trail volunteers . Keep your tools sharp, and ensure volunteers know how to use them correctly before letting them on the trail. Everyone using these tools must have access to and use the necessary safety equipment (e.g., glasses, safety boots, gloves and leg guards).
Hand-held pruning shears and secateurs are effective tools for snipping through small twigs (less than 2 cm (0.8 inches) in diameter). Long handled by-pass pruners , anvil clippers , loppers , or folding handsaws can be used for larger saplings and twigs. Pruners and loppers are generally preferred, because they give a clean cut (allowing the bark to heal more quickly) and are safer to use and carry. Models with ratchet or power assist features can effectively cut vegetation up to 5 cm (2 inches) in diameter. Long handled tools and tools with telescopic handles are particularly important for trimming small branches from mature trees. The long handles ensure that the worker can reach into the tree and make a clean cut through the collar of the branch, adjacent to the tree trunk.
For larger branches and tree trunks of more than 5 cm (2 inches) in diameter, saws are usually the "tool of choice". Saws provide a smoother cut, are generally more efficient, and are easy and reasonably safe for volunteers to use. Handsaws are available in a variety of sizes and styles. Pruning, bow or crosscut saws are most commonly used by trail volunteers. Pole saws are useful for cutting limbs that otherwise would be out-of-reach during trail maintenance sessions (e.g., those limbs that are out of reach in the summer but in the face of skiers in the winter).
While chainsaws may be the fastest and most efficient way to clear large trees, stumps or logs, they are heavy to carry over distances and dangerous for inexperienced users. Chainsaws should only be used by individuals who are thoroughly and properly trained .
Training courses in the use of chainsaws are available through many schools and organizations. If chain saws are to be used on a trail, the work should be done by an experienced crew (the person cutting plus two assistants) at a time when other trail workers and trail users are not in the area (i.e., either before or after the other trail work in the area has been completed).
Cut large branches through the collar. If the branch is large, make the first cut up from the bottom a short distance from the collar. The second cut is made through the collar, cutting down from the top.
Grubbing tools, such as a Pulaski, McLeod, grub hoe, fire rake or mattock, are used to loosen dirt, cut through roots and remove ground cover vegetation. Workers using a Pulaski, McLeod or mattock must be constantly aware of the position of the cutting blade (which is opposite the digging tool).
Shovels are the primary tool used for digging and moving earth or rock. They are available in a wide variety of sizes and shapes. Square or flat shovels are suitable for moving loose earth and for shaping the trail tread. Round-point shovels are best for digging. Longer handles will reduce the amount of bending required but many people find a short-handle shovel better for carrying heavy loads. The optimal style and size of shovel for each trail task will depend on both the type of work being performed and the preferences of the trail workers. The pick end of a Pulaski or mattock can also be used to loosen compacted soil.
The removal of large rocks from the trail tread should be a relatively infrequent work task. In most cases, it is preferable to design the trail so that is bypasses the large rock. Bypassing the rock will have less environmental impact, and it is also less work. If the removal or relocation of a large rock is specified in the construction log, tools such as a pry bar , rock bar , digging bar , or wrecking bar will be used. In some cases, a winch or grip hoist may also be required. The person in charge of the trail crew is responsible for ensuring that the workers have the appropriate training and experience before any specialized techniques or equipment are used. Seek assistance from experienced personnel if there is any concern regarding the trail crew's ability to complete the required work.
Trail drainage structures can be used to separate the trail tread and buffer zone from natural drainage channels that contain concentrations of flowing water. The installation of any type of drainage structure will require permits or approvals from the Ministry of Natural Resources or the Conservation Authority because changes to water flow patterns in the trail environment can have significant impacts on ground on water-based habitats. The construction methods and materials must also be approved to ensure that sediment or construction debris does not adversely affect fish habitat. The permits will provide detailed information about how and when the work can be completed as well as the size and configuration of the approved drainage structure.
