| [Image: Examples of BMPs installed along a road] |
| [Image: Culvert] |
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A forest road system is made up of permanent and temporary roads that connect the forestland to existing public roads. They provide forest access for such activities as land management, fire protection, recreation and timber harvesting. Forest roads that are improperly located, poorly constructed and/or not maintained are the largest contributor of nonpoint source pollution from forest activities. Roads on steep slopes, erodible soils or stream crossings hold the greatest potential for degrading water quality. In wetlands, forest roads must comply with 15 mandatory BMPs. See the Forest Wetlands section of this Web site for information regarding mandatory BMPs in wetlands.
BMPs for Location & Planning
- Use of tools such as soil surveys, topographic maps and aerial photographs can help achieve the most practical road construction results.
- Design a permanent road system to meet long-range objectives rather than simply to access individual sites. Numerous separate road projects have more environmental impact than one well-designed road system.
- Stabilize or reconstruct existing roads where significant erosion problems exist. Abandon and retire roads where repair is impractical.
- Safety should always be considered with road design and location of intersections and access points to public roads.
- Minimize the number of stream crossings.
- Cross streams on straight segments and as close to a right angle as possible (see video).
- Locate roads on the best available sites, avoiding excessive slope.
- All suitable excavated material should be used for the construction of the road, when possible. This may include soil removed from ditches during construction or maintenance.
- Avoid the following:
- Using streamside management zones (SMZs) for road locations or traffic areas.
- Locating roads adjacent to SMZs.
- Locating roads where water tends to collect.
BMPs for Construction
- Salvage merchantable timber prior to clearing the right-of-way.
- Stumps, logs, slash and other organic debris should not be covered with fill material and incorporated into roadbeds unless the corduroy road construction technique is used.
- Minimize the amount of soil on the road banks or roadsides that is exposed to soil erosion. To minimize problems, revegetate or otherwise stabilize these areas as they are created.
- Functional water diversion structures should be installed at the same time roads are constructed. Drainage water should be dispersed onto the undisturbed forest floor when possible. Soil from parallel and lateral ditches may be incorporated as material for the roadbed and drainage structure.
- Road bank slopes should be a 2:1 ratio. Seeding, mulching or other stabilizing means should be used to reduce the potential for erosion.
- Plan for periods of heavy rain during road construction by including temporary waterbars, turnouts or other structures to slow water runoff.
BMPs for Drainage
- Ditches, culverts, dips and wing (lateral) ditches should be installed at the time of construction of the roadway. Ditches should be adequately sized and sloped to prevent silting-up and to allow for maintenance-equipment access.
- Roads should be designed to drain at all times by using crowning, ditching, culverts and water bars.
- Ensure that culverts, water turnouts and broad-based dips empty road runoff onto the undisturbed forest floor.
- All culverts, permanent or temporary, should be of adequate size to carry the water flow anticipated during heavy rains. (See CULVERT SIZE CHART).
BMPs for Water Crossings
- Stream crossings should be constructed to minimize the disturbance to stream banks and existing stream channels.
- Use of equipment in the streambed should be kept to an absolute minimum.
- Crossing streams at fords should take place when stream flow is down and threat of sedimentation is low.
- Fills and earth embankments used as bridge approaches should be stabilized to minimize potential erosion by using headwalls, wing walls, rip-rap and other suitable material.
- Excess material and woody debris from road construction should be cleared from streams and drainage ways.
- Bridges and culverts should not constrict clearly defined stream channels.
Some of the most common mistakes in road construction and maintenance are as shown below.
AVOID
- Improperly sized culverts (too small).
- Poor location (wet spot, loose soil).
- Insufficient number of wing ditches.
- Steep hills (more than 10 percent grade).
- Use of fill material taken from SMZ to cover culvert.
- Improperly maintained road crown.
- Plugged culverts.
- Leaving erodible soils stabilized.
- Leaving ditches clogged with logging debris.
- Inadequate soil compaction or "set-up" time before heavy use.
NOTE: Proper maintenance of permanent access roads is of vital importance to logging and land management activities. Road systems should be kept in serviceable condition to minimize erosion by rainfall runoff and vehicle use.
BMPs for Road Maintenance
- The road surface should be crowned or outsloped to dissipate surface runoff and minimize erosion of the roadbed.
- Ditches, wing ditches, and culverts should be kept free of logging debris or other obstructions to allow unrestricted passage of water. Siltation should be removed from ditches and wing ditches through periodic maintenance.
- Exposed soil subject to excessive erosion should be revegetated or otherwise stabilized if natural revegetation will not suffice.
- Trees adjacent to permanent roads should be trimmed or cut back to allow maximum sunlight on the road surface.
- Closed roads should be periodically inspected to ensure their integrity.
- Anticipate weak spots in roadbed and repair with support materials. Do not excavate the road surface and create a channel.
Exemption for Roads in Wetlands
Road construction for silvicultural purposes in jurisdictional wetlands does not require a permit because of this silvicultural exemption. However, to qualify for silvicultural exemption, the road construction must comply with 15 mandatory BMPs for forested wetlands (from Clean Water Act, Section 404 Program Definition and Permit Exemption, Part 232.3).