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L <br />GLISTAVSON ASSOCIATES <br />GEOLOGISTS ENGINEERS APPRAISERS <br />May 11, 2006 <br />Mr. Tom Schreiner <br />Environmental Protection Specialist <br />Colorado Division of Minerals and Geology <br />1313 Sherman Street, Room 215 <br />Denver. Colorado 80203 <br />Re: Regular 112 Permit Application, North Bank Resources <br />Responses to Geotechnical Review Questions <br />Deaz Mr. Schreiner: <br />You have requested clarification regarding the stability of slopes related to the proposed North <br />Bank Resources aggregate operation neaz Rifle, Colorado. Specifically, you are requesting <br />assurance that static and seismic loading will result in slope safety factors exceeding 1.5 and 1.3, <br />respectively, for the following situations at the proposed operation: <br />1. Ten-foot offset from fence lines <br />2. Twenty-five-foot offset from pipelines <br />3. Otte-hundred-foot offset from gas wells <br />4. Fifty-foot offset from the McBride house <br />The March 17, 2005, slope stability analyses reported by Greystone Environmental Consultants <br />(permit application Appendix A) confirms that the design slope safety factors for toe circle, slope <br />circle, and base circle failure exceed 1.5 and 1.3 for static and seismic loading, respectively, at <br />reasonable ranges of material properties and bench heights. Therefore, each of the conditions <br />noted in items 1-3 should be stable, and the item 4 condition should not reduce the stability of <br />the existing slope below the house. <br />I hope these are satisfactory responses to your concerns. Should you have questions or wish <br />further discussion, please call. <br />Sincerely, <br />K. M. Kc <br />Principal <br />5757 Central Ave Suite D Boulder, CO 8030t USA +1 (303) 443-2209 FAX+t (303) 443.3156 <br />http:7lvnnw.uuttavson.com gustavs~¢ustvwn: a4.~ <br />