2018-07-02_PERMIT FILE - M2017013

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Earth Engineering Consultants,LLC EEC Project No. 1122096 Signal Resen•oir Improvements August 5,2015 Page 10 approximately 99 to 124 pounds per cubic (pcf), with an average of about 109 pcf. These dry densities correspond to a consistency of medium stiff to stiff material, which is consistent with the penetration resistance blow counts, (SPT) indicated on the boring logs included in the Appendix. The results of the standard Proctor density tests obtained from the composite subsurface materials within the dam alignment, collected as part of this assessment, revealed a maximum dry density (ASTM Specification D698) of approximately 106 and 108 pounds per cubic foot (pcf) along with an optimum moisture content of approximately 17 and 17.5%. In comparison of the in-situ moisture contents and in-place dry density values obtained from the California Barrel sampling device, at depths of approximately 3 to 14-feet below site grades, (i.e., within the elevated earthen lined dam embankment) in general, equaled to or exceeded a typical earthwork requirement of being compacted to at least 95% of the materials' standard Proctor Density test results. The cohesive subsoils within the existing dam alignment, as previously discussed in this report, also revealed falling head permeability test results, (i.e., k-values) of 1 x 10_8 cm/sec, indicating seepage should be minimized. Based on the supplemental June 2013 field exploration test results, it appears the existing dam alignment earthen embankment is suitable as-is for the proposed improvements. The planned modifications as detailed on Figure No. 2 should be properly benched with the approved earthen liner materials moisture conditioned to f 2% of the materials standard Proctor density, placed in uniform 9-inch lifts, and mechanically compacted to at least 95% of the materials standard Proctor density (ASTM Specification D698). Additional recommendations with regards to Signal Reservoir's wetted perimeter and embankment improvements are presented in the following sections of this report. Slope Stability Analysis This section of the report includes seepage and slope stability analyses which are based on the materials and geometry as previously mentioned herein, and provides an analysis for rapid drawdown and seismic, which are based on undrained soil conditions as typically requested by the State. The results of our evaluation are provided herein and are based on the subsurface information as discussed herein, and the geometry of the dam as well as the location of the downstream toe-drain as prepared by the project's civil engineering design consultant; those documents should be referenced for completeness.