«Countywide Park Trails Plan THE MARYLAND-NATIONAL CAPITAL PARK AND PLANNING COMMISSION Montgomery County Department of Parks Park Planning and ...»
Appendix C Sensitivity to Significant Environmental Features: Planning, Designing and Constructing Hard Surface Trails in M-NCPPC Parks M-NCPPC follows the tiered approach described below during the trail planning, design and construction processes to avoid, minimize and mitigate potential negative environmental effects of a trail proposed in a certain corridor. This approach follows M-NCPPC and county policies, and local, state and federal regulations. In fact, trail development in Montgomery County Parks often goes above and beyond what is required by regulations. M-NCPPC takes its role of steward for the natural resources on parkland on behalf of the citizens of Montgomery County seriously.
Therefore, M-NCPPC tries to make every reasonable effort to use best management practices and state-of-the-art techniques and technologies in trail design and construction in order to balance the need for environmental sensitivity and protection and the recreation and transportation needs of County residents.
The tiered approach starts with the following question:
Can a trail be located within a stream valley associated areas of significant environmental features?
If YES, proceed with trail planning and identify preliminary trail alignments outside stream valley buffer;
If NO, explore the following alternatives within the corridor.
a. Is it possible to marginally expand existing park boundaries to include less sensitive areas for trail location?
EXAMPLE: The Countywide Park Trails Plan proposes this approach in the Rachel Carson Greenway Corridor where the Plan recommends expanding “the Northwest Branch stream valley park boundaries to accommodate the trail while minimizing environmental impacts.” (See Figure09) The Plan states: This approach means construction of a hard surface trail would await redevelopment of a [nearby] golf course. However, this is an appropriate tradeoff given the opportunity to protect a highly sensitive environmental area, which deserves a high level of protection.
b. Is it feasible to acquire a significant amount of new parkland to accommodate a trail?
EXAMPLE: The Countywide Park Trails Plan proposes a trail connection from the Magruder Branch stream valley system to the North Germantown Greenbelt. Although there is already parkland in the area (the Seneca Greenway) the Plan states “opportunities for a hard surface trail in this portion of the Seneca Greenway may be limited due to topography, and the
relatively narrow width of the Great Seneca Extension at this location.” The Plan continues:
For this reason, the Plan suggests an alternative hard surface trail connection be studied which avoids the Great Seneca stream valley. (See Figure 08)
Figure C.1: Example of New Trail Corridor to Avoid Sensitive Features c. Could a non-park bikeway system eliminate the need for a hard surface trail within the park?
The Clarksburg Greenway Study, which refines the hard surface trail system for the upcounty, notes that in portions of the Little Seneca Greenway, “it is recommended that part of the hard surface trail be located along a roadway rather than impact steep slopes and wetlands.” The Study notes that when portions of the hard surface greenway trail network relies on bike paths, “a special cross-section is needed to assure the bike path has a park-like character…,” shown in the Clarksburg Greenway Study, illustrates how a bike path along a road can be located in a park-like setting through the use of plantings and by making the path horizontally and vertically separate from the road.
Figure C.2: How a Bike path Along a Road Can Be Located in a Park Setting
APPENDICES – COUNTYWIDE PARK TRAILS PLAN 2004 UPDATE
If alternatives A-C are found to be infeasible, use these other alternatives:
a. Minimize total environmental impact within the portions of the buffers that cannot be avoided.
EXAMPLE: In some cases, trails may take advantage of already disturbed areas—such as cleared rights-of-way for sewer lines. These rights-of-way are often placed within the stream buffer to accommodate gravity flow for the sewer line. Although priority would be given to reforesting these, a trail might be allowed if especially sensitive areas are avoided. The Magruder Branch Stream Valley Park boardwalk trail is an example of coordinating trail construction with sewer line construction. A similar approach will be used for a portion of the Clarksburg Greenway Trail where WSSC has already cleared a swath of land in the stream valley (See Figure Ap-4). There are several other examples of trails within utility corridors. Parts of Sligo Creek Trail follow a WSSC sewer line. In addition, portions of the Northwest Branch Trail and trails within Black Hill Regional Park fall within previously cleared utility corridors.
b. Use environmentally sensitive design and construction techniques.
During trail facility planning, design, and construction, M-NCPPC staff and consultants look for ways to provide a safe and high quality trail user experience while minimizing negative environmental impacts. Avoid, minimize, and mitigate environmental damage is always the order of addressing sensitive areas. As trail design and construction has become a more specialized field over the last decade or so, new technologies and techniques have been and continue to be developed for more “environmentally friendly” trails. Staff will be developing a Trail Implementation Guide that will be a technical supplement to the Countywide Park Trails Plan. The Guide will recommend and may require some of these types of techniques and technologies.
Examples of Environmentally Sensitive Design Techniques Include:
1. Design of trail alignments:
Alignments should follow natural topographic contours to minimize erosion, and design around or minimize crossings of the most environmentally sensitive areas. These guidelines have been utilized in planning the Rachel Carson Conservation Park Trail System and new Black Hill and Ridge Road Park Trails.
2. Use alternative surfaces to asphalt:
Several materials have been developed to provide a firm and stable surface with a more natural look. A soil stabilizer made of natural tree resin has been mixed with soil and installed in a test section of the Northwest Branch Trail.
3. Use helical piers for boardwalks and bridges:
These piers cause less environmental disturbance than concrete or wooden piers, and can be installed with a portable generator causing less construction impact. They have been used on a boardwalk on a Sligo Creek Trail connector, and as the foundation for a bridge of the new Percheron Trail in the Agricultural History Farm Park.
