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3.0 STRUCTURAL STABILITY <br />3.1 SUMMARY OF EXISTING DATA AND ANALYSIS <br />3.1.1 Embankment Design <br />As discussed earlier, the tailing facility was built in two phases, with the Phase II having a <br />Raise 1 and Raise 2. A typical section of the dam at final buildout is depicted in Figure 3 below, <br />as reproduced from the Phase lI, Raise 2 Design Report (SRK, 1995). The embankment has an <br />overall downstream slope flatter than 3H: IV with two 15 -foot wide benches associated with the <br />upstream raises that are built partially on tailing. <br />EXISTING FOUNCAT'AN LINER SYSTEM <br />EXISTING <br />DRAINAGE BLANKET b LOWER SYSTEM <br />~ _ - - - -� DDETAIL 21 <br />SECTION C-4' <br />SrELiE9A61ZEQ. EAIBANKYENT S7i9S$- SECTION A-A, <br />(Reproduced from SRK, 1995) <br />Figure 3 San Luis Tailing Dam Typical Cross Section <br />The Phase II, Raise 2 Design Report represents the final existing structural stability analysis of <br />the facility and examined the following cases: <br />• Static loading conditions, where the stability of the embankment is examined under <br />normal operating conditions. Presumably this was done with more water in the facility <br />than is present now, but as described below, this cannot be verified. <br />• Liquefaction triggering of the tailing whereby weakening or liquefaction of the tailing <br />could occur during an earthquake design event. <br />• Pseudo static stability analyses, which are an older method of examining stability under <br />earthquake loading. <br />• Deformation and post- liquefaction settlement analyses associated with an earthquake <br />event, whereby the embankment could undergo some deformation. <br />San Luis Project Miller Geotechnical Consultants <br />Tailing Dam Data Report 7 February 2014 <br />:L FrN�F, 11 fiW`,E 2 <br />�I <br />I <br />.. -. -CL iE H RAIL 1 <br />V <br />�. <br />MATERIAL <br />TYPE 1 <br />RAISE 2 FL <br />FN20' <br />PRASE I EL 8390' <br />EXISTING <br />111.NGS EL _.. ._. <br />.'� <br />MATERIAL <br />TYPE I <br />SEE DETAIL A <br />� ' GEOTEXTLE <br />L L r <br />FABRIC <br />�,_EXISTING <br />GRANULAR <br />EMBANKMENT FLL '� <br />` EXISTING '� <br />— MATERIAL <br />TYPE 2 <br />IMATERUL TYPE .1 <br />MATERIAL TYPE 1 <br />2' PROTECTIVE COYER <br />(MATERIAL TYPE 21 <br />EXISTING FOUNCAT'AN LINER SYSTEM <br />EXISTING <br />DRAINAGE BLANKET b LOWER SYSTEM <br />~ _ - - - -� DDETAIL 21 <br />SECTION C-4' <br />SrELiE9A61ZEQ. EAIBANKYENT S7i9S$- SECTION A-A, <br />(Reproduced from SRK, 1995) <br />Figure 3 San Luis Tailing Dam Typical Cross Section <br />The Phase II, Raise 2 Design Report represents the final existing structural stability analysis of <br />the facility and examined the following cases: <br />• Static loading conditions, where the stability of the embankment is examined under <br />normal operating conditions. Presumably this was done with more water in the facility <br />than is present now, but as described below, this cannot be verified. <br />• Liquefaction triggering of the tailing whereby weakening or liquefaction of the tailing <br />could occur during an earthquake design event. <br />• Pseudo static stability analyses, which are an older method of examining stability under <br />earthquake loading. <br />• Deformation and post- liquefaction settlement analyses associated with an earthquake <br />event, whereby the embankment could undergo some deformation. <br />San Luis Project Miller Geotechnical Consultants <br />Tailing Dam Data Report 7 February 2014 <br />