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COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />December 22, 2015 <br />Interoffice Memo <br />Bowie No. 2 (Permit No. C-1996-083) <br />Technical Revision No. 105 (TR -105) <br />Jason, <br />I have reviewed Bowie No. 2 Technical Revision No. 105 and have the following comments: <br />Bowie has included piezometers and identified them on Figure 2 — Coal Mine Waste Disposal <br />Area #3 Full Build Out. I have no issues and all items have been addressed regarding my initial <br />comments. <br />As noted in my first interoffice memo dated November 12, 2015, stability analysis of gob pile #3 <br />was performed critical sections of the pile. The design of the expansion section appears to remain <br />consistent with the current construction and design of gob pile #3 with critical sections remaining <br />unchanged. Thus, HBET's stability analysis is representative of the expanded section so an <br />additional stability analysis isn't necessary. Bowie has provided a cross sectional view of the <br />expanded section of Gob Pile #3 and I have performed a "stability check". I analyzed the <br />expanded section in two scenarios; with and without groundwater present within the pile. My <br />stability analysis resulted in a factor of safety of 1.69 (without groundwater) and 1.59 (with <br />groundwater). Both results are greater than what is required by the Rules and general engineering <br />practices. Attached are the results of my stability analysis. <br />I have no further issues and this concludes my review of Bowie No. 2 TR -105. If you have <br />questions or need additional information, please contact me. <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us <br />John W. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />