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GEOTECHNICAL STABILITY EXHIBIT <br />This information is presented to address the plan to mine within <br />200 feet of the structures listed in Exhibit S. This analysis is <br />presented in leu of obtaining agreements from the numerous owners <br />of the noted structures. Grand County Department of Road and <br />Bridge, has committed to mining slope adjacent to structures at <br />their final slope rate. Under the approved plan this would be 2:1 <br />from the original land surface to the mine floor. This leaves a <br />stable slope of undisturbed gravel adjacent to the structure. <br />To do this Grand County will have any buried structures <br />(i.e., communication lines, etc.) located by the Colorado Call One <br />locate service and then apply a 25 foot setback from the markers. <br />For above ground structures the setback will be staked prior to <br />mining in those areas. For example, as mining begins near the <br />north fence the 25 foot setback will be staked. A second line <br />will be staked from this setback line a distance equal to the mine <br />depth times 2. This establishes the toe of the slope line. This <br />leaves a slope envelope where mining would be done to create the <br />slopes without backfilling. The three cross-sections on Figure 1 <br />show what is explained above. In Section A, a vertical face is <br />being excavated as mining approaches the structure (fence) and the <br />slope distances have been staked. In Section B the mining has <br />shifted from working a vertical face and is transitioning into the <br />slope mining method. In Section C the final slopes are completed. <br />This method of creating slopes leaves a stable slope requir- <br />ing no backfilling or other work once complete. Over the years we <br />have found that the natural angle of repose for most gravel is <br />approximately 2:1 so it would be possible to mine within ?? feet <br />of a structure with a vertical face and be assured that no damage <br />would occur to the structure by a slope failure. Instead and for <br />safety reasons Grand County has chosen to use the method described <br />above. This will entail more work on their part but when done <br />will have created stable slope that protects the structures. <br />Some of the structures lie at an elevation below the mine <br />floor and would not be effected by the mining operations or be <br />effected by slope failure. In particular, all structures along <br />the south side of the permit area including the Box Car Ranches <br />access road, wire fence chain-link fence, power and communications <br />lines. <br />26 <br />