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<br /> <br />srq,.srmurytanmyrrt. <br />vary o~ o~noo-w~ an <br />, oawmo <br />Page 4 <br />100 year flood everrts were simulated. Tire soil characteristks as presented earlier were <br />used in the analysis. Computer generebad data sheets are presented in Attachment C. <br />A review of Aitachment C shows existing bank profiles are stable with calculated safety <br />factors between 1.25 and 1.38 for mine and pit side flood condifions. Static condHion <br />simulations indicated a safety factor of 1.6. <br />The field investigation indicates that the embankment separating the Varra Dufiam <br />gravel operations and the Cache la Poudre River is primarily composed of sand and <br />gravel. These deposits have a high internal friction angle. The slope of the embankment <br />varies between less than 18 and 42 degrees, with the majority of the bank much less <br />than 3D degrees. The high friction angle and moderate bank sopes creates an <br />inherently stable condition. The high permeability of the bank material reduces the <br />potential for excessive pore pressures within the bank during rapid drawdawn events. <br />The bank slopes with out modifications are stable -even during flood event <br />simulations. Data suggest that proposed bank modifications will not adversary affect <br />bank stability. As the bank material is primarily dense to very dense sand and gravel it <br />is our opinion that subsidence after a flood event wits not occur to any significant <br />degree. The fact that the bank has been in place on the order of degdes without any <br />history of failure supports the analysis presented herein. ff any significant modifications <br />to proposed or existing bank sopes occur this analysis should be considered Invalid. <br />