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Geotechnical Demonstration for Kenney Prooertv <br />The geotechnical demonstration included applies to all pit walls of Colona Pit and any adjacent <br />properties and structures. <br />The structures and azeas of concern present within 200 feet of the permit boundary on the <br />Kenney property are as follows: <br />-a driveway passing along the southeast edge of the permit boundary <br />-wetlands and lakes <br />-irrigated pasture <br />The wetlands, lakes, and irrigated pasture, should be unaffected by the mining neazby, since the <br />pit will not be pumped at all. By using this mining method, no draw down of the suaounding <br />water table will occur, ensuring that the wetlands, lakes, and irrigated pasture on the Kenney <br />property will not be disturbed. <br />The driveway will not be affected by any of the mining activity. A naturally occurring berm <br />exists between the pit and the driveway, which is the natural slope between the upper and lower <br />terraces of the river. This slope has been in place for thousands of yeazs and is well vegetated. It <br />has shown no signs of failure. See Map C-5. Since 1995, United has mined the inside portion of <br />the upper terrace leaving a slope of 2H:1 V. Again, no failures were ever seen in any pit slope. <br />The planned mining below water level will occur at a 2H:1 V slope or greater, which is the same <br />or milder than the existing berm, as shown in Map C-5. <br />All final slopes in reclamation, as shown on Map F, show that 2H:1 V will be the minimum slope. <br />The existing gravel material has few fines and the material does not get its strength from <br />cohesion, but internal angle of friction. Partly rounded gravel of this type in place has an angle of <br />repose of approximately 40 degrees. For non-cohesive soils, this is also the internal angle of <br />friction of the material. The overall slope of 2.OH:1.OV is an angle of 26.6 degrees, therefore, the <br />factor of safety is (tan 40 deg /tan 26.6 deg) which is 1.68. Much steeper slopes within the pit <br />have been in place for years without any sign of failures. <br />Colona Pit November 06 S-3 <br />