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• GEOTECHNICAL STABILITY EXHIBIT EXHIBIT U <br />There aze no buildings or structures outside the pemut area which could be affected by the <br />operation. All final slopes in reclamation, as shown on Map F, show that 2H:1 V will be the <br />minimum slope. The existing gravel material has few fines and the material does not get its <br />strength from cohesion, but internal angle of friction. Partly rounded gravel of this type in place <br />has an angle of repose of approximately 40 degrees. For non-cohesive soils, this is also the <br />intemal angle of friction of the material. The overall slope of 2.OH:1.OV is an angle of 26.6 <br />degrees, therefore, the factor of safety is (tan 40 deg /tan 26.6 deg) which is 1.68. Much steeper <br />slopes within the pit have been in place for years without any sign of failures. Since the 3H:1 V <br />slope on both sides of the siphon aze milder then the slopes described above, the safety factor for <br />this azea is even greater. <br />I, Greg Lewicki, P.E., with over 20 years of experience in mine slope safety analysis in <br />Colorado, state that this is true and that this factor of safety is adequate to prevent failure of the <br />i slopes. <br />~~ G•!L`Gr/~CG <br />/~~~0~ <br />U <br />Colona Pit March 07 <br />