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as CL soils in accordance with the Unified Soil Class cation System. The fill materials were compacted to a <br />• minimum of 95% of the maximum staadard Proctor density determined in accordance with ASTM D698. As <br />mentioned previously, the compaction test results and the moisture-density relationship (Proctor) curves taken <br />during the consvuction of [he embankment are shown in Appendix A. The shear strength of the compacted fill <br />materials was determined by conducting a number of unconfined compressive strength tests on relatively <br />undistwbed samples obtained from the embankment. The test results indicate that the clay fill materials <br />exhibited unconfined compressive strengths ranging from 5,6?A psf [0 16,995 psf, These results are summarized <br />in Table 1. In addition, a triaxial shear test was run on a sample of the fill materials which was obtained from <br />the cu[ azea located along Haul Road "B" between Station 13+00 and Station 15+00, prior [o [he construction <br />of the haul roads aad embankment. The triaxial shear tests indicate that the recompac[ed clay fill materials had <br />a total cohesion value (C) of 485 psf and an internal angle of friction (o) of 14.2 degrees. The triaxial shear test <br />results for the recompac[ed clays are shown in Figure #3. <br />The natural soils encountered below the embankment and keyway materials consisted of clays which were <br />sfigh[ly sandy with occasional sand lenses interbedded, medium plastic, medium stiff [o stiff, very moist to we[ <br />and brown to dark brown in color. The natural clays classified as CL soils in accordance with the Unified Soil <br />Classification System. An unconfined compressive strength test run on a relatively undisturbed sample of the <br />clays exlvbi[ed an unconfined compressive svength of 1,000 psf. These results are shown in Table 1. A [riaxial <br />shear test run on relatively undisturbed samples of the clays indirate that [he natural clays had a total cohesion <br />value (C) of 760 psf and an internal angle of friction (o) of 3.8 degrees. These triaxial shear test results are <br />shown in Figure #2. <br />• Clays[one bedrock was encountered below the natural clays at a depth of approximately 20 feet below the <br />existing ground surface. The claystone bedrock was sandy, low to medium plastic, hard to very hard, moist and <br />brown in color. <br />Free groundwater was encountered in the [es[ hole a[ a depth of approximately 20.5 feet below the [op of the <br />dam a[ the time of drilling. <br />EMBANKMENT DETAILS <br />Foundation: Due to the high moisture content and softness of the near surface clays beneath the proposed <br />embankment, a layer of 600X Mirafi Stabilization fabric was placed over the ground surface prior to the <br />placement of the embankment and keyway fill materials, Based on our obsen•ations made a[ the site. it appears <br />[hat the topsoil materials had been adequately removed from beneath the embankment areas prior to the <br />placement of the fabric and fill materials. A keyway which had a minimum width of 10 feet was also <br />constructed along [he embankment centerline prior to the fill placement. The keyway and embankment were <br />backfilled with clay till materials which were approved and tested by our office. All of the till materials were <br />compacted [o at least 95% of the maximum standard Proctor density as determined in accordance with ASTM <br />D698. <br />Toe Drain/Drainaee Blanket: Due [o the relatively shallow depth to groundwater and [he saturated condition <br />of the near surface clays, we recommended that a toe drain and drainage blanket be constructed along the <br />• downstream toe of the embankment. These drainage elements were constructed in accordance with our <br />recommendations. The toe drain and drainage blanket consisted of screened (1 1/2" minus) gravels which were <br />lob No. 75-23&1 Nonnwcst Colorado Consultants. Inc Page 3 <br />