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ARCADIS <br />addition, it is unlikely that all of the coreholes and faults /fractures can be sealed, even with a rigorous <br />grouting program. <br />Pumping of the mine pool should continue if the program is not successful at locating and plugging the <br />coreholes or grouting natural faults /fractures with potential to discharge into the alluvium, regardless of <br />whether the mine pool is successfully treated in -situ or not. Establishing and maintaining the infrastructure <br />to continue pumping the mine pool down may be needed to protect human health and the environment. <br />Recommendations: Additional details pertaining to the grouting program should be included in the <br />Reclamation Plan. <br />4.0 SURFACE SOURCE MITIGATION PLAN <br />4.1 Alluvial Fill <br />Overview: Approximately 32,000 to 54,000 cubic yards of alluvial fill that contains low -grade mineralized <br />mine material and waste rock will be removed from the valley floor. The alluvial fill is to be placed in the <br />Glory Hole that is estimated to have a volume of 56,000 cubic yards. If the Glory Hole volume is exceeded <br />because compaction will not be conducted, the excess material will be transported to the Foothills Landfill. <br />The Glory Hole is considered to be structurally stable since development in the 1970s. Flow from <br />groundwater seeps in the vicinity of the Glory Hole has been documented to be between 1 to.2 gpm or <br />less (Whetstone 2010), and therefore is considered by Cotter to have minimal potential to saturate and <br />leach elevated concentrations of uranium and other constituents. <br />Data Adequacy: Placing the alluvial fill in the Glory Hole is a reasonable option as long as contact of the <br />material with water is minimized to limit leaching and the mine pool elevation is kept well below the base <br />of the Glory Hole, which is near the Steve Level. <br />Recommendations: Place the alluvial fill in the Glory Hole as detailed in the Reclamation Plan while <br />keeping the water levels below the base of the Glory Hole. <br />4.2 Waste Rock Piles <br />Overview: No additional work is proposed for the North Waste Rock Pile, which is appropriate based on <br />the available data. Additional characterization work is proposed at the South Waste Rock Pile, including <br />trenching along the toe to determine the extent of alluvial fill that is believed to underlie the pile, installation <br />of three suction lysimeters in the waste rock to monitor infiltration through the rock pile material, and <br />installation of one alluvial well near the toe of the rock pile to assess possible impacts to groundwater from <br />the waste rock. This additional characterization was recommended during the EPP review process and is <br />necessary to determine the potential impacts to groundwater from the rock pile. <br />Page: <br />5/16 <br />