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Hydrogeological Evaluation of Van 4 Mine <br />Conclusions <br />• <br />Section 3 <br />Conclusions <br />The Van 4 Mine is located on Monogram Mesa, on the south side of Paradox Valley. <br />The mine is located in an and area where evaporation greatly exceeds precipitation. <br />The hydrogeologic framework of the Van 4 mine area consists of the three potential <br />aquifers separated by low-permeability confining layers. In an orientation extending <br />from the surface to depth, the potential aquifers consist of: <br />a The Dakota Aquifer; <br />¦ The Salt Wash Aquifer; and <br />¦ The Navajo Aquifer. <br />An aquifer only includes the saturated portion of a respective rock unit. Available <br />information indicates that seeps are present at the base of the Dakota aquifer, <br />suggesting that saturated conditions occur at least locally within the Dakota aquifer. <br />However, the and environment limits recharge to groundwater, and the quantity of <br />groundwater present at the base of the Dakota aquifer appears to be limited. The <br />Brushy Basin Member of the Morrison Formation underlies the Dakota and forms a <br />• confining layer that restricts downward movement of groundwater into the <br />underlying Salt Wash aquifer. Alluvial aquifers are not expected to be present in the <br />Van 4 mine area, because the unconsolidated alluvial and colluvial deposits on <br />Monogram Mesa are unlikely to be saturated. <br />Existing underground mine workings are located in the upper portion of the Salt <br />Wash Member. Where saturated, this member hosts the Salt Wash Aquifer. Available <br />information indicates that the Van 4 Mine underground mine workings are not <br />saturated. However, the presence of intermittent flow at Fawn Springs indicates that <br />local saturated conditions are present in the Salt Wash Aquifer downgradient of the <br />mine, at least during some portions of the year. Recharge to the Salt Wash aquifer is <br />very limited in the Van 4 Mine area because overlying Brushy Basin confining layer <br />restricts vertical movement of groundwater into the aquifer. A fault zone is present <br />upgradient of the mine area, which may contribute somewhat to infiltration into the <br />Salt Wash Aquifer. Additional recharge areas for the Salt Wash aquifer are present <br />downgradient of the mine. Recharge in these areas likely contributes to the presence <br />of local saturated conditions in the area of Fawn Springs. <br />It is unknown if the Navajo aquifer is saturated in the Van 4 area. However, this <br />aquifer is separated from both the surface and underground portions of the Van 4 <br />mine by a confining layer. Therefore, it is unlikely that mineral development would <br />affect the Navajo Aquifer. <br />0 cm <br />3-1 <br />draft final van 4 hydrogeology report.doc