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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. Willits Company, Inc., in this applica- <br />tion, has committed to mining slopes adjacent to structures at <br />their final slope rate. Under the approved plan this would be 3:1 <br />from the existing ground surface to the mine floor. This leaves a <br />stable slope of undisturbed gravel adjacent to the structure. <br />To do this Willits will have any buried structures (i.e., <br />communication lines) located, establish the necessary ROW lines <br />associated with the powerlines and then apply a setback from the <br />ROW that is equal to the width of the slope for this part of the <br />mine. For above ground structures the ROW line will be established <br />with a 5 foot setback, and the 25 foot setback from the property <br />lines will be staked prior to mining in those areas. For example, <br />as mining begins on the east line the 25 foot setback will be <br />staked. (The gravel depth is 55 feet for our purpose in this <br />example since only one-half of the deposit will be removed when <br />mining starts.) This establishes the setback; from this line a <br />second line 165 feet away is staked for the 3:1 slope (55~ x 3). <br />Whenever mining takes place between the slope the material will be <br />removed to leave the slope at their final rate so no backfilling <br />will be needed. 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 property line and the slope distances have <br />been staked. in Section B the mining has shifted from working a <br />vertical face and is transitioning into the slope mining method. <br />In Section C the final slopes are completed. <br />This method of creating slopes leaves a stable slope requiring <br />no backfilling or other work once complete. Over the years we have <br />found that the natural angle of repose for most gravel is approxi- <br />mately 2:1 so it would be possible to mine within 50 feet of a <br />structure with a vertical face and be assured that no damage would <br />occur to the structure by a slope failure. Instead and for safety <br />reasons Willits has chosen to use the method described above. This <br />will entail more work on their part but when done will have created <br />a more stable slope. <br />45 <br />