Drainage structures within the trail tread or buffer zone should always be of a "closed" design (e.g., culvert, drainage lens). A closed drainage structure is an alternative to building a tread surface above the water flow (e.g., boardwalk). Either a drainage structure or an elevated tread is necessary to prevent the trail tread from having a significant impact on natural drainage channels that either intermittently or continuously contain a reasonably large volume of water.
Drainage structures can be made of many materials including plastic, metal, wood and stone. Each has advantages and will influence construction work in different ways.
The size of the drainage structure, and the materials used to construct them, depend on the location of the natural drainage channel and the volume, continuity and dispersion of the water flow. The aesthetics of the trail environment are also considered during the design of trail drainage structures. The design of the drainage structure is crucial if it is to function in a sustainable manner with a minimum of maintenance. For this reason, the size, material, location and grade of the drainage structure specified in the construction log must be closely followed . The person responsible for the construction crew must assume overall responsibility for ensuring that the constructed drainage structure conforms to the specified design. The construction of a drainage structure is complex, and the steps involved vary each design . Ensure that the trail designer and crew have the knowledge required for the proper construction or installation of the drainage structure.
Culverts support the trail tread so that it does not interfere with a natural drainage channel. They are deceptively "simple-looking" drainage structures. Nothing would seem easier than to dig a trench, lay in a pipe, and put the earth back on top. However, experienced trail volunteers know that careful installation and attention to detail is required to install a culvert that will continue to function effectively with little maintenance . Whenever possible, have someone with experience (i.e., they have previously installed several culverts that worked well for more than one year) involved in the culvert installation.
In recent years, culverts have typically been plastic or galvanized metal pipes that are purchased "ready to go". Corrugated metal culverts are typically used for larger water volumes. It is also possible to build culverts using rocks or logs, but these structures require a lot more work and significantly more expertise. All culverts should have a diameter of at least 30 cm (12 inches) so that maintenance of water flow through the culvert will be easier (e.g., a shovel can be used to clear material blocking water flow).
The trail designer will have specified the size and type of culvert required in the construction log, based on the volume and frequency of water flow. From a sustainability perspective, it is essential that culverts are used to protect and maintain naturally occurring drainage channels so that they are not blocked by the construction of the trail tread. Efforts to force water through a culvert that is not in the natural drainage channel cause substantial damage to the natural environment and are rarely effective. Construction crews must be careful to position the culvert in the correct position. The construction crew leader must also ensure that all necessary permits for the use of a culvert have been obtained before the construction work begins .
The steps to install a plastic or metal culvert are:
A drainage lens is constructed below grade to allow for water movement underneath the trail tread. It is typically used instead of a culvert where the flow of water is smaller in volume or more dispersed across the terrain. A "French drain" is a term often used to refer to a very similar structure that is built into, rather than below, the trail tread. A drainage lens should be used instead of a French drain so that trail users of all abilities will be able to safely negotiate the trail.
The steps for constructing a drainage lens are:
Open drainage structures, such as ditches, French drains or bleeders, have traditionally been used to channel water in trail environments. However, using open drainage structures within the trail tread creates a trip hazard and many trail users find it difficult to navigate the water-filled channel or the uneven surface of drain rock. For these reasons, open drainage structures should not be constructed within the trail tread or buffer zone (i.e., anywhere that users may be expected to travel).
The trail designer should carefully consider the environmental impact of an open drainage structure before including it in the construction log. The advantage of open drainage structures is that they often require fewer materials (i.e., less expensive) and with little maintenance or observation they may be less likely to clog. Therefore, the construction of open drainage structures can be considered in areas away from the trail tread and buffer zone. For example, they can be used to contain water flow within a natural drainage channel that connects to a closed drainage structure (e.g., culvert) that crosses the trail.
To construct an open drainage structure:
Tread structures are used when the natural terrain cannot provide or should not be used for a sustainable tread . The structure raises the tread above the natural (i.e., difficult or sensitive) terrain. Typically, tread structures are built in areas with a lot of water (either visible water or saturated soil). Tread structures can also be used to protect areas with delicate plants (e.g., tundra) or make the surface underfoot more even and stable (e.g., crossing a rock slide).
