
560 - 1 NATURAL RESOURCES CONSERVATION SERVICE CONSERVATION PRACTICE STANDARD ACCESS ROAD (Feet) CODE 560 DEFINITION Planned work shall comply with all federal, state and local laws and regulations. A travel-way for equipment and vehicles constructed as part of a conservation plan. Where general public use is anticipated, roads shall be designed to meet applicable federal, state and local criteria. PURPOSE Location. Construct roads to facilitate the To provide a fixed route for vehicular travel control and disposal of surface and for resource activities involving the subsurface water, control or reduce erosion, management of timber, livestock, agriculture, utilize topographic features where feasible, wildlife habitat, and other conservation and include scenic vistas where possible. enterprises while protecting the soil, water, Construct roads to follow natural contours air, fish, wildlife, and other adjacent natural and slopes to minimize disturbance of resources. drainage patterns. Locate roads where they can be maintained and water management CONDITIONS WHERE PRACTICE problems are not created. To reduce APPLIES potential pollution, locate roads away from watercourses and utilize buffers where Where access is needed from a private or possible to protect waterbodies. public road or highway to a land use enterprise or conservation measure, or Alignment. Adapt gradient and horizontal where travel ways are needed in a planned alignment to intensity of use, mode of travel, land use area. equipment type, load weights, and level of development. Access roads range from seasonal use roads, designed for low speed and rough For stream crossings, align roads so it driving conditions, to all-weather roads crosses perpendicular to the channel. heavily used by the public and designed with Grades shall not exceed 10 percent except safety as a high priority. Some roads are for short lengths of up to 50 feet. Maximum only constructed for a single purpose; i.e. grades of 18 percent should only be control of forest fires, logging and forest exceeded if necessary for special uses such management activities, access to remote as logging roads, field access roads, fire recreation areas, or access for maintenance protection roads or other roads not of facilities. accessible for use by the general public. A water control mechanism is required CRITERIA immediately above steep grades.. Roads can be located diagonally across the slope, only Design access roads to serve the planned when necessary to stay within maximum use with the expected frequency of vehicular allowable grades. or equipment traffic. Consider conditions under which vehicles and equipment are Width. For one-way traffic, the minimum expected to operate, such as vehicle or width of the roadbed is 14 feet; for two-way equipment type, speed, loads, soil, and traffic the minimum width is 20 feet. The climate. roadbed width includes a tread-width of 10 Conservation practice standards are reviewed periodically, and updated if needed. To obtain NRCS-RI the current version of this standard, contact the Natural Resources Conservation Service February, 2010 Rhode Island State Office or download it from the Rhode Island electronic Field Office Technical Guide (eFOTG). 560 - 2 feet for one-way traffic or 16 feet for two-way Drainage. Drainage structures shall be traffic. Each type of road also requires 2 feet chosen to accommodate the intended use of shoulder width on each side. Single-lane and runoff conditions. Culverts, bridges, logging or special-purpose roads can have a fords, or grade dips for water management minimum width of 10 feet, with greater widths shall be provided at all natural drainage ways at curves and turnouts. The two-way traffic and shall be designed in accordance to width shall be increased approximately 4 feet Rhode Island Conservation Practice for trailer traffic. The shoulder width may be Standard Stream Crossing, code 587. The either gravel or grass. minimum capacity of a culvert or bridge in Turnouts shall be used on single lane roads drainage way shall convey the design storm where vehicles travel in both directions on a runoff without causing erosion or road limited basis. Where turnouts are used, road overtopping. Table 1 lists minimum design width shall be increased to a minimum of 20 storm frequencies for various road types. feet for a distance of at least 30 feet. Table 1. Turnouts shall be spaced every 200 to 500 Minimum Design Storm Frequencies for feet. Where sight distances exceed 1000 Various Road Types feet, turnouts may be spaced at 1000 feet. Road Type Storm Frequency Turnarounds shall be used at the end of dead roads. Turnarounds may also be Forest Access Roads, 2 year- 24 Hour desirable for stream, lake, recreation, or Farm Field Access Roads other access purposes. The minimum radius of curvature of centerline for turn arounds Farm Driveways, 10 year-24 Hour and curves shall be 40 feet for cars only and Recreation Facility 50 feet for cars with trailers up to 30 feet Access Roads long. Public Access