High, steep road cuts in fractured bedrock are most susceptible to rockfall. Rockfall fills ditches and plugs culverts, which increases incidents of road failures. Roads constructed through wet due to a poor bearing surface. I. (721) Siskiyou areas often experience prism failures (722) Holland Association (W-14 on MFP Step 1 Overlay) Recommended Practices Road Construction on Slopes Exceeding 70 Percent Avoid locating roads on slopes exceeding 70 percent and on areas exhibiting instability. Roll the road grade, taking advantage of natural benches, ridges, and other stable positions. 7. Fills Crossing Drainages Partial cut using full or partial suspension systems on slopes exceeding 70 percent. Most critical conditions exist on south and we st exposures where the annual rainfall is less than 35 inches. Tractor Logging on Slopes over 20 Percent Tractor logging should be limited to slopes less than 20 percent. Evaluate Bug-Killed Timber Evaluate bug-killed timber thoroughly before removing dead and dying trees to determine cause of insect infestation. Disturbances caused by tractor logging and road construction may increase infestations which weaken or ultimately kill tree roots, thereby promoting massive failures through loss of mechanical support. Remove dead and dying timber by methods that minimize surface disturbance (i.e., suspension systems). Broadcast Burning on Harvested Areas Herbicides or other means should be used as alternatives to burning or scarification. Do not spray adjacent to live streams. Fills must be designed for overtopping and for stability when saturated. Rock fills are simple and effective. Consider bridging across debris channels. Granitic Soils Subject to Piping All fills should be compacted to a degree consistent with design standards and material properties. Large Cuts and Fills Which Produce Considerable Sidecast Cut slopes should generally be as steep as possible consistent with subsurface strength conditions. Multiple cut slopes should be constructed when weak overburden requires it, and it is practical (i.e., natural ground slope makes it feasible). Buttressing should be considered for cut slopes with stability problems. Off-Road Vehicle (ORV) Use ORV's (4-wheel drives and motorbikes) should be limited to surfaced roads. Discourage travel on skid roads, unsurfaced haul roads, and unroaded areas. 11. Granite Pits Shape, mulch, seed, and fertilize granite material sites prior to abandonment. Refertilize at 3 to 5-year intervals. Droughty conditions may require watering to maintain vegetation. Lay out skid trails prior to timber harvest. Clearcutting on or above debris slide prone areas will substantially increase the probability of massive failure. 8. Clearcutting or removing brush or hardwoods on very steeply sioping com Tractor logging on slopes over 20 percent results in surface soil Harvesting bug-killed timber may increase the mass failure hazard. Broadcast burning on harvested areas will remove the duff layer, All fills crossing drainages within this soil association must be Granitic soils are subject to piping in uncompacted fills. 9. Large cuts and fills produce considerable sidecast which buries ORV use increases overland flow by removing the protective duff layer Granite bedrock, when exposed to weathering by water and temperature Partial cut or avoid cutting on slopes exceeding 70 percent. Use a suspension cable or aerial harvesting system. Avoid tractor logging where shallow soils occur (i.e. on ridge crests Alternatives to Burning for Site Preparation Use alternatives to burning, such as herbicides, in site preparation. Partial cut using a full suspension yarding system. Actively moving Use low pressure ground skidder when moisture content is less than 25 Evaluate bug-killed timber thoroughly before removing dead and dying Confine roads to slopes less than 70 percent. Roll the road grade, D-9 taking advantage of stable positions (i.e., ridges, saddles, and natural benches). End haul excavated materials on slopes exceeding 70 percent, which would otherwise be sidecast during excavation, to a safe disposal (i.e., ridge crest, saddle, natur al bench). Shape and revegetate disposal area. Road Construction Through Dipped Bedding Planes Locate roads through areas where the bedding planes or weathering surfaces are not included with the slope. Existing road cuts in the area of proposed road location offer helpful clues to the orientation of the bedding planes. 10. Road Construction Through Fractured Bedrock Avoid high steeply sloping cuts in highly fractured bedrock. Locate and design roads to minimize heights of cuts. 11. Roads Constructed on Unstable Areas Locate roads on stable positions such as ridges, natural benches, and gentle, even slopes. Avoid seeps, old landslides, and oversteepened slopes. Road Construction Through Wet Areas Locate roads on well-drained soil types. Avoid wet areas by rolling the road grade. Place perforated pipe or an open drainage ditch upslope from cutbanks (where crossing wet areas) to intercept and divert surface and subsurface water. These practices should be employed only when alternate routes are not available. the 9. 12. Ramp over wet areas using large rocks as a base where cuts are not required. Clearcutting or removing brush and hardwoods on slopes in excess of 70 percent will expose soil to raindrop splash erosion and initiate soil raveling. The soil fines are removed and the available water capacity is reduced (especially critical on droughty south and we st exposures). Once these processes begin, it is difficult to reestablish protective vegetation cover. Tractor logging on ridge crests and steep slopes occupied by shallow gravelly soils will remove the duff layer and surface soil, which 8. protects the underlying soil layers from erosion by water and raveling. Removing the duff layer and surface soil will reduce site productivity and degrade water quality. Broadcast burning on steeply sloping south and west exposures will remove the duff layer, thereby promoting excessive erosion and reducing site productivity. also Clearcutting in unstable areas will increase massive failure, especially where roads traverse the clearcut unit. Tractor logging on clayey soils removes the duff layer and results in soil compaction, causing a reduction in infiltration and initiation of overland flow on skid trails and a subsequent reduction in site productivity. Overland flow dislodges and transports soil particles, causing water quality degradation. Harvesting bug-killed timber may result in an increase in mass failure