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STATE OF COLORADO <br />DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-8106 <br />COLORADO <br />D I V I S I ON OF <br />RECLAMATION <br />MINING <br />- St- <br />SAFETY <br />MEMORANDUM John W. Hickenlooper <br />Governor <br />Mike King <br />Executive Director <br />To: Michael Cunningham, Environmental Protection Specialist Loretta Pineda <br />Director <br />From: Tim Cazier, P.E., Environmental Protection Specialist] <br />Date: June 8, 2011 <br />Re: Slope Stability Analyses Review for Western Sugar Reclamation Land <br />Development Project, Permit No. M-2010-049 <br />The Division of Reclamation, Mining and Safety engineering staff (DRMS) have reviewed the <br />Slope Stability analyses dated the February 28, 2011 for the Varra Gravel Operation - Great <br />Western Sugar, Greeley Colorado. <br />The review consisted of comparing the application content with specific requirements of Rule <br />6.5 of the Minerals Rules and Regulations of the Colorado Mined Land Reclamation Board for <br />the Extraction of Construction Materials. Any inadequacies are identified below along with <br />suggested actions to correct them. <br />1. Page 1, Background Information: The last line of the second paragraph states "Any <br />extraction beneath 45 feet will be wet mining." The second bullet on page 2 states "The <br />maximum bank height is 45 feet." Please clarify whether or not mining is proposed below a <br />depth of 45 feet. <br />2. Page 2, Overview of Stability Analyses: <br />a. Please provide some basis for the stated assumption for a cohesion value of 731 <br />psf for the underlying Pierre Shale. <br />b. The stability analyses in Attachment A show four or five layers of material <br />overlying the Pierre Shale. The fifth bullet on page 2 suggests a range of internal <br />friction angles (26 to 45 degrees) for these layers. Please provide specific values <br />assumed for each layer in the analyses and a basis for the assumed value of each. <br />In addition, please provide unit weights assumed for each layer in the analyses <br />and a basis for the assumed value of each. <br />c. The first paragraph under the bulleted items states "Simulations using Spencer, <br />Modified Bishop and Modified Janbu methods were run ... ". Attachment A <br />Office of Office of <br />Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines