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<br />Point 17 represents the location along the upper access road with the greatest cut slope <br />angle. At this location the cut slope is nearly vertical (83°). As this point is located <br />near a curve in the upper access road, the road is relatively wide. Figure 4 depicts the <br />cross section at this point. By beginning at the outslope of the road and backfilling at a <br />2:1 slope, a complete backfill of the cut slope could not be achieved. While the <br />backfill would come within three feet of the top of the cut slope, there would be no <br />material available to effect the backfill. A balanced cut and fill calculation at this <br />location reveals that bacldilling could be achieved with an acceptable grade (less than <br />2:1), but the height of the cut slope covered would only be 12 feet, or approximately <br />25 percent of the existing cut slope length. <br />Figure 5 depicts the representative cross section of the lower access road at point 4. <br />Complete backfilling of the cut slope at this location is not possible due to a lack of fill <br />material. A cut and fill balance of backfill at this location illustrates a fill of <br />approximately seven feet of cut slope length. <br />Slope configuration <br />Engineers, hydrologists, erosion control specialists, and geotnotphologists have <br />established that concave slope configurations are mote susceptible to erosion, mass <br />wasting, and instability. With this knowledge, and backfilling cross sections depicted <br />in Figures 1-5, a qualitative assessment of slope configuration was undertaken. <br />At points 4, 8, and 17 along the upper access road, and point 4 along the lower access <br />road, partial backfill (based on cut and fill balances of available material) would create <br />varying degrees of concavity in the slope. The nature of the backfilled slope would <br />contribute to increased sediment load through surface erosion, increased saturation of <br />the backfill, and potential instability in the backfilled material. <br />Slope. erosiou <br />Backfilling the access roads would entail disturbance of the fill slope. By disturbing <br />the fill slope and backfilling the cut slope, total slope length would be increased at <br />every point along the access roads. Increasing the total slope length increases the <br />potential for surficial erosion along the slope. Combined with the creation of a concave <br />slope, the probability of increased surface water runoff and increased sediment yield is <br />increased nearly geometrically. <br />Revegetation <br />Observation of the cut and fill slopes along the access roads revealed significant natural <br />revegetation. At many of the data points along both the upper and lower access roads it <br />was noted that the outslopes had been completely revegetated to the edge of the road <br />surface. On the less steep cut slopes, significant growth of Indian ricegrass (Orympsis <br />hymenoides), bitterbrush (Purshia tridentata), serviceberry (Amelanchier a/nifolia), and <br />-¢ <br />