Water: Coastal Zone Act Reauthorization Amendments
C. Road Construction/Reconstruction Management Measure
- Follow preharvest planning (as described underManagement Measure A) when constructing or reconstructing the roadway.
- Follow designs planned under Management Measure A for road surfacing and shaping.
- Install road drainage structures according to designs planned under Management Measure A and regional storm return period and installation specifications. Match these drainage structures with terrain features and with road surface and prism designs.
- Guard against the production of sediment when installing stream crossings.
- Protect surface waters from slash and debris material from roadway clearing.
- Use straw bales, silt fences, mulching, or other favorable practices on disturbed soils on unstable cuts, fills, etc.
- Avoid constructing new roads in SMAs to the extent practicable.
This management measure is intended for application by States on lands where silvicultural or forestry operations are planned or conducted. It is intended to apply to road construction/reconstruction operations for silvicultural purposes, including:
- The clearing phase: clearing to remove trees and woody vegetation from the road right-of-way;
- The pioneering phase: excavating and filling the slope to establish the road centerline and approximate grade;
- The construction phase: final grade and road prism construction and bridge, culvert, and road drainage installation; and
- The surfacing phase: placement and compaction of the roadbed, road fill compaction, and surface placement and compaction (if applicable).
Under the Coastal Zone Act Reauthorization Amendments of 1990, States are subject to a number of requirements as they develop coastal nonpoint source programs in conformity with this measure and will have some flexibility in doing so. The application of this management measure by States is described more fully in Coastal Nonpoint Pollution Control Program: Program Development and Approval Guidance, published jointly by the U.S. Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce.
The goal of this management measure is to minimize delivery of sediment to surface waters during road construction/reconstruction projects. Figure 3-15 depicts various road structures addressed by this management measure. Disturbance of soil and rock during road construction/reconstruction creates a significant potential for erosion and sedimentation of nearby streams and coastal waters. Some roads are temporary or seasonal-use roads, and their construction does not involve the high level of disturbance generated by permanent, high-standard roads. However, temporary or low-standard roads still need to be constructed in such a way as to prevent disturbance and sedimentation. Brown (1972) stated that road construction is the largest source of silviculture-produced sediment in the Pacific Northwest. It is also a significant source in other regions of the country. Therefore, proper road and drainage crossing construction practices are necessary to minimize sediment delivery to surface waters. Proper road design and construction can prevent road fill and road backslope failure, which can result in mass movements and severe sedimentation. Proper road drainage prevents concentration of water on road surfaces, thereby preventing road saturation that can lead to rutting, road slumping, and channel washout (Dyrness, 1967; Golden et al., 1984). Proper road drainage during logging operations is especially important because that is the time when erosion is greatly accelerated by continuous road use (Kochenderfer, 1970). Figure 3-16 presents various erosion and sediment control practices.
Surface protection of the roadbed and cut-and-fill slopes can:
- Minimize soil losses during storms;
- Reduce frost heave erosion production;
- Restrain downslope movement of soil slumps; and
- Minimize erosion from softened roadbeds (Swift, 1984).
Although there are many commonly practiced techniques to minimize erosion during the construction process, the most meaningful are related to how well the work is planned, scheduled, and controlled by the road builder and those responsible for determining that work satisfies design requirements and land management resource objectives (Larse, 1971).
3. Management Measure Selection
Most erosion from road construction occurs within a few years of disturbance (Megahan, 1980). Therefore, erosion control practices that provide immediate results (such as mulching or hay bales) should be applied as soon as possible to minimize potential erosion (Megahan, 1980). King (1984) found that the amount of sediment produced by road construction was directly related to the percent of the area taken by roads, the amount of protection given to the seeded slopes, and whether the road is given a protective surface (Table 3-21).
a. Effectiveness Information
The effectiveness of road surfacing in controlling erosion was demonstrated by Kochenderfer and Helvey (1984)(Table 3-22). The data show that using 1-inch crusher-run gravel or 3-inch clean gravel can reduce erosion to less than one-half that of using 3-inch crusher run gravel and to 12 percent that of an ungraveled road surface.
