Once clearing limits and road design features are staked out, road construction begins. Timber is cut and logs and vegetation are removed and piled along the lower side of the right-of-way.
Excavations efficiently dig, swing, and deposit material with accuracy and care. Slumps and other vegetative debris are swept clean from the new road surface and promptly disposed of in burn pits.
While pioneering, temporary crossings are used to get beyond a stream and continue clearing. Several logs, placed in the stream channel, form a base that water can flow through while protecting stream banks. This is replaced promptly with a permanent crossing.
Forest roads are often built by excavating the road surface out of a hillside. A bulldozer starts at the top of the cut slope, excavating and side-casting material until the desired road width is obtained.
An experienced bulldozer operator can do many road construction tasks, including drainage features. The inside-ditch and catch basin, formed just below the culvert inlet, prevents ditch water from bypassing the culvert.
Following up the bulldozer is a grader, providing the final smoothing of the road surface and shaping of inside ditches and drainage features.
Grass seeding raw, exposed cut and fill surfaces is an important erosion control practice. Exact seed mixtures, proper timing, and fertilizers and mulch are important for success (consult with experts).
Seeding stabilizes soil, prevents erosion, and indicates landowner's concern for potential erosion.
Control erosion during the construction process:
Design roads to balance cuts and fills or use full bench construction where stable fill construction is not possible.
- Construct roads in a manner that prevents debris, overburden, and excess materials from entering streams. Deposit excess materials outside of stream protection zones.
- Construct roads to comply with FPA plan and design guidelines.
- Provide for quarry drainage, to prevent sediment from entering streams.
- Clear drainage ways of all debris, generated during construction or maintenance, that may interfere with drainage or impact water quality.
- When constructing road fills near streams, compact the material to settle it, reduce erosion, and reduce water entry into fill. Minimize snow, ice, frozen soil, necessary to add and woody debris buried in embankments. Limited slash culverts for improved drainage. Anticipating and debris may be windrowed along the toe of the fill to the need for additional provide a filter near stream crossings.
- Construct road stream crossings or roads constricting upon a stream channel in compliance with the Stream Channel Alteration Law, Title 42, Chapter 38, Idaho Code.
- Stabilize slopes:
- Where exposed material (Excavation, embankment, waste piles, etc.) is erodible and may enter streams, stabilize it before fall or spring runoff by seeding, compacting, riprapping benching, mulching, or other suitable means.
- Retain outslope drainage during or following operations and remove outside edge berms except those protecting road fills.
- Construct cross drains and relief culverts to prevent erosion. Minimize construction and installation time. Use rip rap, vegetation matter, down spouts, or similar devices to prevent erosion of fills. Install drainage structures on uncompleted roads before fall or spring runoff.
- Install relief culverts with a minimum draingrade of 2 percent.
Considerations for borrow pits and overburden disposal:
Most forest roads are built by excavating a road surface. Road design and layout on-the-ground show machine operators the proper cut slopes and indicate cut slope steepness. The bulldozer starts at the top of the cut slope, excavating and sidecasting material until the desired road grade and width is obtained. Material from cuts is often pushed or "drifted" in front of the blade to areas where fill is needed. Road fill is used to cover culverts and build up flat areas. Since fill must support traffic, it needs to be spread and compacted in layers to develop strength.
- Minimize sediment production from borrow pits and gravel sources through proper location, development and reclamation.
- Place debris, overburden, and other waste materials associated with construction and maintenance activities in a location to avoid entry into streams. Include these waste areas in soil stabilization planning for the road.
While cut-and-fill road construction is common for gentle terrain, full-bench roads are usually built on slopes over 65 percent. In full-bench construction, the entire road surface is excavated into the hill. The excavated material is pushed or hauled to an area needing fill or to a disposal area.
During the process of cut-and-fill, it is critical to avoid letting sidecast or waste material enter streams or placing it on unstable areas where it might erode.
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