Laserfiche WebLink
• <br />• <br />• <br />C1Documents an <br />Section 7 <br />Groundwater Information <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. The <br />interpreted depth to groundwater is based on observations of groundwater occurring <br />within the Sunday, West Sunday and Topaz mine at a depth of approximately 585 feet <br />(ft), and an assumption that the Dolores River is the local base point for the <br />hydrogeologic system. <br />7.2.1 Sunday and Carnation Mines <br />An interpretive hydrogeologic framework for the Sunday and Carnation mines is <br />presented in Figure 7 -6. 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 />layers of the Brushy Basin Member. Recharge to these aquifers is likely by lateral flow <br />through the aquifer from adjacent areas where the sandstones are exposed at the <br />surface. <br />An area of submerged mine workings is shown on the south end of the section, south <br />of the interpreted groundwater divide between Disappointment Valley to the South <br />and Big Gypsum Valley to the north. This portion of the mine was excavated during a <br />prior phase of mine development, and these workings are currently inaccessible. <br />Groundwater in this area likely flows towards the south into Disappointment Valley. <br />Communication of groundwater between the Salt Wash aquifer and the underlying <br />Navajo aquifer is unlikely, because of the presence of the confining layer formed by <br />the Summerville Formation shale. <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 />Settings \cwoodward.DMC\Desktop \Environmental Protection Plan Sunday Mines Revised November 2011 reel (2) 11 10 tt.docz <br />7 -4 <br />