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Hydrogeological Evaluation of Sunday Mines Group <br />Geologic and Hydrologic Conditions <br />It is likely that groundwater flows laterally within the sandstone aquifers in a <br />direction that is generally towards the Dolores River. However, local flow directions <br />in direct vicinity of the mines are likely modified by the complex structural geology of <br />area, and groundwater in the vicinity of the mines may take a complex route in the <br />process of moving generally towards the Dolores River. A hydrogeologic divide is <br />interpreted to be present coincident with the topographic divide between Big <br />Gypsum and Disappointment Valleys with groundwater north of the divide staying <br />within the Big Gypsum Creek watershed and groundwater south of the divide <br />staying within the Disappointment Creek watershed. <br />The Salt Wash aquifer and the Dakota Aquifer crop out adjacent to the Dolores River <br />in the Disappointment Creek watershed, and the Saltwash aquifer crops out adjacent <br />to the river in the Big Gypsum Creek watershed. These are likely areas of <br />groundwater discharge to the river. Groundwater discharge from the Dakota aquifer <br />is also reported from several artesian wells in the Disappointment Creek watershed <br />(Weir et al. 1983). <br />Groundwater in the vicinity of the mine affected areas is generally unconfined. <br />Confined conditions are reported for aquifers in Disappointment Valley, and it is <br />likely that groundwater conditions change from unconfined to confined as the depth <br />of the aquifers increase along the northern limb of the Disappointment Valley <br />syncline. <br />The following sections provide additional detail regarding the local groundwater <br />framework in direct vicinity of the various mines within the Sunday Group. These <br />sections have been developed based on the geologic sections presented in Section 2.2, <br />the hydrogeological units defined in Exhibit 2-2, observations regarding presence of <br />groundwater within existing underground workings, and information presented by <br />Weir et al (1983). The interpreted depth to groundwater is based on observations of <br />groundwater occurring within the Sunday, West Sunday and Topaz mine at a depth <br />of approximately 585 feet, and an assumption that the Dolores River is the local base <br />point for the Hydrogeologic system. <br />2.4.1.1 Sunday and Carnation Mines <br />An interpretive hydrogeologic framework for the Sunday and Carnation mines is <br />presented in Figure 2-10. This section shows the approximate location of the affected <br />area of the mines, the underground workings, the major hydrogeologic units, major <br />faults and the interpreted potentiometric surface. <br />The affected area of the mines lies above the shale confining layer of the Brushy Basin <br />Member of the Morrison Formation. The potential for significant infiltration through <br />this layer and recharge to groundwater is low in this area. Groundwater is interpreted <br />to be present within the Salt Wash and Navajo aquifers at depth beneath the confining <br />to layers of the Brushy Basin Member. Recharge to these aquifers is likely by lateral flow <br />cm 2-13 <br />TA64988-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.14 - Hydrogeology ReportVlnal sunday hydro report\textTINAL Sunday Hydrogeology Repon.doc