The terminology and construction methods used in relation to tread structures varies dramatically. The feedback on initial drafts of this resource was extremely diverse, polarized and variable from trail group to trail group. Opposing and strongly held views were difficult (and in some cases impossible) to reconcile. However, there was agreement on two general categories for trail tread structures:
Intermittent contact structures are preferred for areas where water is a dominant feature of the landscape. Even if water is not visible, the construction of a continuous contact structure can significantly damage the natural drainage patterns. Continuous contact structures cannot be used in areas where delicate plants must be protected . Although continuous contact structures have historically been used extensively to construct trail tread, from a sustainability perspective they have limited use. They should be used primarily, in select locations not affected by surface water flow, when providing a more consistent tread surface is a priority.
The trail designer will consider a wide range of factors (e.g., environmental impact, permitted trail users) in deciding on the type of tread structure required. The construction of tread structures requires substantial labour, but it is often the "activity of choice" for volunteers who can easily see the results of their efforts. The primary responsibility of the construction crew is to ensure that "as built" is the same as "as designed" (i.e., the constructed structure complies with the specified design as closely as possible) and that there is as little impact on the surrounding environment from the construction activities as possible .
As previously stated, 90% of the environmental damage related to a recreation trail will occur during construction and initial use. If the trail is constructed for sustainability, the environmental impact will be almost entirely related to the initial trail construction. As a result, construction crews have almost total control over the environmental impacts that will occur . Negative environmental impacts that can result from trail structure construction typically include:
In order to minimize the environmental impact of trail structure construction, work crews should :
Prior to the start of construction, it is essential that all necessary approvals and permits have been obtained . Confirm that the local Conservation Authority and any other relevant government offices or organizations have reviewed and approved all aspects of the proposed work. Approval must be obtained not only for what will be constructed, but also the timing of construction. Exactly who will need to approve the project will vary, depending on factors such as land ownership, type of environment, natural habitat, presence of water bodies, etc. The land management agency should be able to provide the names and contact information for the relevant agencies and organizations.
Elevated tread structures are the most costly and labour-intensive aspect of trail construction. For bridges, there are additional liability concerns because the trail user is elevated above the surrounding terrain. Regardless of size, all components of an elevated tread structure must be constructed to appropriate standards for load carrying capacity. Trail designers must ensure that the structure specifications in the construction log conform to all required safety and engineering standards .
Trail volunteers use a wide variety of terminology to describe the tread structures that they build to elevate the trail tread above the surrounding terrain. For the purposes of this resource, the following terms are used:
Regardless of which anchoring technique is used, the height of the walking surface above the terrain, or the stability of the soil, the same general steps are used:
More detailed information on each of these steps is provided in the following sections.
Choose construction materials carefully!
It is critically important that the construction materials used for elevated tread structures are carefully selected based on the demands of the environment and the safety of trail users. Some types of wood (e.g., cedar) are less likely to rot , particularly if the weather allows them to dry out intermittently. An oil-based stain is suitable for lengthening the durability of natural wood structures in some natural environments. Plastic lumber products can also be used, but they will require much more extensive support structures. Regular maintenance will also be required to prevent the growth of algae which makes the plastic lumber surface extremely slippery when it is wet.
Pressure treated wood is often the "building material of choice" for tread structures because it is expected to last a long time. Until January 2004, wood was commonly treated with Chromated Copper Arsenate (CCA). CCA has been linked to health problems for many people. Since 2004, arsenic, a known cancer-causing agent, has been removed from the chemicals used to treat wood. H owever, building supply companies were, and still are, allowed to sell off existing stocks of CCA treated wood. Today pressure treated wood is typically created with chemicals such as amine copper quat ( ACQ ) or copper azole ( CA ). At the very least, these options are less toxic than CCA. However, some health concerns remain and it is still advisable to take precautionary measures when using wood treated with these chemicals. Lumber companies continue to develop non-toxic wood preservatives. Products using sodium silicate [58] are promising, but when this resource was created they were not yet available in Ontario.
