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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. McAtee Construction Company, has commit- <br />ted to mining slope adjacent to structures at their final slope <br />rate. Under the approved plan this would be 3:1 from the original <br />land surface to the mine floor. This leaves a stable slope of <br />undisturbed gravel adjacent to the structure. <br />To do this McAtee will have any buried structures (i.e., <br />communication lines, etc.) located by the Colorado Call One locate <br />service and then apply a 25 foot setback from the markers. For <br />above ground structures the setback will be staked prior to mining <br />in those areas. For example, as mining begins near a fence the 10 <br />foot setback will be staked. A second line will be staked from <br />this setback line a distance equal to the mine depth time 3. This <br />establishes the toe of the slope line. This leaves a slope <br />envelope where mining would be done to create the slopes without <br />backfilling. The three cross-sections on Figure 1 show what is <br />explained above. In Section A, a vertical face is being excavated <br />as mining approaches the structure (gasline) and the slope dis- <br />tances have been staked. In Section B the mining has shifted from <br />working a vertical face and is transitioning into the slope mining <br />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 80 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 McAtee Construction company has chosen to use the <br />method described above. This will entail more work on their part <br />but when done will have created stable slope that protects the <br />structures. <br /> <br />39 <br />