Roads, 25 year – 24 Hour For agricultural access roads, minimum Campgrounds, Etc. widths of 12 feet are acceptable on tangents with fairly level sections without appreciable depth of cut or fill. Minimum widths of 14 feet An erosion-resistant low point or overflow shall be used on all curves, side hill sections area may be constructed across the access or areas of substantial cut or fill. Sufficient road to supplement culvert capacity on non- side clearance shall be allowed for clear public use roads. Install culverts, bridges, passage of trucks along the finished road. fords and hardened overflow areas to avoid Generally, a minimum of two feet of cleared significant impact of fish migration. area is to be maintained from the edge of the Roadside ditches shall be adequate to graded surface. provide surface drainage for the roadway Side Slopes. All cuts and fills shall be and contributing area, and maintain the designed to have stable slopes of a minimum proper depth to serve as outlets for of 2 horizontal to 1 vertical on heights of less subsurface drainage. At a minimum, the than 4 feet. For short lengths, rock areas, or roadside ditch shall be 1.0 foot below the top very steep hillsides, steeper slopes may be of the road surface to provide internal permitted, only if soil conditions warrant or drainage. Ditch channels shall be designed special stabilization measures are installed. to be on stable grades or protected with structures or linings for stability. Avoid areas with geological conditions prone to sliding or slope instability. When such Water-breaks or water-bars may be used to sites are to be used provide treatment to control surface runoff on low-intensity use ensure slope stability. Allowable treatments forest, ranch or similar roads. Consider include but are not limited to regrading slope, water bars on steep grades where runoff and installing turf-reinforcement mats, or erosion is anticipated down the road. placement of gabion wire-mesh baskets. Construct water bars with materials compatible with the use and maintenance of the road surface. Water bar discharge areas NRCS-RI February, 2010 560 - 3 must be well vegetated or have other erosion To prevent damage or hazardous conditions resistant materials. See Figure 1. during adverse climatic conditions, consider Recommended Spacing of Relief Culverts controlled access on unsurfaced roads. and Water Bars Based on Soil Type. Toxic and acid-forming materials shall not be Provide roadbed drainage at all seep areas used on roads. This is not to be construed to and high water table areas. The depth, prohibit use of chemicals for dust control and spacing, outlets, and size of roadbed drains snow and ice removal after considering must keep the water table at least 24 inches potential impacts on stabilizing vegetation. below the surface. Utilize additional conservation practices to Use surface crowning to help direct road reduce the potential for generation and runoff into the side drainage ditches. Crown transport of particulate matter emissions. the centerline of the access road at least 3 Construction Operations. Construction inches higher than the shoulder or grade operations should be carried out in such a from one side of the road to the other on a manner that air and water pollution and single uniform slope. Flow into the ditches erosion are minimized and held within legal must remain unobstructed to prevent limits. Construction shall include the roadside erosion. following requirements as necessary for the Surfacing. Provide surface treatment on job: access roads as required by traffic needs, 1. Trees, stumps, roots, brush, weeds, and soil, climate, erosion control, or particulate other objectionable material shall be matter emission control. Treatment type removed from the work area. depends on local conditions, available materials, and the existing road base. If 2. Removal of unsuitable material from the these factors or volume of traffic pose no roadbed area. problem, special treatment of the surface is 3. Grading, sub-grade preparation, and not required. For weak bearing capacity compaction shall be done as needed. soils such as silts, organics, and clays, the surface treatment should be underlain with 4. Surfacing shall be done as needed. geotextile material specifically designed for 5. Limit the generation of particulate matter road stabilization applications when the road during construction. is used on a regular basis. Figure 1. Recommended Spacing of Relief Culverts and Water Bars Based on Soil Types 450 400 Granular Soils 350 (Gravel) 300 250 200 150 Spacing (feet) 100 Sands, Silts & Clay Soils 50 0 0 2 4 6 8 10 12 14 16 18 20 Road Grade (%) NRCS-RI February, 2010 560 - 4 Traffic Safety. Provide passing lanes, CONSIDERATIONS turnouts, guardrails, signs, and other Consider visual resources and facilities as needed for safe traffic flow. environmental values during the planning Traffic safety shall be a prime factor in and designing of the road system.
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