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Section 7 Groundwater Information within the Big Gypsum Creek watershed and groundwater south of the divide staying within the Disappointment Creek watershed. The Salt Wash aquifer and the Dakota Aquifer crop out adjacent to the Dolores River in the Disappointment Creek watershed, and the Salt Wash aquifer crops out adjacent to the river in the Big Gypsum Creek watershed. These are likely areas of groundwater discharge to the river. Groundwater discharge from the Dakota aquifer is also reported from several artesian wells in the Disappointment Creek watershed (Weir et al. 1983). Groundwater in the vicinity of the mine affected areas is generally unconfined. Confined conditions are reported for aquifers in Disappointment Valley, and it is likely that groundwater conditions change from unconfined to confined as the depth of the aquifers increase along the northern limb of the Disappointment Valley syncline. The following sections provide additional detail regarding the local groundwater framework in direct vicinity of the various mines within the Sunday Group. The interpreted depth to groundwater is based on observations of groundwater occurring within the Sunday, West Sunday and Topaz mine at a depth of approximately 585 feet (ft), and an assumption that the Dolores River is the local base point for the hydrogeologic system. 7.2.1 Sunday and Carnation Mines An interpretive hydrogeologic framework for the Sunday and Carnation mines is presented in Figure 7 -6. This section shows the approximate location of the affected area of the mines, the underground workings, the major hydrogeologic units, major faults and the interpreted potentiometric surface. The affected area of the mines lies above the shale confining layer of the Brushy Basin Member of the Morrison Formation. The potential for significant infiltration through this layer and recharge to groundwater is low in this area. Groundwater is interpreted to be present within the Salt Wash and Navajo aquifers at depth beneath the confining layers of the Brushy Basin Member. Recharge to these aquifers is likely by lateral flow through the aquifer from adjacent areas where the sandstones are exposed at the surface. An area of submerged mine workings is shown on the south end of the section, south of the interpreted groundwater divide between Disappointment Valley to the South and Big Gypsum Valley to the north. This portion of the mine was excavated during a prior phase of mine development, and these workings are currently inaccessible. Groundwater in this area likely flows towards the south into Disappointment Valley. Communication of groundwater between the Salt Wash aquifer and the underlying Navajo aquifer is unlikely, because of the presence of the confining layer formed by the Summerville Formation shale. C \ Users \cwoodward\Des1aop \SundayslFINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx 7 -3