Always use safety equipment when cutting and using treated wood, such as gloves, glasses, and a dust mask .Anchor sills (also called mud sills) provide support for the stringers and are the only part of the elevated tread structure that contacts the ground . Sills can be made from a variety of materials, including logs, lumber and concrete. The size and number of sills will be determined by the required load carrying capacity and the type of terrain. If the natural soils are stable, a smaller sill will be required. In areas where soils are unstable, larger sills will be required. Parking lot curb blocks make excellent sills, although they can be very difficult to transport.
The vertical dimension of the sill should ensure that the top of the sill is at least 15 cm (6 inches) above the adjacent terrain to separate the stringers from the ground. If one sill is not high enough, a small crib can be built. To build a crib, put two logs parallel to each other on the bottom row and then add a second row of logs that is perpendicular to the first row. Additional rows can be added as necessary, each perpendicular to the last, to achieve the desired change in height. Ensure that the top row of logs is perpendicular to the boardwalk stringers. A small gabion basket can also be used in place of an anchor sill. Sills, cribs and gabion baskets should never be located within a watercourse where they would interfere with the natural water flow patterns. Refer to Construction of Abutments for additional information about cribs and gabion baskets.
To install anchor sills:
Research in Alaska suggests that cellular containment panels can be used for trails in areas saturated with water (e.g., muskeg) [59]. The existing soil and organic material is not removed and the panels are placed on top of the existing terrain. The sills are mounted on top of the panels. The weight of the sills keeps the panels in place and, with time, vegetation will grow through the panels to restore a more natural appearance. Refer to Binding or Stabilization Materials for additional information on panel installation.
Anchor posts are used instead of sills when greater stability of the support structure is required. In Ontario, the use of anchor posts for the construction of trail tread structures is relatively unusual. Bedrock, sand and muskeg areas are just a few examples of the types of terrain that are not suitable for anchor posts. If anchor posts are to be used, engineering expertise should be obtained to determine the size, depth and location of anchor posts. Because of the complexity of installation, anchor posts are seldom installed by trail volunteers . The assistance of an experienced construction professional is recommended when anchor posts are required to support an elevated tread structure.
There are three types of anchor posts that are commonly used for trail tread structures:
Abutments are structures anchored into the terrain that support the stringers. Typically they are used to anchor a bridge when the banks are quite steep, or when the stringers need to be supported at a height off the ground. Permits will be required for any abutment construction that is in the vicinity of a body of water (e.g., creek). Depending on the ownership and management of the land and environmental factors, permits may be required from a number of different sources. The landowner should be able to provide the list of agencies and organizations that must be contacted regarding permits.
Constructing an abutment into an embankment makes it easier to construct the elevated tread at the same height as the surrounding terrain. However, construction on the banks of water bodies is extremely complex and can cause significant environmental damage if done in correctly. Professional expertise is required for the design and construction of abutments .
Cribs and gabion baskets are commonly used techniques for constructing abutments with volunteer labour. In both cases, a containment structure is built and then the structure is filled with rock to ensure its stability. In the case of gabion baskets, the containment structure is wire mesh [60]. For cribs, the containment structure is typically made of wood. Cribs are built with a series of layers, each perpendicular to the layers above and below. Engineering expertise is required to determine the location, size, materials, construction methods and anchoring systems for all abutments . The footing of abutments must be on ground that is solid and dry. Abutments on flat terrain can sit on compacted mineral soil. Abutments on steep terrain must be tied into the slope. Before constructing any type of abutment, the plans and details of the construction methods and timing must be approved by the local Conservation Authority and/or office of the Ministry of Natural Resources. Gabion and cribs should never be constructed within the water flow channel.
Just as it is important for each anchor to be level from side to side, it is equally important that adjacent anchors be relatively level to each other. If adjacent anchors differ significantly in height, the finished tread structure will be sloped and difficult to navigate. Sloped stringers can also be more difficult to stabilize.
Use a laser level or clinometer (refer to Appendix G for details) to determine the slope between adjacent anchors. If the slope is more than 4% (i.e., a height difference of more than 4 cm for every 1 metre of horizontal length or 1 inch for every 25 inches of horizontal length) the height of the lower anchor point should be increased.
