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embankment. This will minimize the amount of water that can percolate into the reclaimed waste <br />material. Details of this plan are shown in Exhibit 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) The permeability of the waste rock (and susceptibility to leaching) will also be reduced by the <br />compaction that is specified (94% of maximum dry density) of the waste pile. The material will <br />be compacted in thin lifts in order to achieve this compaction. This compaction also serves to <br />greatly improve the slope stability of the permanent pile. The existing base area of the Revenue <br />pile from the mine discharge pipe to the north will not be altered, except for the excavation along <br />Sneffels Creek for the bench, collection ditch and Sediment Pond #2. The cross section showing <br />this is included on Map C -6. Tailings will only be placed above the existing waste rock and will <br />be compacted to the required 94% compaction. The waste rock will be left in its current <br />condition to allow infiltration of the mine water flow into the groundwater. <br />6) A water monitoring well is located at the downstream edge (north of the north toe) of each <br />pile to monitor the water quality of any water that may emanate from the piles. These samples <br />will be tested for the full ground water suite on a quarterly basis. <br />7) Additional SPLP tests will be conducted on the tailings once a quarter for the life of the mine <br />and provided to the Division in Quarterly Groundwater Reports. <br />8) Waste rock cannot make up more than 20% of the new material to be placed in the permanent <br />piles, in order to prevent void spaces which may reduce compaction and provide conduits for <br />water flow. The existing waste at the Revenue Pile is entirely waste rock and will have <br />permeability, which is where the mine water discharge will be located. Tailings from the mill <br />will be placed above this waste rock, as shown on the cross section of Map C -6. <br />9) The existing waste rock will be pulled back from the base of Sneffels Creek to leave a <br />horizontal bench for access to the toe of the new Revenue Pile. This bench will be vegetated and <br />will contain the collection ditch to Sediment Pond #2. This bench also allows increased flow <br />cross section for Sneffels Creek during a very high peak flow event before it could erode the toe <br />of the pile, although no evidence of this erosion has taken place in 120 years. It also provides <br />Revenue Mine August 2012 D -16 <br />