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added cross sectional area for a debris flow in Sneffels Creek, which again, has never affected <br />the pile since it was built in the 1880's. <br />Waste Embankment Slope Stability Considerations <br />Based on the apparent stability of the existing unreclaimed waste rock pile slopes in the area, a <br />detailed slope stability analysis was not performed on this material. Many of these older mines <br />have slopes as steep as 1.2H:1 V compared to the 3H:1 V proposed minimum slope of the <br />Revenue and Atlas waste rock/tailings pile. The existing Revenue Pile has slopes of <br />approximately 1.1H:1.0V for over 120 years with no signs of slope instability. This is due to the <br />blasted rock having extremely angular pieces which are prone to being stable at steep angles due <br />to the inherent angle of friction of this material. The internal angle of friction of this material is <br />approximately 45 degrees. Since the waste rock has very little fine material, the mine water <br />seepage through it will have no effect on the stability of the pile since there is no cohesion in this <br />waste rock, only internal angle of friction. Mine discharge water will no longer pass through the <br />existing waste rock as it does now with the Revenue Seep. Exhibit U presents a slope stability <br />analysis using commonly accepted circular failure equations and material parameters for both the <br />Revenue Pile and the Atlas Pile. The analysis indicates that the waste embankments have a <br />calculated safety factor above 1.3, using conservative strength parameters, which constitutes an <br />adequate design. <br />Map C -3 shows the avalanche path that covers a large portion of the Revenue Pile. There is no <br />path in the Atlas Pile area and no avalanche has ever been seen there in 120 years. The Revenue <br />pile area sees an avalanche almost every year. A plan has been incorporated to safely trigger <br />these avalanches using an experienced contractor, as explained in Exhibit T. GLA firmly <br />believes that the avalanches will not affect the new Revenue Pile stability for 3 main reasons: <br />1) No avalanche in the past has ever caused a stability problem with the existing waste rock, <br />even though the north slope of the Revenue Pond is immediately in the path of the avalanche and <br />2) The new pile will fill in this pond, providing no resistive slope for the avalanche to come up <br />against, thus increasing the stability and 3) the permanent slope of the finished pile is tilted to the <br />Revenue Mine August 2012 D -17 <br />