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May 2013 Groundwater POC Memorandum ♦ 9 <br />internal monitor well pairs have reported downward vertical gradients in the Quaternary <br />sediment aquifer between 0.1 and 0.67 ft /ft. <br />Analytical data for MLGW -15 will be reported after the required five quarters of monitoring. <br />However, concentrations in both wells are well below the numeric protection limits (NPLs) <br />set forth in the DRMS- approved TR -16 Groundwater Management Plan (Climax <br />Molybdenum Company, 2012). <br />3.2 POTATO GULCH <br />The north end of 1 -Dam coincides with the edge of the Ute Creek watershed hydrologic <br />divide (Figures 4 and 5). A ridge of Xg separates the area north of 1 -Dam from the Williams <br />Fork River and the shallow aquifer east of 1 -Dam. Monitor wells constructed north of 1- <br />Dam, including MLGW -2 and MLGW -10 (Potato Gulch), intermittently contain water; with <br />dry conditions reported historically. When water is observed, the levels are at high elevations <br />(greater than 200 feet) relative to the area east of 1 -Dam. Based on these geologic and <br />hydrologic observations, groundwater north of 1 -Dam is interpreted to be separate from the <br />Quaternary sediments aquifer east of 1 -Dam. <br />The geology north of 1 -Dam is characterized by surficial, thin, glacial deposits overlying Tt <br />and Xg. Tt and Xg have been demonstrated to have low permeability and are generally non - <br />water bearing. Groundwater flow is limited to the more permeable, but discontinuous, thin, <br />sand and silt beds in the Tt. Currently, groundwater is monitored in three locations north of <br />1 -Dam, MLGW -2, MLGW -3, and MLGW -10. As noted above, groundwater occurs <br />intermittently in each of the monitoring locations, with each well having been reported as <br />dry during prior monitoring events. <br />The base of the Tt was encountered at a depth of 121 feet bgs at MLGW -2. This contact <br />certainly varies in elevation, but the corresponding elevation of the contact at MLGW -2 <br />(8,801 feet amsl) is important due to its relationship with the ultimate tailings elevation in the <br />1 -Dam impoundment. As the tailings height increases above the Tt — bedrock contact <br />(8,801 feet amsl at MLGW -2), thin sand beds in the Tt could become a seepage transport <br />pathway. <br />AJAX Ltd ♦ 28828 Cedar Circle ♦ Evergreen, CO 80439 ♦ (303) 241 -2057 <br />Clear Creek Associates* 6155 E Indian School Rd. ♦ Scottsdale, AZ 85251 ♦ (480) 659 -7131 <br />