According to Swift (1984b), road cuts and fills are the largest source of sediment once a logging road is constructed. His research showed that planting grass on cut-and-fill slopes of new roads effectively reduced erosion in the southern Appalachians. The combined effectiveness of grass establishment and roadbed graveling was a 97-99 percent reduction in soil loss.
Swift (1986) measured the extent of downslope soil movement for various categories of roadway and slope conditions (Tables 3-23 and 3-24). He found that grassed fill was more effective than mulched fill or bare fill in reducing the downslope movement of soil from newly constructed roads. The author determined grass, forest floor litter, and brush barriers to be effective management practices for reducing downslope sediment.
Megahan (1980, 1987) summarized the results of several studies that echo Swift's conclusions (Table 3-25 (14k)). The combination of straw mulch with some type of netting to hold it in place reduces erosion by more than 90 percent and has the added benefits of providing immediate erosion control and promoting revegetation. Treating the road surface reduced erosion 70 to 99 percent. Grass seeding alone can control erosion in moist climates, as confirmed by Swift (1984b).
b. Cost Information
The costs associated with construction of rolling dips on roads were estimated by Dubensky (1991) as $19.75 each, with more dips needed as the slope of the road increases.
Ellefson and Miles (1984) determined the decline in net revenue associated with culvert construction, water bar construction, and construction of broad-based dips to be 3.8 percent, 2.3 percent, and 2.4 percent, respectively, for a timber sale with net revenue of $124,340 without these practices. Kochenderfer and Wendel (1980) examined road costs, including bulldozing, construction of drainage dips, culvert installation, and graveling. They concluded that:
- Cost to reconstruct a road (including 600 tons of 3-inch clean stone surfacing at $5.74/ton) = $5,855 per mile. Cost also included 20.5 hours (25 hours/mile) of D-6 tractor time (for road construction and construction of broad-based drainage dips), 23 hours (28 hours/mile) of JD 450 tractor time to spread gravel and do final dip shaping, and installation of two culverts. Road construction without the stone would have cost $1,061/mile.
- Cost for a newly constructed road was $3,673 per mile, including 200 tons of gravel. Costs included 46.5 hours (57 hours/mile) of D-6 tractor time to bulldoze the road and construct 22 drainage dips. Spreading gravel and final dip shaping required 7.5 hours of JD tractor time. This road, constructed without stone, would have cost $2,078 per mile.
The study concluded that road construction costs in terrain similar to the West Virginia mountain area would range from about $2,000/mile with no gravel and few culverts to about $10,000/mile with complete graveling and more frequent use of culverts.
Kochenderfer, Wendel, and Smith (1984) examined the costs associated with road construction of four minimum standard roads in the Appalachians (Table 3-8 gives road characteristics). Excavation costs varied according to site-specific factors (soil type, rock outcrop extent, topography) and increased as the amount of rock needing blasting and the number of large trees to be removed increased. Culvert costs varied according to the size and type of culvert used (Tables 3-26 and 3-27).
Lickwar (1989) studied the costs of various forestry practices in the Southeast. He determined that practices associated with road construction were generally the most expensive, regardless of terrain. The costs for broad-based dips and water bars increased as the terrain steepened, indicating increased implementation of erosion and runoff control practices as slopes increased (Table 3-28). Steeper areas also required additional (nonspecified) road costs that were not necessary in moderate to flat areas. Unit cost comparisons for surfacing practices (Swift, 1984a) reveal that grass is the least expensive alternative, at $174 per kilometer of road (Table 3-29). Five-centimeter crushed rock cost almost $2000 per kilometer, 15-centimeter gravel cost about $6000, and 20-centimeter gravel cost almost $9000. The author cautions, however, that material costs alone are misleading because an adequate road surface might endure several years of use, whereas a grassed or thinly-graveled surface would need replenishing. Even so, multiple grass plantings may be cheaper and more effective than gravel spread thinly over the roadbed, depending on climate, growing conditions, soil type, and road use (Swift, 1984b). Megahan (1987) found that dry seeding alone cost significantly less than seeding in conjunction with plastic netting (Table 3-30).
