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GEOTECHNICAL STABILITY EXHIBIT <br />There are no buildings or any structures outside the permit area which could be affected by the <br />excavation. A minimum 30 foot buffer will be maintained from the permit boundary line to all <br />new excavations. There will be no excavation within 30 feet of the property line. <br />1. Slope Stability <br />The Ralston Quarry is entirely contained within a basalt extrusion adjacent to Pierre shale that <br />has been uplifted. Basalt, like what is found in this quarry, is highly competent material that <br />facilitates mining to very steep slopes. The south, north, and east slopes of the quarry are entirely <br />contained within the basalt, and are therefore limited in their slopes by the basalt's geotechnical <br />properties and local jointing. On the west slope, the basalt -shale contact dictates the limits of <br />excavation and permanent slopes. <br />Brierley and Associates of Golden, CO performed a site specific analysis of the slope stability at <br />Ralston Quarry. Their report is attached as Appendix 2. According to their analysis of possible <br />wedge failures in the quarry, the following worst case scenarios were determined that will be <br />used to limit the final excavation highwalls of the quarry: <br />1. West slope (east dipping) <br />a. Overall all slope limit = 73 °. Measured from the top bench crest to the bottom <br />bench toe. <br />b. Individual bench limit = 90 °. Measured from a single bench crest to that bench's <br />toe. <br />c. Minimum bench width = 14' <br />d. Maximum bench height = 80' <br />2. East slope (west dipping) <br />a. Overall slope limit = 90 °. Measured as a single slope from the top of the <br />excavation to the bottom. <br />b. Maximum bench height = 200' <br />3. North slope (south dipping) <br />Ralston Quarry, February 2015 U -1 <br />