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bedding is not dipping unfavorably from a stability standpoint. Expect occasional unraveling of <br /> the landslide scarp at the transition between the through-cut and cut-fill sections, potentially <br /> requiring occasional removal of this material to maintain road access. <br /> Our test pits indicate that the fill is benched into the rock, a favorable condition from a roadway <br /> stability standpoint. The upper approximate 12 inches of roadway fill is dense and properly <br /> compacted (this is confirmed by the test results in the May 261h report). Below this depth, the fill <br /> is loose and appeared to have been poorly compacted if at all. Except for the presence of <br /> occasional oversize cobbles near the bottom of the test pits, our test results indicate the fill is <br /> suitable for its intended use. Atterburg limits results are within acceptable range for structural <br /> fill; no organic material was observed in the fill exposed in the test pits. <br /> The retaining wall across the drainage appears to be performing well, except for some outward <br /> leaning of vertical members on the river side. The retaining wall along cut-fill section of access <br /> road appears to be performing poorly in its present condition. The side slope retaining wall has <br /> either undergone extensive movement and, for all intents and purposes, is failing and/or is <br /> exhibiting characteristics of poor workmanship during its construction. The silt fence is in poor <br /> condition and is not capable of performing its intended function, much less resisting soil and <br /> rock sloughing off the steep slope directly above it. <br /> In summary, the good news is as follows: no seepage, good quality fill, fill appears to be <br /> constructed on bench in the rock, the road has survived 2 winters intact, bedding of rock in cut <br /> slope is not unfavorable from a stability standpoint, retaining walls on either side of drainage fill <br /> appears to be performing well. The bad news includes the following: retaining wall current <br /> performance and future capabilities to perform as intended uncertain at best, loose fill at depth, <br /> fill slopes of unknown quality and thickness on slopes steeper than 1.5:1, roadway steeper than <br /> 15 percent. <br /> Recommendations <br /> To utilize the road for the intended purpose, we recommend a work plan be prepared and <br /> implemented that at a minimum addresses the following: <br /> Roadway fill: Complete construction of the road in a manner that results in road grades less than <br /> 15 percent. The upper 30 inches of road should be compacted to at least 90 percent relative <br /> compaction per ASTM D 1557-02. In areas where less than 30 inches of fill will be placed to <br /> complete the road, over-excavate as necessary, scarify to a depth of 6 inches, moisture condition <br /> as necessary, and compact to at least 95 percent relative compaction per ASTM D 1557-02. <br /> Remove loose logs, branches, and other debris from the steep slope on the outboard side of the <br /> road. Replace repair silt fence at bottom of slope. Construct new fill slopes no steeper than 1.5: <br /> 1. Where the minimum allowable roadway width cannot be achieved at these fill slope <br /> inclinations, utilize horizontal reinforcement in the fill, such as Hilfiker walls to construct the fill <br /> slopes. These slopes, where horizontally reinforced, can be increased to 3/a:1 or steeper. <br /> May 30, 2010 <br />