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• <br />I. Evaluation of Recirculation Pond Embankments <br />A. Site Conditions <br />The Alma Placer Recirculation Ponds are located adjacent to the City of Alma, <br />Colorado, along the Middle Fork South Platte River. The ponds c nsist of two <br />man-made earth embankment structures which share a common intern 1 embankment. <br />They have an average top width of 16 feet, with a crest length o <br />approximately 500 feet parallel to the Middle Fork South Plate R ver. The <br />total storage volume is 1,009,084 cubic feet (23.2 acre-feet) as shown in <br />Table 1. <br />The embankments xere constructed of a homogeneous mixture of cla , sand and <br />gravel. The predominant soil is clay. The outside slopes are a 1.3H to 1V <br />and the inside slopes are at 1.SH to 1V. Soil properties are co servatively <br />estimated based on Field examination and descriptions. <br />Table 2 <br />Summary of Soil Properties <br />• <br />• <br />Total Unit Weight (lb/f t') 118 <br />Saturated Unit Weight (lb/f t') 133 <br />Cohesion (lb/f t') 200 <br />Friction Angle, Phi 25° <br />The earth embankments appear to be in suitable condition for min use. The <br />embankment slopes appear to be well compacted; there was no evid nce of <br />settlement, slumping, cracking, erosion or any other structural efficiencies. <br />In addition, there was no evidence of seepage or scour along the toe of the <br />outside slope. <br />H. Stability Analyses <br />The embankment was analyzed to evaluate the relative stability o the <br />structure. A computer program [1] employing the Simplified Jamb and <br />Simplified Hishop Method of Analysis, was used in this study. T e critical <br />section selected for stability analyses is located along the lon itudinal axis <br />of the embankment parallel to the river. At this location the a bankment has <br />a structural height of approximately 25 feet with an internal height of 18 <br />feet. The stability was computed with a phreatic surface three eet below the <br />top of the embankment, which provides for a highly saturated emb nkment. the <br />results of the static analyses are summarized in Table 3 and the <br />representative critical failure circles are shown in Figure 1. <br />