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Section 7 <br />Groundwater Information <br />7.2.2 St. Jude Mine <br />An interpretive section of the St. Jude mine is shown in Figure 7 -7. The affected area <br />of the St. Jude mine is also located on shale of the Brushy Basin Member of the <br />Morrison Formation, which would restrict potential recharge to groundwater in this <br />area. Along the trace of the cross - section, significant direct recharge to groundwater is <br />unlikely in the central and southern portions of the section; however recharge may <br />occur to the Dakota Aquifer in the Big Gypsum Valley area north of the mine affected <br />area. <br />Extensive faulting is present in the St. Jude mine area, which may lead to local <br />compartmentalization of groundwater. The interpretive potentiometric surface in this <br />area assumes that the water table has equilibrated over geologic time. Although the <br />potentiometric surface may have equilibrated over geologic time, it is likely that the <br />confining units restrict groundwater flow between aquifers, unless the aquifers are <br />directly adjacent as a result of fault displacements. <br />7.2.3 West Sunday Mine <br />An interpretive hydrogeologic cross - section showing the West Sunday mine is <br />included as Figure 7 -8. The West Sunday Mine affected area is located east of the <br />series of faults on the periphery of the Gypsum Valley anticline, and the development <br />rock storage area overlies the Burro Canyon Formation. Where saturated, the Burro <br />Canyon Formation is part of the Dakota aquifer, and there is potential for <br />groundwater recharge to the Dakota aquifer from the mine affected area. The Salt <br />Wash and Navajo aquifers are overlain by the Brushy Basin Member shale, and <br />therefore significant recharge from the mine affected area to those aquifers is unlikely. <br />The cross - section shows the West Sunday mine decline extending to the south <br />towards Disappointment Valley. Groundwater is present in the base of the West <br />Sunday mine, which is south of the groundwater divide between Disappointment <br />Valley to the South and Big Gypsum Valley to the north. Therefore, groundwater in <br />the underground mining area would be expected to flow southward into <br />Disappointment Valley. <br />7.2.4 Topaz Mine <br />An interpretive hydrogeological cross - section showing the Topaz Mine affected area <br />is included as Figure 7 -9. The Topaz Mine affected area overlies the Salt Wash <br />Member of the Morrison Formation. Based on the interpretive hydrogeological <br />framework, this portion of the Salt Wash Member may be saturated, and therefore the <br />Salt Wash aquifer could be present in this area. The Salt Wash Member in this area is <br />truncated to the north by the Brushy Basin Member of the Morrison Formation, which <br />is a confining layer of low permeability shale. There is potential for infiltration from <br />the mine affected area to recharge the Salt Wash aquifer. Flow of this water towards <br />the north into Big Gypsum Valley would be unlikely based on the fault contact <br />juxtaposing the Salt Wash Member against the Brushy Basin Member. However, the <br />potential for westerly flow towards the Dolores River is plausible considering the <br />surficial geology. <br />C \Users\cwoodward\DesMop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />7 -4 <br />