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surfaces within the tailings materials, including assumptions that (1) water could <br />rise to the upward extend of tailings slime, and (2) the water would only rise to the <br />lower extent of the cyclone sand "wedges." The resulting calculated factors of <br />safety are about 1.3 and 2.1, respectively, if the tailings slime is assumed to have <br />the same angle of internal friction as the cycloned sand (35 degrees), and 1.2 and <br />2.1 if the friction angle for the slime is 30 degrees. We note our analysis was <br />based on a 3:1 outslope. If the cycloned sand flows to a less steep configuration, <br />slope stability will also be enhanced (i.e. a higher factor of safety). <br />As one would expect, the calculated factor of safety decreases as the <br />assumed water surface rises toward the outward slope. We believe that if the <br />water surface in the decant pool is controlled at about 5 feet below the crest of the <br />cycloned sand, adequate slope stability will be maintained. In no case should the <br />water level in the decant pool be allowed to rise to the crest of the cycloned sand. <br />We note our analysis was based on a 3:1 outslope. If the cycloned sand flows to a <br />less steep configuration, slope stability will also be enhanced (i.e. a higher factor <br />of safety). <br />If we can be of further service in discussing either the contents of this <br />letter or the analysis of the influence of subsurface conditions on the design of <br />the proposed tailings facility, please call. <br />Very truly yours, <br />CTL 1 THOMPSON, INC. <br />Ronald M. McOmber, P.E., D.GE <br />Chairman & CEO <br />RMM /nt <br />(3 copies) <br />via email: melderccr�.unionmilling.com <br />THE UNION MILLING COMPANY <br />TAILINGS POND EMBANKMENT AND FUTURE TAILINGS SLOPE <br />UNION MILL <br />CTL 1 T PROJECT NO. DN45,584 -130 <br />S:IPROJECTS1455001DN45584 .000113013. Letters1L21DN45584- 130- L2.doc <br />2 <br />