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Hydrogeological Evaluation of Sunday Mines Group <br />Conclusions <br />Section 3 <br />Conclusions <br />The hydrogeologic framework of the Sunday Mines Group is controlled by geologic <br />and climatic factors. The Sunday Mines Group is located in an and area of the Dolores <br />River Basin where evaporation greatly exceeds precipitation. The climate supports the <br />and landscape and constrains both surface water flow and recharge to groundwater. <br />The only perennial surface water body in the area is the Dolores River, which receives <br />the majority of its flow from mountainous areas surrounding the Dolores River Basin. <br />Other surface water in the Sunday Mines Group area is intermittent or ephemeral <br />with surface flows occurring only seasonally or in response to major precipitation <br />events. <br />The hydrogeologic framework is relatively complex as a result of the occurrence of a <br />sequence of sandstone aquifers separated by low-permeability confining units, which <br />are displaced by folds and faults associated with the Gypsum Valley anticline and <br />Disappointment Valley syncline. The structural displacements result in formation of <br />fault-bound blocks containing the various hydrogeologic units. Groundwater is <br />commonly unconfined, but confined conditions are present in Disappointment Valley. <br />Groundwater flow is generally towards the Dolores River, but the flow directions are <br />perturbed locally by underground mining, topography and structural displacements. <br />I The rate of groundwater flow is relatively slow with estimated linear groundwater <br />velocities of between 3 and 6 feet per year. <br />Uncommon natural geochemical conditions are present in the area including high <br />salinity that results from exposure of the Paradox Member of the Hermosa Formation <br />in Big Gypsum Valley and natural enrichments of uranium, vanadium and other <br />associated metals. Exposures of the Paradox Member in Big Gypsum Valley have led <br />to chemical erosion of rock salt, and development of an ecosystem in lower Big <br />Gypsum Valley that is tolerant of natural high salinity conditions. Natural <br />enrichments of uranium, vanadium and other associated metals also affect the <br />geochemistry of the area and the quality of groundwater in close proximity to the <br />uranium-vanadium ore deposits. <br /> <br />cm 3-1 <br />T:\64986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.14 - Hydrogeology Report final sunday hydro report\te d\FINAL Sunday Hydrogeology Report.doc