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To further reduce the risk of impacts to the jurisdictional wetlands, signs will be placed along the <br /> wetland boundary. It is understood that Ouray Silver Mines will not be allowed to disturb the <br /> wetlands and if any wetlands are to be disturbed, an approved nationwide or individual permit <br /> must be supplied to the DRMS. The Atlas TSF along with a sediment control pond is located on <br /> the moderately flat area west of the main Revenue portal area. The Atlas TSF was graded to <br /> provide an area for the placement of tailings and related sediment pond. Preliminary as built <br /> drawings for the Atlas TSF are included in Attachment 5. The maximum height of the Atlas TSF <br /> will be 60 feet. Ten-foot benches will be placed every 30 feet as described in Section 7 of the <br /> 2015 Tailings and Waste management Plan. <br /> Like the Revenue TSF, the Galena Slope Stability Analysis Stem was used to calculate factors of <br /> safety for different ratios of waste rock being mixed into the tailings. The Galena software <br /> utilizes Bishop's method of slope stability analysis. Bishop's method only considers moment <br /> equilibrium and is suited to stability problems where a circular failure surface is likely, such as a <br /> tailings pile. The different mixtures of tailings and waste rock result in varying cohesion factors. <br /> Benches were not included in this model because the benches are not placed for slope stability — <br /> they are to control stormwater runoff on the piles. Five scenarios were created for the Atlas TSF <br /> which resulted in Factors of Safety between 2.87 and 4.08. Factors of Safety for all scenarios are <br /> well above the minimum 1.3 required by the Division. <br /> 4.3 Waste Rock Storage <br /> Waste rock brought to the surface to be used for embankment, TSF construction or to be crushed <br /> as road base will be managed using the following best management practices (BMPs). <br /> 1) As required by TR-09,waste rock crushed for use off-site must be tested using the <br /> Synthetic Precipitation Leachate Procedure (SPLP)to ensure the material is suitable for <br /> use as a road base and will not cause environmental impacts. In the SPLP test,the waste <br /> rock is ground to a minute size (i.e., smaller than 9.5 millimeters)prior to leaching with a <br /> pH 5 solution,while the actual waste rock embankment site will have larger sized rocks <br /> up to 1.5 inches in diameter,that will not leach as readily. <br /> 2) Undisturbed runoff from the south hillside is diverted away from the waste rock <br /> embankment,using a diversion ditch designed for the 10-year, 24-hour storm event. <br /> 3) The waste rock embankment will be covered with a minimum of six inches of topsoil and <br /> planted with a stable mix of vegetation well suited to this location and approved by <br /> DRMS. The vegetation will use most of the direct precipitation and surface water runoff <br /> that occurs on the reclaimed embankment. This will minimize the amount of water that <br /> can percolate into the reclaimed waste material. Details of this plan are shown in Exhibit <br /> E. <br /> 4) The gradual slopes and revegetated surface of the waste rock embankment will minimize <br /> erosion of topsoil and prevent exposure of the underlying waste rock. <br /> 5) Waste rock cannot make up more than 15% of the new material to be placed in the <br /> permanent TSFs,to prevent void spaces which may reduce compaction and provide <br /> conduits for water flow. <br /> Revenue Mine <br /> Amendment 02 D-20 <br /> Updated August 2022 <br />