As discussed more fully at the beginning of this chapter and in Chapter 1, the following practices are described for illustrative purposes only. State programs need not require implementation of these practices. However, as a practical matter, EPA anticipates that the management measure set forth above generally will be implemented by applying one or more management practices appropriate to the source, location, and climate. The practices set forth below have been found by EPA to be representative of the types of practices that can be applied successfully to achieve the management measure described above.
- Follow the design developed during preharvest planning to minimize erosion by properly timing and limiting ground disturbance operations.
- Construct bridges and install culverts during periods when streamflow is low.
- Avoid construction during egg incubation periods on streams with important spawning areas.
- Practice careful equipment operation during road construction to minimize the movement of excavated material downslope as unintentional sidecast.
- Compact the road base at the proper moisture content, surfacing, and grading to give the designed road surface drainage shaping.
- Use straw bales, straw mulch, grass-seeding, hydromulch, and other erosion control and revegetation techniques to complete the construction project. These methods are used to protect freshly disturbed soils until vegetation can be established.
- Prevent slash from entering streams or promptly remove slash that accidentally enters streams to prevent problems related to slash accumulations.
Slash can be useful if placed as windrows along the base of the fill slope. Right-of-way material that is merchantable can also be used by the operator.
- Use turnouts, wing ditches, and dips to disperse runoff and reduce road surface drainage from flowing directly into watercourses.
- Install surface drainage controls to remove stormwater from the roadbed before the flow gains enough volume and velocity to erode the surface. Route discharge from drainage structures onto the forest floor so that water will disperse and infiltrate (Swift, 1985). Methods of road surface drainage include:
- Broad-based Dip Construction. A broad-based dip is a gentle roll in the centerline profile of a road that is designed to be a relatively permanent and self-maintaining water diversion structure and can be traversed by any vehicle (Swift, 1985, 1988) (See Figure 3-17). The dip should be outsloped 3 percent to divert stormwater off the roadbed and onto the forest floor, where transported soil can be trapped by forest litter (Swift, 1988). Broad-based dips should be used on roads having a gradient of 10 percent or less. Proper construction requires an experienced bulldozer operator (Kochenderfer, 1970).
- Installation of Pole Culverts and/or Ditch Relief Culverts. Culverts are placed at varying intervals in a road to safely conduct water from the ditch to the outside portion of the road. Figures 3-18 and 3-19 highlight the design and installation of pole and pipe culverts, respectively. Culverts often need outlet and inlet protection to keep water from scouring away supporting material and to keep debris from plugging the culvert. Energy dissipators, such as riprap and slash, should be installed at culvert outlets (Rothwell, 1978). Culvert spacing depends on rainfall intensity, soil type, and road grade. Culvert size selection should be based on drainage area size and should be able to handle large flows. Open-top or pole culverts are temporary drainage structures that are most useful for intercepting runoff flowing down road surfaces (Kochenderfer, 1970). They can also be used as a substitute for pipe culverts on roads of smaller operations, if properly built and maintained, but they should not be used for handling intermittent or live streams. Open-top culverts should be placed at angles across a road to provide gradient to the culvert and to ensure that no two wheels of a vehicle hit the ditch at once.
- Road Outsloping and Grading. Grade and outslope roadbeds to minimize water accumulation on road surfaces (Kochenderfer, 1970). This practice minimizes erosion and road failure potential. Outsloping involves grading the road so that it slopes downward from the toe of the road cut to the shoulder. The slope should be about 3-4 percent (Rothwell, 1978). Outsloping the roadbed keeps water from flowing next to and undermining the cut bank, and is intended to spill water off the road in small volumes at many random sites. In addition to outsloping the roadbed, a short reverse grade should be constructed to turn water off the surface. Providing a berm on the outside edge of an outsloped road during construction, and until loose fill material is protected by vegetation, can eliminate fill erosion (Swift, 1985). The effectiveness of outsloping is limited by roadbed rutting during wet conditions. Also, berms may form along the edge of older roadbeds and block drainage (Swift, 1985). Therefore, proper maintenance of these structures is necessary.