To increase the height of the lower anchor point , complete the following steps:
Stringers are the long spans, parallel with the direction of trail travel, which connect adjacent anchors and support the tread . Typically, they are made of wood, either log or lumber. For some projects, steel beams may be used as stringers.
The length of a stringer should not exceed 5 metres (16 feet). That is, the distance spanned between adjacent anchors should be no more than 4 metres (13 feet) . If longer spans are required, professional expertise assistance should be obtained because the diameter and strength of the stringers will need to be carefully calculated.
The stringers are installed after the construction of adjacent anchors is complete. The installation of stringers is similar to the positioning of sills. The steps are:
Shimming with small pieces of wood is commonplace and effective. Since the wood pieces are elevated above the soil, they are not particularly prone to rot.
Decking is the term used for the walking surface of elevated tread structures. Typically, 2 x 4, 2 x 6 or 2 x 8 lumber is used for decking. Use rough sawn lumber for decking as it provides a tread with more "grip". Thicker lumber (3" or 4" boards) should be used if the distance between stringers is more than 0.75 metres (2.5 feet) or if heavier load bearing (e.g., equestrians, stock, motorized trail users) is required. Avoid the use of tree branches for decking because the rounded walking surface can be hazardous for many trail users. Plastic planks are also used by some trail organizations. However, they require additional support (i.e., more stringers placed closely together) and maintenance (to prevent the growth of algae that makes the surface very slippery), so the choice of this material must be carefully considered. Pressure treaded lumber can also be very slippery when wet so its use is not recommended for decking.
To install lumber decking:
The use of logs for decking is not appropriate except in very remote areas where lumber is not available. If logs must be used, the topside of each log should be "shaved" with a chain saw to create a flat surface for trail users to stand on. Spaces between the round log edges should be filled with compacted crushed rock, soil or wood chips so that trail users have a consistently firm, level and stable tread. Remember, putting soil or wood chips on top of the logs will encourage them to rot more quickly.
In areas where the decking will be almost continuously wet (e.g., in the spray from a waterfall or shoreline), expanded metal (flat, metal lattice or grid) or tensar netting [61] can be added to the top surface of the wood deck to make it less slippery under wet conditions. However, care must be taken to ensure that the metal or netting sits flat and tight on the wood surface . Even small sections of metal or netting that are not flat and tight to the wood surface can be a tripping hazard, particularly for children and people who use walking sticks, crutches or canes.
A key component of the design of elevated tread structures is that the parts are separated from contact with the ground to decrease the speed of rot in the wood components. Even though the top of the sill is relatively close to the ground (gap of at least 15 cm or 6 inches), the trail user walking on top of the elevated structure, which is mounted on stringers, will usually be elevated above the remaining trail surface by at least 0.5 metres. The approach structures at each end of the elevated tread enable trail users to navigate the difference in height between the two tread surfaces .
The design and construction of the approach is critical to ensuring that trail users of all abilities can access the elevated tread structure easily and safely. The approach structure should always provide a continuously ramped surface that smoothly connects the ground level and elevated tread surfaces. The slope up the ramp should not exceed 10%, and ramps below 5% slope are recommended. Steps onto the elevated surface can also be provided, and may be helpful to some trail users or if the height differential is substantial, but a ramped surface is always required . Ensuring ramped access will also discourage cyclists from by-passing the elevated tread when water levels are low, in order to avoid dismounting.
An approach structure is not required if the elevated tread structure is constructed on top of abutments that are excavated into the ground so that the elevated tread structure begins level with the ground level trail tread. The excavation and construction of these types of abutments is complex, and professional assistance is recommended.
The construction log will provide detailed information on the length and slope for the access ramp surfaces. Because the access ramps are typically designed to have the steepest acceptable grade, it is critically important that construction crews build the access ramps exactly as designed . Changing a ramp designed as 3 metres (10 feet) in length to be a ramp of 2.8 metres (9.2 feet) in length can mean the difference between a safe and accessible elevated tread and a trail that encourages trail users of different abilities to navigate an uncomfortable and potentially unsafe situation.
