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<br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br />f) Back analysis of existing slopes. This inGuded the back analysis of existing Santa Fe, Pink <br />Gneiss and alluvium slopes. The exposures were limited since the property is generally <br />covered by overburden. The exposures on average were under 20 feet in vertical height. <br />The slopes are shown in Figure 4. This reinforced the design strengths that were <br />determined through subsequent analysis. <br />g) Geological Interpretation of surticial geology as defined by BMG geologists. This was <br />employed to divide the ultimate pit into areas with rock units exhibiting similar <br />geotechnical characteristics. <br />3.0 GEOLOGY ANDGEOHYDROLOGY <br />The San Luis deposft is an epithermal deposit located within a Biotite Gneiss that is situated <br />beneath a thrust plate of Pink Granite Gneiss. Subsequent movement along this plate has resulted <br />in a clay horizon measuring 5 - 50 feet thick. This unit is defined as 'Green Clay F.sult'. Prior to <br />erosion, the Green Clay covered the entire gold -mineralized area and has since treen removed <br />from about half of the mine area. This fault is shown in Figure 4 and dips to the west and south at <br />approximately 15°. The Biotite Gneiss lies immediately below the Green Clay and is a moderately <br />strong rock. Instability in this material will be controlled by joints. <br />Overlying the Green Clay is the altered Pink Granite Gneiss which is strongly Uractured and <br />chlorite-clay altered to yield a weak rock mass. <br />Immediately above the Pink Gneiss is the Santa Fe formation which are gravel deposits formed <br />from channels cut into the weaker Pink Gneiss and Green Clay materials. This material consists of <br />a matrix of either sand, gneisses or highly altered clay material. It yields a weak rock mass. <br />Alluvium covers most of the deposit in the project area. Its lower comact against the similar Santa <br />Fe Formation is not distinct. The thickness of alluvium is generally less than 30 feet. The alluvium <br />will be treated as a weak Santa Fe for purposes of design since it resembles a conglomerate <br />whose matrix is primarily sand. <br />Figure 4 is a geologic interpretation of the lithologic units that have been mapped by BMG <br />geologists. The ultimate pit walls will be located in rock units as follows: <br />a) West Pit Ore Zone <br />North wall: Pink Gneiss + Green Clay +Biotite Gneiss <br />West wall: Santa Fe + Pink Gneiss + Green Ctay +Biotite Gneiss <br />South Wail: Santa Fe + Green Clay +Biotite Gneiss <br />East Wall: Biotite Gneiss <br />