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Whirlwind Mine Groundwater Characterization Report <br /> Salt Wash Top Rim sandstone was common at a number of historic mines, and the unit did not <br /> produce substantial quantities of groundwater. Drill hole intercepts that conveyed seepage from <br /> the overlying aquifer zones was a common component of mine inflows. <br /> Based on the above observations, evidence of broad downward vertical seepage from the Burro <br /> Canyon or the Brushy Basin to underlying strata is lacking. The lack of a confined aquifer in the <br /> Salt Wash would further indicate that upward or downward leakage from the Top Rim is not <br /> likely. The underlying Morrison Tidwell Member and the Summerville Formation, both consisting <br /> of very fine-grained sediments, are likely of low permeability and may restrict any downward <br /> seepage of groundwater that may occur in the Salt Wash. However, it was suggested that it is <br /> possible that some water source chemistry may represent mixing of Burro Canyon groundwater. <br /> with Brushy Basin groundwater. Such mixing would require a component of vertical flow in these <br /> formations. Of the three sources where mixing may be occurring, two of them are springs, <br /> Willow Spring and PR Spring. Like many springs, their existence is due to some preferential <br /> flow path such as fractures in the hydrostratigraphy and such fractures may convey <br /> groundwater from upper aquifers to lower ones. It is also known that vertical migration of <br /> groundwater is occurring through drill holes, but this mechanism is not necessarily playing a role <br /> in spring chemistry, except possibly in the Packrat Mine and the Rajah 49 Mine. <br /> 7.0 HYDROGEOLOGIC CONCEPTUAL MODEL <br /> The purpose of a hydrogeologic conceptual model is to provide a working concept of the <br /> hydrologic systems and interrelationships of surface water and groundwater sources in the <br /> vicinity of the project area so that groundwater behavior and potential contaminant fate and <br /> transport can be reasonably estimated as a result of past and proposed mining operations. <br /> This report documents key historical hydrological information and data that is associated with <br /> the Whirlwind Mine site and vicinity mines, as well as surface hydrological observations. A <br /> hydrogeologic conceptual model has been formulated on the basis of factual information <br /> gathered from previous exploration and mining operations and mine permitting investigations. <br /> Surface water in the study area is sparse as the main drainages in the near and downgradient <br /> of the mine area are ephemeral to intermittent in nature. No perennial surface water features <br /> exist adjacent to the Whirlwind Mine area; therefore, groundwater occurrence in the observed <br /> aquifers originates from infiltration of meteoric water(precipitation). However, groundwater that <br /> Western Water& Land, Inc. 48 <br />