incidents. De ad and dying timber is often on unstable positions created by a seasonal watertable that weakened the timber and encouraged insect infestation. Tractor logging in boggy areas may alter or intercept subsurface water flow, causing a rise in the water table and a subsequent reduction in site productivity. High water tables restrict rooting and weaken native vegetation. Road construction on slopes exceeding 70 percent produces very gravelly sidecast material that buries downslope vegetation and creates a droughty condition, resulting in reduced site production. Sidecast can cause overloading of the fill slope and subsequent failure. Roads constructed through steeply sloping terrain where bedding planes or weathering surfaces are inclined with the slope are subject to massive failure. High, steeply sloping road cuts in fractured bedrock are most susceptible to rockfall. Roads constructed on oversteepened slopes, hummocky (uneven) topography, and across seeps and old landslides will substantially increase the occurrence of massive failures. Road 3 constructed through wet areas often experience prism failures due to a poor bearing surface. K. (745) Laurelhurst - (706) Medco Association (W-16 on MFP Step 1 Overlay) Recommended Practices 1. Disturbance of Clayey Soils Use low pressure ground skidder when moisture content is less than 25 percent. Skid trails and landings should be ripped following final harvest at driest time of year. Evaluate bug-killed timber thoroughly before removing dead and dying trees to determine cause of insect infestation. Disturbances caused by tractor logging and road construction may increase infestations which weakens or ultimately kills tree roots, thereby promoting massive failures through loss of mechanical support. Remove dead and dying timber by methods that minimize surface disturbance (i.e., suspension systems). Locate roads on stable positions such as ridges, natural benches, and gentle, even slopes. Avoid seeps, old landslides, and over-steepened slopes. 5. Sidecast Material From Road Construction 6. End haul material that would otherwise be sidecast during road construction to a safe disposal site. Shape and revegetate disposal areas. Roads Constructed Through Wet Areas Locate roads on well-drained soil types. Avoid wet areas by rolling the road grade. Place perforated pipe or an open drainage ditch upslope from the cutbanks (where crossing wet areas) to intercept and divert surface and subsurface water. These practices should be employed only when alternate routes are not available. Ramp over wet areas using large rocks as a base where cuts are not required. Reasons 2. Tractor logging removes the duff layer and results in soil compaction, causing a reduction in infiltation and initiation of overland flow on skid trails and subsequent reduction in site productivity. Overland flow dislodges and transports colloidal-sized soil particles, causing water quality degradation. Harvesting bug-killed timber may result in an increase in mass failure incidents. De ad and dying timber is often in unstable positions created by a water table that weakened the timber and encouraged insect infestation. 3. Tractor logging in boggy areas may alter or intercept subsurface water flow, causing a rise in the water table and subsequent reduction in site productivity. High water tables restrict rooting and weaken native vegetation. Roads constructed on oversteepened slopes, hummocky (uneven) topography, and across seeps and old landslides will substantially increase the occurrence of massive failures. Sidecast material from road construction, when saturated, causes roadfill failures. Roads constructed through wet areas often experience prism failures due to a poor bearing surface. L. (750) Dumont (740) Geppert Association (W-17 on MFP Step 1 Overlay) Limit period of operation to when soil moisture is below 25 percent. All primary skid trails should be waterbarred. Rip and waterbar skid trails following final removal at driest time of year (July 15 through D-11 M. September 15). Rip to a depth of 12 to 15 inches with spacing equal to depth. Waterbars should be spaced at 25 to 100 foot intervals based on natural slope. 4. End haul material that would otherwise be sidecast during road construction to a safe disposal site. Shape and revegetate disposal areas. Roads Constructed Through Wet Areas Locate roads on well-drained soil types. Avoid wet areas by rolling the road grade. Place perforated pipe or an open drainage ditch upslope from the cutbanks (where crossing wet areas) to intercept and divert surface and subsurface water. These practices should be employed only when alternate routes are not available. Ramp over wet areas using large rocks as a base where cuts are not required. Reasons 1. Tractor logging removes the duff layer and results in soil compaction, causing a reduction in infiltration and initiation of overland flow on skid trails and subsequent reduction in site productivity. Overland flow dislodges and transports colloidal-sized soil particles, causing water quality degradation. Tractor logging in boggy areas may alter or intercept subsurface water flow, causing a rise in the water table and a subsequent reduction in site productivity. High water tables restrict rooting and we aken native vegetation. Sidecast material from road construction, when saturated, causes road failures. Roads constructed through wet areas often experience prism failures due to a poor bearing surface. (770) Pearsoll (R) Rock Land Association (Shown as W-18 on MFP Step 1 Overlay) Partial cut using a full suspension system. Plant to reestablish ground cover on bare soil areas. Shallow rocky areas should not be logged. Limit yarding to dry season of the year (generally June through October). Confine tractor logging to slopes less than 35 percent. Tractor log only during the time of the year when the soil moisture content is below 25 percent. All primary skid trails should be waterbarred. Rip and waterbar skid trails following final removal at driest time of year (July 15 through September 15). Rip to a depth of 12 to 15 inches with spacing equal to depth. Waterbars should be spaced at 25 to 100 foot intervals based on natural slope. Allow no tractor logging in boggy areas or landscapes where water accumulates (i.e., swamps, drainage ways, etc.). Locate skid trails on ridges or other convex positions. Clearcutting on Slide Prone Areas Partial cut using a full or partial suspension yarding system. Actively moving areas or slide prone areas traversed by roads should not be harvested. |