There are essentially two types of approach structures:
The construction log will specify the design to be used. The two types of structure are relatively similar. The primary difference is whether the elevated tread decking is extended onto the approach (and then earthen-gravel fill is used only for the final connection to the lower trail tread) or whether the entire approach surface is constructed from earthen-gravel fill. The following instructions are for a ramped approach structure . If an earthen-gravel fill approach is required, begin at Step #3.
The trail designer will determine the need for handrails based on a variety of factors, such as the height of the elevated tread above the surrounding terrain, the anticipated range of abilities among trail users and safety codes and regulations. The Ontario Building Code specifies that "guards" (i.e., railing, wall) are required if the walking surface is more than 60 cm (2 feet) above the surrounding ground surface [62]. Handrails are not required on trails because of changes in the grade of the trail. For example, if the grade on the trail exceeds 5% (1:20), handrails are not required on the trail. Trail designers must ensure that trail complies with all safety codes related to the provision of handrails. The trail designer may also require one or more railings in other situations, depending on what is required for the safety of trail users and to assist them in making a steady crossing.
There are a wide variety of handrail designs and materials that can be used. The choices made will depend on the aesthetics of the trail environment and required safety codes. Details of the size and design of handrails to be constructed will be provided by the trail designer in the construction log. Important points to keep in mind during the construction of handrails are:
Edge protection may be desirable on elevated tread structures that do not have handrails. Trail designers are not required to provide edge protection on elevated tread structures, except where required by local trail standards or safety regulations. Edge protection (also called a "bull rail") is often included on elevated tread structures that are used by horses. Handrails, rather than edge protection, are preferred for trails that permit cyclists.
If desired, edge protection can be constructed from either logs or lumber. If provided:
Docks and floating bridges are most commonly used on water trails (e.g., canoe or kayak routes). However, floating bridges can also be appropriate for crossing small bodies of water. The use of a floating bridge rather than an elevated tread structure must be determined in conjunction with the land managing organization. Permits will be required for all construction work because it occurs within a body of water . The local conservation authority should be contacted so that the proposed work can be reviewed and approved. The landowner should be able to provide the contact information for any additional agencies or organizations whose permission will be required.
The U.S. Forest Service has developed a good resource for the construction of floating trail bridges and docks [63]. It is available, free of charge, on the recreation trail resources web site of the U.S. Federal Highway Administration: http://wwwcf.fhwa.dot.gov/environment/rectrails/trailpub.htm.
The U.S. National Park Service has also recently published an excellent resource [64] on floating docks, launches and landings, which contains suggestions on how to design these facilities so that they are easier for people with disabilities to use. The design considerations recommended in that resource include:
Continuous contact tread structures are controversial in the trails community. Many people oppose the use of continuous contact tread structures because the design creates a continuous barrier that can substantially alter the natural drainage patterns of the trail environment. In general, the use of intermittent contact tread structures is recommended and the use of continuous contact structures should be limited to situations where intermittent contact structures are not feasible.
There is a wide variety of continuous contact tread structures that are used to build elevated trail tread. The terminology used to refer to these different types of structures also varies tremendously, based on the feedback received on the first draft of this resource. For the purposes of this resource, the following terms are used:
Choose construction materials carefully!
By design, the materials used for the construction of continuous contact elevated tread structures will be in "continuous contact" with the soils that occur naturally in the trail environment. This makes the materials more likely to rot, and increases the risk that contaminates from the materials will leach into the soil and impact the local habitat. Therefore, it is critically important that the construction materials used for these tread structures are carefully selected based on their potential impact on the environment as well as the safety of trail users. The use of rock or untreated types of wood that are less likely to rot (e.g., cedar) is strongly recommended . Refer to the Tread Structures Above the Surrounding Terrain section for additional information about the importance of material selection.
Always use safety equipment when cutting and using treated wood, such as gloves, glasses, and a dust mask .
