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Mine <br />Estimated <br />Hydraulic <br />Gradient <br />Estimated <br />Porosity <br />Estimated <br />Hydraulic <br />Conductivity <br />(cm /sec) <br />Estimated <br />Average Linear <br />Groundwater <br />Velocity <br />(feet/year) <br />Topaz <br />0.004 <br />0.11 <br />1.1 x 10 -4 <br />4.1 <br />Topaz <br />0.004 <br />0.14 <br />1.1 x 10 -4 <br />3.3 <br />West Sunday <br />0.006 <br />0.11 <br />1.1 x 10 -4 <br />6.2 <br />West Sunday <br />0.006 <br />0.14 <br />1.1 x 10 -4 <br />4.9 <br />Mine <br />Observed <br />Groundwater <br />Elevation <br />(feet) <br />Elevation of <br />Potential <br />Discharge Point <br />(feet) <br />Distance from <br />Mine to Potential <br />Discharge Point <br />(feet) <br />Estimated <br />Hydraulic <br />Gradient <br />(feet) <br />Carnation/West <br />Sunday <br />5,490 <br />5,360 <br />20,431 <br />0.006 <br />Topaz <br />5,403 <br />5,360 <br />10,582 <br />0.004 <br />Exhibit 7 -2. Estimated Hydraulic Gradient <br />The porosity of the sandstone is unknown; however, Freeze and Cherry (1979) <br />describe an empirical relationship developed by Chilinger (1963), which allows <br />estimation of sandstone porosity based on the textural classification and the intrinsic <br />permeability. Craig et al. (1955) describe the texture of Salt Wash Member sandstone <br />as ranging from fine grained to medium grained, which is supported by visual <br />observations collected during the course of this investigation. Based on the empirical <br />relationship developed by Chilinger (1963) and the intrinsic permeability data <br />provided by Jobim (1962), the porosity of the Salt Wash member sandstones is <br />estimated to range from approximately 11 to 14 percent. In this estimation of average <br />linear groundwater velocity, this estimated porosity is assumed to be equivalent to <br />the estimated effective porosity of the Salt Wash member sandstones. <br />Groundwater observed in the West Sunday and Topaz Mines occurs within the Salt <br />Wash member of the Morrison Formation. A hydraulic conductivity of 1.1 x 10 -4 <br />centimeters per second (cm /sec.) is estimated for this unit based on intrinsic <br />permeability values provided by Jobim (1962). <br />Exhibit 7 -3 presents a range of estimated linear groundwater velocity for the Salt <br />Wash Member of the Morrison Formation in the vicinity of the mines based on the <br />hydraulic conductivity, effective porosity and hydraulic gradient information <br />described above. <br />Exhibit 7 -3. Estimated Linear Groundwater Velocit <br />C \Users1cwoodward1Desktop \Sundays 1FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />Section 7 <br />Groundwater Information <br />Based on the evaluation presented above, the rate of groundwater flow is estimated <br />to range from approximately 3.3 to 6.2 feet per year. This suggests that, if pathways <br />are present for groundwater to travel towards the Dolores River, the travel time for <br />groundwater in the vicinity of the mine affected areas to reach the Dolores River may <br />be on the order of 2600 to 3300 years. However, the complex structural displacement <br />of the Salt Wash aquifer and other hydrogeologic units likely increases the complexity <br />of groundwater pathways, which may affect the travel time towards the Dolores <br />River. <br />7 -8 <br />