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Christopher Schmitz June 2, 2014 Climax Molybdenum Company 4 1402712 001 TMO1 RevO ■ Seismic stability was evaluated using a pseudo-static analysis procedure generally following the Hynes-Griffin and Franklin method (1984). For this pseudo-static analysis, total stress shear strength parameters were used for the tailings materials, while 80 percent of the effective stress shear strength was used for all other materials (excluding the overburden material, since straining and strength degradation due to shaking are expected to be minimal for this material). A seismic load coefficient of 0.03 for the OBE (half the PGA)was used for the pseudo-static analyses. 4.0 MATERIAL PARAMETERS The material properties presented in Table 1 and Table 2 were used for the static and pseudo-static analyses, respectively. These parameters are consistent with those used in the OSF design report (Golder 2012) and were selected based on a review of the available laboratory test data, historical reports, and engineering judgment. A more in-depth discussion of material strength selection is presented in the main text of the design report. Table 1 presents the material properties used for the static stability analyses. A combination of Mohr- Coulomb and bi-linear Mohr-Coulomb failure envelopes were used for the native materials and tailings. A traditional Mohr-Coulomb failure envelope was used for the Minturn Formation. The envelope was obtained from a staged consolidated-undrained triaxial test performed on a relatively undisturbed sample of clayey residual soil weathered from the Minturn Formation. Bi-linear Mohr-Coulomb failure envelopes were constructed for both the Lincoln Porphyry and Glacial Till. For these materials, bi-linear envelopes were found to provide the best fit to the data provided by large-scale direct shear tests on reconstituted samples of these materials. The strength of the tailings material was determined by a series of consolidated-undrained triaxial tests on tailings fines. The Mohr-Coulomb envelope for tailings assumes no effective cohesion. Two large-scale direct shear tests were performed on samples of mine overburden collected from the site. The shear box was 12 by 12 inches, and as a result only the sampled material finer than 2 inches was used in the test. Assuming zero cohesion, the results indicate residual strengths of 35 to 36 degrees (linear Mohr-Coulomb). A power curve best fit for the laboratory data lies approximately midway between the Leps (1971) curves for low and average strength rockfill. For the Climax mine overburden, the curvilinear power curve fit to the large-scale direct shear test data was selected for use in stability modeling. This curve is considered representative of expected worst-case conditions within the OSFs for areas where overburden derived from igneous and/or metamorphic rock makes up the majority of the OSF fill. For the majority of the OSF, this strength envelope is considered conservative, as the tests were performed only on the finer-grained matrix material and was not corrected to account for the large amount of oversize material present in the OSFs. Note that approximately 30 percent of the overburden is expected to consist of sedimentary rock. The power curve described above is also considered representative for areas of the OSF containing average quantities of Golder I:\14\1402712\0100\0122\001 TM01 RevO\1402712 001 TM01 RevO ClimaxMolyOSFStabilityAnalysis 02JUN14.docx ` Associates