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Hydrogeological Evaluation of Sunday Mines Group <br />Geologic and Hydrologic Conditions <br />steep northerly dipping rock units present in the eastern portion of the section. This <br />structural orientation exhibits the collapse of clastic sedimentary units into the central <br />portion of Big Gypsum Valley described in Section 2.1.3. <br />2.2.2 St. Jude Mine <br />The local geology in the area of the St. Jude mine affected area is shown in Figure 2-3. <br />The affected area of the mine also overlies the Brushy Basin Member of the Morrison <br />Formation. Three faults are present on the section with downward displacement of <br />rocks towards Big Gypsum Valley. These faults form several fault bound blocks of <br />sedimentary rocks in the general vicinity of the mine affected area. Folding, faulting <br />and collapse of rock units into the central portion of the valley is evident, which is <br />also associated with collapse of clastic sedimentary rocks into the central portion of <br />Big Gypsum Valley. <br />2.2.3 West Sunday Mine <br />The local geological framework of the West Sunday Mine affected area is shown on <br />Figure 2-4. In general, this geology of the area is similar to that previously described <br />at the St. Jude, Carnation, and Sunday mines. However, the affected area of the mine <br />is located in a different location in relation to the faults bounding the valley and the <br />displaced geologic formations. The affected area of the West Sunday mine lies on the <br />Brushy Basin Member of the Morrison Formation and the Burro Canyon Formation. <br />Several faults are present in the general vicinity of the mine affected area; however, <br />the faults are located upslope from the affected area. <br />2.2.4 Topaz Mine <br />The Topaz Mine is located approximately 1 mile west of the other Sunday Group <br />mines, and the local geological framework is somewhat different. The affected area of <br />the Topaz mine is shown on Figure 2-5. This affected area directly overlies the Salt <br />Wash Member of the Morrison Formation, which is the unit that hosts uranium- <br />vanadium mineralization at the mine. The Salt Wash Member consists of sandstone <br />with interbedded red shale and a few local beds of limestone. A fault is present in <br />proximity to the Topaz Mine affected area, which displaces rock units on the north <br />side downward as observed previously at the other Sunday Group mines. This fault <br />juxtaposes the Brushy Basin shale on the north side of the fault against the Salt Wash <br />member on the south side of the fault. <br />Additional information regarding the geological framework in the area of the Topaz <br />mine affected area is shown on the geologic map (Figure 2-1). The relative density of <br />faults in the area west of the Topaz Mine is higher than areas adjacent to the other <br />Sunday Group mines. This may be related to increased structural complexity <br />associated with the intersection of the Big Gypsum Valley anticline with geologic <br />structures associated with the Dolores River. Although the density of faults is higher, <br />the faults show the same general pattern of displacing rock units on the north side of <br />the fault downward towards Big Gypsum Valley. The surface geology shown in <br />cm 2-6 <br />TA64986-Denison Mines\Task Older 3 - DMO Sampling and Analysis Plan\Task 3.14 - Hydrogeology Reportwinal sunday hydro reporNeATINAL Sunday Hydrogeology Report.doc