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Whirlwind Mine Groundwater Characterization Report <br /> These sources have water chemistries that fall between or outside of the Burro Canyon and <br /> Brushy Basin source water chemistry signatures. Theoretically, water chemistries shown on <br /> Figure 8 that lie in a straight line between the Burro Canyon chemistry and the Brushy Basin <br /> chemistry could result from mixing of these two end members. Sources that show a chemistry in <br /> the vicinity of a line between the Burro Canyon and Brushy Basin waters include Willow Spring, <br /> BM00-1 (Test 1), PR Spring, and Packrat Mine Pool. The latter two sources are discussed in the <br /> previous section. It is possible that mixing of Burro Canyon and Brushy Basin groundwater <br /> occurs locally through fracture flow. <br /> In the case of Willow Spring, it is conceivable that Burro Canyon aquifer water contacts the <br /> Brushy Basin upstream of the spring. The chemistry of the BM00-1 sample may also reflect a <br /> mixture of Burro Canyon and Brushy Basin as this sample was collected from an interval of <br /> borehole BM00-1 that was open (for at least some minutes)to both the Burro Canyon and <br /> underlying Brushy Basin. In addition, if the upper packer did not form a good seal, Burro Canyon <br /> water could have entered the test interval. <br /> It is equally possible that the water chemistries of these sources may simply reflect local <br /> differences in host rock composition. <br /> 6.3 Groundwater Flow <br /> Groundwater flow within separate aquifers is primarily lateral toward the northeast, in the <br /> direction of formation dip. Without a component of vertical groundwater flow and under <br /> unconfined conditions, the hydraulic gradient is expected to closely match the geologic dip of 1 <br /> to 3 degrees; resulting in an estimated maximum hydraulic gradient of 0.052 ft/ft. <br /> Observations during exploration drilling and mining have demonstrated that the aquifers of the <br /> Burro Canyon and Brushy Basin are unconfined. Drilling done by Cotter in 1996, Umetco in <br /> 2000, and EFR in 2007 showed that, when present, the Burro Canyon aquifer did not show <br /> static water levels indicating confined conditions. Similar conditions were observed in the <br /> Brushy Basin. Construction of the Whirlwind Decline allowed firsthand observations of <br /> groundwater conditions in the Brushy Basin. The formation produced groundwater from a lower <br /> sandstone unit, whereas the predominate intervals of mudstone were dry. Tunneling through the <br /> Western Water& Land, Inc. 47 <br />