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C~ ' 3.0 PROPOSED SITE DEVELOPMENT ' The first phase of the proposed site development, as outlined in Section 1.0 of this Design Report, includes, in part, construction of a raise on the existing tailings impoundment embankment, to provide additional tailings storage capacity for interior operation of [he mill. The following subsections present a brief description of the existing embankment and a discussion of the design and construction of the proposed expansion works. ' 3.1 Existing Tailings Impoundment ' The existing embankment, which serves as a starter for the expansion works, appears to be a conventional homogeneous earth-fill type embankment. Detailed, as-constructed drawings of the existing facility were not available from the previous operator. Therefore, a field survey was conducted to determine ' the geometry of the embankment and the topography of the surrounding area, and representative soil samples were collected from the accessible downstream face of the embanlanent to assess the construction materials. ' The downstream face of the existing embankment has a nominal slope of 2.5:1 (horizontal:vertical), however, the face of the embankment is not uniform throughout. The slope of the upstream face is ' unknown, due to the fact that it is almost entirely inundated by tailings. Based upon anecdotal information from the previous operator who oversaw construction of the facility, the slope of the upstream embankment face is understood to be between 2:1 and 2.5:1. The nominal elevation of the embankment crest is ' approximately 8,408 feet above mean sea level (AMSL). The width of the embankment crest is approximately 9 to 10 feet, and the maximum height of the embankment crest above the natural ground surface, based upon interpolation of the adjacent existing topography uphill and downhill of the ' impoundment, is approximately 12 feet. The maximum elevation difference between the embankment crest and the existing ground at the toe of the downstream face is approximately 16 feet. The material of which ' the embankment is constructed can be classified generally as a dense to very dense gravelly sand. The in- place dry density of the material was measured to be 104 pcf and the natural moisture content was measured to be 9.8%. Further information regarding the physical and geotechnical properties of the material are ' .presented in Appendix D to this Report. The upstream face of the embankment and the excavated surfaces of the impoundment are lined with ' an HDPE geomembrane, which is secured in an anchor trench around the full perimeter of the impoundment. Tailings have been discharged into the impoundment from spigots located along the crest of the embankment, and the sand-sized particles which were the first to settle out of the tailings flow have formed astable beach adjacent to the upstream face. The finer fraction of the tailings were carried further in the tailings slurry and deposited in the interior of the impoundment, and the slurry water has been ponded toward t the back of the impoundment, furthest from the embankment. At the time of the field inspection, the tailings impoundment .vas being used as an evaporation pond for water pumped from the nearby Hazel A adit and, thus, the pond had been filled to the maximum allowable level. Consequently, there was very little exposed beach area, and the distance from the face of the embankment to the edge of the ponded water varied from approximately one to ten feet. Even with the volume of ponded water maximized, the depth of water near the center of the impoundment was estimated to be only approximately three feet. Providing for the maintenance of adequate freeboard, [he existing impoundment is essentially filled to the design capacity 6