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GEOTECHNICAL STABILITY EXHIBIT <br />This information is presented to address the plan to mine <br />within 200 feet of the structures listed in Exhibit S. This <br />analysis is presented in leu of obtaining agreements from the <br />numerous owners of the noted structures. Albert Frei and Sons, <br />Inc., in this application, has committed to mining slope adja- <br />cent to structures at the in situ rate of 2:1 along the outer <br />perimeter of the mine. This leaves a stable slope of undis- <br />turbed gravel adjacent to the structure. As soon as possible <br />backfilling will begin on-the excavated area to add additional <br />protection from slope failure until eventually the excavated <br />area has been filled to at lease it existing elevation. <br />To do this Albert Frei and Sons, Inc. will stake the 25 <br />foot setback from the property lines prior to mining in a given <br />area. For example, as mining begins on the site the 25 foot <br />setback will be staked. (The gravel depth is 15 feet for our <br />purpose in this example.) This establishes the setback line; <br />from this line a second line 30 feet away is staked for the 2:1 <br />slope (15' x 2) to establish the toe of the slope. This leaves <br />a 55 feet wide area inside the permit line where mining would be <br />done to create the slopes without backfilling. To the inside of <br />this line mining will be done on a near vertical face, but once <br />this line is reached care will be taken to mine a the 2:1 rate. <br />The three cross-sections on Figure 1 show what is explained <br />above. In Section A, a vertical face is being excavated as <br />mining approaches the permit 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 backfilling is completed lined between the <br />mined slope and the backfill material is visible. There is a <br />shallow trench along the base of the fill to collect any runoff <br />from the filled area so it does not leave the site. <br />This method of creating slopes leaves a stable slope re- <br />quiring no backfilling or other work once complete. Over the <br />years we have found that the natural angle of repose for most <br />gravel is approximately 2:1. If the gravel depth is 25 feet it <br />would be possible to mine within 50 feet of a structure with a <br />vertical face and be assured that no damage would occur to the <br />structure by a slope failure. The additional mining setback <br />leaves 25 feet of material from the fence to the digline as a <br />safety factor. This will entail more work on Frei's part and <br />leave valuable material in the mine but when done will have <br />created a more stable slope to protect off site structures.