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approximately 6 feet in height and constructed to approximately a 3.0 (horizontal) to 1 (vertical) slope <br />• configuration. <br />A phreatic surface has also been added to this model to analyze the embankment under a full reservoir <br />condition with steady state seepage, which is considered to be the worst case scenario. Therefore, a failure <br />of the downstream face of the embankment during peak water storage was analyzed. <br />For this evaluation a unit weight (soil density) of 135 pcf, a cohesion value of 1,000 psf and a phi angle of <br />0 were used for the underlying, natural claystone bedrock materials. A unit weight (soil density) of 127 <br />pcf, a cohesion value of 500 psf and an effective phi angle of 0 were used for the natural clays underlying <br />the proposed embankment; whereas, a unit weight (soil density) of 114 pcf, a cohesion value of 250 psf and <br />a phi angle of 0 were used for the remolded clays to be used in construction of the embankment. <br />Based on our calculations and analysis, the minimum calculated theoretical factor of safety for a failure of <br />the maximum embankment fill slope section, with Pond 2 full, will be 3.68 under static conditions. The <br />slope stability analysis data and a cross section showing the slip (failure) surface are presented in Appendix <br />B. <br />Conclusions: Based on the results of this evaluation, we believe that the proposed cut and fill slopes, if <br />properly constructed, should be stable and perform adequately. We strongly recommend that a <br />representative of NWCC observe the construction of the cut slopes and embankment fill slopes and to <br />verify that the subsurface conditions exposed in the excavations are similar to those assumed in this report, <br />as well as to be on-site to test the compaction of the fill materials as they are placed in the embankment fill <br />slopes. <br />Limitations <br />The recommendations given in this report are based on the soils encountered at this site and our <br />understanding of the proposed construction. We believe that this information gives a high degree of <br />reliability for anticipating the behavior of the proposed structures. However, our recommendations are <br />professional opinions and cannot control nature, nor can they assure the soils profiles beneath those or <br />adjacent to those observed. No warranties expressed or implied are given on the content of this report. <br />Highly expansive clays and claystone bedrock materials were encountered at this site. These soilsibedrock <br />materials are stable at their natural moisture content but can shrink or swell considerably with changes in <br />moisture and loading. The behavior of swelling soils and is not fully understood. The swell potential of <br />49 any particular site can change erratically both in lateral and vertical extent. Moisture changes also occur <br />Job Number: 08-8241 NWCC, Inc. Page 12