- Ditch and Turnout Construction. Ditches should be used only where necessary and should discharge water into vegetated areas through the use of turnouts. The less water ditches carry and the more frequently water is discharged, the better. Construct wide, gently sloping ditches, especially in areas with highly erodible soils. Ditches should be stabilized with rock and/or vegetation (Yoho, 1980) and outfalls protected with rock, brush barriers, live vegetation, or other means. Roadside ditches should be large enough to carry runoff from moderate storms. A standard ditch used on secondary logging roads is a triangular section 45 cm deep, 90 cm wide on the roadway side, and 30 cm wide on the cut bank side. Minimum ditch gradient should be 0.5 percent, but 2 percent is preferred to ensure good drainage. Runoff should be frequently diverted into culverts to prevent erosion or overflow (Rothwell, 1978).
- Install appropriate sediment control structures to trap suspended sediment transported by runoff and prevent its discharge into the aquatic environment.
Methods to trap sediment include:
- Brush Barriers. Brush barriers are slash materials piled at the toe slope of a road or at the outlets of culverts, turnouts, dips, and water bars. Brush barriers should be installed at the toe of fills if the fills are located within 150 feet of a defined stream channel (Swift, 1988). Figure 3-20 shows the use of a brush barrier at the toe of fill. Proper installation is important because if the brush barrier is not firmly anchored and embedded in the slope, brush material may be ineffective for sediment removal and may detach to block ditches or culverts (Ontario Ministry of Natural Resources, 1988). In addition to use as brush barriers, slash can be spread over exposed mineral soils to reduce the impact of precipitation events and surface flow.
- Silt Fences. Silt fences are temporary barriers used to intercept sediment- laden runoff from small areas. They act as a strainer: silt and sand are trapped on the surface of the fence while water passes through. They may consist of woven geotextile filter fabric or straw bales. Silt fences should be installed prior to earthmoving operations and should be placed as close to the contour as possible.
- Riprap. Riprap is a layer of rocks or rock fragments placed over exposed soil to protect it from erosive forces. Riprap is generally used only in areas where the velocity of water flow, seriousness of erosion, steepness of slope, or material type prevents satisfactory establishment of vegetation. Stones of suitable size are fitted and implanted in the slope to form a contiguous cover (Figure 3-21). When used near streams, riprap should be extended below the stream channel scour depth and above the high water line. Commonly, a filter cloth or graded filter blanket of small gravel is laid beneath the riprap. Riprap should not be used on slopes that are naturally subject to deep-seated or avalanche-type slide failure. Riprap should be used in conjunction with other slope stabilization techniques and then only if these techniques are ineffective alone. Riprap is not recommended for very steep slopes or fine-grained soils (Hynson et al., 1982).
- Filter Strips. Sediment control is achieved by providing a filter or buffer strip between streams and construction activities in order to use the natural filtering capabilities of the forest floor and litter. The Streamside Management Area management measure requires the presence of a filter or buffer strip around all waterbodies.
- Revegetate or stabilize disturbed areas, especially at stream crossings.
Cutbanks and fillslopes along forest roads are often difficult to revegetate (Berglund, 1978). Properly condition slopes to provide a seedbed, including rolling of embankments and scarifying of cut slopes. The rough soil surfaces will provide niches for seeds to lodge and germinate. Seed as soon as possible after disturbance, preferably during road construction or immediately following completion and within the same season (Larse, 1971). Early grassing and spreading of brush or erosion-resisting fabrics on exposed soils at stream crossings are imperative (Swift, 1985). See the Revegetation of Disturbed Areas management measure for a more detailed discussion.
- Protect access points to the site that lead from a paved public right-of-way with stone, wood chips, corduroy logs, wooden mats, or other material to prevent soil or mud from being tracked onto the paved road.
This will prevent tracking of sediment onto roadways, thereby preventing the subsequent washoff of that sediment during storm events. When necessary, clean truck wheels to remove sediment prior to entering a public right-of-way.
- Construct stream crossings to minimize erosion and sedimentation.