The length, height, location and construction techniques for the causeway or turnpike will be determined by the trail designer. Factors such as environmental conditions, natural drainage patterns and trail user information will be combined to determine the type of elevated structure required. The location of causeways and turnpikes is critical to their success (or failure). Areas of very low or imperceptible water flow, or very intermittent drainage channels can easily be dammed by a causeway or turnpike that is constructed in the wrong location. Causeways and turnpikes should never be constructed in areas with visible, ground level water flow or areas with intermittent flooding . If construction crews arrive at the site and find evidence of surface water flow, construction should not begin until the plans for the elevated tread structure are reviewed.
Turnpike and causeway surfaces are long lasting, and low maintenance . Even if the sidewalls are constructed with logs, the rotted log will eventually be replaced by a duff berm that will still retain the drain rock and tread material. The crushed aggregate and other tread surface materials that can be used last longer and require less maintenance than wood plank surfaces. After the initial construction labour and expense, a turnpike will stay "high and dry" in all types of weather. Users will be able to travel through wet environments under enjoyable conditions without making a significant impact on the environment. The main drawbacks for turnpike or causeway use are the high potential for negative environmental impacts and the substantial amount of labour required during initial construction. Building a turnpike or causeway of any length requires an energetic trail crew that is not afraid of hard work.
The steps for constructing a turnpike or causeway are:
Corduroy is a technique that, in the past, was often used to construct a trail across wet terrain. Typically, it consisted of logs laid side-by-side across the tread, although some trail construction guides recommend that the logs be anchored together. However, corduroy is the source of many sustainability and access problems . The logs in corduroy will eventually rot and require replacement, increasing trail maintenance demands. Corduroy has a negative impact on healthy natural environments because of:
Trail users and wildlife are seldom comfortable walking on top of the corduroy. As a result, the environmental impact of trail use continues to increase as they go further and further off of the trail tread in order to find dry, firm and stable ground. For many trail users, stock and wildlife, trying to balance on corduroy, especially under wet conditions, can be dangerous. For all of these reasons, corduroy is not recommended .
The use of corduroy may be considered in very remote areas where other methods of elevated tread construction are not feasible. Corduroy may also be used on trails that are open for winter use only (e.g., cross country ski trails). If corduroy is used, the following methods of construction are essential:
A retaining wall is used to support the trail bench when the natural soil does not have the stability required for a trail tread. The retaining wall is built on the downhill side of the tread and then the trail bench is constructed between the retaining wall and the uphill slope. Some trail groups also use retaining walls to control sloughing of uphill material onto the trail tread. However, this is not recommended. Always construct the uphill slope so that it is at or below the angle of repose , this will allow the slope to naturally stabilize itself through re-vegetation. Retaining walls can also be used on very steep slopes, even if the natural soil is suitable for a trail tread. Constructing a retaining wall on the downhill side of a very steep slope decreases the size of the excavated trail bench and lowers the height of the back slope. For these reasons, retaining walls are often used to construct the landing of a switchback.
Retaining walls can be difficult to build and if the wall required will be more than 1 metre in height, experienced or professional help should be obtained . In general, the best option is to build the trail so that retaining walls are not required. The need for a retaining wall suggests that the natural soil or landform cannot support the trail tread . When that is the case, it invariably means much higher construction costs and more on-going trail maintenance. Before deciding to build a retaining wall, try to find a more suitable, alternative route for the trail.
Retaining walls can be built with a wide variety of materials, such as rocks, gabion baskets, logs, lumber, concrete and interlocking bricks. The choice of materials will depend on aesthetics, and the availability and suitability of materials in and for the trail environment. Building a safe and effective retaining wall involves more than just stacking materials . The slope of a retaining wall (the distance or angle that each row is set back on the previous row) should be determined by the steepness and stability of the slope as well as the performance characteristics of the material being used [66]. Design of the retaining wall must also consider drainage patterns, and how water will flow around and through the finished wall. When in doubt, seek professional advice.
