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Hydrogeological Evaluation of Sunday Mines Group <br />Geologic and Hydrologic Conditions <br />permeability values provided by Jobim (1962). These values were described <br />previously in Section 2.3.3. <br />Exhibit 2-4 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 />z'vh;l,;I 7_d Fcf4mnI0II lirrvnr OrOU"dMatPr velorihl <br />Mine Estimated Estimated Estimated Estimated <br /> Hydraulic Porosity Hydraulic Average <br /> Gradient Conductivity Linear <br /> (cm/sec) Groundwater <br /> Velocity <br /> feet/ ear <br />Topaz 0.004 0.11 1.1 x 104 4.1 <br />Topaz 0.004 0.14 1.1 x 104 3.3 <br />West Sunda 0.006 0.11 1.1 x 104 6.2 <br />West Sunda 0.006 0.14 1.1 x 104 4.9 <br />• Based on the evaluation presented above, the rate of groundwater flow is estimated to <br />range from approximately 3.3 to 6.2 feet per year. This suggests that, if pathways are <br />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 />2.4.4 Naturally Occurring Geochemical Conditions <br />There are two major categories of naturally occurring geochemical conditions that are <br />important in relation to the Sunday Mines Group: <br />1. Naturally occurring high salinity that results from outcrops of the Paradox <br />Member of the Hermosa Formation; and <br />2. Natural enrichments of uranium, vanadium, and other metals, which are <br />associated with the uranium-vanadium ore deposits in the Salt Wash Member <br />of the Morrison Formation. <br />As described previously, the Big Gypsum Valley anticline is formed from a collapsed <br />salt intrusion. The Paradox Member of the Hermosa Formation is dominantly <br />composed of rock salt (halite [NaCI] and sylvite [KCI]) as well as gypsum <br />(Ca(SO4) •2H20). This unit crops out in several areas of lower Big Gypsum Valley, and <br />cm 2-19 <br />T:\64986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.14 - Hydrogeology Reporttlinal sunday hydro reportUextTINAL Sunday Hydrogeology Report.doc