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Slope Stability Analysis <br />Varra Gravel Operation - Durham Pit <br />Greeley, Colorado <br />Page 2 <br />the dewatering operation. The regional site location is depicted on Figure 1. Site <br />conditions are depicted on Figure 2. <br />Site Exploration and Laboratory Testing <br />The bank between the Durham gravel operation and Poudre River is approximately 5100 <br />feet in length. The unsaturated bank width varies between 40 feet in the western portion of <br />the study area to in excess of 200 feet in the eastern portion of the study area. The river <br />side bank height generally varies between 12 and 20 feet. The maximum vertical relief on <br />the pit side of the bank is on the order of 50 feet, based in information provided by <br />Anderson Consulting Engineers, Inc. The embankment was inspected on April 12, 2006, <br />and no apparent signs of failure such as tension cracks or raveling were observed. <br />Soil conditions within the bank were evaluated by drilling six soil borings with a truck <br />mounted hollow stem auger rig. The depth of the borings varied between 20 and 50 feet <br />below grade. Representative soil samples were obtained by advancing a two-inch outside <br />diameter split barrel sampler ahead of the auger bit. Details of each boring log are <br />presented in Appendix A. <br />Soil descriptions of cores obtained from within the embankment were recorded during <br />drilling activities. In general, soil conditions consist of up to five feet of fill which is <br />underlain by alluvial deposits of well graded sand and gravel. Bedrock, which consists of <br />a dense, dark gray shale (Pierre Shale) underlies the sand and gravel deposits. The <br />depth to water within the bank varied between 4 and 22 feet below grade. The boring <br />locations are depicted on Figure 2. <br />Overview of Stability Analyses <br />Soil samples obtained from borings B-3, B-4, and B-5 were submitted to CTL Thompson <br />of Fort Collins, Colorado and tested to determine the following properties: <br />> water content;