4. Trail Safety:
Widen trail at steep slopes and curves to increase safety without widening the entire trail. This is being done on the rock Creek Trail Extension.
5. Use tree protection techniques to limit disturbance to trees near trail:
These include air-blasting technology to expose and analyze the root structure, clean-cutting tree roots by hand during construction, aeration of roots, and maintaining tight limits of disturbance for construction equipment.
6. Use new, lighter weight materials where possible:
Bridge components made of an advanced composite material with fiberglass reinforcement will be used for small bridges on the Northwest Branch Trail. Lighter but strong materials can be brought on site by smaller vehicles, or hand carried.
7. Use smaller construction machinery:
Smaller construction vehicles to exist; the California-based SWECO Company makes a 4” wide paver. However, smaller machinery, and contractors experienced with them, may not be as readily available, and may increase costs due to the increased time and effort involved.
8. Use small modular construction or end-on construction:
Especially applicable to boardwalk-type facilities, trail sections can be built piece by piece, limiting the area of construction disturbance to the section already constructed. More research is necessary for the application of this technique.
APPENDICES – COUNTYWIDE PARK TRAILS PLAN 2004 UPDATE
Mitigate for negative environmental impacts caused by the trail.
Trail projects can include a wide array of mitigation techniques for trail impacts, as required by permitting agencies. They will serve to improve the general conditions of the corridor’s environment.
These can be done within the trail corridor or elsewhere
1. Storm water management facility improvements or construction:
The Rock Creek Extension will improve an existing storm water management pond to help control the quantity of storm water runoff from the trail and other nearby facilities.
2. Stream restoration:
Some of the riprap and other stream restoration in Sligo Creek were constructed in part as mitigation for the Sligo Creek Trail Extension. The riprap helps control erosion, thereby improving the water quality.
3. Vernal pool construction:
These were constructed as part of the Magruder Branch Trail project. These pools provide habitat for creatures such as salamanders.
Environmental Improvements for Conditions Not Caused By Trail:
Trail projects can and do include tasks that improve some environmental damage that had been caused by sources other than the trail. In addition, trails provide some long-term positive impacts to the environment by providing access to natural areas so that citizens can develop a public appreciation of nature, and by educating the public regarding environmental issues through interpretive signage, brochures and programs.
1. Clean up of accumulated trash and old dumps within a trail corridor. Old cars and large appliances litter the undeveloped areas of the park system.
2. Stream restoration along tributaries in the trial corridor, which have been incised by storm water runoff from development outside of parklands.
3. Wetland creation or enhancement.
4. Reforestation / forest enhancement.
5. Removal of invasive exotic plans.
6. Creation of wildflower gardens using plants to attract native birds or butterflies.
7. Provision of wildlife corridors, such as underpasses under major roads, wide enough to serve trail users and wildlife.
Appendix D Natural Surface Trail Planning Guidelines Process and Design The natural surface trail planning process is shown in Figure 08.
The following objectives and principles help guide the natural surface trail planning process:
a. To seek trail alignments that avoid environmentally sensitive areas and sensitive archaeological and historical features. Evaluating environmental conditions during the trail planning process is essential to address park and open-space protection and the stewardship of natural, archaeological and historical resources.
b. To recognize that hiking is a legitimate form of recreation and transportation on natural surface trails when and where it is practiced in an environmentally sound and socially responsible manner.
c. To recognize that horseback riding is a legitimate form of recreation and transportation on natural surface trails when and where it is practiced in an environmentally sound and socially responsible manner.
d. To recognize that bicycling is a legitimate form of recreation and transportation on natural surface trails when and where it is practiced in an environmentally sound and socially responsible manner.
e. To recognize that not all natural surface trails should be open to equestrian and/or bicycle use.
f. To provide geographic parity in natural surface trail use opportunities for hikers, equestrians and bicyclists across the park system.
g. To seek trail alignments that are compatible with adjacent land-use and connecting trails.
h. To incorporate features for user enjoyment, e.g., loop trails, scenic destinations and picnic areas i. To create joint projects to educate all trail users.
j. To encourage communication between park staff, natural surface trail user groups and the environmental community.
Categories of Natural Surface Trails Natural surface trails are enjoyed by people on foot, people on horseback and people on hybrid bicycles. An important planning issue relating to natural surface trails is what user groups should be
accommodated on any given trail. The trail use categories for natural surface trails are:
Single Use, Hiking Only.
Hiking trails may be located in environmentally sensitive areas that are considered too fragile for bicycle or equestrian use or traverse terrain that is very rugged.
Shared Use by All These trails are open to hikers, equestrians and cyclists.
Shared Use by Some.
These trails are open to hikers and equestrians or hikers and cyclists.
APPENDICES – COUNTYWIDE PARK TRAILS PLAN 2004 UPDATE
In special situations, trails may have a Special Focus. These are trails designed with a specific user group in mind. Equestrian trails intended to accommodate trail riding groups or to allow jumping or faster gaits, for example, should be designed and built to a higher trail standard. Trails for mountain bikers seeking a high degree of challenge and obstacles require careful planning. Interpretive trails for groups would involve higher standards in terms of trail width and access.
Determining Whether a Natural Surface Trail Should Be Shared Use Shared use trails are beneficial as they direct users to one trail alignment and eliminate the need to provide multiple parallel trails for each user group.
However, when the Department of Park and Planning reviews suitability of a natural surface trail for equestrian or bicycle use, equestrian or bicycle use should not be allowed where it would cause the following measurable effects. This list is not all-inclusive.
a. Significant soil erosion or significant damage to streams or palustrine wetlands.