605B7600015 MPS Trail Spec Matrix (190528) (1).pdf
PDF 366 KB Posted
- Attached to
- Trail Ph 2 - Construction at Gathland State Park
- Solicitation number
- BPM059258
- Issued by
- Washington County, Maryland
About this file
This document is a specification matrix for natural surface trail construction standards established by the Maryland Department of Natural Resources (DNR) for use in state park projects. The matrix provides detailed technical specifications for three trail difficulty classifications—Easier (Green), More Difficult (Blue), and Very Difficult (Black)—to guide the construction of a second phase battlefield interpretation trail at Crampton's Gap/Gathland State Park near Burkittsville, Maryland. The project encompasses approximately 5,150 linear feet of new natural surface singletrack trail construction designed for pedestrian use only, with no motorized access permitted. The specifications establish baseline standards for constructed tread width, average trail grade, maximum grade, minimum turn radius, corridor width and height, exposure limitations, obstacle parameters, and surface roughness across the three difficulty levels, while acknowledging that landscape conditions may necessitate exceptions requiring consultation with the project manager.
The specification matrix emphasizes sustainability principles as the foundation for all design and construction decisions, incorporating features such as grade reversals at least every 100 feet, minimum three percent grade and camber for drainage, and terrain-modification techniques such as "lift and tilt" construction to ensure proper water drainage regardless of local conditions. The Green trail classification requires significant terrain modification with firm surfaces and minimal obstacles, while Blue trails anticipate modest rough tread with occasional unavoidable obstacles, and Black trails accommodate significant unavoidable obstacles including steps, terraces, rock gardens, and extended exposure. All specifications account for soil quality variations, with the matrix noting that high-quality clay-based soils with rock are assumed, while lower-quality sandy soils would necessitate grade reductions. The guidelines establish specific measurements for obstacle avoidance, turnpad grades, and corridor dimensions to balance user safety with sustainable trail design practices.
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Other files
| File | Type | Posted |
|---|---|---|
| 605B7600015 19-SF-GA01_FINAL APPROVAL SCANNED.pdf | ||
| 605B7600015 IFB 10.9.26.docx | DOCX document |
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Text version
Maryland Park Service Natural Surface Trail Specifications Matrix1
Easier (Green) More Difficult (Blue) Very Difficult (Black)
Constructed Tread Width
(typical)2
36 30" 18"
Ave Trail Grade per 1000'
5% 7% 10%
Max Trail Grade3, 4 15% 20% 30% (armored over 20%)
Min Turn Radius5 10' 8' 6'
Max Turnpad Grade6 5% 15% 15%
Corridor Width
(4' above tread)
48"-72" 36"-72" 36"-48"
Corridor Height (typical) 8' (humans) / 10' (horses) 8' (humans) / 10' (horses) 8' (humans) / 10' (horses)
Exposure (direct, without railing)7 less then 18" less then 48" no limit
Unavoidable Obstacles less then 2" less then 8" less then 18"
Avoidable Obstacles (over 50% of tread or less) less then 6" less then 24" less then 36"
Roughasity (surface texture)8 low med, some high high, some very high
Tread and trail features Firm trail surface. Any rock armored sections are constructed to have minimal height variation.
Modest rough tread (relative to local landscape) and occasional unavoidable obstacles are expected.
Significant unavoidable obstacles are expected. May include steps, terraces, extended rock gardens, loose rock, significantly exposure.
Notes Expect to significantly modify local terrain to meet trail specs; removing rock, avoiding tree species with surface root systems.
Seek out rocky ridges. Selective machine work to create a defined but organic appearing tread. Most rock and tread work is aimed at sustainability and definition rather than ease of passage.
Footnotes…
General Notes!
1. Matrix establishes a general baseline. It is understood landscape conditions may dictate exceptions. Consult with project manager for specific situations.
2. Constructed tread width may narrow over short distances to 50% of spec. Examples include rock or tree gateways.
3. Max grades refer to extremely short segments, approximately 20 feet.
4. Listed grades assume high-quality clay-based soil with rock. Lower quality sandy soils will reduce value.
7. Additional exposure may be acceptable via widening tread to permit timid users to escape.
• Grade reversals are required in all trails, at least every 100 feet.
• All trails should have a minimum grade and camber (in/outslope) of 3% to ensure a well-drained tread.
• Trails are required to have a cambered tread and drain regardless of local terrain. In flat areas this may necessitate a "lift and tilt" or other terrain-modifying construction technique.
5. Unless constrained by landscape elements, turns should maintain a consistent radius.
6. Turnpad grade measures the rise/fall across the turning surface at the base of any inslope.
8. Roughasity attempts to capture average tread coarseness. Tread area with obstacles: "low" = less then 5%, "med" = less then
20%, "high" = over 20%, "very high" = over 50%.
• Sustainable trails guidelines provide the foundation for all design + construction decisions ("half rule", frequent grade reversals, max grades function of soils + use, etc.).
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