The construction log will specify the materials to be used to construct the retaining wall. The materials are typically log, lumber, rock or interlocking stone. Once the drainage issues have been resolved, and the need for drainage pipes within the retaining wall has been determined, building a retaining wall will require the following steps:
When trails are located in steep terrain and the topography and available land will not allow the use of the more sustainable curvilinear trail alignment, a climbing turn or switchback may be required. Switchbacks and climbing turns allow a trail to reverse direction so that most of the tread can follow the natural contours of the terrain. A switchback will have a relatively level turning area. This ensures that trail users do not have to negotiate the fall line of the hill while on a steep slope. A climbing turn does not have one turning area, but gradually climbs and changes direction throughout the turn. Since trail users will be on a slope on the fall line in a climbing turn, climbing turns are best suited to gentler slopes.
Climbing turns and switchbacks must be built with the utmost care . Whenever trail users can see that the trail abruptly reverses direction, there will be an almost irresistible temptation to "short cut". Trail users going off the trail tread to take a shorter route will significantly impact vegetation and drainage patterns in the trail environment. Damage or removal of vegetation leaves the underlying soil, which is not compacted to be a trail tread, at high risk for erosion. Great care must be taken to camouflage the adjacent sections of trail so they are not visible to trail users until they virtually arrive at the turn. Installing handrails at knee and torso height on the trail tread as it approaches the switchback landing from uphill can be an effective method of encouraging trail users to follow the tread through the switchback. In some types of terrain, vegetation or natural rock outcroppings can also be used to camouflage the adjacent sections of trail tread.
To construct a climbing turn or switchback, perform the following steps:
After the trail route has been cleared, construction of the trail surface can begin. If the tread is to be the naturally occurring ground surface, it must be firm, stable, resistant to erosion and dry . Soils that contain small pieces of fractured rock (i.e., rock matrix with a variety of sizes of rock pieces) generally provide the most sustainable tread. If the trail alignment is optimal but the natural soils are not suitable, the use of tread stabilization techniques (e.g., soil hardening) or a constructed tread (e.g., boardwalk) will be required. It is inappropriate to construct the trail tread on sub-standard soils that cannot provide a sustainable tread .
Soil types change dramatically throughout every landscape. The trail designer will have considered the naturally occurring ground surface in making the tread material and construction decisions specified in the construction log. Good trail design will locate the trail on the most sustainable soils with appropriate grades , thus minimizing potential erosion. If substantial tread construction is specified in the construction log, it reflects the fact that the optimal trail alignment must cross an area with poor quality natural soils. The constructed tread provides a "structural solution" to the poor quality of the natural soil. The trail construction person needs to always "read the ground" for changes of soil type that may have been missed in the trail design phase . Construction crews should not alter the trail tread work specified in the construction log. If sub-standard soils are encountered during construction, the work should stop until the issue can be re-considered from a design perspective (i.e., consideration of a change in the trail alignment).
To determine if the naturally occurring soil is not suitable for constructing a sustainable tread:
Building trail tread is often "back-breaking" work. Natural environments rely on delicate patterns of water movement. Trails are not a part of the natural environment, and even the most sustainable trails will alter the natural patterns of water movement. It is almost impossible to underestimate the importance of maintaining natural drainage patterns both during trail construction and on-going trail use. Sustainable trails often require more work to construct, because they pull in and out of every natural drainage channel. However, this work is necessary to ensure that the impact of the tread on the natural drainage patterns is minimized, the tread will have the proper outslope for good drainage, and it will be level enough for safe and comfortable use.
The specific steps for constructing the trail tread will vary, depending on the quality of the natural soils, the terrain, and the type of tread material. In general, the steps will be:
Each of the steps used to create a natural surface trail is described in detail in the following sub-sections. Information on constructing hardened or constructed trail surfaces is provided in the section titled Constructed Trail Surfaces.
To prepare the ground for a natural surface tread:
The bench refers to the land on which the tread material rests. A "full bench tread" is one that is constructed by cutting the full width of the trail tread into the hillside. Although many people believe that "cutting a bench" is damaging to the trail environment, in fact a full bench tread provides the most sustainable design. Properly constructed, a full bench tread should last "forever" with virtually no maintenance .
A "partial bench&quo