Avoid operating machinery in waterbodies. Work within or adjacent to live streams and water channels should not be attempted during periods of high streamflow, intense rainfall, or migratory fish spawning. Avoid channel changes and protect embankments with riprap, masonry headwalls, or other retaining structures (Larse, 1971).
If possible, culverts should be installed within the natural streambeds. The inlet should be on or below the streambed to minimize flooding upstream and to facilitate fish passage. Culverts should be firmly anchored and the earth compacted at least halfway up the side of the pipe to prevent water from leaking around it (Figure 3-22). Both ends of the culvert should protrude at least 1 foot beyond the fill (Hynson et al., 1982). Large culverts should be aligned with the natural course and gradient of the stream unless the inlet condition can be improved and the erosion potential reduced with some channel improvement (Larse, 1971). Use energy dissipators at the downstream end of the culverts to reduce the erosion energy of emerging water. Armor inlets to prevent undercutting and armor outlets to prevent erosion of fill or cut slopes.
- Excavation for a bridge or a large culvert should not be performed in flowing water. The water should be diverted around the work site during construction with a cofferdam or stream diversion.
Isolating the work site from the flow of water is necessary to minimize the release of soil into the watercourse and to ensure a satisfactory installation in a dry environment. Limit the duration of construction to minimize environmental impacts by establishing disturbance limits, equipment limitations, the operational time period when disturbance can most easily be limited, and the use of erosion and sediment controls, such as silt fences and sediment catch basins. Diversions should be used only where constructing the stream crossing structure without diverting the stream would result in instream disturbance greater than the disturbance from diverting the stream. Figure 3-23 portrays a procedure for installing a large culvert when excavation in the channel of the stream would cause sedimentation and increase turbidity.
- Compact the fill to minimize erosion and ensure road stability (Hynson et al., 1982).
During construction, fills or embankments are built up by gradual layering. Compact the entire surface of each layer with a tractor or other construction equipment. If the road is to be grassed, the final layer should not be compacted in order to provide an acceptable seedbed.
- Properly dispose of organic debris generated during road construction (Hynson et al., 1982).
- Stack usable materials such as timber, pulpwood, and firewood in suitable locations and use them to the extent possible. Alternatives for use of other materials include piling and burning, chipping, scattering, windrowing, and removal to designated sites.
- Organic debris should not be used as fill material for road construction since the organic material would eventually decompose and cause fill failure (Hynson et al., 1982; Larse, 1971).
- Debris that is accidently deposited in streams during road construction should be removed before work is terminated.
- All work within the stream channel should be accomplished by hand to avoid the use of machinery in the stream and riparian zone (Hynson et al., 1982).
- Use pioneer roads to reduce the amount of area disturbed and ensure stability of the area involved.
Pioneer roads are temporary access ways used to facilitate construction equipment access when building permanent roads.
- Confine pioneer roads to the construction limits of the surveyed permanent roadway.
- Fit the pioneer road with temporary drainage structures (Hynson et al., 1982).
- When soil moisture conditions are excessive, promptly suspend earthwork operations and take measures to weatherproof the partially completed work (Larse, 1971; Hynson et al., 1982).
Regulating traffic on logging roads during unfavorable weather is an important phase of erosion control. Construction and logging under these conditions destroy drainage structures, plug up culverts, and cause excessive rutting, thereby increasing the amount and the cost of required maintenance (Kochenderfer, 1970).
- Locate burn bays away from water and drainage courses.
- If the use of borrow or gravel pits is needed during forest road construction, locate rock quarries, gravel pits, and borrow pits outside SMAs and above the 50-year flood level of any waters to minimize the adverse impacts caused by the resulting sedimentation. Excavation should not occur below the water table.
Gravel mining directly from streams causes a multitude of impacts including destruction of fish spawning sites, turbidity, and sedimentation (Hynson et al., 1982). During the construction and use of rock quarries, gravel pits, or borrow pits, runoff water should be diverted onto the forest floor or should be passed through one or more settling basins. Rock quarries, gravel pits, spoil disposal areas, and borrow pits should be revegetated and reclaimed upon abandonment.