Laserfiche WebLink
ATCOLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />April 18, 2014 <br />Bradford Janes <br />Varra Companies, Inc. <br />8120 Gage Street <br />Fredrick, Colorado 80516 <br />Re: Third Review of Slope Stability Analysis, Varra Companies, Inc., Varra - Coulson <br />Resource Project, File No. M- 2013 -064 <br />The Division of Reclamation, Mining and Safety (Division) staff has reviewed the stability <br />analysis included with the Varra - Coulson Resource Project 112c adequacy letter response <br />from AWES, LLC dated March 23, 2014. <br />Using Clover Technology's Galena v6.0 slope stability software, the Division conducted <br />further analysis of the three critical cross sections and slope combinations for the Varra- <br />Coulson Resource Project. Specific comments and requirements for each of the cross <br />sections are provided below. <br />Cross Section No. 1 <br />Typical 1.25:1 Mine Slope with 10' offset, unconsolidated pit floor material and <br />topsoil stockpile loading <br />The Applicant's cross section was duplicated for verification with the addition of the topsoil <br />stockpile to represent the worst case scenario for this slope configuration. The safety factor <br />produced by Galena is significantly lower (1.01) than the safety factor produced by the <br />Applicant's model (1.267). Therefore, this slope configuration is unacceptable for the <br />perimeter of the proposed site. A copy of the Galena model is attached. The Applicant must <br />revise the typical cross section by increasing the offset distance, changing the mine face <br />slope or by another acceptable method. <br />Cross Section No. 2 <br />• Typical "Critical Slope Area" with 3:1 to 2:1 to 1.25:1 Mine Slope with 10' offset, <br />unconsolidated pit floor material and topsoil stockpile loading <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 />,oF. <br />\ * 1876 <br />