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<br />~' <br />' 1.3 Scope of Work <br />San Luis Mine -Phan D, Rein I Design Report <br />In order to confirm the viability of the conceptual embankment raise design a serves of investigations <br />were conducted to define the physical characteristics of the tailings which will underlie the raise. <br />These investigations consisted of shallow hand auger borings with associated Sampling, testing to <br />' determine insitu tailings density, a series of six cone penetrometer test (CPT) prdbes, and associated <br />laboratory testing. The results of this test work will be described in detail in the following section. <br />' The results of the tailings investigations were incorporated into the model of the structure. This <br />refined embankment model was utilized to evaluate the raise stability under Static and dynamic <br />' earthquake loading conditions. Dynamic loading considered several levels of earthquake ground <br />motion, including the maximum credible earthquake (MCE) as defined in Appendix B of the Permit. <br />In order to evaluate stability of the raise structure under dynamic loading conditions, pseudostatic <br />' stability analyses as presented in the Amendment and Newmark (19b5) type deformation analyses <br />were conducted. <br />SRK was also requested to prepare the technical specifications and design drawings for the raise <br />construction. <br />2.0 TAII.INGS INVFSTIGATIONS <br />2.1 Physical Sampling <br />During October 1992, a series of tests were conducted to determine the insitu density of near surface <br />' tailings throughout the impoundment azeas (during Phase I operations the tailings disposal facility <br />is separated by an embankment into upper and lower impoundments). Due to the recent deposition <br />of tailings within the lower impoundment and soft condition of the tailings surface, testing in this <br />' area was restricted to the tailings "beach" located adjacent to the main embatilanent. <br />' The tailings beach, which will support a portion of the raise, was found to have an [nsitu dry density <br />which ranged from 81.4 pcf to 90.6 pcf and averaged 85.5 pcf. These values are slightly higher <br />than the density which was assumed for freshly deposited tailings in the Amendment. Details of the <br />' insitu density testing are included in Appendix A,1. <br />During December, 1992 a series of hand auger borings were advanced to depths rtanging from 4.5 <br />to 12.4 ft at various locations throughout the impoundment areas. The boring locations and logs <br />Juiy 13, 1993 2 SRK Pfolect No. 14719 <br />1 <br />