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Mr. Raymond Lazuk June 28, 2017 <br /> Climax Molybdenum Company, Climax Mine 3 1661214 006 RSP RevO <br /> All the Climax OSF computed FoS presented in Golder(2017)meet or exceed the minimum project design <br /> criteria noted above, both for the maximum operational and closure stability scenarios. It should be noted <br /> that all the computed FoS also exceed the DMRS guidance minimum FoS criteria, with one exception: the <br /> FoS for section C-C' for the pseudo static case. The computed pseudo-static FoS as presented in Golder <br /> (2017) are 1.1 during operations under the OBE and 1.0 after closure under the MDE. It should also be <br /> noted that the DMRS guidance does not define a minimum seismic reoccurrence interval. The magnitude <br /> of seismic events that could be considered in the analysis, and thus the range in computed factors of safety, <br /> can be expected to vary significantly depending upon the seismic reoccurrence interval selected. The <br /> following section will provide Golder's justification for the use of a FoS of unity for the pseudo-static <br /> conditions as an acceptable standard of care criteria. <br /> Golder has performed an additional analysis, to evaluate the post closure conditions using the OBE for this <br /> response. Our results show that the FoS for the post-closure condition using a 475-year reoccurrence <br /> interval is 1.15, which meets the guidance as provided in DRMS (2017a). The remaining sections of this <br /> memorandum provide additional justification for the standard of care, basis of using pseudo-static analyses, <br /> and the stability analyses conducted as documented in Golder(2017). <br /> 3.0 JUSTIFICATION FOR PSEUDO-STATIC CRITERIA <br /> 1.1 Mechanism of Movement <br /> As noted in Golder (2017), earthquake (seismic) loading conditions are typically simulated using a <br /> conservative and simplified pseudo-static approach, unless the results justify conducting a more rigorous <br /> displacement analysis to compute the actual predicted displacements. In an actual seismic event, a peak <br /> acceleration is be sustained for only a fraction of a second, before it reverses.Actual seismic time histories <br /> are characterized by multiple oscillating frequencies, which alternate between destabilizing and stabilizing <br /> forces. The accelerations produced by seismic events tend to build to a peak acceleration, which then <br /> quickly decays to lesser accelerations. Consequently, the duration during which a mass is actually <br /> subjected to a unidirectional, peak seismic acceleration is short and finite in time, rather than an infinite <br /> pulse as assumed by a simplistic pseudo-static simulation.As an example,a time history from the El Centro, <br /> California earthquake, as presented in Newmark (1965) is shown below as Figure 1. <br /> (a) Ground Acceleration <br /> 02 <br /> a <br /> c <br /> � O <br /> 0 <br /> `m <br /> u —o2 <br /> u 14 <br /> Q Aq=0.32 g <br /> (b)Ground Velocity <br /> e <br /> uMA 0 AN AM J'\^ A I r^_�n 0", <br /> m <br /> w <br /> c O <br /> T w **,%v rq I "J Y V <br /> c �0 <br /> V x 13,7 in./sec. <br /> -le <br /> e 0=8.3 -n. <br /> `- (c) Ground Displacement <br /> c <br /> _V —V <br /> E <br /> u <br /> u T <br /> 0 <br /> 0 <br /> .n <br /> a <br /> 0 3 10 IS 20 25 30 <br /> Figure 1: Example Earthquake Time History, El Centro Earthquake, From Newmark(1965) <br /> Golder <br /> 1P <br /> 661214 006 RSP RM Responses to DRMS Comments 28JUN17 docx Associates <br />